ARONEX PHARMACEUTICALS INC
8-A12G, 1999-10-07
PHARMACEUTICAL PREPARATIONS
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<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                    FORM 8-A

                For Registration of Certain Classes of Securities
                   Pursuant to Section 12(b) or 12 (g) of The
                         Securities Exchange Act of 1934


                          ARONEX PHARMACEUTICALS, INC.
             (Exact name of registrant as specified in its charter)


                DELAWARE                                  76-0196535
(State of incorporation or organization)    (I.R.S. Employer Identification No.)


    8707 TECHNOLOGY FOREST PLACE
         THE WOODLANDS, TEXAS                             77381-1191
(Address of principal executive office)                   (Zip Code)

SECURITIES TO BE REGISTERED PURSUANT TO SECTION 12(b) OF THE ACT:

None


If this form relates to the registration of a class of securities pursuant to
Section 12(b) of the Exchange Act and is effective pursuant to General
Instruction A(c), check the following box. [ ]

If this form relates to the registration of a class of securities pursuant to
Section 12(g) of the Exchange Act and is effective pursuant to General
Instruction A(d), check the following box. [X]

Securities Act registration statement file number to which this form
relates: not applicable.

SECURITIES TO BE REGISTERED PURSUANT TO SECTION 12(g) OF THE ACT:

         TITLE OF EACH CLASS                NAME OF EACH EXCHANGE ON WHICH
         TO BE SO REGISTERED:               EACH CLASS IS TO BE REGISTERED:

     Rights to purchase Series One               Nasdaq National Market
   Junior Participating Preferred Stock



<PAGE>   2



ITEM 1.  DESCRIPTION OF REGISTRANT'S SECURITIES TO BE REGISTERED

         The authorized capital stock of Aronex Pharmaceuticals, Inc. (the
"Company") consists of 40,000,000 shares of common stock, par value $.001 per
share (the "Common Stock"), and 5,000,000 shares of preferred stock, par value
$.001 per share, of which 750,000 shares are designated as the Series One Junior
Participating Preferred Stock (the "Preferred Stock").

SUMMARY OF RIGHTS TO PURCHASE PREFERRED STOCK

         On October 6, 1999, the Board of Directors of Aronex Pharmaceuticals,
Inc. (the "Company") declared a dividend distribution of one preferred stock
purchase right (a "Right") for each outstanding share of common stock, par value
$0.001 per share ("Common Stock"), of the Company. The distribution is payable
on October 18, 1999 (the "Record Date") to the stockholders of record on that
date. Each Right entitles the registered holder thereof to purchase from the
Company one one-hundredth of a share of Series One Junior Participating
Preferred Stock, par value $0.001 per share, of the Company (the "Preferred
Stock") at a price of $32.00, subject to adjustment. The following is a summary
of the Rights; the full description and terms of the Rights are set forth in a
Rights Agreement (the "Rights Agreement") between the Company and American Stock
Transfer & Trust Company, as Rights Agent (the "Rights Agent").

         Copies of the Rights Agreement and the Certificate of Designation are
available free of charge from the Company. This summary description of the
Rights and the Preferred Stock does not purport to be complete and is qualified
in its entirety by reference to all the provisions of the Rights Agreement and
the Certificate of Designation, including the definitions therein of certain
terms, which Rights Agreement and Certificate of Designation are incorporated
herein by reference.

         Initially, the Rights will attach to all certificates representing
shares of outstanding Company Common Stock, and no separate Rights Certificates
will be distributed. The Rights will separate from the Company Common Stock and
the Distribution Date will occur upon the earlier of (i) 10 days following the
date of public announcement that a person or group of persons has become an
Acquiring Person (as hereinafter defined) or (ii) 10 business days (or such
later date as may be determined by action of the Board of Directors prior to the
time a person becomes an Acquiring Person) following the commencement of, or the
announcement of an intention to make, a tender offer or exchange offer upon
consummation of which the offeror would, if successful, beneficially own 20% or
more of the outstanding Common Stock (the earlier of such dates being called the
"Distribution Date"). The term "Acquiring Person" means any person who or which,
together with all of its affiliates and associates, shall be the beneficial
owner of 20% or more of the outstanding Common Stock, but shall not include the
Company, any Subsidiary of the Company or any employee benefit plan of the
Company.

         The Rights Agreement provides that, until the Distribution Date, the
Rights will be transferred with and only with the Common Stock. Until the
Distribution Date (or earlier redemption or expiration of the Rights), new
Common Stock certificates issued after the Record Date, upon transfer or new
issuance of Common Stock, will contain a notation incorporating the Rights
Agreement by reference. Until the Distribution Date (or earlier redemption or
expiration of the Rights), the surrender for transfer of any certificates for
Common Stock, outstanding as of the Record Date, even without such notation or a
copy of this Summary of Rights being attached thereto, will also constitute the
transfer of the Rights associated with the Common Stock represented by such
certificate. As soon as practicable following the Distribution Date, separate
certificates evidencing the Rights ("Rights Certificates") will be mailed to
holders of record of the Common Stock as of the close of business on the
Distribution Date and such separate Rights Certificates alone will evidence the
Rights.

         The Rights are not exercisable until the Distribution Date. The Rights
will expire on October 18, 2009 (the "Expiration Date").

         The Purchase Price payable, and the number of one one-hundredths of a
share of Preferred Stock or other securities or property issuable, upon exercise
of the Rights are subject to adjustment from time to time to prevent dilution
(i) in the event of a stock dividend on, or a subdivision, combination or
reclassification of, the Preferred Stock, (ii) upon the grant to holders of the
Preferred Stock of certain rights or warrants to subscribe for or purchase
shares of Preferred Stock at a price, or securities convertible into Preferred
Stock with a conversion price, less than the then current market price of the
Preferred Stock or (iii) upon the distribution to holders of the Preferred Stock
of evidences of indebtedness

                                      -2-

<PAGE>   3


or assets (excluding regular periodic cash dividends paid or dividends payable
in Preferred Stock) or of subscription rights or warrants (other than those
referred to in (ii) above).

         The number of outstanding Rights and the number of one one-hundredths
of a share of Preferred Stock issuable upon exercise of each Right are also
subject to adjustment in the event of a stock split of the Common Stock or a
stock dividend on the Common Stock payable in the Common Stock or subdivisions,
consolidations or combinations of the Common Stock occurring, in any such case,
prior to the Distribution Date.

         In the event that following a Shares Acquisition Date (the date of
public announcement that an Acquiring Person has become such) the Company is
acquired in a merger or other business combination transaction, or more than 50%
of its consolidated assets or earning power are sold, proper provision will be
made so that each holder of a Right will thereafter have the right to receive,
upon the exercise thereof at the then current exercise price of the Right, that
number of shares of common stock of the acquiring company which at the time of
such transaction will have a market value of two times the exercise price of the
Right (the "Flip-Over Right").

         In the event that a person becomes an Acquiring Person, proper
provision shall be made so that each holder of a Right (other than the Acquiring
Person and its affiliates and associates) will thereafter have the right to
receive upon exercise that number of shares of Common Stock (or, under certain
circumstances, cash, other equity securities or property of the Company) having
a market value equal to two times the Purchase Price of the Rights (the "Flip-In
Right"). Upon the occurrence of the foregoing event giving rise to the
exercisability of the Rights, any Rights that are or were at any time owned by
an Acquiring Person shall become void.

         With certain exceptions, no adjustment in the Purchase Price will be
required until cumulative adjustments require an adjustment of at least 1% in
such Purchase Price. Upon exercise of the Rights, no fractional shares of
Preferred Stock will be issued other than fractions which are integral multiples
of one one-hundredth of a share of Preferred Stock; cash will be paid in lieu of
fractional shares of Preferred Stock that are not integral multiples of one
one-hundredth of a share of Preferred Stock.

         At any time prior to the earlier to occur of (i) 5:00 p.m., Houston,
Texas time on the 10th day after the Shares Acquisition Date or (ii) the
expiration of the Rights, the Company may redeem the Rights in whole, but not in
part, at a price of $0.001 per Right (the "Redemption Price"); provided, that
(i) if the Board of Directors authorizes redemption on or after the time a
person becomes an Acquiring Person, then such authorization must be by Board
Approval (as hereinafter defined) and (ii) the period for redemption may, upon
Board Approval, be extended by amending the Rights Agreement. The term "Board
Approval" means the approval of a majority of the directors of the Company.
Immediately upon any redemption of the Rights described in this paragraph, the
right to exercise the Rights will terminate and the only right of the holders of
Rights will be to receive the Redemption Price.

         For so long as the Rights are redeemable, the terms of the Rights may
be amended by the Board of Directors without the consent of the holders of the
Rights provided that no amendment to the Rights may be made which decreases the
Redemption Price. At such time as the Rights are no longer redeemable, the
Rights Agreement and the terms of the Rights may be amended without the approval
of any holders of the Rights to (i) cure any ambiguity, (ii) correct or
supplement any defective or inconsistent provision, (iii) shorten or lengthen
any time period under the Rights Agreement, or (iv) change or supplement any
provision contained in the Rights Agreement which the Board of Directors deems
necessary; provided, that no such supplement or amendment may adversely affect
the interests of the holders of the Rights (other than an Acquiring Person and
its affiliates) and no such amendment shall cause the Rights to again become
redeemable or cause the Rights Agreement to again become amendable except as
provided therein.

         Until a Right is exercised, the holder thereof, as such, will have no
rights as a stockholder of the Company, including, without limitation, the right
to vote or to receive dividends. While the distribution of the Rights will not
be taxable to stockholders or to the Company, stockholders may, depending upon
the circumstances, recognize taxable income in the event that the Rights become
exercisable for Preferred Stock (or other consideration).


                                       -3-
<PAGE>   4


DESCRIPTION OF PREFERRED STOCK

         Each one-hundredth of a share of the Preferred Stock ("Preferred Share
Fraction") that may be acquired upon exercise of the Rights will be
nonredeemable and subordinate to any other shares of preferred stock that may be
issued by the Company.

         Each Preferred Share Fraction will have a minimum preferential
quarterly dividend rate of $0.01 per Preferred Share Fraction but will, in any
event, be entitled to a dividend equal to the per share dividend declared on the
Company Common Stock.

         In the event of liquidation, the holder of a Preferred Share Fraction
will receive a preferred liquidation payment equal to the greater of $0.01 per
Preferred Share Fraction or the per share amount paid in respect of a share of
Company Common Stock.

         Each Preferred Share Fraction will have one vote, voting together with
the Company Common Stock.

         In the event of any merger, consolidation or other transaction in which
shares of Company Common Stock are exchanged, each Preferred Share Fraction will
be entitled to receive the per share amount paid in respect of each share of
Company Common Stock.

         The rights of holders of the Preferred Stock to dividends, liquidation
and voting, and in the event of mergers and consolidations, are protected by
customary antidilution provisions.

         Because of the nature of the Preferred Stock's dividend, liquidation
and voting rights, the economic value of one Preferred Share Fraction that may
be acquired upon the exercise of each Right should approximate the economic
value of one share of the Company's Common Stock.

         Additional information regarding the Rights is set forth in the Rights
Agreement which is filed herewith as Exhibit 4.1 and incorporated herein by
reference.

ITEM 2.  EXHIBITS

         3.1      Certificate of Designation of Series One Junior Participating
                  Preferred Stock dated October 6, 1999 (attached as Exhibit A
                  to the Rights Agreement filed as Exhibit 4.1 hereto).

         4.1      Rights Agreement, dated October 6, 1999, between the Company
                  and American Stock Transfer & Trust Company, as Rights Agent.

         4.2      Form of Rights Certificate (attached as Exhibit B to the
                  Rights Agreement filed as Exhibit 4.1 hereto).


                                    SIGNATURE

         Pursuant to the requirements of Section 12 of the Securities Exchange
Act of 1934, as amended, the Registrant has duly caused this Registration
Statement on Form 8-A to be signed on its behalf by the undersigned, thereunto
duly authorized.

                                       ARONEX PHARMACEUTICALS, INC.


                                       By:  /s/ Geoffrey F. Cox
                                          --------------------------------------
                                            Geoffrey F. Cox
                                            Chief Executive Officer


Dated: October 7, 1999


                                       -4-
<PAGE>   5


                                  EXHIBIT INDEX


<TABLE>
<CAPTION>
Exhibit No.                        Description
- -----------                        -----------
<S>               <C>
         3.1      Certificate of Designation of Series One Junior Participating
                  Preferred Stock dated October 6, 1999 (attached as Exhibit A
                  to the Rights Agreement filed as Exhibit 4.1 hereto).

         4.1      Rights Agreement, dated October 6, 1999, between the Company
                  and American Stock Transfer & Trust Company, as Rights Agent.

         4.2      Form of Rights Certificate (attached as Exhibit B to the
                  Rights Agreement filed as Exhibit 4.1 hereto).
</TABLE>


                                       -5-

<PAGE>   1
                                                                    EXHIBIT 4.1

                          ARONEX PHARMACEUTICALS, INC.

                                      AND

            AMERICAN STOCK TRANSFER & TRUST COMPANY, AS RIGHTS AGENT


                                RIGHTS AGREEMENT


                          DATED AS OF OCTOBER 6, 1999




<PAGE>   2


                               TABLE OF CONTENTS


<TABLE>
<S>         <C>                                                                                                 <C>
Section 1.  Certain Definitions...................................................................................1

Section 2.  Appointment of Rights Agent...........................................................................7

Section 3.  Issue of Right Certificates...........................................................................7

Section 4.  Form of Right Certificates...........................................................................10

Section 5.  Countersignature and Registration....................................................................10

Section 6.  Transfer, Split Up, Combination and Exchange of Right Certificates;
               Mutilated, Destroyed, Lost or Stolen Right Certificates...........................................11

Section 7.  Exercise of Rights; Purchase Price; Expiration Date of Rights........................................13

Section 8.  Cancellation and Destruction of Right Certificates...................................................15

Section 9.  Availability of Preferred Shares.....................................................................15

Section 10.  Preferred Shares Record Date........................................................................17

Section 11.  Adjustment of Purchase Price, Number of Shares or Number of Rights..................................18

Section 12.  Certificate of Adjusted Purchase Price or Number of Shares..........................................32

Section 13.  Consolidation, Merger or Sale or Transfer of Assets or Earning Power................................32

Section 14.  Fractional Rights and Fractional Shares.............................................................38

Section 15.  Rights of Action....................................................................................40

Section 16.  Agreement of Right Holders..........................................................................41

Section 17.  Right Certificate Holder Not Deemed a Stockholder...................................................42

Section 18.  Concerning the Rights Agent.........................................................................42

Section 19.  Merger or Consolidation or Change of Name of Rights Agent...........................................43

Section 20.  Duties of Rights Agent..............................................................................44

Section 21.  Change of Rights Agent..............................................................................48
</TABLE>


<PAGE>   3


<TABLE>
<S>          <C>                                                                                                <C>
Section 22.  Issuance of New Right Certificates..................................................................50

Section 23.  Redemption..........................................................................................50

Section 24.  Exchange............................................................................................51

Section 25.  Notice of Certain Events............................................................................54

Section 26.  Notices.............................................................................................55

Section 27.  Supplements and Amendments..........................................................................56

Section 28.  Successors..........................................................................................57

Section 29.  Benefits of this Agreement..........................................................................57

Section 30.  Determination and Actions by the Board of Directors.................................................57

Section 31.  Severability........................................................................................58

Section 32.  Governing Law.......................................................................................58

Section 33.  Counterparts........................................................................................58

Section 34.  Descriptive Headings................................................................................58
</TABLE>

Exhibits:         A-Certificate of Designations

                  B-Form of Right Certificate

                  C-Summary of Rights to Purchase Preferred Shares


<PAGE>   4


                                RIGHTS AGREEMENT

         This Agreement, dated as of October 6, 1999 ("Agreement"), between
Aronex Pharmaceuticals, Inc., a Delaware corporation (the "Company"), and
American Stock Transfer & Trust Company, as rights agent (the "Rights Agent").

                                R E C I T A L S:

         WHEREAS, at a meeting of the Board of Directors of the Company duly
called and held on October 6, 1999, at which a quorum was present and acting
throughout, such Board of Directors has authorized and declared a dividend of
one preferred share purchase right (a "Right") for each share of Common Stock
(as such term is hereinafter defined) of the Company outstanding at the close
of business on October 18, 1999 (the "Record Date"), each Right representing
the right to purchase one one-hundredth of a Preferred Share, upon the terms
and subject to the conditions herein set forth, and has further authorized and
directed the issuance of one Right with respect to each share of Common Stock
that shall become outstanding between the Record Date and the earliest of the
Distribution Date, the Redemption Date and the Final Expiration Date (as such
terms are hereinafter defined);

         NOW, THEREFORE, in consideration of the premises and the mutual
agreements herein set forth, the parties hereby agree as follows:

         Section 1. Certain Definitions. For purposes of this Agreement, the
following terms have the meanings indicated:

                  (a) "Acquiring Person" shall mean any Person (as such term is
         hereinafter defined) who or which shall be the Beneficial Owner (as
         such term is hereinafter defined) of 20% or more of the shares of
         Common Stock then outstanding, but shall not include an Exempt Person;
         provided, however, that if the Board of Directors of the Company
         determines


<PAGE>   5

         in good faith that a Person who would otherwise be an "Acquiring
         Person" has become such inadvertently (including, without limitation,
         because (i) such Person was unaware that it beneficially owned a
         percentage of Common Stock that would otherwise cause such Person to
         be an "Acquiring Person" or (ii) such Person was aware of the extent
         of its Beneficial Ownership of Common Stock but was unaware of the
         consequences of such Beneficial Ownership under this Agreement) and
         without any intention of changing or influencing control of the
         Company, and such Person, as promptly as practicable after being
         advised of such determination divested or divests himself or itself of
         Beneficial Ownership of a sufficient number of shares of Common Stock
         so that such Person would no longer be an Acquiring Person, then such
         Person shall not be deemed to be or to have become an "Acquiring
         Person" for any purposes of this Agreement. Notwithstanding the
         foregoing, no Person shall become an "Acquiring Person" as the result
         of an acquisition of Common Stock by the Company which, by reducing
         the number of shares outstanding, increases the proportionate number
         of shares beneficially owned by such Person to 20% or more of the
         Common Stock of the Company then outstanding; provided, however, that
         if a Person shall become the Beneficial Owner of 20% or more of the
         Common Stock of the Company then outstanding by reason of the share
         purchases by the Company and shall, after such share purchases by the
         Company, become the Beneficial Owner of any additional Common Stock of
         the Company, then such Person shall be deemed to be an "Acquiring
         Person" unless upon the consummation of the acquisition of such
         additional shares of Common Stock such Person does not own 20% or more
         of the shares of Common Stock then outstanding.


