CELTRIX PHARMACEUTICALS INC
S-3, 1999-07-20
PHARMACEUTICAL PREPARATIONS
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<PAGE>   1

     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JULY 20, 1999
                                                   REGISTRATION NO. 333-_______
================================================================================


                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   ----------

                                    FORM S-3
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                   ----------

                          CELTRIX PHARMACEUTICALS, INC.
             (Exact Name of Registrant as Specified in Its Charter)

                                   ----------

           DELAWARE                                            94-3121462
(State or Other Jurisdiction of                             (I.R.S. Employer
Incorporation or Organization)                            Identification Number)


                          2033 GATEWAY PLACE, SUITE 600
                               SAN JOSE, CA 95110
                                 (408) 988-2500
       (Address, Including Zip Code, and Telephone Number, Including Area
               Code, of Registrant's Principal Executive Offices)

                                   ----------

                              ANDREAS SOMMER, PH.D.
                      PRESIDENT AND CHIEF EXECUTIVE OFFICER
                          2033 GATEWAY PLACE, SUITE 600
                               SAN JOSE, CA 95110
                                 (408) 988-2500
  (Name, Address Including Zip Code, and Telephone Number Including Area Code,
                             of Agent for Service)

                                   ----------

                                   COPIES TO:
                              Edmund S. Ruffin, Jr.
                                Frances Johnston
                                VENTURE LAW GROUP
                           A Professional Corporation
                               2800 Sand Hill Road
                              Menlo Park, CA 94025

                                   ----------

                  APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED
              SALE TO THE PUBLIC: AS SOON AS PRACTICABLE AFTER THE
                 EFFECTIVE DATE OF THIS REGISTRATION STATEMENT.

                                   ----------

     If the only securities being registered on this form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box. [ ]

     If any of the securities being registered on this form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, check the following box. [X]

     If this form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering. [ ] _______________

     If this form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [ ]____________


     If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. [ ]


<TABLE>
<CAPTION>
                                                         CALCULATION OF REGISTRATION FEE
==============================================================================================================================
     TITLE OF EACH CLASS OF        AMOUNT TO BE     PROPOSED MAXIMUM OFFERING   PROPOSED MAXIMUM AGGREGATE        AMOUNT OF
   SECURITIES TO BE REGISTERED      REGISTERED         PRICE PER UNIT (1)           OFFERING PRICE (1)        REGISTRATION FEE
<S>                                <C>                      <C>                        <C>                       <C>
- ------------------------------------------------------------------------------------------------------------------------------
Common Stock, par value $0.01       10,075,000              $1.46875                   $14,797,656.25             $4,114.00
==============================================================================================================================
</TABLE>


(1) Estimated solely for the purpose of computing the amount of the registration
fee based on the average of the high and low price of the Common Stock
as reported on the Nasdaq National Market on July 13, 1999 pursuant to Rule
457(c).


         THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE
OR DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT
SHALL FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF
THE SECURITIES ACT OF 1933 OR UNTIL THIS REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.
<PAGE>   2

                   Subject to Completion, Dated July 20, 1999


PROSPECTUS


                          CELTRIX PHARMACEUTICALS, INC.

                        10,075,000 SHARES OF COMMON STOCK


         THE COMMON STOCK OFFERED BY THIS PROSPECTUS INVOLVE A HIGH DEGREE OF
RISK. YOU SHOULD CAREFULLY CONSIDER THE "RISK FACTORS" BEGINNING ON PAGE 2 IN
DETERMINING WHETHER TO PURCHASE THE COMMON STOCK.



         The selling stockholders identified on pages 12 and 13 of this
prospectus are offering these shares of common stock. For additional information
on the methods of sale, you should refer to the section entitled "Plan of
Distribution" on page 10. We will not receive any portion of the proceeds from
the sale of these shares.

         Celtrix's common stock is quoted on the Nasdaq National Market under
the symbol "CTRX."

         On July 13, 1999, the last sale price of the common stock on the Nasdaq
National Market was $1.625 per share.

<TABLE>
<CAPTION>
==================================================================================================================
                                                                       UNDERWRITING
                                               PRICE TO                DISCOUNTS AND              PROCEEDS TO
                                                PUBLIC                  COMMISSIONS           SELLING STOCKHOLDERS
- ------------------------------------------------------------------------------------------------------------------
<S>                                         <C>                       <C>                     <C>
Per Share..........................         See Text Above            See Text Above             See Text Above
Total..............................
- ------------------------------------------------------------------------------------------------------------------
</TABLE>

         NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THE SECURITIES OR PASSED ON THE
ADEQUACY OR ACCURACY OF THE DISCLOSURES IN THIS PROSPECTUS. ANY REPRESENTATION
TO THE CONTRARY IS A CRIMINAL OFFENSE.

         THE INFORMATION IN THE PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED.
WE MAY NOT SELL THESE SECURITIES UNTIL THE REGISTRATION STATEMENT FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE. THIS PROSPECTUS IS NOT AN OFFER
TO SELL THESE SECURITIES AND IT IS NOT SOLICITING AN OFFER TO BUY THESE
SECURITIES IN ANY STATE WHERE THE OFFER OR SALE IS NOT PERMITTED.



                The date of this prospectus is ____________, 1999

<PAGE>   3
                                TABLE OF CONTENTS

<TABLE>
<S>                                                                        <C>
THE COMPANY.................................................................1
RISK FACTORS................................................................2
USE OF PROCEEDS............................................................10
ISSUANCE OF COMMON STOCK AND WARRANTS TO SELLING STOCKHOLDERS..............10
PLAN OF DISTRIBUTION.......................................................10
SELLING STOCKHOLDERS.......................................................12
LEGAL MATTERS..............................................................14
EXPERTS....................................................................14
WHERE YOU CAN FIND MORE INFORMATION........................................14
</TABLE>


<PAGE>   4
    We have not authorized any dealer, salesperson or other person to give any
information or represent anything not contained in this prospectus. You should
not rely on any unauthorized information. This prospectus does not offer to sell
or buy any shares in any jurisdiction in which it is unlawful. The information
in this prospectus is current as of the date on the cover.

                                   THE COMPANY

     Celtrix is a biopharmaceutical company developing novel drug candidates to
treat seriously debilitating, degenerative conditions primarily associated with
aging, chronic diseases and severe trauma. Our focus is on restoring lost
tissues and bodily processes essential for the patient's health and quality of
life. Our product development programs have targeted severe osteoporosis,
including hip fracture surgery in the elderly, diabetes, and acute traumatic
injury as in severe burns. Other potential development programs may target
protein wasting diseases (involving deterioration or degeneration of body
tissue) associated with cancer, AIDS, advanced kidney failure, and comparable
life-threatening conditions.

     Our leading drug candidate is SomatoKine, a naturally occurring complex
comprised of the tissue-producing (or anabolic) hormone insulin-like growth
factor-I (IGF-I) and its primary binding protein, BP3. IGF-I is known to play a
major role in diverse biological processes, including bone and muscle formation,
tissue repair, and endocrine regulation. However, IGF-I does not naturally exist
in large quantities free of its binding proteins, and limitations associated
with administering free IGF-I therapeutically have proven significant. When
IGF-I is bound to BP3, as it is in nature, it does not display these acute
limitations. BP-3 is critical in regulating the availability of IGF-I to the
body's cells.

     We completed a Phase II clinical feasibility study in December 1998 using
SomatoKine to treat severely osteoporotic patients recovering from hip fracture
surgery. Final results from the Phase II study suggest that SomatoKine has the
potential to amplify bone metabolism and reverse the loss of bone mineral
density that usually occurs following a hip fracture and improves the patient's
functional independence. In April 1999, we established a corporate partnership
with Elan Corporation, plc and Elan International Services, Ltd. to form a new
jointly owned subsidiary that will continue global development of SomatoKine for
treatment of severe osteoporosis, including recovery from hip fracture surgery.

     We have also conducted a Phase II feasibility study in patients with severe
burns. Data from the study show that SomatoKine has a normalizing effect on
protein metabolism and patients treated with SomatoKine recorded improvements in
several measures of their immune systems and heart functions. We believe that
SomatoKine has the potential to provide severely burned patients with critical
protection from serious infection, and it may speed their recovery and reduce
their hospital stay. Recently we were notified by the United States Food and
Drug Administration (also known as the FDA) that SomatoKine qualifies for orphan
drug status in treatment of severe burns and the beneficial marketing rights
that are associated with that designation. Specifically, orphan drug status will
guarantee us seven years of market exclusivity in the United States following
FDA approval of SomtoKine for the treatment of severe burns, since orphan drug
status applies to products that address diseases or conditions, such as severe
burns, that affect less than 200,000 persons in the United States and for which
development would otherwise not be economically feasible.

     In January 1999, we completed a Phase II study in patients with Type I
diabetes. Final data revealed that average daily insulin requirements for
patients who received SomatoKine decreased significantly and these patients'
average daily glucose levels were also decreased. Based on such findings, we
believe that SomatoKine has potential to improve insulin sensitivity and help
diabetics manage their disease, and in so doing avoid complications which
ultimately accompany diabetes.

     We plan to seek corporate collaborations to develop SomatoKine not only for
treatment of severe burns and diabetes, but also in connection with protein
wasting diseases, such as cancer, AIDS, advanced kidney failure, and similar
life-threatening conditions. SomatoKine's tissue-producing effects offer the
potential to preserve and restore muscle strength and mobility important for
these patients' survival and quality of life.

<PAGE>   5
     We also have a product development, license and marketing agreement with
Genzyme Corporation for TGF-beta-2. Genzyme is currently developing TGF-beta-2
for tissue repair and the treatment of systemic indications. We are not
currently pursuing an in-house TGF-beta-2 program.

    Celtrix was spun off from Collagen Corporation and was incorporated in
Delaware in December 1990 as "Celtrix Laboratories, Inc." We changed our name to
"Celtrix Pharmaceuticals, Inc." in December 1991.

    Our principal executive offices are located at 2033 Gateway Place, Suite
600, San Jose 95110 and our telephone number is (408) 988-2500. As used in this
prospectus, "we," "us," "our" and "Celtrix" refer to Celtrix Pharmaceuticals,
Inc., a Delaware corporation.

                                  RISK FACTORS

    PROSPECTIVE PURCHASERS OF THE COMMON STOCK OFFERED BY THIS PROSPECTUS SHOULD
CAREFULLY CONSIDER THE FOLLOWING RISK FACTORS IN ADDITION TO THE OTHER
INFORMATION APPEARING IN OR INCORPORATED BY REFERENCE INTO THIS PROSPECTUS.

         BECAUSE OUR PRODUCTS ARE IN AN EARLY STAGE OF DEVELOPMENT, NONE HAVE
RECEIVED REGULATORY APPROVAL OR BEEN RELEASED FOR COMMERCIAL SALE

         Our potential products are in the research and development stage and we
have generated no material revenues to date from product sales. To achieve
profitable operations, we must, either, alone or with others, successfully
develop, obtain regulatory approval for, manufacture and market our products
currently in development. Much clinical development work for our potential
products remains to be completed. No assurance can be given that our product
development efforts will be successfully completed, that required regulatory
approvals will be obtained or that any products, if developed and introduced,
will be successfully marketed or achieve market acceptance.

         WE HAVE A HISTORY OF OPERATING LOSSES AND AN ACCUMULATED DEFICIT

         We have incurred net operating losses in every year of operation since
our inception. As of March 31, 1999, we had an accumulated deficit of
approximately $130.4 million. Losses have resulted principally from costs
incurred in connection with our research and development activities and from
general and administrative costs associated with our operations. We expect to
incur substantial and increasing operating losses for at least the next several
years. Our ability to achieve profitability will depend in part on our
completing research and development of, and obtaining regulatory approvals for,
our products and successfully commencing product commercialization.

         OUR STOCK PRICE HAS BEEN VOLATILE AND WE HAVE NEVER PAID DIVIDENDS

         Since our common stock became listed for public trading, its market
price has fluctuated over a wide range and we expect that it will continue to
fluctuate. Like securities of biopharmaceutical and biotechnology companies
generally, our stock price has from time to time experienced significant price
and volume fluctuations that are unrelated to our operating performance. In
addition, announcements concerning Celtrix or our competitors, the results of
clinical trials, technological innovations or new commercial products,
government regulations, developments concerning proprietary rights, litigation
or public concern as to safety of our potential products as well as changes in
general market conditions may have a significant effect on the market price of
our common stock.



                                      -2-
<PAGE>   6
         We have never paid dividends on our capital stock and we do not
anticipate paying any cash dividends in the foreseeable future.

         ALTHOUGH WE REQUIRE FUTURE CAPITAL FOR OPERATIONS, ADDITIONAL FUNDING
IS UNCERTAIN

         We anticipate that proceeds from financings we completed in November
1998 and April 1999, as well as proceeds from the sale of fixed assets in
connection with our discontinuation of manufacturing operations in the fall of
1998 and a $600,000 payment received in March 1999 from Yoshitomi
Pharmaceuticals Industries, Ltd. pursuant to a settlement agreement will be
sufficient to fund our operations (other than clinical research and development)
into the third calendar quarter of 2000. However, further development of our
products will require the commitment of substantial resources to conduct the
time-consuming research and development, clinical studies and regulatory
activities necessary to bring any potential therapeutic products to market and
to establish production, marketing and sales capabilities. Such additional
funding will need to be raised through collaborative arrangements or through
public or private financings, including equity financings. Our joint venture
transaction with Elan Corporation plc in April 1999 provides for the future
purchase by Elan of additional Celtrix stock and we will use the proceeds from
such stock sales to fund our share of anticipated clinical expenses associated
with the joint venture's large scale trial in osteoporosis (hip fractures).

         There can be no assurance that any future financing will be available
to us or on attractive terms, or that we can enter into future collaborative
relationships with corporate partners for the continuation of clinical trials in
any of our current areas of development. In February 1999, the Securities and
Exchange Commission informed us that we did not have a valid exemption for the
sale of our securities in the November 1998 financing and, consequently, we have
offered the purchasers from that financing an opportunity to rescind their
purchase of those securities. The exercise by any of the investors of such
rescission right will reduce our available cash and cash equivalents, and could
have a material adverse effect on our ability to conduct our business in the
future. To date, all purchasers from the financing have informed us they do not
intend to rescind their purchases and they have agreed to waive certain rights
(including certain financial penalties) in connection with the timing of our
obligation to register the securities they purchased in the November 1998
financing with the Securities and Exchange Commission, and, accordingly, our
published financial statements do not reflect the impact of such a rescission.

         OUR POTENTIAL PRODUCTS ARE SUBJECT TO STRINGENT GOVERNMENT REGULATION
IN ORDER TO OBTAIN REQUIRED APPROVALS

         The preclinical testing and clinical trials of any compounds we or our
collaborative partners develop and the manufacturing and marketing of any drugs
produced from such compounds are subject to regulation by numerous federal,
state and local governmental authorities in the United States, the principal one
being the FDA, and by similar agencies in other countries in which drugs
developed by Celtrix or our collaborative partners may be tested and marketed.
Any compound developed by Celtrix or our collaborative partners must receive
approval from applicable regulatory agencies before it may be marketed as a drug
in a particular country. The regulatory process, which includes preclinical
testing and clinical trials of each compound in order to establish its safety
and efficacy, can take many years and requires the expenditure of substantial
resources. Data obtained from preclinical and clinical activities are subject to
varying interpretations which could delay, limit or prevent regulatory agency
approval. In addition, delays or rejections may be encountered based on changes
in regulatory agency policies during the period in which a drug is being
developed and/or the period required for review of any application for
regulatory agency approval of a particular compound. Delays in obtaining
regulatory agency approvals could adversely affect the marketing of any drugs we
or our collaborative partners develop. Such delays could result in the
imposition of costly procedures on our and on our collaborative partners'
activities, diminish any competitive advantages that we or our collaborative
partners may attain and adversely affect our ability to



                                      -3-
<PAGE>   7
receive royalties, any of which could have a material adverse effect on our
business, financial condition and results of operations.

         There can be no assurance that, even after considerable time and funds
have been expended, regulatory agency approvals will be obtained for any
compounds we develop alone or in collaboration with partners. Moreover, if
regulatory agency approval for a drug is granted, such approval may include
limitations on the indicated uses for which the drug may be marketed and this
could limit the potential market for any such drug. Furthermore, if and when we
obtain approval for any of our products, the marketing and manufacture of such
products remains subject to extensive regulatory requirements. The discovery of
previously unknown problems with a drug or its manufacturer may result in
restrictions on such drug or the drug's manufacturer, including withdrawal of
the drug from the market. Failure to comply with regulatory requirements could,
among other things, result in fines, suspension of regulatory approvals,
operating restrictions and criminal prosecution. In addition, regulatory agency
approval of pricing is required in many countries and may be required for the
marketing in such countries of any drug we or our collaborative partners
develop.

         WE FACE UNCERTAINTIES RELATED TO CLINICAL TRIALS

         Before obtaining regulatory approvals for the commercial sale of any of
our products under development, we must demonstrate through preclinical studies
and clinical trials that the product is safe and efficacious for use in each
target indication. The results from preclinical studies and early clinical
trials may not accurately predict results that will be obtained in large-scale
testing, and there can be no assurance that our clinical trials will demonstrate
the safety and efficacy of any products or will result in marketable products. A
number of companies in the biotechnology industry have suffered significant
setbacks in advanced clinical trials, even after experiencing promising results
in earlier trials. For example, in fiscal year 1995, we discontinued our
in-house TGF-beta-2 program for the treatment of ophthalmic conditions as a
result of disappointing clinical study results.

         The rate of completion of our clinical trials is dependent on, among
other factors, the rate of patient enrollment. Patient enrollment is a function
of many factors, including the size of the patient population, the nature of the
protocol, the proximity of patients to clinical sites and the eligibility
criteria for the study. Delays in patient enrollment may result in increased
costs and delays for the trial, which could have a material adverse effect on
our business, financial condition and results of operations.

