REGISTRATION RIGHTS AGREEMENT

            THIS   REGISTRATION   RIGHTS   AGREEMENT    ("Registration    Rights
Agreement"),  entered into as of May 20th,  1998, by and between the  purchasers
set forth on the signature pages hereof (each, a "Purchaser",  and collectively,
the "Purchasers") and AMERICAN BIOGENETIC SCIENCES, INC., a Delaware corporation
with offices at 1375 Akron Street, Copiague, NY 11726 (the "Company").


                              W I T N E S S E T H:

            WHEREAS, pursuant to Securities Subscription Agreements, dated as of
the  date  hereof  (the  "Agreements"),  by and  between  the  Company  and  the
Purchasers,  the  Company has agreed to sell and the  Purchasers  have agreed to
purchase an aggregate of $4,000,000 of the Company's 5%  Convertible  Debentures
due May 20, 2001 (the  "Debentures")  convertible  into shares of the  Company's
Class A Common Stock, $.001 par value (the "Common Stock");

            WHEREAS,  the Company has agreed to issue,  in  connection  with the
issuance of the  Debentures,  Warrants to purchase  shares of Common  Stock (the
"Warrant");

            WHEREAS, pursuant to the terms of, and in partial consideration for,
the Purchasers'  purchase of the  Debentures,  the Company has agreed to provide
the  Purchaser  with certain  registration  rights with respect to the shares of
Common Stock  issuable  upon  conversion of the  Debentures  and exercise of the
Warrants  (collectively,  the "Shares") as set forth in this Registration Rights
Agreement;

            NOW,   THEREFORE,   in   consideration   of  the  mutual   promises,
representations,   warranties,   covenants  and  conditions  set  forth  in  the
Agreements  and  this  Registration  Rights  Agreement,   the  Company  and  the
Purchasers agree as follows:

            1.    Certain  Definitions.  As  used in  this  Registration  Rights
Agreement, the following terms shall have the following respective meanings, and
terms not  otherwise  defined  herein  shall have their  respective  meanings as
assigned to them in the Agreements:

            "Commission"  shall mean the Securities  and Exchange  Commission or
any other federal agency at the time administering the Securities Act.

            "Holders"  shall  include  the  Purchasers  and  any  transferee  of
Debentures,  Warrants or Registrable  Securities to whom the registration rights
conferred  by this  Registration  Rights  Agreement  have  been  transferred  in
compliance with Section 10 of this Registration Rights Agreement.

            "Registrable  Securities"  shall mean any Shares or other securities
issued or issuable to a Purchaser or any Holder upon the  conversion or exercise
or  exchange  of any  Debenture,  Warrant  or  Shares  which  have not been sold
pursuant to the Registration  Statement or under Rule 144 promulgated  under the
Securities Act ("Rule 144") or are eligible for sale under paragraph (k) of Rule
144.








            The terms "register", "registered" and "registration" shall refer to
a  registration  effected by preparing  and filing a  registration  statement in
compliance  with  the  Securities  Act  and  applicable  rules  and  regulations
thereunder,  and  the  declaration  or  ordering  of the  effectiveness  of such
registration statement.

            "Registration  Expenses"  shall mean all  expenses to be incurred by
the Company in connection with Purchasers' exercise of their registration rights
under this Registration Rights Agreement,  including,  without  limitation,  all
registration  and filing fees,  printing  expenses,  fees and  disbursements  of
counsel  for the  Company,  blue  sky  fees and  expenses,  reasonable  fees and
disbursements  of  counsel to Holder for a "due  diligence"  examination  of the
Company and review of the  Registration  Statement  and related  documents,  the
expense of any special audits  incident to or required by any such  registration
and the  compensation of regular  employees of the Company.  With respect to the
"due  diligence"  examination of the Company,  the  Registration  Expenses shall
include only fees and disbursements  for one (1) designated  counsel for all the
Holders of  Debentures  and the amount  thereof to be borne by the Company shall
not exceed $5,000.

            "Registration Statement" shall have the meaning set forth in Section
2(a) herein.

            "Regulation D" shall mean  Regulation D as  promulgated  pursuant to
the Securities Act, and as subsequently amended.