                                      -2-

<PAGE>   6

                  (b) "Affiliate" shall have the meaning ascribed to such term
         in Rule 12b-2 of the General Rules and Regulations under the Exchange
         Act as in effect on the date of this Agreement.

                  (c) "Associate" shall have the meaning ascribed to such term
         in Rule l2b-2 of the General Rules and Regulations under the Exchange
         Act as in effect on the date of this Agreement.

                  (d) A Person shall be deemed the "Beneficial Owner" of and,
         shall be deemed to have "Beneficial Ownership" of and shall be deemed
         to "beneficially own" any securities:

                           (i) which such Person or any of such Person's
                  Affiliates or Associates beneficially owns, directly or
                  indirectly;

                           (ii) which such Person or any of such Person's
                  Affiliates or Associates has (A) the right to acquire
                  (whether such right is exercisable immediately or only after
                  the passage of time) pursuant to any agreement, arrangement
                  or understanding (other than customary agreements with and
                  between underwriters and selling group members with respect
                  to a bona fide public offering of securities), or upon the
                  exercise of conversion rights, exchange rights, rights (other
                  than these Rights), warrants or options, or otherwise;
                  provided, however, that a Person shall not be deemed the
                  Beneficial Owner of, or to beneficially own, (I) securities
                  tendered pursuant to a tender or exchange offer made by or on
                  behalf of such Person or any of such Person's Affiliates or
                  Associates until such tendered securities are accepted for
                  purchase or exchange or (II) securities which such Person has
                  a right to acquire upon the exercise of Rights at any time
                  prior to the time a Person becomes an Acquiring Person; or
                  (B) the right to vote pursuant to any agreement, arrangement
                  or


                                      -3-

<PAGE>   7

                  understanding; provided, however, that a Person shall not be
                  deemed the Beneficial Owner of, or to beneficially own, any
                  security by reason of such an agreement, arrangement or
                  understanding if the agreement, arrangement or understanding
                  to vote such security (1) arises solely from a revocable
                  proxy or consent given to such Person in response to a public
                  proxy or consent solicitation made pursuant to, and in
                  accordance with, the applicable rules and regulations
                  promulgated under the Exchange Act (as such term is
                  hereinafter defined) and (2) is not also then reportable on
                  Schedule 13D under the Exchange Act (or any comparable or
                  successor report); or

                           (iii) which are beneficially owned, directly or
                  indirectly, by any other Person with which such Person or any
                  of such Person's Affiliates or Associates has any agreement,
                  arrangement or understanding (other than customary agreements
                  with and between underwriters and selling group members with
                  respect to a bona fide public offering of securities) for the
                  purpose of acquiring, holding, voting (except to the extent
                  contemplated by the proviso to Section 1(d)(ii)(B)) or
                  disposing of any securities of the Company.

                  Notwithstanding anything in this definition of Beneficial
         Ownership to the contrary, the phrase "then outstanding," when used
         with reference to a Person's Beneficial Ownership of securities of the
         Company, shall mean the number of such securities then issued and
         outstanding together with the number of such securities not then
         issued and outstanding which such Person would be deemed to own
         beneficially hereunder.

                                      -4-

<PAGE>   8

                  (e) "Business Day" shall mean any day other than a Saturday,
         a Sunday, or a day on which banking institutions in New York are
         authorized or obligated by law or executive order to close.

                  (f) "Close of Business" on any given date shall mean 5:00
         P.M., Houston, Texas time, on such date; provided, however, that, if
         such date is not a Business Day, it shall mean 5:00 P.M., Houston,
         Texas time, on the next succeeding Business Day.

                  (g) "Common Stock" when used with reference to the Company
         shall mean the common stock, par value $0.001 per share, of the
         Company. "Common Shares" when used with reference to the Company shall
         mean shares of Common Stock. "Common Stock" when used with reference
         to any Person other then the Company shall mean the capital stock (or,
         in the case of an unincorporated entity, the equivalent equity
         interest) with the greatest voting power of such other Person or, if
         such other Person is a Subsidiary of another Person, the Person or
         Persons which ultimately control such first-mentioned Person.

                  (h) "Common Stock equivalent" shall have the meaning set
         forth in Section 11(a)(iii) hereof.

                  (i) "Company" shall have the meaning set forth in the
         preamble hereof.

                  (j) "current per share market price" shall have the meaning
         set forth in Section 11(d) hereof.

                  (k) "Current Value" shall have the meaning set forth in
         Section 11(a)(iii) hereof.

                  (l) "Distribution Date" shall have the meaning set forth in
         Section 3 hereof.

                  (m) "Equivalent Preferred Shares" shall have the meaning set
         forth in Section 11(b) hereof.

                  (n) "Exchange Act" shall mean the Securities Exchange Act of
         1934, as amended.

                                      -5-

<PAGE>   9

                  (o) "Exchange Ratio" shall have the meaning set forth in
         Section 24(a) hereof.

                  (p) "Exempt Person" shall mean the Company or any Subsidiary
         (as such term is hereinafter defined) of the Company or any employee
         benefit plan of the Company.

                  (q) "Final Expiration Date" shall have the meaning set forth
         in Section 7(a) hereof.

                  (r) "Nasdaq" shall mean the National Association of
         Securities Dealers, Inc. Automated Quotations System.

                  (s) "Person" shall mean any individual, firm, corporation,
         limited liability company, partnership, limited partnership or other
         entity, and shall include any successor (by merger or otherwise) of
         such entity.

                  (t) "Preferred Stock" shall mean the Series One Junior
         Participating Preferred Stock, par value $0.001 per share, of the
         Company having the rights and preferences set forth in the Form of
         Certificate of Designations attached to this Agreement as Exhibit A.
         "Preferred Shares" shall mean shares of the Preferred Stock.

                  (u) "Principal Party" shall have the meaning set forth in
         Section 13(b) hereof.

                  (v) "Purchase Price" shall have the meaning set forth in
         Section 7(b) hereof.

                  (w) "Record Date" shall have the meaning set forth in the
         second paragraph hereof.

                  (x) "Redemption Date" shall have the meaning set forth in
         Section 7(a) hereof.

                  (y) "Redemption Price" shall have the meaning set forth in
         Section 23(a) hereof.

                  (z) "Rights Agent" shall have the meaning set forth in the
         preamble hereof.

                  (aa) "Right" shall have the meaning set forth in the second
         paragraph hereof.

                  (ab) "Right Certificate" shall have the meaning set forth in
         Section 3(a) hereof.

                                      -6-

<PAGE>   10

                  (ac) "Section 11(a)(ii) Trigger Date" shall have the meaning
         set forth in Section 11(a)(iii) hereof.

                  (ad) "Security" shall have the meaning set forth in Section
         11(d) hereof.

                  (ae) "Shares Acquisition Date" shall mean the first date of
         public announcement by the Company or an Acquiring Person that an
         Acquiring Person has become such.

                  (af) "Subsidiary" of any Person shall mean any corporation or
         other entity of which a majority of the voting power of the voting
         equity securities or equity interest is owned, directly or indirectly,
         by such Person.

                  (ag) "Substitution Period" shall have the meaning set forth
         in Section 11(a)(iii) hereof.

                  (ah) "Summary of Rights" shall have the meaning set forth in
         Section 3(b) hereof.

                  (ai) "Trading Day" shall have the meaning set forth in
         Section 11(d) hereof.

         Section 2. Appointment of Rights Agent. The Company hereby appoints
the Rights Agent to act as agent for the Company and the holders of the Rights
(who, in accordance with Section 3 hereof, shall, prior to the Distribution
Date, also be the holders of the Common Shares) in accordance with the terms
and conditions hereof, and the Rights Agent hereby accepts such appointment.
The Company may from time to time appoint such co-Rights Agents as it may deem
necessary or desirable.

         Section 3. Issue of Right Certificates. (a) Until the earlier of (i)
the tenth day after the Shares Acquisition Date or (ii) the tenth business day
(or such later date as may be determined by action of the Board of Directors of
the Company prior to such time as any Person becomes an Acquiring Person) after
the date of the commencement by any Person of, or of the first public
announcement of the intention of any Person to commence, a tender or exchange
offer the consummation of which


                                      -7-

<PAGE>   11

would result in any Person becoming an Acquiring Person (including any such
date which is after the date of this Agreement and prior to the issuance of the
Rights; the earlier of such dates being herein referred to as the "Distribution
Date"), (x) the Rights will be evidenced (subject to the provisions of Section
3(b) hereof) by the certificates for Common Shares registered in the names of
the holders thereof (which certificates shall also be deemed to be Right
Certificates) and not by separate Right Certificates, and (y) the Rights will
be transferable only in connection with the transfer of Common Shares. As soon
as practicable after the Distribution Date, the Company will prepare and
execute, the Rights Agent will countersign, and the Company will send or cause
to be sent (and the Rights Agent will, if requested, at the expense of the
Company, send) by first-class, insured, postage prepaid mail, to each record
holder of Common Shares as of the close of business on the Distribution Date,
at the address of such holder shown on the records of the Company, a Right
Certificate, in substantially the form of Exhibit B hereto (a "Right
Certificate"), evidencing one Right for each share of Common Stock so held. As
of the Distribution Date, the Rights will be evidenced solely by such Right
Certificates.

         (b) On the Record Date, or as soon as practicable thereafter, the
Company will send a copy of a Summary of Rights to Purchase Preferred Shares,
in substantially the form of Exhibit C hereto (the "Summary of Rights"), by
first-class, postage-prepaid mail, to each record holder of Common Shares as of
the Close of Business on the Record Date, at the address of such holder shown
on the records of the Company. With respect to certificates for Common Shares
outstanding as of the Record Date, until the Distribution Date, the Rights will
be evidenced by such certificates registered in the names of the holders
thereof together with a copy of the Summary of Rights attached thereto. Until
the Distribution Date (or the earlier of the Redemption Date or the Final
Expiration Date), the surrender for transfer of any certificate for Common
Shares outstanding on the

                                      -8-

<PAGE>   12

Record Date, with or without a copy of the Summary of Rights attached thereto,
shall also constitute the transfer of the Rights associated with the Common
Shares represented thereby.

         (c) Certificates for Common Shares which become outstanding
(including, without limitation, reacquired Common Shares referred to in the
last sentence of this paragraph (c) that are subsequently issued or distributed
by the Company) after the Record Date but prior to the earliest of the
Distribution Date, the Redemption Date or the Final Expiration Date shall have
impressed on, printed on, written on or otherwise affixed to them the following
legend:

                  This certificate also evidences and entitles the holder
         hereof to certain Rights as set forth in a Rights Agreement between
         Aronex Pharmaceuticals, Inc. and American Stock Transfer & Trust
         Company, as Rights Agent (the "Rights Agreement"), the terms of which
         are hereby incorporated herein by reference and a copy of which is on
         file at the principal executive offices of Aronex Pharmaceuticals,
         Inc. Under certain circumstances, as set forth in the Rights
         Agreement, such Rights may be redeemed or be evidenced by separate
         certificates and no longer be evidenced by this certificate. Aronex
         Pharmaceuticals, Inc. will mail to the holder of this certificate a
         copy of the Rights Agreement without charge after receipt of a written
         request therefor. Under certain circumstances, as set forth in the
         Rights Agreement, Rights owned by or transferred to any Person who
         becomes an Acquiring Person or an Affiliate or Associate thereof (as
         such terms are defined in the Rights Agreement), and certain
         transferees thereof, will become null and void and will no longer be
         transferable.

         With respect to such certificate containing the foregoing legend,
until the Distribution Date, the Rights associated with the Common Shares
represented by such certificates shall be evidenced by such certificates alone,
and the surrender for transfer of any such certificate shall also constitute
the transfer of the Rights associated with the Common Shares represented
thereby. In the event that the Company purchases or acquires any Common Shares
after the Record Date but prior to the Distribution Date, any Rights associated
with such Common Shares shall be deemed canceled and retired so that the
Company shall not be entitled to exercise any Rights associated with the Common
Shares which are no longer outstanding.


                                      -9-

<PAGE>   13

         Section 4. Form of Right Certificates. The Right Certificates (and the
forms of election to purchase Preferred Shares and of assignment to be printed
on the reverse thereof) shall be substantially the same as Exhibit B hereto and
may have such marks of identification or designation and such legends,
summaries or endorsements printed thereon as the Company may deem appropriate
and as are not inconsistent with the provisions of this Agreement, or as may be
required to comply with any applicable law or with any rule or regulation made
pursuant thereto or with any rule or regulation of any stock exchange on which
the Rights may from time to time be listed, or to conform to usage. Subject to
the provisions of Sections 11, 13 and 22 hereof, the Right Certificates shall
entitle the holders thereof to purchase such number of one one-hundredths of a
Preferred Share as shall be set forth therein at the price per one
one-hundredth of a Preferred Share set forth therein, but the number of such
one one-hundredths of a Preferred Share and the Purchase Price shall be subject
to adjustment as provided herein.

         Section 5. Countersignature and Registration. (a) The Right
Certificates shall be executed on behalf of the Company by its Chairman of the
Board, its Chief Executive Officer, its President, any of its Vice Presidents,
or its Treasurer, either manually or by facsimile signature, shall have affixed
thereto the Company's seal or a facsimile thereof, and shall be attested by the
Secretary or an Assistant Secretary of the Company, either manually or by
facsimile signature. The Right Certificates shall be manually countersigned by
the Rights Agent and shall not be valid for any purpose unless countersigned.
In case any officer of the Company who shall have signed any of the Right
Certificates shall cease to be such officer of the Company before
countersignature by the Rights Agent and issuance and delivery by the Company,
such Right Certificates, nevertheless, may be countersigned by the Rights Agent
and issued and delivered by the Company with the same force and effect as
though the Person who signed such Right Certificates had not ceased to be such
officer
                                      -10-

<PAGE>   14
of the Company; and any Right Certificate may be signed on behalf of the Company
by any Person who, at the actual date of the execution of such Right
Certificate, shall be a proper officer of the Company to sign such Right
Certificates although at the date of the execution of this Rights Agreement any
such Person was not such an officer.

         (b) Following the Distribution Date, the Rights Agent will keep or
cause to be kept, at its principal office, books for registration and transfer
of the Right Certificates issued hereunder. Such books shall show the names and
addresses of the respective holders of the Right Certificates, the number of
Rights evidenced on its face by each of the Right Certificates and the date of
each of the Right Certificates.

         Section 6. Transfer, Split Up, Combination and Exchange of Right
Certificates; Mutilated, Destroyed, Lost or Stolen Right Certificates. (a)
Subject to the provisions of Section 14 hereof, at any time after the Close of
Business on the Distribution Date, and at or prior to the Close of Business on
the earlier of the Redemption Date or the Final Expiration Date, any Right
Certificate or Right Certificates (other than Right Certificates representing
Rights that have become void pursuant to Section 11(a)(ii) hereof or that have
been exchanged pursuant to Section 24 hereof) may be transferred, split up,
combined or exchanged for another Right Certificate or Right Certificates
entitling the registered holder to purchase a like number of one one-hundredths
of a Preferred Share as the Right Certificate or Right Certificates surrendered
then entitled such holder to purchase. Any registered holder desiring to
transfer, split up, combine or exchange any Right Certificate or Right
Certificates shall make such request in writing delivered to the Rights Agent,
and shall surrender the Right Certificate or Right Certificates to be
transferred, split up, combined or exchanged at the principal office of the
Rights Agent. Neither the Rights Agent nor the Company shall be obligated to
take any action whatsoever with respect to the transfer of any such surrendered
Right Certificate

                                      -11-

<PAGE>   15
until the registered holder shall have completed and signed the certificate
contained in the form of assignment on the reverse side of such Right
Certificate and shall have provided such additional evidence of the identity of
the Beneficial Owner (or former Beneficial Owner) or Affiliates or Associates
thereof as the Company shall reasonably request. Thereupon, the Rights Agent
shall countersign and deliver to the Person entitled thereto a Right
Certificate or Right Certificates, as the case may be, as so requested. The
Company may require payment of a sum sufficient to cover any tax or
governmental charge that may be imposed in connection with any transfer, split
up, combination or exchange of Right Certificates.

         (b) Subject to the provisions of Section 11(a)(ii) hereof, at any time
after the Distribution Date and prior to the close of business on the earlier
of the Redemption Date and the Final Expiration Date, upon receipt by the
Company and the Rights Agent of evidence reasonably satisfactory to them of the
loss, theft, destruction or mutilation of a Right Certificate, and, in case of
loss, theft or destruction, of indemnity or security reasonably satisfactory to
them, and, at the Company's request, reimbursement to the Company and the
Rights Agent of all reasonable expenses incidental thereto, and upon surrender
to the Rights Agent and cancellation of the Right Certificate if mutilated, the
Company will make and deliver a new Right Certificate of like tenor to the
Rights Agent for delivery to the registered holder in lieu of the Right
Certificate so lost, stolen, destroyed or mutilated.

