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                                                                  Exhibit 4.4(b)

                       AMERICAN BIOGENETIC SCIENCES, INC.

                             REGISTRATION AGREEMENT

      THIS AGREEMENT, is made as of March 3, 2000, among AMERICAN BIOGENETIC
SCIENCES, a Delaware corporation (the "Company") and the investors listed on
Exhibit A attached hereto (collectively referred to as the "Investor").

      The parties to this Agreement are parties to a Securities Purchase
Agreement, dated as of February 3, 2000 (the "Purchase Agreement"). In order to
induce the Investor to enter into the Purchase Agreement, the Company has agreed
to provide the registration rights set forth in this Agreement. The execution
and delivery of this Agreement is a condition to the Closing under the Purchase
Agreement. Unless otherwise provided in this Agreement, capitalized terms used
herein shall have the meanings set forth in paragraph 5 hereof.

      The parties hereto agree as follows:

      1. REGISTRATION AFTER CLOSING.

            (a) Within 60 days after the Closing, the Company shall file a
registration statement on the appropriate form, under the Securities Act
covering the Registrable Securities, including a prospectus for the purpose of
offering for resale the Registrable Securities (the "Registration Statement").
The Company shall use its best efforts to cause the Registration Statement to be
declared effective by the Securities and Exchange Commission within 120 days
after the Closing.

            (b) The Company shall use its best efforts to cause the Registration
Statement to remain effective until the first to occur of (i) two years
(excluding any period during which the Registration Statement is suspended
pursuant to Section 2(d)) after the date it is declared effective, (ii) the date
on which all Registrable Securities are sold; and (iii) the date that such share
cease to be treated as Registrable Securities because they are eligible be sold
without delay under Rule 144 under the Securities Act.

      2. REGISTRATION PROCEDURES.

            (a) The Company shall:

                  (1) notify each holder of Registrable Securities of the filing
of the Registration Statement with the Securities and Exchange Commission and of
the effectiveness of the Registration Statement;

                  (2) prepare and file with the Securities and Exchange
Commission such amendments and supplements to the Registration Statement and the
prospectus used in


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connection therewith as may be necessary to keep the Registration Statement
effective for the period set forth in Section 1(b) hereof;

                  (3) comply with the provisions of the Securities Act with
respect to the disposition of all securities covered by the Registration
Statement during such period in accordance with the intended methods of
disposition by the sellers thereof set forth in the Registration Statement;

                  (4) furnish to each seller of Registrable Securities such
number of copies of the Registration Statement, each amendment and supplement
thereto, the prospectus included in the Registration Statement (including each
preliminary prospectus) and such other documents as such seller may reasonably
request in order to facilitate the disposition of the Registrable Securities
owned by such seller;

                  (5) use its best efforts to register or qualify such
Registrable Securities under such other securities or blue sky laws of such
jurisdictions as any seller reasonably requests and do any and all other acts
and things which may be reasonably necessary or advisable to enable such seller
to consummate the disposition in such jurisdictions of the Registrable
Securities owned by such seller (provided that the Company shall not be required
to (i) qualify generally to do business in any jurisdiction where it would not
otherwise be required to qualify but for this subparagraph, (ii) subject itself
to taxation in any such jurisdiction or (iii) consent to general service of
process in any such jurisdiction);

                  (6) notify each seller of such Registrable Securities, at any
time when a prospectus relating thereto is required to be delivered under the
Securities Act, of the happening of any event as a result of which the
prospectus included in the Registration Statement contains an untrue statement
of a material fact or omits any fact necessary to make the statements therein
not misleading, and, subject to the right of the Company to suspend sales under
Section 2(d) below, at the request of any such seller, the Company shall prepare
a supplement or amendment to such prospectus so that, as thereafter delivered to
the purchasers of such Registrable Securities, such prospectus shall not contain
an untrue statement of a material fact or omit to state any fact necessary to
make the statements therein not misleading;

                  (7) use its reasonable efforts to cause all such Registrable
Securities to be listed on the securities exchange on which similar securities
issued by the Company are then listed;

                  (8) provide a transfer agent and registrar for all such
Registrable Securities not later than the effective date of the Registration
Statement;