            "Securities Act" shall mean the Securities Act of 1933, as amended.

            "Selling Expenses" shall mean all underwriting discounts and selling
commissions  applicable  to the  sale of  Registrable  Securities,  all fees and
disbursements  of counsel for Holder not included with  "Registration  Expenses"
and the compensation of regular employees of the Purchasers.

            2.    Registration  Requirements.  The  Company  shall  use its best
efforts to effect the  registration  of the Registrable  Securities  (including,
without  limitation,  the  execution of an  undertaking  to file  post-effective
amendments,  appropriate  qualification under applicable blue sky or other state
securities laws and appropriate  compliance with applicable  regulations  issued
under the Securities Act) as would permit or facilitate the sale or distribution
of all the Registrable  Securities in the manner  (including manner of sale) and
in all states  reasonably  requested by the Holders under a broad-based  plan of
distribution  reasonably acceptable to the Purchasers.  Such best efforts by the
Company shall include without limitation the following:

                  (a)   The Company shall, as soon as practicable after the date
hereof but in no event  later than sixty (60) days after the date  hereof,  file
(i) a registration  statement with the Commission pursuant to Rule 415 under the
Securities  Act on Form S-3 under the  Securities  Act (or in the event that the
Company  is  ineligible  to use such form,  such  other  form as the  Company is
eligible  to use under the  Securities  Act and  consented  to by a majority  in
interest of the Registrable Securities,  which consent shall not be unreasonably
withheld)  covering the  Registrable  Securities  so requested to be  registered
("Registration  Statement");  (ii)  such  blue sky  filings  as shall  have been
reasonably  requested  by the Holders;  and (iii) any required  filings with the
National Association of Securities Dealers, Inc. or exchange or market where the
Shares are

                                      - 2 -








traded.  Thereafter  the  Company  shall  use its  best  efforts  to  have  such
Registration  Statement  and other  filings  declared  effective  as promptly as
practicable.

                  (b)   If the Company  fails to file a  Registration  Statement
complying with the requirements of this Registration  Rights Agreement within 60
days after the Closing under the Subscription Agreements or if such Registration
Statement has not become  effective  within 120 days after the Closing under the
Subscription  Agreements,  the Holders  shall  have,  in addition to and without
limiting  any  other  rights  they  may have at law,  in  equity  or  under  the
Debentures,  the Agreements or this Registration Rights Agreement (including the
right to specific performance), the right to receive, as liquidated damages, the
following payments:

                  an amount equal to 1% of the Outstanding  Principal Amount (as
            defined in the Debentures) of the Debentures, in cash, for the first
            30-day period following such period that such Registration Statement
            is not filed or effective  as  applicable,  1.5% of the  Outstanding
            Principal  Amount (as defined in the  Debentures) of the Debentures,
            in cash,  for the second  30-day period  following  such period that
            such   Registration   Statement  is  not  filed  or  effective,   as
            applicable,  and 2% of the Outstanding  Principal Amount (as defined
            in the Debentures) of the  Debentures,  in cash, for each additional
            30-day period thereafter (the payments under this Section 2(b) shall
            be pro rated for any period of less than 30 days).  In  addition  to
            the  foregoing,   if  after  180  days  from  the  date  hereof  the
            Registration  Statement  has  not  been  declared  effective  by the
            Commission,  then upon  demand of any  Holders,  the  Company  shall
            redeem all or any specified  portion of the Debentures  held by such
            Holders  at a  redemption  price  equal  to 130% of the  Outstanding
            Principal  Amount of the Debentures plus accrued  interest  thereon,
            together with all other  payments due under the  Debentures  and the
            Agreements.

                  (c)   If the  Holders  intend to  distribute  the  Registrable
Securities covered by its request by means of an underwriting, the Holders shall
so advise the Company.  The Holders will have the right to select the investment
bankers  for  such  underwriting   subject  to  such  investment  bankers  being
reasonably  satisfactory  to the Company  and the Company  shall enter into such
customary  agreements  (including a customary  underwriting  agreement  with the
underwriter or underwriters,  if any) and take all such other reasonable actions
in connection  therewith in order to expedite or facilitate  the  disposition of
such Registrable Securities.