         Section 7. Exercise of Rights; Purchase Price; Expiration Date of
Rights. (a) The registered holder of any Right Certificate may exercise the
Rights evidenced thereby (except as otherwise provided herein), in whole or in
part, at any time after the Distribution Date, upon surrender of the Right
Certificate, with the form of election to purchase on the reverse side thereof
duly executed, to the Rights Agent at the principal office of the Rights Agent,
together with payment of the Purchase

                                      -12-

<PAGE>   16

Price for each one one-hundredth of a Preferred Share as to which the Rights
are exercised, at or prior to the earliest of (i) the Close of Business on
October 18, 2009 (the "Final Expiration Date"), (ii) the time at which the
Rights are redeemed as provided in Section 23 hereof (the "Redemption Date")
and (iii) the time at which such Rights are exchanged as provided in Section 24
hereof.

         (b) The Purchase Price for each one one-hundredth of a Preferred Share
purchasable pursuant to the exercise of a Right shall initially be $32.00, and
shall be subject to adjustment from time to time as provided in Section 11 or
13 hereof (the "Purchase Price") and shall be payable in lawful money of the
United States of America in accordance with paragraph (c) of this Section 7.

         (c) Upon receipt of a Right Certificate representing exercisable
Rights, with the form of election to purchase duly executed, accompanied by
payment of the Purchase Price for the shares to be purchased and an amount
equal to any applicable transfer tax required to be paid by the holder of such
Right Certificate in accordance with Section 9 hereof by certified check,
cashier's check or money order payable to the order of the Company, the Rights
Agent shall thereupon promptly (i) (A) requisition from any transfer agent of
the Preferred Shares certificates for the number of Preferred Shares to be
purchased and the Company hereby irrevocably authorizes any such transfer agent
to comply with all such requests, or (B) requisition from the depositary agent
depositary receipts representing such number of one one-hundredths of a
Preferred Share as are to be purchased (in which case certificates for the
Preferred Shares represented by such receipts shall be deposited by the
transfer agent of the Preferred Shares with such depositary agent) and the
Company hereby directs such depositary agent to comply with such request; (ii)
when appropriate, requisition from the Company the amount of cash to be paid in
lieu of issuance of fractional shares in accordance with Section 14 hereof;
(iii) promptly after receipt of such certificates or depositary receipts, cause
the same to be delivered to or upon the order of the registered holder of such
Right Certificate, registered


                                      -13-

<PAGE>   17

in such name or names as may be designated by such holder; and (iv) when
appropriate, after receipt, deliver such cash to or upon the order of the
registered holder of such Right Certificate.

         (d) Except as otherwise provided herein, in case the registered holder
of any Right Certificate shall exercise less than all the Rights evidenced
thereby, a new Right Certificate evidencing Rights equivalent to the Rights
remaining unexercised shall be issued by the Rights Agent to the registered
holder of such Right Certificate or to his duly authorized assigns, subject to
the provisions of Section 14 hereof.

         (e) Notwithstanding anything in this Agreement to the contrary,
neither the Rights Agent nor the Company shall be obligated to undertake any
action with respect to a registered holder of Rights upon the occurrence of any
purported transfer or exercise of Rights pursuant to Section 6 hereof or this
Section 7 unless such registered holder shall have (i) completed and signed the
certificate contained in the form of assignment or election to purchase set
forth on the reverse side of the Rights Certificate surrendered for such
transfer or exercise and (ii) provided such additional evidence of the identity
of the Beneficial Owner (or former Beneficial Owner) thereof as the Company
shall reasonably request.

         Section 8. Cancellation and Destruction of Right Certificates. All
Right Certificates surrendered for the purpose of exercise, transfer, split up,
combination or exchange shall, if surrendered to the Company or to any of its
agents be delivered to the Rights Agent for cancellation or in canceled form,
or, if surrendered to the Rights Agent, shall be canceled by it, and no Right
Certificates shall be issued in lieu thereof except as expressly permitted by
any of the provisions of this Agreement. The Company shall deliver to the
Rights Agent for cancellation and retirement, and the Rights Agent shall so
cancel and retire, any other Right Certificate purchased or acquired by the
Company otherwise than upon the exercise thereof. The Rights Agent shall
deliver all canceled


                                      -14-

<PAGE>   18
Right Certificates to the Company, or shall, at the written request of the
Company, destroy such cancelled Right Certificates, and, in such case, shall
deliver a certificate of destruction thereof to the Company.

         Section 9. Availability of Preferred Shares. (a) The Company covenants
and agrees that it will cause to be reserved and kept available out of its
authorized and unissued Preferred Shares or any Preferred Shares held in its
treasury, the number of Preferred Shares that will be sufficient to permit the
exercise in full of all outstanding Rights in accordance with Section 7. The
Company covenants and agrees that it will take all such action as may be
necessary to ensure that all Preferred Shares delivered upon exercise of Rights
shall at the time of delivery of the certificates for such Preferred Shares
(subject to payment of the Purchase Price), be duly and validly authorized and
issued and fully paid and nonassessable shares.

         (b) So long as the shares of Preferred Stock (and, following the time
that a Person becomes an Acquiring Person, shares of Common Stock and other
securities) issuable upon the exercise of Rights may be listed or admitted to
trading on any national securities exchange or quotation system, the Company
shall use its best efforts to cause, from and after such time as the Rights
become exercisable, all shares reserved for such issuance to be listed or
admitted to trading on any such exchange or quotation system upon official
notice of issuance upon such exercise.

         (c) From and after such time as the Rights become exercisable, the
Company shall use its best efforts, if then necessary to permit the issuance of
shares of Preferred Stock (and following the time that a Person first becomes
an Acquiring Person, shares of Common Stock and other securities) upon the
exercise of Rights, to register and qualify such shares of Preferred Stock (and
following the time that a Person first becomes an Acquiring Person, shares of
Common Stock and other securities) under the Securities Act and any applicable
state securities or "Blue Sky" laws (to



                                      -15-

<PAGE>   19


the extent exemptions therefrom are not available), cause such registration
statement and qualifications to become effective as soon as possible after such
filing and keep such registration and qualifications effective until the
earlier of the date as of which the Rights are no longer exercisable for such
securities and the Final Expiration Date. The Company may temporarily suspend,
for a period of time not to exceed 90 days, the exercisability of the Rights in
order to prepare and file a registration statement under the Securities Act and
permit it to become effective. Upon any such suspension, the Company shall
issue a public announcement stating that the exercisability of the Rights has
been temporarily suspended, as well as a public announcement at such time as
the suspension is no longer in effect. Notwithstanding any provision of this
Agreement to the contrary, the Rights shall not be exercisable in any
jurisdiction unless the requisite qualification in such jurisdiction shall have
been obtained and until a registration statement under the Securities Act (if
required) shall have been declared effective.

         (d) The Company further covenants and agrees that it will pay when due
and payable any and all federal and state transfer taxes and charges which may
be payable in respect of the issuance or delivery of the Right Certificates or
of any Preferred Shares upon the exercise of Rights. The Company shall not,
however, be required to pay any transfer tax which may be payable in respect of
any transfer or delivery of Right Certificates to a Person other than, or the
issuance or delivery of certificates or depositary receipts for the Preferred
Shares in a name other than that of, the registered holder of the Right
Certificate evidencing Rights surrendered for exercise or to issue or to
deliver any certificates or depositary receipts for Preferred Shares upon the
exercise of any Rights until any such tax shall have been paid (any such tax
being payable by the holder of such Right Certificate at the time of surrender)
or until it has been established to the Company's reasonable satisfaction that
no such tax is due.


                                      -16-

<PAGE>   20

         Section 10. Preferred Shares Record Date. Each Person in whose name
any certificate for Preferred Shares is issued upon the exercise of Rights
shall for all purposes be deemed to have become the holder of record of the
Preferred Shares represented thereby on, and such certificate shall be dated,
the date upon which the Right Certificate evidencing such Rights was duly
surrendered and payment of the Purchase Price (and any applicable transfer
taxes) was made; provided, however, that if the date of such surrender and
payment is a date upon which the Preferred Shares transfer books of the Company
are closed, such Person shall be deemed to have become the record holder of
such shares on, and such certificate shall be dated, the next succeeding
Business Day on which the Preferred Shares transfer books of the Company are
open. Prior to the exercise of the Rights evidenced thereby, the holder of a
Right Certificate shall not be entitled to any rights of a holder of Preferred
Shares for which the Rights shall be exercisable, including, without
limitation, the right to vote, to receive dividends or other distributions or
to exercise any preemptive rights, and shall not be entitled to receive any
notice of any proceedings of the Company, except as provided herein.

         Section 11. Adjustment of Purchase Price, Number of Shares or Number
of Rights. The Purchase Price, the number of Preferred Shares or other
securities or property covered by each Right and the number of Rights
outstanding are subject to adjustment from time to time as provided in this
Section 11.

                  (a) (i) In the event the Company shall at any time after the
         date of this Agreement (A) declare a dividend on the Preferred Shares
         payable in Preferred Shares, (B) subdivide the outstanding Preferred
         Shares, (C) combine the outstanding Preferred Shares into a smaller
         number of Preferred Shares or (D) issue any shares of its capital
         stock in a reclassification of the Preferred Shares (including any
         such reclassification in connection with a consolidation or merger in
         which the Company is the continuing or surviving corporation),


                                     -17-

<PAGE>   21
         except as otherwise provided in this Section 11(a), the Purchase Price
         in effect at the time of the record date for such dividend or of the
         effective date of such subdivision, combination or reclassification,
         and the number and kind of shares of capital stock issuable on such
         date, shall be proportionately adjusted so that the holder of any
         Right exercised after such time shall be entitled to receive the
         aggregate number and kind of shares of capital stock which, if such
         Right had been exercised immediately prior to such date and at a time
         when the Preferred Share transfer books of the Company were open, such
         holder would have owned upon such exercise and been entitled to
         receive by virtue of such dividend, subdivision, combination or
         reclassification; provided, however, that in no event shall the
         consideration to be paid upon the exercise of one Right be less than
         the aggregate par value of the shares of capital stock of the Company
         issuable upon exercise of one Right.

                  (ii) Subject to Sections 23 and 24 of this Agreement, in the
         event any Person becomes an Acquiring Person, then (A) the Purchase
         Price shall be adjusted to be the Purchase Price in effect immediately
         prior to such Person becoming an Acquiring Person multiplied by the
         number of one one-hundredths of a Preferred Share for which a Right
         was exercisable immediately prior to such Person becoming an Acquiring
         Person, whether or not such Right was then exercisable, and (B) each
         holder of a Right, except as otherwise provided in this Section
         11(a)(ii) and Subsection 11(a)(iii) hereof, shall thereafter have the
         right to receive, upon exercise at a price equal to the Purchase Price
         (as so adjusted), in accordance with the terms of this Agreement and
         in lieu of Preferred Shares, such number of shares of Common Stock of
         the Company as shall equal the result obtained by (x) multiplying the
         then current Purchase Price by the number of one one-hundredths of a
         Preferred Share for which a Right is then exercisable and dividing
         that product by (y) 50%

                                      -18-

<PAGE>   22

         of the then current per share market price of the Company's Common
         Stock (determined pursuant to Section 11(d) hereof) on the date such
         Person became an Acquiring Person; provided, however, that the
         Purchase Price and the number of shares of Common Stock so receivable
         upon exercise of a Right shall thereafter be subject to further
         adjustment as appropriate in accordance with Section 11(f) hereof.
         Notwithstanding anything in this Agreement to the contrary, however,
         from and after the time (the "Invalidation Time") when any Person
         first becomes an Acquiring Person, any Rights that are beneficially
         owned by (x) any Acquiring Person (or any Affiliate or Associate of
         any Acquiring Person), (y) a transferee of any Acquiring Person (or
         any such Affiliate or Associate) who becomes a transferee after the
         Invalidation Time or (z) a transferee of any Acquiring Person (or any
         such Affiliate or Associate) who became a transferee prior to or
         concurrently with the Invalidation Time pursuant to either (I) a
         transfer from the Acquiring Person to holders of its equity securities
         or to any person with whom it has any continuing agreement,
         arrangement or understanding regarding the transferred Rights or (II)
         a transfer which the Board of Directors has determined is part of a
         plan, arrangement or understanding which has the purpose or effect of
         avoiding the provisions of this paragraph, and subsequent transferees
         of such Persons, shall be void without any further action and any
         holder of such Rights shall thereafter have no rights whatsoever with
         respect to such Rights under any provision of this Agreement. The
         Company shall use all reasonable efforts to ensure that the provisions
         of this Section 11(a)(ii) are complied with, but shall have no
         liability to any holder of Right Certificates or other Person as a
         result of its failure to make any determinations with respect to an
         Acquiring Person or its Affiliates, Associates or transferees
         hereunder. From and after the Invalidation Time, no Right Certificate
         shall be issued pursuant to Section 3 or Section 6 hereof that


                                      -19-

<PAGE>   23
         represents Rights that are or have become void pursuant to the
         provisions of this paragraph, and any Right Certificate delivered to
         the Rights Agent that represents Rights that are or have become void
         pursuant to the provisions of this paragraph shall be canceled. From
         and after the occurrence of an event specified in Section 13(a) hereof,
         any Rights that theretofore have not been exercised pursuant to this
         Section 11(a)(ii) shall thereafter be exercisable only in accordance
         with Section 13 and not pursuant to this Section 11(a)(ii).
         Notwithstanding the occurrence of an adjustment in accordance with this
         Section 11(a)(ii), the Rights (other than those that have been
         invalidated pursuant to this Section 11(a)(ii)), shall remain subject
         to redemption pursuant to Section 23 hereof on the terms set forth
         herein.

                  (iii) In the event that there shall not be sufficient shares
         of Common Stock issued but not outstanding or authorized but unissued
         to permit the exercise in full of the Rights in accordance with the
         subparagraph (ii) of this Section 11(a), the Company shall take all
         such action as may be necessary to authorize additional shares of
         Common Stock for issuance upon exercise of the Rights. In the event
         the Company shall, after good faith effort, be unable to take all such
         action as may be necessary to authorize such additional shares of
         Common Stock the Company shall, to the extent permitted by applicable
         law and any material agreements then in effect to which the Company is
         a party, (A) determine the excess of (1) the value of the shares of
         Common Stock issuable upon the exercise of a Right in accordance with
         the foregoing subparagraph (ii) (the "Current Value") over (2) the
         then current Purchase Price multiplied by the number of one
         one-hundredths of Preferred Shares for which a Right was exercisable
         immediately prior to the time that the Acquiring Person became such
         (such excess, the "Spread"), and (B) with respect to each Right (other
         than Rights which have become void pursuant to Section 11(a)(ii)),
         make adequate provision to


                                      -20-

<PAGE>   24

         substitute for the shares of Common Stock issuable in accordance with
         subparagraph (ii) upon exercise of the Right and payment of the
         applicable Purchase Price, (1) cash, (2) a reduction in the Purchase
         Price, (3) Preferred Shares or other equity securities of the Company
         (including, without limitation, shares or fractions of shares of
         preferred stock which, by virtue of having dividend, voting and
         liquidation rights substantially comparable to those of the shares of
         Common Stock, are deemed in good faith by the Board of Directors to
         have substantially the same value as the shares of Common Stock (such
         shares of preferred stock and shares or fractions of shares of
         preferred stock are hereinafter referred to as "Common Stock
         equivalents")), (4) debt securities of the Company, (5) other assets,
         or (6) any combination of the foregoing, having a value which, when
         added to the value of the shares of Common Stock actually issued upon
         exercise of such Right, shall have an aggregate value equal to the
         Current Value (less the amount of any reduction in the Purchase
         Price), where such aggregate value has been determined by the Board of
         Directors upon the advice of a nationally recognized investment
         banking firm selected in good faith by the Board of Directors;
         provided, however, that if the Company shall not make adequate
         provision to deliver value pursuant to clause (B) above within 30 days
         following the date that the Acquiring Person became such (the "Section
         11(a)(ii) Trigger Date"), then the Company shall be obligated to
         deliver, to the extent permitted by applicable law and any material
         agreements then in effect to which the Company is a party, upon the
         surrender for exercise of a Right and without requiring payment of the
         Purchase Price, shares of Common Stock (to the extent available), and
         then, if necessary, such number of fractions of shares of Preferred
         Stock (to the extent available) and then, if necessary, cash, which
         shares and/or cash have an aggregate value equal to the Spread. If,
         upon the date any Person becomes an



                                      -21-

<PAGE>   25

         Acquiring Person, the Board of Directors shall determine in good faith
         that it is likely that sufficient additional shares of Common Stock
         could be authorized for issuance upon exercise in full of the Rights,
         then, if the Board of Directors so elects, the 30-day period set forth
         above may be extended to the extent necessary, but not more than 90
         days after the Section 11(a)(ii) Trigger Date, in order that the
         Company may seek stockholder approval for the authorization of such
         additional shares (such 30-day period, as it may be extended, is
         herein called the "Substitution Period"). To the extent that the
         Company determines that some action need be taken pursuant to the
         second and/or third sentence of this Section 11(a)(iii), the Company
         (x) shall provide, subject to Section 11(a)(ii) hereof and the last
         sentence of this Section 11(a)(iii) hereof, that such action shall
         apply uniformly to all outstanding Rights and (y) may suspend the
         exercisability of the Rights until the expiration of the Substitution
         Period in order to seek any authorization of additional shares and/or
         to decide the appropriate form of distribution to be made pursuant to
         such second sentence and to determine the value thereof. In the event
         of any such suspension, the Company shall issue a public announcement
         stating that the exercisability of the Rights has been temporarily
         suspended, as well as a public announcement at such time as the
         suspension is no longer in effect. For purposes of this Section
         11(a)(iii), the value of the shares of Common Stock shall be the
         current per share market price (as determined pursuant to Section
         11(d)(i)) on the Section 11(a)(ii) Trigger Date and the per share or
         fractional value of any "Common Stock equivalent" shall be deemed to
         equal the current per share market price of the Common Stock. The
         Board of Directors of the Company may, but shall not be required to,
         establish procedures to allocate the right to receive shares of Common
         Stock upon the exercise of the Rights among holders of Rights pursuant
         to this Section 11(a)(iii).