                  (9) if the Registrable Securities are to be sold in a firm
commitment underwritten offering, enter into a customary underwriting agreement
and take all such other actions as the holders of a majority of the Registrable
Securities being sold or the underwriters reasonably request in order to
expedite or facilitate the disposition of such Registrable Securities;

                  (10) make available for inspection by any seller of
Registrable Securities, any underwriter participating in any disposition
pursuant to the Registration


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Statement, and any attorney, accountant or other agent retained by any such
seller or underwriter, all financial and other records, pertinent corporate
documents and properties of the Company, and cause the Company's officers,
directors, employees and independent accountants to supply all information
reasonably requested by any such seller, underwriter, attorney, accountant or
agent in connection with such registration statement; PROVIDED, HOWEVER, that
any information that is determined in good faith by the Company to be of a
confidential nature at the time of delivery of such information shall be kept
confidential by such persons, unless (i) disclosure of such information is
required by court or administrative order or is necessary to respond to
inquiries of regulatory authorities; (ii) disclosure of such information, in the
opinion of counsel to such person, is required by law; (iii) such information
becomes generally available to the public other than as a result of a disclosure
or failure to safeguard by such person; or (iv) such information becomes
available to such person from a source other than the Company and such source is
not known by such person to be bound by a confidentiality agreement with the
Company;

                  (11) in the event of the issuance of any stop order suspending
the effectiveness of the Registration Statement, or of any order suspending or
preventing the use of any related prospectus or suspending the qualification of
any Common Stock included in the Registration Statement for sale in any
jurisdiction, the Company shall use its reasonable best efforts promptly to
obtain the withdrawal of such order;

                  (12) the Company may require each seller of the Registrable
Securities to furnish to the Company such information regarding the distribution
of such Registrable Securities as is required by law to be disclosed in the
Registration Statement, and the Company may exclude from such registration the
Registrable Securities of any such holder who unreasonably fails to furnish such
information within a reasonable time after receiving such request;

            (b) The holders of any Registrable Securities covenant and agree
that (i) they will not sell any Registrable Securities under the Registration
Statement until they have received copies of the prospectus as then amended or
supplemented as contemplated in Section 4(b) and notice from the Company that
the Registration Statement and any post-effective amendments thereto have become
effective and (ii) each such holder and its officers, directors or Affiliates,
if any, will comply with the prospectus delivery requirements of the Securities
Act as applicable to them in connection with sales of Registrable Securities
pursuant to the Registration Statement.

            (c) Each holder of Registrable Securities agrees by its acquisition
of such Registrable Securities that, upon receipt of a notice from the Company
of the occurrence of any event of the kind described in Subsections 2(a)(6) or
2(a)(11), such holder will forthwith discontinue disposition of such Registrable
Securities until such holder's receipt of the copies of the supplemented
prospectus and/or amended Registration Statement contemplated by Subsection
2(a)(4), or until it is advised in writing by the Company that the use of the
applicable prospectus may be resumed, and, in either case, has received copies
of any additional or supplemental filings that are incorporated or deemed to be
incorporated by reference in such prospectus or Registration Statement.


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            (d) If a event occurs which would otherwise require the filing of an
amendment to the Registration Statement or a prospectus supplement under
Subsection 2(a) (6) above so as permit the proposed sale without a violation of
securities laws, if the in the good faith judgment of the Board of Directors of
the Company, after consultation with counsel, such disclosure would materially
adversely affect a pending or scheduled public offering, or an acquisition,
merger, or similar transaction, or negotiations of either of the foregoing, or
would require the disclosure of another material development prior to the time
it would otherwise be required to be disclosed in a manner adverse to the best
interests of the Company, then it may decline to permit the resale of any
Registrable Securities pursuant to the Registration Statement for up to a
maximum of ninety (90) days, provided that it may not exercise this right more
than twice in any twelve (12) month period. Each Investor hereby covenants and
agrees that it will not sell any Shares pursuant to the Registration Statement
during the periods sales in reliance upon the Registration Statement are
prohibited as set forth in this Section 2(d).

