CREATIVE BIOMOLECULES INC
8-K, 2000-02-18
BIOLOGICAL PRODUCTS, (NO DIAGNOSTIC SUBSTANCES)
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<PAGE>   1

                             WASHINGTON, D.C. 20549

                                    FORM 8-K

                                 CURRENT REPORT

                         PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934


       Date of Report (Date of earliest event reported): FEBRUARY 14, 2000
       -------------------------------------------------------------------

                           CREATIVE BIOMOLECULES, INC.
             ------------------------------------------------------
             (Exact name of registrant as specified in its charter)


           DELAWARE                 0-19910                    94-2786743
       -----------------------------------------------------------------------
       (State or other            (Commission                (IRS Employer
       jurisdiction of            File Number)             Identification No.)
                                 incorporation)


                 45 SOUTH STREET, HOPKINTON, MASSACHUSETTS 01748
               ---------------------------------------------------
               (Address of principal executive offices) (Zip Code)


       Registrant's telephone number, including area code: (508) 782-1100
       ------------------------------------------------------------------


<PAGE>   2




                              ITEM 5. OTHER EVENTS.

On February 14, 2000, the Registrant entered into an Agreement and Plan of
Merger with Ontogeny, Inc., and Reprogenesis, Inc., pursuant to which each
company shall be merged with and into a new public company known as Curis, Inc.
Under the terms of the merger, which is subject to shareholder and regulatory
approval, the Registrant's shareholders will receive three shares of Curis
common stock for every ten shares of Creative BioMolecules. Following
completion of the transaction, the Registrant's shareholders will hold
approximately 43%, Ontogeny's shareholders will hold approximately 38% and
Reprogenesis' shareholders will hold approximately 19% of Curis. The merger is
expected to close in June 2000.


ITEM 7.  FINANCIAL STATEMENTS AND EXHIBITS.

(c)  Exhibits.

2.1 The Registrant's Agreement and Plan of Merger dated February 14, 2000.






                                        2


<PAGE>   3




                                   SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                    Creative Biomolecules, Inc.
                                    ----------------------------------
                                    (Registrant)

Date: February 17, 2000             /s/ Cheryl K. Lawton
                                    ----------------------------------
                                    Cheryl K. Lawton
                                    General Counsel and Vice President,
                                    Administration and Secretary


<PAGE>   4



                                  EXHIBIT INDEX

Exhibit
- -------

2.1        The Registrant's Agreement and Plan of Merger dated February 14, 2000



<PAGE>   1
                                                                     Exhibit 2.1


================================================================================



                          AGREEMENT AND PLAN OF MERGER

                                      AMONG

                           CREATIVE BIOMOLECULES, INC.

                                 ONTOGENY, INC.

                               REPROGENESIS, INC.

                                       AND

                                   CURIS, INC.

                          DATED AS OF FEBRUARY 14, 2000



================================================================================


<PAGE>   2


                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
<S>                                                                                                              <C>
ARTICLE I THE MERGER..............................................................................................2

   1.1   THE MERGER...............................................................................................2
   1.2   EFFECTIVE TIME...........................................................................................2
   1.3   EFFECT OF THE MERGER.....................................................................................2
   1.4   CERTIFICATE OF INCORPORATION AND BY-LAWS OF SURVIVING COMPANY............................................2
   1.5   DIRECTORS AND OFFICERS...................................................................................3

ARTICLE II EFFECTS ON CAPITAL STOCK; EXCHANGE OF CERTIFICATES.....................................................3

   2.1   EFFECT OF MERGER ON CAPITAL STOCK........................................................................3
   2.2   CANCELLATION OF TREASURY SHARES..........................................................................5
   2.3   STOCK OPTIONS AND WARRANTS...............................................................................5
   2.4   ADJUSTMENTS TO EXCHANGE RATIOS...........................................................................5
   2.5   FRACTIONAL SHARES........................................................................................6
   2.6   SURRENDER OF CERTIFICATES................................................................................6
   2.7   NO FURTHER OWNERSHIP RIGHTS IN COMPANY STOCK.............................................................8
   2.8   CLOSING..................................................................................................8
   2.9   LOST, STOLEN OR DESTROYED CERTIFICATES...................................................................8
   2.10     TAX CONSEQUENCES......................................................................................8
   2.11     DISSENTERS' RIGHTS....................................................................................8
   2.12     CLOSING OF COMPANY TRANSFER BOOKS.....................................................................9
   2.13     AFFILIATES............................................................................................9

ARTICLE III  REPRESENTATIONS AND WARRANTIES OF COMPANIES..........................................................9

   3.1   ORGANIZATION OF THE COMPANY.............................................................................10
   3.2   THE COMPANY'S CAPITAL STRUCTURE.........................................................................10
   3.3   AUTHORITY; NO CONFLICT; REQUIRED FILINGS AND CONSENTS...................................................12
   3.4   FINANCIAL STATEMENTS....................................................................................13
   3.5   NO UNDISCLOSED LIABILITIES..............................................................................13
   3.6   ABSENCE OF CERTAIN CHANGES OR EVENTS....................................................................13
   3.7   TAXES...................................................................................................14
   3.8   PROPERTIES..............................................................................................15
   3.9   INTELLECTUAL PROPERTY...................................................................................15
   3.10     PRECLINICAL TESTING AND CLINICAL TRIALS..............................................................17
   3.11     AGREEMENTS, CONTRACTS AND COMMITMENTS................................................................17
   3.12     LITIGATION...........................................................................................18
   3.13     ENVIRONMENTAL MATTERS................................................................................18
   3.14     EMPLOYEE BENEFIT PLANS...............................................................................18
   3.15     COMPLIANCE WITH LAWS.................................................................................20
   3.16     CERTAIN REGULATORY MATTERS...........................................................................20
   3.17     TAX MATTERS..........................................................................................21
   3.18     REGISTRATION STATEMENT; PROXY STATEMENT/PROSPECTUS...................................................21
   3.19     LABOR MATTERS........................................................................................21
   3.20     INSURANCE............................................................................................22
   3.21     NO EXISTING DISCUSSIONS..............................................................................22
   3.22     OPINION OF FINANCIAL ADVISOR.........................................................................22
   3.23     SECTION 203 OF THE DGCL NOT APPLICABLE...............................................................22
   3.24     NO BROKERS...........................................................................................22
   3.25     STOCKHOLDER RIGHTS...................................................................................22
</TABLE>


                                       i
<PAGE>   3


<TABLE>
<CAPTION>
<S>                                                                                                             <C>
ARTICLE IV  REPRESENTATIONS AND WARRANTIES OR CURIS..............................................................23

   4.1   ORGANIZATION OF CURIS...................................................................................23
   4.2   CURIS' CAPITAL STRUCTURE................................................................................23
   4.3   AUTHORITY; NO CONFLICT; REQUIRED FILINGS AND CONSENTS...................................................24
   4.4   CONTINUITY OF BUSINESS ENTERPRISE; REORGANIZATION CLASSIFICATION........................................25

ARTICLE V  CONDUCT OF BUSINESS PENDING THE MERGER................................................................25

   5.1   CONDUCT OF BUSINESS BY COMPANY PENDING THE MERGER.......................................................25
   5.2   COOPERATION.............................................................................................28
   5.3   CONFIDENTIALITY.........................................................................................28
   5.4   CURIS CERTIFICATE OF INCORPORATION......................................................................28

ARTICLE VI  SOLICITATION OF OTHER PROPOSALS......................................................................28

   6.1   SOLICITATION OF OTHER PROPOSALS.........................................................................28

ARTICLE VII  ADDITIONAL AGREEMENTS...............................................................................32

   7.1   PROXY STATEMENT/PROSPECTUS; REGISTRATION STATEMENT......................................................32
   7.2   MEETINGS OF STOCKHOLDERS................................................................................33
   7.3   ACCESS TO INFORMATION...................................................................................33
   7.4   ALL REASONABLE EFFORTS; FURTHER ASSURANCES..............................................................34
   7.5   STOCK OPTIONS AND WARRANTS..............................................................................35
   7.6   NOTIFICATION OF CERTAIN MATTERS.........................................................................36
   7.7   LISTING ON THE NASDAQ...................................................................................37
   7.8   PUBLIC ANNOUNCEMENTS....................................................................................37
   7.9   ACCOUNTANT'S LETTERS....................................................................................37
   7.10     INDEMNIFICATION OF DIRECTORS AND OFFICERS............................................................37
   7.11     COVENANTS FOR TAX-FREE STATUS........................................................................38
   7.12     STOCKHOLDER AGREEMENTS...............................................................................38
   7.13     AFFILIATE AGREEMENTS.................................................................................39
   7.14     SEC FILINGS..........................................................................................40
   7.15     MAINTENANCE, PROSECUTION AND FILING OBLIGATIONS......................................................40
   7.16     CERTAIN AGREEMENTS...................................................................................40
   7.17     LOCK-UP AGREEMENTS...................................................................................40
   7.18     CURIS BOARD AUTHORIZATION............................................................................41
   7.19     BEST EFFORTS OBLIGATIONS.............................................................................41

ARTICLE VIII  CONDITIONS OF MERGER...............................................................................41

   8.1   CONDITIONS TO OBLIGATION OF ALL PARTIES TO EFFECT THE MERGER............................................41
   8.2   ADDITIONAL CONDITIONS TO OBLIGATION OF EACH PARTY TO EFFECT THE MERGER..................................42

ARTICLE IX  TERMINATION, AMENDMENT AND WAIVER....................................................................43

   9.1   TERMINATION.............................................................................................43
   9.2   EFFECT OF TERMINATION...................................................................................45
   9.3   FEES AND EXPENSES.......................................................................................45
   9.4   AMENDMENT...............................................................................................48
   9.5   WAIVER..................................................................................................48

ARTICLE X  GENERAL PROVISIONS....................................................................................48

   10.1     SURVIVAL OF REPRESENTATIONS AND WARRANTIES...........................................................48
   10.2     NOTICES..............................................................................................48
   10.3     CERTAIN DEFINITIONS..................................................................................50
   10.4     INTERPRETATION.......................................................................................51
   10.5     SEVERABILITY.........................................................................................51
   10.6     ENTIRE AGREEMENT.....................................................................................52
   10.7     ASSIGNMENT...........................................................................................52
</TABLE>


                                       ii
<PAGE>   4


<TABLE>
<CAPTION>
<S>                                                                                                             <C>
   10.8     PARTIES IN INTEREST..................................................................................52
   10.9     FAILURE OR INDULGENCE NOT WAIVER; REMEDIES CUMULATIVE................................................52
   10.10    GOVERNING LAW........................................................................................52
   10.11    COUNTERPARTS.........................................................................................53
</TABLE>


EXHIBIT A -    Form of Stockholder Agreement
EXHIBIT B -    Form of Certificate of Merger
EXHIBIT C -    Form of Articles of Merger
EXHIBIT D -    Curis Certificate of Incorporation
EXHIBIT E -    Form of Affiliate Agreement
EXHIBIT F -    Form of Lock-Up Agreement
EXHIBIT G -    Form of Certificate of Amendment to Certificate of Incorporation
EXHIBIT H -    Form of Articles of Amendment to Articles of Incorporation


                                      iii
<PAGE>   5


                                    SCHEDULES

Schedule 1.5        Directors and Officers of the Surviving Company


CREATIVE DISCLOSURE SCHEDULES

     See attached

ONTOGENY DISCLOSURE SCHEDULES

     See attached

REPROGENESIS DISCLOSURE SCHEDULES

     See attached

CURIS DISCLOSURE SCHEDULES

     None


                                       iv
<PAGE>   6


                          AGREEMENT AND PLAN OF MERGER

               This AGREEMENT AND PLAN OF MERGER, is made as of February 14,
2000 (the "Agreement") by and among CREATIVE BIOMOLECULES, INC., a Delaware
corporation ("Creative"), ONTOGENY, INC., a Delaware corporation ("Ontogeny"),
REPROGENESIS, INC., a Texas corporation ("Reprogenesis") and CURIS, INC. a
Delaware corporation ("Curis"). Each of Creative, Ontogeny, Reprogenesis and
Curis are sometimes referred to herein individually as a "Party" and
collectively as the "Parties". Each of Creative, Ontogeny and Reprogenesis are
also sometimes referred to herein individually as a "Company" and collectively
as the "Companies".

                                    RECITALS

               WHEREAS, each of the Parties desires to effectuate a corporate
reorganization to form a combined company to conduct the businesses of the
Companies;

               WHEREAS, Curis has been formed by the Companies for the purpose
of effectuating such corporate reorganization;

               WHEREAS, each Company is the owner of 100 shares of common stock,
par value $.01 per share, of Curis (the "Curis Common Stock");

               WHEREAS, the Board of Directors of each Party has deemed it
advisable and in the best interests of such Party and the stockholders of such
Party for such Party to effectuate the corporate reorganization upon the terms
and subject to the conditions set forth herein;

               WHEREAS, in furtherance of such corporate reorganization, the
Board of Directors of each Company has approved the merger of such Company and
each other company with and into Curis (the "Merger"), with Curis being the
surviving corporation of the Merger (the "Surviving Company") in accordance with
the General Corporation Law of the State of Delaware (the "DGCL") and the Texas
Business Corporation Act (the "TBCA") and subject to the conditions set forth
herein;

               WHEREAS, the Merger will result in, among other things, the
exchange and conversion of all of the issued and outstanding shares of capital
stock of the Companies into shares of common stock, par value $0.01 per share,
of the Surviving Company ("Surviving Company Common Stock");

               WHEREAS, as a condition to the willingness of, and as an
inducement to, the Parties to enter into this Agreement, contemporaneously with
the execution and delivery of this Agreement, certain holders of shares of
capital stock of the Companies are entering into agreements in the form of
EXHIBIT A hereto (a "Stockholder Agreement"), which Stockholder Agreements
provide for certain actions relating to the transactions contemplated by this
Agreement, including the agreement by such holders to vote such shares in favor
of the Merger;

               WHEREAS, for federal income tax purposes, it is intended that the
Merger shall qualify as a tax-free reorganization within the meaning of Section
368(a) of the United States


<PAGE>   7


Internal Revenue Code of 1986, as amended (the "Code") and the United States
Treasury Regulations promulgated thereunder; and

               WHEREAS, the Parties desire to make certain representations and
warranties and other agreements in connection with the Merger; and

               NOW, THEREFORE, in consideration of the foregoing and the mutual
representations, warranties, covenants and agreements herein contained, and
intending to be legally bound hereby, the Parties hereby agree as follows:

                                    ARTICLE I

                                   THE MERGER

     1.1  THE MERGER. At the Effective Time (as defined in Section 1.2) and
subject to and upon the terms and conditions of this Agreement and the
provisions of the DGCL and the TBCA, each Company shall be merged with and into
Curis, the separate corporate existence of each Company shall cease and Curis
shall, as the surviving corporation in the Merger, continue its existence under
the provisions of the DGCL as the Surviving Company.

     1.2  EFFECTIVE TIME. As promptly as practicable after the satisfaction or,
to the extent permitted hereunder, waiver of the conditions set forth in Article
VIII of this Agreement, the Parties shall cause the Merger to be consummated by
filing (a) the Certificate of Merger substantially in the form of EXHIBIT B
attached hereto (the "Certificate of Merger"), along with a certified copy of
this Agreement, if required, with the Secretary of State of the State of
Delaware, executed in accordance with the relevant provisions of the DGCL and
(b) the Articles of Merger substantially in the form of EXHIBIT C attached
hereto (the "Articles of Merger") with the Secretary of State of the State of
Texas, executed in accordance with the relevant provisions of the TBCA (the date
and time of the later of the issuance of the certificate of merger by the
Secretary of State of the State of Texas and the filing of the Certificate of
Merger, or such later date and time as may be specified in the Certificate of
Merger and the Articles of Merger by mutual agreement of the Parties, being the
"Effective Time").

     1.3  EFFECT OF THE MERGER. At the Effective Time, the effect of the Merger
shall be as provided in the applicable provisions of the DGCL and the TBCA.
Without limiting the generality of the foregoing, and subject thereto, at the
Effective Time all the property, rights, privileges, powers and franchises of
the Companies shall vest in the Surviving Company, and all debts, liabilities
and duties of the Companies shall become the debts, liabilities and duties of
the Surviving Company.

     1.4  CERTIFICATE OF INCORPORATION AND BY-LAWS OF SURVIVING COMPANY. The
Certificate of Incorporation of Curis shall be the Certificate of Incorporation
of the Surviving Company until thereafter amended as provided by the DGCL. The
By-laws of Curis shall be the By-laws of the Surviving Company until thereafter
amended as provided by the DGCL.


                                       2
<PAGE>   8


     1.5  DIRECTORS AND OFFICERS. At the Effective Time, the directors and
officers of the Surviving Company shall be those persons set forth on SCHEDULE
1.5 hereto, in each case until their respective successors are duly elected or
appointed and qualified or until their earlier death, resignation or removal in
accordance with the Surviving Company's Certificate of Incorporation and
By-laws.

                                   ARTICLE II

               EFFECTS ON CAPITAL STOCK; EXCHANGE OF CERTIFICATES

     2.1  EFFECT OF MERGER ON CAPITAL STOCK. At the Effective Time, by virtue of
the Merger and without any action on the part of the Parties hereto or the
holders of the following securities:

     (a)  Subject to the other provisions of this Article II, each share of
common stock, par value $.01 per share, of Creative (the "Creative Common
Stock") issued and outstanding immediately prior to the Effective Time (other
than any Creative Common Stock to be canceled pursuant to Section 2.2) shall be
converted automatically into the right to receive 0.30 of a fully paid and
nonassessable share of Surviving Company Common Stock (the "Creative Exchange
Ratio"), together with cash, if any, in lieu of any fraction of a share of
Surviving Company Common Stock, pursuant to Section 2.5 (the "Creative Merger
Consideration").

     (b)  Subject to the other provisions of this Article II, each share of (i)
common stock, par value $.01 per share, of Ontogeny (the "Ontogeny Common
Stock") issued and outstanding immediately prior to the Effective Time and (ii)
each share of Series A Convertible Preferred Stock, Series B Convertible
Preferred Stock, Series C Convertible Preferred Stock, Series C-1 Convertible
Preferred Stock, Series D Convertible Preferred Stock, Series E Convertible
Preferred Stock, Series F Convertible Preferred Stock and Series G Convertible
Preferred Stock of Ontogeny, each series with a par value $.01 per share
(collectively, the "Ontogeny Preferred Stock") issued and outstanding
immediately prior to the Effective Time (other than, in each case, any Ontogeny
Common Stock or Ontogeny Preferred Stock to be canceled pursuant to Section 2.2
and any Appraisal Shares (as defined in Section 2.11(a))) shall be converted
automatically into the right to receive 0.2564 of a fully paid and nonassessable
share of Surviving Company Common Stock (the "Ontogeny Exchange Ratio"),
together with cash, if any, in lieu of any fraction of a share of Surviving
Company Common Stock, pursuant to Section 2.5 (the "Ontogeny Merger
Consideration").

     (c)  (i) In addition to such number of shares of Surviving Company Common
Stock that each share of Series A preferred stock, par value $.01 per share, of
Reprogenesis (the "Reprogenesis Series A Stock") shall be entitled to pursuant
to Section 2.1 (c)(ii), each share of Reprogenesis Series A Stock issued and
outstanding immediately prior to the Effective Time (other than any Reprogenesis
Series A Stock to be canceled pursuant to Section 2.2 and any Dissenting Shares
(as defined in Section 2.11(b)) shall be converted automatically into the right
to receive the number of fully paid and nonassessable shares of Surviving
Company Common Stock equal to the Reprogenesis Series A Consideration divided by
2,702,702, together with cash, if any, in lieu of any fraction of a share of
Surviving Company Common Stock, pursuant to Section 2.5. "Reprogenesis Series A
Consideration" shall mean the lesser of (A) the number of


                                       3
<PAGE>   9


fully paid and nonassessable shares of Surviving Company Common Stock whose
aggregate Trailing Average Market Price equals $6,000,000 and (B) the
Reprogenesis Fully Diluted Merger Consideration.

          (ii) Subject to Section 2.1(c)(i), each share of common stock, par
value $.01 per share, of Reprogenesis (the "Reprogenesis Common Stock"), each
share of Reprogenesis Series A Stock and each share of Series B preferred stock,
par value $.01 per share, of Reprogenesis (the "Reprogenesis Series B Stock")
issued and outstanding immediately prior to the Effective Time (other than any
Reprogenesis Common Stock, Reprogenesis Series A Stock and Reprogenesis Series B
Stock to be canceled pursuant to Section 2.2 and any Dissenting Shares (as
defined in Section 2.11(b)) shall be converted automatically into the right to
receive 0.1956 (the "Reprogenesis Exchange Ratio") multiplied by a fraction, the
numerator of which is the Reprogenesis Fully Diluted Merger Consideration less
the Reprogenesis Series A Consideration and the denominator of which is the
Reprogenesis Fully Diluted Merger Consideration, of a fully paid and
nonassessable share of Surviving Company Common Stock, together with cash, if
any, in lieu of any fraction of a share of Surviving Company Common Stock,
pursuant to Section 2.5. The Creative Exchange Ratio, Ontogeny Exchange Ratio
and Reprogenesis Exchange Ratio are sometimes referred to individually herein as
an "Exchange Ratio".

          (iii) For the purposes of this Section 2.1(c), (A) "Trailing Average
Market Price" shall mean the average of the daily Market Price for each Business
Day on the twenty (20) consecutive Business Days the last day of which shall be
the fifth Business Day prior to the Effective Time, divided by the Creative
Exchange Ratio, (B) "Reprogenesis Fully Diluted Merger Consideration" shall mean
the product of the Reprogenesis Exchange Ratio and the aggregate number of
shares of Reprogenesis Common Stock, Reprogenesis Series A Stock and
Reprogenesis Series B Stock either issued and outstanding or subject to
outstanding options or warrants to purchase immediately prior to the Effective
Time (other than any Reprogenesis Common Stock, Reprogenesis Series A Stock and
Reprogenesis Series B Stock to be canceled pursuant to Section 2.2), (C) "Market
Price" at any date shall be deemed to be the last reported sale price of
Creative Common Stock, or, in case no such reported sale takes place on such
day, the average of the bid and asked prices, in either case as officially
reported by the Nasdaq National Market, or, if the Nasdaq National Market is no
longer reporting such information, as reasonably determined in good faith by
resolution of the Board of Directors of Reprogenesis, and (D) "Reprogenesis
Merger Consideration" shall mean the product of the Reprogenesis Exchange Ratio
and the number of shares of Reprogenesis Common Stock, Reprogenesis Series A
Stock and Reprogenesis Series B Stock issued and outstanding immediately prior
to the Effective Time (other than any Reprogenesis Common Stock, Reprogenesis
Series A Stock and Reprogenesis Series B Stock to be canceled pursuant to
Section 2.2 and other than any Dissenting Shares). The Reprogenesis Merger
Consideration, collectively with the Creative Merger Consideration and the
Ontogeny Merger Consideration, are referred to herein as the "Merger
Consideration".

     (d)  As of the Effective Time, all Company Common Stock and Company
Preferred Stock (together, "Company Stock") issued and outstanding immediately
prior to the Effective Time shall automatically be canceled and retired and
shall cease to exist, and each holder of a certificate representing any Company
Stock shall cease to have any rights with respect thereto, except the right to
receive the applicable Merger Consideration and any cash in lieu of fractional


                                       4
<PAGE>   10


shares of Surviving Company Common Stock to be issued or paid in consideration
therefor upon surrender of such certificate in accordance with Section 2.5
hereof, without interest.

     (e)  As of the Effective Time, all shares of Curis Common Stock issued and
outstanding immediately prior to the Effective Time shall no longer be
outstanding and shall automatically be cancelled and retired and shall cease to
exist, and each holder of a certificate representing any Curis Common Stock
shall cease to have any rights with respect thereto.

     2.2  CANCELLATION OF TREASURY SHARES. Each share of Creative Common Stock
held in the treasury of Creative and each share of Creative Common Stock, if
any, owned by any wholly-owned subsidiary of Creative or by Curis immediately
prior to the Effective Time shall be canceled and extinguished without any
conversion thereof. Each share of Ontogeny Common Stock and Ontogeny Preferred
Stock held in the treasury of Ontogeny and each share of Ontogeny Common Stock
and Ontogeny Preferred Stock, if any, owned by any wholly-owned subsidiary of
Ontogeny or by Curis immediately prior to the Effective Time shall be canceled
and extinguished without any conversion thereof. Each share of Reprogenesis
Common Stock and Reprogenesis Preferred Stock held in the treasury of
Reprogenesis and each share of Reprogenesis Common Stock and Reprogenesis
Preferred Stock, if any, owned by any wholly-owned subsidiary of Reprogenesis or
by Curis immediately prior to the Effective Time shall be canceled and
extinguished without any conversion thereof.

     2.3  STOCK OPTIONS AND WARRANTS.

     (a)  At the Effective Time, each outstanding Company Stock Option under the
Company Stock Plans, whether vested or unvested, shall, in accordance with the
terms of such Company Stock Option and such Company Stock Plan, by virtue of the
Merger and without any action on the part of the holder thereof, become and
represent an option to acquire, on the same terms and conditions as were
applicable under such Company Stock Option, the same number of shares of
Surviving Company Common Stock as the holder of such Company Stock Option would
have been entitled to receive pursuant to the Merger had such holder exercised
such option in full immediately prior to the Effective Time, as further set
forth in Section 7.5.

     (b)  At the Effective Time, each outstanding Company Warrant (other than
any Company Warrant that by its terms otherwise expires by virtue of the Merger)
shall, in accordance with the terms of such Company Warrant, by virtue of the
Merger and without any action on the part of the holder thereof, become and
represent a warrant to acquire, on the same terms and conditions as were
applicable under such Company Warrant, the same number of shares of Surviving
Company Common Stock as the holder of such Company Warrant would have been
entitled to receive pursuant to the Merger (including with respect to the
treatment of fractional shares) had such holder exercised such Company Warrant
in full immediately prior to the Effective Time, as further set forth in Section
7.5

     2.4  ADJUSTMENTS TO EXCHANGE RATIOS. Without limiting any other provision
of this Agreement, the applicable Exchange Ratio or Exchange Ratios shall be
correspondingly adjusted to reflect fully the effect of any stock split, reverse
split, stock dividend (including any dividend or distribution of securities
convertible into Company Stock), reorganization, recapitalization,
reclassification, conversion, consolidation, contribution or exchange of shares
or other like


                                       5
<PAGE>   11


change with respect to Curis Common Stock or Company Stock occurring after the
date hereof and prior to the Effective Time.