                                     -22-

<PAGE>   26

         (b) In case the Company shall fix a record date for the issuance of
rights, options or warrants to all holders of Preferred Stock entitling them
(for a period expiring within 45 calendar days after such record date) to
subscribe for or purchase Preferred Shares (or shares having the same rights,
privileges and preferences as the Preferred Shares ("equivalent preferred
shares")) or securities convertible into Preferred Shares or equivalent
preferred shares at a price per Preferred Share or equivalent preferred share
(or having a conversion price per share, if a security convertible into
Preferred Shares or equivalent preferred shares) less than the then current per
share market price of the Preferred Shares on such record date, the Purchase
Price to be in effect after such record date shall be determined by multiplying
the Purchase Price in effect immediately prior to such record date by a
fraction, the numerator of which shall be the number of Preferred Shares
outstanding on such record date plus the number of Preferred Shares which the
aggregate offering price of the total number of Preferred Shares and/or
equivalent preferred shares so to be offered (and/or the aggregate initial
conversion price of the convertible securities so to be offered) would purchase
at such current market price and the denominator of which shall be the number
of Preferred Shares outstanding on such record date plus the number of
additional Preferred Shares and/or equivalent preferred shares to be offered
for subscription or purchase (or into which the convertible securities so to be
offered are initially convertible); provided, however, that in no event shall
the consideration to be paid upon the exercise of one Right be less than the
aggregate par value of the shares of capital stock of the Company issuable upon
exercise of one Right. In case such subscription price may be paid in a
consideration part or all of which shall be in a form other than cash, the
value of such consideration shall be as determined in good faith by the Board
of Directors of the Company, whose determination shall be described in a
statement filed with the Rights Agent. Preferred Shares owned by or held for
the account of the Company shall not be deemed outstanding for the purpose of
any such


                                      -23-

<PAGE>   27

computation. Such adjustment shall be made successively whenever such a record
date is fixed; and in the event that such rights, options or warrants are not
so issued, the Purchase Price shall be adjusted to be the Purchase Price that
would then be in effect if such record date had not been fixed.

         (c) In case the Company shall fix a record date for the making of a
distribution to all holders of the Preferred Shares (including any such
distribution made in connection with a consolidation or merger in which the
Company is the continuing or surviving corporation) of evidences of
indebtedness or assets (other than a regular quarterly cash dividend or a
dividend payable in Preferred Shares) or subscription rights or warrants
(excluding those referred to in Section 11(b) hereof), the Purchase Price to be
in effect after such record date shall be determined by multiplying the
Purchase Price in effect immediately prior to such record date by a fraction,
the numerator of which shall be the then current per share market price of the
Preferred Shares on such record date, less the fair market value (as determined
in good faith by the Board of Directors of the Company, whose determination
shall be described in a statement filed with the Rights Agent) of the portion
of the assets or evidences of indebtedness so to be distributed or of such
subscription rights or warrants applicable to one Preferred Share and the
denominator of which shall be such current per share market price of the
Preferred Shares; provided, however, that in no event shall the consideration
to be paid upon the exercise of one Right be less than the aggregate par value
of the shares of capital stock of the Company to be issued upon exercise of one
Right. Such adjustments shall be made successively whenever such a record date
is fixed; and in the event that such distribution is not so made, the Purchase
Price shall again be adjusted to be the Purchase Price which would then be in
effect if such record date had not been fixed.

         (d)(i) For the purpose of any computation hereunder, the "current per
share market price" of any security (a "Security" for the purpose of this
Section 11(d)(i)) on any date shall be deemed

                                     -24-

<PAGE>   28

to be the average of the daily closing prices per share of such Security for
the 30 consecutive Trading Days immediately prior to such date; provided,
however, that in the event that the current per share market price of the
Security is determined during a period following the announcement by the issuer
of such Security of (A) a dividend or distribution on such Security payable in
shares of such Security or securities convertible into such shares, or (B) any
subdivision, combination or reclassification of such Security and prior to the
expiration of 30 Trading Days after the ex-dividend date for such dividend or
distribution, or the record date for such subdivision, combination or
reclassification then, and in each such case, the current per share market
price shall be appropriately adjusted to reflect the current market price per
share equivalent of such Security. The closing price for each day shall be the
last sale price, regular way, or, in case no such sale takes place on such day,
the average of the closing bid and asked prices, regular way in either case, as
reported in the principal consolidated transaction reporting system with
respect to securities listed on the principal national securities exchange on
which the Security is listed or admitted to trading or, if the Security is not
listed or admitted to trading on any national securities exchange, the last
quoted price or, if not so quoted, the average of the high bid and low asked
prices in the over-the-counter market, as reported by Nasdaq or such other
system then in use, or, if on any such date the Security is not quoted by any
such organization, the average of the closing bid and asked prices as furnished
by a professional market maker making a market in the Security selected by the
Board of Directors of the Company. The term "Trading Day" shall mean a day on
which the principal national securities exchange on which the Security is
listed or admitted to trading is open for the transaction of business or, if
the Security is not listed or admitted to trading on any national securities
exchange, a Business Day.

         (ii) For the purpose of any computation hereunder, the "current per
share market price" of the Preferred Shares shall be determined in accordance
with the method set forth in



                                      -25-

<PAGE>   29

Section 11(d)(i). If the Preferred Shares are not publicly traded, the "current
per share market price" of the Preferred Shares shall be conclusively deemed to
be the current per share market price of the Common Shares as determined
pursuant to Section 11(d)(i) (appropriately adjusted to reflect any stock
split, stock dividend or similar transaction occurring after the date hereof),
multiplied by 100. If neither the Common Shares nor the Preferred Shares is
publicly held or so listed or traded, "current per share market price" shall
mean the fair value per share as determined in good faith by the Board of
Directors of the Company, whose determination shall be described in a statement
filed with the Rights Agent.

         (e) No adjustment in the Purchase Price shall be required unless such
adjustment would require an increase or decrease of at least 1% in the Purchase
Price; provided, however, that any adjustments which by reason of this Section
11(e) are not required to be made shall be carried forward and taken into
account in any subsequent adjustment. All calculations under this Section 11
shall be made to the nearest cent or to the nearest one ten-thousandth of a
Preferred Share or one ten-thousandth of any other share or security as the
case may be. Notwithstanding the first sentence of this Section 11(e), any
adjustment required by this Section 11 shall be made no later than the earlier
of (i) three years from the date of the transaction which require such
adjustment and (ii) the date of the expiration of the right to exercise any
Rights.

         (f) If, as a result of an adjustment made pursuant to Section 11(a)
hereof, the holder of any Right thereafter exercised shall become entitled to
receive any shares of capital stock of the Company other than Preferred Shares,
thereafter the number of such other shares so receivable upon exercise of any
Right shall be subject to adjustment from time to time in a manner and on terms
as nearly equivalent as practicable to the provisions with respect to the
Preferred Shares contained in


                                      -26-

<PAGE>   30

Section 11(a) through (c), inclusive, and the provisions of Sections 7, 9, 10
and 13 with respect to the Preferred Shares shall apply on like terms to any
such other shares.

         (g) All Rights originally issued by the Company subsequent to any
adjustment made to the Purchase Price hereunder shall evidence the right to
purchase, at the adjusted Purchase Price, the number of one one-hundredths of a
Preferred Share purchasable from time to time hereunder upon exercise of the
Rights, all subject to further adjustment as provided herein.

         (h) Unless the Company shall have exercised its election as provided
in Section 11(i), upon each adjustment of the Purchase Price as a result of the
calculations made in Sections 11(b) and (c), each Right outstanding immediately
prior to the making of such adjustment shall thereafter evidence the right to
purchase, at the adjusted Purchase Price, that number of one one-hundredths of
a Preferred Share (calculated to the nearest one ten-thousandth of a Preferred
Share) obtained by (A) multiplying (x) the number of one one-hundredths of a
share covered by a Right immediately prior to this adjustment by (y) the
Purchase Price in effect immediately prior to such adjustment of the Purchase
Price and (B) dividing the product so obtained by the Purchase Price in effect
immediately after such adjustment of the Purchase Price.

         (i) The Company may elect on or after the date of any adjustment of
the Purchase Price to adjust the number of Rights in substitution for any
adjustment in the number of one one-hundredths of a Preferred Share purchasable
upon the exercise of a Right. Each of the Rights outstanding after such
adjustment of the number of Rights shall be exercisable for the number of one
one-hundredths of a Preferred Share for which a Right was exercisable
immediately prior to such adjustment. Each Right held of record prior to such
adjustment of the number of Rights shall become that number of Rights
(calculated to the nearest one ten-thousandth) obtained by dividing the
Purchase Price in effect immediately prior to adjustment of the Purchase Price
by the Purchase


                                      -27-

<PAGE>   31


Price in effect immediately after adjustment of the Purchase Price. The Company
shall make a public announcement of its election to adjust the number of
Rights, indicating the record date for the adjustment and, if known at the
time, the amount of the adjustment to be made. This record date may be the date
on which the Purchase Price is adjusted or any day thereafter, but, if the
Right Certificates have been issued, such record date shall be at least 10 days
later than the date of the public announcement. If Right Certificates have been
issued, upon each adjustment of the number of Rights pursuant to this Section
11(i), the Company shall, as promptly as practicable, cause to be distributed
to holders of record of Right Certificates on such record date Right
Certificates evidencing, subject to Section 14 hereof, the additional Rights to
which such holders shall be entitled as a result of such adjustment, or, at the
option of the Company, shall cause to be distributed to such holders of record
in substitution and replacement for the Right Certificates held by such holders
prior to the date of adjustment, and upon surrender thereof, if required by the
Company, new Right Certificates evidencing all the Rights to which such holders
shall he entitled after such adjustment. Right Certificates to be so
distributed shall be issued, executed and countersigned in the manner provided
for herein and shall be registered in the names of the holders of record of
Right Certificates on the record date specified in the public announcement.

         (j) Irrespective of any adjustment or change in the Purchase Price or
the number of one one-hundredths of a Preferred Share issuable upon the
exercise of the Rights, the Right Certificates theretofore and thereafter
issued may continue to express the Purchase Price and the number of one
one-hundredths of a Preferred Share which were expressed in the initial Right
Certificates issued hereunder.

         (k) Before taking any action that would cause an adjustment reducing
the Purchase Price below one one-hundredth of the then par value, if any, of
the Preferred Shares or other shares of



                                      -28-

<PAGE>   32

capital stock issuable upon exercise of the Rights, the Company shall take any
corporate action which may, in the opinion of its counsel, be necessary in
order that the Company may validly and legally issue fully paid and
nonassessable Preferred Shares or other such shares at such adjusted Purchase
Price.

         (l) In any case in which this Section 11 shall require that an
adjustment in the Purchase Price be made effective as of a record date for a
specified event, the Company may elect to defer until the occurrence of such
event the issuing to the holder of any Right exercised after such record date
of the Preferred Shares and other capital stock or securities of the Company,
if any, issuable upon such exercise over and above the Preferred Shares and
other capital stock or securities of the Company, if any, issuable upon such
exercise on the basis of the Purchase Price in effect prior to such adjustment;
provided, however, that the Company shall deliver to such holder a due bill or
other appropriate instrument evidencing such holder's right to receive such
additional shares upon the occurrence of the event requiring such adjustment.

         (m) Anything in this Section 11 to the contrary notwithstanding, the
Company shall be entitled to make such reductions in the Purchase Price, in
addition to those adjustments expressly required by this Section 11, as and to
the extent that it, in its sole discretion, shall determine to be advisable in
order that any consolidation or subdivision of the Preferred Shares, issuance
wholly for cash of any Preferred Shares at less than the current market price,
issuance wholly for cash of Preferred Shares or securities which by their terms
are convertible into or exchangeable for Preferred Shares, dividends on
Preferred Shares payable in Preferred Shares or issuance of rights, options or
warrants referred to hereinabove in Section 11(b), hereafter made by the
Company to holders of its Preferred Shares shall not be taxable to such
stockholders.


                                     -29-

<PAGE>   33

         (n) In the event that at any time after the date of this Agreement and
prior to the Distribution Date, the Company shall (i) declare or pay any
dividend on the Common Stock payable in Common Shares or (ii) effect a
subdivision, combination or consolidation of the Common Stock (by
reclassification or otherwise than by payment of dividends in Common Shares)
into a greater or lesser number of shares of Common Stock, then in any such
case the Rights associated with each share of Common Stock following any such
event shall equal the result obtained by multiplying the number of Rights
associated with each share of Common Stock immediately prior to such event by a
fraction, of which the numerator shall be equal to the number of shares of
Common Stock outstanding immediately prior to the occurrence of the event and
of which the denominator shall be equal to the total number of shares of Common
Stock outstanding immediately following the occurrence of such event. The
adjustments provided for in this Section 11(n) shall be made successively
whenever such a dividend is declared or paid or such a subdivision, combination
or consolidation is effected.

         Section 12. Certificate of Adjusted Purchase Price or Number of
Shares. Whenever an adjustment is made as provided in Section 11 or 13 hereof,
the Company shall promptly (a) prepare a certificate setting forth such
adjustment, and a brief statement of the facts accounting for such adjustment,
(b) file with the Rights Agent and with each transfer agent for the Common
Stock or the Preferred Stock a copy of such certificate and (c) mail a brief
summary thereof to each holder of a Right Certificate in accordance with
Section 23 hereof. The Rights Agent shall be fully protected in relying on any
such certificate and on any adjustment therein contained and shall not be
obligated or responsible for calculating any adjustment nor shall it be deemed
to have knowledge of such adjustment unless and until it shall have received
such certificate.

                                     -30-

<PAGE>   34

         Section 13. Consolidation, Merger or Sale or Transfer of Assets or
Earning Power. (a) In the event, directly or indirectly, at any time after a
Person has become an Acquiring Person, (i) the Company shall consolidate with,
or merge with and into, any other Person, (ii) any Person shall consolidate with
the Company, or merge with and into the Company and the Company shall be the
continuing or surviving corporation of such merger and, in connection with such
merger, all or part of the Common Shares shall be changed into or exchanged for
stock or other securities of any other Person (or the Company) or cash or any
other property, or (iii) the Company shall sell or otherwise transfer (or one or
more of its Subsidiaries shall sell or otherwise transfer), in one or more
transactions, assets or earning power aggregating 50% or more of the assets or
earning power of the Company and its Subsidiaries (taken as a whole) to any
other Person (other than the Company or one or more of its wholly-owned
Subsidiaries), then, and in each such case, proper provision shall be made so
that (A) each holder of a Right (other than Rights that have become void
pursuant to Section 11(a)(ii)) shall thereafter have the right to receive, upon
the exercise thereof at a price equal to the then current Purchase Price
multiplied by the number of one one-hundredths of a Preferred Share for which a
Right is then exercisable, in accordance with the terms of this Agreement and in
lieu of Preferred Shares, such number of validly issued, fully paid and
non-assessable and freely tradeable shares of Common Stock of the Principal
Party (as defined herein) not subject to any liens, encumbrances, rights of
first refusal or other adverse claims, as shall equal the result obtained by (I)
multiplying the then current Purchase Price by the number of one one-hundredths
of a Preferred Share for which a Right is then exercisable and dividing that
product by (II) 50% of the then current per share market price of the Common
Stock of such Principal Party (determined in accordance with Section 11(d)(i)
hereof) on the date of consummation of such consolidation, merger, sale or
transfer; provided that the Purchase Price and the number of shares of Common
Stock of such Principal Party



                                      -31-

<PAGE>   35

issuable upon exercise of each Right shall be further adjusted as provided in
Section 11(f) of this Agreement to reflect any events occurring in respect of
such Principal Party after the date of such consolidation, merger, sale or
transfer; (B) such Principal Party shall thereafter be liable for, and shall
assume, by virtue of such consolidation, merger, sale or transfer, all the
obligations and duties of the Company pursuant to this Agreement; (C) the term
"Company" shall thereafter be deemed to refer to such Principal Party; and (D)
such Principal Party shall take such steps (including, but not limited to, the
reservation of a sufficient number of its shares of Common Stock in accordance
with Section 9 hereof) in connection with such consummation of any such
transaction as may be necessary to assure that the provisions hereof shall
thereafter be applicable, as nearly as reasonably may be, in relation to the
shares of its Common Stock thereafter deliverable upon the exercise of the
Rights; provided that, upon the subsequent occurrence of any consolidation,
merger, sale or transfer of assets or other extraordinary transaction in
respect of such Principal Party, each holder of a Right shall thereupon be
entitled to receive, upon exercise of a Right and payment of the Purchase Price
as provided in this Section 13(a), such cash, shares, rights, warrants and
other property which such holder would have been entitled to receive had such
holder, at the time of such transaction, owned the Common Stock of the
Principal Party receivable upon the exercise of a Right pursuant to this
Section 13(a), and such Principal Party shall take such steps (including, but
not limited to, reservation of shares of stock) as may be necessary to permit
the subsequent exercise of the Rights in accordance with the terms hereof for
such cash, shares, rights, warrants and other property.