      3. REGISTRATION EXPENSES.

            (a) All expenses incident to the Company's performance of or
compliance with this Agreement, including without limitation all registration
and Securities and Exchange Commission and National Association of Securities
Dealers, Inc. filing fees and expenses, fees and expenses of compliance with
securities or blue sky laws, printing expenses, messenger and delivery expenses,
fees and disbursements of custodians, the expense of any audit of financial data
required to be included in the Registration Statement, and fees and
disbursements of counsel for the Company and fees and disbursements of not more
than one counsel to the holders of Registrable Securities up to a maximum of
$5,000 and fees and disbursements of all independent certified public
accountants, and other persons retained by the Company (all such expenses being
herein called "Registration Expenses"), shall be borne by the Company; PROVIDED,
HOWEVER, that the Company shall have no obligation to pay or otherwise bear any
portion of (i) the underwriter's commissions or discounts or transfer taxes
attributable to the Registrable Securities being offered and sold by the holders
of such Registrable Securities, or (ii) the fees and expenses of advisors,
professionals or agents for the holders of Registrable Securities in connection
with the registration of Registrable Securities (other than as above provided),
or (iii) the fees and expenses of any counsel or accounting firm retained by the
underwriters in connection with an underwritten offering of the Registrable
Securities and the costs of any determination (but not filing) by the
underwriters of the eligibility of the Registrable Securities for investment
under the applicable state securities law.

            (b) To the extent Registration Expenses are not required to be paid
by the Company, each holder of securities included in any registration hereunder
shall pay those Registration Expenses allocable to the registration of such
holder's securities so included, and any Registration Expenses not so allocable
shall be borne pro rata by all sellers of securities included in such
registration in proportion to the aggregate selling price of the securities to
be so registered.

      4. INDEMNIFICATION.

            (a) The Company agrees to indemnify and hold harmless, to the extent
permitted by law, each holder of Registrable Securities, its officers and
directors and each person


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who controls such holder (within the meaning of the Securities Act or the
Exchange Act) (each, an "Indemnitee") against any loss, claim, damage, liability
or expense, as incurred, to which such Indemnitee may be subject under the
Securities Act, the Exchange Act, or other federal or state statutory law or
regulation, at common law or otherwise (including in settlement of any
litigation, if such settlement is effected with the written consent of the
Company, which consent shall not be unreasonably withheld), insofar as such
loss, claim, damage, liability or expense (or action in respect thereof) arises
out of or is based (i) upon any untrue or alleged untrue statement of material
fact contained in any registration statement, prospectus or preliminary
prospectus or any amendment thereto (including any information deemed to be part
thereof pursuant to Rule 430A of the Securities Act) or supplement thereto or
any omission or alleged omission of a material fact required to be stated
therein or necessary to make the statements therein not misleading; or (ii), in
whole or in part upon any failure of the Company or any controlling person to
the Company to perform its obligations hereunder, in each case except insofar as
the same are caused by or contained in any information furnished to the Company
by such holder expressly for use therein or by such holder's failure to deliver
a copy of the registration statement or prospectus or any amendments or
supplements thereto after the Company has furnished such holder with copies of
the same. In connection with an underwritten offering, the Company shall
indemnify such underwriters, their officers and directors and each person who
controls such underwriters (within the meaning of the Securities Act or the
Exchange Act) to the same extent as provided above with respect to the
indemnification of the holders of Registrable Securities.

            (b) In connection with the Registration Statement in which a holder
of Registrable Securities is participating, each such holder shall furnish to
the Company in writing such information and affidavits as the Company reasonably
requests for use in connection with any the Registration Statement or prospectus
and, to the extent permitted by law, shall indemnify the Company, its directors,
officers, agents and employees and each person who controls the Company (within
the meaning of the Securities Act) and the directors, officers, agents and
employees of such controlling persons against any losses, claims, damages,
liabilities and expenses resulting from any untrue or alleged untrue statement
of material fact contained in the Registration Statement, prospectus or
preliminary prospectus or any amendment thereof or supplement thereto or any
omission or alleged omission of a material fact required to be stated therein or
necessary to make the statements therein not misleading, but only to the extent
that such untrue statement or omission is contained in any information or
affidavit so furnished by such holder; provided that the obligation to indemnify
shall be individual, not joint and several, for each holder and shall be limited
to the amount of proceeds received by such holder from the sale of Registrable
Securities pursuant to the Registration Statement.