         THERE IS NO ASSURANCE OF MARKET ACCEPTANCE FOR OUR POTENTIAL PRODUCTS

         There can be no assurance that any products which we successfully
develop, if approved for marketing, will achieve market acceptance. The products
and therapies which we are attempting to develop will compete with a number of
well-established traditional drugs and therapies manufactured and marketed by
major pharmaceutical companies. The degree of market acceptance of any products
we develop will depend on a number of factors, including the establishment and
demonstration in the medical community of the clinical efficacy and safety of
our product candidates, their potential advantage over existing treatment
methods, and reimbursement policies of government and third-party payors,
including insurance companies. Our competitors may also develop new technologies
or products which are more effective or less costly, or that are perceived to be
more cost-effective than SomatoKine. There is no assurance that physicians,
patients or the medical community in general will accept and utilize any
products that we may develop. Our business, financial condition and results of
operations may be materially adversely affected if SomatoKine does not receive
market acceptance for any reason.



                                      -4-
<PAGE>   8
         WE FACE SUBSTANTIAL COMPETITION

         In each of our potential product areas, competition from large
pharmaceutical companies, biotechnology companies and other companies,
universities and research institutions is substantial. At least three large
biotechnology and pharmaceutical companies with substantial financial and legal
resources have patent applications on file in the United States and abroad
directed at the production of recombinant IGF-I by various methods and its use
in various clinical indications. Relative to Celtrix, most of these entities
have substantially greater capital resources, research and development staffs,
facilities and experience in conducting clinical trials and obtaining regulatory
approvals, as well as in manufacturing and marketing pharmaceutical products.
Furthermore, we believe that our competitors have used, and may continue to use,
litigation to gain a competitive advantage. In addition, these and other
entities may have or may develop new technologies or use existing technologies
that are, or may in the future be, the basis for competitive products.

         Any potential products that we successfully develop and for which we
gain regulatory approval will have to compete for market acceptance and market
share. For certain of our potential products, an important factor in such
competition may be the timing of market introduction of competitive products.
Accordingly, the relative speed with which we can develop products, complete the
clinical testing and regulatory approval processes and supply commercial
quantities of the product to the market are expected to be important competitive
factors. We expect that competition will be based, among other things, on
product efficacy, safety, reliability, availability, timing and scope of
regulatory approval and price. There can be no assurance that our competitors
will not succeed in developing technologies and products that are more effective
than any that we are developing or that would render our technology and products
obsolete or noncompetitive. In addition, many of our competitors may achieve
product commercialization or patent protection earlier than we will. Our failure
to compete effectively would have a material adverse effect on our business,
financial condition and results of operations.

         ALTHOUGH OUR SUCCESS DEPENDS ON PROTECTION OF OUR PROPRIETARY
TECHNOLOGY, THERE ARE UNCERTAINTIES INVOLVED WITH PATENT PROSECUTION

         Our success will depend in part on our ability to obtain patents,
maintain trade secrets and operate without infringing on the proprietary rights
of others, both in the United States and in other countries. The patent
positions of pharmaceutical, biopharmaceutical and biotechnology companies,
including Celtrix, are highly uncertain and involve complex legal and factual
questions. Patent law relating to the scope of claims in the technology fields
in which we operate is still evolving. The degree of future protection for our
proprietary rights is therefore uncertain. No consistent policy has emerged
regarding the permissible breadth of coverage of claims in biotechnology
patents. Therefore, no assurance can be given that any of our or our licensors'
patent applications will issue as patents or that any such issued patents will
provide competitive advantages for our products or will not be successfully
challenged or circumvented by our competitors. In addition, there can be no
assurance that others will not independently develop substantially equivalent
proprietary technology that is not covered by our patents or that others will
not be issued patents that may prevent the sale of our proposed products or
require us to license technology from third parties and pay significant fees or
royalties.

         We are aware that at least three large biotechnology and pharmaceutical
companies have issued patents and/or have filed patent applications in the
United States and abroad directed at the production of recombinant IGF-I by
various methods and its use in various clinical indications. The earliest date
of filing of these patent applications is April 25, 1983, but most are much more
recent -- within the last five years. Unless and until all such applications
issue, it is not possible for us to determine the breadth of our competitors'
claims regarding processes for production of IGF-I or for the



                                      -5-
<PAGE>   9
use of IGF-I for particular indications. Furthermore, a large biotechnology and
pharmaceutical company with substantial financial and legal resources has a
patent issued in the United States directed towards certain DNA molecules
encoding BP3 and the corresponding BP3 protein. This same patent was previously
granted in Europe, which we successfully opposed. However, this large
biotechnology and pharmaceutical company has recently appealed the decision in
Europe and there can be no assurance that the appeal will not be successful, nor
is it possible to determine what, if any, claims will be reinstated or the
breadth of such claims. In addition, we expect our competitors to defend
their patent positions vigorously.

         We have developed a new process for the production of IGF and BP3 which
we do not believe infringes other patents relating to recombinant protein
production in general or other patents relating to the production of IGF and BP3
in particular, although there can be no assurance that a contrary position will
not be asserted by our competitors. A large number of other companies have
pending patent applications and/or issued patents which claim certain methods of
use of IGF. There can be no assurance that third parties will not claim that our
technology, current or future products or manufacturing processes infringe their
proprietary rights. If other companies were to successfully bring legal actions
against us claiming patent or other intellectual property infringements, in
addition to any potential liability for damages, we could be required to obtain
a license in order to continue to use the affected process or to manufacture or
use the affected products, or alternatively, we could be required to cease using
such products or process if enjoined by a court. Any such claim, with or without
merit, could result in costly litigation or might require us to enter into
royalty or licensing agreements, all of which could delay or otherwise adversely
impact the development of our potential products for commercial use. If any
licenses are required, there can be no assurance that we will be able to obtain
them on commercially favorable terms, if at all, and if such licenses are not
obtained, we might be prevented from pursuing the development of certain of our
potential products. Our breach of an existing license, our failure to obtain, or
our delay in obtaining a license to any technology that we require to
commercialize our products may have a material adverse impact on our business,
financial condition and results of operations.

         It may be necessary for us to undertake costly litigation to enforce
any patents issued or licensed to us or to determine the scope and validity of
another party's proprietary rights. There can be no assurance that our issued or
licensed patents would be held to be valid by a court of competent jurisdiction.
An adverse outcome in litigation or an interference or other proceeding in a
court or patent office could subject us to significant liabilities to other
parties, require disputed rights to be licensed from other parties or require us
to cease using such technology, any of which could have a material adverse
effect on our business, financial condition and results of operations.

         We also rely on trade secrets to protect technology, especially where
patent protection is not believed to be appropriate or obtainable. We attempt to
protect our proprietary technology and processes in part by confidentiality
agreements with employees, consultants and contractors. There can be no
assurance that such agreements will not be breached, that we will have adequate
remedies for any breach, or that our trade secrets will not otherwise become
known or will be independently discovered by competitors in such a manner that
we have no practical recourse. To the extent that we or our consultants or our
research collaborators use intellectual property owned by others in work
performed for Celtrix, disputes may also arise as to the rights in related or
resulting know-how and inventions.

         WE HAVE LIMITED MANUFACTURING EXPERIENCE AND CAPACITY

         Our products must be manufactured in compliance with regulatory
requirements and at



                                      -6-
<PAGE>   10
acceptable costs. In September 1998, we implemented a restructuring plan to
focus our operations on clinical development of SomatoKine, our leading drug
compound, and to reduce our cash burn rate. With what we believe to be
sufficient clinical grade SomatoKine to support the conduct of clinical trials
for approximately two years, we discontinued our in-house manufacturing
operations. In the future, we will need to contract with others for our
manufacturing operations or establish corporate partnering arrangements that
will support manufacturing of drug material to support additional clinical drug
needs and eventual commercial manufacturing. There can be no assurance that we
will be able to successfully identify and contract with a third party
manufacturer to manufacture our current or future products on a commercial
scale, nor that such products can be manufactured at a cost or in quantities to
make commercially viable products. Failure to obtain sufficient commercial
quantities of SomatoKine at acceptable terms will have an adverse impact on our
attempts to seek approval for this product, or to commercialize it.

         WE HAVE LIMITED SALES AND MARKETING EXPERIENCE

         If we are permitted to commence commercial sales of products, we will
face competition with respect to commercial sales, marketing and distribution,
areas in which we have no experience. To market any of our products directly, we
must develop a marketing and sales force with technical expertise and with
supporting distribution capability. Alternatively, we may obtain the assistance
of a pharmaceutical company with a large distribution system and a large direct
sales force. There can be no assurance that we will be able to establish sales
and distribution capabilities or be successful in gaining market acceptance for
our proprietary products. To the extent we enter into co-promotion or other
licensing arrangements, any revenues we receive will be dependent on the efforts
of third parties and there can be no assurance that such efforts will be
successful.

         WE RELY ON QUALIFIED AND KEY PERSONNEL

         We are highly dependent on the principal members of our scientific and
management staff, the loss of whose services might significantly delay or
prevent the achievement of research, development, or business objectives.
Although we believe we have retained sufficient employees to achieve our
near-term business objectives after reduction of our work force in September
1998, there can be no assurance that the loss of certain employees would not
impede our objectives. Furthermore, there can be no assurance that the reduction
in force will not adversely affect our ability to retain our remaining
employees. The loss of key management or scientific personnel could adversely
affect our continued business.

         Our potential expansion into areas and activities requiring additional
expertise, such as further clinical trials, governmental approvals, contract
manufacturing and marketing, are expected to place additional requirements on
our management, operational and financial resources. These demands are expected
to require an increase in management and scientific personnel and the
development of additional expertise by existing management personnel. The
failure to attract and retain such personnel or to develop such expertise could
materially adversely affect prospects for our success.

         WE ARE SUBJECT TO PRODUCT LIABILITY CLAIMS AND THE AVAILABILITY OF
INSURANCE

         The use of our potential products or technology in clinical trials and
the sale of such products may expose us to liability claims. Such risks exist
even with respect to those potential products, if any, that receive regulatory
approval for commercial sale. Although we have taken and will continue to take
what we believe are appropriate precautions, there can be no assurance that we
will avoid significant product liability exposure. We currently have in force
general liability insurance, with coverage limits of $3.0 million per incident
and $4.0 million in the aggregate annually, and product liability insurance with



                                      -7-
<PAGE>   11
coverage limits of $1.0 million per incident and $3.0 million in the aggregate
annually. Our insurance policies provide coverage for product liability on a
claims made basis and general liability on an occurrence basis. These policies
are subject to annual renewal. Such insurance may not be available in the future
on acceptable terms or at all. There can be no assurance that our insurance
coverage will be adequate or that a product liability claim or recall would not
materially adversely affect our business or financial condition.

         OWNERSHIP OF OUR STOCK IS CONCENTRATED AMONG SEVERAL STOCKHOLDERS

         As of June 1, 1999 our directors and officers and their affiliates
beneficially owned approximately 25% of our outstanding common stock. As a
result, these stockholders have been able to exercise significant influence over
all matters requiring stockholder approval, including the election of directors
and approval of significant corporate transactions. Such concentration of
ownership may have the effect of delaying or preventing a change in control of
Celtrix.

         WE FACE RISKS ASSOCIATED WITH THE IMPACT OF YEAR 2000 ON OUR OPERATING
AND COMPUTER SYSTEMS

         We are currently assessing the impact of year 2000, or Y2k, on our
existing software and systems. We expect to implement successfully the systems
and software changes necessary to address Y2k issues, and do not believe that
the costs of such actions will have a material effect on our results of
operations or financial condition. However, many computer systems will
experience problems handling dates beyond the year 1999 and we do not know the
extent, if any, of the impact of the year 2000 on other systems and equipment of
third parties with which we do business. There can be no assurance that third
parties will address Y2k issues in a timely fashion, or at all. Any Y2k
compliance problem or delay of either Celtrix, our suppliers, our clinical
research organizations, or our collaborative partners could have a material
adverse effect on our business, operating results and financial conditions.

    WE FACE ONGOING COMPLIANCE ISSUES IN CONNECTION WITH OUR NASDAQ LISTING

         In November 1998, we received notice from the Nasdaq Stock Market that
we failed to comply with two Nasdaq continued listing requirements - the minimum
net tangible assets requirement and the minimum bid price requirement. In
January 1999, Nasdaq officials confirmed that we had regained compliance with
the minimum bid price requirement, but that we would be subject to delisting if
we failed to comply with the minimum net tangible assets requirement. In
response, we requested an oral hearing before a Nasdaq Listing Qualifications
Panel to present our plan to regain compliance with the minimum net tangible
assets requirement. We presented our plan at an oral hearing on April 1, 1999,
and on July 6, 1999, the Nasdaq panel informed us that our listing would be
moved from the Nasdaq National Market to the Nasdaq SmallCap Market effective
July 8, 1999, subject to our continued compliance with SmallCap listing
requirements. Although we intend to comply with all continued listing
requirements of the Nasdaq SmallCap Market, there can be no assurance that we
will be able to satisfy Nasdaq's requirements in the future. Failure to meet
Nasdaq's requirements may result in delisting by Nasdaq, which may have a
material adverse effect on the price of our common stock and the levels of
liquidity currently available to our stockholders.

         WE FACE OPERATIONAL RISKS ASSOCIATED WITH OUR RECENT RESTRUCTURING

         In order to reduce our cash burn rate and preserve value in our core
assets and technologies, in the second quarter of 1998, we restructured our
operations to eliminate manufacturing and announced a reduction in work force of
up to 90%. Such actions were designed to permit us to continue our clinical
development of SomatoKine. There can be no assurance that our recent
restructuring efforts will be successful or that we will be able to sustain our
clinical development activities going forward (with the



                                      -8-
<PAGE>   12
exception of the large scale Phase II trial in osteoporosis (hip fracture) which
will be undertaken by the Celtrix/Elan joint venture company newly formed in
April 1999). In addition, there can be no assurance that our management will not
deem it appropriate to undertake other restructuring efforts in the future or to
what degree any such efforts will result in improved performance or a reduction
in our cash burn rate.

         FUTURE SECURITY ISSUANCES WILL HAVE DILUTIVE AND POTENTIAL DILUTIVE
EFFECTS ON STOCKHOLDERS

         In November 1998, pursuant to the terms of a Common Stock and Warrant
Purchase Agreement dated October 12, 1998, we completed a private placement of
4,000,000 shares of our common stock, resulting in net proceeds, after deducting
estimated transaction costs, of approximately $1.9 million. Also in connection
with the offering, for every share of stock issued, we issued one and one-half
warrants to purchase additional shares at $0.55 per share. In April 1999, we
completed a private placement of 1,508,751 shares of our common stock to Elan
International Services, Ltd., resulting in net proceeds, after deducting
estimated transaction costs, of approximately $2.3 million. The foregoing
issuances of shares of our securities diluted the beneficial ownership of our
existing stockholders. Any additional equity financing may be dilutive to our
stockholders, and any debt financing, if available, may involve restrictions on
our ability to pay future dividends on our capital stock or the manner in which
we conduct business.



                                      -9-
<PAGE>   13
                                 USE OF PROCEEDS

    We will not receive any proceeds from the sale of Common Stock by the
Selling Stockholders in the Offering.

          ISSUANCE OF COMMON STOCK AND WARRANTS TO SELLING STOCKHOLDERS

         On November 20, 1998, pursuant to a Common Stock and Warrant Purchase
Agreement dated as of October 12, 1998, we completed the sale of 4,000,000
shares of our common stock and warrants to purchase 6,000,000 shares of our
common stock to the selling stockholders in a private placement transaction. We
also issued a warrant exercisable for 75,000 shares of common stock to Credit
Suisse First Boston Corporation who had previously acted as our placement agent.
This prospectus covers the resale of the 10,075,000 shares of our common stock
issued (or issuable upon exercise of the warrants issued) in connection with the
private placement to the selling stockholders.


                              PLAN OF DISTRIBUTION

         Shares of common stock offered by this prospectus may be offered and
sold from time to time by the selling stockholders. The selling stockholders
will act independently of us in making decisions with respect to the timing,
manner and size of each sale. The selling stockholders may sell shares on the
Nasdaq National Market, or in private sales at negotiated prices directly or
through a broker. The selling stockholders and any underwriters, dealers or
agents who participate in the distribution of the shares may be deemed to be
"underwriters" under the Securities Act of 1933. Any discount, commission or
concession received by such persons might be deemed to be an underwriting
discount or commission under the Securities Act. We have agreed to indemnify the
selling stockholders against certain liabilities arising under the Securities
Act.

         The selling stockholders will pay selling commissions or brokerage
fees, if any, with respect to the sale of the common stock offered by this
prospectus in amounts customary for this type of transaction. Each selling
stockholder will also pay all applicable transfer taxes and fees for its legal
counsel incurred in connection with the sale of shares.

         The anti-manipulation rules under the Securities Exchange Act of 1934
may apply to sales of the shares offered by this prospectus in the market, and
to their own activities and those of their affiliates. The selling stockholders
have advised us that during the time they are engaged in attempting to sell the
shares offered by this prospectus, they will:

         - notify us of its intent to sell any shares at least three (3) full
business days prior to such sale; and

         - furnish to each person to whom shares may be offered, and to each
broker-dealer, if any, through whom shares are offered, copies of this
prospectus, as supplemented or amended, as may be required by such person.

         We have agreed to use our best efforts to maintain the effectiveness of
this registration statement until the earlier of either the date that each
holder of shares can sell all of the shares it holds in any three-month period
in compliance with Rule 144 promulgated under the Securities Act or November 20,
2000. No sales may be made pursuant to this prospectus after the expiration date
unless we amend or



                                      -10-
<PAGE>   14
supplement this prospectus to indicate that we have agreed to extend the period
of effectiveness. The selling stockholders may sell all, some or none of the
shares offered by this prospectus.



                                      -11-
<PAGE>   15
                              SELLING STOCKHOLDERS

         The following table sets forth certain information as of June 1, 1999
with respect to the selling stockholders. The following table assumes that the
selling stockholders sell all of the shares offered by this prospectus. We are
unable to determine the exact number of shares that actually will be sold.