         (b) As used in this Section 13, "Principal Party" shall mean

                  (i) in the case of any transaction described in clause (i) or
         (ii) of the first sentence of Section 13(a) hereof: (A) the Person
         that is the issuer of the securities into which the shares of Common
         Stock are converted in such merger or consolidation, or, if there is
         more



                                      -32-

<PAGE>   36

         than one such issuer, the issuer the shares of Common Stock of which
         have the greatest aggregate market value of shares outstanding, or (B)
         if no securities are so issued, (x) the Person that is the other party
         to the merger, if such Person survives said merger, or, if there is
         more than one such Person, the Person the shares of Common Stock of
         which have the greatest aggregate market value of shares outstanding
         or (y) if the Person that is the other party to the merger does not
         survive the merger, the Person that does survive the merger (including
         the Company if it survives) or (z) the Person resulting from the
         consolidation; and

                  (ii) in the case of any transaction described in clause (iii)
         of the first sentence in Section 13(a) hereof, the Person that is the
         party receiving the greatest portion of the assets or earning power
         transferred pursuant to such transaction or transactions, or, if each
         Person that is a party to such transaction or transactions receives
         the same portion of the assets or earning power so transferred or if
         the Person receiving the greatest portion of the assets or earning
         power cannot be determined, whichever of such Persons as is the issuer
         of Common Stock having the greatest aggregate market value of shares
         outstanding; provided, however, that in any such case described in the
         foregoing clause (b)(i) or (b)(ii), if the Common Stock of such Person
         is not at such time or has not been continuously over the preceding
         12-month period registered under Section 12 of the Exchange Act, then
         (1) if such Person is a direct or indirect Subsidiary of another
         Person the Common Stock of which is and has been so registered, the
         term "Principal Party" shall refer to such other Person, or (2) if
         such Person is a Subsidiary, directly or indirectly, of more than one
         Person, and the Common Stock of all of such persons have been so
         registered, the term "Principal Party" shall refer to whichever of
         such Persons is the issuer of Common Stock having the greatest
         aggregate market value of shares outstanding, or (3) if such Person is
         owned, directly or indirectly, by



                                      -33-

<PAGE>   37

         a joint venture formed by two or more Persons that are not owned,
         directly or indirectly, by the same Person, the rules set forth in
         clauses (1) and (2) above shall apply to each of the owners having an
         interest in the venture as if the Person owned by the joint venture
         was a Subsidiary of both or all of such joint venturers, and the
         Principal Party in each such case shall bear the obligations set forth
         in this Section 13 in the same ratio as its interest in such Person
         bears to the total of such interests.

         (c) The Company shall not consummate any consolidation, merger, sale
or transfer referred to in Section 13(a) hereof unless prior thereto the
Company and the Principal Party involved therein shall have executed and
delivered to the Rights Agent an agreement confirming that the requirements of
Sections 13(a) and (b) hereof shall promptly be performed in accordance with
their terms and that such consolidation, merger, sale or transfer of assets
shall not result in a default by the Principal Party under this Agreement as
the same shall have been assumed by the Principal Party pursuant to Sections
13(a) and (b) hereof and providing that, as soon as practicable after executing
such agreement pursuant to this Section 13, the Principal Party will:

                  (i) prepare and file a registration statement under the
         Securities Act, if necessary, with respect to the Rights and the
         securities purchasable upon exercise of the Rights on an appropriate
         form, use its best efforts to cause such registration statement to
         become effective as soon as practicable after such filing and use its
         best efforts to cause such registration statement to remain effective
         (with a prospectus at all times meeting the requirements of the
         Securities Act) until the Final Expiration Date, and similarly comply
         with applicable state securities laws;

                  (ii) use its best efforts, if the Common Stock of the
         Principal Party shall be listed or admitted to trading on a national
         securities exchange, to list or admit to trading (or



                                      -34-

<PAGE>   38

         continue the listing of) the Rights and the securities purchasable
         upon exercise of the Rights such securities exchange, or, if the
         Common Stock of the Principal Party shall not be listed or admitted to
         trading on a national securities exchange, to cause the Rights and the
         securities receivable upon exercise of the Rights to be reported by
         such other system then in use;

                  (iii) deliver to holders of the Rights historical financial
         statements for the Principal Party which comply in all respects with
         the requirements for registration on Form 10 (or any successor form)
         under the Exchange Act; and

                  (iv) obtain waivers of any rights of first refusal or
         preemptive rights in respect of the Common Stock of the Principal
         Party subject to purchase upon exercise of outstanding Rights.

         (d) In case the Principal Party has provision in any of its authorized
securities or in its certificate of incorporation or by-laws or other
instrument governing its corporate affairs, which provision would have the
effect of (i) causing such Principal Party to issue (other than to holders of
Rights pursuant to this Section 13), in connection with, or as a consequence
of, the consummation of a transaction referred to in this Section 13, shares of
Common Stock of such Principal Party at less than the then current market price
per share thereof (determined pursuant to Section 11(d) hereof) or securities
exercisable for, or convertible into, Common Stock of such Principal Party at
less than such then current market price, or (ii) providing for any special
payment, tax or similar provision in connection with the issuance of the Common
Stock of such Principal Party pursuant to the provisions of Section 13, then,
in such event, the Company hereby agrees with each holder of Rights that it
shall not consummate any such transaction unless prior thereto the Company and
such Principal Party shall have executed and delivered to the Rights Agent a
supplemental agreement providing that the provision in question of such
Principal Party shall have been canceled, waived or



                                      -35-

<PAGE>   39

amended, or that the authorized securities shall be redeemed, so that the
applicable provision will have no effect in connection with, or as a
consequence of, the consummation of the proposed transaction.

         (e) The Company covenants and agrees that it shall not, at any time
after a Person first becomes an Acquiring Person enter into any transaction of
the type contemplated by any of clauses (i) - (iii) of Section 13(a) hereof if
(x) at the time of or immediately after such consolidation, merger, sale,
transfer or other transaction there are any rights, warrants or other
instruments or securities outstanding or agreements in effect which would
substantially diminish or otherwise eliminate the benefits intended to be
afforded by the Rights, (y) prior to, simultaneously with or immediately after
such consolidation, merger, sale, transfer or other transaction, the
stockholders of the Person who constitutes, or would constitute, the Principal
Party for purposes of Section 13(a) hereof shall have received a distribution
of Rights previously owned by such Person or any of its Affiliates or
Associates or (z) the form or nature of organization of the Principal Party
would preclude or limit the exercisability of the Rights.

         Section 14. Fractional Rights and Fractional Shares. (a) The Company
shall not be required to issue fractions of Rights or to distribute Right
Certificates which evidence fractional Rights. In lieu of such fractional
Rights, there shall be paid to the registered holders of the Right Certificates
with regard to which such fractional Rights would otherwise be issuable, an
amount in cash equal to the same fraction of the current market value of a
whole Right. For the purposes of this Section 14(a), the current market value
of a whole Right shall be the closing price of the Rights for the Trading Day
immediately prior to the date on which such fractional Rights would have been
otherwise issuable. The closing price for any day shall be the last sale price,
regular way, or, in case no such sale takes place on such day, the average of
the closing bid and asked prices, regular way,



                                      -36-

<PAGE>   40

in either case, as reported in the principal consolidated transaction reporting
system with respect to securities listed on the principal national securities
exchange on which the Rights are listed or admitted to trading or, if the
Rights are not listed or admitted to trading on any national securities
exchange, the last quoted price or, if not so quoted, the average of the high
bid and low asked prices in the over-the-counter market, as reported by Nasdaq
or such other system then in use or, if on any such date the Rights are not
quoted by any such organization, the average of the closing bid and asked
prices as furnished by a professional market maker making a market in the
Rights selected by the Board of Directors of the Company. If on any such date
no such market maker is making a market in the Rights, the fair value of the
Rights on such date as determined in good faith by the Board of Directors of
the Company shall be used.

         (b) The Company shall not be required to issue fractions of Preferred
Shares (other than fractions which are integral multiples of one one-hundredth
of a Preferred Share) upon exercise of the Rights or to distribute certificates
which evidence fractional Preferred Shares (other than fractions which are
integral multiples of one one-hundredth of a Preferred Share). Fractions of
Preferred Shares in integral multiples of one one-hundredth of a Preferred
Share may, at the election of the Company, be evidenced by depositary receipts,
pursuant to an appropriate agreement between the Company and a depositary
selected by it; provided that such agreement shall provide that the holders of
such depositary receipts shall have all the rights, privileges and preferences
to which they are entitled as beneficial owners of the Preferred Shares
represented by such depositary receipts. In lieu of fractional Preferred Shares
that are not integral multiples of one one-hundredth of a Preferred Share, the
Company shall pay to the registered holders of Right Certificates at the time
such Rights are exercised as herein provided an amount in cash equal to the
same fraction of the current market value of one Preferred Share. For the
purposes of this Section 14(b), the current market value of a



                                      -37-

<PAGE>   41

Preferred Share shall be the closing price of a Preferred Share (as determined
pursuant to the second sentence of Section 11(d)(i) hereof) for the Trading Day
immediately prior to the date of such exercise.

         (c) The Company shall not be required to issue fractions of shares of
Common Stock or to distribute certificates which evidence fractional shares of
Common Stock upon the exercise or exchange of Rights. In lieu of such
fractional shares of Common Stock, the Company shall pay to the registered
holders of the Right Certificates with regard to which such fractional shares
of Common Stock would otherwise be issuable an amount in cash equal to the same
fraction of the current market value of a whole share of Common Stock (as
determined in accordance with Section 14(a) hereof) for the Trading Day
immediately prior to the date of such exercise or exchange.

         (d) The holder of a Right by the acceptance of the Right expressly
waives his right to receive any fractional Rights or any fractional shares upon
exercise of a Right (except as provided above).

         Section 15. Rights of Action. All rights of action in respect of this
Agreement, excepting the rights of action given to the Rights Agent under
Section 18 hereof, are vested in the respective registered holders of the
Right Certificates (and, prior to the Distribution Date, the registered holders
of the Common Stock); and any registered holder of any Right Certificate (or,
prior to the Distribution Date, of the Common Stock), without the consent of
the Rights Agent or of the holder of any other Right Certificate (or, prior to
the Distribution Date, of the Common Stock), may, in his own behalf and for his
own benefit, enforce, and may institute and maintain any suit, action or
proceeding against the Company to enforce, or otherwise act in respect of, his
right to exercise the Rights evidenced by such Right Certificate in the manner
provided in such Right Certificate and in this Agreement. Without limiting the
foregoing or any remedies available to the holders of Rights,


                                      -38-

<PAGE>   42

it is specifically acknowledged that the holders of Rights would not have an
adequate remedy at law for any breach of this Agreement and will be entitled to
specific performance of the obligations under, and injunctive relief against
actual or threatened violations of the obligations of any Person subject to,
this Agreement.

         Section 16. Agreement of Right Holders. Every holder of a Right, by
accepting the same, consents and agrees with the Company and the Rights Agent
and with every other holder of a Right thus:

                  (a) prior to the Distribution Date, the Rights will be
         transferable only in connection with the transfer of the Common Stock;

                  (b) after the Distribution Date, the Right Certificates are
         transferable only on the registry books of the Rights Agent if
         surrendered at the principal office or agency of the Rights Agent
         designated for such purpose, duly endorsed or accompanied by a proper
         instrument of transfer; and

                  (c) the Company and the Rights Agent may deem and treat the
         Person in whose name the Right Certificate (or, prior to the
         Distribution Date, the associated Common Stock certificate) is
         registered as the absolute owner thereof and of the Rights evidenced
         thereby (notwithstanding any notations of ownership or writing on the
         Right Certificates or the associated Common Stock certificate made by
         anyone other than the Company or the Rights Agent) for all purposes
         whatsoever, and neither the Company nor the Rights Agent shall be
         affected by any notice to the contrary.

         Section 17. Right Certificate Holder Not Deemed a Stockholder. No
holder, as such, of any Right Certificate shall be entitled to vote, receive
dividends or be deemed for any purpose the holder of the Preferred Shares or any
other securities of the Company which may at any time be issuable


                                      -39-

<PAGE>   43

on the exercise of the Rights represented thereby, nor shall anything contained
herein or in any Right Certificate be construed to confer upon the holder of
any Right Certificate, as such, any of the rights of a stockholder of the
Company or any right to vote for the election of directors or upon any matter
submitted to stockholders at any meeting thereof, or to give or withhold
consent to any corporate action, or to receive notice of meetings or other
actions affecting stockholders (except as provided in Section 25 hereof), or to
receive dividends or subscription rights, or otherwise, until the Right or
Rights evidenced by such Right Certificate shall have been exercised in
accordance with the provisions hereof.

         Section 18. Concerning the Rights Agent. (a) The Company agrees to pay
to the Rights Agent reasonable compensation for all services rendered by it
hereunder and, from time to time, on demand of the Rights Agent, its reasonable
expenses and counsel fees and other disbursements incurred in the
administration and execution of this Agreement and the exercise and performance
of its duties hereunder. The Company also agrees to indemnify the Rights Agent
for, and to hold it harmless against, any loss, liability or expense incurred
without negligence, bad faith or willful misconduct on the part of the Rights
Agent for anything done or omitted by the Rights Agent in connection with the
acceptance and administration of this Agreement, including the costs and
expenses of defending against any claim of liability arising therefrom,
directly or indirectly. The indemnification provided for hereunder shall
survive the expiration of the Rights and the termination of this Agreement. The
costs and expenses incurred in enforcing this right of indemnification shall
also be paid by the Company.

         (b) The Rights Agent may conclusively rely upon and shall be protected
and shall incur no liability for, or in respect of any action taken, suffered
or omitted by it in connection with, its administration of this Agreement in
reliance upon any Right Certificate or certificate for the


                                      -40-

<PAGE>   44


Preferred Stock or Common Stock or for other securities of the Company,
instrument of assignment or transfer, power of attorney, endorsement,
affidavit, letter, notice, direction, consent, certificate, statement, or other
paper or document believed by it to be genuine and to be signed, executed and,
where necessary, verified or acknowledged, by the proper Person or Persons, or
otherwise upon the advice of counsel as set forth in Section 20 hereof.
Notwithstanding anything in this Agreement to the contrary, in no event shall
the Rights Agent be liable for special, indirect or consequential loss or
damage of any kind whatsoever (including but not limited to lost profits), even
if the Rights Agent has been advised of the likelihood of such loss or damage
and regardless of the form of the action.

         Section 19. Merger or Consolidation or Change of Name of Rights Agent.
(a) Any corporation into which the Rights Agent or any successor Rights Agent
may be merged or with which it may be consolidated, or any corporation
resulting from any merger or consolidation to which the Rights Agent or any
successor Rights Agent shall be a party, or any corporation succeeding to the
stock transfer or corporate trust powers of the Rights Agent or any successor
Rights Agent, shall be the successor to the Rights Agent under this Agreement
without the execution or filing of any paper or any further act on the part of
any of the parties hereto; provided that such corporation would be eligible for
appointment as a successor Rights Agent under the provisions of Section 21
hereof. In case at the time such successor Rights Agent shall succeed to the
agency created by this Agreement, any of the Right Certificates shall have been
countersigned but not delivered, any such successor Rights Agent may adopt the
countersignature of the predecessor Rights Agent and deliver such Right
Certificates so countersigned; and in case at that time any of the Right
Certificates shall not have been countersigned, any successor Rights Agent may
countersign such Right Certificates either in the name of the predecessor
Rights Agent or in the name of the successor


                                      -41-

<PAGE>   45

Rights Agent; and in all such cases such Right Certificates shall have the full
force provided in the Right Certificates and in this Agreement.

         (b) In case at any time the name of the Rights Agent shall be changed
and at such time any of the Right Certificates shall have been countersigned
but not delivered, the Rights Agent may adopt the countersignature under its
prior name and deliver Right Certificates so countersigned; and in case at that
time any of the Right Certificates shall not have been countersigned, the
Rights Agent may countersign such Right Certificates either in its prior name
or in its changed name; and in all such cases such Right Certificates shall
have the full force provided in the Right Certificates and in this Agreement.

         Section 20. Duties of Rights Agent. The Rights Agent undertakes the
duties and obligations imposed by this Agreement upon the following terms and
conditions, by all of which the Company and the holders of Right Certificates,
by their acceptance thereof, shall be bound, and no implied duties or
obligations shall be read into this Agreement against the Rights Agent:

                  (a) Before the Rights Agent acts or refrains from acting, it
         may consult with legal counsel (who may be legal counsel for the
         Company), and the opinion of such counsel shall be full and complete
         authorization and protection to the Rights Agent as to any action
         taken or omitted by it in good faith and in accordance with such
         opinion.

                  (b) Whenever in the performance of its duties under this
         Agreement the Rights Agent shall deem it necessary or desirable that
         any fact or matter be proved or established by the Company prior to
         taking or suffering any action hereunder, such fact or matter (unless
         other evidence in respect thereof be herein specifically prescribed)
         may be deemed to be conclusively proved and established by a
         certificate signed by any one of the Chairman of the Board, the Chief
         Executive Officer, the President, any Vice President, the Treasurer or


                                      -42-

<PAGE>   46

         the Secretary of the Company and delivered to the Rights Agent; and
         such certificate shall be full authorization to the Rights Agent for
         any action taken or suffered in good faith by it under the provisions
         of this Agreement in reliance upon such certificate.

                  (c) The Rights Agent shall be liable hereunder only for its
         own negligence, bad faith or willful misconduct.

                  (d) The Rights Agent shall not be liable for or by reason of
         any of the statements of fact or recitals contained in this Agreement
         or in the Right Certificates (except its countersignature thereof) or
         be required to verify the same, but all such statements and recitals
         are and shall be deemed to have been made by the Company only.

                  (e) The Rights Agent shall not be under any responsibility in
         respect of the validity of this Agreement or the execution and
         delivery hereof (except the due execution hereof by the Rights Agent)
         or in respect of the validity or execution of any Right Certificate
         (except its countersignature thereof); nor shall it be responsible for
         any breach by the Company of any covenant or condition contained in
         this Agreement or in any Right Certificate; nor shall it be
         responsible for any change in the exercisability of the Rights
         (including the Rights becoming void in accordance with Section
         11(a)(ii) hereof) or any adjustment in the terms of the Rights
         (including the manner, method or amount thereof) provided for in
         Section 3, 11, 13, 23 or 24, or the ascertaining of the existence of
         facts that would require any such change or adjustment (except with
         respect to the exercise of Rights evidenced by Right Certificates
         after actual notice that such change or adjustment is required); nor
         shall it by any act hereunder be deemed to make any representation or
         warranty as to the authorization or reservation of any Preferred
         Shares to be issued pursuant to this

                                      -43-

<PAGE>   47

         Agreement or any Right Certificate or as to whether any Preferred
         Shares will, when issued, be validly authorized and issued, fully paid
         and nonassessable.