                  (d)   Whether or not an underwriting agreement is entered into
and whether or not the Registrable  Securities are to be sold in an underwritten
offering the Company will:

                        (i)   make such  representations  and  warranties to the
      Holders and the underwriter or  underwriters,  if any, in form,  substance
      and scope as are customarily  made by issuers to underwriters in secondary
      underwritten offerings;

                        (ii)  cause  to  be   delivered   to  the   sellers   of
      Registrable  Securities  and  the  underwriter  or  underwriters,  if any,
      opinions and advice of counsel to the Company,  dated the  effective  date
      (or in the case of an underwritten offering, dated the

                                      - 3 -








      date of delivery of any Registrable  Securities sold pursuant  thereto) of
      the Registration  Statement  (which counsel,  and opinions and advices (in
      form,  scope  and  substance),  shall be  reasonably  satisfactory  to the
      managing   underwriter  or   underwriters,   if  any,  and  the  appointed
      representative  or counsel of the  Holders),  addressed to the Holders and
      each  underwriter,  if any,  covering the matters  customarily  covered in
      opinions and advices requested in secondary underwritten offerings and, in
      the  case  of an  underwritten  offering,  such  other  matters  as may be
      reasonably requested by the Holders;

                        (iii) cause to be  delivered,  immediately  prior to the
      effectiveness  of the  Registration  Statement  (and,  in the  case  of an
      underwritten  offering,  at  the  time  of  delivery  of  any  Registrable
      Securities sold pursuant  thereto),  a "comfort" letter from the Company's
      independent certified public accountants addressed to the Holders and each
      underwriter,  if any, stating that such accountants are independent public
      accountants  within the meaning of the  Securities  Act and the applicable
      published  rules and  regulations  thereunder,  and otherwise in customary
      form and covering such financial and accounting matters as are customarily
      covered  by  letters  of  the  independent  certified  public  accountants
      delivered in connection with secondary underwritten public offerings;

                        (iv)  if an underwriting  agreement is entered into, the
      same  shall  set  forth  in  full  the  indemnification  and  contribution
      provisions and procedures  similar to those  contained in Sections 6 and 7
      herein  with  respect to all  parties to be  indemnified  pursuant to such
      sections; and

                        (v)   the  Company  shall  deliver  such  documents  and
      certificates  as  may  be  reasonably  requested  by  the  Holders  of the
      Registrable   Securities  being  sold  or  the  managing   underwriter  or
      underwriters,  if any,  to evidence  compliance  with clause (i) above and
      with any customary conditions contained in the underwriting  agreement, if
      any, or other agreement entered into by the Company;

the  foregoing in this  paragraph  2(d) shall be done at each closing under such
underwriting or similar  agreement or as and to the extent required  thereunder;
provided, however, the foregoing in paragraph 2(d) shall not be required on more
than two (2) occasions.

            (e)   The  Company  shall  make   available  for   inspection  by  a
      representative  or  representatives   of  the  Holders,   any  underwriter
      participating in any disposition pursuant to a Registration Statement, and
      any attorney or accountant  retained by such Holders or  underwriter,  all
      financial  and  other  records  customary  for  such  purposes,  pertinent
      corporate documents and properties of the Company, and cause the Company's
      officers,  directors  and employees to supply all  information  reasonably
      requested by any such representative,  underwriter, attorney or accountant
      in connection with such Registration Statement.  The Holders agree to keep
      all  non-public   information  supplied  to  it  confidential  until  such
      information is included in the Registration Statement.

            3.    Expenses of Registration.  All Registration  Expenses incurred
in  connection  with  any   registration,   qualification   or  compliance  with
registration  pursuant to this  Registration  Rights Agreement shall be borne by
the Company, and all Selling Expenses shall be

                                      - 4 -









borne by the Holders.

            4.    Registration  on Form  S-3.  The  Company  shall  use its best
efforts to qualify for  registration  on Form S-3 or any comparable or successor
form or forms,  or in the event that the Company is ineligible to use such form,
such form as the Company is eligible to use under the Securities Act.