     2.5  FRACTIONAL SHARES. No fraction of a share of Surviving Company Common
Stock will be issued hereunder, but in lieu thereof each holder of Company Stock
who would otherwise be entitled to a fraction of a share of Surviving Company
Common Stock (after aggregating all fractional shares of Surviving Company
Common Stock to be received by such holder) shall receive from the Surviving
Company an amount of cash (rounded down to the nearest whole cent), without
interest, equal to the product of such fraction multiplied by the Market Value
(as defined below) of the Surviving Company Common Stock. The "Market Value" of
the Surviving Company Common Stock means the closing price per share of
Surviving Company Common Stock (rounded to the nearest cent) on the NASDAQ
National Market (as reported in the Wall Street Journal, or, if not reported
therein, any other authoritative source selected by the Surviving Company) on
the first day of trading of shares of Surviving Company Common Stock.

     2.6  SURRENDER OF CERTIFICATES.

     (a)  EXCHANGE AGENT. Prior to the Effective Time, Curis shall designate one
or more Persons to act as Exchange Agent hereunder.

     (b)  SURVIVING COMPANY TO PROVIDE COMMON STOCK. Promptly after the
Effective Time, the Surviving Company shall make available to the Exchange Agent
for exchange in accordance with this Article II, through such reasonable
procedures as the Surviving Company may adopt, the shares of Surviving Company
Common Stock issuable pursuant to Section 2.1 in exchange for outstanding
Company Stock, together with an estimated amount of cash to be paid pursuant to
Section 2.5 in lieu of fractional shares.

     (c)  EXCHANGE PROCEDURES. Promptly after the Effective Time, the Surviving
Company shall cause the Exchange Agent to mail to each holder of record of a
certificate or certificates (the "Certificates") which immediately prior to the
Effective Time represented outstanding Company Stock whose shares were converted
into the right to receive shares of Surviving Company Common Stock pursuant to
Section 2.1, a letter of transmittal (which shall specify that delivery shall be
effected, and risk of loss and title to the Certificates shall pass, only upon
delivery of the Certificates to the Exchange Agent and shall be in such form and
have such other provisions as the Surviving Company may reasonably specify) and
instructions for use in effecting the surrender of the Certificates in exchange
for certificates representing shares of Surviving Company Common Stock and cash
in lieu of the fraction of a share of Surviving Company Common Stock, if any,
pursuant to Section 2.5 hereof. Upon surrender of a Certificate for cancellation
to the Exchange Agent, together with such letter of transmittal, duly completed
and validly executed in accordance with the instructions thereto, the holder of
such Certificate shall be entitled to receive in exchange therefor, a
certificate representing the number of whole shares of Surviving Company Common
Stock and payment in lieu of fractional shares which such holder has the right
to receive pursuant to Section 2.5, and the Certificate so surrendered shall
forthwith be canceled. Until so surrendered, each outstanding Certificate that,
prior to the Effective Time, represented Company Stock will be deemed from and
after the Effective Time, for all corporate purposes, other than the payment of
dividends, to evidence the right to receive the number of full shares of
Surviving Company Common Stock into which such Company


                                       6
<PAGE>   12


Stock shall have been so converted and the right to receive an amount in cash in
lieu of the issuance of any fractional shares in accordance with Section 2.5.
Any portion of the shares of Surviving Company Common Stock deposited with the
Exchange Agent pursuant to this Section 2.6(c) which remains undistributed to
the holders of the Certificates representing Company Common Shares for six (6)
months after the Effective Time shall be delivered to Surviving Company, upon
demand, and any holders of Company Stock who have not theretofore complied with
this Article II shall thereafter look only to the Surviving Company for
Surviving Company Common Stock, any cash in lieu of fractional shares of
Surviving Company Common Stock and any dividends or distributions with respect
to Surviving Company Common Stock to which such holders may be entitled.

     (d)  DISTRIBUTIONS WITH RESPECT TO UNEXCHANGED SHARES. No dividends or
other distributions declared or made after the Effective Time with respect to
Surviving Company Common Stock with a record date after the Effective Time will
be paid to the holder of any unsurrendered Certificate with respect to the
shares of Surviving Company Common Stock represented thereby until the holder of
record of such Certificate shall surrender such Certificate. Subject to
applicable escheat law, following surrender of any such Certificate, there shall
be paid to the record holder of the certificates representing whole shares of
Surviving Company Common Stock issued in exchange therefor, without interest, at
the time of such surrender, the amount of dividends or other distributions with
a record date after the Effective Time theretofore paid with respect to such
whole shares of Surviving Company Common Stock.

     (e)  TRANSFERS OF OWNERSHIP. If any certificate for shares of Surviving
Company Common Stock is to be issued in a name other than that in which the
Certificate surrendered in exchange therefor is registered, it will be a
condition of the issuance thereof that the Certificate so surrendered will be
properly endorsed and otherwise in proper form for transfer and that the Person
requesting such exchange will have paid to Surviving Company, or any agent
designated by it, any transfer or other taxes required by reason of the issuance
of a certificate for shares of Surviving Company Common Stock in any name other
than that of the registered holder of the certificate surrendered, or
established to the satisfaction of Surviving Company or any agent designated by
it that such tax has been paid or is not payable.

     (f)  NO LIABILITY. Notwithstanding anything to the contrary in this
Agreement, none of the Exchange Agent or Surviving Company shall be liable to a
holder of Company Stock for any Surviving Company Common Stock or any amount
properly paid to a public official pursuant to any applicable abandoned
property, escheat or similar law.

     (g)  WITHHOLDING OF TAX. The Surviving Company and the Exchange Agent will
be entitled to deduct and withhold from the consideration otherwise payable
pursuant to this Agreement to any holder of Company Stock such amounts as the
Surviving Company (or any Affiliate thereof) or the Exchange Agent are required
to deduct and withhold with respect to the making of such payment under the
Code, or any provision of federal, state, local or foreign Tax law (as defined
below). To the extent that amounts are so withheld by the Surviving Company or
the Exchange Agent, such withheld amounts will be treated for all purposes of
this Agreement as having been paid to the holder of Company Stock in respect of
whom such deduction and withholding were made by Surviving Company.


                                       7
<PAGE>   13


     2.7  NO FURTHER OWNERSHIP RIGHTS IN COMPANY STOCK. All shares of Surviving
Company Common Stock issued upon the surrender for exchange of Company Stock in
accordance with the terms of this Article II (including any cash paid in respect
thereof) shall be deemed to have been issued in full satisfaction of all rights
pertaining to such Company Stock under this Article II, and there shall be no
further registration of transfers on the records of the Surviving Company of
shares of Company Stock which were outstanding immediately prior to the
Effective Time. If, after the Effective Time, Certificates are presented to the
Surviving Company for any reason, they shall be canceled and exchanged as
provided in this Article II.

     2.8  CLOSING. Unless this Agreement shall have been terminated and the
transactions contemplated by this Agreement abandoned pursuant to the provisions
of Article IX, and subject to the provisions of Article VIII, the closing of the
Merger (the "Closing") will take place at 10:00 a.m. (Eastern time) on a date
(the "Closing Date") to be mutually agreed upon by the parties, which date shall
be not later than the third Business Day after all the conditions set forth in
Article VIII shall have been satisfied (or waived in accordance with Section
9.5, to the extent the same may be waived), unless another time and/or date is
agreed to in writing by the parties. The Closing shall take place at the offices
of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., Boston, Massachusetts,
unless another place is agreed to in writing by the parties.

     2.9  LOST, STOLEN OR DESTROYED CERTIFICATES. In the event any Certificates
shall have been lost, stolen or destroyed, the Exchange Agent shall issue in
exchange for such lost, stolen or destroyed certificates, upon the making of an
affidavit of that fact by the holder thereof, such shares of Surviving Company
Common Stock and cash for fractional shares, if any, as may be required pursuant
to Section 2.5; PROVIDED that the Surviving Company may, as a condition
precedent to the issuance thereof, require the owner of such lost, stolen or
destroyed certificates to deliver a bond in such sum as it may reasonably direct
as indemnity against any claim that may be made against the Surviving Company or
the Exchange Agent with respect to the Certificates alleged to have been lost,
stolen or destroyed.

     2.10 TAX CONSEQUENCES. For federal income tax purposes, the Parties intend
that the Merger be treated as a reorganization within the meaning of Section
368(a) of the Code, and that this Agreement shall be, and is hereby, adopted as
a plan of reorganization for purposes of Section 368 of the Code. The parties
shall not take a position on any Tax Return (as defined below) inconsistent with
this Section 2.10.

     2.11 DISSENTERS' RIGHTS.

     (a)  Notwithstanding anything in this Agreement to the contrary, shares
("Appraisal Shares") of capital stock of Ontogeny that are outstanding
immediately prior to the Effective Time and that are held by any Person who is
entitled to demand and properly demands appraisal of such Appraisal Shares
pursuant to, and who complies in all respects with, Section 262 of the DGCL
("Section 262") shall not be converted into Merger Consideration as provided in
Section 2.1, but rather the holders of Appraisal Shares shall be entitled to
payment of the fair market value of such Appraisal Shares in accordance with
Section 262; provided, however, that if any such holder shall fail to perfect or
otherwise shall waive, withdraw or lose the right to appraisal under Section
262, then the right of such holder to be paid the fair value of such holder's
Appraisal Shares shall cease and such Appraisal Shares shall be deemed to have
been converted


                                       8
<PAGE>   14


as of the Effective Time into, and to have become exchangeable solely for the
right to receive, the applicable Merger Consideration as provided in Section
2.1. Ontogeny shall give prompt notice to Curis of any demands received by
Ontogeny for appraisal of any shares of capital stock of Ontogeny, and Curis
shall have the right to participate in and direct all negotiations and
proceedings with respect to such demands. Prior to the Effective Time, Ontogeny
shall not, without the prior written consent of Curis, make any payment with
respect to, or settle or offer to settle, any such demands, or agree to do any
of the foregoing.

     (b)  Notwithstanding anything in this Agreement to the contrary, shares
("Dissenting Shares") of capital stock of Reprogenesis that are outstanding
immediately prior to the Effective Time and that are held by any Person who is
entitled to make and properly makes demand for payment of the fair value of such
Dissenting Shares pursuant to, and who complies in all respects with, Article
5.12 of the TBCA ("Article 5.12") shall not be converted into Merger
Consideration as provided in Section 2.1, but rather the holders of Dissenting
Shares shall be entitled to payment of the fair value of such Dissenting Shares
in accordance with Article 5.12; provided, however, that if any such holder
shall fail to perfect or otherwise shall waive, withdraw or lose his right to
payment of the fair value under Article 5.12, then the right of such holder to
be paid the fair value of such holder's Dissenting Shares shall cease and such
Dissenting Shares shall be deemed to have been converted as of the Effective
Time into, and to have become exchangeable solely for the right to receive, the
applicable Merger Consideration as provided in Section 2.1. Reprogenesis shall
give prompt notice to Curis of any demands received by Reprogenesis for the
payment of the fair value of any shares of capital stock of Reprogenesis, and
Curis shall have the right to participate in and direct all negotiations and
proceedings with respect to such demands. Prior to the Effective Time,
Reprogenesis shall not, without the prior written consent of Curis, make any
payment with respect to, or settle or offer to settle, any such demands, or
agree to do any of the foregoing.

     2.12 CLOSING OF COMPANY TRANSFER BOOKS. At the Effective Time, the stock
transfer books of each Company shall be closed and no transfer of shares of
Company Stock shall thereafter be made. If, after the Effective Time,
certificates representing shares of Company Stock are presented to the Surviving
Company, they shall be canceled and presented to the Exchange Agent in
accordance with Section 2.6.

     2.13 AFFILIATES. Notwithstanding anything herein to the contrary,
Certificates surrendered for exchange by any Person who is a director or
executive officer of a Company or a holder of shares of 10% or more of such
Company's Voting Stock, shall not be exchanged until the Surviving Company has
received an Affiliate Agreement from such Person.

                                   ARTICLE III

                   REPRESENTATIONS AND WARRANTIES OF COMPANIES

     Each Company hereby represents and warrants to each other Company that the
statements contained in this Article III are true and correct with respect to
it, except as set forth herein or in the disclosure schedule attached by such
Company to this Agreement (for each respective Company, the "Company Disclosure
Schedule"). The Company Disclosure Schedule shall be arranged in sections
corresponding to the numbered and lettered sections contained in


                                       9
<PAGE>   15


this Article III, and the disclosure in any section shall qualify other sections
in this Article III only the extent that it is reasonably apparent from a
reading of such disclosure that it also qualifies or applies to such other
sections. For the purposes of this Article III, all references to a Company
shall include such Company and its Subsidiaries, and all representations and
warranties about a Company shall be construed as representations and warranties
about each of its Subsidiaries as well, unless the context requires otherwise
(including, by way of example, Section 3.7(c) hereof).

     3.1  ORGANIZATION OF THE COMPANY. The Company is a corporation duly
organized, validly existing and in good standing under the laws of the state of
its organization. The Company has all requisite corporate power to own, lease
and operate its properties and assets and to carry on the business as now being
conducted and as proposed to be conducted, and is duly qualified to do business
and is in good standing as a foreign corporation in each jurisdiction in which
the failure to be so qualified, individually or in the aggregate, would be
reasonably likely to have a material adverse effect on the business, properties,
financial condition, results of operations or prospects of the Company, or to
have a material adverse effect on the ability of the Company to consummate the
transactions contemplated by this Agreement (a "Company Material Adverse
Effect"); provided, however, that for purposes of this Agreement, any adverse
change in the stock price of a Company whose stock is publicly traded (each, a
"Public Company") in and of itself, as quoted on the Nasdaq National Market,
shall not be taken into account in determining whether there has been or would
be a "Company Material Adverse Effect" on or with respect to the Company.

     3.2  THE COMPANY'S CAPITAL STRUCTURE.

     (a)  The authorized capital stock of the Company is as set forth in the
Company Disclosure Schedule. As of February 10, 2000, the number of shares of
common stock of the Company ("Company Common Stock") and preferred stock of the
Company ("Company Preferred Stock") issued and outstanding or held in the
treasury of the Company are as set forth on the Company Disclosure Schedule, and
all of such shares are validly issued, fully-paid and non-assessable. The
Company Disclosure Schedule shows the number of shares of Company Common Stock
reserved for future issuance pursuant to stock options granted and outstanding
as of the date of this Agreement, and the plans under which such options were
granted (collectively, the "Company Stock Plans") and sets forth a complete and
accurate list of all holders of options outstanding as of the date of this
Agreement to purchase shares of Company Common Stock (such outstanding options,
the "Company Stock Options") under the Company Stock Plans, indicating the
number of shares of Company Common Stock subject to each Company Stock Option,
and the exercise price, the date of grant and the expiration date thereof. The
Company Disclosure Schedule shows the number of shares of Company Common Stock
reserved for future issuance pursuant to warrants or other outstanding rights to
purchase shares of Company Common Stock outstanding as of the date of this
Agreement (such outstanding warrants or other rights, the "Company Warrants")
and the agreement or other document under which such Company Warrants were
granted and sets forth a complete and accurate list of all holders of Company
Warrants indicating the number and type of shares of Company Common Stock
subject to each Company Warrant, and the exercise price, the date of grant and
the expiration date thereof. All outstanding shares of Company Common Stock are,
and all shares of Company Common Stock subject to issuance as specified above
are, duly authorized and, upon issuance on


                                       10
<PAGE>   16


the terms and conditions specified in the instruments pursuant to which they are
issuable, shall be, validly issued, fully paid and nonassessable and not subject
to or issued in violation of any purchase option, call option, right of first
refusal, preemptive right, subscription right or any similar right under any
provision of the DGCL or the TBCA, the Company's Certificate or Articles of
Incorporation or By-laws or any agreement to which the Company is a party or is
otherwise bound. There are no obligations, contingent or otherwise, of the
Company to repurchase, redeem or otherwise acquire any shares of Company Common
Stock or any other capital stock of the Company or to provide funds to or make
any investment (in the form of a loan, capital contribution or otherwise) in any
other entity.

     (b)  Except for the Company Stock Plans, the Company Warrants and shares of
capital stock and other securities of the Company issuable pursuant to the
foregoing, (i) there are no equity securities of any class of the Company, or
any security exchangeable into or exercisable for such equity securities,
issued, reserved for issuance or outstanding, and (ii) there are no options,
warrants, equity securities, calls, rights, commitments or agreements of any
character to which the Company is a party or by which it is bound obligating the
Company to issue, deliver or sell, or cause to be issued, delivered or sold,
additional shares of capital stock of or other equity interests in the Company
or obligating the Company to grant, extend, accelerate the vesting of, otherwise
modify or amend or enter into any such option, warrant, equity security, call,
right, commitment or agreement. To the best Knowledge of the Company, other than
the Stockholder Agreements, there are no voting trusts, proxies or other voting
agreements or understandings with respect to the shares of capital stock of or
other equity interests in the Company.

     (c)  There are no bonds, debentures, notes or other indebtedness of the
Company with voting rights (or convertible into, or exchangeable for, securities
with voting rights) on any matters on which stockholders of the Company may
vote.

     (d)  The Company Disclosure Schedule sets forth all Subsidiaries of the
Company and the authorized capital stock or other equity interests of such
Subsidiaries. The Company owns all of the outstanding capital stock or other
equity interests of such Subsidiaries. As of the date of this Agreement, the
number of shares of common stock and preferred stock, or amount of other equity
interests, of any such Subsidiary issued and outstanding or held in such
Subsidiary's treasury are as set forth on the Company Disclosure Schedule, and
all of such shares or other equity interests are duly authorized, validly
issued, fully-paid and non-assessable and not subject to or issued in violation
of any purchase option, call option, right of first refusal, preemptive right,
subscription right or any similar right under any provision of the DGCL or the
TBCA (or other law governing such Subsidiary's organization), the Certificate or
Articles of Incorporation or By-laws (or other organizational documents) of such
Subsidiary or any agreement to which such Subsidiary is a party or is otherwise
bound. There are no obligations, contingent or otherwise, of such Subsidiary to
repurchase, redeem or otherwise acquire any shares of its capital stock or other
equity interests or to provide funds to or make any investment (in the form of a
loan, capital contribution or otherwise) in any other entity. There are no
options, warrants, equity securities, calls, rights, commitments or agreements
of any character to which any such Subsidiary is a party or by which it is bound
obligating it to issue, deliver or sell, or cause to be issued, delivered or
sold, shares of capital stock of or other equity interests in such Subsidiary.


                                       11
<PAGE>   17


     (e)  Each Subsidiary of the Company is duly organized, validly existing and
in good standing under the laws of the jurisdiction of its organization. Each
such Subsidiary has all requisite power (corporate and otherwise) to own, lease
and operate its properties and assets and to carry on the business as now being
conducted and as proposed to be conducted, and is duly qualified to do business
and is in good standing as a foreign corporation or other entity in each
jurisdiction in which the failure to be so qualified, individually or in the
aggregate, would be reasonably likely to have a Company Material Adverse Effect.
Each Subsidiary of the Company is inactive, has not conducted any business in
the last five years, and has not owned, leased or operated any properties or
assets in the last five years.

     3.3  AUTHORITY; NO CONFLICT; REQUIRED FILINGS AND CONSENTS.

     (a)  The Company has all requisite power and authority to enter into this
Agreement and to consummate the transactions contemplated by this Agreement. The
execution and delivery of this Agreement and the consummation of the
transactions contemplated by this Agreement by the Company have been duly
authorized by all the necessary corporate action on the part of the Company,
subject only to the approval of the Merger by the Company's stockholders under
the DGCL or the TBCA. This Agreement has been duly executed and delivered by the
Company and constitutes the valid and binding obligations of the Company,
enforceable in accordance with its terms, subject to bankruptcy, insolvency,
fraudulent transfer, reorganization, moratorium and similar laws of general
applicability relating to or affecting creditors' rights and to general equity
principles (the "Bankruptcy and Equity Exception").

     (b)  The execution and delivery of this Agreement by the Company does not,
and the consummation of the transactions contemplated by this Agreement will
not, (i) conflict with, or result in any violation or breach of, any provision
of the Certificate or Articles of Incorporation or By-laws of the Company, (ii)
result in any violation or breach of, or constitute (with or without notice or
lapse of time, or both) a default (or give rise to a right of termination,
cancellation or acceleration of any obligation or loss of any material benefit)
under, or require a consent or waiver under, any of the terms, conditions or
provisions of any note, bond, mortgage, indenture, lease, license, contract or
other agreement, instrument or obligation to which the Company is a party or by
which it or any of its properties or assets may be bound, or (iii) conflict with
or violate any permit, concession, franchise, license, judgment, order, decree,
statute, law, ordinance, rule or regulation applicable to the Company or by
which it or any of its properties or assets may be bound or (iv) constitute a
change in control or comparable event under any of the terms, conditions or
provisions of any note, bond mortgage, indenture, lease, license, contract or
other agreement, instrument or obligation to which the Company is a party or by
which it or any of its properties or assets may be bound, which change of
control or comparable event will give rise to a right of termination,
cancellation or acceleration of any obligation or loss of any material benefit,
except in the case of (ii), (iii) and (iv) for any such conflicts, violations,
defaults, terminations, cancellations or accelerations which are not,
individually or in the aggregate, reasonably likely to have a Company Material
Adverse Effect.

     (c)  No consent, approval, license, permit, order or authorization of, or
registration, declaration or filing with, any Governmental Authority is required
by or with respect to the Company in connection with the execution and delivery
of this Agreement or the consummation of the transactions contemplated hereby,
except for (i) the filing of a pre-merger notification


                                       12
<PAGE>   18


report under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as
amended, ("HSR Act"), (ii) the filing of the Certificate of Merger with the
Delaware Secretary of State, (iii) the filing of the Articles of Merger with the
Secretary of State of the State of Texas and the issuance of a certificate of
merger by the Secretary of State of the State of Texas, (iv) the filing of the
Joint Proxy Statement (as defined in Section 3.18 below) with the Securities and
Exchange Commission ("SEC") in accordance with the Securities Exchange Act of
1934, as amended (the "Exchange Act"), (v) such, consents, approvals, orders,
authorizations, registrations, declarations and filings as may be required under
applicable state securities laws and (vi) such other consents, licenses,
permits, orders, authorizations, filings, approvals and registrations which, if
not obtained or made, would not be reasonably likely, individually or in the
aggregate, to have a Company Material Adverse Effect. The stockholder vote
required for the approval of this Agreement and the Merger by each Company is
set forth in the Company Disclosure Schedule.

     3.4  FINANCIAL STATEMENTS.

     (a)  Each Company has provided or made available to each other Company (i)
its audited consolidated balance sheets and statements of income, changes in
stockholders' equity and cash flows as of and for each of the last three fiscal
years, and (ii) the unaudited consolidated balance sheet and statements of
income, changes in stockholders' equity and cash flows as of and for the twelve
months ended as of December 31, 1999 (the "Company Financial Statements").

     (b)  Each Company Financial Statement (including, in each case, any related
notes and schedules) (i) was prepared in accordance with generally accepted
accounting principles ("GAAP") applied on a consistent basis throughout the
periods involved (except as may be indicated in the notes to such financial
statements or, in the case of unaudited statements, as permitted by Form 10-Q of
the SEC or, with respect to Ontogeny and Reprogenesis, the absence of notes
thereto) and (iii) fairly presented or will fairly present the consolidated
financial position of the Company as of the dates and the consolidated results
of its operations and cash flows for the period indicated, consistent with the
books and records of the Company, except that the unaudited financial statements
were or are subject to normal and recurring year-end adjustments which were not
or are not expected to be material in amount. The unaudited balance sheet of the
Company as of December 31, 1999 is referred to herein as the "Company Balance
Sheet."

     3.5  NO UNDISCLOSED LIABILITIES. Except for normal or recurring liabilities
incurred since the date of the Company Balance Sheet in the ordinary course of
business and consistent with past practices, the Company does not have any
liabilities, either accrued, contingent or otherwise (whether or not required to
be reflected in financial statements in accordance with generally accepted
accounting principles), and whether due or to become due, which individually or
in the aggregate are reasonably likely to have a Company Material Adverse
Effect.

     3.6  ABSENCE OF CERTAIN CHANGES OR EVENTS. Since the date of the Company
Balance Sheet, the Company has conducted its businesses only in the ordinary
course and in a manner consistent with past practice and, since such date, there
has not been (i) any event, change or development in the financial condition,
results of operations, business, properties or prospects of the Company, that
individually or in the aggregate has had, or is reasonably likely to have, a
Company Material Adverse Effect; (ii) any damage, destruction or loss (whether
or not covered by insurance) with respect to the Company having a Company
Material Adverse Effect; (iii) any


                                       13
<PAGE>   19


material change by the Company in its accounting methods not required pursuant
to generally accepted accounting principles or practices to which both the other
Companies have not previously consented in writing; (iv) any revaluation by the
Company of any of its assets having a Company Material Adverse Effect; or (v)
any other action or event that would have required the consent of the other
Companies pursuant to Section 5.1 of this Agreement had such action or event
occurred after the date of this Agreement.

     3.7  TAXES.

     (a)  For the purposes of this Agreement, a "Tax" or, collectively, "Taxes,"
means any and all material federal, state, local and foreign taxes, assessments
and other governmental charges, duties, impositions and liabilities, including
taxes based upon or measured by gross receipts, income, profits, sales, use and
occupation, and value added, ad valorem, transfer, gains, franchise,
withholding, payroll, recapture, employment, excise, unemployment insurance,
social security, business license, occupation, business organization, stamp,
environmental and property taxes, together with all interest, penalties and
additions imposed with respect to such amounts and any obligations under any
agreements or arrangements with any other person with respect to such amounts
and including any liability for taxes of a predecessor entity.

