<PAGE>   1
                                                                     Exhibit 4.1

                          REGISTRATION RIGHTS AGREEMENT


            THIS REGISTRATION RIGHTS AGREEMENT (this "Agreement") is made as of
this    day of January, 2000, by and between American Biogenetic Sciences, Inc.,
a Delaware corporation ("ABS"), and Abbott Laboratories, an Illinois corporation
("Abbott").

                                    RECITALS

         WHEREAS, ABS and Abbott are parties to an Exclusive License Agreement
(the "License Agreement") and a Stock Purchase Agreement (the "Stock Purchase
Agreement"), both of which are of even date herewith; and;

         WHEREAS, the execution and delivery of this Agreement are a condition
to the Share Closing of the Stock Purchase Agreement;

NOW, THEREFORE, THE PARTIES HEREBY AGREE AS FOLLOWS:

         1. DEFINITIONS. All terms not otherwise defined in this Agreement shall
have the same meanings ascribed to them in the Stock Purchase Agreement. For
purposes of this Agreement:

                  1.1 EXCHANGE ACT. The term "Exchange Act" shall mean the
Securities Exchange Act of 1934, as amended.

                  1.2 REGISTER, REGISTERED, AND REGISTRATION. The terms
"register," "registered," and "registration" refer to a registration effected by
preparing and filing a registration statement or similar document in compliance
with the Securities Act, and the declaration or ordering of effectiveness of
such registration statement or document.

                  1.3 REGISTRABLE SECURITIES. The term "Registrable Securities"
means such portion of the Shares that has not previously been registered or sold
to the public.

                  1.4 REGISTRATION STATEMENT. The term "Registration Statement"
means a registration statement filed with the SEC under the Securities Act to
register the resale of the Registrable Securities by Abbott.

                  1.5 RULE 144. The term "Rule 144" shall mean Rule 144
promulgated by the SEC (or its successor rule).

                  1.6 SEC. The term "SEC" shall mean the Securities and Exchange
Commission.

                  1.7 SECURITIES ACT. The term "Securities Act" means the
Securities Act of 1933, as amended.
<PAGE>   2
                  1.8 SHARES. The term "Shares" means the shares of Class A
common stock of ABS, $.001 par value per share, issued to Abbott pursuant to the
Stock Purchase Agreement and any common stock of ABS issued as a dividend or
other distribution with respect to such common stock.

         2. REGISTRATION. ABS covenants and agrees as follows:

                  2.1 REGISTRATION RIGHTS - GENERALLY. At any time after the
first anniversary of this Agreement, Abbott may request ABS to file a
Registration Statement registering the resale of the Shares. Within forty-five
(45) days following such request, ABS shall prepare and file a Registration
Statement on Form S-3 (or such other short form registration statement as is
then available) and any related qualification or compliance with respect to all
of the Shares so as to permit or facilitate the sale and distribution of all of
the Shares. ABS agrees to use reasonable commercial efforts to cause the
Registration Statement to be declared effective as soon as practicable after
filing, but in any event no later than three (3) business days after any
notification by the SEC of its decision not to review the Registration Statement
or its determination that it has completed its review of the Registration
Statement and will accept an acceleration request. ABS agrees it will not
include any securities of ABS other than the Shares and will not permit any
other person or entity to include any additional securities in the Registration
Statement to be filed pursuant to this SECTION 2.1.

                  2.2 PIGGYBACK REGISTRATION RIGHTS. If, at any time after the
first anniversary of this Agreement, ABS shall determine to register any of its
securities, either for its own account or the account of a security holder or
holders exercising their respective registration rights, other than (i) a
registration relating solely to employee benefit plans on Form S-8 (or a similar
successor form), or (ii) a registration on Form S-4 (or a similar successor
form) relating solely to a transaction subject to Rule 145 under the Securities
Act, ABS will promptly give Abbott written notice thereof, and subject to the
terms of SECTION 2.3 below, use its reasonable efforts to include in such
registration (and any related qualification under blue sky laws or other
compliance), and in any underwriting involved therein, all Registrable
Securities specified in a written request to ABS made within fifteen (15)
business days after the receipt of such written notice by Abbott.