            5.    Registration  Procedures.  In the  case of  each  registration
effected by the Company  pursuant to this  Agreement,  the Company will keep the
Holders advised in writing as to the initiation of each  registration  and as to
the completion  thereof.  At its expense,  the Company will use its best efforts
to:

                  (a)   Keep such  registration  effective for the period ending
(a) fifty-four (54) months, as extended pursuant to Section 5A hereof, after the
date hereof or, (b) the Shares are no longer Registrable  Securities,  whichever
first occurs.

                  (b)   Furnish such number of prospectuses,  and amendments and
supplements  thereto,  and other documents  incident thereto as any Holders from
time to time may reasonably request.

                  (c)   Prepare and file with the Commission such amendments and
post-  effective  amendments to a Registration  Statement as may be necessary to
keep such Registration  Statement effective for the applicable period; cause the
related Prospectus to be supplemented by any required Prospectus supplement, and
as so  supplemented  to be filed pursuant to Rule 424 under the Securities  Act;
and comply with the  provisions  of the  Securities  Act  applicable  to it with
respect  to the  disposition  of all  securities  covered  by such  Registration
Statement  during the applicable  period in accordance with the intended methods
of disposition by the sellers thereof set forth in such  Registration  Statement
or supplement to such Prospectus;

                  (d)   Notify  each of the  Holders of  Registrable  Securities
included  in  the  Registration  Statement,   their  counsel  and  the  managing
underwriters,  if any,  promptly  (but in no event later than two business  days
thereafter)  and (if  requested  by any such  Person)  confirm  such  notice  (a
"Notice") in writing,  (1) when a Prospectus  or any  Prospectus  supplement  or
post-effective  amendment has been filed,  and,  with respect to a  Registration
Statement or any post-effective  amendment,  when the same has become effective,
(2)  of any  request  by the  Commission  for  amendments  or  supplements  to a
Registration Statement or related Prospectus or for additional information,  (3)
of the issuance by the Commission of any stop order suspending the effectiveness
of a  Registration  Statement  or the  initiation  of any  proceedings  for that
purpose,  (4) if at any time the  representations  and warranties of the Company
contained  in  agreements  contemplated  by  Section  2(d)  cease to be true and
correct,  (5) of the receipt by the Company of any notification  with respect to
the suspension of the  qualification  of any of the  Registrable  Securities for
sale in any  jurisdiction or the initiation or threatening of any proceeding for
such  purpose,  (6) of the  happening  of any  event  as a result  of which  the
Prospectus  included in the Registration  Statement (as then in effect) contains
any untrue  statement  of a material  fact or omits to state any  material  fact
required to be stated  therein or necessary to make the  statements  therein (in
the  case of the  Prospectus  or any  preliminary  Prospectus,  in  light of the
circumstances under

                                      - 5 -








which  they  were  made)  not  misleading  and (7) of the  Company's  reasonable
determination that a post-effective  amendment to a Registration Statement would
be appropriate or that there exist circumstances not yet disclosed to the public
which make further sales under such Registration  Statement  inadvisable pending
such disclosure and post-effective amendment;

                  (e)   Upon the occurrence of any event contemplated by Section
5(d)(2)- (7) and  immediately  upon the  expiration  of any Blocking  Period (as
defined in  Section  5A),  prepare,  if the  occurrence  of such event or period
requires  such  preparation,  a supplement  or  post-effective  amendment to the
Registration  Statement  or  related  Prospectus  or any  document  incorporated
therein by reference or file any other required  document so that, as thereafter
delivered to the purchasers of the Registrable Securities being sold thereunder,
such Prospectus will not contain an untrue  statement of a material fact or omit
to state  any  material  fact  necessary  to make  the  statements  therein  not
misleading;

                  (f)   Make every reasonable effort to obtain the withdrawal of
any order suspending the  effectiveness of the  Registration  Statement,  or the
lifting  of any  suspension  of  the  qualification  of  any of the  Registrable
Securities for sale in any jurisdiction, at the earliest possible moment;