     (b)  The Company has:

          (i)  (y) as of the date of this Agreement, filed all federal, state,
     local and foreign tax returns and reports required to be filed by it prior
     to such date (taking into account extensions) and (z) as of the Closing
     Date, filed all federal, state, local and foreign tax returns and reports
     required to be filed by it prior to such date (taking into account
     extensions), and in each case all such returns ("Tax Returns") were
     complete and accurate in all respects;

          (ii) (y) as of the date of this Agreement, paid or accrued all Taxes
     due and payable as of such date and (z) as of the Closing Date, paid or
     accrued all Taxes due and payable as of such date, in each case whether or
     not so reflected on such returns or reports; and

          (iii) paid or accrued all Taxes for which a notice of assessment or
     collection has been received (other than amounts being contested in good
     faith by appropriate proceedings);

     except in the case of clause (i), (ii) or (iii) for any such filings,
     inaccuracies, payments or accruals which are not reasonably likely,
     individually or in the aggregate, to have a Company Material Adverse
     Effect. Unpaid Taxes for periods prior to the date hereof do not materially
     exceed accruals and reserves for Taxes (exclusive of any accruals and
     reserves for Taxes established to reflect timing difference between book
     and Tax income) as set forth on the Company Balance Sheet. Neither the
     Internal Revenue Service (the "IRS") nor any other taxing authority has
     asserted any claim for Taxes, or to the Knowledge of the chief executive
     officer or the principal accounting officer of the Company, is threatening
     to assert any claims for Taxes, which claims, individually or in


                                       14
<PAGE>   20


     the aggregate, are reasonably likely to have a Company Material Adverse
     Effect. The Company has withheld or collected and paid over to the
     appropriate Governmental Authorities (or are properly holding for such
     payment) all Taxes required by law to be withheld or collected, except for
     amounts which are not reasonably likely, individually or in the aggregate,
     to have a Company Material Adverse Effect. There are no Liens for Taxes
     upon the assets of the Company (other than Liens for Taxes that are not yet
     due or that are being contested in good faith by appropriate proceedings),
     except for Liens which are not reasonably likely, individually or in the
     aggregate, to have a Company Material Adverse Effect.

     (c)  None of the Company and its Subsidiaries has been a member of an
affiliated group of corporations filing a consolidated federal income Tax Return
(other than a group the common parent of which was the Company). None of the
Company and its Subsidiaries has any actual or potential liability for any Taxes
of any person (other than the Company) under Treasury Regulation Section
1.1502-6 (or any similar provision of federal, state, local or foreign law), or
as a transferee or successor, by contract or otherwise.

     (d)  The Company is not a "consenting corporation" within the meaning of
Section 341(f) of the Code, and none of the assets of the Company are subject to
an election under Section 341(f) of the Code.

     (e)  The Company has not been a United States real property holding
corporation within the meaning of Section 897(c)(2) of the Code during the
applicable period specified in Section 897(c)(1)(A)(ii) of the Code.

     (f)  The Company has not made any payments, is not obligated to make any
payments, and is not a party to any agreement that could obligate it to make any
payments that will be an "excess parachute payment" under Section 280G of the
Code.

     3.8  PROPERTIES. The Company Disclosure Schedule sets forth a true and
complete list of all real property leased by the Company (collectively,
"Lease(s)") and the location of the premises. The Company is not in default
under any of such leases, except where the existence of such defaults,
individually or in the aggregate, is not reasonably likely to have a Company
Material Adverse Effect. The Company does not own and has never owned any real
property.

     3.9  INTELLECTUAL PROPERTY.

     (a)  The Company Disclosure Schedule sets forth a true and complete list of
each of the following items: (1) all patents and applications therefor,
including any patent term extensions or supplementary protection certificates,
registrations of trademarks (including service marks) and applications therefor,
domain names and registrations of copyrights and applications therefor that are
owned by the Company or that are licensed or sublicensed to the Company,
indicating in each case the nature of ownership thereof or license or sublicense
thereto, (2) all licenses, agreements and contracts relating to Intellectual
Property Rights (as defined below) pursuant to which the Company is entitled to
use any Intellectual Property Rights owned by any third party (the "Third Party
Licenses"), other than commercially available mass marketed shrink-wrap software
and commercially available research reagents, and (3) all


                                       15
<PAGE>   21


agreements under which the Company has granted any third party the right to use
any Intellectual Property Rights.

     (b)  To the Company's Knowledge, the Company owns, or is licensed,
sublicensed or otherwise possesses legally enforceable rights to use, pursuant
to the licenses, agreements and contracts listed in Section 3.9(a)(2) of the
Company Disclosure Schedule, all Intellectual Property Rights that are used or
necessary to conduct the business of the Company as currently conducted and that
are material, individually or in the aggregate, to the Company, including
without limitation all Intellectual Property Rights used or necessary to conduct
its ongoing and presently planned clinical programs (each of which (the "Ongoing
Clinical Programs") is deemed to be material to the Company) and all
Intellectual Property Rights that are now used or planned to be used or are
necessary to make, use or sell its planned products (as disclosed to each other
Company) after those products are approved for marketing and sale by the
appropriate health regulatory authorities (the "Company Intellectual Property
Rights"). For purposes hereof, "Intellectual Property Rights" means all patents,
including patent term extensions and supplementary protection certificates,
trademarks, trade names, domain names, service marks and copyrights, any
applications for and registrations of such patents, trademarks, trade names,
domain names, service marks and copyrights, and all processes, formulae,
methods, schematics, technology, know-how, computer software programs or
applications and tangible or intangible proprietary information or material.

     (c)  The execution and delivery of this Agreement and consummation of the
transactions contemplated hereby will not result in the breach of, or create on
behalf of any third party the right to terminate or modify, any license,
sublicense or other agreement relating to the Company Intellectual Property
Rights, including any Third Party License.

     (d)  All patents, including all patent term extensions and supplementary
protection certificates, registered trademarks, service marks and copyrights
under which the Company holds any rights and which are material to the business
of the Company are, to the Company's Knowledge, valid and subsisting, and all
applications for such patents, trademarks, service marks and copyrights are
subsisting and were filed in good faith. The Company has taken reasonable
measures to protect the proprietary nature of the Company Intellectual Property
Rights that are material to the business of the Company and to maintain in
confidence all trade secrets and confidential information owned or used by the
Company and that are material to the business of the Company. To the Knowledge
of the Company, no other person or entity is infringing, violating or
misappropriating any of the Company Intellectual Property Rights.

     (e)  To the Knowledge of the Company, none of the activities or business
previously or currently conducted by the Company, its licensees or assignees of
royalty-bearing Intellectual Property Rights ("IP Assignees") or planned to be
conducted (as disclosed to each other Company) by the Company, its licensees or
IP Assignees (including the manufacture, use and sale of the future products
which are the subject of Ongoing Clinical Programs for any clinical indications)
which is material to the business of the Company infringes, violates or
constitutes a misappropriation of, any Intellectual Property Rights of any other
person or entity. The Company has not received any complaint, claim or notice
alleging any such infringement, violation or misappropriation, present or
future.


                                       16
<PAGE>   22


     (f)  The Company is not a party to any agreement under which, following the
Closing, a third party would be entitled to receive a license or any other right
in or to Intellectual Property Rights currently held by either of the other
Companies or any of such other Companies' Affiliates or which, following the
Closing, would restrict or limit the business or operations currently conducted
by either of the other Companies or any of their Affiliates.

     3.10 PRECLINICAL TESTING AND CLINICAL TRIALS. The human clinical trials,
animal studies and other preclinical tests conducted by the Company or in which
the Company has participated, and such studies and tests conducted on behalf of
the Company, were and, if still pending, are being conducted in all material
respects in accordance with experimental protocols, informed consents,
procedures and controls generally used by qualified experts in the preclinical
or clinical study of products comparable to those being developed by the
Company. Neither the Company, nor any agent or representative of the Company
nor, to the Knowledge of the Company, any of its licensees and IP Assignees, has
received any notices or correspondence from the Food and Drug Administration
("FDA") or any other Governmental Authority requiring the termination,
suspension or modification (other than such modifications as are normal in the
regulatory process) of any animal studies, preclinical tests or clinical trials
conducted by or on behalf of the Company or, to the Knowledge of the Company,
such licensees and IP Assignees, or in which the Company or, to the Knowledge of
the Company, such licensees and IP Assignees, have participated. To the
Company's Knowledge, no clinical investigator acting for the Company has been or
is now, or is threatened to become, the subject of any disbarment or
disqualification proceedings by any regulatory agency.

     3.11 AGREEMENTS, CONTRACTS AND COMMITMENTS.

     (a)  There are no contracts or agreements that are material contracts (as
defined in Item 601(b)(10) of Regulation S-K) with respect to the Company
("Company Material Contracts") other than as set forth in the Company Disclosure
Schedule. No Company Material Contract has expired by its terms or has been
terminated in accordance with its terms (nor has the Company received notice of
any such termination) and each Company Material Contract is in full force and
effect. The Company is not in violation of or in default under (nor does there
exist any condition which, upon the passage of time or the giving of notice or
both, would cause such a violation of or default under) any lease, permit,
concession, franchise, license or other contract or agreement to which it is a
party or by which it or any of its properties or assets is bound, except for
violations or defaults that, individually or in the aggregate, have not resulted
in and are not reasonably likely to result in a Company Material Adverse Effect.

     (b)  The Company Disclosure Schedule sets forth a complete list of each
contract or agreement to which the Company is a party or bound (i) with any
Affiliate of the Company, other than any agreements (A) which are or have been
fully performed and under which the Company has no continuing right, liability
or obligation, (B) that are otherwise disclosed on the Company Disclosure
Schedule and marked with a footnote indicating that it is a contract or
agreement with an Affiliate of the Company or (C) Stockholder Agreements, or
(ii) that includes any non-competition or similar provision imposing any
restrictions or undertakings on the Company. To the Company's Knowledge, none of
the contracts or agreements referred to in the foregoing clause (ii) would
preclude the Company or the Surviving Company from engaging in any of its
current activities or any of the Company's or the Surviving Company's planned


                                       17
<PAGE>   23


activities. Copies of all the agreements, contracts and arrangements set forth
in the Company Disclosure Schedule have heretofore been made available to the
Companies and such copies are accurate and complete.

     3.12 LITIGATION. There is no Litigation against the Company pending or as
to which the Company has received any written notice of assertion.

     3.13 ENVIRONMENTAL MATTERS.

     (a)  Except for such matters that, individually or in the aggregate, are
not reasonably likely to have a Company Material Adverse Effect: (i) the Company
has complied with all applicable Environmental Laws (as defined in Section
3.13(b)); (ii) the properties currently owned or operated by the Company
(including soils, groundwater, surface water, buildings or other structures) are
not contaminated with any Hazardous Substances (as defined in Section 3.13(c));
(iii) the properties formerly owned or operated by the Company were not
contaminated with Hazardous Substances during the period of ownership or
operation by the Company; (iv) the Company is not subject to liability for any
Hazardous Substance disposal or contamination on the property of any third
party; (v) the Company has not released any Hazardous Substance; (vi) the
Company has not received any notice, demand, letter, claim or request for
information alleging that the Company may be in violation of, liable under or
have obligations under any Environmental Law; (vii) the Company is not subject
to any orders, decrees, injunctions or other arrangements with any Governmental
Authority or any indemnity or other agreement with any third party relating to
liability under any Environmental Law or relating to Hazardous Substances; and
(viii) there are no circumstances or conditions involving the Company that could
reasonably be expected to result in any claims, liability, obligations,
investigations, costs or restrictions on the ownership, use or transfer of any
property of the Company pursuant to any Environmental Law.

     (b)  As used herein, the term "Environmental Law" means any federal, state,
local or foreign law, regulation, order, decree, permit, authorization, opinion,
common law or agency requirement relating to: (i) the protection, investigation
or restoration of the environment, health and safety, or natural resources, (ii)
the handling, use, presence, disposal, release or threatened release of any
Hazardous Substance or (iii) noise, odor, wetlands, pollution, contamination or
any injury or threat of injury to persons or property.

     (c)  As used herein, the term "Hazardous Substance" means any substance
that is: (i) listed, classified, regulated or which falls within the definition
of a "hazardous substance" or "hazardous material" pursuant to any Environmental
Law; (ii) any petroleum product or by-product, asbestos-containing material,
lead-containing paint or plumbing, polychlorinated biphenyls, radioactive
materials or radon; or (iii) any other substance which is the subject of
regulatory action by any Governmental Authority pursuant to any Environmental
Law.

     3.14 EMPLOYEE BENEFIT PLANS.

     (a)  The Company has listed in Section 3.14 of the Company Disclosure
Schedule all employee benefit plans (as defined in Section 3(3) of the Employee
Retirement Income Security Act of 1974, as amended ("ERISA")) and all bonus,
stock option, stock purchase, incentive,


                                       18
<PAGE>   24


deferred compensation, supplemental retirement, severance and other similar
employee benefit plans, and all unexpired severance agreements, written or
otherwise, for the benefit of, or relating to, any current or former employee of
the Company or any trade or business (whether or not incorporated) which is or
was ever a member of a controlled group of corporations or which is or was ever
under common control with the Company (an "ERISA Affiliate") within the meaning
of Section 414 of the Code (together, the "Company Employee Plans").

     (b)  With respect to each Company Employee Plan, the Company has furnished
to each of the other Companies a true and correct copy of (i) the most recent
annual report (Form 5500) filed with the IRS, (ii) such Company Employee Plan,
(iii) each trust agreement and group annuity contract, if any, relating to such
Company Employee Plan and (iv) the most recent reports regarding the
satisfaction of the nondiscrimination requirements of Sections 410(b), 401(k)
and 401(m) of the Code.

     (c)  With respect to the Company Employee Plans, no event has occurred, and
to the Knowledge of the Company, there exists no condition or set of
circumstances in connection with which the Company or any ERISA Affiliate could
be subject to any liability that is reasonably likely, individually or in the
aggregate, to have a Company Material Adverse Effect under ERISA, the Code or
any other applicable law. The transactions contemplated herein shall not
constitute a prohibited transaction (as defined in Section 4975 of the Code) or
in any way reasonably be expected to subject the Company to any liability that
in the aggregate would have a Company Material Adverse Effect.

     (d)  With respect to the Company Employee Plans, there are no funded
benefit obligations for which contributions have not been made or properly
accrued and there are no unfunded benefit obligations which have not been
accounted for by reserves, or otherwise properly footnoted in accordance with
generally accepted accounting principles, on the financial statements of the
Company, which obligations are reasonably likely, individually or in the
aggregate, to have a Company Material Adverse Effect.

     (e)  Neither the Company nor any ERISA Affiliate has (i) ever maintained a
Company Employee Benefit Plan which was ever subject to Title IV of ERISA or
Section 412 of the Code or (ii) ever been obligated to contribute to a
multiemployer plan (as defined in Section 4001(a)(3) of ERISA).

     (f)  Except as provided for in this Agreement, the Company is not a party
to any oral or written (i) agreement with any officer or other key employee of
the Company, the benefits of which are contingent, or the terms of which are
materially altered, upon the occurrence of a transaction involving the Company
of the nature contemplated by this Agreement, (ii) agreement with any employee
of the Company providing any term of employment or compensation guarantee
extending for a period longer than one year from the date hereof and for the
payment of compensation in excess of $50,000 per annum, or (iii) agreement or
plan, including any stock option plan, stock appreciation right plan, restricted
stock plan or stock purchase plan, any of the benefits of which will be
increased, or the vesting of the benefits of which will be accelerated, by the
occurrence of any of the transactions contemplated by this Agreement or the
value of any of the benefits of which will be calculated on the basis of any of
the transactions contemplated by this Agreement.


                                       19
<PAGE>   25


     (g)  Each Company Employee Plan intended to be qualified under Section
401(a) of the Code has either obtained from the IRS a favorable determination
letter as to its qualified status under the Code, including all amendments to
the Code effected by the Tax Reform Act of 1986 and subsequent legislation, or
has applied (or has time remaining in which to apply) to the IRS for such a
determination letter prior to the expiration of the requisite period under
applicable Treasury Regulations or IRS pronouncements in which to apply for such
determination letter and to make any amendments necessary to obtain a favorable
determination or has been established under a standardized prototype plan for
which an IRS opinion letter has been obtained by the plan sponsor and is valid
as to the adopting employer. The Company has furnished or made available to each
other Company a copy of the most recent IRS determination or opinion with
respect to each such Company Employee Plan and nothing has occurred since the
inception of each such Company Employee Plan which could reasonably be expected
to cause the loss of the tax-qualified status of any Company Employee Plan
subject to Section 401(a) of the Code.

     (h)  None of the Company Employee Plans promises or provides retiree
medical or other retiree welfare benefits to any person, except as required by
applicable law.

     3.15 COMPLIANCE WITH LAWS. The Company has complied with, is not in
violation of, and has not received any notice alleging any violation with
respect to, any foreign, federal, state or local statute, law or regulation with
respect to the conduct of its business, or the ownership or operation of its
properties or assets, except for failures to comply or violations which,
individually or in the aggregate, have not had and are not reasonably likely to
have a Company Material Adverse Effect.

     3.16 CERTAIN REGULATORY MATTERS.

     (a)  Section 3.16 of the Company Disclosure Schedule sets forth a complete
and accurate list of any written communications between the Company, on the one
hand, and the FDA or any other Governmental Authority on the other hand that
describe matters that could have a material adverse effect on the Company's
currently projected sales or revenues attributable to any contemplated compound,
product or product line of the Company. The Company has made available to both
of the other Companies copies of all such documents, as well as copies of all
complaints and other information required to be maintained by the Company
pursuant to the United States Federal Food, Drug and Cosmetic Act and
Comprehensive Drug Abuse Prevention and Control Act of 1970 and the
corresponding laws of jurisdictions other than the United States.

     (b)  The Company has filed with the FDA and all applicable state and local
regulatory bodies for and received approval of all registrations, applications,
licenses, requests for exemptions, permits and other regulatory authorizations
necessary to conduct the business of the Company as currently conducted, the
absence of which would, individually or in the aggregate, be reasonably likely
to have a Company Material Adverse Effect. The Company is, and at all relevant
times has been, in compliance in all material respects with all such
registrations, applications, licenses, requests for exemptions, permits and
other regulatory authorizations. To the Company's Knowledge, any third party
which is a manufacturer for the Company is, and at all relevant times has been,
in compliance in all material respects with all such registrations,


                                       20
<PAGE>   26


applications, licenses, requests for exemptions, permits and other regulatory
authorizations insofar as the same pertain to the manufacture of products for
the Company. The Company is, and at all relevant times has been, in compliance
in all material respect with all material FDA, state and local rules,
regulations, guidelines and policies, including, but not limited to, material
FDA, state and local rules, regulations and policies relating to good
manufacturing practice ("GMP") and good laboratory practice ("GLP"); and the
Company has no reason to believe that any party granting any such registration,
application, license, request for exemption, permit or other authorization is
considering limiting, suspending or revoking the same and knows of no basis for
any such limitation, suspension or revocation.

     3.17 TAX MATTERS. To its Knowledge, after consulting with its independent
auditors, neither the Company nor any of its Affiliates has taken or agreed to
take any action which would prevent the Merger from constituting a transaction
qualifying as a reorganization under 368(a) of the Code.

     3.18 REGISTRATION STATEMENT; PROXY STATEMENT/PROSPECTUS. The information to
be supplied by the Company for inclusion in the registration statement on Form
S-4 pursuant to which shares of Surviving Company Common Stock issued in the
Merger will be registered under the Securities Act (the "Registration
Statement"), shall not at the time the Registration Statement is declared
effective by the SEC contain any untrue statement of a material fact or omit to
state any material fact required to be stated in the Registration Statement or
necessary in order to make the statements in the Registration Statement not
misleading. The information to be supplied by the Company for inclusion in the
joint proxy statement/prospectus (the "Joint Proxy Statement") to be sent to the
stockholders of the Companies in connection with the meetings of the Companies'
stockholders to consider this Agreement and the Merger (the "Company Meetings")
shall not, on the date the Joint Proxy Statement is first mailed to stockholders
of the Companies, at the time of the Company Meetings, or at the Effective Time,
contain any statement which, at such time and in light of the circumstances
under which it shall be made, is false or misleading with respect to any
material fact, or omit to state any material fact necessary in order to make the
statements made in the Joint Proxy Statement not false or misleading; or omit to
state any material fact necessary to correct any statement in any earlier
communication with respect to the solicitation of proxies for the Company
Meetings which has become false or misleading. If at any time prior to the
Effective Time any event relating to the Company or any of its Affiliates,
officers or directors should be discovered by the Company which should be set
forth in an amendment to the Registration Statement or a supplement to the Joint
Proxy Statement, the Company shall promptly inform the other Companies.

     3.19 LABOR MATTERS. The Company is not a party to or otherwise bound by any
collective bargaining agreement, contract or other agreement or understanding
with a labor union or labor organization. The Company is not the subject of any
proceeding asserting that the Company has committed an unfair labor practice or
is seeking to compel it to bargain with any labor union or labor organization or
that, individually or in the aggregate, is reasonably likely to have a Company
Material Adverse Effect, nor is there pending or, to the Knowledge of the
Company, threatened, any labor strike, dispute, walkout, work stoppage,
slow-down or lockout involving the Company that, individually or in the
aggregate, is reasonably likely to have a Company Material Adverse Effect.


                                       21
<PAGE>   27


     3.20 INSURANCE. All fire and casualty, general liability, business
interruption, product liability, clinical trial and sprinkler and water damage
insurance policies maintained by the Company are with reputable insurance
carriers, provide full and adequate coverage for all normal risks incident to
the business of the Company and its properties and assets, and are in character
and amount at least equivalent to that carried by persons engaged in similar
businesses and subject to the same or similar perils or hazards, except for any
such failures to maintain insurance policies that, individually or in the
aggregate, are not reasonably likely to have a Company Material Adverse Effect.
The Company Disclosure Schedule sets forth the insurance coverages maintained by
the Company and a history of any claims paid.

     3.21 NO EXISTING DISCUSSIONS. As of the date hereof, the Company is not
engaged, directly or indirectly, in any discussions or negotiations with any
other party with respect to an Acquisition Proposal (as defined in Section 6.1).

     3.22 OPINION OF FINANCIAL ADVISOR. The financial advisor of each of
Creative and Ontogeny has delivered to such Company an opinion dated the date of
this Agreement to the effect, as of such date, that the applicable Exchange
Ratio is fair to the holders such Company's capital stock from a financial point
of view, and such Company has furnished a copy of such opinion to the other
Companies.

     3.23 SECTION 203 OF THE DGCL NOT APPLICABLE. The Board of Directors of each
of Creative and Ontogeny has taken all actions, if any, necessary so that the
restrictions contained in Section 203 of the DGCL applicable to a "business
combination" (as defined in Section 203) will not apply to the execution,
delivery or performance of this Agreement or the Stockholder Agreements or the
consummation of the Merger or the other transactions contemplated by this
Agreement or the Stockholder Agreements.

     3.24 NO BROKERS. Except with respect to Chase H&Q (in the case of
Creative), Pacific Growth Equities, Inc. (in the case of Reprogenesis) and SG
Cowen Securities Corporation (in the case of Ontogeny), the Company has no
contract, arrangement or understanding with any broker, finder, agent, financial
advisor or other intermediary with respect to the transactions contemplated by
this Agreement. Each Company has provided to each other Company a copy of such
Company's financial advisor contract.

     3.25 STOCKHOLDER RIGHTS.

     (a)  Other than as set forth in Section 3.2 of the Company Disclosure
Schedule, there are no outstanding securities, options, warrants, calls, rights,
commitments, agreements, arrangements, obligations or undertakings of any kind
(contingent or otherwise) to which the Company is a party or by which it is
bound that will obligate or require the Surviving Company after the Merger to
(i) issue, deliver or sell, or cause to be issued, delivered or sold, shares of
capital stock or other voting securities of the Surviving Company, (ii) issue,
grant, extend or enter into any such security, option, warrant, call, right,
commitment, agreement, arrangement or undertaking or (iii) repurchase, redeem or
otherwise acquire any shares of capital stock (or options to acquire any such
shares) of the Surviving Company.


                                       22
<PAGE>   28


     (b)  Other than as set forth in Section 3.2 of the Company Disclosure
Schedule, there are no agreements, arrangements, obligations or commitments of
any character (contingent or otherwise) pursuant to which any Person is or may
be entitled (A) to cause the Surviving Company to file a registration statement
under the Securities Act or which will otherwise relate to the registration of
any securities of the Surviving Company or (B) to preemptive rights or similar
contractual rights or arrangements with respect to the issuance or sale of
capital stock of the Surviving Company or any securities convertible into or
evidencing the right to subscribe for any shares of its capital stock.

     (c)  Other than the Stockholder Agreements, the Affiliate Agreements and
the Lock-up Agreements there are no voting trusts, proxies or other agreements,
arrangements, obligations or commitments of any character (contingent or
otherwise) to which the Company is a party or, to the Knowledge of the Company,
by which any of its stockholders is bound that, after the Merger, will (i)
relate to the voting of any shares of capital stock of the Surviving Company or
(ii) impose restrictions on or otherwise encumber the transfer of the capital
stock of the Surviving Company.

                                   ARTICLE IV

                     REPRESENTATIONS AND WARRANTIES OF CURIS

     Curis hereby represents and warrants to each Company that the statements
contained in this Article IV are true and correct with respect to it, except as
set forth herein or in the disclosure schedule attached by Curis to this
Agreement (the "Curis Disclosure Schedule"). The Curis Disclosure Schedule shall
be arranged in sections corresponding to the numbered and lettered sections
contained in this Article IV, and the disclosure in any section shall qualify
other sections in this Article IV only the extent that it is reasonably apparent
from a reading of such disclosure that it also qualifies or applies to such
other sections.

     4.1  ORGANIZATION OF CURIS. Curis is a corporation duly organized, validly
existing and good standing under the laws of the State of Delaware. The
Certificate of Incorporation of Curis as in effect on the date of this Agreement
is attached as Exhibit D hereto (the "Curis Certificate of Incorporation").
Curis has all requisite corporate power to own, lease and operate its properties
and assets and to carry on the business as now being conducted, and is duly
qualified to do business and is in good standing as a foreign corporation in
each jurisdiction in which the failure to be so qualified, individually or in
the aggregate, would be reasonably likely to have a material adverse effect on
the business, properties, financial condition, results of operations or
prospects of Curis or to have a material adverse effect on the ability of Curis
to consummate the transactions contemplated by this Agreement (a "Curis Material
Adverse Effect"). Curis does not directly or indirectly own any equity or
similar interest in, or any interest convertible into or exchangeable or
exercisable for, any corporation, partnership, joint venture or other business
association or entity.