         The number and percentage of shares beneficially owned is based on
26,569,804 shares outstanding at June 1, 1999 determined in accordance with Rule
13d-3 of the Exchange Act. The information is not necessarily indicative of
beneficial ownership for any other purpose. Under Rule 13d-3, beneficial
ownership includes any shares as to which an individual has sole or shared
voting power or investment power, and also includes shares which an individual
has the right to acquire within 60 days of June 1, 1999 through the exercise of
any stock option, warrant or other right. Unless otherwise indicated in the
footnotes, each person has sole voting and investment power (or shares such
powers with his or her spouse) with respect to the shares shown as beneficially
owned.

         No selling stockholder has had any material relationship with us or any
of our predecessors or affiliates within the last three years.


<TABLE>
<CAPTION>
                                                    Shares Beneficially      Shares Offered       Shares Beneficially
                                                        Owned Prior             by this              Owned  After
        Selling Stockholder                          to the Offering(1)       Prospectus             the Offering
        -------------------                         -------------------      --------------       -------------------
                                                     Number     Percent                          Number          Percent
                                                     ------     -------                          ------          -------
<S>                                                 <C>         <C>         <C>                 <C>              <C>
Biotechnology Development Fund, L.P.                3,095,774     11.1%        1,250,000        1,845,774          6.9%
Frank Kung, General Partner
575 High Street, Suite 201
Palo Alto, CA  94301

Biotechnology Development Fund, III L.P.            2,500,000      8.9%        2,500,000                0             *
Frank Kung, General Partner
575 High Street, Suite 201
Palo Alto, CA  94301

Veron International, Ltd.                           3,272,887     11.6%        2,350,000          922,887          3.6%
Chinachem Golden Plaza
77 Mody Road
Tsin Sha Tsui East
Kowloon, Hong Kong
Attn:  W.K. Leung

Lee Wei Chen                                        2,350,000      8.4%        2,350,000                0             *
c/o Fu Sheng Industrial Co., Ltd.
172 Nanking East Road, Sec. 2
Taipei 104, Taiwan, R.O.C.
Attn:  Shubbin King

Hofung Holdings Limited                             1,042,287      3.8%          950,000           92,287             *
20 F East Town Bldg.
41 Lockard Rd.
Wanchai, Hong Kong
Attn:  Robert Ho
</TABLE>



                                      -12-
<PAGE>   16
<TABLE>
<CAPTION>
                                                    Shares Beneficially      Shares Offered       Shares Beneficially
                                                        Owned Prior             by this              Owned  After
        Selling Stockholder                          to the Offering(1)       Prospectus             the Offering
        -------------------                         -------------------      --------------       -------------------
                                                     Number     Percent                          Number          Percent
                                                     ------     -------                          ------          -------
<S>                                                 <C>         <C>         <C>                 <C>              <C>
Wanpyng Chuang and Jesse Chen                         342,287      1.3%          250,000           92,287             *
1608 Pebble Beach Ct.
Milpitas, CA  95035

Nai-Ping Leung                                        211,518        *           150,000           61,518             *
95A, Hill Road 1/F
Western District
Hong Kong

Wen-Chen Yuan                                         200,000        *           200,000                0             *
8/F 33 One hundred fifty first Avenue
Fourth District
Ren-ai Street
Taipei, R.O.C.

Credit Suisse First Boston Corporation                 75,000        *            75,000                0             *
Eleven Madison Avenue
New York, NY  10010-3629

                      Total                                                   10,075,000
</TABLE>


- ----------
*        Less than 1%



                                      -13-
<PAGE>   17
                                  LEGAL MATTERS

         The validity of the issuance of the common stock offered by this
prospectus will be passed upon by Venture Law Group, A Professional Corporation,
Menlo Park, California, counsel to Celtrix.


                                     EXPERTS

         The consolidated financial statements of Celtrix Pharmaceuticals, Inc.
appearing in Celtrix Pharmaceuticals, Inc.'s Annual Report (Form 10-K) for the
year ended March 31, 1999, have been audited by Ernst & Young LLP, independent
auditors, as set forth in their report thereon included therein and incorporated
herein by reference. Such consolidated financial statements are incorporated
herein by reference in reliance upon such report given upon the authority of
such firm as experts in accounting and auditing.


                       WHERE YOU CAN FIND MORE INFORMATION

         This prospectus is part of a registration statement on Form S-3 that we
filed with the Securities and Exchange Commissions. Certain information in the
registration statements has been omitted from this prospectus in accordance with
the rules of the SEC. We file proxy statements and annual, quarterly and special
reports and other information with the SEC. You can inspect and copy the
registration statement as well as the reports, proxy statements and other
information we have filed with the SEC at the public reference room maintained
by the SEC at 450 Fifth Street, N.W., Washington, D.C., and at the SEC Regional
Offices located at Citicorp Center, 500 West Madison Street, Suite 1400,
Chicago, Illinois 60661-2511 and 7 World Trade Center, Suite 1300, New York, New
York 10048. You can call the SEC at 1-800-732-0330 for further information about
the public reference rooms. We are also required to file electronic versions of
these documents with the SEC, which may be accessed from the SEC's World Wide
Web site at http://www.sec/gov. Reports, proxy and information statements and
other information concerning Celtrix may be inspected at The Nasdaq Stock Market
at 1735 K Street, N.W., Washington, D.C. 20006.

         The SEC allows us to "incorporate by reference" certain of our
publicly-filed documents into this prospectus, which means that information
included in those documents is considered part of this prospectus. Information
that we file with the SEC after the effective date of this prospectus will
automatically update and supersede this information. We incorporate by reference
the documents listed below and any future filings made with the SEC under
Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, until the selling
stockholders have sold all the shares.

         The following documents filed with the SEC are incorporated by
reference in this prospectus:

         1. Our Current Report on Form 8-K dated July 7, 1999.

         2. Our Annual Report on Form 10-K for the year ended March 31, 1999
(File No 0-18976).

         3. Our definitive Proxy Statement dated July 29, 1998 filed in
connection with our September 10, 1998 Annual Meeting of Stockholders.

         4. The description of our common stock in our Registration Statement on
Form 10 filed with the SEC on January 24, 1991.

         We will furnish without charge to you, on written or oral request, a
copy of any or all of the documents incorporated by reference, other than
exhibits to those documents. You should direct any requests for documents to
Chief Financial Officer, 2033 Gateway Place, Suite 600, San Jose, CA 95110,
telephone: (408) 988-2500.



                                      -14-
<PAGE>   18
                                     PART II
                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION

         The following table sets forth the costs and expenses payable by the
Registrant in connection with the sale and distribution of the common stock
being registered. Selling commissions and brokerage fees and any applicable
transfer taxes and fees and disbursements of counsel for the selling
stockholders are payable individually by the selling stockholders. All amounts
shown are estimates except the SEC registration fee and the Nasdaq listing fee.

<TABLE>
<CAPTION>
                                                                                                Amount
                                                                                              To be Paid
                                                                                              ----------
<S>                                                                                           <C>
SEC registration fee...............................................................           $  3,458
Legal fees and expenses............................................................             20,000
Accounting fees and expenses.......................................................             10,000
Nasdaq listing fees................................................................             17,500
Finders Fee (in connection with private placement) ................................             82,500
Miscellaneous expenses.............................................................              6,542
                                                                                              --------
         Total.....................................................................           $140,000
                                                                                              ========
</TABLE>

ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS

         Section 145 of the Delaware General Corporation Law authorizes a court
to award, or a corporation's Board of Directors to grant, indemnity to directors
and officers in terms sufficiently broad to permit such indemnification under
certain circumstances for liabilities (including reimbursement for expenses
incurred) arising under the Securities Act of 1933. Article Tenth of the
Registrant's Amended and Restated Certificate of Incorporation and Article VI of
the Registrant's Bylaws provide for indemnification of its directors, officers,
employees and other agents to the maximum extent permitted by law. In addition,
the Registrant has entered into Indemnification Agreements with its officers and
directors and maintains director and officer liability insurance.

         In connection with this offering, the selling stockholders have agreed
to indemnify the Registrant, its directors and officers and each such person who
controls the Registrant, against any and all liability arising from inaccurate
information provided to the Registrant by the selling stockholders and contained
herein up to a maximum of the net proceeds received by the selling stockholders
from the sale of their shares hereunder.

ITEM 16. EXHIBITS

<TABLE>
<CAPTION>
                    Exhibit
                     Number      Description of Exhibit
                     ------      ----------------------
<S>                              <C>
                      4.5        Form of Warrant of Registrant dated November
                                 20, 1998
                      5.1        Opinion of Venture Law Group, A Professional
                                 Corporation
</TABLE>



                                      II-1
<PAGE>   19
<TABLE>
<CAPTION>
                     Exhibit
                      Number      Description of Exhibit
                      ------      ----------------------
<S>                              <C>
                      10.55      Common Stock and Warrant Purchase Agreement
                                 dated as of October 12, 1998 between Celtrix
                                 and the selling stockholders

                      23.1       Consent of Ernst & Young LLP Independent
                                 Auditors (see page II-4)

                      23.2       Consent of Counsel (included in Exhibit 5.1)

                      24.1       Power of Attorney (see page II-3)
</TABLE>

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

ITEM 17. UNDERTAKINGS

         The undersigned Registrant hereby undertakes:

         (1) To file, during any period in which offers or sales are being made,
a post-effective amendment to this Registration Statement to include any
material information with respect to the plan of distribution not previously
disclosed in the Registration Statement or any material change to such
information in the Registration Statement.

         (2) That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (3) To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

         (4) That, for purposes of determining any liability under the
Securities Act of 1933, each filing of the Registrant's annual report pursuant
to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and,
where applicable, each filing of an employee benefit plan's annual report
pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is
incorporated by reference in the Registration Statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         Insofar as indemnification for liabilities arising under the Securities
Act of 1933 may be permitted to directors, officers and controlling persons of
the Registrant pursuant to the provisions referred to in Item 15 above or
otherwise, the Registrant has been advised that in the opinion of the Securities
and Exchange Commission such indemnification is against public policy as
expressed in the Securities Act of 1933 and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than the
payment by the Registrant of expenses incurred or paid by a director, officer or
controlling person of the Registrant in the successful defense of any action,
suit or proceeding) is asserted against the Registrant by such director, officer
or controlling person in connection with the securities being registered
hereunder, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act of 1933 and will be governed by the
final adjudication of such issue.



                                      II-2
<PAGE>   20
                                   SIGNATURES

    Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-3 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of San Jose, State of California, on the 14th day of
July 1999.

                                       CELTRIX PHARMACEUTICALS, INC.

                                       By: /s/ Andreas Sommer
                                           -------------------------------------
                                       Andreas Sommer, President and
                                       Chief Executive Officer


                                POWER OF ATTORNEY

    KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears
below hereby constitutes and appoints, Andreas Sommer and Donald D. Huffman, and
each of them acting individually, as his attorney-in-fact, each with full power
of substitution, for him in any and all capacities, to sign any and all
amendments to this Registration Statement (including post-effective amendments),
and to file the same, with exhibits thereto and other documents in connection
therewith, with the Securities and Exchange Commission, hereby ratifying and
confirming our signatures as they may be signed by our said attorney to any and
all amendments to said Registration Statement.

    PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, THIS
REGISTRATION STATEMENT HAS BEEN SIGNED BY THE FOLLOWING PERSONS IN THE
CAPACITIES AND ON THE DATES INDICATED:

<TABLE>
<CAPTION>
            SIGNATURE                                 TITLE                                    DATE
            ---------                                 -----                                    ----
<S>                                 <C>                                                    <C>
/s/   Andreas Sommer                President, Chief Executive Officer and Director        July 14, 1999
- -----------------------------       (Principal Executive Officer)
      (Andreas Sommer)




/s/   Donald D. Huffman              Vice President, Finance and Administration and        July 14, 1999
- -----------------------------        Chief Financial Officer
      (Donald D. Huffman)            (Principal Financial and Accounting Officer)




/s/   Henry E. Blair                 Director                                              July 14, 1999
- -----------------------------
      (Henry E. Blair)



/s/   Barry M. Sherman               Director                                              July 14, 1999
- -----------------------------
      (Barry M. Sherman)


/s/   James E. Thomas                Chairman of the Board of Directors                    July 14, 1999
- -----------------------------
      (James E. Thomas)
</TABLE>



                                      II-3
<PAGE>   21
               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS



         We consent to the reference to our firm under the caption "Experts" in
the Registration Statement (Form S-3) and the related Prospectus of Celtrix
Pharmaceuticals, Inc. for the registration of 10,075,000 shares of its common
stock and to the incorporation by reference therein of our report dated May 28,
1999, with respect to the consolidated financial statements of Celtrix
Pharmaceuticals, Inc. included in its Annual Report (Form 10-K) for the year
ended March 31, 1999 filed with the Securities and Exchange Commission.



                                          /s/ Ernst & Young LLP


Palo Alto, California
July 15, 1999


                                      II-4
<PAGE>   22
                          CELTRIX PHARMACEUTICALS, INC.

                                INDEX TO EXHIBITS

<TABLE>
<CAPTION>
   EXHIBIT
   NUMBER
   ------
<S>              <C>
    4.5          Form of Warrant of Registrant dated November 20, 1998

    5.1          Opinion of Venture Law Group, A Professional Corporation

    10.55        Common Stock and Warrant Purchase Agreement dated as of October
                 12, 1998 between Celtrix and each of the selling stockholders

    23.1         Form of Consent of Ernst & Young, Independent Auditors (see
                 page II-4)

    23.2         Form of Consent of Counsel (included in Exhibit 5.1)

    24.1         Power of Attorney (see page II-3)
</TABLE>



<PAGE>   1
                                                                     EXHIBIT 4.5

        THESE SECURITIES HAVE BEEN ACQUIRED FOR INVESTMENT AND MAY BE SOLD,
        OFFERED FOR SALE OR TRANSFERRED ONLY IN ACCORDANCE WITH THE PROVISIONS
        OF THIS WARRANT AND PURSUANT TO A REGISTRATION STATEMENT OR AN OPINION
        OF COUNSEL SATISFACTORY TO THE CORPORATION AS TO THE AVAILABILITY OF AN
        EXEMPTION FROM REGISTRATION.


C.S. NO. [WRNT]                                               [WRNTS] Shares


                           WARRANT TO PURCHASE SHARES
                               OF COMMON STOCK OF

                          CELTRIX PHARMACEUTICALS, INC.




        1. COMMON STOCK AND WARRANT PURCHASE AGREEMENT. This Warrant is issued
to [NAME] ("Purchaser") pursuant to the Common Stock and Warrant Purchase
Agreement dated as of October 12, 1998 (with a closing date of November 20,
1998) between Celtrix Pharmaceuticals, Inc., a Delaware company ("Celtrix"), and
Purchaser ("Purchase Agreement") in which Celtrix issued [UNITS] Units to
Purchaser. Each "Unit" is composed of one share of Celtrix Common Stock
("Share") and a warrant to purchase one and one half shares of Celtrix Common
Stock. This Warrant is part of the Unit.


        2. NUMBER AND PRICE OF SHARES SUBJECT TO WARRANT. Subject to the terms
and conditions herein set forth Purchaser is entitled to purchase from Celtrix,
at any time in whole or from time to time in part commencing on February 20,
1999 (the "Vesting Date") and until November 20, 2002, [WARRANTSPELLED]
([WRNTS]) shares (which number of shares is subject to adjustment as described
below) of fully paid and nonassessable Common Stock, $.01 par value, of Celtrix
("Warrant Shares"), upon surrender of this Warrant at the principal office of
Celtrix and upon payment of the purchase price by wire transfer to Celtrix or
cashiers check drawn on a United States bank made to the order of Celtrix.
Subject to adjustment as hereinafter provided, the purchase price of one Warrant
Share (or such securities as may be substituted for one Warrant Share pursuant
to the provisions hereinafter set forth) shall be $0.55. The purchase price of
one Warrant Share (or such securities as may be substituted for one Warrant
Share pursuant to the provisions hereinafter set forth) payable from time to
time upon the exercise of this Warrant (whether such price be the price
specified above or an adjusted price determined as hereinafter provided) is
referred to herein as the "Warrant Price."

               (a) ACCELERATION. In the event that a Corporate Transaction (as
defined in Section 13 below) is consummated by Celtrix prior to the Vesting
Date, this Warrant shall become immediately exercisable by the Registered Holder
(as defined in Section 9(c) below) for the full number of Warrant Shares set
forth above in this Section 2.


<PAGE>   2

        3. ADJUSTMENT OF WARRANT PRICE AND NUMBER OF SHARES. The number and kind
of securities issuable upon the exercise of this Warrant shall be subject to
adjustment from time to time upon the happening of certain events as follows:

               (a) ADJUSTMENT FOR DIVIDENDS IN STOCK OR OTHER SECURITIES OR
PROPERTY. In case at any time or from time to time on or after the date hereof
the holders of the Common Stock of Celtrix (or any shares of other stock or
other securities at the time issued and outstanding) shall have received, or, on
or after the record date fixed for the determination of eligible stockholders,
shall have become entitled to receive, without payment therefor, (i) other or
additional stock or other securities or property (other than cash in connection
with regular or ordinary dividends) of Celtrix by way of dividend, (ii) any cash
paid or payable (including, without limitation, by way of dividend), except out
of earned surplus of Celtrix, or (iii) other or additional stock or other
securities or property (including cash) by way of spin-off, split-up,
reclassification, recapitalization, combination of shares, or similar corporate
rearrangement, then and in each case, the holder of this Warrant shall, upon the
exercise hereof, be entitled to receive, in addition to the number of shares of
Common Stock receivable thereupon, and without payment of any additional
consideration therefor, the amount of such other or additional stock or other
securities or property (including cash in the cases referred to in clauses (ii)
and (iii) above) of Celtrix which such holder would hold on the date of such
exercise had it been the holder of record of such Common Stock on the date
hereof and had thereafter, during the period from the date hereof to and
including the date of such exercise, retained such shares and/or all other
additional stock available by it as aforesaid during such period, giving effect
to all adjustments called for during such period by paragraphs (b), (c) and (d)
of this Section 3.