                  (f) The Company agrees that it will perform, execute,
         acknowledge and deliver or cause to be performed, executed,
         acknowledged and delivered all such further and other acts,
         instruments and assurances as may reasonably be required by the Rights
         Agent for the carrying out or performing by the Rights Agent of the
         provisions of this Agreement.

                  (g) The Rights Agent is hereby authorized and directed to
         accept instructions with respect to the performance of its duties
         hereunder from any one of the Chairman of the Board, the Chief
         Executive Officer, the President, any Vice President, the Secretary or
         the Treasurer of the Company, and to apply to such officers for advice
         or instructions in con nection with its duties, and it shall not be
         liable for any action taken or suffered by it in good faith in
         accordance with instructions of any such officer or for any delay in
         acting while waiting for those instructions. Any application by the
         Rights Agent for written instructions from the Company may, at the
         option of the Rights Agent, set forth in writing any action proposed
         to be taken or omitted by the Rights Agent under this Agreement and
         the date on and/or after which such action shall be taken or such
         omission shall be effective. The Rights Agent shall not be liable for
         any action taken by, or omission of, the Rights Agent in accordance
         with a proposal included in any such application on or after the date
         specified in such application (which date shall not be less than five
         Business Days after the date any officer of the Company actually
         receives such application, unless any such officer shall have
         consented in writing to an earlier date) unless, prior to taking any
         such action (or the effective date in the case of an omission), the
         Rights Agent shall have received written instructions in response to
         such application specifying the action to be taken or omitted.


                                     -44-
<PAGE>   48

                  (h) The Rights Agent and any stockholder, director, officer
         or employee of the Rights Agent may buy, sell or deal in any of the
         Rights or other securities of the Company or become pecuniarily
         interested in any transaction in which the Company may be interested,
         or contract with or lend money to the Company or otherwise act as
         fully and freely as though it were not Rights Agent under this
         Agreement. Nothing herein shall preclude the Rights Agent from acting
         in any other capacity for the Company or for any other legal entity.

                  (i) The Rights Agent may execute and exercise any of the
         rights or powers hereby vested in it or perform any duty hereunder
         either itself or by or through its attorneys or agents, and the Rights
         Agent shall not be answerable or accountable for any act, default,
         neglect or misconduct of any such attorneys or agents or for any loss
         to the Company resulting from any such act, default, neglect or
         misconduct.

                  (j) If, with respect to any Rights Certificate surrendered to
         the Rights Agent for exercise or transfer, the certificate contained
         in the form of assignment or the form of election to purchase set
         forth on the reverse thereof, as the case may be, has not been
         completed to certify the holder is not an Acquiring Person (or an
         Affiliate or Associate thereof), the Rights Agent shall not take any
         further action with respect to such requested exercise or transfer
         without first consulting with the Company.

                  (k) No provision of this Agreement shall require the Rights
         Agent to expend or risk its own funds or otherwise incur any financial
         liability in the performance of any of its duties hereunder or in the
         exercise of its rights if there shall be reasonable grounds for
         believing that repayment of such funds or adequate indemnification
         against such risk or liability is not reasonably assured to it.


                                     -45-

<PAGE>   49

                  (l) The Rights Agent shall not be required to take notice or
         be deemed to have notice of any fact, event or determination
         (including, without limitation, any dates or events defined in this
         Agreement or the designation of any Person as an Acquiring Person,
         Affiliate, Associate or Subsidiary) under this Agreement unless and
         until the rights Agent shall be specifically notified in writing by
         the Company of such fact, event or determination.

         Section 21. Change of Rights Agent. The Rights Agent or any successor
Rights Agent may resign and be discharged from its duties under this Agreement
upon 30 days' notice in writing mailed to the Company and to each transfer
agent of the Common Stock or Preferred Stock by registered or certified mail,
and, at the expense of the Company, to the holders of the Right Certificates by
first-class mail. The Company may remove the Rights Agent or any successor
Rights Agent upon 30 days' notice in writing, mailed to the Rights Agent or
successor Rights Agent, as the case may be, and to each transfer agent of the
Common Stock or Preferred Stock by registered or certified mail, and to the
holders of the Right Certificates by first-class mail. If the Rights Agent
shall resign or be removed or shall otherwise become incapable of acting, the
Company shall appoint a successor to the Rights Agent. If the Company shall
fail to make such appointment within a period of 30 days after giving notice of
such removal or after it has been notified in writing of such resignation or
incapacity by the resigning or incapacitated Rights Agent or by the holder of a
Right Certificate (who shall, with such notice, submit his Right Certificate
for inspection by the Company), then the registered holder of any Right
Certificate may apply to any court of competent jurisdiction for the
appointment of a new Rights Agent. Any successor Rights Agent, whether
appointed by the Company or by such a court shall be a corporation organized
and doing business under the laws of the United States (or of any state of the
United States so long as such corporation is authorized to do business as a
banking institution in such state), in good standing, which is authorized under
such


                                      -46-

<PAGE>   50

laws to exercise corporate trust or stock transfer powers and is subject to
supervision or examination by federal or state authority and which has at the
time of its appointment as Rights Agent a combined capital and surplus of at
least $50 million. After appointment, the successor Rights Agent shall be
vested with the same powers, rights, duties and responsibilities as if it had
been originally named as Rights Agent without further act or deed; but the
predecessor Rights Agent shall deliver and transfer to the successor Rights
Agent any property at the time held by it hereunder, and execute and deliver
any further assurance, conveyance, act or deed necessary for the purpose. Not
later than the effective date of any such appointment, the Company shall file
notice thereof in writing with the predecessor Rights Agent and each transfer
agent of the Common Stock or Preferred Stock, and mail a notice thereof in
writing to the registered holders of the Right Certificates. Failure to give
any notice provided for in this Section 21, however, or any defect therein,
shall not affect the legality or validity of the resignation or removal of the
Rights Agent or the appointment of the successor Rights Agent, as the case may
be.

         Section 22. Issuance of New Right Certificates. Notwithstanding any of
the provisions of this Agreement or of the Rights to the contrary, the Company
may, at its option, issue new Right Certificates evidencing Rights in such form
as may be approved by its Board of Directors to reflect any adjustment or
change in the Purchase Price and the number or kind or class of shares or other
securities or property purchasable under the Right Certificates made in
accordance with the provisions of this Agreement. In addition, in connection
with the issuance or sale of Common Stock following the Distribution Date and
prior to the earlier of the Redemption Date and the Final Expiration Date, the
Company may with respect to shares of Common Stock so issued or sold pursuant
to (i) the exercise of stock options, (ii) under any employee plan or
arrangement, (iii) upon the exercise, conversion or exchange of securities,
notes or debentures issued by the Company or

                                      -47-

<PAGE>   51

(iv) a contractual obligation of the Company in each case existing prior to the
Distribution Date, issue Rights Certificates representing the appropriate
number of Rights in connection with such issuance or sale.

         Section 23. Redemption. (a) The Board of Directors of the Company may,
at its option, at any time prior to the Close of Business on the 10th business
day after the Shares Acquisition Date, redeem all but not less than all of the
then outstanding Rights at a redemption price of $0.001 per Right,
appropriately adjusted to reflect any stock split, stock dividend or similar
transaction occurring after the date hereof (such redemption price being
hereinafter referred to as the "Redemption Price"). The redemption of the
Rights by the Board of Directors of the Company may be made effective at such
time, on such basis and with such conditions as the Board of Directors of the
Company, in its sole discretion may establish. The Company may, at its option,
pay the Redemption Price in cash, shares of Common Stock (based on the current
market price of the Common Stock at the time of redemption) or any other form
of consideration deemed appropriate by the Board of Directors.

         (b) Immediately upon the action of the Board of Directors of the
Company ordering the redemption of the Rights pursuant to paragraph (a) of this
Section 23 (or at such later time as the Board of Directors may establish for
the effectiveness of such redemption), and without any further action and
without any notice, the right to exercise the Rights will terminate and the
only right thereafter of the holders of Rights shall be to receive the
Redemption Price. The Company shall promptly give public notice of any such
redemption; provided, however, that the failure to give, or any defect in, any
such notice shall not affect the validity of such redemption. Within 10 days
after such action of the Board of Directors of the Company ordering the
redemption of the Rights, the Company shall mail a notice of redemption to all
the holders of the then outstanding Rights at their


                                      -48-

<PAGE>   52

last addresses as they appear upon the registry books of the Rights Agent or,
prior to the Distribution Date, on the registry books of the transfer agent for
the Common Stock. Any notice which is mailed in the manner herein provided
shall be deemed given, whether or not the holder receives the notice. Each such
notice of redemption will state the method by which the payment of the
Redemption Price will be made. Neither the Company nor any of its Affiliates or
Associates may redeem, acquire or purchase for value any Rights at any time in
any manner other than that specifically set forth in this Section 23 or in
Section 24 hereof, and other than in connection with the purchase of Common
Shares prior to the Distribution Date.

         Section 24. Exchange. (a) The Board of Directors of the Company may,
at its option, at any time after any Person first becomes an Acquiring Person,
exchange all or part of the then outstanding and exercisable Rights (which
shall not include Rights that have become void pursuant to the provisions of
Section 11(a)(ii) hereof) for shares of Common Stock at an exchange ratio of
one share of Common Stock per Right, appropriately adjusted to reflect any
stock split, stock dividend or similar transaction occurring after the date
hereof (such exchange ratio being hereinafter referred to as the "Exchange
Ratio"). Notwithstanding the foregoing, the Board of Directors of the Company
shall not be empowered to effect such exchange at any time after any Person
(other than an Exempt Person), together with all Affiliates and Associates of
such Person, becomes the Beneficial Owner of 50% or more of the Common Shares
then outstanding. From and after the occurrence of an event specified in
Section 13(a) hereof, any Rights that theretofore have not been exchanged
pursuant to this Section 24(a) shall thereafter be exercisable only in
accordance with Section 13 and may not be exchanged pursuant to this Section
24(a). The exchange of the Rights by the Board of Directors may be made
effective at such time, on such basis and with such conditions as the Board of
Directors in its sole discretion may establish.


                                     -49-

<PAGE>   53

         (b) Immediately upon the action of the Board of Directors of the
Company ordering the exchange of any Rights pursuant to paragraph (a) of this
Section 24 and without any further action and without any notice, the right to
exercise such Rights shall terminate and the only right thereafter of a holder
of such Rights shall be to receive that number of shares of Common Stock equal
to the number of such Rights hold by such holder multiplied by the Exchange
Ratio. The Company shall promptly give public notice of any such exchange;
provided, however, that the failure to give, or any defect in, such notice
shall not affect the validity of such exchange. The Company promptly shall mail
a notice of any such exchange to all of the holders of such Rights at their
last addresses as they appear upon the registry books of the Rights Agent. Any
notice which is mailed in the manner herein provided shall be deemed given,
whether or not the holder receives the notice. Each such notice of exchange
will state the method by which the exchange of the Common Stock for Rights will
be effected and, in the event of any partial exchange, the number of Rights
which will be exchanged. Any partial exchange shall be effected pro rata based
on the number of Rights (other than Rights which have become void pursuant to
the provisions of Section 11(a)(ii) hereof) held by each holder of Rights.

         (c) In the event that there shall not be sufficient shares of Common
Stock issued but not outstanding or authorized but unissued to permit any
exchange of Rights as contemplated in accordance with this Section 24, the
Company shall take all such action as may be necessary to authorize additional
shares of Common Stock for issuance upon exchange of the Rights. In the event
the Company shall, after good faith effort, be unable to take all such action
as may be necessary to authorize such additional Common Stock, the Company
shall substitute, for each share of Common Stock that would otherwise be
issuable upon exchange of a Right, a number of Preferred Shares or fraction
thereof such that the current per share market price of one Preferred Share
multiplied by

                                      -50-

<PAGE>   54

such number or fraction is equal to the current per share market price of one
share of Common Stock as of the date of issuance of such Preferred Shares or
fraction thereof.

         (d) The Company shall not be required to issue fractions of a share of
Common Stock or to distribute certificates which evidence fractional shares of
Common Stock. In lieu of such fractional shares of Common Stock, the Company
shall pay to the registered holders of the Right Certificates with regard to
which such shares of fractional Common Stock would otherwise be issuable an
amount in cash equal to the same fraction of the current market value of a
whole share of Common Stock. For the purposes of this Section 24(d), the
current market value of a whole share of Common Stock shall be the closing
price of a share of Common Stock (as determined pursuant to the second sentence
of Section 11(d)(i) hereof) for the Trading Day immediately prior to the date
of exchange pursuant to this Section 24.

         Section 25. Notice of Certain Events. (a) In case the Company shall at
any time after the earlier of the Distribution Date and the Shares Acquisition
Date propose (i) to pay any dividend payable in stock of any class to the
holders of its Preferred Shares or to make any other distribution to the
holders of its Preferred Shares (other than a regular quarterly cash dividend),
(ii) to offer to the holders of its Preferred Shares rights or warrants to
subscribe for or to purchase any additional Preferred Shares or shares of stock
of any class or any other securities, rights or options, (iii) to effect any
reclassification of its Preferred Shares (other than a reclassification
involving only the subdivision or combination of outstanding Preferred Shares),
(iv) to effect any consolidation or merger with or into, or to effect any sale
or other transfer (or to permit one or more of its Subsidiaries to effect any
sale or other transfer), in one or more transactions, of 50% or more of the
assets or earning power of the Company and its Subsidiaries (taken as a whole)
to, any other Person, (v) to effect the liquidation, dissolution or winding up
of the Company, or (vi) to declare or pay any

                                      -51-

<PAGE>   55

dividend on the Common Stock payable in Common Shares or to effect a
subdivision, combination or consolidation of the Common Stock (by
reclassification or otherwise than by payment of dividends in Common Shares),
then, in each such case, the Company shall give to each holder of a Right
Certificate, in accordance with Section 26 hereof, a notice of such proposed
action, which shall specify the record date for the purposes of such stock
dividend, or distribution of rights or warrants, or the date on which such
reclassification. consolidation, merger, sale, transfer, liquidation,
dissolution, or winding up is to take place and the date of participation
therein by the holders of the Common Stock and/or Preferred Stock, if any such
date is to be fixed, and such notice shall be so given in the case of any
action covered by clause (i) or (ii) above at least 10 days prior to the record
date for determining holders of the Preferred Shares for purposes of such
action, and in the case of any such other action, at least 10 days prior to the
date of the taking of such proposed action or the date of participation therein
by the holders of the Common Stock and/or Preferred Stock, whichever shall be
the earlier.

         (b) In case the event set forth in Section 11(a)(ii) or Section 13
hereof shall occur, then the Company shall as soon as practicable thereafter
give to each holder of a Right Certificate (or if occurring prior to the
Distribution Date, the holders of the Common Shares), in accordance with
Section 26 hereof, a notice of the occurrence of such event, which notice shall
describe such event and the consequences of such event to holders of Rights
under Section 11(a)(ii) or Section 13 hereof, as the case may be.

         Section 26. Notices. Notices or demands authorized by this Agreement
to be given or made by the Rights Agent or by the holder of any Right
Certificate to or on the Company shall be sufficiently given or made if sent by
registered or certified mail and deemed given upon receipt, addressed (until
another address is filed in writing with the Rights Agent) as follows:


                                     -52-

<PAGE>   56

                           Aronex Pharmaceuticals, Inc.
                           8707 Technology Forest Place
                           The Woodlands, Texas 77381-1191
                           Attention: Chief Executive Officer

Subject to the provisions of Section 21 hereof, any notice or demand authorized
by this Agreement to be given or made by the Company or by the holder of any
Right Certificate to or on the Rights Agent shall be sent by registered or
certified mail and shall be deemed given upon receipt, and addressed (until
another address is filed in writing with the Company) as follows:

                           American Stock Transfer & Trust Company
                           40 Wall Street
                           New York, New York 10005
                           Attention: Corporate Trust Department

Notices or demands authorized by this Agreement to be given or made by the
Company or the Rights Agent to the holder of any Right Certificate shall be
sufficiently given or made if sent by first-class mail, postage prepaid,
addressed to such holder at the address of such holder as shown on the registry
books of the Company.

         Section 27. Supplements and Amendments. Except as otherwise provided
in this Section 27, for so long as the Rights are then redeemable, the Company
may in its sole and absolute discretion, and the Rights Agent shall if the
Company so directs, supplement or amend any provision of this Agreement in any
respect without the approval of any holders of the Rights, including, without
limitation, as long as the Rights are then redeemable, to extend the period
during which the Rights may be redeemed. At any time when the Rights are no
longer redeemable, except as otherwise provided in this Section 27, the Company
may, and the Rights Agent shall, if the Company so directs, supplement or amend
this Agreement without the approval of any holders of Rights Certificates in
order to (i) cure any ambiguity, (ii) correct or supplement any provision
contained herein which may be defective or inconsistent with any other
provisions herein, (iii) shorten or



                                      -53-

<PAGE>   57

lengthen any time period hereunder, or (iv) change or supplement the provisions
hereunder in any manner which the Company may deem necessary or desirable;
provided that no such supplement or amendment shall adversely affect the
interests of the holders of Rights as such (other than an Acquiring Person or
an Affiliate or Associate of an Acquiring Person), and no such amendment may
cause the rights again to become redeemable or cause the Agreement again to
become amendable other than in accordance with this sentence. Notwithstanding
anything contained in this Agreement to the contrary, no supplement or
amendment shall be made which decreases the Redemption Price. Upon the delivery
of a certificate from an appropriate officer of the Company which states that
the proposed supplement or amendment is in compliance with the terms of this
Section 27, the Rights Agent shall execute such supplement or amendment.
Notwithstanding anything in this Agreement to the contrary, no supplement or
amendment that changes the rights and duties of the Rights Agent under this
Agreement will be effective against the Rights Agent without the execution of
such supplement or amendment by the Rights Agent.