     4.2  CURIS' CAPITAL STRUCTURE.

     (a)  The authorized capital stock of Curis consists of one hundred
twenty-five million shares of Curis Common Stock and twenty million shares, par
value $.01 per share, of


                                       23
<PAGE>   29


undesignated preferred stock of Curis ("Curis Preferred Stock"). As of the date
of this Agreement, there are 300 shares of Curis Common Stock issued and
outstanding, 100 shares of which are each owned by Creative, Ontogeny and
Reprogenesis, and no shares of which are held in the treasury of Curis. There
are no shares of Curis Preferred Stock issued and outstanding or held in the
treasury of Curis. All of such shares of Curis Common Stock are duly authorized,
validly issued, fully-paid and non-assessable, were not issued in violation of
any purchase option, call option, right of first refusal, preemptive right,
subscription right or any similar right under the DGCL, Curis's Certificate of
Incorporation or By-laws or any agreement to which Curis is a party or is
otherwise bound.

     (b)  There are no options, warrants, equity securities, calls, rights,
commitments or agreements of any character to which Curis is a party or by which
it is bound obligating Curis to issue, deliver or sell, or cause to be issued,
delivered or sold, shares of capital stock of or other equity interests in
Curis. To the Knowledge of Curis, other than as provided in this Agreement,
there are no voting trusts, proxies or other voting agreements or understandings
with respect to the shares of capital stock of or other equity interests in
Curis.

     (c)  Curis does not (i) own of record or beneficially, directly or
indirectly, (A) any shares of capital stock or securities convertible into
capital stock of any other corporation or (B) any participating interest in any
partnership, limited liability company, joint venture or other non-corporate
business enterprise or (ii) control, directly or indirectly, any other entity.

     4.3  AUTHORITY; NO CONFLICT; REQUIRED FILINGS AND CONSENTS.

     (a)  Curis has all requisite power and authority to enter into this
Agreement and to consummate the transactions contemplated by this Agreement. The
execution and delivery of this Agreement and the consummation of the
transactions contemplated by this Agreement by Curis have been duly authorized
by all the necessary corporate action on the part of Curis, subject only to the
approval of the Merger by Curis' stockholders under the DGCL. This Agreement has
been duly executed and delivered by Curis and constitutes the valid and binding
obligation of Curis, enforceable in accordance with its terms, subject to the
Bankruptcy and Equity Exception.

     (b)  The execution and delivery of this Agreement by Curis does not, and
the consummation of the transactions contemplated by this Agreement will not,
(i) conflict with, or result in any violation or breach of, any provision of the
Certificate of Incorporation or By-laws of Curis, (ii) result in any violation
or breach of, or constitute (with or without notice or lapse of time, or both) a
default (or give rise to a right of termination, cancellation or acceleration of
any obligation or loss of any material benefit) under, or require a consent or
waiver under, or constitute a change in control under, any of the terms,
conditions or provisions of any note, bond mortgage, indenture, lease, license,
contract or other agreement, instrument or obligation to which Curis is a party
or by which it or any of its properties or assets may be bound, or (iii)
conflict with or violate any permit, concession, franchise, license, judgment,
order, decree, statute, law, ordinance, rule or regulation applicable to Curis
or by which it or any of its properties or assets may be bound, except in the
case of (ii) and (iii) for any such conflicts, violations, defaults,
terminations, cancellations or accelerations which are not, individually or in
the aggregate, reasonably likely to have a Curis Material Adverse Effect.


                                       24
<PAGE>   30


     (c)  No consent, approval, license, permit, order or authorization of, or
registration, declaration or filing with, any Governmental Authority is required
by or with respect to Curis in connection with the execution and delivery of
this Agreement or the consummation of the transactions contemplated hereby,
except for (i) the filing of a pre-merger notification report under the HSR Act,
(ii) the filing of the Certificate of Merger with the Delaware Secretary of
State, (iii) the filing of the Articles of Merger with the Secretary of State of
the State of Texas and the issuance of a certificate of merger by the Secretary
of State of the State of Texas, (iv) the filing of the Registration Statement
with the SEC and the effectiveness thereof, (v) the registration of the
Surviving Company Common Stock under the Exchange Act, (vi) such, consents,
approvals, orders, authorizations, registrations, declarations and filings as
may be required under applicable state securities laws and (vii) such other
consents, licenses, permits, orders, authorizations, filings, approvals and
registrations which, if not obtained or made, would not be reasonably likely,
individually or in the aggregate, to have a Curis Material Adverse Effect.

     4.4  CONTINUITY OF BUSINESS ENTERPRISE; REORGANIZATION CLASSIFICATION.
Curis hereby represents and warrants to each Company and to the stockholders of
each Company (which representation and warranty shall survive the Closing) that
the Merger will satisfy the continuity of business enterprise test of Treasury
Regulation Section 1.368-1(d).

                                    ARTICLE V

                     CONDUCT OF BUSINESS PENDING THE MERGER

     5.1  CONDUCT OF BUSINESS BY COMPANY PENDING THE MERGER. Each Company
covenants and agrees with the other Parties that, between the date hereof and
the Effective Time, except as expressly required or permitted by this Agreement
or unless each other Party shall otherwise agree in writing, such Company shall
conduct and shall cause the businesses of each of its Subsidiaries to be
conducted only in, and such Company and its Subsidiaries shall not take any
action except in, the ordinary course of business and in a manner consistent
with past practice. Each Company shall use its commercially reasonable best
efforts to preserve intact the business organization and assets of such Company
and each of its Subsidiaries, and to operate, and cause each of its Subsidiaries
to operate, according to plans and budgets provided to each other Party, to keep
available the services of the present officers, employees and consultants of
such Company and each of its Subsidiaries and, except as set forth in Section
5.1 of the Company Disclosure Schedule, to maintain in effect Company Material
Contracts and to preserve the present relationships of the Company and each of
its Subsidiaries with licensors, licensees, sponsors, customers, suppliers,
consultants and other Persons with which the Company or any of its Subsidiaries
has business relations. By way of amplification and not limitation, except as
expressly permitted by this Agreement or except as set forth in the Company
Disclosure Schedule, neither the Companies nor any of their respective
Subsidiaries shall, between the date hereof and the Effective Time, directly or
indirectly do, or propose to do, any of the following without the prior written
consent of each other Party:


                                       25
<PAGE>   31


     (a)  amend or otherwise change the Certificate or Articles of Incorporation
or By-laws or equivalent organizational document of the Company or any of its
Subsidiaries or alter through merger, liquidation, reorganization, restructuring
or in any other fashion the corporate structure or ownership of Company or any
of its Subsidiaries;

     (b)  issue, sell, transfer, pledge, dispose of or encumber, or authorize
the issuance, sale, transfer, pledge, disposition or encumbrance of, any shares
of capital stock of any class, or any options, warrants, convertible securities
or other rights of any kind to acquire any shares of capital stock, or any other
ownership interest of the Company or any of its Subsidiaries (except for the
issuance of Company Common Stock upon the exercise of Company Options or Company
Warrants outstanding on the date hereof or upon the conversion of any
convertible securities outstanding on the date hereof); or sell, transfer,
pledge, dispose of or encumber, or authorize the sale, transfer, pledge,
disposition or encumbrance, of any assets of the Company or any of its
Subsidiaries (except for sales of assets in the ordinary course of business and
in a manner consistent with past practice) or redeem, purchase or otherwise
acquire, directly or indirectly, any of the capital stock of the Company or
interest in or securities of any Subsidiary;

     (c)  declare, set aside or pay any dividend or other distribution (whether
in cash, stock or property or any combination thereof) in respect of any of its
capital stock (except that a wholly owned Subsidiary of any Company may declare
and pay a dividend to its parent); split, combine or reclassify any of its
capital stock or issue or authorize or propose the issuance of any other
securities in respect of, in lieu of or in substitution for shares of its
capital stock or amend the terms of, repurchase, redeem or otherwise acquire, or
permit any Subsidiary to repurchase, redeem or otherwise acquire, any of its
securities or any securities of its Subsidiaries, or propose to do any of the
foregoing;

     (d)  sell, transfer, lease, out-license, out-sublicense, mortgage, pledge,
dispose of, encumber, grant or otherwise dispose of any Intellectual Property
Rights, or amend or modify in any material way any existing agreements with
respect to any Intellectual Property Rights, except for (i) non-exclusive
licenses granted pursuant to material transfer agreements entered into in the
ordinary course of business consistent with past practice and (ii) non-exclusive
research licenses granted as part of a research agreement that is otherwise
permitted under this Agreement;

     (e)  acquire (by merger, consolidation, acquisition of stock or assets or
otherwise) any corporation, limited liability company, partnership, joint
venture or other business organization or division thereof; incur any
indebtedness for borrowed money or issue any debt securities or assume,
guarantee or endorse or otherwise as an accommodation become responsible for,
the obligations of any Person, or make any loans, advances or enter into any
financial commitments, except in the ordinary course of business consistent with
past practice and as otherwise permitted under any loan or credit agreement to
which the Company is a party; authorize any capital expenditures which are, in
the aggregate, in excess of $100,000 for the Company and its Subsidiaries taken
as a whole; or enter into or amend in any material respect any contract,
agreement, commitment or arrangement with respect to any of the matters set
forth in this Section 5.1(e);


                                       26
<PAGE>   32


     (f)  hire any employee or consultant; terminate any employee or consultant,
except in the ordinary course of business consistent with past practice;
increase the compensation (including, without limitation, bonus) payable or to
become payable to its officers or employees, except for increases in salary or
wages of employees of the Company or its Subsidiaries who are not officers of
the Company in the ordinary course of business consistent with past practices,
or grant any severance or termination pay or stock options to, or enter into any
employment or severance agreement with any director, officer or other employee
of the Company or any of its Subsidiaries, or establish, adopt, enter into or
amend any collective bargaining, bonus, profit sharing, thrift, compensation,
stock option, restricted stock, pension, retirement, deferred compensation,
employment, termination, severance or other plan, agreement, trust, fund, policy
or arrangement for the benefit of any current or former directors, officers or
employees;

     (g)  change any accounting policies or procedures (including procedures
with respect to reserves, revenue recognition, payments of accounts payable and
collection of accounts receivable) unless required by statutory accounting
principles or GAAP;

     (h)  create, incur, suffer to exist or assume any Lien on any of their
material assets other than Liens outstanding on the date hereof;

     (i)  other than in the ordinary course of business consistent with past
practice, (i) enter into any Company Material Contract, (ii) modify, amend or
transfer in any material respect or terminate any Company Material Contract or
waive, release or assign any material rights or claims thereto or thereunder or
(iii) enter into or extend any lease with respect to real property with any
third party;

     (j)  make any Tax election or settle or compromise any federal, state,
local or foreign income Tax liability or agree to an extension of a statute of
limitations;

     (k)  settle any material Litigation or waive, assign or release any
material rights or claims except, in the case of Litigation, any Litigation
which settlement would not (i) impose either material restrictions on the
conduct of the Company's business or any of its Subsidiaries or (ii) for any
individual Litigation item settled, exceed $50,000 in cost or value to the
Company or any of its Subsidiaries;

     (l)  pay, discharge or satisfy any liabilities or obligations (absolute,
accrued, asserted or unasserted, contingent or otherwise), except in the
ordinary course of business consistent with past practice in an amount or value
not exceeding $100,000 in any instance or series of related instances or
$250,000 in the aggregate or in accordance with their terms as in effect as of
the date hereof;

     (m)  engage in any transaction, or enter into any agreement, arrangement,
or understanding with, directly or indirectly, any Affiliate, other than those
contemplated pursuant to the terms of this Agreement and those existing as of
the date hereof which are listed in the Company Disclosure Schedule;

     (n)  fail to renew or maintain in full force and effect all insurance
policies, as the case may be, currently in effect or fail to pay any insurance
premiums thereon; and


                                       27
<PAGE>   33


     (o)  authorize, recommend, propose or announce an intention to do any of
the foregoing, or agree or enter into any agreement, contract commitment or
arrangement to do any of the foregoing.

     5.2  COOPERATION. Subject to compliance with applicable law, from the date
hereof until the Effective Time, each Company shall, and shall cause each of
their respective Subsidiaries to, make its officers available to confer on a
regular and frequent basis with one or more representatives of the other Parties
at reasonable times and upon reasonable advance notice to report on the general
status of ongoing operations and shall promptly provide the other Parties or
their counsel with copies of all filings made by such party with any
Governmental Authority in connection with this Agreement, the Merger and the
transactions contemplated hereby and thereby.

     5.3  CONFIDENTIALITY. The parties acknowledge that each of (i) the
Non-Disclosure Agreement dated June 11, 1998 between Creative and Ontogeny (as
amended, the "CO Agreement"), (ii) the Non-Disclosure Agreement between Creative
and Reprogenesis (as amended, the "CR Agreement") (iii) the Non-Disclosure
Agreement between Ontogeny and Reprogenesis (the "OR Agreement") and (iv) the
Agreement Regarding Disclosure of Confidential Documents and Information dated
January 10, 2000 by and among the Companies (the "IP NDA" and, collectively with
the CO Agreement, the CR Agreement and the OR Agreement, the "Confidentiality
Agreements"), shall continue in full force and effect in accordance with its
terms.

     5.4  CURIS CERTIFICATE OF INCORPORATION. Curis covenants and agrees with
the other Parties that, between the date hereof and the Effective Time, Curis
shall not amend or modify the Curis Certificate of Incorporation without the
prior written consent of each Company.

                                   ARTICLE VI

                         SOLICITATION OF OTHER PROPOSALS

     6.1  SOLICITATION OF OTHER PROPOSALS.

     (a)  From the date hereof until the earlier of the Effective Time or the
termination of this Agreement in accordance with its terms, no Company shall,
nor shall any Company permit any of their respective Subsidiaries or any of
their respective officers, directors, employees, investment bankers, attorneys
or other representatives, advisors or agents (collectively, the
"Representatives") to, and each Company shall use its best efforts to cause each
of its respective non-officer and non-director Affiliates not to, directly or
indirectly, (i) solicit, facilitate, initiate or encourage, or take any action
to solicit, facilitate, initiate or encourage, the making of any proposal or
offer that constitutes an Acquisition Proposal or the making of any inquiries
concerning an Acquisition Proposal or (ii) participate or engage in discussions
or negotiations with, or provide any information to, any Person concerning an
Acquisition Proposal or which might reasonably be expected to lead to an
Acquisition Proposal; PROVIDED that, if such Company has not breached this
Section 6.1(a), nothing contained in this Agreement shall prevent such Company
or its Board of Directors, prior to the vote of the stockholders of such Company
for approval of this Agreement and the Merger, from furnishing non-public
information to, or


                                       28
<PAGE>   34


entering into discussions or negotiations with, any Person (other than another
Company) in response to an unsolicited bona fide written Acquisition Proposal by
such Person if and only to the extent that (A) the Board of Directors of such
Company believes in good faith (after consultation with its financial advisor)
that such Acquisition Proposal is reasonably capable of being completed on the
terms proposed and would, if so consummated, result in a Superior Proposal (as
defined below), (B) such Company's Board of Directors determines in good faith
after consultation with outside legal counsel that such action is necessary for
such Board of Directors to comply with its fiduciary duties to stockholders
under applicable law, (C) prior to furnishing such non-public information to, or
entering into discussions or negotiations with, such Person, such Board of
Directors receives from such Person an executed confidentiality agreement with
terms no more favorable to such Person than those contained in the
Confidentiality Agreements and (D) prior to furnishing such non-public
information to, or entering into discussions or negotiations with, such Person,
such Company has complied with the provisions of Section 6.1(c). Without
limiting the foregoing, it is understood that any violation of the restrictions
set forth in this Section 6.1(a) by any Representative of a Company or its
Subsidiaries or any non-officer and non-director Affiliate of such Company,
whether or not acting on behalf of such Company or any of its Subsidiaries,
shall be deemed to be a breach of this Section 6.1(a) by such Company.

     For purposes of this Agreement, the term "Acquisition Proposal" shall mean
any inquiry, proposal or offer after the date of this Agreement from any Person
relating to:

               (1)  any merger, consolidation, recapitalization, liquidation or
     other direct or indirect business combination, involving a Company or any
     of its Subsidiaries or the issuance or acquisition of shares of capital
     stock or other equity securities of a Company or any of its Subsidiaries
     (excluding the issuance of Company Common Stock upon the exercise of
     Company Options or Company Warrants outstanding on the date hereof or upon
     the conversion of any convertible securities outstanding on the date
     hereof) or any tender or exchange offer that if consummated would result in
     any Person, together with all Affiliates thereof, beneficially owning
     shares of capital stock or other equity securities of a Company or any of
     its Subsidiaries; provided, however, that if any pharmaceutical or
     biopharmaceutical company engaged in discussions with a Company regarding
     the licensing of Intellectual Property Rights makes, in connection with and
     relating to such discussions, an unsolicited inquiry, proposal or offer
     regarding the acquisition of shares of capital stock representing 5% or
     less of the outstanding capital stock of such Company, such an inquiry,
     proposal or offer shall not constitute an Acquisition Proposal if, and only
     if, such inquiry, proposal or offer is disclosed in reasonable detail in
     writing to the other Companies within three (3) Business Days and the Chief
     Executive Officers of such other Companies agree that such inquiry,
     proposal or offer does not constitute an Acquisition Proposal, with written
     confirmation to follow within three (3) Business Days of such agreement; or

               (2)  other than as set forth in Section 6.1 of the Company
     Disclosure Schedule or as permitted pursuant to Section 5.1(d), the sale,
     lease, exchange, license (whether exclusive or not), or any other
     disposition of any significant portion of a material Intellectual Property
     Right, or any significant portion of the business or other assets of a
     Company or any its Subsidiaries, or any other transaction, the consummation


                                       29
<PAGE>   35


     of which sale, lease, exchange, license, disposition or transaction could
     reasonably be expected to impede, interfere with, prevent or materially
     delay the consummation of the transactions contemplated hereby or which
     would reasonably be expected to diminish significantly the benefits to each
     other Company and Curis of the transactions contemplated hereby; provided,
     however, that if any pharmaceutical or biopharmaceutical company makes an
     inquiry, proposal or offer regarding any such sale, lease, exchange,
     license, disposition or transaction, such inquiry, proposal or offer shall
     not constitute an Acquisition Proposal if, and only if, such inquiry,
     proposal or offer is disclosed in reasonable detail in writing to the other
     Companies within three (3) Business Days and the Chief Executive Officers
     of such other Companies agree that such inquiry, proposal or offer does not
     constitute an Acquisition Proposal, with written confirmation to follow
     within three (3) Business Days of such agreement.

Each Party shall immediately cease and cause to be terminated and shall cause
its respective Representatives (and shall use its best efforts to cause its
non-officer and non-director Affiliates) to terminate all existing discussions
or negotiations with any Persons conducted heretofore with respect to, or that
could reasonably be expected to lead to, an Acquisition Proposal. Each Party
shall promptly notify its respective Representatives and non-officer and
non-director Affiliates of its obligations under this Section 6.1(a).

     (b)  Except as permitted by this Section 6.1(b), neither the Board of
Directors of each Company nor any committee thereof shall:

               (1)  approve or recommend, or publicly (or in a manner reasonably
     likely to become public) propose to approve or recommend, any Acquisition
     Proposal other than the Merger,

               (2)  withdraw or modify or publicly (or in a manner reasonably
     likely to become public) propose to withdraw or modify in a manner adverse
     to each other Party its approval or, except as provided below,
     recommendation (or the approval or, except as provided below,
     recommendation of any committee of such Board of Directors) of the Merger,
     this Agreement or the transactions contemplated hereby,

               (3)  upon a request by any of the other Parties to reaffirm its
     approval or, except as provided below, recommendation of this Agreement or
     the Merger, fail to do so within two (2) Business Days after such request
     is made,

               (4)  enter, or cause such Company or any its Subsidiaries to
     enter, into any letter of intent, agreement in principle, acquisition
     agreement or other similar agreement related to any Acquisition Proposal,
     or

               (5)  resolve or announce its intention to do any of the
     foregoing.

The immediately preceding sentence notwithstanding, in the event that prior to a
Company Meeting, the Board of Directors of such Company receives a Superior
Proposal, then the Board of Directors of such Company may, if such Company has
complied with the provisions of Section 6.1(a), (i) withdraw or modify, or
propose to withdraw or modify, in a manner adverse to the other Parties its
recommendation of the Merger, this Agreement or the transactions


                                       30
<PAGE>   36


contemplated hereby, or (ii) fail to reaffirm its recommendation of this
Agreement or the Merger after a request by the other Parties to do so; PROVIDED
that (A) such Board of Directors determines in good faith, after consultation
with its outside counsel that taking such action is required to satisfy the
fiduciary duties of such directors and (B) such Company furnishes the other
Parties five Business Days' prior written notice of the taking of such action
(which notice shall include a description of the material terms and conditions
of the Superior Proposal), during which time the other Parties may make, and
such Company shall consider, a counterproposal to such Superior Proposal.

For purposes of the Agreement, the term "Superior Proposal" means any BONA FIDE
proposal by a third party to acquire all or substantially all of the assets or
capital stock of a Company pursuant to a tender or exchange offer, a merger,
consolidation, a liquidation or dissolution, a recapitalization, a sale of its
assets or otherwise which is on terms which the Board of Directors of such
Company determines by a majority vote of its directors in their good faith
judgment to be more favorable to the stockholders of such Company than the
Merger (or any counterproposal made by the other Parties), after receiving the
written advice of the Company's independent financial advisor and after
consultation with its outside counsel, and after taking into account the terms
and conditions of such Superior Proposal and all other relevant factors relating
thereto, including, the timing of the closing thereof, the risk of
non-consummation, the ability of the Person making the Acquisition Proposal to
finance the transaction contemplated thereby and any required governmental or
other consents, filings and approvals.

     (c)  In addition to the other obligations of the Parties set forth in this
Section 6.1, the Parties shall immediately (and in any event within one day)
advise one another orally and in writing of any Acquisition Proposal, any
request for information with respect to any Acquisition Proposal, or any inquiry
with respect to or which could result in an Acquisition Proposal, and the
material terms and conditions of such Acquisition Proposal, request or inquiry
(including the identity of the Person making such Acquisition Proposal, request
or inquiry). The Parties shall inform one another on a prompt and current basis
of the status and content of any discussions regarding any Acquisition Proposal
with a third party and as promptly as practicable of any change in the price,
structure or form of the consideration or material terms of and conditions
regarding any Acquisition Proposal or of any other developments or circumstances
which could reasonably be expected to culminate in the taking of any of the
actions referred to in Section 6.1(b).

     (d)  Nothing in this Section 6.1 shall (i) permit a Company to terminate
this Agreement (except as specifically provided in Section 9.1 hereof), (ii)
permit a Company to enter into any agreement with respect to an Acquisition
Proposal during the term of this Agreement (it being agreed that during the term
of this Agreement, no Company shall enter into any agreement with any Person
that provides for, or in any way facilitates, an Acquisition Proposal (other
than a confidentiality agreement of the type referred to in clause (C) of
Section 6.1(a) above)) or (iii) affect any other obligation of each Company
under this Agreement.

     (e)  Nothing contained in this Section 6.1 shall prevent the Board of
Directors of a Company that is a Public Company from at anytime taking or
disclosing to its stockholders a position contemplated by Rule 14e-2 promulgated
under the Exchange Act; provided that no


                                       31
<PAGE>   37


Company or its Board of Directors shall, except to the extent permitted by
Section 6.1(b), propose to approve or recommend an Acquisition Proposal.

                                   ARTICLE VII

                              ADDITIONAL AGREEMENTS

     7.1  PROXY STATEMENT/PROSPECTUS; REGISTRATION STATEMENT.

     (a)  As promptly as practicable following the date of this Agreement, Curis
shall prepare and file with the SEC the Registration Statement on Form S-4, in
which the Joint Proxy Statement shall be included as a prospectus, and shall use
reasonable efforts to have the Registration Statement declared effective by the
SEC as promptly as practicable. Curis shall obtain and furnish the information
required to be included in the Registration Statement and, after consultation
with each Company respond promptly to any comments made by the SEC with respect
to the Registration Statement (which comments shall promptly be furnished to
each Company) and cause the prospectus included therein, including any amendment
or supplement thereto, to be mailed to the stockholders of each Company at the
earliest practicable date after the Registration Statement is declared effective
by the SEC, provided that no amendment or supplement to the Registration
Statement will be made by Curis without consultation with each Company and each
of their respective counsels. Curis shall also take any action required to be
taken under Blue Sky or other securities Laws in connection with the issuance of
Surviving Company Common Stock in the Merger.

     (b)  Each Company shall (i) as promptly as practicable following the date
hereof prepare a preliminary proxy or information statement relating to the
Merger and this Agreement, (ii) obtain and furnish the information required to
be included by the SEC in the Joint Proxy Statement, (iii) cause the Joint Proxy
Statement and the prospectus to be included in the Registration Statement,
including any amendment or supplement thereto, to be mailed to their respective
stockholders at the earliest practicable date after the Registration Statement
is declared effective by the SEC, and (iv) use all reasonable efforts to obtain
the necessary approval of the Merger and this Agreement by their stockholders.
No Company shall file with or supplementally provide to the SEC or mail to its
stockholders the Joint Proxy Statement or any amendment or supplement thereto
without the prior written consent of each other Company. Each Company shall
allow each other Company's full participation in the preparation of the Joint
Proxy Statement and any amendment or supplement thereto and shall consult with
each other Company and its advisors concerning any comments from the SEC with
respect thereto.

     (c)  Each Company shall include in the Joint Proxy Statement the
recommendation of its Board of Directors in favor of approval and adoption of
this Agreement and the Merger, except to the extent that the Board of Directors
of such Company shall have withdrawn or modified its recommendation of this
Agreement or the Merger as permitted by Section 6.1(b). Without limiting the
foregoing, each Company agrees that its obligation under Section 7.2 to duly
call, give notice of and hold its Company Meeting as soon as practicable
following the date upon which the Registration Statement becomes effective shall
not be affected by (i) the commencement, public proposal, public disclosure or
communication to such Company of any


                                       32
<PAGE>   38


Acquisition Proposal or (ii) the withdrawal or modification by the Board of
Directors of such Company of its approval or recommendation of this Agreement or
the Merger.

     (d)  The Parties shall, as promptly as practicable, make all necessary
filings with respect to the Merger under the Securities Act and the Exchange Act
and the rules and Regulations thereunder (including, without limitation,
registration of the Surviving Company Common Stock on a Form 8-A (the "Exchange
Act Registration Statement")) and under applicable Blue Sky or similar
securities laws, rules and Regulations, and shall use all reasonable efforts to
obtain required approvals and clearances with respect thereto.