               (b) ADJUSTMENT FOR RECLASSIFICATION, REORGANIZATION OR MERGER. In
case of any reclassification or change of the outstanding securities of Celtrix
or of any reorganization of Celtrix (or any other corporation the stock or
securities of which are at the time receivable upon the exercise of this
Warrant) or any similar corporate reorganization on or after the date hereof, or
any merger or consolidation of Celtrix, or any transfer of all or substantially
all of Celtrix's properties or assets to any other person or entity under any
plan or arrangement contemplating the dissolution of Celtrix within 6 months
from the date of such transfer, then and in each such case the holder of this
Warrant, upon the exercise hereof at any time after the consummation of such
reclassification, change, reorganization, merger or conveyance, shall be
entitled to receive, in lieu of the stock or other securities and property
receivable upon the exercise hereof prior to such consummation, the stock or
other securities or property to which such holder would have been entitled upon
such consummation if such holder had exercised this Warrant immediately prior
thereto, all subject to further adjustment as provided in paragraphs (a) and
(c); and in each such case, the terms of this Section 3 shall be applicable to
the shares of stock or other securities properly receivable upon the exercise of
this Warrant after such consummation.

               (c) STOCK SPLITS AND REVERSE STOCK SPLITS. If at any time on or
after the date hereof Celtrix shall subdivide its outstanding shares of Common
Stock into a greater number of shares, the Warrant Price in effect immediately
prior to such subdivision shall thereby be proportionately reduced and the
number of shares receivable upon exercise of the Warrant shall thereby be
proportionately increased; and, conversely, if at any time on or after the date
hereof

                                      -2-


<PAGE>   3

the outstanding number of shares of Common Stock shall be combined into a
smaller number of shares, the Warrant Price in effect immediately prior to such
combination shall thereby be proportionately increased and the number of shares
receivable upon exercise of Warrant shall thereby be proportionately decreased.

                (d) OTHER ADJUSTMENTS.

                        (i) IN GENERAL. In case Celtrix shall issue or sell
shares of its Common Stock after the date hereof without consideration or for a
consideration per share less than $0.4375 per share, except where such shares
are issued or sold pursuant to the circumstances set forth in subsection (iii)
below, then the Warrant Price in effect hereunder shall simultaneously with such
issuance or sale be reduced to a price determined by multiplying the Warrant
Price by a fraction (i) the numerator of which shall be the total number of
shares of Common Stock outstanding immediately prior to such issuance or sale
plus the number of shares of Common Stock that the aggregate consideration, if
any, received by Celtrix upon such issuance or sale would purchase at the
Warrant Price; and (2) the denominator of which shall be the total number of
shares of Common Stock outstanding immediately after issuance or sale of such
additional shares.

                        (ii) CONVERTIBLE SECURITIES. Subject to subsection (iii)
below, in case Celtrix shall issue or sell any securities convertible into
Common Stock of Celtrix ("Convertible Securities") after the date hereof, there
shall be determined the price per share for which Common Stock is issuable upon
the conversion or exchange thereof, such determination to be made by dividing
(a) the sum of the total amount received or receivable by Celtrix as
consideration, if any, for the issue or sale of all such Convertible Securities
and such additional consideration, if any, payable to Celtrix upon the
conversion or exchange thereof, by (b) the maximum number of shares of Common
Stock of Celtrix issuable upon the conversion or exchange of all of such
Convertible Securities. If the price per share so determined shall be less than
$0.4375 per share, then at such time as any of such Convertible Securities are
actually converted into shares of Common Stock, the Warrant Price shall be
adjusted pursuant to the formula set forth in Section 3(d)(i) above taking into
consideration only those Convertible Securities actually converted. The
foregoing adjustment(s) shall also reflect any increase or increases, with the
passage of time, in the amount of additional consideration, if any, payable to
Celtrix for such Convertible Securities, or any change to the rate of exchange
that may be applicable upon the conversion or exchange of such Convertible
Securities.

                        (iii) NONDILUTIVE ISSUANCES. The terms of Section
3(d)(i) and (ii) shall not apply to any of the following:

                                (1) Common Stock issued pursuant to a
transaction described in Section 3(c) hereof,

                                (2) Shares of Common Stock issuable or issued to
employees, consultants or directors of Celtrix directly or pursuant to a stock
option plan or restricted stock plan approved by the Board of Directors of
Celtrix,

                                      -3-

<PAGE>   4

                                (3) Capital stock, or options or warrants to
purchase capital stock, issued to financial institutions or lessors in
connection with commercial credit arrangements, equipment financings or similar
transactions,

                                (4) Shares of Common Stock or Preferred Stock
issuable upon exercise of warrants outstanding as of the date of this Warrant,

                                (5) Capital stock or warrants or options to
purchase capital stock issued in connection with bona fide acquisitions, mergers
or similar transactions, the terms of which are approved by the Board of
Directors of Celtrix.

        4. NO FRACTIONAL SHARES. No fractional shares of Warrant Shares will be
issued in connection with any exercise of this Warrant. In lieu of any
fractional shares which would otherwise be issuable, Celtrix shall pay cash
equal to the product of such fraction multiplied by the closing price of one
Warrant Share as reported on the Nasdaq National Market on the date of exercise.

        5. NO STOCKHOLDER RIGHTS. This Warrant shall not entitle its holder to
any of the rights of a stockholder of Celtrix.

        6. RESERVATION OF STOCK. Celtrix covenants that during the period this
Warrant is exercisable, Celtrix will reserve from its authorized and unissued
Common Stock a sufficient number of shares of Common Stock (or other securities,
if applicable) to provide for the issuance of Warrant Shares (or other
securities) upon the exercise of this Warrant. Celtrix agrees that its issuance
of this Warrant shall constitute full authority to its officers who are charged
with the duty of executing stock certificates to execute and issue the necessary
certificates for the Warrant Shares upon the exercise of this Warrant.

        7. EXERCISE OF WARRANT. This Warrant may be exercised by the holder
hereof, in whole or in part, by the surrender of this Warrant and the Notice of
Exercise attached hereto as Exhibit A duly completed and executed on behalf of
the holder hereof, at the principal office of Celtrix together with payment in
full of the Warrant Price then in effect with respect to the number of Warrant
Shares as to which the Warrant is being exercised. The Warrant Price shall by
wire transfer to Celtrix or cashiers check drawn on a United States bank made to
the order of Celtrix. This Warrant shall be deemed to have been exercised
immediately prior to the close of business on the date of its surrender for
exercise as provided above, and the person entitled to receive the Warrant
Shares issuable upon such exercise shall be treated for all purposes as the
holder of such shares of record as of the close of business on such date. As
promptly as practicable on or after such date and in any event within ten (10)
days thereafter, Celtrix at its expense shall cause to be issued and delivered
to the person or persons entitled to receive the same a certificate or
certificates for the number of full Warrant Shares issuable upon such exercise,
together with cash in lieu of any fraction of a share as provided above. The
Warrant Shares issuable upon exercise hereof shall, upon their issuance, be
fully paid and nonassessable. In the event that this Warrant is exercised in
part, Celtrix at its expense will execute and deliver a new Warrant of like
tenor exercisable for the number of shares for which this Warrant may then be
exercised.


                                      -4-

<PAGE>   5

        8. CERTIFICATE OF ADJUSTMENT. Whenever the Warrant Price or number or
type of securities issuable upon exercise of this Warrant is adjusted, as herein
provided, Celtrix shall, at its expense, promptly deliver to the record holder
of this Warrant a certificate of an officer of Celtrix setting forth the nature
of such adjustment and showing in detail the facts upon which such adjustment is
based.

        9. TRANSFERABILITY.

               (a) UNREGISTERED SECURITY. Each holder of this Warrant
acknowledges that this Warrant and the Warrant Shares have not been registered
under the Securities Act of 1933, as amended (the "Securities Act"), and agrees
not to sell, pledge, distribute, offer for sale, transfer or otherwise dispose
of this Warrant or any Warrant Shares issued upon its exercise in the absence of
(i) an effective registration statement under the Securities Act as to this
Warrant or such Warrant Shares and registration or qualification of this Warrant
or such Warrant Shares under any applicable U.S. federal or state securities law
then in effect or (ii) an opinion of counsel, satisfactory to Celtrix, that such
registration and qualification are not required. Each certificate or other
instrument for Warrant Shares issued upon the exercise of this Warrant shall
bear a legend substantially to the foregoing effect.

               (b) TRANSFERABILITY. Subject to the provisions of Section 9(a)
hereof, this Warrant and all rights hereunder are transferable, in whole or in
part, upon surrender of the Warrant with a properly executed assignment (in the
form of Exhibit B hereto) at the principal office of Celtrix, provided, however,
that this Warrant may not be transferred in part unless the transferee and any
subsequent transferee acquires the right to purchase at least 100,000 shares (as
adjusted pursuant to Section 3) of Warrant Shares hereunder.

               (c) WARRANT REGISTER. Celtrix will maintain a register containing
the name and address of Purchaser or its registered assign (the "Registered
Holder") of this Warrant. Until any transfer of this Warrant is made in the
warrant register, Celtrix may treat the Registered Holder of this Warrant as the
absolute owner hereof for all purposes; provided, however, that if this Warrant
is properly assigned in blank, Celtrix may (but shall not be required to) treat
the bearer hereof as the absolute owner hereof for all purposes, notwithstanding
any notice to the contrary. Any Registered Holder may change such Registered
Holder's address as shown on the warrant register by written notice to Celtrix
requesting such change.

        10. NOTICES OF RECORD DATE. In the event of:

               (a) any taking by Celtrix of a record of the holders of any class
of securities for the purpose of determining the holders thereof who are
entitled to receive any dividend (other than a cash dividend payable out of
earned surplus of Celtrix) or other distribution, or any right to subscribe for,
purchase or otherwise acquire any shares of stock of any class or any other
securities or property, or to receive any other right; or

               (b) any capital reorganization of Celtrix, any reclassification
or recapitalization of the capital stock of Celtrix or any transfer of all or
substantially all the assets of Celtrix to or consolidation or merger of Celtrix
with or into any other person; or


                                      -5-

<PAGE>   6

               (c) any voluntary or involuntary dissolution, liquidation or
winding-up of Celtrix, then and in each such event Celtrix will mail or cause to
be mailed to each holder of a Warrant a notice specifying (i) the date on which
any such record is to be taken for the purpose of such dividend, distribution or
right, and stating the amount and character of such dividend, distribution or
right, and (ii) the date on which any such reorganization, reclassification,
recapitalization, transfer, consolidation, merger, dissolution, liquidation or
winding-up is to take place, and the time, if any, as of which the holders of
record of Common Stock (or other securities) shall be entitled to exchange their
shares of Common Stock (or other securities) for securities or other property
deliverable upon such reorganization, reclassification, recapitalization,
transfer, consolidation, merger, dissolution, liquidation or winding-up. Such
notice shall be mailed at least 10 days prior to the date therein specified.

        11. REPLACEMENT OF WARRANTS. On receipt of evidence reasonably
satisfactory to Celtrix of the loss, theft, destruction or mutilation of any
Warrant and, in the case of any such loss, theft, destruction or mutilation of
any Warrant, on delivery of an indemnity agreement or security reasonably
satisfactory in form and amount to Celtrix or, in the case of any such
mutilation, on surrender and cancellation of such Warrant, Celtrix at its
expense will execute and deliver, in lieu thereof, a new Warrant of like tenor.

        12. MISCELLANEOUS. This Warrant shall be governed by the laws of the
State of California. The headings in this Warrant are for purposes of
convenience and reference only, and shall not be deemed to constitute a part
hereof. Neither this Warrant nor any term hereof may be changed, waived,
discharged or terminated orally but only by an instrument in writing signed by
Celtrix and the registered holder of warrants covering a majority of the Warrant
Shares reserved for issuance upon exercise of this Warrant. All notices and
other communications from Celtrix to the holder of this Warrant shall be
sufficient if in writing and sent by registered or certified mail, domestic or
international courier, or facsimile, return receipt requested, postage or
courier charges prepaid, to the address furnished to Celtrix in writing by
Purchaser. All such notices and communications shall be effective one (1)
trading day after being sent by courier or by facsimile with confirmation of
receipt or five (5) trading days after being sent by the other approved methods.
The invalidity or unenforceability of any provision hereof shall in no way
affect the validity or enforceability of any other provisions.


        13. TERMINATION. This Warrant (and the right to purchase securities upon
exercise hereof) shall terminate on the earlier of (i) November 20, 2002, (ii)
the sale, conveyance, disposal, or encumbrance of all or substantially all of
Celtrix's property or business or Celtrix's merger into or consolidation with
any other corporation (other than a wholly-owned subsidiary corporation) or any
other transaction or series of related transactions in which more than fifty
percent (50%) of the voting power of Celtrix is disposed of (a "Corporate
Transaction"), provided that this Section 13(ii) shall not apply to a merger
effected exclusively for the purpose of changing the domicile of Celtrix, or
(iii) such earlier time as provided in Section 2 above. In the event that
termination of this Warrant shall occur pursuant to subsection (ii) above, then
and only then shall the following subsection 13(a) be applicable.



                                      -6-

<PAGE>   7

                (a) NET ISSUE EXERCISE.

                        (i) In lieu of exercising this Warrant in the manner
provided above in Section 2, the Registered Holder may elect to receive shares
equal to the value of this Warrant (or the portion thereof being canceled) by
surrender of this Warrant at the principal office of Celtrix together with
notice of such election in which event Celtrix shall issue to holder a number of
shares of Common Stock computed using the following formula:

                             X =    Y (A - B)
                                    ---------
                                         A

Where          X = The number of shares of Common Stock to be issued to the
                   Registered Holder.

               Y = The number of shares of Common Stock purchasable under this
                   Warrant (at the date of such calculation).

               A = The fair market value of one share of Common Stock (at the
                   date of such calculation).

               B = The Warrant Price (as adjusted to the date of such
                   calculation).

                        (ii) For purposes of this Section 13(a), the fair market
value of one share of Common Stock on the date of calculation shall mean:

                                (A) if this Warrant is exercised at a time when
Celtrix Common Stock is traded on a securities exchange or The Nasdaq Stock
Market, The Nasdaq SmallCap Market or is actively traded over-the-counter, the
closing sale price of Celtrix Common Stock on the day prior to the date the
Warrant is submitted for exercise, but if no such closing sale price is
available, then:

                                        (1) if Celtrix Common Stock is traded on
a securities exchange, The Nasdaq Stock Market, or The Nasdaq SmallCap Market,
the fair market value shall be deemed to be the average of the closing prices
over a thirty (30) day period ending three days before the date of calculation;
or

                                        (2) if Celtrix Common Stock is actively
traded over-the-counter, the fair market value shall be deemed to be the average
of the closing bid or sales price (whichever is applicable) over the thirty (30)
day period ending three days before the date of calculation; or

                                (B) if (A) is not applicable, the fair market
value shall be at the highest price per share which Celtrix could obtain on the
date of calculation from a willing buyer (not a current employee or director or
an affiliate thereof) for shares of Common Stock sold by Celtrix, from
authorized but unissued shares, as determined in good faith by the Board of
Directors, unless Celtrix is at such time subject to a Corporate Transaction
described in subsection 13(ii) above, in which case the fair market value per
share of Common Stock shall be

                                      -7-


<PAGE>   8

deemed to be the value of the consideration per share received by the holders of
such stock pursuant to such Corporate Transaction.

        14. REMEDIES. Celtrix stipulates that the remedies at law of the holder
of this Warrant in the event of any default or threatened default by Celtrix in
the performance of or compliance with any of the terms of this Warrant are not
and will not be adequate, and that such terms may be specifically enforced by a
decreed for the specific performance of any agreement contained herein or by an
injunction against a violation of any of the terms hereof or otherwise.

        15. NEGOTIABILITY. This Warrant is issued upon the following terms, to
all of which each holder or owner hereof by the taking hereof consents and
agrees:

               (a) title to this Warrant may be transferred only in accordance
with the provisions of Section 9 hereunder; and

               (b) subject to the terms of Section 9, any person in possession
of this Warrant properly endorsed is authorized to represent himself as absolute
owner hereof and is empowered to transfer absolute title hereto by endorsement
and delivery hereof to a bona fide purchaser hereof for value; each prior taker
or owner waives and renounces all of his right, title and interest in this
Warrant in favor of each such bona fide purchaser and each such bona fide
purchaser shall acquire absolute title hereto and to all rights represented
hereby.


        16. EXTENDED EXPIRATION. The right to exercise this Warrant shall expire
at 5:00 P.M., PST, on November 20, 2002; provided, however, that if a
registration statement covering the Warrant Shares has not become effective
prior to the expiration date of the right to exercise this Warrant, then the
right to exercise this Warrant shall be extended and shall expire 30 days after
the effective date of such registration statement.

        17. ASSIGNABILITY. This Warrant may be assigned only in accordance with
the provisions set forth in Section 9.



        ISSUED this 20th day of November, 1998.



                                            CELTRIX PHARMACEUTICALS, INC.



                                            ------------------------------------
                                            Andreas Sommer
                                            Chief Executive Officer


                                       -8

<PAGE>   9



                                    EXHIBIT A


                          NOTICE OF INTENT TO EXERCISE
                  (To be signed only upon exercise of Warrant)



To:   CELTRIX PHARMACEUTICALS, INC.

The undersigned, the Holder of the within Warrant, hereby irrevocably elects to
exercise the purchase right represented by such Warrant for, and to purchase
thereunder, _____________ ____________________________ (_____________) shares of
Common Stock of Celtrix Pharmaceuticals, Inc. and herewith makes payment of
____________________ Dollars ($__________) thereof and requests that the
certificates for such shares be issued in the name of, and delivered to
________________________________, whose address is _____________________________
________________________________________________________________________________
_______________________________________________________________________________.