         Section 28. Successors. All the covenants and provisions of this
Agreement by or for the benefit of the Company or the Rights Agent shall bind
and inure to the benefit of their respective successors and assigns hereunder.

         Section 29. Benefits of this Agreement. Nothing in this Agreement
shall be construed to give to any Person other than the Company, the Rights
Agent and the registered holders of the Right Certificates (and, prior to the
Distribution Date, the Common Stock) any legal or equitable right, remedy or
claim under this Agreement; but this Agreement shall be for the sole and
exclusive benefit of the Company, the Rights Agent and the registered holders
of the Right Certificates (and, prior to the Distribution Date, the Common
Stock).


                                     -54-

<PAGE>   58

         Section 30. Determination and Actions by the Board of Directors. The
Board of Directors of the Company shall have the exclusive power and authority
to administer this Agreement and to exercise the rights and powers specifically
granted to the Board of Directors of the Company or to the Company, or as may
be necessary or advisable in the administration of this Agreement, including,
without limitation, the right and power to (i) interpret the provisions of this
Agreement and (ii) make all determinations deemed necessary or advisable for
the administration of this Agreement (including, without limitation, a
determination to redeem or not redeem the Rights or to amend this Agreement).
All such actions, calculations, interpretations and determinations (including,
for purposes of clause (y) below, all omissions with respect to the foregoing)
that are done or made by the Board of Directors of the Company in good faith,
shall (x) be final, conclusive and binding on the Company, the Rights Agent,
the holders of the Rights, as such, and all other parties, and (y) not subject
the Board of Directors to any liability to the holders of the Rights.

         Section 31. Severability. If any term, provision, covenant or
restriction of this Agreement is held by a court of competent jurisdiction or
other authority to be invalid, void or unenforceable, the remainder of the
terms, provisions, covenants and restrictions of this Agreement shall remain in
full force and effect and shall in no way be affected, impaired or invalidated.

         Section 32. Governing Law. This Agreement and each Right Certificate
issued hereunder shall be deemed to be a contract made under the laws of the
State of Delaware and for all purposes shall be governed by and construed in
accordance with the laws of such State applicable to contracts to be made and
performed entirely within such State.

         Section 33. Counterparts. This Agreement may be executed in any number
of counterparts and each of such counterparts shall for all purposes be deemed
to be an original, and all such counterparts shall together constitute but one
and the same instrument.


                                     -55-

<PAGE>   59
         Section 34. Descriptive Headings. Descriptive headings of the several
Sections of this Agreement are inserted for convenience only and shall not
control or affect the meaning or construction of any of the provisions hereof.


                                     -56-

<PAGE>   60

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be duly executed and attested, all as of the day and year first above written.


                                      ARONEX PHARMACEUTICALS, INC.


                                      By: /s/ Geoffrey F. Cox, Ph.D.
                                          -------------------------------------
                                          Geoffrey F. Cox, Ph.D.
                                          Chief Executive Officer

                                      AMERICAN STOCK TRANSFER & TRUST
                                      COMPANY, as Rights Agent


                                      By: /s/ Herbert Lemmer
                                          -------------------------------------
                                          Name: Herbert Lemmer
                                                -------------------------------
                                          Title: General Counsel
                                                 ------------------------------


                                      -57-

<PAGE>   61

                                   EXHIBIT A


                         CERTIFICATE OF DESIGNATION OF

                        SERIES ONE JUNIOR PARTICIPATING

                PREFERRED STOCK OF ARONEX PHARMACEUTICALS, INC.

             PURSUANT TO SECTION 151 OF THE GENERAL CORPORATION LAW
                            OF THE STATE OF DELAWARE

         Aronex Pharmaceuticals, Inc., a corporation organized and existing
under the General Corporation Law of the State of Delaware (hereinafter called
the "Company"), hereby certifies that the following resolution was duly adopted
by the Board of Directors of the Company as required by Section 151 of the
General Corporation Law of the State of Delaware at a meeting duly called and
held on October 6, 1999:

         WHEREAS, the Company's Restated Certificate of Incorporation, as
amended (hereinafter called the "Certificate of Incorporation"), authorizes a
total of 45,000,000 shares of capital stock, consisting of 5,000,000 shares of
preferred stock, par value $0.001 per share (the "Preferred Stock"), issuable
from time to time in one or more series, and 40,000,000 shares of common stock,
par value $0.001 per share (the "Common Stock"), issuable from time to time;
and

         WHEREAS, pursuant to the authority vested in the Board of Directors of
the Company in accordance with the General Corporation Law of the State of
Delaware and the Company's Certificate of Incorporation, the Board of Directors
is authorized by resolution duly adopted, to designate shares of Preferred
Stock to be issued, in one or more series, to provide for the designation
thereof of the powers, designations, preferences and relative, participating,
optional or other special rights of the shares of such series, and the
qualifications, limitations or restrictions thereof;

         NOW, THEREFORE BE IT RESOLVED, that pursuant to the authority granted
to and vested in the Board of Directors of the Company (hereinafter called the
"Board of Directors" or the "Board") in accordance with the provisions of the
Delaware General Corporation Law and the Certificate of Incorporation, a Series
One Junior Participating Preferred Stock of the Corporation is hereby created,
with the designations thereof and the powers, designations, preferences and
relative, participating, optional or other special rights of the shares of such
series, and the qualifications, limitations or restrictions thereof as set
forth below:

         Section 1. Designation and Amount. The shares of such series shall be
designated as "Series One Junior Participating Preferred Stock" (the "Series
One Preferred Stock") and the number of shares constituting the Series One
Preferred Stock shall be 750,000. Such number of shares may be increased or
decreased by resolution of the Board of Directors; provided that no decrease
shall reduce the number of shares of Series One Preferred Stock to a number
less than the number of


<PAGE>   62


shares then outstanding plus the number of shares reserved for issuance upon
the exercise of outstanding options, rights or warrants or upon the conversion
of any outstanding securities issued by the Company convertible into Series One
Preferred Stock.

         Section 2. Dividends and Distributions.

         (A) Subject to the rights of the holders of any shares of any series
of Preferred Stock ranking prior and superior to the Series One Preferred Stock
with respect to dividends, the holders of shares of Series One Preferred Stock,
in preference to the holders of Common Stock of the Company and of any other
stock of the Company ranking junior to the Series One Preferred Stock, shall be
entitled to receive, when, as and if declared by the Board of Directors out of
funds legally available therefor, quarterly dividends payable in cash on the
last day of January, April, July, and October in each year (each such date
being referred to herein as a "Dividend Payment Date"), commencing on the first
Dividend Payment Date after the first issuance of a share or fraction of a
share of Series One Preferred Stock, in an amount per share (rounded to the
nearest cent) equal to the greater of (a) $1.00, or (b) subject to the
provision for adjustment hereinafter set forth, 100 times the aggregate per
share amount of all cash dividends, and 100 times the aggregate per share
amount (payable in kind) of all non-cash dividends or other distributions other
than a dividend payable in shares of Common Stock, declared on the Common Stock
since the immediately preceding Dividend Payment Date or, with respect to the
first Dividend Payment Date, since the first issuance of any share or fraction
of a share of Series One Preferred Stock. In the event that the Company shall
at any time after October 18, 1999, declare or pay any dividend on the Common
Stock payable in shares of Common Stock, or effect a subdivision or combination
or consolidation of the outstanding shares of Common Stock (by reclassification
or otherwise than by payment of a dividend in shares of Common Stock) into a
greater or lesser number of shares of Common Stock, then in each such case the
amount to which holders of shares of Series One Preferred Stock were entitled
immediately prior to such event under clause (b) of the preceding sentence
shall be adjusted by multiplying such amount by a fraction, the numerator of
which is the number of shares of Common Stock outstanding immediately after
such event and the denominator of which is the number of shares of Common Stock
that were outstanding immediately prior to such event.

         (B) The Company shall declare a dividend or distribution on the Series
One Preferred Stock as provided in paragraph (A) of this Section immediately
after it declares a dividend or distribution on the Common Stock (other than a
dividend payable in shares of Common Stock); provided that, in the event no
dividend or distribution shall have been declared on the Common Stock during
the period between any Dividend Payment Date and the next subsequent Dividend
Payment Date, a dividend of $1.00 per share on the Series One Preferred Stock
shall nevertheless be payable, when, as and if declared, on such subsequent
Dividend Payment Date.

         (C) Dividends shall begin to accrue and be cumulative, whether or not
earned or declared, on outstanding shares of Series One Preferred Stock from
the Dividend Payment Date next preceding the date of issue of such shares,
unless the date of issue of such shares is prior to the record date for the
first Dividend Payment Date, in which case dividends on such shares shall begin
to accrue from the date of issue of such shares, or unless the date of issue is
a Dividend Payment Date or is a date


<PAGE>   63

after the record date for the determination of holders of shares of Series One
Preferred Stock entitled to receive a quarterly dividend and before such
Dividend Payment Date, in either of which events such dividends shall begin to
accrue and be cumulative from such Dividend Payment Date. Accrued but unpaid
dividends shall not bear interest. Dividends paid on the shares of Series One
Preferred Stock in an amount less than the total amount of such dividends at
the time accrued and payable on such shares shall be allocated pro rata on a
share-by-share basis among all such shares at the time outstanding. The Board
of Directors may fix a record date for the determination of holders of shares
of Series One Preferred Stock entitled to receive payment of a dividend or
distribution declared thereon, which record date shall be not more than 60 days
prior to the date fixed for the payment thereof.

         Section 3. Voting Rights. The holders of shares of Series One
Preferred Stock shall have the following voting rights:

         (A) Subject to the provision for adjustment hereinafter set forth and
except as otherwise provided in the Certificate of Incorporation or required by
law, each share of Series One Preferred Stock shall entitle the holder thereof
to 100 votes on all matters upon which the holders of the Common Stock of the
Company are entitled to vote. In the event the Company shall at any time after
October 18, 1999 declare or pay any dividend on the Common Stock payable in
shares of Common Stock, or effect a subdivision or combination or consolidation
of the outstanding shares of Common Stock (by reclassification or otherwise
than by payment of a dividend in shares of Common Stock) into a greater or
lesser number of shares of Common Stock, then in each such case the number of
votes per share to which holders of shares of Series One Preferred Stock were
entitled immediately prior to such event shall be adjusted by multiplying such
number by a fraction, the numerator of which is the number of shares of Common
Stock outstanding immediately after such event and the denominator of which is
the number of shares of Common Stock that were outstanding immediately prior to
such event.

         (B) Except as otherwise provided herein, in the Certificate of
Incorporation or in any other Certificate of Designations creating a series of
Preferred Stock or any similar stock, and except as otherwise required by law,
the holders of shares of Series One Preferred Stock and the holders of shares
of Common Stock and any other capital stock of the Company having general
voting rights shall vote together as one class on all matters submitted to a
vote of stockholders of the Company.

         (C) Except as set forth herein, or as otherwise provided by law or the
Certificate of Incorporation, holders of Series One Preferred Stock shall have
no special voting rights and their consent shall not be required (except to the
extent they are entitled to vote with holders of Common Stock as set forth
herein) for taking any corporate action.

         Section 4. Certain Restrictions.

         (A) Whenever quarterly dividends or other dividends or distributions
payable on the Series One Preferred Stock as provided in Section 2 are in
arrears, thereafter and until all accrued


<PAGE>   64

and unpaid dividends and distributions, whether or not earned or declared, on
shares of Series One Preferred Stock outstanding shall have been paid in full,
the Company shall not:

                  (i) declare or pay dividends, or make any other
         distributions, on any shares of stock ranking junior (as to dividends)
         to the Series One Preferred Stock;

                  (ii) declare or pay dividends, or make any other
         distributions, on any shares of stock ranking on a parity (as to
         dividends) with the Series One Preferred Stock, except dividends paid
         ratably on the Series One Preferred Stock and all such parity stock on
         which dividends are payable or in arrears in proportion to the total
         amounts to which the holders of all such shares are then entitled;

                  (iii) redeem or purchase or otherwise acquire for
         consideration shares of any stock ranking junior (either as to
         dividends or upon liquidation, dissolution or winding up) to the
         Series One Preferred Stock, provided that the Company may at any time
         redeem, purchase or otherwise acquire shares of any such junior stock
         in exchange for shares of any stock of the Company ranking junior (as
         to dividends and upon dissolution, liquidation or winding up) to the
         Series One Preferred Stock or rights, warrants or options to acquire
         such junior stock; or

                  (iv) redeem or purchase or otherwise acquire for
         consideration any shares of Series One Preferred Stock, or any shares
         of stock ranking on a parity (either as to dividends or upon
         liquidation, dissolution or winding up) with the Series One Preferred
         Stock, except in accordance with a purchase offer made in writing or
         by publication (as determined by the Board of Directors) to all
         holders of such shares upon such terms as the Board of Directors,
         after consideration of the respective annual dividend rates and other
         relative rights and preferences of the respective series and classes,
         shall determine in good faith will result in fair and equitable
         treatment among the respective series or classes.

         (B) The Company shall not permit any subsidiary of the Company to
purchase or otherwise acquire for consideration any shares of stock of the
Company unless the Company could, under paragraph (A) of this Section 4,
purchase or otherwise acquire such shares at such time and in such manner.

         Section 5. Reacquired Shares. Any shares of Series One Preferred Stock
purchased or otherwise acquired by the Company in any manner whatsoever shall
be retired and canceled promptly after the acquisition thereof. All such shares
shall upon their retirement become authorized but unissued shares of Preferred
Stock and may be reissued as part of a new series of Preferred Stock to be
created by resolution or resolutions of the Board of Directors, subject to any
conditions and restrictions on issuance set forth herein.

         Section 6. Liquidation, Dissolution or Winding Up. Upon any
liquidation, dissolution or winding up of the Company, no distribution shall be
made (A) to the holders of the Common Stock or of shares of any other stock of
the Company ranking junior, upon liquidation, dissolution or


<PAGE>   65

winding up, to the Series One Preferred Stock unless, prior thereto, the
holders of shares of Series One Preferred Stock shall have received $1.00 per
share, plus an amount equal to accrued and unpaid dividend distributions
thereon, whether or not earned or declared, to the date of such payment,
provided that the holders of shares of Series One Preferred Stock shall be
entitled to receive an aggregate amount per share, subject to the provision for
adjustment hereinafter set forth, equal to 100 times the aggregate amount to be
distributed per share to holders of shares of Common Stock, or (B) to the
holders of shares of stock ranking on a parity upon liquidation, dissolution or
winding up with the Series One Preferred Stock, except distributions made
ratably on the Series One Preferred Stock and all such parity stock in
proportion to the total amounts to which the holders of all such shares are
entitled upon such liquidation, dissolution or winding up. In the event,
however, that there are not sufficient assets available to permit payment in
full of the Series One Preferred Stock liquidation preference and the
liquidation preferences of all other classes and series of stock of the
Company, if any, that rank on a parity with the Series One Preferred Stock in
respect thereof, then the assets available for such distribution shall be
distributed ratably to the holders of the Series One Preferred Stock and the
holders of such parity shares in the proportion to their respective liquidation
preferences. In the event the Company shall at any time after October 18, 1999
declare or pay any dividend on the Common Stock payable in shares of Common
Stock, or effect a subdivision or combination or consolidation of the
outstanding shares of Common Stock (by reclassification or otherwise than by
payment of a dividend in shares of Common Stock) into a greater or lesser
number of shares of Common Stock, then in each such case the aggregate amount
to which holders of shares of Series One Preferred Stock were entitled
immediately prior to such event under the proviso in clause (A) of the
preceding sentence shall be adjusted by multiplying such amount by a fraction
the numerator of which is the number of shares of Common Stock outstanding
immediately after such event and the denominator of which is the number of
shares of Common Stock that were outstanding immediately prior to such event.

         Section 7. Consolidation, Merger, etc. In the case the Company shall
enter into any consolidation, merger, combination or other transaction in which
the shares of Common Stock are converted into, exchanged for or changed into
other stock or securities, cash and/or any property, then in any such case each
share of Series One Preferred Stock shall at the same time be similarly
converted into, exchanged for or changed into an amount per share (subject to
the provision for adjustment hereinafter set forth) equal to 100 times the
aggregate amount of stock, securities, cash and/or any other property (payable
in kind), as the case may be, into which or for which each share of Common
Stock is converted, exchanged or converted. In the event the Company shall at
any time after October 18, 1999 declare or pay any dividend on the Common Stock
payable in shares of Common Stock, or effect a subdivision or combination or
consolidation of the outstanding shares of Common Stock (by reclassification or
otherwise than by payment of a dividend in shares of Common Stock) into a
greater or lesser number of shares of Common Stock, then in each such case the
amount set forth in the preceding sentence with respect to the conversion,
exchange or change of shares of Series One Preferred Stock shall be adjusted by
multiplying such amount by a fraction, the numerator of which is the number of
shares of Common Stock outstanding immediately after such event and the
denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.


<PAGE>   66

         Section 8. No Redemption. The shares of Series One Preferred Stock
shall not be redeemable from any holder.

         Section 9. Rank. The Series One Preferred Stock shall rank, with
respect to the payment of dividends and the distribution of assets upon
liquidation, dissolution or winding up of the Company, junior to all other
series of Preferred Stock and senior to the Common Stock.

         Section 10. Amendment. If any proposed amendment to the Certificate of
Incorporation (including this Certificate of Designations) would alter, change
or repeal any of the preferences, powers or special rights given to the Series
One Preferred Stock so as to affect the Series One Preferred Stock adversely,
then the holders of the Series One Preferred Stock shall be entitled to vote
separately as a class upon such amendment, and the affirmative vote of
two-thirds of the outstanding shares of the Series One Preferred Stock, voting
separately as a class, shall be necessary for the adoption thereof, in addition
to such other vote as may be required by the General Corporation Law of the
State of Delaware.

         Section 11. Fractional Shares. Series One Preferred Stock may be
issued in fractions of a share that shall entitle the holder, in proportion to
such holder's fractional shares, to exercise voting rights, receive dividends,
participate in distributions and to have the benefit of all other rights of
holders of Series One Preferred Stock.