            (c) Any person entitled to indemnification hereunder shall (i) give
prompt written notice to the indemnifying party of any claim with respect to
which it seeks indemnification (provided that the failure to give prompt notice
shall not impair any such person's right to indemnification hereunder to the
extent such failure has not prejudiced the indemnifying party) and (ii) unless
in such indemnified party's reasonable judgment a conflict of interest between
such indemnified and indemnifying parties may exist with respect to such claim,
permit such indemnifying party to assume the defense of such claim with counsel
reasonably satisfactory to the indemnified party. If such defense is assumed,
the indemnifying party shall not be subject to any liability for any settlement
made by the indemnified party without its consent


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(but such consent shall not be unreasonably withheld). An indemnifying party who
is not entitled to, or elects not to, assume the defense of a claim shall not be
obligated to pay the fees and expenses for more than one counsel for all parties
indemnified by such indemnifying party with respect to such claim or related
claims.

            (d) The indemnification provided for under this Agreement shall
remain in full force and effect regardless of any investigation made by or on
behalf of the indemnified party or any officer, director or controlling person
of such indemnified party and shall survive the transfer of securities. The
parties also agree to make such provisions as are reasonably requested by any
indemnified party in the event that indemnification hereunder is unavailable for
any reason.

      5. DEFINITIONS.

            (a) "REGISTRABLE SECURITIES" means (i) any Class A Common Stock, par
value $.001 per share ("Common Stock"), of the Company (x) to be issued upon the
conversion of the Series A Convertible Preferred Stock, $.001 par value per
share ("Preferred Stock"), of the Company acquired by the Investor pursuant to
the Purchase Agreement or (y)otherwise issued pursuant to Section 1.3(b) of the
Purchase Agreement, (ii) any Common Stock issued upon exercise of the Warrants
acquired by the Investor pursuant to the Purchase Agreement; and (iii) any
Common Stock issued or issuable with respect to the securities referred to in
clauses (i) and (ii) by way of a stock dividend or stock split or in connection
with a combination of shares, recapitalization, merger, consolidation or other
reorganization. As to any particular Registrable Securities, such securities
shall cease to be Registrable Securities when they have been distributed to the
public pursuant to an offering registered under the Securities Act or sold to
the public through a broker or dealer or to a market maker in compliance with
Rule 144 under the Securities Act (or any similar rule then in force) or
repurchased by the Company or any Subsidiary, or when they are eligible to be
sold in compliance with Rule 144 under the Securities Act. For purposes of this
Agreement, a person shall be deemed to be a holder of Registrable Securities,
and the Registrable Securities shall be deemed to be in existence, whenever such
person has the right to acquire directly or indirectly such Registrable
Securities (upon conversion or exercise in connection with a transfer of
securities or otherwise), whether or not such acquisition has actually been
effected, and such person shall be entitled to exercise the rights of a holder
of Registrable Securities hereunder.

            (b) Unless otherwise stated, other capitalized terms contained
herein have the meanings set forth in the Purchase Agreement.

      6. MISCELLANEOUS.

            (a) NO INCONSISTENT AGREEMENTS. The Company shall not hereafter
enter into any agreement with respect to its securities which is inconsistent
with or violates the rights granted to the holders of Registrable Securities in
this Agreement.

            (b) NO ADVERSE ACTION. The Company shall not take any action, or
permit any change to occur, with respect to its securities which would adversely
affect the ability


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of the holders of Registrable Securities to include such Registrable Securities
in the registration undertaken pursuant to this Agreement.

            (c) REMEDIES. Any person having rights under any provision of this
Agreement shall be entitled to enforce such rights specifically to recover
damages caused by reason of any breach of any provision of this Agreement and to
exercise all other rights granted by law. The parties hereto agree and
acknowledge that money damages may not be an adequate remedy for any breach of
the provisions of this Agreement and that any party may in its sole discretion
apply to any court of law or equity of competent jurisdiction (without posting
any bond or other security) for specific performance and for other injunctive
relief in order to enforce or prevent violation of the provisions of this
Agreement.