     (e)  In the event that Curis is not permitted to include in the
Registration Statement all shares of Surviving Company Common Stock to be issued
as Merger Consideration ("Excluded Securities") then, as promptly as practicable
after the filing of the Registration Statement, Curis shall file and shall use
its commercially reasonable best efforts to have declared effective a "shelf"
registration statement pursuant to Rule 415 under the Securities Act for the
resale of the Excluded Securities and use its commercially reasonable best
efforts to keep such registration statement effective for a period of two (2)
years following the Effective Time or, if shorter, until (i) all Excluded
Securities have been sold pursuant to such registration statement or (ii) the
first date on which each holder of Excluded Securities may sell all of such
Excluded Securities held by such holder without registration pursuant to Rule
144 under the Securities Act within a three-month period.

     7.2  MEETINGS OF STOCKHOLDERS. Each Company shall promptly after the date
hereof take all action necessary in accordance with the provisions of the DGCL
or the TBCA and each of their Certificates or Articles of Incorporation and
By-laws, respectively, to duly call, give notice of and hold its Company Meeting
as soon as practicable following the date upon which the Registration Statement
becomes effective and shall consult with Curis in connection therewith. Once
such Company Meeting has been called and noticed, the Company shall not postpone
or adjourn (other than for the absence of a quorum and then only to a future
date agreed to by the other Parties) such Company Meeting without the consent of
each other Company. The Boards of Directors of each Company shall have declared
that this Agreement and the Merger is advisable and, subject to Section 6.1(b),
recommended that this Agreement and the Merger be approved and authorized by the
stockholders of such Company and include in the Registration Statement and Joint
Proxy Statement a copy of such recommendation; PROVIDED, that each Company,
through its Board of Directors, shall submit this Agreement and the Merger to
their respective stockholders whether or not such Board of Directors at any time
subsequent to making such recommendation takes any action permitted by Section
6.1(b). Each Company shall solicit from their respective stockholders proxies in
favor of the Merger and shall take all other action necessary or advisable to
secure the vote or consent of such stockholders required by the DGCL or the TBCA
to authorize the Merger; PROVIDED that this provision shall not prohibit the
Boards of Directors of the Companies from taking any action permitted by Section
6.1(b).

     7.3  ACCESS TO INFORMATION. Upon reasonable notice, each Company shall (and
shall cause each of its Subsidiaries to) afford to the other Parties' officers,
employees, accountants, counsel and other representatives, reasonable access,
during normal business hours during the period prior to the Effective Time, to
all its properties, books, contracts, commitments and records and, during such
period, each Company shall (and shall cause each of its Subsidiaries to) furnish
promptly to the other Parties (i) a copy of each report, schedule, registration
statement


                                       33
<PAGE>   39


and other document filed or received by it during such period pursuant to the
requirements of federal securities laws and (ii) all other information
concerning its business, properties and personnel as each other Party may
reasonably request. Unless otherwise required by law, each Party shall, and
shall cause its officers, employees, accountants, counsel and other
representatives or persons who have access to such information to, hold any such
information which is non-public in confidence in accordance with the
Confidentiality Agreements. No information or knowledge obtained in any
investigation pursuant to this Section 7.3 or otherwise shall affect or be
deemed to modify any representation or warranty contained in this Agreement or
the conditions to the obligations of the Parties to consummate the Merger.

     7.4  ALL REASONABLE EFFORTS; FURTHER ASSURANCES.

     (a)  Upon the terms and subject to the conditions set forth in this
Agreement, each Party shall use all reasonable efforts to take, or cause to be
taken, all appropriate actions, and do, or cause to be done, and to assist and
cooperate with the other Parties in doing, all things necessary, proper or
advisable to consummate and make effective, in the most expeditious manner
practicable, the Merger and the other transactions contemplated hereby. The
Parties shall use all reasonable efforts to:

               (i)  obtain all licenses, permits, consents, waivers, approvals,
     authorizations, qualifications or Orders (including all United States and
     foreign governmental and regulatory rulings and approvals), required to be
     obtained by each of them, or any of their respective Subsidiaries,
     respectively, and the Parties shall make all filings (including, without
     limitation, all filings with United States and foreign governmental or
     regulatory agencies) under applicable Law required in connection with the
     authorization, execution and delivery of this Agreement by them and the
     consummation by them of the transactions contemplated hereby and thereby,
     including the Merger (in connection with which the Parties will cooperate
     with each other in connection with the making of all such filings,
     including providing copies of all such documents to the non-filing party
     and its advisors prior to filings and, if requested, will accept all
     reasonable additions, deletions or changes suggested in connection
     therewith);

               (ii) furnish all information required for any application or
     other filing to be made pursuant to any applicable law or any applicable
     Regulations of any Governmental Authority (including all information
     required to be included in the Joint Proxy Statement or the Registration
     Statement) in connection with the transactions contemplated by this
     Agreement; and

               (iii) lift, rescind or mitigate the effects of any injunction,
     restraining order or other order adversely affecting the ability of any
     party hereto to consummate the transactions contemplated hereby and thereby
     and to prevent, with respect to any threatened injunction, restraining
     order or other Order, the issuance or entry thereof, PROVIDED that no Party
     shall be under any obligation to (x) make proposals, execute or carry out
     agreements or submit to Orders providing for the sale or other disposition
     or holding separate (through the establishment of a trust or otherwise) of
     any assets or categories of assets material (in nature or amount) to such
     Party or imposing or seeking to impose any material limitation on the
     ability of such Party to conduct its business or own such assets or (y)
     otherwise take any step


                                       34
<PAGE>   40


to avoid or eliminate any impediment which may be asserted under any Law
governing competition, monopolies or restrictive trade practices which, in the
reasonable judgment of such Party, might result in a limitation of the benefit
expected to be derived by Curis as a result of the transactions contemplated
hereby or might adversely affect the Parties as a whole. None of the Parties
hereto will take any action which results in any of the representations or
warranties made by such Party pursuant to Articles III or IV, as the case may
be, becoming untrue or inaccurate in any material respect.

     (b)  The Parties shall use all reasonable efforts to satisfy or cause to be
satisfied all of the conditions precedent that are set forth in Article VIII, as
applicable to each of them, and to cause the transactions contemplated by this
Agreement to be consummated. Each Party, at the reasonable request of another
Party, shall execute and deliver such other instruments and do and perform such
other reasonable acts and things as may be necessary or desirable for effecting
completely the consummation of this Agreement and the transactions contemplated
hereby.

     7.5  STOCK OPTIONS AND WARRANTS.

     (a)  At the Effective Time, each outstanding Company Stock Option under the
Company Stock Plans, whether vested or unvested, shall, in accordance with the
terms of such Company Stock Option and such Company Stock Plan, by virtue of the
Merger and without any action on the part of the holder thereof, become and
represent an option to acquire, on the same terms and conditions as were
applicable under such Company Stock Option, the same number of shares of
Surviving Company Common Stock as the holder of such Company Stock Option would
have been entitled to receive pursuant to the Merger had such holder exercised
such option in full immediately prior to the Effective Time (rounded downward to
the nearest whole number), at a price per share (rounded upward to the nearest
whole cent) equal to (i) the aggregate exercise price for shares of Company
Common Stock purchasable pursuant to such Company Stock Option immediately prior
to the Effective Time divided by (ii) the number of full shares of Surviving
Company Common Stock deemed purchasable pursuant to such Company Stock Option in
accordance with the foregoing.

     (b)  As soon as practicable after the Effective Time, the Surviving Company
shall deliver to the participants in Company Stock Plans appropriate notice
setting forth such participants' rights pursuant thereto and the grants pursuant
to Company Stock Plans shall continue in effect on the same terms and conditions
(subject to the adjustments required by this Section 7.5 after giving effect to
the Merger).

     (c)  Curis shall take all corporate action necessary to reserve for
issuance a sufficient number of shares of Surviving Company Common Stock for
delivery under the Company Stock Plans assumed in accordance with this Section
7.5. As soon as practicable after the Effective Time, and in any event within 30
days thereafter, the Surviving Company shall file one or more registration
statements on Form S-8 (or any successor or other appropriate forms) with
respect to the shares of Surviving Company Common Stock subject to such options
and shall use its commercially reasonable best efforts to maintain the
effectiveness of such registration statement or registration statements (and
maintain the current status of the prospectus or prospectuses contained therein)
for so long as such options remain outstanding.


                                       35
<PAGE>   41


     (d)  The Board of Directors of each Company (or Board committee
administering such plans) shall have approved, prior to the date of this
Agreement, and shall take, prior to or as of the Effective Time, all necessary
actions, if any, pursuant to and in accordance with the terms of the Company
Stock Plans and the instruments evidencing the Company Stock Options, to provide
for the conversion of the Company Stock Options into options to acquire
Surviving Company Common Stock in accordance with this Section 7.5, and to
provide that no consent of the holders of the Company Stock Options is required
in connection with such conversion.

     (e)  At the Effective Time, each outstanding Company Warrant (other than
any Company Warrant that by its terms otherwise expires by virtue of the Merger)
shall, in accordance with the terms of such Company Warrant, by virtue of the
Merger and without any action on the part of the holder thereof, become and
represent a warrant to acquire, on the same terms and conditions as were
applicable under such Company Warrant, the same number of shares of Surviving
Company Common Stock as the holder of such Company Warrant would have been
entitled to receive pursuant to the Merger (including with respect to the
treatment of fractional shares) had such holder exercised such Company Warrant
in full immediately prior to the Effective Time, at a price per share (rounded
upward to the nearest whole cent) equal to (i) the aggregate exercise price for
the shares of Company Common Stock purchasable pursuant to such Company Warrant
immediately prior to the Effective Time divided by (ii) the number of full
shares of Surviving Company Common Stock deemed purchasable pursuant to such
Company Warrant in accordance with the foregoing.

     (f)  The Board of Directors of each Company shall have approved, prior to
the date of this Agreement, and shall take, prior to or as of the Effective
Time, all necessary actions, pursuant to and in accordance with the terms of the
Company Warrants, to provide for the conversion of the Company Warrants into
warrants to acquire Surviving Company Common Stock in accordance with this
Section 7.5, and to provide that no consent of the holders of any Company
Warrant is required in connection with such conversion.

     (g)  Immediately prior to the Effective Time, the Subordinated Note of
Ontogeny payable to Atwill Holdings Limited (the "Ontogeny Convertible Note")
shall in accordance with the terms of the Ontogeny Convertible Note and the
Common Stock Purchase Agreement pursuant to which such Ontogeny Convertible Note
was issued, by virtue of the Merger and without any action on the part of the
holder thereof, become and represent (and Ontogeny will issue to the holder of
such note) an aggregate of 819,673 shares of Ontogeny Common Stock.

     7.6  NOTIFICATION OF CERTAIN MATTERS.

     (a)  A Party shall give prompt notice to the other Parties of the
occurrence, or non-occurrence, of any event the occurrence, or non-occurrence,
of which results in any representation or warranty contained in this Agreement
being untrue or inaccurate in any material respect (or, in the case of any
representation or warranty qualified by its terms by materiality or Material
Adverse Effect, then untrue or inaccurate in any respect) and any failure of the
Parties, as the case may be, to comply with or satisfy in any material respect
any covenant, condition or agreement to be complied with or satisfied by it
hereunder; PROVIDED, HOWEVER, that the delivery of any notice pursuant to this
Section 7.6 shall not limit or otherwise affect the remedies available hereunder
to the party receiving such notice.


                                       36
<PAGE>   42


     (b)  A Party shall give prompt notice to the other Parties of (i) any
notice or other communication from any Person alleging that the consent of such
Person is or may be required in connection with the Merger; (ii) any notice or
other communication from any Governmental Authority in connection with the
Merger; (iii) any Litigation, relating to or involving or otherwise affecting
such Party that relates to the consummation of the Merger; (iv) the occurrence
of a default or event that, with notice or lapse of time or both, will become a
default under any contract which is material to Curis or any Company Material
Contract of such Party; and (v) any change that is reasonably likely to have a
Material Adverse Effect on such Party or is likely to delay or impede the
ability of any Party to consummate the transactions contemplated by this
Agreement or to fulfill their respective obligations set forth herein.

     (c)  Each of the Parties shall give (or shall cause their respective
Subsidiaries to give) any notices to third Persons, and use, and cause their
respective Subsidiaries to use, all reasonable efforts to obtain any consents
from third Persons (i) necessary, proper or advisable to consummate the
transactions contemplated by this Agreement, (ii) otherwise required under any
contracts, licenses, leases or other agreements in connection with the
consummation of the transactions contemplated hereby or (iii) required to
prevent a Material Adverse Effect on any of the Parties from occurring. If any
Party shall fail to obtain any such consent from a third Person, such Party
shall use all reasonable efforts, and will take any such actions reasonably
requested by the other Parties, to limit the adverse effect upon them, their
respective Subsidiaries, and their respective businesses resulting, or which
would result after the Effective Time, from the failure to obtain such consent.

     7.7  LISTING ON THE NASDAQ. Curis shall use its commercially reasonable
best efforts to cause the Surviving Company Common Stock to be issued in the
Merger to be approved for listing on NASDAQ National Market, subject to official
notice of issuance, prior to the Effective Time.

     7.8  PUBLIC ANNOUNCEMENTS. A Party shall consult with and obtain the
approval of the other Parties before issuing any press release or other public
announcement with respect to the Merger or this Agreement and shall not issue
any such press release prior to such consultation and approval, except as may be
required by applicable law or any listing agreement related to the trading of
the shares of either party on any national securities exchange or national
automated quotation system, in which case the Party proposing to issue such
press release or make such public announcement shall use reasonable efforts to
consult in good faith with each other Party before issuing any such press
release or making any such public announcement.

     7.9  ACCOUNTANT'S LETTERS. Upon reasonable notice, the Parties shall use
reasonable efforts to cause their respective independent public accountants to
deliver to the other Parties, as the case may be, a letter covering such matters
as are requested by the requesting Party, as the case may be, and as are
customarily addressed in accountant's "comfort" letters in connection with
registration statements similar to Form S-4.

     7.10 INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     (a)  From and after the Effective Time, Curis (as the Surviving Company)
shall, to the fullest extent permitted by Law, honor all of each Company's
obligations to indemnify (including any obligations to advance funds for
expenses) the current or former directors or officers of such


                                       37
<PAGE>   43


Company for acts or omissions by such directors and officers occurring prior to
the Effective Time to the extent that such obligations of such Company to
indemnify and advance expenses exist on the date of this Agreement, whether
pursuant to a Company's Certificate or Articles of Incorporation, a Company's
By-laws, individual indemnity agreements or otherwise, and such obligations
shall survive the Merger and shall continue in full force and effect in
accordance with the terms of the Companies' Certificates or Articles of
Incorporations, By-laws and such individual indemnity agreements from the
Effective Time until the later of (i) the expiration of the applicable statute
of limitations with respect to any claims against such directors or officers
arising out of such acts or omissions or (ii) in the case of any claims made
prior to the expiration of the applicable statute of limitations, the final
disposition of such claims.

     (b)  For a period of six years after the Effective Time, Curis (as the
Surviving Company) shall maintain in effect, if available, directors' and
officers' liability insurance covering those Persons who, as of immediately
prior to the Effective Time, are covered by each Company's directors' and
officers' liability insurance policy (the "Insured Parties") on terms no less
favorable to the Insured Parties than those of such Company's present directors'
and officers' liability insurance policy.

     (c)  The provisions of this Section 7.10 (i) are intended to be for the
benefit of, and will be enforceable by, each indemnified party, his or her heirs
and his or her representatives and (ii) are in addition to, and not in
substitution for, any other rights to indemnification or contribution that any
such person may have by contract or otherwise.

     7.11 COVENANTS FOR TAX-FREE STATUS. Prior to and after the Effective Time,
each Party shall use all commercially reasonable efforts to cause the Merger to
qualify as a reorganization within the meaning of Section 368(a) of the Code,
and will not take any action reasonably likely to cause the Merger not to so
qualify. After the Effective Time, Curis (as the Surviving Company) shall
continue at least one significant historic business line of each Company, or use
at least a significant portion of each Company's historic business assets in a
business, in each case within the meaning of Treasury Regulation Section
1.368-1(d).

     7.12 STOCKHOLDER AGREEMENTS.

     (a)  Concurrently with the execution of this Agreement, each Company is
delivering to the Other Companies a Stockholder Agreement in the form of EXHIBIT
A attached hereto executed by each director and officer of such Company, and
each of their respective Affiliates, from whom such Company has by then obtained
such a Stockholder Agreement. If and to the extent the following has not already
been accomplished at the time of execution of this Agreement, then, within 14
days after the date hereof, (i) Creative shall use its best efforts to cause a
Stockholder Agreement in the form of EXHIBIT A attached hereto to be executed
and delivered to the other Companies by each of Creative's directors and
officers, and each of their respective Affiliates, and any other Affiliates of
Creative (the "Creative Voting Commitment"), (ii) Ontogeny shall use its best
efforts to cause such a Stockholder Agreement to be executed and delivered to
the other Companies by each of Ontogeny's directors and officers, and each of
their respective Affiliates, and such of its other stockholders as are necessary
to obtain the requisite vote of the stockholders of Ontogeny to approve this
Agreement and the Merger, as well as the amendment of the Ontogeny Certificate
of Incorporation in substantially the form of EXHIBIT G


                                       38
<PAGE>   44


attached hereto, in accordance with the DGCL and its Certificate of
Incorporation (the "Ontogeny Required Stockholder Vote"), and (iii) Reprogenesis
shall use its best efforts to cause such a Stockholder Agreement to be executed
and delivered to the other Companies by each of Reprogenesis' directors and
officers, and each of their respective Affiliates, and such of its other
stockholders as are necessary to obtain the requisite vote of the stockholders
of Reprogenesis to approve this Agreement and the Merger, as well as the
amendment of the Reprogenesis Articles of Incorporation in substantially the
form of EXHIBIT H attached hereto, in accordance with the TBCA and its Articles
of Incorporation (the "Reprogenesis Required Stockholder Vote"); PROVIDED,
however, that the obligation of Ontogeny to deliver the Stockholder Agreements
representing the Ontogeny Required Stockholder Vote, and the obligation of
Reprogenesis to deliver Stockholder Agreements representing the Reprogenesis
Required Stockholder Vote, is subject to the satisfaction of such obligation by
the other such Company.

     (b)  If, within 14 days after the date of this Agreement, Ontogeny has been
able to obtain Stockholder Agreements representing the Ontogeny Required
Stockholder Vote, except that it has not been able to obtain Stockholder
Agreements from stockholders whose vote is sufficient to approve amendment of
any or all of Sections D.4(h) or E.4(h) of Article Fourth of the Ontogeny
Certificate of Incorporation, Section 4(h) of the Certificate of Designation of
the Series C-1 Convertible Preferred Stock thereunder, or Section 4(h) of the
Certificate of Designation of the Series G Convertible Preferred Stock
thereunder (as the case may be, the "Applicable Preferred Stock Provisions") in
substantially the manner contemplated by Exhibit G attached hereto (the Ontogeny
Required Stockholder Vote, excluding the requisite stockholder vote described in
the foregoing exception, being referred to herein as the "Ontogeny Minimum
Required Stockholder Vote"), and if Reprogenesis has been able to obtain
Stockholder Agreements representing the Reprogenesis Stockholder Vote, then
Curis and the Companies shall cooperate in good faith, within 28 days after the
date of this Agreement, to prepare and adopt mutually acceptable amendments to
the Certificate of Incorporation of Curis and to this Agreement that will (i)
authorize a class or series of convertible capital stock of Curis which has the
minimum rights necessary to satisfy the requirements of the Applicable Preferred
Stock Provisions as they apply to the Merger, (ii) provide for the conversion of
the shares of Ontogeny Preferred Stock to which the Applicable Preferred Stock
Provisions relate into such new class or series of convertible stock of Curis
(rather than into Common Stock of Curis) on a basis otherwise consistent with
Section 2.1(b), and (iii) make such other changes, if any, as may be necessary
or appropriate to give effect to the foregoing.

     (c)  Each Company acknowledges and agrees to be bound by and comply with
the provisions of paragraph 2 of each of the Stockholder Agreements, as
applicable to such Company, as if a party thereto, with respect to transfers of
record of ownership of shares of Company Stock, and agrees to notify the
transfer agent for any such shares and provide such documentation and do such
other things as may be necessary to effectuate the provisions of such
Stockholder Agreements.

     7.13 AFFILIATE AGREEMENTS.

     (a)  Identified in Section 7.13 of each Company Disclosure Schedule is a
list of each Person who is a director or executive officer of the Company and,
to the Company's best Knowledge, each Person who is a holder of 10% or more of
the outstanding Voting Stock of such Company, and such Persons are, in the
reasonable judgment of such Company, all Persons


                                       39
<PAGE>   45


who are "affiliates" of such Company within the meaning of Rule 145 promulgated
under the Securities Act ("Rule 145"). Each Company shall provide such
information and documents as any other Party shall reasonably request for
purposes of reviewing such list and shall notify such other Parties in writing
regarding any change in the identity of its affiliates prior to the Closing
Date. Each Company shall use its best efforts to deliver or cause to be
delivered to the other Parties no later than the date of the filing of the
Registration Statement from each of their respective affiliates, an executed
agreement, in substantially the form attached hereto as EXHIBIT E (an "Affiliate
Agreement"), by which each such affiliate agrees to comply with the applicable
requirements of Rule 145 and other applicable securities laws. Curis shall be
entitled to place appropriate legends on the certificates evidencing any
Surviving Company Common Stock to be received by such affiliates pursuant to the
terms of this Agreement, and to issue appropriate stop transfer instructions to
the transfer agent for the Surviving Company Common Stock, consistent with the
terms of the Affiliate Agreements (provided that such legends or stop transfer
instructions shall be promptly removed, after the required restricted period).

     (b)  Curis shall, at all times during the two (2) year period beginning on
the Closing Date, whether or not it is subject to the reporting requirements of
Section 13 or Section 15(d) of the Exchange Act, comply with the current public
information requirements of Rule 144(c)(1) promulgated under the Securities Act.

     7.14 SEC FILINGS. Prior to the Effective Time, each Company that is a
Public Company shall (a) timely file with the SEC each periodic or current
report required to be filed by it under the Exchange Act and (b) promptly after
filing such report, furnish each other Party with a copy.

     7.15 MAINTENANCE, PROSECUTION AND FILING OBLIGATIONS. Each Company shall
pay the costs of preparation for filing, prosecution and maintenance of each of
their respective Intellectual Property Rights as required and shall not permit
the lapse of any filings following the execution of this Agreement, except in
its reasonable business judgment in light of the transactions contemplated
hereby. Each Company shall provide copies of all filings and evidence of
payments under this Section 7.15 to the other Parties.

     7.16 CERTAIN AGREEMENTS. Each Company irrevocably and unconditionally
agrees that it (a) will vote all of the shares of Curis Common Stock owned by it
in favor of the Merger Agreement and the Merger at any meeting or meetings of
Curis's stockholders called to vote upon the Merger Agreement and the Merger;
(b) will not vote such shares (or otherwise provide a proxy or consent or a
voting agreement with respect thereto) in favor of any other Acquisition
Proposal; and (c) will timely take all action necessary to (i) elect as
directors of Curis the persons designated on or pursuant to SCHEDULE 1.5, (ii)
amend the Curis Certificate of Incorporation to eliminate the ability of Curis
stockholders to act by written consent and (iii) approve a Curis employee,
director and consultant stock plan.

     7.17 LOCK-UP AGREEMENTS. Each Company shall use its best efforts to deliver
or cause to be delivered to the other Parties no later than the date of the
filing of the Registration Statement from each Company officer and director and
each Person who is an Affiliate of each such officer and director, an executed
agreement, in substantially the form attached hereto as EXHIBIT F (a "Lock-Up
Agreement"); PROVIDED, however, that no Company shall be obligated to deliver
its Lock-Up Agreements to the other Companies unless both other Companies also


                                       40
<PAGE>   46


deliver all of their required Lock-Up Agreements. The Surviving Company may
impose stop-transfer instructions with respect to the shares subject to the
foregoing restriction until the end of said period.

     7.18 CURIS BOARD AUTHORIZATION. In connection with obtaining the exemption
of certain transactions from the requirements of Section 16 of the Exchange Act
pursuant to Rule 16b-3 thereunder, Curis shall use its best efforts to approve,
by resolution of its Board of Directors, the acquisition of Surviving Company
Common Stock by its officers and directors in the Merger.

     7.19 BEST EFFORTS OBLIGATIONS. Where provisions of this Agreement
(including, without limitation, Sections 7.4, 7.12, 7.13, 7.17 and 7.18) require
a Company to use its best efforts or its reasonable efforts to obtain consents,
waivers, approvals, authorizations, agreements (including Stockholder
Agreements, Affiliate Agreements and Lock-Up Agreements) or the like from any
other Person, or otherwise to cause any other Person to take action or refrain
from taking action, such Company shall not be obligated to pay any amount or
provide anything of value (other than filing fees and other required amounts in
the case of Governmental Authorities) to such other Person to induce such Person
to act in the desired manner.

                                  ARTICLE VIII

                              CONDITIONS OF MERGER

     8.1  CONDITIONS TO OBLIGATION OF ALL PARTIES TO EFFECT THE MERGER. The
respective obligations of each Party to effect the Merger shall be subject to
the satisfaction at or prior to the Effective Time of the following conditions:

     (a)  EFFECTIVENESS OF THE REGISTRATION STATEMENTS. The Registration
Statement and the Exchange Act Registration Statement shall have been declared
effective; no stop order suspending the effectiveness of the Registration
Statement or the Exchange Act Registration Statement shall have been issued by
the SEC and no proceedings for that purpose shall have been initiated; and no
similar proceeding in respect of the Joint Proxy Statement shall have been
initiated or, to the Knowledge of any Party, threatened by the SEC.

     (b)  STOCKHOLDER APPROVAL. This Agreement and the Merger shall have been
authorized by the requisite vote of the stockholders of each Company in
accordance with the provisions of the DGCL or the TBCA (as the case may be) and
the Certificate or Articles of Incorporation and By-laws of each respective
Party.

     (c)  HSR ACT. The waiting period applicable to the consummation of the
Merger under the HSR Act shall have expired or been terminated.