<PAGE>   67

         IN WITNESS WHEREOF, this Certificate of Designations has been executed
on behalf of the Company by its Chief Executive Officer and attested by its
Secretary this ___ day of October, 1999.

                                      ARONEX PHARMACEUTICALS, INC.



                                      By:
                                         --------------------------------------
                                         Geoffrey F. Cox, Ph.D.
                                         Chief Executive Officer


Attest:


- ---------------------------
Terance A. Murnane
Secretary


<PAGE>   68
                                   EXHIBIT B

                           Form of Right Certificate
Certificate No. R-                                              _________Rights

         NOT EXERCISABLE AFTER OCTOBER 18, 2009 OR EARLIER IF REDEMPTION OR
         EXCHANGE OCCURS. THE RIGHTS ARE SUBJECT TO REDEMPTION AT $0.001 PER
         RIGHT AND TO EXCHANGE ON THE TERMS SET FORTH IN THE RIGHTS AGREEMENT.

                          Aronex Pharmaceuticals, Inc.

         This certifies that _________, or registered assigns, is the registered
owner of the number of Rights set forth above, each of which entitles the owner
thereof, subject to the terms, provisions and conditions of the Rights
Agreement, dated as of October 6, 1999 (the "Rights Agreement"), between Aronex
Pharmaceuticals, Inc., a Delaware corporation (the "Company"), and American
Stock Transfer & Trust Company, as rights agent (the "Rights Agent"), to
purchase from the Company at any time after the Distribution Date (as such term
is defined in the Rights Agreement) and prior to 5:00 P.M., Houston, Texas time,
on October 18, 2009 at the principal office of the Rights Agent, or at the
office of its successor as Rights Agent, one-hundredth of a fully paid
non-assessable share of Series One Junior Participating Preferred Stock, par
value $0.001 per share, of the Company (the "Preferred Shares") at a purchase
price of $32.00 (subject to adjustment as provided in the Rights Agreement) per
one-hundredth of a Preferred Share (the "Purchase Price"), upon presentation and
surrender of this Right Certificate with the Form of Election to Purchase duly
executed. The number of Rights evidenced by this Right Certificate (and the
number of one-hundredths of a Preferred Share which may be purchased upon
exercise hereof) set forth above, and the Purchase Price set forth above, are
the number and Purchase Price as of October 18, 1999, based on the Preferred
Shares as constituted at such date. As provided in the Rights Agreement, the
Purchase Price and the number of one-hundredths of a Preferred Share which may
be purchased upon the exercise of the Rights evidenced by this Right Certificate
are subject to modification and adjustment upon the happening of certain events.

         This Right Certificate is subject to all of the terms, provisions and
conditions of the Rights Agreement, which terms, provisions and conditions are
hereby incorporated herein by reference and made a part hereof and to which
Rights Agreement reference is hereby made for a full description of the rights,
limitations of rights, obligations, duties and immunities hereunder of the
Rights Agent, the Company and the holders of the Right Certificates. Copies of
the Rights Agreement are on file at the principal executive offices of the
Company and the offices of the Rights Agent.

         This Right Certificate, with or without other Right Certificates, upon
surrender at the principal office of the Rights Agent, may be exchanged for
another Right Certificate or Right Certificates of like tenor and date
evidencing Rights entitling the holder to purchase a like aggregate number of
Preferred Shares as the Rights evidenced by the Right Certificate or Right
Certificates surrendered shall have entitled such holder to purchase. If this
Right Certificate shall be exercised in part, the

                                      B-1

<PAGE>   69

holder shall be entitled to receive upon surrender hereof another Right
Certificate or Right Certificates for the number of whole Rights not exercised.

         Subject to the provisions of the Rights Agreement, the Rights
evidenced by this Right Certificate (i) may be redeemed by the Company at a
redemption price of $0.001 per Right or (ii) may be exchanged in whole or in
part for Preferred Shares or shares of the Company's Common Shares, par value
$0.001 per share.

         No fractional Preferred Shares will be issued upon the exercise of any
Right or Rights evidenced hereby (other than fractions which are integral
multiples of one-hundredth of a Preferred Share, which may, at the election of
the Company, be evidenced by depositary receipts), but, in lieu thereof, a cash
payment will be made, as provided in the Rights Agreement.

         No holder of this Right Certificate shall be entitled to vote or
receive dividends or be deemed for any purpose the holder of the Preferred
Shares or of any other securities of the Company which may at any time be
issuable on the exercise hereof, nor shall anything contained in the Rights
Agreement or herein be construed to confer upon the holder hereof as such, any
of the rights of a stockholder of the Company or any right to vote for the
election of directors or upon any matter submitted to stockholder of the
Company at any meeting thereof, or to give or withhold consent to any corporate
action, or to receive notice of meetings or other actions affecting
stockholders (except as provided in the Rights Agreement), or to receive
dividends or subscription rights, or otherwise, until the Right or Rights
evidenced by this Right Certificate shall have been exercised as provided in
the Rights Agreement.

         This Right Certificate shall not be valid or obligatory for any
purpose until it shall have been countersigned by the Rights Agent.

         WITNESS the facsimile signature of the proper officers of the Company
and its corporate seal. Dated as of ______________,_______.

                                         ARONEX PHARMACEUTICALS, INC.
ATTEST:

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

Countersigned:                           AMERICAN STOCK TRANSFER & TRUST
                                         COMPANY, as Rights Agent


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



                                      B-2

<PAGE>   70

                   FORM OF REVERSE SIDE OF RIGHT CERTIFICATE

                               FORM OF ASSIGNMENT

                (To be executed by the registered holder if such
               holder desires to transfer the Right Certificate.)


         FOR VALUE RECEIVED___________________________ hereby sells, assigns
and transfers onto

- -------------------------------------------------------------------------------
                 (Please print name and address of transferee)

this Right Certificate, together with all right, title and interest therein,
and does hereby irrevocably constitute and appoint___________________ Attorney,
to transfer the within Right Certificate on the books of the within-named
Company, with full power of substitution.

Dated:______________,____

                                    Signature
                                             ----------------------------------

         Signature Guaranteed:

         Signatures must be guaranteed by a member firm of a registered
national securities exchange, a member of the National Association of
Securities Dealers, Inc., or a commercial bank or trust company having an
office or correspondent in the United States.

- -------------------------------------------------------------------------------

         The undersigned hereby certifies that the Rights evidenced by this
Right Certificate are not beneficially owned by an Acquiring Person or an
Affiliate or Associate thereof (as defined in the Rights Agreement).

                                    Signature
                                             ----------------------------------

- -------------------------------------------------------------------------------


                                      B-3

<PAGE>   71

             FORM OF REVERSE SIDE OF RIGHT CERTIFICATE - CONTINUED

                          FORM OF ELECTION TO PURCHASE

                 (To be executed if holder desires to exercise
                 Rights represented by the Right Certificate.)

To:      Aronex Pharmaceuticals, Inc.

         The undersigned hereby irrevocably elects to exercise _____________
Rights represented by this Right Certificate to purchase the Preferred Shares
issuable upon the exercise of such Rights and requests that certificates for
such Preferred Shares be issued in the name of:

Please insert social security
or other identifying number    ------------------------

                               ------------------------

- ----------------------         ------------------------

                        (Please print name and address)

If such number of Rights shall not be all the Rights evidenced by this Right
Certificate, a new Right Certificate for the balance remaining of such Rights
shall be registered in the name of and delivered to:

Please insert social security
or other identifying number    ------------------------

                               ------------------------

- ----------------------         ------------------------

                        (Please print name and address)

Dated:_______________,____

                                         Signature
                                                  -----------------------------

Signature Guaranteed:

         Signatures must be guaranteed by a member firm of a registered
national securities exchange, a member of the National Association of
Securities Dealers, Inc., or a commercial bank or trust company having an
office or correspondent in the United States.


                                      B-4

<PAGE>   72

            (Form of Reverse Side of Right Certificate -- continued)

- -------------------------------------------------------------------------------

         The undersigned hereby certifies that the Rights evidenced by this
Right Certificate are not beneficially owned by an Acquiring Person or an
Affiliate or Associate thereof (as defined in the Rights Agreement).

                                   Signature
                                            -----------------------------------

- -------------------------------------------------------------------------------



                                      B-5

<PAGE>   73

                                     NOTICE

         The signature in the Form of Assignment or Form of Election to
Purchase, as the case may be, must conform to the name as written upon the face
of this Right Certificate in every particular, without alteration or
enlargement or any change whatsoever.

         In the event the certification set forth above in the Form of
Assignment or the Form of Election to Purchase, as the case may be, is not
completed, the Company and the Rights Agent will deem the beneficial owner of
the Rights evidenced by this Right Certificate to be an Acquiring Person or an
Affiliate or Associate thereof (as defined in the Rights Agreement) and such
Assignment or Election to Purchase will not be honored.


                                      B-6
<PAGE>   74
                                    EXHIBIT C


                         SUMMARY OF RIGHTS TO PURCHASE
                                PREFERRED STOCK

         On October 6, 1999, the Board of Directors of Aronex Pharmaceuticals,
Inc. (the "Company") declared a dividend distribution of one preferred stock
purchase right (a "Right") for each outstanding share of common stock, par value
$0.001 per share ("Common Stock"), of the Company. The distribution is payable
on October 18, 1999 (the "Record Date") to the stockholders of record on that
date. Each Right entitles the registered holder thereof to purchase from the
Company one one-hundredth of a share of Series One Junior Participating
Preferred Stock, par value $0.001 per share, of the Company (the "Preferred
Stock") at a price of $32.00 subject to adjustment. The following is a summary
of the Rights; the full description and terms of the Rights are set forth in a
Rights Agreement (the "Rights Agreement") between the Company and American Stock
Transfer & Trust Company, as Rights Agent (the "Rights Agent").

         Copies of the Rights Agreement and the Certificate of Designation are
available free of charge from the Company. This summary description of the
Rights and the Preferred Stock does not purport to be complete and is qualified
in its entirety by reference to all the provisions of the Rights Agreement and
the Certificate of Designation, including the definitions therein of certain
terms, which Rights Agreement and Certificate of Designation are incorporated
herein by reference.

THE RIGHTS AGREEMENT

         Initially, the Rights will attach to all certificates representing
shares of outstanding Company Common Stock, and no separate Rights Certificates
will be distributed. The Rights will separate from the Company Common Stock and
the Distribution Date will occur upon the earlier of (i) 10 days following the
date of public announcement that a person or group of persons has become an
Acquiring Person (as hereinafter defined) or (ii) 10 business days (or such
later date as may be determined by action of the Board of Directors prior to the
time a person becomes an Acquiring Person) following the commencement of, or the
announcement of an intention to make, a tender offer or exchange offer upon
consummation of which the offeror would, if successful, beneficially own 20% or
more of the outstanding Common Stock (the earlier of such dates being called the
"Distribution Date").

         The term "Acquiring Person" means any person who or which, together
with all of its affiliates and associates, shall be the beneficial owner of 20%
or more of the outstanding Common Stock, but shall not include the Company, any
Subsidiary of the Company or any employee benefit plan of the Company.

         The Rights Agreement provides that, until the Distribution Date, the
Rights will be transferred with and only with the Common Stock. Until the
Distribution Date (or earlier redemption or expiration of the Rights), new
Common Stock certificates issued after the Record


<PAGE>   75


Date, upon transfer or new issuance of Common Stock, will contain a notation
incorporating the Rights Agreement by reference. Until the Distribution Date (or
earlier redemption or expiration of the Rights), the surrender for transfer of
any certificates for Common Stock, outstanding as of the Record Date, even
without such notation or a copy of this Summary of Rights being attached
thereto, will also constitute the transfer of the Rights associated with the
Common Stock represented by such certificate. As soon as practicable following
the Distribution Date, separate certificates evidencing the Rights ("Rights
Certificates") will be mailed to holders of record of the Common Stock as of the
close of business on the Distribution Date and such separate Rights Certificates
alone will evidence the Rights.

         The Rights are not exercisable until the Distribution Date. The Rights
will expire on October 18, 2009 (the "Expiration Date").

         The Purchase Price payable, and the number of one one-hundredths of a
share of Preferred Stock or other securities or property issuable, upon exercise
of the Rights are subject to adjustment from time to time to prevent dilution
(i) in the event of a stock dividend on, or a subdivision, combination or
reclassification of, the Preferred Stock, (ii) upon the grant to holders of the
Preferred Stock of certain rights or warrants to subscribe for or purchase
shares of Preferred Stock at a price, or securities convertible into Preferred
Stock with a conversion price, less than the then current market price of the
Preferred Stock or (iii) upon the distribution to holders of the Preferred Stock
of evidences of indebtedness or assets (excluding regular periodic cash
dividends paid or dividends payable in Preferred Stock) or of subscription
rights or warrants (other than those referred to in (ii) above).

         The number of outstanding Rights and the number of one one-hundredths
of a share of Preferred Stock issuable upon exercise of each Right are also
subject to adjustment in the event of a stock split of the Common Stock or a
stock dividend on the Common Stock payable in the Common Stock or subdivisions,
consolidations or combinations of the Common Stock occurring, in any such case,
prior to the Distribution Date.

         In the event that following a Shares Acquisition Date (the date of
public announcement that an Acquiring Person has become such) the Company is
acquired in a merger or other business combination transaction, or more than 50%
of its consolidated assets or earning power are sold, proper provision will be
made so that each holder of a Right will thereafter have the right to receive,
upon the exercise thereof at the then current exercise price of the Right, that
number of shares of common stock of the acquiring company which at the time of
such transaction will have a market value of two times the exercise price of the
Right (the "Flip-Over Right").

         In the event that a person becomes an Acquiring Person, proper
provision shall be made so that each holder of a Right (other than the Acquiring
Person and its affiliates and associates) will thereafter have the right to
receive upon exercise that number of shares of Common Stock (or, under certain
circumstances, cash, other equity securities or property of the Company) having
a market value equal to two times the Purchase Price of the Rights (the "Flip-In
Right"). Upon the occurrence


<PAGE>   76


of the foregoing event giving rise to the exercisability of the Rights, any
Rights that are or were at any time owned by an Acquiring Person shall become
void.

         With certain exceptions, no adjustment in the Purchase Price will be
required until cumulative adjustments require an adjustment of at least 1% in
such Purchase Price. Upon exercise of the Rights, no fractional shares of
Preferred Stock will be issued other than fractions which are integral multiples
of one one-hundredth of a share of Preferred Stock; cash will be paid in lieu of
fractional shares of Preferred Stock that are not integral multiples of one
one-hundredth of a share of Preferred Stock.

         At any time prior to the earlier to occur of (i) 5:00 p.m., Houston,
Texas time on the 10th day after the Shares Acquisition Date or (ii) the
expiration of the Rights, the Company may redeem the Rights in whole, but not in
part, at a price of $0.001 per Right (the "Redemption Price"); provided, that
(i) if the Board of Directors authorizes redemption on or after the time a
person becomes an Acquiring Person, then such authorization must be by Board
Approval (as hereinafter defined) and (ii) the period for redemption may, upon
Board Approval, be extended by amending the Rights Agreement. The term "Board
Approval" means the approval of a majority of the directors of the Company.
Immediately upon any redemption of the Rights described in this paragraph, the
right to exercise the Rights will terminate and the only right of the holders of
Rights will be to receive the Redemption Price.

         For so long as the Rights are redeemable, the terms of the Rights may
be amended by the Board of Directors without the consent of the holders of the
Rights provided that no amendment to the Rights may be made which decreases the
Redemption Price. At such time as the Rights are no longer redeemable, the
Rights Agreement and the terms of the Rights may be amended without the approval
of any holders of the Rights to (i) cure any ambiguity, (ii) correct or
supplement any defective or inconsistent provision, (iii) shorten or lengthen
any time period under the Rights Agreement, or (iv) change or supplement any
provision contained in the Rights Agreement which the Board of Directors deems
necessary; provided, that no such supplement or amendment may adversely affect
the interests of the holders of the Rights (other than an Acquiring Person and
its affiliates) and no such amendment shall cause the Rights to again become
redeemable or cause the Rights Agreement to again become amendable except as
provided therein.

         Until a Right is exercised, the holder thereof, as such, will have no
rights as a stockholder of the Company, including, without limitation, the right
to vote or to receive dividends. While the distribution of the Rights will not
be taxable to stockholders or to the Company, stockholders may, depending upon
the circumstances, recognize taxable income in the event that the Rights become
exercisable for Preferred Stock (or other consideration).

DESCRIPTION OF PREFERRED STOCK

         Each one-hundredth of a share of the Preferred Stock ("Preferred Share
Fraction") that may be acquired upon exercise of the Rights will be
nonredeemable and subordinate to any other shares of preferred stock that may be
issued by the Company.


<PAGE>   77


         Each Preferred Share Fraction will have a minimum preferential
quarterly dividend rate of $0.01 per Preferred Share Fraction but will, in any
event, be entitled to a dividend equal to the per share dividend declared on the
Company Common Stock.

         In the event of liquidation, the holder of a Preferred Share Fraction
will receive a preferred liquidation payment equal to the greater of $0.01 per
Preferred Share Fraction or the per share amount paid in respect of a share of
Company Common Stock.

         Each Preferred Share Fraction will have one vote, voting together with
the Company Common Stock.

         In the event of any merger, consolidation or other transaction in which
shares of Company Common Stock are exchanged, each Preferred Share Fraction will
be entitled to receive the per share amount paid in respect of each share of
Company Common Stock.

         The rights of holders of the Preferred Stock to dividends, liquidation
and voting, and in the event of mergers and consolidations, are protected by
customary antidilution provisions.

         Because of the nature of the Preferred Stock's dividend, liquidation
and voting rights, the economic value of one Preferred Share Fraction that may
be acquired upon the exercise of each Right should approximate the economic
value of one share of the Company's Common Stock.



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