                  2.3 UNDERWRITING.


                           (a)      If the registration of which ABS gives
                                    notice pursuant to SECTION 2.2 is for a
                                    registered offering involving an
                                    underwriting, then Abbott's right to
                                    registration shall be conditioned upon
                                    Abbott's participation in the underwriting
                                    and the inclusion of Abbott's Registrable
                                    Securities in the underwriting to the extent
                                    provided in this Agreement. Abbott (together
                                    with ABS and the holders of other securities
                                    of ABS distributing their securities through
                                    that underwriting (such other holders being
                                    termed the "Other Holders")) shall enter
                                    into an underwriting agreement in customary



                                      -2-
<PAGE>   3
                                    form with the representative of the
                                    underwriter or underwriters selected by ABS.

                           (b)      Notwithstanding any other provision of this
                                    SECTION 2, if the representative of the
                                    underwriters advises ABS in writing that
                                    marketing factors require a limitation on
                                    the number of shares to be underwritten,
                                    then ABS shall so inform Abbott and the
                                    Other Holders. The number of shares of ABS
                                    common stock being sold by ABS for its own
                                    account shall not be reduced by operation of
                                    this SECTION 2.3. The number of shares of
                                    Registrable Securities held by Abbott and
                                    the Other Holder(s) that may be included in
                                    the underwriting (in addition to those being
                                    sold by ABS for its own account) shall be
                                    allocated among Abbott and the Other Holders
                                    in proportion (as nearly as practicable) to
                                    the amount of Registrable Securities owned
                                    by each such holder.

                           (c)      Any holder which does not agree to the terms
                                    of the such underwriting shall be excluded
                                    from that underwriting by written notice
                                    from ABS or the underwriter. Any Registrable
                                    Securities or other securities excluded or
                                    withdrawn from that underwriting shall be
                                    withdrawn from the registration.

                  2.4 REGISTRATION EXPENSES. ABS shall pay all "registration
expenses" (as defined below) in connection with any registration, qualification
or compliance under this Agreement. Abbott shall pay all "selling expenses" (as
defined below). The term "registration expenses" shall mean all expenses, except
for selling expenses, incurred by ABS in complying with the registration
provisions of this Agreement, including, without limitation, all registration,
qualification and filing fees, printing expenses, escrow fees, fees and
disbursements of counsel for ABS, accounting fees, blue sky fees and expenses,
and the expense of any attest service incident to or required by any such
registration. The term "selling expenses" shall mean all selling commissions,
underwriting fees and stock transfer taxes applicable to the Shares and all fees
and disbursements of counsel for Abbott.

                  2.5 OBLIGATIONS OF ABS. In the case of a registration effected
by ABS pursuant to this SECTION 2, ABS will use reasonable efforts to:

                           (a)      keep such registration effective until the
                                    earliest of:

                                    (i)      such date as all of the Shares have
                                             been sold, or

                                    (ii)     if ABS is not then eligible to
                                             effect such registration on Form
                                             S-3 (or a similar successor form),
                                             one hundred and twenty (120) days
                                             after the effective date of the
                                             Registration Statement, or


                                      -3-
<PAGE>   4
                                    (iii)    the termination of the registration
                                             rights pursuant to SECTION 2.9
                                             hereof.

                           (b)      prepare and file with the SEC such
                                    amendments and supplements to the
                                    Registration Statement and the prospectus
                                    used in connection with the 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 the Registration Statement;

                           (c)      furnish such number of prospectuses,
                                    prospectus supplements, and other documents
                                    incident thereto, including any amendment of
                                    or supplement to the prospectus, as Abbott
                                    from time to time may reasonably request;

                           (d)      cause all Shares registered as described
                                    herein to be listed on any securities
                                    exchange or quoted on any quotation service
                                    on which similar securities issued by ABS
                                    are then listed or quoted;

                           (e)      provided a transfer agent and registrar for
                                    all Registrable Securities registered
                                    pursuant to the Registration Statement and a
                                    CUSIP number for all such Shares;

                           (f)      otherwise use reasonable efforts to comply
                                    with all applicable rules and regulations of
                                    the SEC; and

                           (g)      file the documents required of ABS and
                                    otherwise use reasonable efforts to maintain
                                    requisite blue sky clearance in:

                                    (i)      all jurisdictions in which any of
                                             the Shares are originally sold; and

                                    (ii)     all other states specified in
                                             writing by Abbott, provided as to
                                             this clause (ii), however, that ABS
                                             shall not be required to qualify to
                                             do business or consent to service
                                             of process in any state in which it
                                             is not now so qualified or has not
                                             so consented.