        DATED: ______________


                                ------------------------------------------------
                                (Signature must conform in all respects to name
                                of Holder as specified on the face of the
                                Warrant)


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

                                ------------------------------------------------
                                (Address)



<PAGE>   10




                                    EXHIBIT B

                                 ASSIGNMENT FORM

        FOR VALUE RECEIVED, _________________________________________ hereby
sells, assigns and transfers all of the rights of the undersigned under the
attached Warrant with respect to the number of shares of Common Stock covered
thereby set forth below, unto:
<TABLE>
<CAPTION>

     NAME OF ASSIGNEE             ADDRESS/FAX NUMBER              NO. OF SHARES
<S>                               <C>                             <C>
</TABLE>





Dated:_________________             Signature:
                                               ---------------------------------



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


                                    Witness:
                                               ---------------------------------






<PAGE>   1
                                                                     EXHIBIT 5.1

                                VENTURE LAW GROUP
                           a Professional Corporation
                               2800 Sand Hill Road
                              Menlo Park, CA 94025

                                 July 19, 1999

Celtrix Pharmaceuticals, Inc.
2033 Gateway Place, Suite 600
San Jose, California 95110

    REGISTRATION STATEMENT ON FORM S-3

Ladies and Gentlemen:

    We have examined the Registration Statement on Form S-3 to be filed by you
with the Securities and Exchange Commission on or about July 20, 1999 (the
"Registration Statement") in connection with the registration under the
Securities Act of 1933, as amended, of a total of 10,075,000 shares of your
Common Stock (the "Shares"), 4,000,000 of which Shares were issued to several
institutional stockholders (the "Stockholders") in a private placement on
November 20, 1998, and 6,075,000 of which Shares are issuable upon the exercise
of warrants (the "Warrants") issued to such Stockholders in such private
placement. As your legal counsel, we have examined the proceedings taken in
connection with the sale of the Shares and the Warrants to the Stockholders and
are familiar with the proceedings proposed to be taken by you, and the
Stockholders in connection with the sale of the Shares under the Registration
Statement.

    It is our opinion that the Shares are legally and validly issued, fully paid
and nonassessable (or in the case of the Shares issuable upon exercise of the
Warrants, will be legally and validly issued, fully paid and nonassessable upon
exercise of the Warrants in accordance with their terms) and when resold in the
manner referred to in the Registration Statement, the Shares will be legally and
validly issued, fully paid and nonassessable.

    We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to the use of our name wherever it appears in the
Registration Statement and any amendments to it.



                                       Sincerely,

                                       VENTURE LAW GROUP
                                       A Professional Corporation

                                       /s/ VENTURE LAW GROUP


ESR

<PAGE>   1


                   COMMON STOCK AND WARRANT PURCHASE AGREEMENT

                          DATED AS OF OCTOBER 12, 1998

                                     BETWEEN


                          CELTRIX PHARMACEUTICALS, INC.


                                       AND


                       THE PURCHASERS LISTED ON EXHIBIT A


<PAGE>   2

<TABLE>
<CAPTION>

                                      TABLE OF CONTENTS

                                                                                    Page
                                                                                    ----
<S>                                                                                 <C>
SECTION 1 - Sale of Common Stock and Warrants.........................................1
        1.1 Sale of Common Stock and Warrants.........................................1
        1.2 Closing Date..............................................................1
        1.3 Delivery..................................................................1
SECTION 2 - Representations and Warranties of Celtrix.................................1
        2.1 Organization and Standing.................................................2
        2.2 Corporate Power; Authorization............................................2
        2.3 Shares; Warrant Shares....................................................2
        2.4 Capitalization............................................................3
        2.5 SEC Documents; Financial Statements.......................................3
        2.6 Governmental Consents.....................................................4
        2.7 No Material Adverse Change................................................4
        2.8 Intellectual Property.....................................................5
        2.9 Litigation................................................................6
        2.10 Consistent Terms.........................................................6
        2.11 Subsidiaries.............................................................7
        2.12 Undisclosed Liabilities..................................................7
        2.13 Title to Properties......................................................7
        2.14 Employee Matters.........................................................7
        2.15 Taxes....................................................................8
        2.16 Brokers..................................................................8
        2.17 Environmental Matters....................................................8
        2.18 Use of Proceeds..........................................................9
        2.19 Compliance with Applicable Laws..........................................9
        2.20 Disclosure...............................................................9
        2.21 Year 2000 Compliance.....................................................9
SECTION 3 - Representations and Warranties of Purchasers.............................10
        3.1 Investment Experience....................................................10
        3.2 Investment Intent........................................................10
        3.3 Registration or Exemption Requirements...................................10
        3.4 No Legal, Tax or Investment Advice.......................................10
SECTION 4 - Conditions to Obligations of Purchasers..................................11
        4.1 Representations and Warranties Correct...................................11
        4.2 Covenants................................................................11
        4.3 Opinion of Company's Counsel.............................................11
        4.4 No Order Pending.........................................................11
        4.5 No Law Prohibiting or Restricting Such Sale..............................11
        4.6 Compliance Certificate...................................................11
        4.7 No Material Adverse Change...............................................11
        4.8 Governmental Approvals...................................................11
        4.9 Closing Bid Price of Celtrix Stock.......................................12

                                           i
</TABLE>

<PAGE>   3

<TABLE>
<CAPTION>

                                      TABLE OF CONTENTS
                                         (CONTINUED)

                                                                                    Page
                                                                                    ----
<S>                                                                                 <C>
        4.10 Deliveries..............................................................12
SECTION 5 - Conditions to Obligations of Celtrix.....................................12
        5.1 Representations and Warranties Correct...................................12
        5.2 Covenants................................................................12
        5.3 No Order Pending.........................................................12
        5.4 No Law Prohibiting or Restricting Such Sale..............................12
        5.5 Governmental Approvals...................................................13
SECTION 6 - Covenants of Celtrix.....................................................13
        6.1 Warrants.................................................................13
        6.2 Registration Requirements................................................13
        6.3 Financial Information....................................................17
        6.4 Budget...................................................................17
        6.5 Access...................................................................17
        6.6 Board of Directors.......................................................17
        6.7 Proceedings..............................................................17
        6.8 Insurance................................................................17
        6.9 Proprietary Information Agreements.......................................18
        6.10 Taxes and Other Liabilities.............................................18
        6.11 Corporate Existence.....................................................18
        6.12 Business................................................................18
        6.13 Compliance with Laws....................................................18
        6.14 Indemnification.........................................................18
        6.15 Material Events.........................................................20
        6.16 Stockholder Ratification................................................20
SECTION 7 - Covenants of Purchasers..................................................20
        7.1 Notice to Company of Proposed Sale and Right of Company to Suspend Use
        of Registration Statement....................................................20
        7.2 Restrictions on Short-Sales..............................................21
SECTION 8 - Restrictions on Transferability of Shares; Compliance With Securities
Act..................................................................................21
        8.1 Restrictions on Transferability..........................................21
        8.2 Restrictive Legend.......................................................21
SECTION 9 - Miscellaneous............................................................22
        9.1 Termination of Agreement.................................................22
        9.2 Best Efforts.............................................................22
        9.3 Governing Law............................................................22
        9.4 Survival.................................................................22
        9.5 Successors and Assigns...................................................22
        9.6 Entire Agreement; Amendment..............................................22
        9.7 Notices and Dates........................................................23

                                              -ii-
</TABLE>
<PAGE>   4


<TABLE>
<CAPTION>

                                      TABLE OF CONTENTS
                                         (CONTINUED)

                                                                                    Page
                                                                                    ----
<S>                                                                                 <C>
        9.8 Severability.............................................................23
        9.9 No Third Party Rights....................................................24
        9.10 Counterparts............................................................24
        9.11 Expenses................................................................24


Exhibits

A.      Schedule of Purchasers
B.      Warrant
C.      Schedule of Exceptions
D.      Budget



                                             -iii-
</TABLE>


<PAGE>   5
                   COMMON STOCK AND WARRANT PURCHASE AGREEMENT


        THIS COMMON STOCK AND WARRANT PURCHASE AGREEMENT ("Agreement") is
entered into as of this 12th day of October, 1998 (the "Effective Date") between
Celtrix Pharmaceuticals, Inc., a Delaware corporation ("Celtrix"), and the
purchasers listed on the attached Exhibit A (each a "Purchaser" and together the
"Purchasers").

                                    SECTION 1

                        SALE OF COMMON STOCK AND WARRANTS

        1.1 SALE OF COMMON STOCK AND WARRANTS. Subject to the terms and
conditions hereof, Celtrix will issue and sell to each Purchaser, and each
Purchaser will purchase from Celtrix, at the Closing (as defined below) the
number of Units set forth opposite each Purchaser's name on Exhibit A. A "Unit"
shall be composed of one share ("Share") of common stock, $0.01 par value, of
Celtrix ("Common Stock") and a warrant to purchase one and one half shares of
Common Stock (each single share, a "Warrant Share"). A form of the warrant is
attached as Exhibit B ("Warrant"). The purchase price per Unit ("Unit Purchase
Price") shall be $0.50. The exercise price per Warrant Share shall be equal to
110% of the Unit Purchase Price (or $0.55 per Warrant Share). Units shall be
purchased hereunder in even increments.

        1.2 CLOSING DATE. The closing of the purchase and sale of the Units
("Closing") shall be held at the law offices of Venture Law Group, 2800 Sand
Hill Road, Menlo Park, California not later than thirty (30) days after the
Effective Date, or at such other time and place upon which Celtrix and the
Purchasers purchasing a majority of the Units shall mutually agree (the date of
the Closing is hereinafter referred to as the "Closing Date").

        1.3 DELIVERY. At the Closing, Celtrix will deliver to each Purchaser
certificates representing the Shares and Warrants purchased by such Purchaser,
against payment of the aggregate Unit Purchase Price therefor, by wire transfer
to Celtrix or certified or cashier's check drawn on a United States bank made to
the order of Celtrix.

                                    SECTION 2

                    REPRESENTATIONS AND WARRANTIES OF CELTRIX

        Celtrix hereby represents and warrants to the Purchasers as of the
Closing Date that, except as set forth on the Schedule of Exceptions attached
hereto as Exhibit C, which exceptions shall be deemed to be representations and
warranties as if made hereunder:

        2.1 ORGANIZATION AND STANDING. Celtrix is a corporation duly
organized and validly existing under, and by virtue of, the laws of the State of
Delaware and is in good standing as a domestic corporation under the laws of
said state and is qualified as a foreign corporation in California and in all
other jurisdictions in which such qualification is required; provided, however,
that Celtrix need not be qualified in a jurisdiction in which its failure to
qualify would


<PAGE>   6

not have a material adverse effect on the business, properties, prospects or
financial condition of Celtrix.

        2.2 CORPORATE POWER; AUTHORIZATION. Celtrix has all requisite legal
and corporate power and has taken all requisite corporate action to execute and
deliver this Agreement and the Warrants, to sell and issue the Shares, the
Warrants and the Warrant Shares and to carry out and perform all of its
obligations under this Agreement and the Warrants. This Agreement and the
Warrants constitute the legal, valid and binding obligation of Celtrix,
enforceable in accordance with their terms, except (i) as limited by applicable
bankruptcy, insolvency, reorganization or similar laws relating to or affecting
the enforcement of creditors' rights generally and (ii) as limited by equitable
principles generally. The execution and delivery of this Agreement and the
Warrants does not, and the performance of this Agreement and the Warrants and
the compliance with the provisions hereof and thereof and the issuance, sale and
delivery of the Shares, the Warrants and the Warrant Shares by Celtrix will not
materially conflict with, or result in a breach or violation of the terms,
conditions or provisions of, or constitute a default under, or result in the
creation or imposition of any lien pursuant to the terms of, the Certificate of
Incorporation or Bylaws of Celtrix or any statute, law, rule or regulation or
any state or federal order, judgment or decree or any note, bond, indenture,
mortgage, lease, license, permit, franchise or other agreement, obligation or
instrument to which Celtrix, or any of its properties, is subject. The execution
and delivery of this Agreement and the Warrant and the consummation of the
transactions contemplated herein and therein have been duly and validly
authorized and approved by Celtrix's Board of Directors, and no other corporate
or stockholder approval or proceedings are necessary to authorize or approve
this Agreement, the Warrant, or to consummate the transactions contemplated
hereby and thereby. True and complete copies of the respective minutes of all
meetings or consent actions of the Board of Directors and stockholders of
Celtrix have been delivered to or made available to Purchasers and accurately
reflect all actions taken by the Board of Directors and stockholders of Celtrix.
As of the date hereof Celtrix is not subject to any bankruptcy or reorganization
proceedings or arrangement or moratorium affecting the enforcement of creditors
rights generally.

        2.3 SHARES; WARRANT SHARES. The Shares and the Warrants (and the
Warrant Shares issuable upon exercise of the Warrants) when issued in compliance
with the provisions of this Agreement or the Warrants, as the case may be, will
be duly and validly authorized, issued, fully paid and nonassessable. Based on
the representations and warranties of the Purchasers contained herein, the
Shares and the Warrants (and the Warrant Shares) when issued in compliance with
the provisions of this Agreement or the Warrants, as the case may be, will be
issued in compliance with federal and state securities laws. The issuance and
delivery of the Shares and the Warrants (and the Warrant Shares upon exercise of
the Warrants) is not subject to preemptive or any other similar rights of the
stockholders of Celtrix or any liens or encumbrances. Celtrix has reserved such
number of shares of its Common Stock necessary for issuance of the Warrant
Shares.

        2.4 CAPITALIZATION. The authorized capital stock of Celtrix consists
of 60,000,000 shares of Common Stock, $0.01 par value, of which at September 30,
1998, 21,061,053 shares were issued and outstanding, and 10,000,000 shares of
Preferred Stock, $0.01 par value per share, no shares of which are issued and
outstanding. All such issued and outstanding shares


                                      -2-
<PAGE>   7

have been duly authorized and validly issued and are fully paid and
nonassessable. All offers and sales of securities by Celtrix have been duly and
properly made pursuant to registrations conducted under applicable federal and
state securities laws or pursuant to exemptions from the registration
requirements thereof. In addition to the foregoing, Celtrix has reserved and
outstanding the following warrants, options and convertible securities: (i)
warrants for the purchase of 687,155 shares of Common Stock at an exercise price
of $9.00 per share, which warrants expire November 17, 1998; (ii) warrants for
the purchase of 2,860,934 shares of Common Stock at an exercise price of $2.6818
per share, which warrants expire April 1, 2000; (iii) an option for the purchase
of 75,000 shares of Common Stock at an exercise price of $2.438 per share, which
option expires April 1, 2000; (iv) 3,000,000 shares reserved for issuance
pursuant to Celtrix's 1991 Stock Option Plan, of which, at September 30, 1998
options to purchase 32,174 shares had been exercised, options to purchase
1,714,358 shares were outstanding and 1,253,468 shares remained available for
future grant; (v) 500,000 shares reserved for issuance pursuant to Celtrix's
1991 Employee Stock Purchase Plan, of which, at September 30, 1998, 176,880
shares had been issued and 323,120 shares remained available for future
issuance; and (vi) 200,000 shares reserved for issuance under Celtrix's 1991
Directors' Stock Option Plan, of which, at September 30, 1998, options to
purchase 29,999 shares were outstanding and 170,001 shares remained available
for future grant. Except for securities issued in the ordinary course of
business under Celtrix's stock plans, no additional securities of Celtrix will
be issued and outstanding as of the Closing. Except as described in this Section
2.4 and except for E.M. Warburg, Pincus and Company's right to purchase such
amount of newly issued securities of Celtrix in order to maintain their
respective percentage ownership of Celtrix Common Stock (which rights have been
waived by E.M. Warburg, Pincus and Company in connection with the transactions
contemplated by this Agreement), there are no other options, warrants,
conversion privileges or other contractual rights currently outstanding that
would obligate Celtrix to sell or otherwise issue any authorized but unissued
shares of Celtrix's capital stock or other securities or to grant or enter into
any such option, warrant, conversion privilege or other contractual right to
purchase or otherwise acquire Celtrix securities. In addition to the foregoing,
as of the date hereof, Celtrix has no bonds, debentures, notes or other
indebtedness outstanding that have voting rights in Celtrix, and Celtrix is not
subject to any agreement, understanding or commitment which would require it to
issue any such bonds, debentures, notes or other indebtedness. Except as set
forth in the Schedule of Exceptions, Celtrix is not presently under any
contractual obligation to register any of its presently outstanding securities
or any of its securities that may be hereafter issued.

        2.5 SEC DOCUMENTS; FINANCIAL STATEMENTS. Each complete or partial
statement, report, prospectus and other document filed by Celtrix under the
Securities Act of 1933, as amended ("Securities Act") and the Securities
Exchange Act of 1934, as amended ("Exchange Act"), is a true and complete copy
of or excerpt from such document as filed by Celtrix with the SEC ("SEC
Documents"). Celtrix has filed all the documents that Celtrix was required to
file with the SEC under Sections 13 or 14(a) of the Exchange Act since the date
on which its Registration Statement filed in connection with its initial public
offering of securities was declared effective. As of their respective filing
dates, the SEC Documents complied in all material respects with the requirements
of the Exchange Act or the Securities Act, as applicable. None of the SEC
Documents as of their respective dates contained any untrue statement of a


                                      -3-

<PAGE>   8

material fact or omitted to state a material fact required to be stated therein
or necessary to make the statements made therein, in light of the circumstances
under which they were made, not misleading. The financial statements of Celtrix
included in the SEC Documents ("Financial Statements") comply as to form in all
material respects with applicable accounting requirements and with the published
rules and regulations of the SEC with respect thereto. Except as may be
indicated in the notes to the Financial Statements or, in the case of unaudited
statements, as permitted by Form 10-Q of the SEC, the Financial Statements have
been prepared in accordance with generally accepted accounting principles
consistently applied and fairly present the consolidated financial position of
Celtrix and any subsidiaries at the dates thereof and the consolidated results
of their operations and consolidated cash flows for the periods then ended
(subject, in the case of unaudited statements, to normal, recurring
adjustments). To the knowledge of Celtrix, no holder of any securities of
Celtrix has any bona fide claim against Celtrix pursuant to any federal or state
law, including, but not limited to Section 10(b)(5) of the Exchange Act.