     (d)  NO INJUNCTIONS OR RESTRAINTS; ILLEGALITY. No Court or Governmental
Authority having jurisdiction over any Party shall have enacted, issued,
promulgated, enforced or entered any Law, Regulation or Order (whether
temporary, preliminary or permanent) which is then in effect and which has the
effect of making the Merger illegal or otherwise preventing or prohibiting
consummation of the Merger.


                                       41
<PAGE>   47


     (e)  NASDAQ. The shares of Surviving Company Common Stock issuable to the
stockholders of the Companies pursuant to this Agreement shall have been
approved for listing on NASDAQ National Market subject to official notice of
issuance.

     (f)  APPRAISAL SHARES. The Appraisal Shares of Ontogeny shall comprise not
more than 5% of the issued and outstanding Ontogeny Common Stock and not more
than 5% of the issued and outstanding Ontogeny Preferred Stock.

     (g)  DISSENTING SHARES. The Dissenting Shares of Reprogenesis shall
comprise not more than 5% of the issued and outstanding Reprogenesis Common
Stock and not more than 5% of the issued and outstanding Reprogenesis Preferred
Stock.

     (h)  CHARTER AMENDMENTS. An amendment to the Amended and Restated
Certificate of Incorporation of Ontogeny in substantially the form of EXHIBIT G
attached hereto shall have been duly adopted and filed with the Secretary of
State of the State of Delaware, unless Section 7.12(b) of this Agreement has
become applicable, in which case such amendment shall not include an amendment
of the Applicable Preferred Stock Provisions. Articles of Amendment to the
Articles of Incorporation of Reprogenesis in substantially the form of EXHIBIT H
attached hereto shall have been duly adopted and filed with the Secretary of
State of the State of Texas. If Section 7.12(b) has become applicable, an
amendment to the Curis Certificate of Incorporation as contemplated by Section
7.12(b) shall have been duly adopted and filed with the Secretary of State of
the State of Delaware.

     8.2  ADDITIONAL CONDITIONS TO OBLIGATION OF EACH PARTY TO EFFECT THE
MERGER. The respective obligations of each Party to effect the Merger shall be
subject to the satisfaction at or prior to the Effective Time of the additional
following conditions by each other Party, any or all of which may be waived by
such Party, in whole or in part, to the extent permitted by applicable Law:

     (a)  REPRESENTATIONS AND WARRANTIES. The representations and warranties of
each other Party contained in this Agreement shall be true and correct in all
material respects on and as of the Effective Time, except for (x) changes
contemplated by this Agreement (including the Disclosure Schedules hereto), (y)
those representations and warranties that are qualified by materiality or by
Company Material Adverse Effect or Curis Material Adverse Effect, as the case
may be, in which case such representations and warranties shall be true and
correct in all respects subject to such qualifications and (z) those
representations and warranties which address matters only as of a particular
date (in which case such representations and warranties shall be true and
correct in all material respects, on and as of such particular date, with the
same force and effect as if made on and as of the Effective Time), and such
Party shall have received certificates to such effect signed by the Chief
Executive Officer and Chief Financial Officer of each other Party.

     (b)  AGREEMENTS AND COVENANTS. Each other Party shall have performed or
complied in all material respects with all agreements and covenants required by
this Agreement to be performed or complied with by it on or prior to the
Effective Time, and such Party shall have received certificates to such effect
signed by the Chief Executive Officer and Chief Financial Officer of each of
other Party.


                                       42
<PAGE>   48


     (c)  REGULATORY APPROVALS. All approvals and consents of applicable Courts
and/or Governmental Authorities required for each other Party to consummate the
Merger shall have been received, except for such approvals and consents the
failure of which to have been so received, shall not have had, or be reasonably
be expected to have, a Company Material Adverse Effect or a Curis Material
Adverse Effect, as the case may be.

     (d)  THIRD PARTY CONSENTS. Such Party shall have received evidence, in form
and substance reasonably satisfactory to it, that the licenses, permits,
consents, waivers, approvals, authorizations, qualifications or Orders of
Governmental Authorities and other third parties required by each of the other
Parties as described in the Company Disclosure Schedule of such other Parties
have been obtained, except where failure to have been so obtained, either
individually or in the aggregate, is not reasonably likely to have a Company
Material Adverse Effect or a Curis Material Adverse Effect, as the case may be.
Notwithstanding the foregoing, (i) Creative shall have received evidence, in
form and substance reasonably satisfactory to it, that the licenses, permits,
consents, waivers, approvals, authorizations, qualifications or Orders of
Governmental Authorities and other third parties set forth on Schedule 8.2(d) of
the Company Disclosure Schedules of each of the other two Companies shall have
been obtained; (ii) Ontogeny shall have received evidence, in form and substance
reasonably satisfactory to it, that the licenses, permits, consents, waivers,
approvals, authorizations, qualifications or Orders of Governmental Authorities
and other third parties set forth on Schedule 8.2(d) of the Company Disclosure
Schedules of each of the other two Companies shall have been obtained; and (iii)
Reprogenesis shall have received evidence, in form and substance reasonably
satisfactory to it, that the licenses, permits, consents, waivers, approvals,
authorizations, qualifications or Orders of Governmental Authorities and other
third parties set forth on Schedule 8.2(d) of the Company Disclosure Schedules
of each of the other two Companies shall have been obtained.

     (e)  TAX OPINIONS. Such Party shall have received a written opinion from
its counsel to the effect that the Merger will be treated for federal income tax
purposes as a tax-free reorganization within the meaning of Section 368(a) of
the Code; provided that if such counsel does not render such opinion, this
condition shall nonetheless be deemed satisfied if counsel for any other Company
renders such opinion to such Party (it being agreed that each Company shall
provide reasonable cooperation, including making reasonable representations, to
each Company counsel to enable it to render such opinion).

                                   ARTICLE IX

                        TERMINATION, AMENDMENT AND WAIVER

     9.1  TERMINATION. This Agreement may be terminated and the Merger
contemplated hereby may be abandoned at any time prior to the Effective Time,
notwithstanding approval thereof by the stockholders of each Party:

     (a)  By mutual written consent duly authorized by the Boards of Directors
of each Party; or

     (b)  By any Company if the Merger shall not have been consummated on or
before August 31, 2000; PROVIDED, that the right to terminate this Agreement
under this Section 9.1(b)


                                       43
<PAGE>   49


shall not be available to any Company whose failure to fulfill any obligation
under this Agreement has been the cause of, or resulted in, the failure of the
Merger to have been consummated on or before such date; or

     (c)  By any Company if a Court of competent jurisdiction or Governmental
Authority shall have issued an Order, decree or ruling or taken any other
action, in each case which has become final and non-appealable, which restrains,
enjoins or otherwise prohibits the Merger; or

     (d)  By any Company, if, at the Company Meeting of any other Company
(including any adjournment or postponement thereof), the requisite vote of the
stockholders of such other Company to authorize this Agreement shall not have
been obtained; PROVIDED that the right to terminate this Agreement under this
Section 9.1(d) shall not be available to any Company where the failure to obtain
such stockholder approval shall have been caused by the action or failure to act
of such Company in breach of this Agreement; or

     (e)  By any Company, if the Board of Directors of any other Company or any
committee thereof (the "Defaulting Party") shall have (1) approved or
recommended any Acquisition Proposal other than the Merger, (2) failed to
present and recommend the authorization of this Agreement and the Merger to the
stockholders of such other Company, or withdrawn or modified in a manner adverse
to such Company, its recommendation of the Merger, this Agreement or the
transactions contemplated hereby, (3) failed to mail the Joint Proxy Statement
to its stockholders within five (5) Business Days of when the Joint Proxy
Statement was available for mailing or failed to include therein such approval
and recommendation (including the recommendation that the stockholders of such
other Party vote in favor of the Merger), (4) upon a request by any Party to
reaffirm the approval and recommendation of the Merger, failed to do so within
five (5) Business Days after such request is made, (5) entered, or caused such
other Company to enter, into any letter of intent, agreement in principle,
acquisition agreement or other similar agreement related to any Acquisition
Proposal, (6) recommended to the stockholders of such other Company, following
the commencement of a tender or exchange offer for outstanding shares of such
other Company's Common Stock, that such stockholders tender their shares in such
tender or exchange offer or failed, within 10 days of the commencement of such
offer, to recommend against acceptance of such offer, (7) taken any action
prohibited by Section 6.1, or (8) resolved by the Board of Directors of such
other Company or announced its intention to do any of the foregoing;

     (f)  By any Company, if such Company is not in material breach of its
obligations or its representations and warranties under this Agreement, and if
(i) there has been a breach at any time by any other Company of any of their
respective representations and warranties hereunder such that Section 8.2(a) of
this Agreement would not be satisfied (treating such time as if it were the
Effective Time for purposes of this Section 9.1(f)) or (ii) there has been the
willful breach on the part of any other Company of any of its covenants or
agreements contained in this Agreement (other than the breach of a covenant
which is dealt with in Section 9.1(e) above) such that Section 8.2(b) of this
Agreement would not be satisfied (treating such time as if it were the Effective
Time for purposes of this Section 9.1(f)), and, in the case of either clause (i)
or (ii) above, such breach (if curable) has not been cured within 30 days after
written notice to both other Companies;


                                       44
<PAGE>   50


     (g)  By Creative, no later than 21 days after the date of this Agreement,
if Ontogeny shall have failed to deliver Stockholder Agreements representing the
Ontogeny Minimum Required Stockholder Vote, or Reprogenesis shall have failed to
deliver Stockholder Agreements representing the Reprogenesis Required
Stockholder Vote, in either case within 14 days after the date of this
Agreement;

     (h)  By Ontogeny, no later than 21 days after the date of this Agreement,
if Creative shall have failed to deliver Stockholder Agreements representing the
Creative Voting Commitment, or Reprogenesis shall have failed to deliver
Stockholder Agreements representing the Reprogenesis Required Stockholder Vote,
in either case within 14 days after the date of this Agreement; or

     (i)  By Reprogenesis, no later than 21 days after the date of this
Agreement, if Ontogeny shall have failed to deliver Stockholder Agreements
representing the Ontogeny Minimum Required Stockholder Vote, or Creative shall
have failed to deliver Stockholder Agreements representing the Creative Voting
Commitment, in either case within 14 days after the date of this Agreement.

     9.2  EFFECT OF TERMINATION. Except as provided in this Section 9.2, in the
event of the termination of this Agreement pursuant to Section 9.1, this
Agreement (other than this Section 9.2 and Sections 5.3, 9.3 and Article X
hereof, which shall survive such termination) will forthwith become void, and
there will be no liability on the part of any Party or any of their respective
officers or directors to the other and all rights and obligations of any Party
hereto will cease, except that nothing herein will relieve any Party from
liability for any breach, prior to termination of this Agreement in accordance
with its terms, of any representation, warranty, covenant or agreement contained
in this Agreement.

     9.3  FEES AND EXPENSES.

     (a)  Except as set forth in this Section 9.3, all fees and expenses
incurred in connection with this Agreement and the transactions contemplated
hereby shall be paid by the Party incurring such expenses, whether or not the
Merger is consummated; PROVIDED that each Company shall share pro rata, in
proportion to its proposed relative ownership of Curis upon consummation of the
Merger, all fees and expenses, other than attorneys' fees, incurred in relation
to the printing and filing of the Joint Proxy Statement (including any
preliminary materials related thereto), the Registration Statement (including
financial statements and exhibits) and any amendments or supplements thereto,
and any fees and expenses required to be paid by Curis (it being understood that
the HSR Act filing fee shall be borne equally by the Companies).

     (b)  In the event that any of the following occurs:

               (i)  any Party terminates this Agreement pursuant to Section
     9.1(e) hereof; or

               (ii) (A) any Company or Companies (as applicable) terminates this
     Agreement pursuant to (y) Section 9.1(d) hereof as a result of the failure
     to receive the requisite vote of the stockholders of any other Company (the
     "Breaching Party") at the


                                       45
<PAGE>   51


     Company Meeting of the Breaching Party if, at the time of such failure an
     Acquisition Proposal to the Breaching Party shall have been made, or
     proposed, communicated or disclosed in a manner which is or otherwise
     becomes public (including being known by any stockholder of such Party) or
     (z) Section 9.1(f) hereof after a breach by any other Company (the
     "Breaching Party") of any of the Breaching Party's covenants or agreements
     contained in this Agreement and (B) within one year of such termination,
     either (1) the Breaching Party or any of its Subsidiaries enters into an
     agreement with any Person with respect to an Acquisition Proposal which
     provides for (x) transfer or issuance of securities representing more than
     50% of the equity or voting interests in the Breaching Party, (y) a merger,
     consolidation, recapitalization or another transaction resulting in the
     issuance of cash or securities of any Person (other than a reincorporation
     or a holding company merger that results in the stockholders of the
     Breaching Party owning all of the equity interests in the surviving
     corporation) to the stockholders of the Breaching Party in exchange for
     more than 50% of the equity or voting interests in the Breaching Party or
     (z) transfer of assets, securities or ownership interests representing more
     than 50% of the consolidated assets or earning power of the Breaching Party
     or (2) any Person commences a tender offer that results in the acquisition
     by the Person making the tender offer of a majority of the outstanding
     Company Common Stock,

then the Defaulting Party or the Breaching Party, as the case may be, shall pay
to each other Company that is not in material breach of its obligations or its
representations and warranties under this Agreement at the time of such
termination (and, only in the case of clause (ii)(A)(y) above, that has received
the requisite vote of its stockholders at its Company Meeting to approve this
Agreement), a fee in cash in the amount of $5 million (and therefore a total of
$10,000,000 to both other Companies, if both are entitled to receive such fees),
plus the amount of such Company's Stipulated Expenses (the "Termination Fee"),
which Termination Fee shall be payable by wire transfer of immediately available
funds (i) in the case of a termination pursuant to Section 9.1(e), at the time
of such termination or (ii) in the case of a termination pursuant to Section
9.1(d) or 9.1(f), at the time such agreement is entered into or such tender
offer is commenced, as the case may be, except as otherwise provided in Section
9.3(c) with respect to Stipulated Expenses. Termination by any Company pursuant
to Section 9.1(d) or 9.1(f) under circumstances where the Termination Fee is
then payable shall not be effective with respect to the Company owing such
Termination Fee until receipt of the Termination Fee by the other Companies.

     (c)  If this Agreement is terminated pursuant to Section 9.1(f) (other than
due to an event after the date of this Agreement that results in a breach of a
representation or warranty, which event is entirely outside the control of the
Breaching Party and due to no act or omission to act of the Breaching Party),
then the Breaching Party causing such termination shall reimburse each other
Party for all Stipulated Expenses not later than two (2) Business Days after the
date of such termination.

     (d)  As used in this Agreement, the term "Stipulated Expenses" shall mean
those reasonable fees and expenses actually incurred by any Company in
connection with this Agreement and the transactions contemplated hereby,
including fees and expenses of counsel, investment bankers, accountants,
experts, consultants and other Representatives, including (y) such Company's
efforts to merge and (z) salaries, travel costs and expenses incurred by such


                                       46
<PAGE>   52


Company as a result of changes to its business plan in contemplation of the
Merger; PROVIDED that the Stipulated Expenses of any Company shall not exceed
$750,000.

     (e)  Nothing in this Section 9.3 shall be deemed to be exclusive of any
other rights or remedies any Party may have hereunder or at law or in equity for
any breach of this Agreement.

     (f)  In the event that Reprogenesis terminates this Agreement pursuant to
Section 9.1(d) hereof as a result of the failure to receive the requisite vote
of the Stockholders of Creative at the Company Meeting of Creative, then
Creative shall pay Reprogenesis a fee in the aggregate amount of $1,500,000,
which shall be payable by wire transfer of immediately available funds within
five (5) business days of such termination.

     (g)  In the event that (i) any Company or Companies, as applicable,
terminates this Agreement pursuant to Section 9.1(d) hereof as a result of the
failure to receive the requisite vote of the stockholders of any other Company
(the "Failing Party") at its Company Meeting to approve this Agreement, and (ii)
each such terminating Company has received the requisite vote of its
stockholders at its Company Meeting to approve this Agreement, and (iii) within
one year of such termination, the Failing Party or its Subsidiaries enters into
an agreement with any Person with respect to an Equity Financing (as defined
below) providing the Failing Company with gross proceeds equal to or greater
than $50,000,000, then the Failing Party shall pay, to each other Company that
both has received the requisite vote of its stockholders at its Company Meeting
to approve this Agreement and is not in material breach of its obligations or
its representations and warranties under this Agreement at the time of such
termination, a fee in the amount of $5,000,000 (and therefore a total of
$10,000,000 to both other Companies, if both are entitled to receive such fees).
Such fee shall be payable by wire transfer of immediately available funds at the
time the Failing Party has received at least $50,000,000 of gross proceeds from
such Equity Financing. Termination by any Company pursuant to Section 9.1(d)
under circumstances where the fee under this Section 9.3(g) is then payable
shall not be effective with respect to the Failing Party until receipt of such
fee by each Company entitled to receive it. As used is this Section 9.3, the
term "Equity Financing" means a financing transaction (or series of related
transactions) in which a Company raises proceeds by selling shares of its
capital stock or any security convertible into, or exchangeable or exercisable
for, its capital stock.

     (h)  In the event that (i) any Company or Companies, as applicable,
terminates this Agreement pursuant to Section 9.1(f) hereof after a breach by
any other Company (the "Breaching Party") of any of the Breaching Party's
covenants or agreements contained in this Agreement, and (ii) within one year of
such termination, the Breaching Party or its Subsidiaries enters into an
agreement with any Person with respect to an Equity Financing providing the
Breaching Company with gross proceeds equal to or greater than $50,000,000, then
the Breaching Party shall pay, to each other Company that is not in material
breach of its obligations or its representations and warranties under this
Agreement at the time of such termination, a fee in the amount of $5,000,000
(and therefore a total of $10,000,000 to both other Companies, if both are
entitled to receive such fees). Such fee shall be payable by wire transfer of
immediately available funds at the time the Breaching Party has received at
least $50,000,000 of gross proceeds from such Equity Financing. Termination by
any Company pursuant to Section 9.1(f) under circumstances where the fee under
this Section 9.3(h) is then payable shall not be effective with respect to the
Breaching Party until receipt of such fee by each Company entitled to receive
it.


                                       47
<PAGE>   53


     (i)  Notwithstanding any other provision hereof to the contrary, (i) the
maximum amount of the fees that any Company shall be obligated to pay to any
other Company pursuant to Sections 9.3(b), 9.3(f), 9.3(g) and 9.3(h), even if
more than one of such Sections is applicable, shall be $5,000,000 (and therefore
a total of $10,000,000 to both other Companies, if both are entitled to receive
such fees), and (ii) any Company shall be obligated to pay the Stipulated
Expenses of any other Company only once pursuant to Sections 9.3(b) and 9.3(c),
even if more than one of such Sections is applicable.

     9.4  AMENDMENT. This Agreement may be amended by the Parties hereto by
action taken by or on behalf of their respective Boards of Directors at any time
prior to the Effective Time, subject to Section 252 of the DGCL. This Agreement
may not be amended except by an instrument in writing signed by all of the
Parties hereto.

     9.5  WAIVER. At any time prior to the Effective Time, any Party hereto may
extend the time for the performance by any other Party of any of the obligations
or other acts required hereunder, waive any inaccuracies in the representations
and warranties of any other Party contained herein or in any document delivered
pursuant hereto and waive compliance by any other Party with any of the
agreements or conditions contained herein. Any such extension or waiver shall be
valid if set forth in an instrument in writing signed by the Party or Parties to
be bound thereby.

                                    ARTICLE X

                               GENERAL PROVISIONS

     10.1 SURVIVAL OF REPRESENTATIONS AND WARRANTIES.

     (a)  Except as set forth in Section 10.1(b) of this Agreement, the
representations, warranties and agreements of each Party hereto will remain
operative and in full force and effect regardless of any investigation made by
or on behalf of any other Party hereto, any Person controlling any such Party or
any of their officers, directors, representatives or agents whether prior to or
after the execution of this Agreement.

     (b)  The representations and warranties in this Agreement will terminate at
the Effective Time; PROVIDED, HOWEVER, this Section 10.1(b) shall in no way
limit any covenant or agreement of the Parties which by its terms contemplates
performance after the Effective Time or after the termination of this Agreement
pursuant to Article IX.

     10.2 NOTICES. All notices or other communications which are required or
permitted hereunder shall be in writing and sufficient if delivered personally
or sent by a nationally-recognized overnight courier or by registered or
certified mail, postage prepaid, return receipt requested, or by electronic
mail, with a copy thereof to be delivered by mail (as aforesaid) within 24 hours
of such electronic mail, or by telecopier, with confirmation as provided above
addressed as follows:


                                       48
<PAGE>   54


If to Creative:     Creative Biomolecules, Inc.
                    101 Huntington Avenue
                    Boston, Massachusetts 02111
                    Telecopier:    (617) 912-2995
                    Attention:     Michael Tarnow, President
                                   Cheryl Lawton, Esq., General Counsel
                                    and Vice President, Administration

               With a copy to:

                    Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                    One Financial Center
                    Boston, Massachusetts  02111
                    Telecopier:    (617) 542-2211
                    Attention:     Jeffrey M. Wiesen, Esq.
                                   Lewis J. Geffen, Esq.

If to Reprogenesis: Reprogenesis, Inc.
                    21 Erie Street
                    Cambridge, MA  02139
                    Telecopier:      (617) 499-2927
                    Attention:     Daniel R. Omstead, President

               With a copy to:

                    Baker Botts LLP
                    One Shell Plaza
                    910 Louisana
                    Houston, TX  77002
                    Telecopier:    (713) 229-1522
                    Attention:     Walter J. Smith, Esq.

If to Ontogeny:     Ontogeny, Inc.
                    45 Moulton Street
                    Cambridge, Massachusetts 02138
                    Telecopier:    (617) 876-0866
                    Attention:     Doros Platika, President
                                   Bruce A. Leicher, Vice President and General
                                    Counsel

               With a copy to:

                    Foley, Hoag & Eliot LLP
                    One Post Office Square
                    Boston, Massachusetts 02109
                    Telecopier:    (617) 832-7000
                    Attention:     Robert Birnbaum, Esq.
                                   Jonathan Hulbert, Esq.

If to Curis:   to each of the Companies (with copies to its counsel).


                                       49
<PAGE>   55


or to such other address as the Party to whom notice is to be given may have
furnished to the other Parties in writing in accordance herewith. All such
notices or communications shall be deemed to be received (a) in the case of
personal delivery, on the date of such delivery, (b) in the case of a
nationally-recognized overnight courier, on the next Business Day after the date
when sent (c) in the case of facsimile transmission or telecopier or electronic
mail, upon confirmed receipt, and (d) in the case of mailing, on the third
Business Day following the date on which the piece of mail containing such
communication was posted.

     10.3 CERTAIN DEFINITIONS. For purposes of this Agreement, the term:

     "Affiliate" means, with respect to any Person, any other Person that
directly or indirectly, through one or more intermediaries, Controls, is
Controlled by, or is under common Control with, such Person.

     "Business Day" means any day other than a Saturday, Sunday or day on which
banks are permitted to close in the State of New York or in the State of
Delaware.

     "Control" (including the terms "controlled by" and "under common control
with") means the possession, directly or indirectly or as trustee or executor,
of the power to direct or cause the direction of the management or policies of a
Person, whether through the ownership of stock, as trustee or executor, by
contract or credit arrangement or otherwise.

     "Court" means any court or arbitration tribunal of the United States, any
domestic state, or any foreign country, and any political subdivision thereof.

     "Exchange Agent" means any bank or trust company organized under the Laws
of the United States or any of the states thereof and having a net worth in
excess of $100 million designated and appointed to act in the capacities
required under Section 2.6.

     "Governmental Authority" means any governmental agency or authority (other
than a Court) of the United States, any domestic state, or any foreign country,
and any political subdivision or agency thereof, and includes any authority
having governmental or quasi-governmental powers.

     "Knowledge" means (i) in the case an individual, knowledge of a particular
fact or other matter if such individual is actually aware of such fact or other
matter and (ii) in the case of an entity (other than an individual) such entity
will be deemed to have "Knowledge" of a particular fact or other matter if any
individual who is serving, or has at any time served, as a director, officer,
partner, executor, or trustee of such Person has (while such individual is
serving in such capacity), or at any time had (while such individual was serving
in such capacity), Knowledge of such fact or other matter.

     "Law" means all laws, statutes and ordinances of any Governmental Agency
including all decisions of Courts having the effect of law within its
jurisdiction.

     "Lien" means any mortgage, pledge, security interest, attachment,
encumbrance, lien (statutory or otherwise), option, conditional sale agreement,
right of first refusal, first offer, termination, participation or purchase or
charge of any kind (including any agreement to give


                                       50
<PAGE>   56


any of the foregoing); provided, however, that the term "Lien" shall not include
(i) statutory liens for Taxes, which are not yet due and payable or are being
contested in good faith by appropriate proceedings, (ii) statutory or common law
liens to secure landlords, lessors or renters under leases or rental agreements
confined to the premises rented, (iii) deposits or pledges made in connection
with, or to secure payment of, workers' compensation, unemployment insurance,
old age pension or other social security programs mandated under applicable
Laws, (iv) statutory or common law liens in favor of carriers, warehousemen,
mechanics and materialmen, to secure claims for labor, materials or supplies and
other like liens, and (v) restrictions on transfer of securities imposed by
applicable state and federal securities Laws.

     "Litigation" means any suit, action, arbitration, cause of action, claim,
complaint, criminal prosecution, investigation, demand letter, governmental or
other administrative proceeding, whether at law or at equity, before or by any
Court or Governmental Authority, or before any arbitrator or other tribunal.

     "Order" means any judgment, order, writ, injunction or decree of any Court
or Governmental Authority.

     "Person" means an individual, corporation, partnership, association, trust,
unincorporated organization, limited liability company, other entity or group
(as defined in Section 13(d)(3) of the Exchange Act).

     "Regulation" means any rule or regulation of any Governmental Authority
having the effect of Law.

     "Subsidiary" or "Subsidiaries" of any Party or any other Person means any
corporation, partnership, joint venture, limited liability company or other
legal entity of which such Party or such other Person, as the case may be,
(either alone or through or together with any other Subsidiary) owns, directly
or indirectly, 50% or more of the stock or other equity interests the holders of
which are generally entitled to vote for the election of the board of directors
or other governing body of such corporation or other legal entity.