                  2.6 SELLING PROCEDURES.

                           (a)      In the event Abbott intends to sell Shares
                                    pursuant to a Registration Statement, Abbott
                                    shall give ABS five (5) business days notice
                                    of its intent to sell in reliance on such
                                    Registration Statement (the "Notice of
                                    Sale"). ABS may refuse to permit Abbott to
                                    resell any Shares pursuant to the
                                    Registration Statement; provided, however,
                                    that in order to exercise this right, ABS
                                    must



                                      -4-
<PAGE>   5
                                    deliver a certificate in writing within
                                    three (3) business days following the Notice
                                    of Sale to Abbott to the effect that a sale
                                    pursuant to the Registration Statement in
                                    its then current form could constitute a
                                    violation of the federal securities laws. In
                                    such an event, ABS shall either (i) use
                                    commercially reasonable efforts to promptly
                                    amend the Registration Statement, if
                                    necessary, and take all other actions
                                    necessary to allow such sale under the
                                    federal securities laws, and shall notify
                                    Abbott promptly after it has determined that
                                    such sale has become permissible under the
                                    federal securities laws, or (ii) exercise
                                    its right under paragraph (b) below to delay
                                    the sale.

                           (b)      If in the good faith judgment of the Board
                                    of Directors of ABS, after consultation with
                                    counsel, the filing of a Registration
                                    Statement or an amendment thereto or
                                    prospectus supplement so as permit the
                                    proposed sale without a violation of
                                    securities laws 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 ABS,
                                    then it may decline to permit the resale of
                                    any Shares 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. Abbott 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 2.6.

                  2.7 INFORMATION FROM ABBOTT. It shall be a condition precedent
to the obligations of ABS to take any action pursuant to SECTION 2 of this
Agreement with respect to the Shares that Abbott shall furnish to ABS such
information as ABS may reasonably request, including information regarding
Abbott, the Shares held by it, the intended method of disposition of such
securities, and such other information as required to effect the registration of
the Shares.

                  2.8 ASSIGNMENT OF REGISTRATION RIGHTS. The right to cause ABS
to register the Shares pursuant to this Agreement may be assigned by Abbott to a
transferee of the Shares only if:

                            (a)     ABS is, prior to such transfer, furnished
                                    with written notice of the name and address
                                    of such transferee and the Shares with
                                    respect to which such registration rights
                                    are being assigned and a copy of a duly
                                    executed written instrument in form
                                    reasonably satisfactory to ABS by which such
                                    transferee assumes all of the obligations
                                    and


                                      -5-
<PAGE>   6
                                    liabilities of its transferor hereunder and
                                    agrees itself to be bound hereby;

                           (b)      immediately following such transfer the
                                    disposition of the Shares by the transferee
                                    is restricted under the Securities Act;

                           (c)      such assignment includes all of the Shares
                                    then held by Abbott; provided, however, that
                                    such share limitation shall not apply to
                                    transfers by Abbott to its affiliates if all
                                    such transferees or assignees agree in
                                    writing to appoint a single representative
                                    as their attorney-in-fact for the purpose of
                                    receiving any notices and exercising their
                                    rights under this Agreement; and

                           (d)      Abbott guarantees the performance of the
                                    transferee of its obligations under this
                                    Agreement.

                  2.9 TERMINATION OF REGISTRATION RIGHTS. The registration
rights provided in this Agreement shall terminate if Abbott may sell all of the
Shares pursuant to Rule 144 in any three (3) month period. Upon the termination
of registration rights pursuant to this SECTION 2.9, ABS may withdraw the
Registration Statement, or any portion thereof, covering the Shares.