        2.6 GOVERNMENTAL CONSENTS. No consent, approval, order or
authorization of, or registration, qualification, designation, declaration or
filing with, any federal, state, or local governmental authority, including
without limitation the U.S. Food and Drug Administration, on the part of Celtrix
is required in connection with the consummation of the transactions contemplated
by this Agreement except for (a) compliance with foreign securities laws,
federal securities laws and state "blue sky" laws in the jurisdictions in which
Units are offered and/or sold, which compliance will be effected in accordance
with such laws, (b) filing the Nasdaq National Market Notification Form for
listing of additional shares, which filing will be effected in accordance with
the rules thereunder or an appropriate waiver will be obtained, and (c) filing
with the SEC and NASD either a Current Report on Form 8-K or a Quarterly or
Annual Report on Form 10-Q or 10-K disclosing the terms of the transaction
contemplated by this Agreement. The business of Celtrix is not being conducted
in violation of any law, ordinance or regulation of any governmental entity,
including but not limited to the U.S. Food and Drug Administration, except for
violations which either singly or in the aggregate would not be reasonably
likely to have a material adverse effect on Celtrix's business, financial
condition or results of operations.

        2.7 NO MATERIAL ADVERSE CHANGE. Except as otherwise disclosed herein
or in the Financial Statements, since June 30, 1998, there has not been:

               (a) any changes in the assets, liabilities, financial condition
or operations of Celtrix from that reflected in the Financial Statements except
changes in the ordinary course of business which have not been, either in any
individual case or in the aggregate, materially adverse;

               (b) any material change in the contingent obligations of Celtrix,
whether by way of guarantee, endorsement, indemnity, warranty or otherwise;

               (c) any damage, destruction or loss, whether or not covered by
insurance, materially and adversely affecting the properties or business of
Celtrix;


                                      -4-

<PAGE>   9

               (d) any declaration or payment of any dividend or other
distribution of the assets of Celtrix;

               (e) any labor organization activity;

               (f) any purchase or redemption of the capital stock of Celtrix;

               (g) any declaration, payment, or commitment for the payment by
Celtrix of a bonus or other additional salary, compensation or benefit to any
employee of Celtrix that was not in the ordinary course of business;

               (h) any release, compromise, waiver or cancellation of any debts
to or claims by Celtrix, or waiver of any rights of Celtrix;

               (i) any capital expenditure in excess of $10,000 for a single
item or $25,000 in the aggregate;

               (j) any change in accounting methods or practices or revaluation
of assets of Celtrix;

               (k) any loans by Celtrix or guarantees by Celtrix of any loans;

               (l) any termination of any material contract, or any amendment of
a material contract to which Celtrix is a party;

               (m) any resignation by or termination of key employees of
Celtrix;

               (n) any failure by Celtrix to satisfy any debts, obligations or
liabilities as the same come due; or

               (o) any agreement or commitment to any of the foregoing, or any
other event or condition of any character which has materially and adversely
affected Celtrix's assets, liabilities, financial condition or operations or
prospects.

        2.8 INTELLECTUAL PROPERTY. Celtrix has sufficient title and ownership
of all patents, patent applications, copyrights, trade secrets, trademarks,
proprietary information, proprietary rights, and processes necessary for its
business as now conducted and as now proposed to be conducted without any
conflict with or infringement of the rights of others except as disclosed in the
documents filed with the SEC, to the knowledge of Celtrix. The research,
development, manufacture, sale, and use of products presently made, used, or
sold by, or contemplated for future manufacture, sale or use by Celtrix, do not
and would not constitute or involve a significant risk of infringement of any
patent or misappropriation of any trade secret of any third party, except as
disclosed in the SEC Documents. Except as disclosed in the documents filed with
the SEC, there are no outstanding options, licenses, or agreements of any kind
relating to any material use of the foregoing, nor is Celtrix bound by or a
party to any options, licenses, encumbrances or liens, or any outstanding
orders, judgments, decrees, stipulations, or agreements of any kind with respect
to the patents, trademarks, service marks, trade names, copyrights, trade



                                      -5-

<PAGE>   10

secrets, licenses, information, proprietary rights and processes of any other
person or entity that are material to Celtrix's business as currently conducted
or as now proposed to be conducted. Except as disclosed in the documents filed
with the SEC, Celtrix has not received any communications alleging, nor does
Celtrix have any reason to believe, that Celtrix, by conducting its business as
proposed, would violate any of the patents, trademarks, service marks, trade
names, copyrights, or trade secrets or other proprietary rights of any other
person or entity. Celtrix is not aware that any of its employees or consultants
is obligated under any contract (including licenses, covenants or commitments of
any nature) or other agreement, or subject to any judgment, decree or order of
any court or administrative agency, that is violated by or would materially
interfere with the current or prospective services provided to Celtrix by the
employee or consultant or the use of his best efforts to promote the interests
of Celtrix or that would materially conflict with Celtrix's business as now
proposed to be conducted. Neither the execution nor delivery of this Agreement,
nor the carrying on of Celtrix's business as proposed, will, to Celtrix's
knowledge, conflict with or result in a material breach of the terms, conditions
or provisions of, or constitute a material default under, any contract, covenant
or instrument under which any of such employees is now obligated. To Celtrix's
knowledge, no third party is conducting or planning to conduct any activity that
would constitute an infringement of Celtrix's intellectual property rights.

        2.9 LITIGATION. Celtrix is not engaged in, or a party to, or
threatened with, any claim or legal action or other proceeding before any court,
any arbitrator of any kind or any administrative agency, or any governmental
investigation, which could have a material adverse effect on Celtrix's business,
financial condition or results of operations, nor to Celtrix's knowledge does
any basis for any claim or legal action or other proceeding or governmental
investigation exist. There are no orders, rulings, decrees, judgments or
stipulations to which Celtrix is a party by or with any court, arbitrator or
administrative agency and to Celtrix's knowledge, there are no other such
orders, rulings, decrees, judgments or stipulations affecting Celtrix's
business, financial condition or results of operations.

        2.10 CONSISTENT TERMS. No Units are being issued and sold at the
Closing other than pursuant to the Agreement and if Celtrix shall enter into any
other agreement, side letter or other understanding with any Purchaser listed on
Exhibit A or any other purchaser containing additional or contrary undertakings
or terms to those contained herein in connection with the issuance and sale of
Units at the Closing, Celtrix shall make such undertakings or terms available to
each other Purchaser.

        2.11 SUBSIDIARIES. Celtrix has no subsidiaries and does not otherwise
own or control, directly or indirectly, any equity interest in, or any security
convertible into an equity interest in, any corporation, partnership, limited
liability company, joint venture, association or other business entity.

        2.12 UNDISCLOSED LIABILITIES. Celtrix does not have any debt,
liability or obligation of any kind, whether accrued, absolute or otherwise,
including, without limitation, any liability or obligation on account of taxes
or any governmental charges or penalty, interest or fines, except


                                      -6-

<PAGE>   11

liabilities reflected on the Financial Statements and liabilities incurred as a
result of the transactions contemplated by this Agreement, including the costs
associated with this transaction.

        2.13 TITLE TO PROPERTIES. Celtrix has good and marketable title to all
tangible property and assets set forth in its June 30, 1998 balance sheet and
good title to all of its leasehold interests, in each case, free and clear of
any and all liens, claims and encumbrances.

        2.14 EMPLOYEE MATTERS.

               (a) Celtrix is not a party to any collective bargaining
agreement, no collective bargaining agent has been certified as a representative
of any of the employees of Celtrix, no representation campaign or election is
now in progress with respect to any employee of Celtrix and there are no labor
disputes, grievances, controversies, strikes or requests for union
representation pending, or, to the knowledge of Celtrix, threatened, relating to
or affecting the Business. To the knowledge of Celtrix, no event has occurred
that could give rise to any such dispute, controversy, strike or request for
representation.

               (b) Except as disclosed in the SEC Documents, there are no
employee benefit plans, agreements or arrangements maintained by Celtrix,
including, without limitation, (i) "employee benefit plans," within the meaning
of Section 3(3) of the Employee Retirement Income Security Act of 1974, as
amended ("ERISA"); (ii) affirmative action plans; (iii) current or deferred
compensation, pension, profit sharing, vacation or severance plans or programs;
or (iv) medical, hospital, accident, disability or death benefit plans
(collectively, "Benefit Plans"). All the Benefit Plans are administered in
accordance with, and are in material compliance with, all applicable laws and
regulations. No default exists with respect to the obligations of Celtrix under
any Benefit Plans.

               (c) All the Benefit Plans that are subject to ERISA have been
administered in accordance with, and are in compliance with, the applicable
provisions of ERISA. Each of Celtrix's Benefit Plans that is intended to meet
the requirements of Section 401(a) of the Internal Revenue Code of 1986, as
amended (the "Code") has been determined by the Internal Revenue Service to meet
such requirements within the meaning of such provision. No Celtrix Benefit Plan
is subject to Title IV of ERISA or Section 412 of the Code. Celtrix has not
engaged in any nonexempt "prohibited transactions," as such term is defined in
Section 4975 of the Code or Section 406 of ERISA, involving Celtrix Benefit
Plans that would subject Celtrix to the penalty or tax imposed under Section
502(i) of ERISA or Section 4975 of the Code. Celtrix has not engaged in any
transaction described in Section 4069 of ERISA within the last five years.
Neither the execution and delivery of this Agreement nor the consummation of the
transactions contemplated hereby will (i) result in any payment (including,
without limitation, severance, unemployment compensation or golden parachute)
becoming due to any director or other employee of Celtrix, (ii) increase any
benefits otherwise payable under any Benefit Plan or (iii) result in the
acceleration of the time of payment or vesting of any such benefits to any
extent.

               (d) No notice of a "reportable event," within the meaning of
Section 4043 of ERISA for which the 30-day reporting requirement has not been
waived, has been required to be


                                      -7-
<PAGE>   12

filed for any Benefit Plan that is an "employee pension benefit plan" within the
meaning of Section 3(2) of ERISA and that is intended to meet the requirements
of Section 401(a) of the Code, or by any entity that is considered one employer
with Celtrix under Section 4001 of ERISA or Section 414 of the Code (an "ERISA
Affiliate"), within the 12-month period ending on the date hereof. Celtrix has
not incurred any liability to the Pension Benefit Guaranty Corporation in
respect of any Benefit Plan that remains unpaid.

        2.15 TAXES.

               (a) As of the date hereof, Celtrix has filed all federal, state
and local tax returns required to be filed by it, all of such returns were
correct and complete as of the time of filing, and Celtrix has paid all taxes
required to be paid by it. Celtrix has provided or made available to Purchasers
copies of all federal, state and local income, franchise, excise, real and
personal property and other tax returns and reports, including extensions, filed
by Celtrix on or prior to the date hereof. As of the date hereof, Celtrix has
not been subject to any tax audit.


               (b) Celtrix is not a party to, or bound by, or otherwise in any
way obligated under, any tax sharing or similar agreement.


        2.16 BROKERS. Except for the agreement with BioAsia dated _______,
1998, no broker or finder is entitled to any broker's or finder's fee or other
commission in connection with the transactions contemplated by this Agreement as
a result of arrangements made by or on behalf of Celtrix.

        2.17 ENVIRONMENTAL MATTERS.

               (a) To the knowledge of Celtrix, no real property currently or
formerly owned or operated by Celtrix is contaminated with any Hazardous
Substances (as hereinafter defined).

               (b) Celtrix is not a party to any litigation or administrative
proceeding nor, to the knowledge of Celtrix, is any litigation or administrative
proceeding threatened against it, that, in either case, asserts or alleges that
Celtrix (i) violated any Environmental Laws (as hereinafter defined); (ii) is
required to clean up, remove or take remedial or other response action due to
the disposal, deposit, discharge, leak or other release of any Hazardous
Substances; or (iii) is required to pay all or a portion of the cost of any
past, present or future cleanup, removal or remedial or other action that arises
out of or is related to the disposal, deposit, discharge, leak or other release
of any Hazardous Substances.

               (c) To the knowledge of Celtrix, there are not now nor have there
previously been tanks or other facilities on, under, or at any real property
owned, leased, used or occupied by Celtrix containing materials that, if known
to be present in soils or ground water, would require cleanup, removal or other
remedial action under Environmental Laws.

               (d) To the knowledge of Celtrix, Celtrix is not subject to any
judgment, order or citation related to or arising out of any Environmental Laws
and has not been named or listed

                                      -8-


<PAGE>   13

as a potentially responsible party by any governmental agency in a matter
related to or arising out of any Environmental Laws.

               (e) For purposes of this Agreement, (i) the term "Environmental
Law" means any federal, state or local law (including statutes, regulations,
ordinances, codes, rules, judicial opinions and other governmental restrictions
and requirements), relating to the discharge of air pollutants, water
pollutants, noise, odors or process waste water, or otherwise relating to the
environment or hazardous or toxic substances; and (ii) the term "Hazardous
Substance" means any toxic or hazardous substance that is regulated by or under
authority of any Environmental Law, including, without limitation, any petroleum
products, asbestos or polychlorinated biphenyls.

        2.18 USE OF PROCEEDS. The proceeds of the transactions contemplated by
this Agreement will be used in accordance with Schedule 2.18 hereto.

        2.19 COMPLIANCE WITH APPLICABLE LAWS. Celtrix holds all material
permits, licenses, variances, exemptions, orders and approvals necessary to own,
lease or operate all of the assets and properties of Celtrix, as appropriate,
and to carry on its business as now conducted and contemplated (the "Permits").
Celtrix is in material compliance with all applicable laws, ordinances and
regulations and the terms of the Permits.

        2.20 DISCLOSURE. To Celtrix's knowledge, it has disclosed to Purchasers
all material information regarding Celtrix requested by Purchasers.

        2.21 YEAR 2000 COMPLIANCE. All software utilized by Celtrix in its
business and all equipment and all systems utilized by Celtrix having embedded
microchips will properly execute across and within multiple century dates so
that when the years 2000 and beyond are introduced, such software and systems
will neither fail nor produce incorrect results relating to date or any other
processing. Celtrix has undertaken efforts to confirm that all third parties
with whom it has material relationships, including but not limited to vendors
and customers, will not have material disruptions in their software or systems
related to the year 2000.

                                    SECTION 3

                  REPRESENTATIONS AND WARRANTIES OF PURCHASERS

        Each Purchaser hereby separately represents and warrants, severally and
not jointly, to Celtrix as of the Closing date as follows:

        3.1 INVESTMENT EXPERIENCE. Such Purchaser is an "accredited investor"
as defined in Rule 501(a) under the Securities Act. Purchaser is aware of
Celtrix's business affairs and financial condition and has had access to and has
acquired sufficient information about Celtrix to reach an informed and
knowledgeable decision to acquire the Units (and the Warrant Shares issuable
upon exercise of the Warrants). Purchaser has such business and financial
experience as is required to give it the capacity to protect its own interests
in connection with the purchase of the Units.


                                      -9-

<PAGE>   14

        3.2 INVESTMENT INTENT. Purchaser is purchasing the Units (and the
Warrant Shares upon exercise of the Warrants) for investment for its own account
only and not with a view to, or for resale in connection with, any
"distribution" thereof within the meaning of the Securities Act. Purchaser
understands that the Shares, the Warrants and the Warrant Shares have not been
registered under the Securities Act or registered or qualified under any state
securities law in reliance on specific exemptions therefrom, which exemptions
may depend upon, among other things, the bona fide nature of Purchaser's
investment intent as expressed herein.

        3.3 REGISTRATION OR EXEMPTION REQUIREMENTS. Purchaser further
acknowledges and understands that the Shares, the Warrants and the Warrant
Shares must be held indefinitely unless they are subsequently registered under
the Securities Act or an exemption from such registration is available.
Purchaser understands that the certificate(s) evidencing the Shares will be
imprinted with a legend that prohibits the transfer of the Shares unless (i)
they are registered or such registration is not required, and (ii) if the
transfer is pursuant to an exemption from registration other than Rule 144 under
the Securities Act, and, if Celtrix shall so request in writing, an opinion of
counsel satisfactory to Celtrix is obtained to the effect that the transaction
is so exempt. In addition, Purchaser will refrain from selling, transferring or
otherwise disposing of any Shares, the Warrants or the Warrant Shares, or any
interest therein, unless the same are registered under the Securities Act or
applicable state securities or blue sky laws, or an exemption therefrom is
applicable.

        3.4 NO LEGAL, TAX OR INVESTMENT ADVICE. Purchaser understands that
nothing in this Agreement or any other materials presented to Purchaser in
connection with the purchase and sale of the Units (and the Warrant Shares
issuable upon exercise of the Warrants) constitutes legal, tax or investment
advice. Purchaser has consulted such legal, tax and investment advisors as it,
in its sole discretion, has deemed necessary or appropriate in connection with
its purchase of the Units (and the Warrant Shares issuable upon exercise of the
Warrants).

                                    SECTION 4

                     CONDITIONS TO OBLIGATIONS OF PURCHASERS

        Each Purchaser's obligation to purchase the Units at the Closing is
subject to the fulfillment on or prior to the Closing Date of the following
conditions, unless otherwise waived by such Purchaser:

        4.1 REPRESENTATIONS AND WARRANTIES CORRECT. The representations and
warranties made by Celtrix in Section 2 hereof shall be true and correct when
made, and shall be true and correct on the Closing Date with the same force and
effect as if they had been made on and as of said date.

        4.2 COVENANTS. All covenants, agreements and conditions contained in
this Agreement to be performed by Celtrix on or prior to the Closing Date shall
have been performed or complied with in all material respects.

                                      -10-
<PAGE>   15

        4.3 OPINION OF COMPANY'S COUNSEL. Purchaser shall have received from
Venture Law Group, counsel to Celtrix, an opinion addressed to it, dated the
Closing Date, in form and substance satisfactory to Purchaser.

        4.4 NO ORDER PENDING. There shall not then be in effect any order
enjoining or restraining the transactions contemplated by this Agreement.

        4.5 NO LAW PROHIBITING OR RESTRICTING SUCH SALE. There shall not be
in effect any law, rule or regulation prohibiting or restricting such sale, or
requiring any consent or approval of any person which shall not have been
obtained to issue the Units (except as otherwise provided in this Agreement).