                  (g)   Insure that all  Registrable  Securities  subject to the
Registration  Statement  shall at all times be registered or qualified for offer
and sale  under the  securities  or blue sky laws of such  jurisdictions  as any
Holders or underwriter  reasonably requests in writing;  use its best efforts to
keep each such  registration or qualification  effective,  including through new
filings or amendments or renewals, during the period such Registration Statement
is  required  to be  kept  effective  and do any and all  other  acts or  things
reasonably   necessary  or  advisable   to  enable  the   disposition   in  such
jurisdictions   of  the  Registrable   Securities   covered  by  the  applicable
Registration Statement; provided, however, that the Company will not be required
to qualify to do business  or take any action that would  subject it to taxation
or  general  service  of  process  in any  jurisdiction  where it is not then so
qualified or subject;

                  (h)   Use its best efforts to cause the Registrable Securities
covered by the Registration  Statement to be registered with or approved by such
other  governmental  agencies or  authorities  as may be necessary to enable the
seller or  sellers  thereof  or the  underwriter  or  underwriters,  if any,  to
consummate the disposition of such Registrable Securities in accordance with the
chosen method or methods of distribution; and

                  (i)   Cause  all  Registrable   Securities  included  in  such
Registration  Statement to be listed,  by the date of first sale of  Registrable
Securities pursuant to such Registration  Statement, on the principal securities
exchange or automated interdealer system on which the same type of securities of
the Company are then listed or traded.

            5A.   Suspensions   of   Effectiveness.   The  Company  may  suspend
dispositions  under the Registration  Statement and notify the Holders that they
may not sell the Registrable  Securities pursuant to the Registration  Statement
or Prospectus (a "Blocking Notice") if the Company's  management  determines (x)
in its reasonable  good faith  judgment that the Company's  obligation to ensure
that such Registration Statement and Prospectus are current and complete


                                      - 6 -








would  require the Company to take actions that might  reasonably be expected to
have  a  materially   adverse   detrimental   effect  on  the  Company  and  its
stockholders;  or (y) of the existence of any fact or the happening or any event
that makes any statement of a material fact made in the Registration  Statement,
the  Prospectus,   any  amendment  or  supplement   thereto,   or  any  document
incorporated  by  reference  therein  untrue in any  material  respect,  or that
requires the making of any additions to or changes in the Registration Statement
or the Prospectus, in order to make the statements therein not misleading in any
material  respect,  provided that such suspension  pursuant to a Blocking Notice
may not exceed thirty (30) days (whether or not  consecutive) in any twelve (12)
month period.  The Holders agree by  acquisition of the  Registrable  Securities
that,  upon  receipt  of a  Blocking  Notice  from the  Company  indicating  the
existence  of any fact of the kind  described  in the  previous  sentence,  such
Holders shall not dispose of, sell or offer for sale the Registrable  Securities
pursuant to the Registration  Statement until such Holders receive (i) copies of
the supplemented or amended  Prospectus,  or until counsel for the Company shall
have determined  that such disclosure is not required due to subsequent  events,
(ii)  notification in writing from the Company (the "Advice")  advising that the
use of the  Prospectus  may be resumed  and (iii)  copies of any  additional  or
supplemental filings that are incorporated by reference in the Prospectus. If so
directed by the Company in  connection  with any such  notice,  each Holder will
deliver  o the  Company  (at the  Company's  expense)  all  copies,  other  than
permanent  file  copies  then in such  Holder's  possession,  of the  Prospectus
covering such Registrable  Securities that was current  immediately prior to the
time of receipt of such  notice.  In the event the  Company  shall give any such
Blocking  Notice,  the time  regarding the  effectiveness  of such  Registration
Statement  set forth in Section  5(a) and the  Maturity  Date of the  Debentures
shall be extended by one and  one-half  (1-1/2)  times the number of days during
the period from and including the date of the giving of such Blocking  Notice to
and  including  the date when the Holders  shall have received the copies of the
supplemented   or  amended   Prospectus,   the  Advice  and  any  additional  or
supplemental  filings that are  incorporated  by  reference  in the  Prospectus.
Delivery of a Blocking  Notice and the related  suspension  of any  Registration
Statement  shall not  constitute a default  under this  Agreement  and shall not
create any obligation to pay liquidated damages under Section 2 hereof. However,
if the Holder's  ability to sell under the  Registration  Statement is suspended
for more than the thirty (30) day period  described  above (an "Excess  Blocking
Period"),  then the rate of  interest  on all of the  Debentures  shall,  to the
maximum extent  permitted by law, be  permanently  increased by two percent (2%)
per annum  (i.e.,  from 5% to 7% per annum)  commencing  on the first day of the
thirty (30) day period (or part  thereof)  following  the beginning of an Excess
Blocking  Period;  an  additional  two percent (2%) per annum  commencing on the
first day of each of the second and third such  thirty (30) day periods (or part
thereof)  thereafter;  and an additional one (1%) percent per annum on the first
day of each  consecutive  thirty  (30) day period (or part  thereof)  thereafter
until the Excess Blocking Period terminates. In addition, if the Excess Blocking
Period  continues for more than an aggregate of 120 days in any 360-day  period,
then at each Holder's option, the Company shall redeem such Holder's  Debentures
at a redemption  price equal to 130% of the Outstanding  Principal Amount of the
Debentures  plus accrued  interest  thereon to the date of redemption,  together
with all payments due under this  paragraph and under such  Holder's  Debentures
and the Agreements.