                  2.10 REPORTS UNDER SECURITIES EXCHANGE ACT OF 1934. With a
view to making available to Abbott 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 Abbott to sell securities of ABS to the public without registration
or pursuant to a registration on Form S-3, ABS agrees to:

                           (a)      make and keep public information available,
                                    as those terms are understood and defined in
                                    SEC Rule 144, at all times;

                           (b)      file with the SEC in a timely manner all
                                    reports and other documents required of ABS
                                    under the Securities Act and the Exchange
                                    Act; and

                           (c)      furnish to Abbott, so long as Abbott owns
                                    any Shares, forthwith upon request (i) a
                                    written statement by ABS that it has
                                    complied with the reporting requirements of
                                    SEC Rule 144, the Securities Act and the
                                    Exchange Act, or that it qualifies as a
                                    registrant whose securities may be resold
                                    pursuant to Form S-3, (ii) a copy of the
                                    most recent annual or quarterly report of
                                    ABS and such other reports and documents so
                                    filed by ABS, and (iii) such other
                                    information as may be reasonably requested
                                    in availing Abbott of any rule or regulation
                                    of the SEC that permits the selling of any
                                    such securities without registration or
                                    pursuant to such form.

         3. INDEMNIFICATION AND CONTRIBUTION

                                      -6-
<PAGE>   7
                  3.1 INDEMNIFICATION BY ABS. ABS agrees to indemnify and hold
harmless Abbott, each of Abbott's directors, officers and U.S. wholly-owned
subsidiaries, and each person, if any, who controls Abbott within the meaning of
the Securities Act or the Exchange Act, from and against any losses, claims,
damages or liabilities (or actions or proceedings in respect thereof) to which
they may become subject (under the Securities Act or otherwise) insofar as such
losses, claims, damages or liabilities (or actions or proceedings in respect
thereof) arise out of, or are based upon any untrue statements of a material
fact contained in (or upon the omission of a material fact from) a Registration
Statement delivered or circulated by Abbott in connection with a sale of ABS
securities by Abbott, or arise out of any failure by ABS to fulfill any
undertaking included in the Registration Statement, and ABS will, as incurred
reimburse Abbott and such persons for any legal or other expenses reasonably
incurred in investigating, defending or preparing to defend any such action,
proceeding or claim; provided, however, that ABS shall not be liable in any such
case to the extent that such loss, claim damage or liability arise out of, or is
based upon (i) an untrue statement made in (or upon the omission of a material
fact from) such Registration Statement in reliance upon and in conformity with
written information furnished to ABS by or on behalf of Abbott specifically for
use in preparation of the Registration Statement, (ii) the failure of Abbott to
comply with the covenants or agreements contained in SECTION 2.6 hereof, or
(iii) any untrue statement or omission in any prospectus that is corrected in
any subsequent prospectus that was delivered to Abbott prior to the pertinent
sale or sales by Abbott.

                  3.2 INDEMNIFICATION BY ABBOTT. Abbott agrees to indemnify and
hold harmless ABS, each of ABS's directors and officers, and each person, if
any, who controls ABS within the meaning of the Securities Act or the Exchange
Act, from and against any losses, claims, damages or liabilities (or actions or
proceedings in respect thereof) to which they may become subject (under the
Securities Act or otherwise) insofar as such losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) arise out of, or are
based upon: (i) either an untrue statement made in or the omission of a material
fact from such Registration Statement in reliance upon and in conformity with
written information furnished to ABS by or on behalf of Abbott specifically for
use in preparation of the Registration Statement, (ii) the failure of Abbott to
comply with the covenants or agreements contained in SECTION 2.6 hereof, or
(iii) any untrue statement or omission in any prospectus that is corrected in
any subsequent prospectus that was delivered to Abbott prior to the pertinent
sale or sales by Abbott, and Abbott will, as incurred, reimburse ABS and such
persons for any legal or other expenses reasonably incurred in investigating,
defending, or preparing to defend any such action, proceeding, or claim;
provided, however, that Abbott shall not be liable for any amount in excess of
the amount by which the net amount received by Abbott from the sale of the
Shares to which such loss relates minus the amount of any damages which Abbott
has otherwise been required to pay by reason of such untrue or allegedly untrue
statement or omission or alleged omission

                  3.3 INDEMNIFICATION PROCEDURES. Promptly after receipt by any
indemnified party of a notice of a claim or the beginning of any action in
respect of which indemnity is to be sought against an indemnifying person
pursuant to this SECTION 3, such indemnified person shall notify the
indemnifying person in writing of such claim or of the commencement of such
action and, subject to the provisions hereinafter stated, in case any such
action shall be brought against