     "Voting Stock" of any Company means the capital stock of such Company
entitled to vote upon the election of directors and upon other matters generally
submitted to stockholders of such Company for voting purposes.

     10.4 INTERPRETATION. When a reference is made in this Agreement to
Sections, subsections, Schedules or Exhibits, such reference shall be to a
Section, subsection, Schedule or Exhibit to this Agreement unless otherwise
indicated. The words "include," "includes" and "including" when used herein
shall be deemed in each case to be followed by the words "without limitation."
The word "herein" and similar references mean, except where a specific Section
or Article reference is expressly indicated, the entire Agreement rather than
any specific Section or Article. The table of contents and the headings
contained in this Agreement are for reference purposes only and shall not affect
in any way the meaning or interpretation of this Agreement.

     10.5 SEVERABILITY. If any term or other provision of this Agreement is
invalid, illegal or incapable of being enforced by any rule of law, or public
policy, all other conditions and provisions of this Agreement shall nevertheless
remain in full force and effect so long as the


                                       51
<PAGE>   57


economic or legal substance of the transactions contemplated hereby is not
affected in any manner adverse to any Party. Upon such determination that any
term or other provision is invalid, illegal or incapable of being enforced, the
Parties hereto shall negotiate in good faith to modify this Agreement so as to
effect the original intent of the Parties as closely as possible in an
acceptable manner to the end that transactions contemplated hereby are fulfilled
to the extent possible.

     10.6 ENTIRE AGREEMENT. This Agreement (including all exhibits and schedules
hereto) constitutes the entire agreement and supersedes all prior agreements and
undertakings (other than the Confidentiality Agreements), both written and oral,
among the Parties, or any of them, with respect to the subject matter hereof
and, except as otherwise expressly provided herein, are not intended to confer
upon any other Person any rights or remedies hereunder.

     10.7 ASSIGNMENT. This Agreement shall not be assigned by operation of law
or otherwise.

     10.8 PARTIES IN INTEREST. This Agreement shall be binding upon and inure
solely to the benefit of each Party hereto, and other than with respect to
Section 7.10 which the Parties intend to establish third party beneficiary
rights, nothing in this Agreement, express or implied, is intended to or shall
confer upon any other Person any right, benefit or remedy of any nature
whatsoever under or by reason of this Agreement.

     10.9 FAILURE OR INDULGENCE NOT WAIVER; REMEDIES CUMULATIVE. No failure or
delay on the part of any Party hereto in the exercise of any right hereunder
will impair such right or be construed to be a waiver of, or acquiescence in,
any breach of any representation, warranty or agreement herein, nor will any
single or partial exercise of any such right preclude other or further exercise
thereof or of any other right. All rights and remedies existing under this
Agreement are cumulative to, and not exclusive to, and not exclusive of, any
rights or remedies otherwise available.

     10.10 GOVERNING LAW. This agreement and the agreements, instruments and
documents contemplated hereby will be governed by and construed in accordance
with the Law of the State of Delaware (exclusive of conflicts of law
principles). State Courts within the State of Delaware and, more particularly to
the fullest extent such Court shall have subject matter jurisdiction over the
matter, the Court of Chancery of the State of Delaware, will have exclusive
jurisdiction over any and all disputes between the Parties, whether in law or
equity, arising out of or relating to this Agreement and the agreements,
instruments and documents contemplated hereby. The Parties consent to and agree
to submit to the jurisdiction of such Courts, PROVIDED, HOWEVER, that such
consent to jurisdiction is solely for the purpose referred to in this Section
10.10 and shall not be deemed to be a general submission to the jurisdiction of
such Courts or in the State of Delaware other than for such purpose. Each Party
hereby waives, and agrees not to assert in any such dispute, to the fullest
extent permitted by applicable Delaware Law, any claim that (i) such Party is
not personally subject to the jurisdiction of such Courts, (ii) such Party and
such Party's property is immune from any legal process issued by such Courts or
(iii) any Litigation commenced in such Courts is brought in an inconvenient
forum.


                                       52
<PAGE>   58


     10.11 COUNTERPARTS. This Agreement may be executed in one or more
counterparts, and by the Parties in separate counterparts, each of which when
executed shall be deemed to be an original but all of which taken together shall
constitute one and the same agreement.

                [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]


                                       53
<PAGE>   59


     IN WITNESS WHEREOF, the Parties have caused THIS AGREEMENT AND PLAN OF
MERGER to be executed as of the date first written above by their respective
officers thereunto duly authorized.



                                         CREATIVE BIOMOLECULES, INC.


                                         By /s/ Michael M. Tarnow
                                            ------------------------------------
                                         Name: Michael M. Tarnow
                                         Title: President


                                         REPROGENESIS, INC.


                                         By /s/ Daniel R. Omstead
                                            ------------------------------------
                                         Name: Daniel R. Omstead
                                         Title: President


                                         ONTOGENY, INC.


                                         By /s/ Doros Platika
                                            ------------------------------------
                                         Name: Doros Platika
                                         Title: President


                                         CURIS, INC.


                                         By /s/ Doros Platika
                                            ------------------------------------
                                         Name: Doros Platika
                                         Title: President



<PAGE>   60


                             INDEX OF DEFINED TERMS

Acquisition Proposal.................................................... 6.1(a)
Affiliate................................................................. 10.3
Affiliate Agreement....................................................... 7.13
Agreement.............................................................. Caption
Appraisal Shares.......................................................... 2.11
Bankruptcy and Equity Exception......................................... 3.3(a)
Breaching Party................................................. 9.3(b), 9.3(h)
Business Day.............................................................. 10.3
Certificate of Merger...................................................... 1.2
Certificates............................................................ 2.6(c)
Closing.................................................................... 2.8
Closing Date............................................................... 2.8
Code.................................................................. Recitals
Company................................................................ Caption
Company Balance Sheet................................................... 3.4(b)
Company Common Stock.................................................... 3.2(a)
Company Disclosure Schedule................................ Article III Caption
Company Employee Plans................................................. 3.14(a)
Company Financial Statements............................................ 3.4(a)
Company Intellectual Property Rights.................................... 3.9(b)
Company Material Adverse Effect............................................ 3.1
Company Material Contract................................................. 3.11
Company Meeting........................................................... 3.18
Company Preferred Stock................................................. 3.2(a)
Company Stock........................................................... 2.1(f)
Company Stock Option.................................................... 3.2(a)
Company Stock Plan...................................................... 3.2(a)
Company Warrants........................................................... 3.2
Confidentiality Agreements................................................. 5.3
Control................................................................... 10.3
Court..................................................................... 10.3
Creative Common Stock................................................... 2.1(a)
Creative Exchange Ratio................................................. 2.1(a)
Creative Merger Consideration........................................... 2.1(a)
Creative Voting Commitment............................................. 7.12(a)
Curis Certificate of Incorporation......................................... 4.1
Curis Material Adverse Effect.............................................. 4.1
DGCL.................................................................. Preamble
Effective Time............................................................. 1.2
Environmental Law...................................................... 3.13(b)
Equity Financing........................................................ 9.3(g)
ERISA.................................................................. 3.14(a)
ERISA Affiliate........................................................ 3.14(a)
Exchange Act............................................................ 3.3(c)
Exchange Agent............................................................ 10.3




                                       55
<PAGE>   61
Exchange Ratio.......................................................... 2.1(d)
Exchange Act Registration Statement..................................... 7.1(d)
Failing Party........................................................... 9.3(g)
FDA....................................................................... 3.10
GAAP.................................................................... 3.4(b)
GLP.................................................................... 3.16(b)
GMP.................................................................... 3.16(b)
Governmental Authority.................................................... 10.3
Hazardous Substance.................................................... 3.13(c)
HSR Act................................................................. 3.3(c)
Intellectual Property Rights............................................ 3.9(b)
IP Assignee............................................................. 3.9(e)
IPO..................................................................... 9.3(g)
IRS..................................................................... 3.7(b)
Joint Proxy Statement..................................................... 3.18
Knowledge................................................................. 10.3
Law....................................................................... 10.3
Lien...................................................................... 10.3
Litigation................................................................ 10.3
Merger................................................................ Preamble
Merger Consideration.................................................... 2.1(d)
Ongoing Clinical Programs............................................... 3.9(b)
Ontogeny Exchange Ratio................................................. 2.1(b)
Ontogeny Minimum Required Stockholder Vote............................. 7.12(b)
Ontogeny Merger Consideration........................................... 2.1(b)
Ontogeny Common Stock................................................... 2.1(b)
Ontogeny Preferred Stock................................................ 2.1(b)
Ontogeny Required Stockholder Vote..................................... 7.12(a)
Order..................................................................... 10.3
Person.................................................................... 10.3
Public Company ............................................................ 3.1
Registration Statement.................................................... 3.18
Regulation................................................................ 10.3
Representatives......................................................... 6.1(a)
Reprogenesis Common Stock............................................... 2.1(c)
Reprogenesis Exchange Ratio............................................. 2.1(c)
Reprogenesis Fully Diluted Merger Consideration......................... 2.1(c)
Reprogenesis Merger Consideration....................................... 2.1(c)
Reprogenesis Preferred Stock............................................ 2.1(c)
Reprogenesis Required Stockholder Vote................................. 7.12(a)
Reprogenesis Series A Consideration..................................... 2.1(c)
Rule 145 ................................................................. 7.13
SEC........................................................................ 3.3
Section 262............................................................... 2.11
Securities Act.......................................................... 2.3(b)
Stipulated Expenses..................................................... 9.3(d)
Stockholder Agreement................................................. Preamble




                                       56
<PAGE>   62

Subsidiary, Subsidiaries.................................................. 10.3
Superior Proposal....................................................... 6.1(b)
Surviving Company.......................................................... 1.1
Tax..................................................................... 3.7(a)
Taxes................................................................... 3.7(a)
Tax Returns............................................................. 3.7(b)
Termination Fee......................................................... 9.3(b)
Third Party Licenses.................................................... 9.3(a)
Voting Stock.............................................................. 10.3






                                       57
<PAGE>   63
                                  SCHEDULE 1.5
                                  ------------

                             DIRECTORS AND OFFICERS
                             ----------------------


DIRECTORS:
- ----------


     CLASS I:     James R. McNab, Jr.
                  James Tobin
                  Doros Platika


     CLASS II:    Douglas A. Melton
                  Michael Rosenblatt
                  [Person as yet to be determined]

     CLASS III:   Ruth B. Kunath
                  Martyn Greenacre


OFFICERS:
- ---------

The Officers at the Effective Time shall be appointed by the Board of Directors.






                                       58
<PAGE>   64
                                   EXHIBIT A
                                   ---------

                         FORM OF STOCKHOLDER AGREEMENT


                                                     February ___, 2000


Creative Biomolecules, Inc.     Reprogenesis, Inc.         Ontogeny, Inc
101 Huntington Ave.             21 Erie Street             45 Moulton Street
Boston, MA  02111               Cambridge, MA  02139       Cambridge, MA  02138
Attention: President            Attention: President       Attention: President



Re:  Stockholder Agreement
     ---------------------


Gentlemen:

         The undersigned (the "Stockholder") owns of record and beneficially the
number of shares (the "Owned Shares") of common stock [and/or preferred stock]
of [Name of Company], a [Delaware] [Texas] corporation ("Company"), as set forth
below. [On even date herewith], the Company, _______ and ________ (the "Other
Companies") and Curis [intend to enter] into an Agreement and Plan of Merger
(the "Merger Agreement") with respect to the merger (the "Merger") of the
Company and the Other Companies with and into Curis. Such Company common stock
[and/or preferred stock] will be converted in the Merger into shares of the
common stock, par value $.01 per share, of Curis (the "Surviving Company Common
Stock"). The Stockholder wishes to facilitate the proposed Merger, acknowledges
that the proposed Merger will benefit the Stockholder and agrees that the Other
Companies [would not enter into the Merger Agreement] unless the Stockholder
enters into this Agreement. For all purposes of this Agreement, the term "Owned
Shares" shall include any additional shares of Company capital stock as to which
the Stockholder acquires beneficial ownership after the execution hereof.

         In consideration of the foregoing, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, and
intending to be legally bound hereby, the Stockholder agrees as follows:

         1.       The Stockholder irrevocably and unconditionally agrees that
he, she or it (a) will vote all of the Owned Shares in favor of the Merger
Agreement and the Merger at any meeting or meetings of the Company's
stockholders called to vote upon the Merger Agreement and the Merger and (b)
will not vote such shares (or otherwise provide a proxy or consent or a voting
agreement with respect thereto) in favor of any other Acquisition Proposal (as
defined in the Merger Agreement) [and (c) will vote to amend the
Certificate/Articles of Incorporation of the Company as contemplated by Section
8.1(h) of the Merger Agreement.]





<PAGE>   65
         2.       The Stockholder agrees that he, she or it will not (a)
directly or indirectly, sell, transfer, pledge, assign or otherwise dispose of,
or enter into any contract, option, commitment or other arrangement or
understanding with respect to the sale, transfer, pledge, assignment or other
disposition of, any of the Owned Shares or (b) take any action or omit to take
any action which would prohibit, prevent or preclude Stockholder from performing
its obligations under this Agreement.

         3.       The Stockholder agrees that irreparable damage would occur in
the event that any of the provisions of this Agreement were not performed by it
in accordance with their specific terms or were otherwise breached. It is
accordingly agreed that the Company and each other Company shall be entitled to
an injunction or injunctions to prevent breaches of this Agreement by the
Stockholder and to enforce specifically the terms and provisions hereof in any
court of the United States or any state having jurisdiction, this being in
addition to any other remedy to which it is entitled at law or in equity, and
that the Stockholder waives the posting of any bond or security in connection
with any proceeding related thereto.

         4.       This Agreement may be executed in one or more counterparts,
each of which shall be deemed to constitute an original. This Agreement shall
become effective when one counterpart signature page has been signed by the
Stockholder and delivered to the Company (which delivery may be by facsimile).

         5.       The Stockholder agrees to execute and deliver all such further
documents, certificates and instruments and take all such further reasonable
action as may be necessary or appropriate, in order to consummate the
transactions contemplated hereby. The Stockholder hereby agrees not to engage in
any transaction involving any securities of the Other Companies that would
violate applicable securities laws.

         6.       Notwithstanding anything in this Agreement to the contrary,
the Company and the Other Companies understand and agree that (i) Owned Shares
may be subject to liens, encumbrances or restrictions (other than those relating
to voting) arising in connection with pledges of Owned Shares by the Stockholder
or its affiliates that exist as of the date hereof and (ii) any transfer of
Owned Shares pursuant to any bona fide foreclosure under any such pledge shall
not violate this Agreement.

         7.       The Stockholder represents and warrants to the Company and the
Other Companies that:

                  (a)      the Stockholder has all necessary power and authority
to execute this letter agreement including the irrevocable proxy attached
hereto;

                  (b)      the Stockholder owns or controls (regardless of in
what capacity) the number of Owned Shares set forth below free from any lien,
encumbrance or restriction whatsoever (except as otherwise permitted by Section
6 above) and with full power to vote the Owned Shares without the consent or
approval of any other person;



                                       2
<PAGE>   66

                  (c)      this letter agreement and the attached proxy have
been duly executed and delivered by the Stockholder and each constitutes a valid
and binding agreement of the Stockholder, enforceable in accordance with its
terms; and

                  (d)      neither the execution nor delivery of this letter
agreement and the attached proxy by the Stockholder will (i) require the
consent, waiver, approval, license or authorization, or any filing with, any
person or public authority, (ii) with or without the giving of notice or the
lapse of time, or both, conflict with or constitute a violation of, or default
under, or give rise to any right of acceleration under any indenture, contract,
commitment, agreement, arrangement or other instrument of any kind to which the
Stockholder is a party or by which the Stockholder is bound, or (iii) violate
any applicable law, rule, regulation, judgment, order or decree of any
governmental instrumentality or court having jurisdiction over the Stockholder.

         8.       The Agreement shall terminate on the termination of the Merger
Agreement or at the Effective Time of the Merger provided for in the Merger
Agreement, as the case may be.

         IN WITNESS WHEREOF, the parties have executed this agreement as of the
date and year first above written.



                                        STOCKHOLDER:



                                        Name:_______________________________

                                        Address:____________________________

                                                ____________________________

                                                ____________________________

                                                ____________________________



                                        Spouse (if applicable)


                                        Name:_______________________________


                                        Number of Shares of
                                        Common Stock _______________________

                                        [Number of Shares of Series A
                                        Preferred Stock ____________________

                                        Number of Shares of Series B
                                        Preferred Stock ____________________]

                                        [Number of Shares of Series C
                                        Preferred Stock ____________________




                                       3
<PAGE>   67

                                        Number of Shares of Series C-1
                                        Preferred Stock ____________________]

                                        [Number of Shares of Series D
                                        Preferred Stock ____________________

                                        Number of Shares of Series E
                                        Preferred Stock ____________________]

                                        [Number of Shares of Series F
                                        Preferred Stock ____________________

                                        Number of Shares of Series G
                                        Preferred Stock ____________________]





                                        4

<PAGE>   68
                            IRREVOCABLE PROXY FOR THE
                        STOCKHOLDER AGREEMENT OF COMPANY


By its execution hereof and in order to secure the obligations of the
undersigned set forth in the Stockholder Agreement ("Stockholder Agreement")
dated February ____, 2000, by and among ___________ (the "Company"), the Other
Companies and the undersigned, the undersigned hereby irrevocably constitutes
and appoints the President and the Secretary of each Other Company, and each of
such officers singly, as its true and lawful attorneys-in-fact, to : (1) vote,
in accordance with the Stockholder Agreement, all shares of capital stock of the
Company which the undersigned may be entitled to vote upon the matters set forth
in the Stockholder Agreement at any annual or special meeting of the
stockholders of the Company (but not to vote such shares on any other matter);
(2) to exercise written consent in lieu of voting with respect to the matters
set forth in clause (1); and (3) to execute, acknowledge, swear to and file in
the undersigned's name, place and stead any consent, approval, or other
documents to be executed by the stockholders in connection with the items in
clauses (1) and (2). The Proxy hereby granted is irrevocable and shall be deemed
coupled with an interest in the Stockholder Agreement for the term stated
therein and it shall survive the undersigned's insolvency.

         IN WITNESS WHEREOF, the undersigned has executed this Irrevocable Proxy
this ____ day of February, 2000.


                                        Name:_______________________________

                                        Address:____________________________

                                                ____________________________

                                                ____________________________

                                                ____________________________



                                        Spouse (if applicable)

                                        Name:_______________________________





                                       5
<PAGE>   69
                                   EXHIBIT B
                                   ---------

                                    FORM OF

                             CERTIFICATE OF MERGER

                                       OF

                                    EACH OF

              CREATIVE BIOMOLECULES, INC., A DELAWARE CORPORATION,

                   ONTOGENY, INC., A DELAWARE CORPORATION AND

                    REPROGENESIS, INC., A TEXAS CORPORATION

                                 WITH AND INTO

                      CURIS, INC., A DELAWARE CORPORATION

                              ********************

         Pursuant to Section 252 of the General Corporation Law of the State of
Delaware, the undersigned corporations organized and existing under and by
virtue of the General Corporation Law of the State of Delaware and the Texas
Business Corporation Act, DO HEREBY CERTIFY:

         FIRST: That the name and state of incorporation of each of the
constituent corporations are as follows:

      NAME                                             STATE OF INCORPORATION
      ----                                             ----------------------

1.    Creative Biomolecules, Inc.                              Delaware

2.    Ontogeny, Inc.                                           Delaware

3.    Reprogenesis, Inc.                                       Texas

4.    Curis, Inc.                                              Delaware

         SECOND: That an Agreement and Plan of Merger dated as of February 14,
2000 by and among Creative Biomolecules, Inc., Ontogeny, Inc., Reprogenesis,
Inc. and Curis, Inc. has been approved, adopted, certified, executed and
acknowledged by each of the constituent corporations in accordance with the
requirements of Section 252 of the General Corporation Law of the state of
Delaware.



<PAGE>   70
         THIRD: That the name of the surviving corporation of the merger is
Curis, Inc. (the "Surviving Corporation").

         FOURTH: That the Certificate of Incorporation of CURIS shall be the
Certificate of Incorporation of the Surviving Corporation.

         FIFTH: That the executed copy of the Agreement and Plan of Merger is on
file at an office of the Surviving Corporation. The address of such office is:

                                Curis, Inc.
                                _________________________

                                _________________________


         SIXTH: That a copy of the Agreement and Plan of Merger will be
furnished by the Surviving Corporation, on request and without cost, to any
stockholder of the constituent corporations.

         SEVENTH: That the authorized capital stock of Reprogenesis, Inc. is as
follows:

         Common Stock:      30,084,501
         Preferred Stock:    7,747,153
                Series A:                 2,702,702
                Series B:                 5,044,451
         Total:             37,831,654

         IN WITNESS WHEREOF, the undersigned, being the President of CURIS, does
hereby execute this Certificate of Merger and so certifies, affirms and
acknowledges under penalties of perjury that this is his free act and deed and
that the facts stated herein are true, this _____________, 2000.


                                            [___________________________]


                                            By: ________________________________

                                                _____________________, President






                                       2
<PAGE>   71
                                   EXHIBIT C
                                   ---------

                               ARTICLES OF MERGER

                                     merging

                               REPROGENESIS, INC.
                             (a Texas corporation),

                                 ONTOGENY, INC.
                            (a Delaware corporation),

                                       and

                           CREATIVE BIOMOLECULES, INC.
                            (a Delaware corporation)

                                  with and into

                                   CURIS, INC.
                            (a Delaware corporation)


         Pursuant to the provisions of Article 5.04 of the Texas Business
Corporation Act (the "TBCA"), Reprogenesis, Inc., a Texas corporation (the
"Company"), Ontogeny, Inc., a Delaware corporation ("Ontogeny"), Creative
Biomolecules, Inc., a Delaware corporation ("Creative"), and Curis, Inc., a
Delaware corporation (the "Surviving Corporation"), hereby adopt the following
Articles of Merger for the purpose of effecting the merger (the "Merger") of the
Company, Ontogeny and Creative with and into the Surviving Corporation, with the
Surviving Corporation continuing in existence following the Merger as the
surviving corporation:

         FIRST: The name and state of incorporation of each party (the
"Constituent Entities") to the Agreement and Plan of Merger attached as Exhibit
A (the "Agreement and Plan of Merger") are as follows:

         NAME                                           STATE OF INCORPORATION
         ----                                           ----------------------

         Reprogenesis, Inc.                             Texas
         Ontogeny, Inc.                                 Delaware
         Creative Biomolecules, Inc.                    Delaware
         Curis, Inc.                                    Delaware

         SECOND: The Agreement and Plan of Merger was approved by the
stockholders of the Company in the manner required by Article 5.03 of the TBCA
and by the stockholders of each of Ontogeny, Creative and the Surviving
Corporation in the manner required by Section 252 of the Delaware General
Corporation Law.



<PAGE>   72
         THIRD: An executed copy of the Agreement and Plan of Merger is on file
at the principal place of business of the Surviving Corporation at 45 Moulton
Street, Cambridge, Massachusetts 02138, and a copy of the Agreement and Plan of
Merger will be furnished by such entity, on written request and without cost, to
any shareholder of any of the Constituent Entities.

         FOURTH: The outstanding capital stock of the Company consists of
14,744,524 shares of common stock, par value $0.01 per share (the "Company
Common Stock"), 2,702,702 shares of Series A Convertible Preferred Stock, par
value $0.01 per share (the "Company Series A Preferred Stock") and 4,729,134
shares of Series B Convertible Preferred Stock, par value $0.01 per share (the
"Company Series B Preferred Stock" and, together with the Company Series A
Preferred Stock, the "Company Preferred Stock"). ______ shares of the Company
Common Stock and the Company Preferred Stock were voted in favor of and _______
shares of the Company Common Stock and the Company Preferred Stock were voted
against the Merger pursuant to the terms and conditions of the Agreement and
Plan of Merger. ______ of the shares of the Company Series A Preferred Stock and
_______ shares of the Company Series B Preferred Stock were voted in favor of
and _______ shares of the Company Series A Shares and _____ shares of Company
Series B Shares were voted against the Merger pursuant to the terms and
conditions of the Agreement and Plan of Merger.

         FIFTH: The outstanding capital stock of Creative consists of 37,138,705
shares of common stock, par value $0.01 per share (the "Creative Common Stock").
__________ shares of the Creative Common Stock were voted in favor of and
________ shares of Creative Common Stock were voted against the Merger pursuant
to the terms and conditions of the Agreement and Plan of Merger.

         SIXTH: The outstanding capital stock of Ontogeny consists of 2,892,815
shares of common stock, par value $0.01 per share (the "Ontogeny Common Stock"),
4,853,334 shares of Series A Convertible Preferred Stock, par value $0.01 per
share (the "Ontogeny Series A Preferred Stock"), 7,447,223 shares of Series B
Convertible Preferred Stock, par value $0.01 per share (the "Ontogeny Series B
Preferred Stock"), 400,000 shares of Series C Convertible Preferred Stock, par
value $0.01 per share (the "Ontogeny Series C Preferred Stock"), 800,000 shares
of Series C-1 Convertible Preferred Stock, par value $0.01 per share (the
"Ontogeny Series C-1 Preferred Stock"), 600,000 shares of Series D Convertible
Preferred Stock, par value $0.01 per share (the "Ontogeny Series D Preferred
Stock"), 10,000,000 shares of Series E Convertible Preferred Stock, par value
$0.01 per share (the "Ontogeny Series E Preferred Stock"), 8,379,593 shares of
Series F Convertible Preferred Stock, par value $0.01 per share (the "Ontogeny
Series F Preferred Stock"), and 400,000 shares of Series G Convertible Preferred
Stock, par value $0.01 per share (the "Ontogeny Series G Preferred Stock" and,
together with the Ontogeny Series A Preferred Stock, Ontogeny Series B Preferred
Stock, Ontogeny Series C Preferred Stock, Ontogeny Series C-1 Preferred Stock,
Ontogeny Series D Preferred Stock, Ontogeny Series E Preferred Stock and
Ontogeny Series F Preferred Stock, the "Ontogeny Preferred Stock"). _______
shares of the Ontogeny Common Stock and Ontogeny Preferred Stock were voted in
favor of and _______ shares of Ontogeny Common Stock and Ontogeny Preferred
Stock were voted against the Merger pursuant to the terms and conditions of the
Agreement and Plan of Merger. _________ shares of Ontogeny Series A Preferred
Stock, Ontogeny Series B Preferred Stock, Ontogeny Series E Preferred Stock and
Ontogeny Series F Preferred Stock were voted in favor of and ________ shares of
Ontogeny Series A Preferred Stock, Ontogeny Series B Preferred Stock, Ontogeny
Series E Preferred Stock and Ontogeny Series F



                                       2
<PAGE>   73

Preferred Stock were voted against the Merger pursuant to the terms and
conditions of the Agreement and Plan of Merger.