        4.6 COMPLIANCE CERTIFICATE. Celtrix shall have delivered to
Purchasers a certificate executed on behalf of Celtrix by a duly authorized
officer of Celtrix, dated the Closing Date, and certifying to the fulfillment of
the conditions specified in Sections 4.1 and 4.2. Notwithstanding the preceding
sentence, Celtrix shall not be required to deliver such a certificate if the
Closing Date and the execution date of this Agreement are the same.

        4.7 NO MATERIAL ADVERSE CHANGE. There shall have been no material
adverse change between the date of this Agreement and the Closing Date in the
financial condition, business or affairs of Celtrix.

        4.8 GOVERNMENTAL APPROVALS. All consents from governmental agencies
required to consummate the transaction contemplated hereby shall have been
obtained.

        4.9 CLOSING BID PRICE OF CELTRIX COMMON STOCK. The closing bid price
of Celtrix Common Stock as reported on the Nasdaq National Market on the trading
day preceding the Closing Date shall not be less than $0.4375 per share. Any
Purchaser who elects not to proceed with the transaction due to such condition
not being complied with will have no further obligation or liability to Celtrix
arising from or related to this Agreement.

        4.10 DELIVERIES. Purchasers shall receive from Celtrix (i)
certificates of Good Standing for Celtrix issued by the Secretaries of State of
the States of Delaware, California, and all other jurisdictions in which Celtrix
is required to be authorized to conduct business as a foreign corporation; (ii)
a copy of the resolutions of the Board of Directors of Celtrix authorizing the
execution, delivery and performance of this Agreement, the Warrant and the
transactions contemplated hereby and thereby certified by the Secretary of
Celtrix as being true and correct copies of such resolutions and in full force
and effect as of the date of the Closing; (iii) stock certificates evidencing
the shares of Celtrix Common Stock purchased hereunder and (iv) the Warrant.


                                      -11-

<PAGE>   16

                                    SECTION 5

                      CONDITIONS TO OBLIGATIONS OF CELTRIX

        Celtrix's obligation to sell and issue the Units at the Closing is
subject to the fulfillment on or prior to the Closing Date of the following
conditions by each of the Purchasers, unless otherwise waived by Celtrix:

        5.1 REPRESENTATIONS AND WARRANTIES CORRECT. The representations and
warranties made by each Purchaser in Section 3 hereof shall be true and correct
in all material respects when made, and shall be true and correct in all
material respects on the Closing Date with the same force and effect as if they
had been made on and as of said date.

        5.2 COVENANTS. All covenants, agreements and conditions contained in
this Agreement to be performed by each Purchaser on or prior to the Closing Date
shall have been performed or complied with in all material respects.

        5.3 NO ORDER PENDING. There shall not then be in effect any order
enjoining or restraining the transactions contemplated by this Agreement.

        5.4 NO LAW PROHIBITING OR RESTRICTING SUCH SALE. There shall not be in
effect any law, rule or regulation prohibiting or restricting such sale, or
requiring any consent or approval of any person which shall not have been
obtained to issue the Units (except as otherwise provided in this Agreement).

        5.5 GOVERNMENTAL APPROVALS. All consents from governmental agencies
required to consummate the transaction contemplated hereby shall have been
obtained.

                                    SECTION 6

                              COVENANTS OF CELTRIX

        Until the termination of this Agreement in accordance with Section 9.1
hereof or the particular covenant, as the case may be:

        6.1 WARRANTS. Celtrix will comply with the provisions of the Warrants
contained in the Form of Warrant attached as Exhibit B hereto.

        6.2    REGISTRATION REQUIREMENTS.

               (a) As soon as reasonably practicable and in any event no later
than 30 days after the Closing, Celtrix shall prepare and file a registration
statement ("Registration Statement") with the SEC under the Securities Act to
register the resale of the Shares and the Warrant Shares ( "Registrable
Securities") and thereafter shall use its best efforts to secure the
effectiveness of such registration statement, such effectiveness to be declared
no later than 90 days after the Closing. In the event that Celtrix fails to file
the Registration Statement with the SEC within 30 days after the Closing or the
SEC does not declare the Registration Statement

                                      -12-
<PAGE>   17

effective within 90 days after the Closing, then Celtrix will pay to the
Purchasers by wire transfer or certified check or cashier's check sent to the
Purchasers' designated account or representative, as the case may be, an amount
equal to 2% of the aggregate Purchase Price hereunder for each month that the
effectiveness of the Registration Statement is delayed. Such amount, however,
shall be pro-rated for any month in which the Registration Statement is declared
effective.

               (b) Celtrix shall pay all Registration Expenses (as defined
below) in connection with any registration, qualification or compliance
hereunder, and each holder of Registrable Securities ("Holder") shall pay all
Selling Expenses (as defined below) and other expenses that are not Registration
Expenses relating to the Registrable Securities resold by such Holder.
"Registration Expenses" shall mean all expenses, except for Selling Expenses,
incurred by Celtrix in complying with the registration provisions herein
described, including, without limitation, all registration, qualification and
filing fees, printing expenses, escrow fees, fees and disbursements of counsel
for Celtrix, blue sky fees and expenses and the expense of any special audits
incident to or required by any such registration. "Selling Expenses" shall mean
all selling commissions, underwriting fees and stock transfer taxes applicable
to the Registrable Securities and all fees and disbursements of counsel for any
Holder.

               (c) In the case of any registration effected by Celtrix pursuant
to these registration provisions, Celtrix will use its best efforts to: (i) keep
such registration effective until the earlier of (A) two (2) years after the
Closing Date or (B) such date as Celtrix shall be satisfied that the
then-current Holders may sell all of their Registrable Securities then
outstanding within a three (3) month period; (ii) prepare and file with the SEC
such amendments and supplements to such Registration Statement and the
prospectus used in connection with such Registration Statement as may be
necessary to comply with the provisions of the Securities Act with respect to
the disposition of all securities covered by such Registration Statement; (iii)
furnish such number of prospectuses and other documents incident thereto,
including any amendment of or supplement to the prospectus, as a Holder from
time to time may reasonably request; (iv) use its best efforts to register and
qualify the securities covered by such registration statement under such other
securities or Blue Sky laws of such jurisdictions as shall be reasonably
requested by the Holders, provided that Celtrix shall not be required in
connection therewith or as a condition thereto to qualify to do business or to
file a general consent to service of process in any such states or
jurisdictions; (v) cause all such Registrable Securities registered as described
herein to be listed on each securities exchange and quoted on each quotation
service on which similar securities issued by Celtrix are then listed or quoted;
(vi) provide a transfer agent and registrar for all Registrable Securities
registered pursuant to such Registration Statement and a CUSIP number for all
Registrable Securities; and (vii) otherwise use its best efforts to comply with
all applicable rules and regulations of the SEC, and make available to its
security holders, as soon as reasonably practicable, an earnings statement
covering the period of at least twelve months, but not more than eighteen
months, beginning with the first month after the effective date of the
registration statement, which earnings statement shall satisfy the provisions of
Section 11(a) of the Securities Act.

               (d) When a Holder is entitled to sell and gives notice of its
intent to sell pursuant to the Registration Statement, Celtrix shall, within
three (3) trading days (subject to

                                      -13-
<PAGE>   18

Section 7.1), furnish to such Holder a reasonable number of copies of a
supplement to or an amendment of such prospectus as may be necessary so that, as
thereafter delivered to the Holders of such shares, such prospectus shall not
include an untrue statement of a material fact or omit to state a material fact
required to be stated therein or necessary to make the statements therein not
misleading or incomplete in the light of the circumstances then existing.

               (e) The right to sell Registrable Securities pursuant to the
Registration Statement described herein will automatically be assigned to each
transferee of Registrable Securities. In the event that it is necessary, in
order to permit a Holder to sell Registrable Securities pursuant to Celtrix's
Registration Statement, to amend the Registration Statement to name such Holder,
such Holder shall, upon written notice to Celtrix, be entitled to have Celtrix
make such amendment as soon as reasonably practicable. Notwithstanding the above
provisions relating to Registration Expenses, in the event that such an
amendment is requested, the Holder shall, at the request of Celtrix, be
obligated to reimburse Celtrix for reasonable Registration Expenses incurred by
it in connection with such amendment.

               (f) With a view to making available to the holders the benefits
of Rule 144 promulgated under the Securities Act and any other rule or
regulation of the SEC that may at any time permit a Holder to sell Registrable
Securities to the public without registration or pursuant to a registration on
Form S-3, Celtrix hereby covenants and agrees to: (i) make and keep public
information available, as those terms are understood and defined in Rule 144, at
all times after the closing; (ii) file with the SEC in a timely manner all
reports and other documents required of Celtrix under the Securities Act and
Exchange Act; and (iii) furnish to any Holder, as long as the Holder owns any
Registrable Securities forthwith upon request, (A) a written statement by
Celtrix that it has complied with the reporting requirements of Rule 144, the
Securities Act and the Exchange Act, (B) a copy of the most recent annual or
quarterly report of Celtrix, and (C) such other information as may be reasonably
requested in order to avail any Holder of any rule or regulation of the SEC that
permits the selling of any such Registrable Securities without registration or
pursuant to such Form S-3.

               (g) INDEMNIFICATION.

                        (i) To the extent permitted by law, Celtrix will
indemnify and hold harmless each Holder, any underwriter (as defined in the Act)
for such Holder, its officers, directors, shareholders or partners and each
person, if any, who controls such Holder or underwriter within the meaning of
the Act or the Securities Exchange Act of 1934, as amended (the "Exchange Act"),
against any losses, claims, damages, or liabilities (joint or several) to which
they may become subject under the Act, the Exchange Act or other federal or
state law, insofar as such losses, claims, damages, or liabilities (or actions
in respect thereof) arise out of or are based upon any of the following
statements, omissions or violations (collectively a "Violation"): (A) any untrue
statement or alleged untrue statement of a material fact contained in such
Registration Statement, including any preliminary prospectus or final prospectus
contained therein or any amendments or supplements thereto, (B) the omission or
alleged omission to state therein a material fact required to be stated therein,
or necessary to make the statements therein not misleading, or (C) any violation
or alleged violation by Celtrix of the Act, the Exchange Act,

                                      -14-


<PAGE>   19


any state securities law or any rule or regulation promulgated under the Act,
the Exchange Act or any state securities law; and Celtrix will pay to each such
Holder, underwriter or controlling person, as incurred, any legal or other
expenses reasonably incurred by them in connection with investigating or
defending any such loss, claim, damage, liability, or action; provided, however,
that the indemnity agreement contained in this Section 6.2(g)(i) shall not apply
to amounts paid in settlement of any such loss, claim, damage, liability, or
action if such settlement is effected without the consent of Celtrix (which
consent shall not be unreasonably withheld), nor shall Celtrix be liable in any
such case for any such loss, claim, damage, liability, or action to the extent
that it arises out of or is based upon a Violation which occurs in reliance upon
and in conformity with written information furnished expressly for use in
connection with such registration by any such Holder, underwriter or controlling
person.

                      (ii) To the extent permitted by law, each selling Holder
will indemnify and hold harmless Celtrix, each of its directors, each of its
officers who has signed the Registration Statement, each person, if any, who
controls Celtrix within the meaning of the Act, any underwriter, any other
Holder selling securities in such Registration Statement and any controlling
person of any such underwriter or other Holder, against any losses, claims,
damages, or liabilities (joint or several) to which any of the foregoing persons
may become subject, under the Act, the Exchange Act or other federal or state
law, insofar as such losses, claims, damages, or liabilities (or actions in
respect thereto) arise out of or are based upon any Violation, in each case to
the extent (and only to the extent) that such Violation occurs in reliance upon
and in conformity with written information furnished by such Holder expressly
for use in connection with such registration; and each such Holder will pay, as
incurred, any legal or other expenses reasonably incurred by any person intended
to be indemnified pursuant to this subsection 6.2(g)(ii), in connection with
investigating or defending any such loss, claim, damage, liability, or action;
provided, however, that the indemnity agreement contained in this subsection
6.2(g)(ii) shall not apply to amounts paid in settlement of any such loss,
claim, damage, liability or action if such settlement is effected without the
consent of the Holder, which consent shall not be unreasonably withheld;
provided, that, in no event shall any indemnity under this subsection 6.2(g)(ii)
exceed the net proceeds from the offering received by such Holder, except in the
case of willful fraud by such Holder.

                      (iii) Promptly after receipt by an indemnified party under
this Section 6.2(g) of notice of the commencement of any action (including any
governmental action), such indemnified party will, if a claim in respect thereof
is to be made against any indemnifying party under this Section 6.2(g), deliver
to the indemnifying party a written notice of the commencement thereof and the
indemnifying party shall have the right to participate in, and, to the extent
the indemnifying party so desires, jointly with any other indemnifying party
similarly noticed, to assume the defense thereof with counsel mutually
satisfactory to the parties; provided, however, that an indemnified party
(together with all other indemnified parties which may be represented without
conflict by one counsel) shall have the right to retain one separate counsel,
with the reasonable fees and expenses to be paid by the indemnifying party, if
representation of such indemnified party by the counsel retained by the
indemnifying party would be inappropriate due to actual or potential differing
interests between such indemnified party and any other party represented by such
counsel in such proceeding. The failure to deliver

                                      -15-


<PAGE>   20

written notice to the indemnifying party within a reasonable time of the
commencement of any such action, if prejudicial to its ability to defend such
action, shall relieve such indemnifying party of any liability to the
indemnified party under this Section 6.2(g), but the omission so to deliver
written notice to the indemnifying party will not relieve it of any liability
that it may have to any indemnified party otherwise than under this Section
6.2(g).

                      (iv) If the indemnification provided for in this Section
6.2(g) is held by a court of competent jurisdiction to be unavailable to an
indemnified party with respect to any loss, liability, claim, damage, or expense
referred to therein, then the indemnifying party, in lieu of indemnifying such
indemnified party hereunder, shall contribute to the amount paid or payable by
such indemnified party as a result of such loss, liability, claim, damage, or
expense in such proportion as is appropriate to reflect the relative fault of
the indemnifying party on the one hand and of the indemnified party on the other
in connection with the statements or omissions that resulted in such loss,
liability, claim, damage, or expense as well as any other relevant equitable
considerations; provided, that, in no event shall any contribution by a Holder
under this subsection 6.2(g)(iv) exceed the net proceeds from the offering
received by such Holder, except in the case of willful fraud by such Holder. The
relative fault of the indemnifying party and of the indemnified party shall be
determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission to state a material fact
relates to information supplied by the indemnifying party or by the indemnified
party and the parties' relative intent, knowledge, access to information, and
opportunity to correct or prevent such statement or omission.

                      (v) The obligations of Celtrix and Holders under this
Section 6.2(g) shall survive the completion of any offering of Registrable
Securities in a Registration Statement under this Section 6.2(g), and otherwise.

        6.3 FINANCIAL INFORMATION. Until such time as the Purchasers hold
collectively less than 10% of the outstanding voting stock of Celtrix, Celtrix
shall deliver to the Purchasers' designated representative, BioAsia Investments,
LLC (Frank Kung, General Partner) (the "Purchasers' Representative" or
"BioAsia") within thirty (30) days after the end of each month, (a) a balance
sheet of Celtrix as of the end of such month and (b) a statement of income of
the Company as of the end of such month. All such financial statements to be
delivered under this Section shall be in accordance with the books and records
of Celtrix and shall have been prepared in accordance with generally accepted
accounting principles, except that such monthly financial statements may be
subject to normally recurring year-end adjustments and may delete any notes.

        6.4 BUDGET. Attached hereto as Exhibit D is a copy of Celtrix's
Operating Plan for its current fiscal year as previously provided to Purchaser,
including its budget for the year. Celtrix agrees that it will not materially
deviate from the terms outlined in such Operating Plan unless approved by
unanimous consent of its Board of Directors. Furthermore, Celtrix shall afford
Purchasers' Representative the opportunity to discuss its views on such proposed
deviation with the Celtrix Board of Directors prior to implementing the proposed
deviation. Additionally, before the end of each fiscal year of Celtrix, Celtrix
shall deliver to Purchasers' Representative a

                                      -16-

<PAGE>   21

budget for such fiscal year, including projected balance sheets and statements
of income of Celtrix for each quarter of such fiscal year.

        6.5 ACCESS. Celtrix shall allow Purchasers' Representative, upon
reasonable prior notice and during regular business hours no more than once per
quarter (a) full and free access to all books, records and properties of
Celtrix, for any reasonable purpose relating to Purchasers investment in Celtrix
and (b) the opportunity to interview the directors, officers and key employees
of Celtrix regarding the affairs of Celtrix.

        6.6 BOARD OF DIRECTORS. Celtrix shall deliver to Purchasers'
Representative prior written notice of all meetings of the Board of Directors at
the same time such notices are distributed to the Directors and a copy of the
package distributed to the Directors in connection with the meeting. Purchasers
may designate a single representative to attend meetings of Celtrix's Board of
Directors as a non-voting observer.

        6.7 PROCEEDINGS. Promptly after obtaining knowledge thereof, Celtrix
shall notify each Purchaser of (a) the commencement of any material action,
suit, claim, investigation or other proceeding by or before any court,
governmental authority or arbitrator against Celtrix, (b) any material judgment,
decree, injunction, or order of any court, governmental authority or arbitrator
entered against, or any settlement agreement entered into by, Celtrix.

        6.8 INSURANCE. Celtrix shall maintain such insurance with coverage and
in amounts as shall be customary for Celtrix's industry and reasonable in light
of the Celtrix's financial condition and stage of business development,
including without limitation liability and extended coverage insurance and
workers' compensation insurance.

        6.9 PROPRIETARY INFORMATION AGREEMENTS. All employees and consultants of
Celtrix who have access to confidential information as part of their employment
or engagement have already executed or shall be required to execute and deliver
a Proprietary Information Agreement in such form as may be approved by the Board
of Directors of the Company.