                                      -7-
<PAGE>   8
an indemnified person and the indemnifying person shall have been notified
thereof, the indemnifying person shall be entitled to participate therein, and,
to the extent that it shall wish, to assume the defense thereof, with counsel
reasonably satisfactory to the indemnified person. After notice from the
indemnifying person to such indemnified person of the indemnifying person's
election to assume the defense thereof, the indemnifying person shall not be
liable to such indemnified person for any legal expenses subsequently incurred
by such indemnified person in connection with the defense thereof; provided,
however, that if there exists or shall exist a conflict of interest that would
make it inappropriate in the reasonable judgment of the indemnified person for
the same counsel to present both the indemnified person and such indemnifying
person or any affiliate or associate thereof, the indemnified person shall be
entitled to retain its own counsel at the expense of such indemnifying person.

                  3.4 CONTRIBUTION. If the indemnification provided for in this
SECTION 3 is unavailable to or insufficient to hold harmless an indemnified
party under SECTION 3.1 or 3.2 above in respect of any losses, claims, damages,
or liabilities (or actions or proceedings in respect thereof) referred to
therein, then each indemnifying party shall contribute to the amount paid or
payable by such indemnified party as a result of such losses, claims, damages,
or liabilities (or actions in respect thereof) in such proportion as is
appropriate to reflect the relative fault of ABS on one hand and Abbott on the
other in connection with the statements or omissions which resulted in such
losses, claims, damages, or liabilities (or actions in respect thereof), as well
as any other relevant equitable considerations. The relative fault shall be
determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission or alleged omission to state
a material fact related to information supplied by ABS on one hand or Abbott on
the other and the parties' relative intent, knowledge, access to information,
and opportunity to correct or prevent such statement or omission. ABS and Abbott
agree that it would not be just and equitable if contribution pursuant to this
SECTION 3.4 were determined by pro rata allocation or by any other method of
allocation which does not take account of the equitable considerations referred
to above in this SECTION 3.4. The amount paid or payable by an indemnified party
as a result of the losses, claims, damages, or liabilities (or actions in
respect thereof) referred to above in this SECTION 3.4 shall be deemed to
include any legal or other expenses reasonably incurred by such indemnified
party in connection with investigating or defending any such action or claim. No
person guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Securities Act) shall be entitled to contribution from any person
who was not guilty of such fraudulent misrepresentation.

                  3.5 CONTINUING OBLIGATIONS. The obligations of ABS and Abbott
under this SECTION 3 shall survive the completion of the offering of the Shares
pursuant to the Registration Statement and shall be in addition to any liability
that ABS and Abbott may otherwise have.

         4. MISCELLANEOUS.

                  4.1 SURVIVAL OF WARRANTIES. The warranties, representations
and covenants of ABS and Abbott contained in or made pursuant to this Agreement
shall survive the execution and delivery of this Agreement.


                                      -8-
<PAGE>   9
                  4.2 ENTIRE AGREEMENT, CONTROLLING DOCUMENT. This Agreement
constitutes the entire agreement of the parties with respect to the subject
matter hereof and supersedes any and all prior negotiations, correspondence, and
understandings between the parties with respect to the subject matter hereof,
whether oral or in writing.

                  4.3 COUNTERPARTS. This Agreement may be executed in two or
more counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

                  4.4 DELAY AND WAIVER. No delay on the part of either party in
exercising any right under this Agreement shall operate as a waiver of such
right. The waiver by either party of any other term or condition of this
Agreement shall not be construed as a waiver of a subsequent breach or failure
of the same term or condition or a waiver of any other term or condition
contained in this Agreement.

                  4.5 GOVERNING LAW. This Agreement shall be governed by and
construed under the laws of the State of Delaware without regard to conflicts of
law principles.

                  4.6 NOTICES, ETC. All notices and other communications
required or permitted hereunder shall be in writing and shall be sent by
personal delivery, facsimile, overnight courier or mailed by certified or
registered mail, postage prepaid, return receipt requested, to the facsimile
number or address as follows:

                           ABS:           American Biogenetic Sciences, Inc.
                                          1375 Akron Street
                                          Copiague, NY 11726
                                          Telephone: (516) 789-2600
                                          Facsimile: (516) 789-1661
                                          Attention: Chairman

                           with a copy (which will not constitute notice) to:

                                          Brown, Rudnick, Freed & Gesmer
                                          One Financial Center
                                          Boston, MA 02111
                                          Telephone: (617) 856-8200
                                          Facsimile: (617) 856-8201
                                          Attention: Mark A. Hofer, Esq.