         SEVENTH: The outstanding capital stock of the Surviving Corporation
consists of 300 shares of common stock, par value $0.01 per share ("Surviving
Corporation Common Stock"). Each of the Company, Ontogeny and Creative owns 100
shares of the Surviving Corporation's Common Stock. All shares of Surviving
Corporation Common Stock were voted in favor of the Merger pursuant to the terms
and conditions of the Agreement and Plan of Merger.

         EIGHTH: The Agreement and Plan of Merger and the performance of its
terms were duly authorized by all action required by the laws of the State of
Delaware and by the constituent documents of each of Ontogeny, Creative and the
Surviving Corporation.

         NINTH: The Agreement and Plan of Merger and the performance of its
terms were duly authorized by all actions required by the laws of the State of
Texas and by the constituent documents of the Company.





                                       3
<PAGE>   74

         IN WITNESS WHEREOF, each of the undersigned corporations has caused
these Articles of Merger to be executed on its behalf on ________________, 2000.




                                        REPROGENESIS, INC.
                                        a Texas corporation


                                        By:
                                            ----------------------------------
                                            Name:
                                            Title:


                                        ONTOGENY, INC.
                                        a Delaware corporation


                                        By:
                                            ----------------------------------
                                            Name:
                                            Title:


                                        CREATIVE BIOMOLECULES, INC.
                                        a Delaware corporation


                                        By:
                                            ----------------------------------
                                            Name:
                                            Title:


                                        CURIS, INC.
                                        a Delaware corporation


                                        By:
                                            ----------------------------------
                                            Name:
                                            Title:





                                       4
<PAGE>   75
                                   EXHIBIT D
                                   ---------

                   FORM OF CURIS CERTIFICATE OF INCORPORATION
                   ------------------------------------------

                          CERTIFICATE OF INCORPORATION
                                       OF
                                  CURIS, INC.


         FIRST: The name of this corporation (the "Corporation") is Curis, Inc.

         SECOND: The address of the registered office of the Corporation in the
State of Delaware is 1209 Orange Street, Wilmington, Delaware 19801, County of
New Castle, and the name of its registered agent at such address is The
Corporation Trust Company.

         THIRD: The purpose for which the Corporation is organized is to engage
in any lawful act or activity for which corporations may be organized under the
General Corporation Law of the State of Delaware.

         FOURTH: The Corporation is authorized to issue two classes of capital
stock, one of which is designated as common stock, $.01 par value per share
("Common Stock"), and the other of which is designated as preferred stock, $.01
par value per share ("Preferred Stock"). The total number of shares of both
classes of capital stock that the Corporation shall have authority to issue is
145 million shares, consisting of 125 million shares of Common Stock and 20
million shares of Preferred Stock. The Preferred Stock may be issued from time
to time in one or more series as set forth in Section (b) of this Article
FOURTH. The following is a statement of the designations and the powers,
preferences and rights of, and the qualifications, limitations or restrictions
applicable to, each class of capital stock of the Corporation.

         (a)      COMMON STOCK

                  (1)      General. The voting, dividend and liquidation rights
         of holders of Common Stock are subject to and qualified by the rights
         of holders of Preferred Stock of any series as may be designated in any
         resolution or resolutions providing for the issue of such series as may
         be adopted by the board of directors as hereinafter provided.

                  (2)      Voting. Holders of Common Stock are entitled to one
         vote for each share held at all meetings of stockholders. The number of
         authorized shares of Common Stock may be increased or deceased (but not
         below the number of shares thereof then outstanding) by the affirmative
         vote of the holders of a majority of the capital stock of the
         Corporation entitled to vote, irrespective of the provisions of Section
         242(b)(2) of the General Corporation Law of the State of Delaware.

                  (3)      Dividends. Dividends may be declared and paid on
         Common Stock from funds lawfully available therefor, as and when
         determined by the board of directors and subject to any preferential
         dividend rights of any series of Preferred Stock then outstanding.




<PAGE>   76

                  (4)      Liquidation. Upon the dissolution or liquidation of
         the Corporation, whether voluntary or involuntary, holders of Common
         Stock will be entitled to receive all assets of the Corporation
         available for distribution to stockholders of the Corporation, subject
         to any preferential rights of any series of Preferred Stock then
         outstanding.

         (b)      PREFERRED STOCK

                  (1)      Issuance. Preferred Stock may be issued from time to
         time in one or more series, each of which series shall have such terms
         as are set forth herein and in any resolution or resolutions providing
         for the issue of such series as may be adopted by the board of
         directors as hereinafter provided. Any shares of Preferred Stock that
         may be redeemed, purchased or acquired by the Corporation may be
         reissued except as otherwise expressly provided in this Certificate of
         Incorporation or provided by law. Different series of Preferred Stock
         shall not be construed to constitute different classes of capital stock
         for the purposes of voting by classes unless expressly provided.

                  (2)      Authority of Board. Authority is hereby expressly
         granted to the board of directors to provide for the issuance of
         Preferred Stock from time to time in one or more series, and in
         connection with the creation of any such series, to determine and fix
         such voting powers, full or limited, or no voting powers, and such
         designations, preferences and relative participating, optional or other
         special rights thereof, and qualifications, limitations or restrictions
         applicable thereto, as shall be stated and expressed in such
         resolutions, all to the full extent now or hereafter permitted by the
         General Corporation Law of the State of Delaware. Without limiting the
         generality of the foregoing, a resolution or resolutions providing for
         issuance of any series of Preferred Stock may provide for dividend
         rights, conversion rights, redemption privileges and liquidation
         preferences applicable to such series and may provide that such series
         shall rank superior, equal or junior to the Preferred Stock of any
         other series, in each case except as otherwise expressly provided in
         this Certificate of Incorporation or as provided by law. Except as
         otherwise provided in this Certificate of Incorporation, no vote of
         holders of Common Stock or holders of Preferred Stock shall be a
         prerequisite to the designation or issuance of any shares of any series
         of Preferred Stock authorized by and complying with the conditions of
         this Certificate of Incorporation.

         FIFTH: Special meetings of stockholders may be called at any time by
the Chairman of the Board, the Chief Executive Officer (or if there is no Chief
Executive Officer, the President) or the board of directors. Business transacted
at any special meeting of stockholders shall be limited to matters relating to
the purpose or purposes stated in the notice of the general meeting.

         SIXTH: No director shall be personally liable to the Corporation or to
any of its stockholders for monetary damages arising out of such director's
breach of fiduciary duty as a director of the Corporation, except to the extent
that the elimination or limitation of such liability is not permitted by the
General Corporation Law of the State of Delaware, as the same exists or may
hereafter be amended. No amendment to or repeal of the provisions of this
Article SIXTH shall deprive any director of the Corporation of the benefit of
the provisions of this Article SIXTH with respect to any act or failure to act
of any director occurring prior to such amendment or repeal.



                                       2
<PAGE>   77
         SEVENTH: In furtherance of and not in limitation of powers conferred by
statute, it is further provided that:

         (a)      AMENDMENT OF BY-LAWS

                  Subject to the limitations and exceptions, if any, contained
         in the by-laws of the Corporation, the by-laws may be adopted, amended
         or repealed by the board of directors.

         (b)      ELECTION OF DIRECTORS

                  Elections of directors need not be by written ballot unless
         otherwise provided in the by-laws of the Corporation.

         (c)      LOCATION OF CORPORATE BOOKS

                  Subject to any applicable requirements of the General
         Corporation Law of the State of Delaware, the books of the Corporation
         may be kept outside the State of Delaware at such location or locations
         as may be designated from time to time by the board of directors or in
         the by-laws of the Corporation.

         EIGHTH: The Corporation shall indemnify each person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the Corporation), by
reason of the fact that such person is or was, or has agreed to become, a
director or officer of the Corporation, or is or was serving or has agreed to
serve, at the request of the Corporation, as a director, officer or trustee of,
or in a similar capacity with, another corporation (including any partially or
wholly owned subsidiary of the Corporation), partnership, joint venture, trust
or other enterprise (including any employee benefit plan), against expenses
(including attorneys' fees), judgments, fines and amounts paid in settlement
actually and reasonably incurred in connection with any such action, suit or
proceeding to the maximum extent permitted by the General Corporation Law of
Delaware. The foregoing right of indemnification shall in no way be exclusive of
any other rights of indemnification to which any such director or officer may be
entitled, under any by-law, agreement, vote of directors or stockholders or
otherwise. No amendment to or repeal of the provisions of this paragraph shall
deprive a person of the benefit of this paragraph with respect to any act or
failure to act of such person occurring prior to such amendment or repeal.

         NINTH: Whenever a compromise or arrangement is proposed between the
Corporation and its creditors or any class of them or between the Corporation
and its stockholders or any class of them, any court of equitable jurisdiction
within the State of Delaware may, on the application in a summary way of the
Corporation or of any creditor or stockholder thereof or on the application of
any receiver or receivers appointed for the Corporation under Section 291 of
Title 8 of the Delaware Code or on the application of trustees in dissolution or
of any receiver or receivers appointed for the Corporation under Section 279 of
Title 8 of the Delaware Code, order a meeting of the creditors or class of
creditors, and/or of the stockholders or class of stockholders of the
Corporation, as the case may be, to be summoned in such manner as the said court
directs. If a majority in number representing three-fourths in value



                                       3
<PAGE>   78
of the creditors or class of creditors, and/or of the stockholders or class of
stockholders of the Corporation, as the case may be, agree to any compromise or
arrangement and to any reorganization of the Corporation as a consequence of
such compromise or arrangement, the said compromise or arrangement and the said
reorganization shall, if sanctioned by the court to which the said application
has been made, be binding on all the creditors or class of creditors, and/or on
all the stockholders or class of stockholders, of the Corporation, as the case
may be, and also on the Corporation.

         TENTH: The Corporation reserves the right to amend, alter, change or
repeal any provision contained in this Certificate of Incorporation in the
manner now or hereafter prescribed by the General Corporation Law of the State
of Delaware and this Certificate of Incorporation, and all rights conferred upon
stockholders herein are granted subject to this reservation. Notwithstanding any
provision of law, any other provision of this Certificate of Incorporation or
any provision of the by-laws of the Corporation, the affirmative vote of the
holders of three- fourths of the shares of capital stock of the Corporation
issued and outstanding and entitled to vote shall be required to amend or
repeal, or to adopt any provision inconsistent with, any provision of Article
FIFTH or this Article TENTH.

         ELEVENTH: The name of the sole incorporator of the Corporation is
Jonathan H. Hulbert and his mailing address is c/o Foley, Hoag & Eliot LLP, One
Post Office Square, Boston, Massachusetts 02109.

         IN WITNESS WHEREOF, I have hereunto set my hand as of February 14,
2000.


                                             ---------------------------------
                                             Jonathan H. Hulbert
                                             Sole Incorporator





                                       4
<PAGE>   79
                                   EXHIBIT E
                                   ---------

                          FORM OF AFFILIATE AGREEMENT
                          ---------------------------

                                                   _________ ___, 2000



Curis, Inc.
____________________________

____________________________
Attention: President


[Name of Company]
____________________________

____________________________
Attention: President



Ladies and Gentlemen:

         I/We have been advised that I/we might be considered to be an
"affiliate" of [Company Name] (the "Company") for purposes of Rule 145 ("Rule
145") under the Securities Act of 1933, as amended (the "Securities Act"), as
promulgated by the Securities and Exchange Commission (the "SEC").

         ____, ____, ____ ("Curis") and the Company have entered into an
Agreement and Plan of Merger dated as of the 14th day of February, 2000 (the
"Plan of Merger"). Upon consummation of the transactions contemplated by the
Plan of Merger (the "Merger"), I/we will receive shares of capital stock of
Curis for all of the shares of capital stock of the Company owned by me/us or as
to which I/we may be deemed a beneficial owner. I/We own _____________ shares of
the common stock, [$.01] par value per share, of the Company (the "Company's
Common Stock") [and/or ____________shares of Preferred Stock, [$.01] par value
per share (the "Preferred Stock")] [and/or options to acquire _________ shares
of the Company's Common Stock (the "Options")] [and/or warrants to acquire
_________ shares of the Company's Common Stock (the "Warrants")]. The Company's
Common Stock [the Company's Preferred Stock] will be converted in the Merger
into shares of the common stock, $.01 par value per share, of Curis (the "Curis
Common Stock") as described in the Plan of Merger. The shares of Curis Common
Stock received by me/us in the Merger are hereinafter collectively referred to
as the "Exchange Stock". This agreement is hereinafter referred to as the
"Affiliate Agreement".

         I/We represent and warrant to, and agree with, ____, ____, Curis and
the Company that:

         A.       I/We have read this Affiliate Agreement and the Plan of Merger
and have discussed their requirements and other applicable limitations upon
my/our ability to sell, transfer or otherwise dispose of the Exchange Stock, to
the extent I/we felt necessary, with my/our counsel or counsel for the Company.


<PAGE>   80
         B.       I/We understand that my/our resale of Exchange Stock issued to
me/us in the Merger will be subject to certain restrictions on transfer in
accordance with Rule 145 under the Securities Act, and in connection therewith
I/we agree not to offer, sell, pledge, transfer or otherwise dispose of any of
such shares of Exchange Stock unless at such time either: (i) such transaction
shall be permitted pursuant to the provisions of Rule 145; (ii) I/we shall have
furnished to Curis an opinion of counsel, satisfactory to Curis, to the effect
that no registration under the Securities Act would be required in connection
with the proposed offer, sale, pledge, transfer or other disposition; (iii) a
registration statement under the Securities Act covering the proposed offer,
sale, pledge, transfer or other disposition shall be effective under the
Securities Act; or (iv) an authorized representative of the SEC shall have
rendered written advice to me/us to the effect that the SEC will take no action,
or that the staff of the SEC will not recommend that the SEC take action, with
respect to the proposed offer, sale, pledge transfer or other disposition if
consummated.

         C.       I/We understand that all certificates representing the
Exchange Stock delivered to me/us pursuant to the Merger shall, until the
occurrence of one of the events referred to in paragraph B. above, bear a legend
substantially as follows:

         "The shares represented by this certificate may not be offered, sold,
pledged, transferred or otherwise disposed of except in accordance with the
requirements of Rule 145 of the Securities Act of 1933, as amended."

         D.       I/We also understand and agree that Curis, in its discretion
and in a manner consistent with the legend set forth above, may cause stop
transfer orders to be placed with its transfer agent with respect to the
certificates for the shares of Exchange Stock which are required to bear the
foregoing legend.

         E.       I/we agree to comply with the prohibition described in Section
6.1(a) of the Agreement.

         It is understood and agreed that this Affiliate Agreement shall
terminate and be of no further force and effect if the Plan of Merger is
terminated pursuant to the terms thereof.

         This Affiliate Agreement shall be binding on my/our heirs, legal
representatives and successors.




                                        Very truly yours,



                                        ----------------------------------
                                        Name:






                                       2
<PAGE>   81

                                   EXHIBIT F
                                   ---------

                            FORM OF LOCK-UP AGREEMENT
                            -------------------------

                                                  ______________, 2000



Curis, Inc. (the "Surviving Company")
____________________________________

____________________________________


Re: Proposed Merger


Ladies & Gentlemen:

         The undersigned is an owner of record or beneficially of certain shares
of common stock and/or preferred stock of [Name of Company] (the "Company") or
securities convertible into or exchangeable or exercisable for common stock. It
is contemplated that the Company will merge (the "Merger") with and into the
Surviving Company pursuant to an Agreement and Plan of Merger (the "Agreement")
dated as of February 14, 2000. Pursuant to the Merger, each outstanding share of
capital stock of the Company will be exchanged and converted into shares of
Common Stock of the Surviving Company (the "Common Stock"), and securities
convertible into or exchangeable or exercisable for common stock of the Company
will become convertible into or exchangeable or exercisable for Common Stock,
all as more specifically provided in the Agreement. The undersigned wishes to
facilitate the proposed Merger and acknowledges that the proposed Merger will be
of benefit to the undersigned.

         In consideration of the foregoing, the undersigned hereby agrees that
the undersigned will not, until the earlier of the end of the [90] [180] day
period following from the Effective Time (as defined in the Agreement), or
termination of the Agreement in accordance with its terms, (1) offer, sell,
contract to sell, grant any option to purchase or acquire any right to dispose
or otherwise dispose for value, any shares of Common Stock or any securities
convertible into, or exchangeable for, or warrants to purchase, any shares of
Common Stock (including, without limitation, Common Stock which may be deemed to
be beneficially owned by the undersigned in accordance with the rules and
regulations promulgated under the federal securities laws), or (2) enter into
any swap, short sale, hedge or other agreement that transfers, in whole or in
part, the economic risk of ownership of the Common Stock, whether any such
transaction described in clause (1) or (2) above is to be settled by delivery of
Common Stock or such other securities, in cash or otherwise, other than (a)
pursuant to bona fide gifts, (b) transfers which will not result in any change
in beneficial ownership, including, but not limited to, pro rata partnership
distributions and transfers into trusts for the benefit of the original holder
or (c) pursuant to the laws of testamentary or intestate descent, provided,
that, in any of the foregoing circumstances the donees or transferees agree, in
writing, to be bound by the provisions of this Lock Up Agreement. The
undersigned also agrees and consents to the entry of stop transfer instructions
imposed by the Surviving Company with the Surviving Company's transfer agent and
registrar against the transfer of shares of Common Stock or securities
convertible into or exchangeable or exercisable for Common Stock held by the
undersigned except in compliance with the foregoing restrictions.


<PAGE>   82

         This agreement is irrevocable and will be binding on the undersigned
and the respective successors, heirs, personal representatives, and assigns of
the undersigned.



                                             Very truly yours,


                                             ----------------------------------
                                             Printed Name of Holder


                                             By:
                                                 ------------------------------
                                                            Signature



                                             ----------------------------------
                                             Printed Name of Person Signing
                                             (and indicate capacity of person
                                             signing if signing as custodian,
                                             trustee, or on behalf of an entity)


                                             Dated:   ______________, 2000





                                       2
<PAGE>   83
                                   EXHIBIT G
                                   ---------

                       FORM OF CERTIFICATE OF AMENDMENT TO
                          CERTIFICATE OF INCORPORATION

                            CERTIFICATE OF AMENDMENT
                                       TO
                AMENDED AND RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                                 ONTOGENY, INC.


         ONTOGENY, INC. (the "Corporation"), a corporation organized and
existing under and by virtue of the General Corporation Law of the State of
Delaware, DOES HEREBY CERTIFY:

FIRST:   That the Board of Directors of the Corporation duly adopted resolutions
         proposing and declaring advisable that the Amended and Restated
         Certificate of Incorporation of the Corporation be amended in the
         manner set forth below and that said amendments be submitted to the
         stockholders of the Corporation for their consideration.

SECOND:  That in lieu of a meeting and vote of stockholders, the stockholders
         have given written consent to said amendments in accordance with the
         provisions of Sections 228 and 242 of the General Corporation Law of
         the State of Delaware.

THIRD:   That the Certificate of Incorporation of the Corporation, as
         previously amended and restated, is further amended as follows:

                              1. The following sentence shall be inserted at the
                        end of Subsection C.2(c) of Article FOURTH:

                        "Notwithstanding the foregoing, the provisions of this
                        Subsection 2(c) shall not apply to a merger of the
                        Corporation with and into Curis, Inc., a Delaware
                        corporation, (the "Excluded Merger") pursuant to the
                        Agreement and Plan of Merger dated as of February 14,
                        2000 among the Corporation, Curis, Inc., Creative
                        Biomolecules, Inc., a Delaware corporation, and
                        Reprogenesis, Inc., a Texas corporation, as such
                        agreement may be amended from time to time in accordance
                        with the provisions thereof, and the Excluded Merger
                        shall not be deemed to be a liquidation, dissolution or
                        winding up of the Corporation."

                              2. The following sentence shall be inserted at the
                        end of Subsection C.4(i) of Article FOURTH:

                        "Notwithstanding the foregoing, the provisions of this
                        Subsection 4(i) shall not apply to the Excluded Merger."

                              3. The following sentence shall be inserted at the
                        end of Subsection D.4(h) of Article FOURTH:

                        "Notwithstanding the foregoing, the provisions of this
                        Subsection 4(h) shall not apply to the Excluded Merger."



<PAGE>   84

                              4. The following sentence shall be inserted at the
                        end of Subsection E.4(h) of Article FOURTH:

                        "Notwithstanding the foregoing, the provisions of this
                        Subsection 4(h) shall not apply to the Excluded Merger."

                              5. The following sentence shall be inserted at the
                        end of Subsection 4(h) of the Certificate of Designation
                        of the Series C-1 Convertible Preferred Stock:

                        "Notwithstanding the foregoing, the provisions of this
                        Subsection 4(h) shall not apply to the Excluded Merger."

                              6. The following sentence shall be inserted at the
                        end of Subsection 4(h) of the Certificate of Designation
                        of the Series G Convertible Preferred Stock:

                        "Notwithstanding the foregoing, the provisions of this
                        Subsection 4(h) shall not apply to the Excluded Merger."

FOURTH:  That the aforesaid amendments were duly adopted in accordance with the
         applicable provisions of Sections 228 and 242 of the General
         Corporation Law of the State of Delaware.





                                       2
<PAGE>   85

         IN WITNESS WHEREOF, Ontogeny, Inc. has caused this certificate to be
signed by Doros Platika, its President, this ____ day of ______ 2000.




                                                  ONTOGENY, INC.


                                                  By:
                                                      -------------------------
                                                      Doros Platika
                                                      Its: President






                                       3
<PAGE>   86
                                   EXHIBIT H
                                   ---------

                          ARTICLES OF AMENDMENT TO THE
              SECOND AMENDED AND RESTATED ARTICLES OF INCORPORATION
                                       OF
                               REPROGENESIS, INC.


         Pursuant to the provisions of Article 4.04 of the Texas Business
Corporation Act (the "TBCA"), Reprogenesis, Inc., a Texas corporation (the
"Corporation"), hereby adopts the following Articles of Amendment to its Second
Amended and Restated Articles of Incorporation, as amended October 13, 1999:


                                    Article I

         The name of the corporation is Reprogenesis, Inc.


                                   Article II

         These Articles of Amendment to the Second Amended and Restated Articles
of Incorporation of the Corporation, as amended October 13, 1999, were adopted
by the written consent of the holders of the common stock of the Corporation,
the Series A Preferred Stock of the Corporation and the Series B Preferred Stock
of the Corporation as of ____________________, 2000.


                                   Article III

         In order to clarify the liquidation rights of the Corporation's Series
A Preferred Stock upon the consummation of the proposed merger of the
Corporation with Creative Biomolecules, Inc. ("Creative") and Ontogeny, Inc.
("Ontogeny") into Curis, Inc. ("Curis"), the following new sentences are added
to the last line of Article Four D.3(a) before the words "After such payment":

         Notwithstanding anything to the contrary in this section 3(a), upon the
         consummation of the merger of the Corporation with Creative and
         Ontogeny into Curis (the "Merger") pursuant to the Agreement and Plan
         of Merger among Creative, Ontogeny, the Corporation and Curis dated as
         of February 14, 2000, each holder of a share of Series A Preferred
         shall be entitled to receive in respect of each share of Series A
         Preferred that such holders own, in full satisfaction of the
         liquidation preference specified in this section 3(a), the number of
         fully paid and nonassessable shares of common stock, par value $0.01
         per share, of the surviving entity (the "Surviving Company Common
         Stock") equal to the Series A Consideration divided by 2,702,702. In
         addition, each holder of Series A Preferred who would otherwise be
         entitled to a fraction of a share shall receive cash in lieu of any
         fraction of a share of Surviving Company Common Stock. "Series A
         Consideration" shall mean the lesser of (A) the number of fully paid
         and nonassessable shares of Surviving Company Common Stock whose
         aggregate Trailing Average Market Price equals $6,000,000, and (B) the
         Fully Diluted Merger Consideration. For the purposes of this section
         3(a), "Trailing Average Market Price" shall mean the average of the
         daily Market Price for each business day on the twenty (20) consecutive
         business days the last day of which shall be the fifth business day
         prior to the effective time of





<PAGE>   87
         the Merger, divided by 0.30; "Fully Diluted Merger Consideration" shall
         mean the product of 0.1956 and the aggregate number of shares of Common
         Stock and Series Preferred either issued or outstanding or subject to
         outstanding options or warrants to purchase immediately prior to the
         consummation of the Merger [(other than any such shares held in the
         treasury of the Corporation)]; and "Market Price" at any date shall be
         deemed to be the last reported sale price of common stock, par value
         $0.01 per share, of Creative, or, in case no such reported sale takes
         place on such day, the average of the bid and asked prices, in either
         case as officially reported by the Nasdaq National Market, or, if the
         Nasdaq National Market is no longer reporting such information, as
         reasonably determined in good faith by resolution of the Board of
         Directors of the Corporation.


                                   Article IV

         The designation and number of outstanding shares of each class or
series entitled to vote thereon and the number of shares which have signed a
consent in writing pursuant to Article 9.10A of the TBCA adopting said Articles
of Amendment were as follows:

                                             Number of Shares   Number of Shares
                                             Outstanding and         Signing
                                             Entitled to Vote   Written Consent
                                             ----------------   ---------------

Common Stock, par value $0.01                ________________   ________________

Series A Preferred Stock, par value $0.01    ________________   ________________

Series B Preferred Stock, par value $0.01    ________________   ________________






                                       2
<PAGE>   88

         IN WITNESS WHEREOF, the Corporation has caused these Articles of
Amendment to the Amended and Restated Articles of Incorporation to be duly
executed as of the ____ day of __________________, 2000.




                                        REPROGENESIS, INC.


                                        By:
                                            ----------------------------------

                                        Name:
                                             ---------------------------------

                                        Title:
                                              --------------------------------







                                       3


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