                                      - 7 -








            6.    Indemnification.

                  (a)   Company  Indemnity.  The  Company  will  indemnify  each
Holder,  each  of  its  officers,   directors  and  partners,  and  each  person
controlling such Holder,  within the meaning of Section 15 of the Securities Act
and the rules and  regulations  thereunder  with respect to which  registration,
qualification  or  compliance  has been effected  pursuant to this  Registration
Rights Agreement,  and each  underwriter,  if any, and each person who controls,
within  the  meaning  of  Section  15 of the  Securities  Act and the  rules and
regulations thereunder, any underwriter, against all claims, losses, damages and
liabilities  (or  actions in  respect  thereof)  arising  out of or based on any
untrue  statement (or alleged untrue  statement) of a material fact contained in
the registration statement (including any prospectus, or other document incident
to any such  registration  or related  qualification  or  compliance  with state
securities  laws),  or based on any  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 any  violation  by the  Company of the
Securities  Act or any  state  securities  law or in  either  case,  any rule or
regulation  thereunder  applicable  to the  Company  and  relating  to action or
inaction  required  of the  Company in  connection  with any such  registration,
qualification  or  compliance,  and  will  reimburse  each  Holder,  each of its
officers,  directors and partners, and each person controlling such Holder, each
such  underwriter  and each person who  controls any such  underwriter,  for any
legal  and  any  other   expenses   reasonably   incurred  in  connection   with
investigating and defending any such claim, loss,  damage,  liability or action,
provided that the Company will not be liable in any such case to the extent that
any such claim, loss, damage,  liability or expense arises out of or is based on
any untrue  statement or omission (or alleged untrue statement or omission) that
is made in reliance upon and in conformity with written information furnished to
the Company by such older or the underwriter  and stated to be specifically  for
use therein.  The indemnity  agreement  contained in this Section 6(a) 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 Company
(which consent will not be unreasonably withheld).

                  (b)   Holders  Indemnity.  Each Holder  will,  if  Registrable
Securities  held  by  it  are  included  in  the  securities  as to  which  such
registration,  qualification  or  compliance  is being  effected,  indemnify the
Company, each of its directors,  officers,  partners,  and each underwriter,  if
any, of the Company's securities covered by such a registration statement,  each
person who  controls  the  Company  or such  underwriter  within the  meaning of
Section 15 of the Securities Act and the rules and regulations thereunder,  each
other Holder (if any), and each of their officers,  directors and partners,  and
each person  controlling such other Holder against all claims,  losses,  damages
and liabilities (or actions in respect  thereof)  arising out of or based on any
untrue  statement (or alleged untrue  statement) of a material fact contained in
the registration  statement (including any prospectus or other document incident
to any such  registration  or related  qualification  or  compliance  with state
securities  laws),  or based on any  omission  (or  alleged  omission)  to state
therein a material fact  required to be stated  therein or necessary to make the
statement  therein  not  misleading,  and will  reimburse  the  Company and such
underwriters  and other Holders and their directors,  officers and partners,  or
control  persons  for any legal or any other  expenses  reasonably  incurred  in
connection  with  investigating  and  defending  any such claim,  loss,  damage,
liability or action,  in each case to the extent,  but only to the extent,  that
such untrue