                           Abbott:        Abbott Laboratories
                                          100 Abbott Park Road
                                          Dept. 309, Bldg. AP30
                                          Abbott Park, IL 60064-3537
                                          Telephone: (847) 938-6863


                                      -9-
<PAGE>   10
                                          Facsimile: (847) 938-5383
                                          Attention: Senior Vice President,
                                          Pharmaceutical Operations

                           with a copy (which will not constitute notice) to:

                                          Abbott Laboratories
                                          100 Abbott Park Road
                                          Dept. 364, Bldg. AP6D
                                          Abbott Park, Illinois 60064-6049
                                          Telephone: (847) 937 - 8906
                                          Facsimile: (847) 938 - 6277
                                          Attention: Senior Vice President,
                                          Secretary and General Counsel

or to such other facsimile number or address provided to the parties to this
Agreement in accordance with this SECTION 4.6. Such notices or other
communications shall be deemed delivered upon receipt, in the case of overnight
delivery, personal delivery, or facsimile transmission (as evidenced by the
confirmation thereof), or 2 days after deposit in the mails (as determined by
reference to the postmark).

                  4.7 TITLES AND SUBTITLES. The titles and subtitles used in
this Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

                  4.8 EXPENSES. Each party shall pay all costs and expenses that
it incurs with respect to the negotiation, execution, and delivery of this
Agreement.

                  4.9 ALTERNATIVE DISPUTE RESOLUTION. The parties agree to
effectuate all reasonable efforts to resolve in an amicable manner any and all
disputes between them in connection with this Agreement. The parties agree that
any dispute that arises in connection with this Agreement, which cannot be
amicably resolved informally shall be finally settled as set forth in the
Alternative Dispute Resolution provisions of Exhibit C to the License Agreement.

                  4.10 AMENDMENTS AND WAIVERS. Any term of this Agreement may be
amended and the observance of any term of this Agreement may be waived (either
generally or in a particular instance and either retroactively or prospectively)
only with the written consent of ABS and the Abbott.

                  4.11 SEVERABILITY. If one or more provisions of this Agreement
are held to be unenforceable under applicable law, such provision shall be
excluded from this Agreement and the balance of the Agreement shall be
interpreted as if such provision were so excluded and shall be enforceable in
accordance with its terms.


                                      -10-
<PAGE>   11
                  4.12 FURTHER ASSURANCES. ABS and Abbott shall do and perform
or cause to be performed all such further acts and things and shall execute and
deliver all such other agreements, certificates, instruments, or documents as
the other party may reasonably request from time to time in order to carry out
the intent and purposes of this Agreement and the consummation of the
transactions contemplated by the Agreement. Neither ABS nor Abbott shall
voluntarily undertake any course of action inconsistent with the satisfaction of
the requirements applicable to them as set forth in this Agreement, and each
shall promptly do all such acts and take all such measures as may be appropriate
to enable them to perform as early as practicable their obligations under this
Agreement.

                  4.13 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
his Agreement.

                  4.14 MUTUAL DRAFTING. This Agreement is the joint product of
ABS and Abbott and each provision of the Agreement has been subject to
consultation, negotiation and agreement of ABS and Abbott and their respective
legal counsel and advisers and any rule of construction that a document shall be
interpreted or construed against the drafting party shall not apply.

                  4.15 SEC RULE CHANGES. To the extent necessary to give effect
to the agreements and understandings of the parties set forth in this Agreement,
any reference in this Agreement to any forms, rules, regulations, or procedures
of the SEC or any provision of the Securities Act or the Exchange Act existing
as of the date of this Agreement shall be deemed to refer to any modifying,
supplementing, or succeeding rules, regulations procedures, or provisions as may
exist from time to time after the date of this Agreement.

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

                                            AMERICAN BIOGENETIC SCIENCES, INC.


                                            By:
                                                -------------------------------
                                                  Alfred J. Roach, Chairman


                                            ABBOTT LABORATORIES


                                            By:
                                                -------------------------------
                                                  Its:

                SIGNATURE PAGE TO REGISTRATION RIGHTS AGREEMENT

                                      -11-