        6.10 TAXES AND OTHER LIABILITIES. Celtrix shall make reasonable efforts
to pay and discharge, before the same become delinquent and before penalties
accrue thereon (all subject to the disclosures concerning taxes contained
elsewhere in this Agreement), all taxes, assessments and governmental charges
upon or against it or any of its properties, and all its other material
liabilities at any time existing, except to the extent and so long as (a) the
same are being contested in good faith and by appropriate proceedings in such
manner as not to cause any materially adverse effect upon the financial
condition of Celtrix or the loss of any right of redemption from any sale
thereunder; and (b) Celtrix shall have set aside on its books adequate reserves
(segregated to the extent required by generally accepted accounting principles)
with respect thereto, all subject to decisions of the Board of Directors
otherwise and/or to the financial condition of Celtrix and the business judgment
of management at the relevant point in time.

        6.11 CORPORATE EXISTENCE. Celtrix shall use best efforts to maintain its
corporate existence, assets and foreign qualifications in all necessary
jurisdictions at all necessary points in time.


                                      -17-

<PAGE>   22

        6.12 BUSINESS. Celtrix shall not change its current line of business, or
enter into any line of business other than its current line of business, or make
any material change in its current line of business, except as shall be approved
by its Board of Directors. Furthermore, Celtrix shall afford Purchaser's
Representative the opportunity to discuss its views on such proposed change with
the Celtrix Board of Directors prior to implementing the proposed change.

        6.13 COMPLIANCE WITH LAWS. Celtrix shall comply with all material laws
and regulations applicable to it in all material respects.

        6.14 INDEMNIFICATION.

               (a) Celtrix shall indemnify and hold Purchasers and their
respective partners, stockholders, directors, officers and employees
(collectively, the "Indemnified Parties") harmless from and against, and agree
to promptly defend each of the Indemnified Parties from and reimburse each of
the Indemnified Parties for, any and all losses, damages, costs, expenses,
liabilities, obligations and claims of any kind (including, without limitation,
reasonable attorney fees (collectively, a "Loss") that any of the Indemnified
Parties may at any time suffer or incur, or become subject to, as a result or in
connection with:

                        (i) any breach or inaccuracy of any representations and
warranties made by Celtrix in this Agreement, or in any certificate or affidavit
delivered by Celtrix at the Closing in accordance with the provisions hereof;

                        (ii) any failure by Celtrix to fulfill its obligations
hereunder or under the Warrant; and

                        (iii) any suit, action or other proceeding arising out
of, or in any way related to, any of the matters referred to in this Section
6.14.

               (b) An Indemnified Party shall notify Celtrix in writing of any
claim or demand (a "Claim") that the Indemnified Party has determined has given
or could give rise to a right of indemnification under this Agreement. Subject
to Celtrix's right to defend in good faith third party claims as hereinafter
provided, Celtrix shall satisfy its obligations under this Section 6.14 within
60 days after the receipt of written notice thereof from the Indemnified Party.

               (c) If the Indemnified Party shall notify Celtrix of any Claim
pursuant to Section 6.14(a) hereof, and if such Claim relates to a Claim
asserted by a third party against the Indemnified Party that Celtrix
acknowledges is a Claim for which it must indemnify or hold harmless the
Indemnified Party under Section 6.14(a), Celtrix shall have the right, at its
sole cost and expense, to employ counsel of its own choosing reasonably
satisfactory to the Indemnified Party to defend any such Claim asserted against
the Indemnified Party; provided, however, that if the Indemnified Party (i)
reasonably believes that its interests with respect to a Claim (or any material
portion thereof) are in conflict with the interests of Celtrix with respect to
such Claim (or portion thereof), and (ii) promptly notifies Celtrix, in writing,
of the nature of such conflict, then, subject to the provisions of the following
sentence, the Indemnified Party shall be entitled to choose, at the sole cost
and expense of Celtrix, independent counsel to defend such Claim. In

                                      -18-


<PAGE>   23

the event that Celtrix does not agree that the Indemnified Party's interests
with respect to any such Claim are in conflict with the interests of Celtrix,
Celtrix shall so notify the Indemnified Party and the parties agree that they
shall each appoint a representative to meet within ten (10) business days after
Celtrix's notification to the Indemnified Party and such representatives will
discuss the issue and diligently work to resolve their differing views. The
Indemnified Party shall have the right to participate in the defense of any such
Claim at its own expense (except to the extent provided in the foregoing
sentence), but Celtrix shall retain control over such litigation (except as
provided in the foregoing sentence). Celtrix shall notify the Indemnified Party
in writing, as promptly as possible (but in any case before the due date for the
answer or response to a claim) after the date of the notice of claim given by
the Indemnified Party to Celtrix under section 6.14(b) hereof of its election to
defend in good faith any such third party Claim. So long as Celtrix is defending
in good faith any such Claim asserted by a third party against the Indemnified
Party, the Indemnified Party shall not settle or compromise such Claim without
the prior written consent of Celtrix. The Indemnified Party shall cooperate with
Celtrix in connection with any such defense and shall make available to Celtrix
or its agents all records and other materials in the Indemnified Party's
possession reasonably required by it for its use in contesting any third party
Claim; provided, however, that Celtrix shall have agreed, in writing, to keep
such records and other materials confidential except to the extent required for
defense of the relevant Claim. Whether or not Celtrix elects to defend any such
Claim, the Indemnified Party shall have no obligation to do so.

        6.15 MATERIAL EVENTS. If the Purchasers' Representative is absent from
any meeting of the Board of Directors at which any of the following events is
announced, discussed or approved, Celtrix shall promptly notify Purchaser's
Representative of the same: (a) the execution of any material agreement to which
Celtrix is a party, (b) the termination of any material agreement to which
Celtrix is a party, (c) the resignation, termination or hiring of any key
employee or any material restructuring of Celtrix's labor force, (d) any
material labor dispute, (e) any material developments related to Celtrix's
intellectual property, (f) the occurrence of any other event that would have a
material effect upon Celtrix and/or its business, operations, prospects or
financial condition, and (g) any issuance of Celtrix Common Stock, Preferred
Stock, securities convertible into Celtrix Common Stock or Preferred Stock, or
the granting of any rights to acquire the same.

        6.16 STOCKHOLDER RATIFICATION. Celtrix agrees that in connection with
its next annual meeting of stockholders (or in connection with any special
meeting of stockholders that may occur prior to such annual meeting date), it
shall solicit stockholder ratification of this Agreement and of the transactions
contemplated hereunder.

                                    SECTION 7

                             COVENANTS OF PURCHASERS

        7.1 NOTICE TO COMPANY OF PROPOSED SALE AND RIGHT OF COMPANY TO SUSPEND
USE OF REGISTRATION STATEMENT. If any Purchaser (as defined in Section 6.2
above) shall propose to sell any Registrable Securities pursuant to the
Registration Statement, it shall notify Celtrix of its intent to do so at least
three (3) full trading days prior to such sale, and the provision of such


                                      -19-
<PAGE>   24

notice to Celtrix shall conclusively be deemed to establish an agreement by such
Purchaser to comply with the registration provisions herein described. Unless
otherwise specified in such notice, such notice shall be deemed to constitute a
representation that any information previously supplied by such Purchaser is
accurate as of the date of such notice. At any time within such three (3)
trading-day period, Celtrix may refuse to permit the Purchaser to resell any
Registrable Securities pursuant to the Registration Statement; provided,
however, that in order to exercise this right, Celtrix must deliver a
certificate in writing to the Purchaser to the effect that a delay in such sale
is necessary because a sale pursuant to such Registration Statement in its
then-current form could constitute a violation of the federal securities laws.
In no event shall such delay exceed ten (10) trading days; provided, however,
that if, prior to the expiration of such ten (10) trading day period, Celtrix
delivers a certificate in writing to the Purchaser to the effect that a further
delay in such sale beyond such ten (10) trading day period is necessary because
the disclosures required to be made for a sale pursuant to such Registration
Statement to be in compliance with federal securities laws would be seriously
detrimental to Celtrix and its stockholders, Celtrix may refuse to permit such
Purchaser to resell any Registrable Securities pursuant to the registration
statement for an additional period not to exceed ten (10) trading days. Celtrix
may not utilize this right more than once in any three (3) month period.

        7.2 RESTRICTIONS ON SHORT-SALES. No Purchaser shall engage in any
short-sales of Celtrix's Common Stock prior to the effectiveness of the
Registration Statement, except to the extent that any such short-sale is fully
covered by freely tradable shares of Common Stock of Celtrix.

                                    SECTION 8

    RESTRICTIONS ON TRANSFERABILITY OF SHARES; COMPLIANCE WITH SECURITIES ACT

        8.1 RESTRICTIONS ON TRANSFERABILITY. The Shares, Warrants and Warrant
Shares shall not be transferable in the absence of a registration under the
Securities Act or an exemption therefrom or in the absence of compliance with
any term of this Agreement. Celtrix shall be entitled to give stop transfer
instructions to the transfer agent with respect to the Shares in order to
enforce the foregoing restrictions.

        8.2 RESTRICTIVE LEGEND. Each certificate representing Shares, Warrants
and Warrant Shares shall bear substantially the following legends (in addition
to any legends required under applicable securities laws):

    THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
    AND MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF REGISTRATION UNDER THE
    SECURITIES ACT OF 1933 OR AN EXEMPTION THEREFROM.

    UNTIL __________, 2000 THE SHARES REPRESENTED BY THIS CERTIFICATE MAY NOT BE
    SOLD OR TRANSFERRED UNLESS PRIOR NOTICE SHALL HAVE BEEN GIVEN TO CELTRIX.


                                      -20-

<PAGE>   25

        The legend contained in this Section 8.2 will be removed from a
certificate if (i) Celtrix receives an opinion of counsel reasonably
satisfactory to Celtrix that the Shares or Warrant Shares represented by such
certificates are available for resale pursuant to Rule 144 under the Securities
Act, or (ii) in Celtrix's opinion the Shares or Warrant Shares represented by
such certificates are available for resale pursuant to Rule 144(k) under the
Securities Act, or (iii) such Shares or Warrant Shares are sold pursuant to an
effective registration statement with the SEC.

                                    SECTION 9

                                  MISCELLANEOUS

        9.1 TERMINATION OF AGREEMENT.

               (a) This Agreement may be terminated at any time prior to the
Effective Time by Celtrix or any Purchaser if there has been a material breach
of any representation, warranty, covenant or agreement on the part of the other
party set forth in this agreement, which breach shall not have been cured, in
the case of a representation or warranty, prior to the Closing or, in the case
of a covenant or agreement, within thirty (30) calendar days following receipt
by the breaching party of written notice of such breach from the other party.

               (b) From and after the termination of this Agreement, the
covenants, obligations and agreements of the parties set forth herein shall be
of no further force or effect and the parties shall be under no further
obligation with respect thereto.

        9.2 BEST EFFORTS. Celtrix and each Purchaser shall use its best efforts
to take all actions required under any law, rule or regulation adopted
subsequent to the date hereof in order that Celtrix may sell the Units to
Purchasers and Purchasers may purchase the Units, and to ensure that the
conditions to a Closing set forth herein are satisfied on or before the
scheduled date of such Closing.

        9.3 GOVERNING LAW. This Agreement shall be governed in all respects by
the laws of the State of California as applied to contracts entered into solely
between residents of, and to be performed entirely within, such state.

        9.4 SURVIVAL. The representations and warranties, in Sections 2 and 3 of
this Agreement shall survive any investigation made by any Purchaser or Celtrix
and the Closing; provided that such representations and warranties shall not be
construed so as to constitute representations and warranties concerning
circumstances existing after the date of this Agreement.

        9.5 SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon and
shall inure to the benefit of the parties hereto and their respective successors
and assigns. This Agreement may not be assigned by a party without the prior
written consent of the other party.

        9.6 ENTIRE AGREEMENT; AMENDMENT. This Agreement, the Warrants and the
other documents delivered pursuant hereto constitute the full and entire
understanding and agreement

                                      -21-


<PAGE>   26

between the parties with regard to the subject matter hereof and thereof and
supersedes all prior agreements and understandings among the parties relating to
the subject matter hereof. With the exception of Section 6 hereof, the terms of
this Agreement may be waived or amended with the written consent of Celtrix and
each Purchaser. With respect to Section 6 hereof, with the written consent of
Celtrix and the record holders of more than fifty percent (50%) of the
Registrable Securities then outstanding the terms of this Agreement may be
waived and amended and any such amendment or waiver shall be binding upon
Celtrix and all holders of Shares.

        9.7 NOTICES AND DATES. Any notice or other communication given under
this Agreement shall be sufficient if in writing and sent by registered or
certified mail, domestic or international courier, or facsimile, return receipt
requested, postage or courier charges prepaid, to a party at its address set
forth below (or at such other address as shall be designated for such purpose by
such party in a written notice to the other party hereto):

               (a)    if to Celtrix, to:

                         Celtrix Pharmaceuticals, Inc.
                         3055 Patrick Henry Drive
                         Santa Clara, CA 95052-8203
                         Attention:  Chief Financial Officer

                         with a copy to:

                         Edmund S. Ruffin, Jr.
                         Venture Law Group
                         2800 Sand Hill Road
                         Menlo Park, CA  94025

                  (b)    if to Purchasers, to the respective address set forth
                         on the attached Schedule of Purchasers


                         with a copy to:

                         Ira S. Nordlicht
                         Nordlicht & Hand
                         Olympic Tower
                         645 Fifth Avenue
                         New York, NY  10022

               All such notices and communications shall be effective one (1)
trading day after being sent by courier or by facsimile with confirmation of
receipt or five (5) trading days after being sent by the other approved methods.


                                      -22-

<PAGE>   27

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

        9.9 NO THIRD PARTY RIGHTS. Nothing in this Agreement shall create or be
deemed to create any rights in any person or entity not a party to this
Agreement.

        9.10 COUNTERPARTS. This Agreement may be executed in counterparts, and
each such counterpart shall be deemed an original for all purposes, but such
counterparts shall together constitute one and the same instrument.

        9.11 EXPENSES. Celtrix and each Purchaser shall bear its own expenses
incurred on its behalf with respect to this Agreement and the transactions
contemplated hereby, except that if the Closing occurs, the Company shall
reimburse the Purchasers for documented, itemized and reasonable fees and
expenses incurred by them not to exceed $50,000 in the aggregate.

                            [SIGNATURE PAGE FOLLOWS]


                                      -23-
<PAGE>   28
        IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their respective authorized officers as of the date first above
mentioned.


                                            CELTRIX PHARMACEUTICALS, INC.



                                            By:    /s/ Andreas Sommer
                                                   -----------------------------

                                            Title: President & CEO
                                                   -----------------------------


                                            PURCHASERS


                                            Name:  /s/ Frank Kung
                                                   -----------------------------

                                            By:    Frank Kung
                                                   -----------------------------

                                            Title: General Partner
                                                   -----------------------------
                                                   Biotechnology Development
                                                   Fund, L.P.
                                                   -----------------------------


                                            Name:  /s/ Frank Kung
                                                   -----------------------------

                                            By:    Frank Kung
                                                   -----------------------------

                                            Title: General Partner
                                                   -----------------------------
                                                   Biotechnology Development
                                                   Fund, III L.P.
                                                   -----------------------------


                                            Name:  /s/ Joseph W K Leung
                                                   -----------------------------

                                            By:    For and on behalf of Veron
                                                   International Limited
                                                   (Incorporated in BVI)
                                                   -----------------------------

                                            Title: Director
                                                   -----------------------------


                                            Name:  LEE WEI CHEN
                                                   -----------------------------

                                            By:    /s/ Wei-Chen Lee
                                                   -----------------------------

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


                                            Name:  For and on behalf of
                                                   Lion International Management
                                                   Limited as sole Director of
                                                   Hofung Holdings Limited
                                                   -----------------------------

                                            By:    /s/ [R] Boswell
                                                   -----------------------------

                                            Title: Authorized Signatory
                                                   -----------------------------


                                            Name:  /s/ Jesse Chen
                                                   -----------------------------
                                                   /s/  Wanpyag Chuang
                                                   -----------------------------

                                            By:    Jesse Chen & Wanpyag Chuang
                                                   -----------------------------

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

<PAGE>   29

                                            Name:  /s/ [J] Leung
                                                   -----------------------------

                                            By:    Nai-ping Leung
                                                   -----------------------------

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


                                            Name:  WEN-CHEN YUAN
                                                   -----------------------------

                                            By:    /s/ Wen-Chen Yuan
                                                   -----------------------------

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

<PAGE>   30




                                    EXHIBIT A

                             SCHEDULE OF PURCHASERS


<TABLE>
<CAPTION>

                                             # SHARES         # WARRANT
              PURCHASER                    COMMON STOCK         SHARES           PURCHASE PRICE
              ---------                    ------------       -----------        --------------
<S>                                        <C>                <C>                <C>
Biotechnology Development Fund, L.P.          500,000             750,000          $250,000
Frank Kung, General Partner
575 High Street
Suite 201
Palo Alto, CA  94301

Biotechnology Development Fund, III         1,000,000           1,500,000          $500,000
L.P.
Frank Kung, General Partner
575 High Street
Suite 201
Palo Alto, CA  94301

Veron International, Ltd.                    940,000            1,410,000          $470,000
Chinachem Golden Plaza
77 Mody Road
Tsin Sha Tsui East
Kowloon, Hong Kong
Attn:  W.K. Leung

Lee Wei Chen                                 940,000            1,410,000          $470,000
c/o Fu Sheng Industrial Co., Ltd.
172 Nanking East Road, Sec. 2
Taipei 104, Taiwan
R.O.C.
Attn:  Shubbin King

Hofung Holdings Limited.                     380,000             570,000           $190,000
20 F East Town Bldg.
41 Lockard Rd.
Wanchai, Hong Kong
Attn:  Robert Ho

Wanpyng Chuang and Jesse Chen                100,000             150,000            $50,000
1608 Pebble Beach Ct.
Milpitas, CA  95035

Nai-Ping Leung                                60,000             90,000             $30,000
95A, Hill Road 1/F
Western District
Hong Kong
</TABLE>

<PAGE>   31

<TABLE>
<CAPTION>
<S>                                        <C>                <C>                <C>
Wen-Chen Yuan                                 80,000             120,000            $40,000
8/F 33 One hundred fifty first Avenue
Fourth District
Ren-ai Street
Taipei, R.O.C.

                                          -----------         -----------         ----------
     Total                                  4,000,000           6,000,000         $2,000,000


</TABLE>


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