            (d) AMENDMENTS AND WAIVERS. Except as otherwise provided herein, the
provisions of this Agreement may be amended or waived only upon the prior
written consent of the Company and Investors.

            (e) SUCCESSORS AND ASSIGNS. All covenants and agreements in this
Agreement by or on behalf of any of the parties hereto shall bind and inure to
the benefit of the respective successors and assigns of the parties hereto
whether so expressed or not. In addition, whether or not any express assignment
has been made, the provisions of this Agreement which are for the benefit of
purchasers or holders of Registrable Securities are also for the benefit of, and
enforceable by, any subsequent holder of Registrable Securities who is an
affiliate of the Investor.

            (f) INCORPORATION OF PURCHASE AGREEMENT PROVISIONS. The paragraphs
of Article IX of the Purchase Agreement are hereby incorporated in this
Agreement by reference and made a part hereof; except that the provisions of
such paragraphs shall refer to this Agreement rather than the Purchase Agreement
and shall continue to apply hereto regardless of whether the Purchase Agreement
is any longer in effect.

            (g) NON-TRANSFERABILITY. The Investors' rights and obligations under
this Agreement shall not be transferable to an other party under any
circumstances, whether by operation of law or otherwise (other than to an entity
into which an Investor has been merged or which has acquired substantially all
of the assets of the Investor); provided that the Investor shall have the right
to transfer its rights and obligations hereunder to its affiliates (as such term
is defined in Rule 144 under the Securities Act) in connection with a permitted
transfer of Registrable Securities to such affiliates, so long as such
affiliates agree in writing to be bound by the terms of this Agreement.


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      IN WITNESS WHEREOF, the parties have executed this Registration Agreement
as of the date first written above.

                               AMERICAN BIOGENETIC SCIENCES, INC.


                               By: /s/ Josef C. Schoell
                                   ---------------------------------------------
                                   Name: Josef C. Schoell
                                   Title: V. P. Finance


                               INVESTORS:

                               /s/ Alfred J. Roach
                               -------------------------------------------------
                               Alfred J. Roach


                               BIOTECHNOLOGY VALUE FUND, L.P.
                               By:   BVF PARTNERS L.P., its General Partner
                                     By:   BVF, INC., its General Partner


                                           By:
                                              ----------------------------------
                                                 Mark N. Lampert
                                                 President


                               BIOTECHNOLOGY VALUE FUND II, L.P.
                               By:   BVF PARTNERS L.P., its General Partner
                                     By:   BVF, INC., its General Partner


                                           By:
                                              ----------------------------------
                                                 Mark N. Lampert
                                                 President


                               INVESTMENT 10 L.L.C.
                               By:   BVF PARTNERS, L.P., its Investment Advisor
                                     By:   BVF, INC., its General Partner


                                           By:
                                              ----------------------------------
                                                 Mark N. Lampert
                                                 President


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      IN WITNESS WHEREOF, the parties have executed this Registration Agreement
as of the date first written above.

                               AMERICAN BIOGENETIC SCIENCES, INC.


                               By: /s/
                                   ---------------------------------------------
                                   Name:
                                   Title:


                               INVESTORS:

                               -------------------------------------------------
                               Alfred J. Roach


                               BIOTECHNOLOGY VALUE FUND, L.P.
                               By:   BVF PARTNERS L.P., its General Partner
                                     By:   BVF, INC., its General Partner


                                           By:   /s/ Mark N. Lampert
                                              ----------------------------------
                                                 Mark N. Lampert
                                                 President


                               BIOTECHNOLOGY VALUE FUND II, L.P.
                               By:   BVF PARTNERS L.P., its General Partner
                                     By:   BVF, INC., its General Partner


                                           By:   /s/ Mark N. Lampert
                                              ----------------------------------
                                                 Mark N. Lampert
                                                 President


                               INVESTMENT 10 L.L.C.
                               By:   BVF PARTNERS, L.P., its Investment Advisor
                                     By:   BVF, INC., its General Partner


                                           By:   /s/ Mark N. Lampert
                                              ----------------------------------
                                                 Mark N. Lampert
                                                 President


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