                                      - 8 -









statement (or alleged  untrue  statement)  or omission (or alleged  omission) is
made in reliance upon and in conformity  with written  information  furnished to
the  Company  by such  Holders  and stated or known to be  specifically  for use
therein,  and provided that no Holders shall be liable under this  indemnity for
an amount in excess of net  proceeds  received  by Holders  from the sale of the
Registrable  Securities pursuant to such Registration  Statement.  The indemnity
agreement  contained  in this  Section  6(b) shall not apply to amounts  paid in
sttlement of any such claims,  losses, damages or liabilities if such settlement
is effected  without the consent of such  Holders  (which  consent  shall not be
unreasonably withheld).

                  (c)   Procedure.  Each party entitled to indemnification under
this Section (the  "Indemnified  Party") shall give notice to the party required
to  provide  indemnification  (the  "Indemnifying  Party")  promptly  after such
Indemnified Party has actual knowledge of any claim as to which indemnity may be
sought,  and shall  permit the  Indemnifying  Party to assume the defense of any
such claim in any litigation resulting therefrom,  provided that counsel for the
Indemnifying Party who shall conduct the defense of such claim or any litigation
resulting  therefrom shall be approved by the Indemnified  Party (whose approval
shall not be unreasonably  withheld),  and the Indemnified Party may participate
in such defense at such party's  expense,  and provided further that the failure
of any Indemnified Party to give notice as provided herein shall not relieve the
Indemnifying  Party of its  obligations  under this Article except to the extent
that the Indemnifying Party is materially and adversely affected by such failure
to provide notice.  The Indemnifying Party shall not, in connection with any one
such action or  proceeding  or  separate  but  substantially  similar or related
actions or proceedings in the same jurisdiction  arising out of the same general
allegations or circumstances,  be liable for the reasonable fees and expenses of
more than one separate firm of attorneys  (in addition to any local  counsel) at
any time for such Indemnified Party, provided, however, that if separate firm(s)
of attorneys are required due to a conflict of interest,  then the  Indemnifying
Party shall be liable for the reasonable fees and expenses of each such separate
firm. No  Indemnifying  Party,  in the defense of any such claim or  litigation,
shall,  except with the consent of each Indemnified  Party,  consent to entry of
any  judgment  or enter  into  any  settlement  which  does  not  include  as an
unconditional  term  thereof  the giving by the  claimant or  plaintiff  to such
Indemnified  Party of a release  from all  liability in respect to such claim or
litigation.  Each  Indemnified  Party hall  furnish such  information  regarding
itself or the claim in question as an Indemnifying  Party may reasonably request
in writing and as shall be reasonably required in connection with the defense of
such claim and litigation resulting therefrom.

            7.    Contribution.  (a)  If  the  indemnification  provided  for in
Section 6 herein is  unavailable  to the  Indemnified  Parties in respect of any
losses,  claims, damages or liabilities referred to herein (other than by reason
of the exceptions provided therein),  then each such Indemnifying Party, in lieu
of indemnifying such Indemnified  Party,  shall contribute to the amount paid or
payable by such Indemnified Party as a result of such losses, claims, damages or
liabilities  (i) as between  the Company and the Holders on the one hand and the
Holders or underwriters, as the case may be, on the other, in such proportion as
is appropriate to reflect the relative  benefits received by the Company and the
Holders on the one hand and the Holders or underwriters,  as the case may be, on
the other from the offering of the Registrable Securities, or if such allocation
is not permitted by applicable  law, in such  proportion  as is  appropriate  to
reflect not only such

                                      - 9 -








relative benefits but also the relative fault of the Company on the one hand and
of the Holders or  underwriters,  as the case may be, on the other in connection
with the statements or omissions which resulted in such losses,  claims, damages
or liabilities,  as well as any other relevant equitable considerations and (ii)
as between  the  Company on the one hand and the  Holders on the other,  in such
proportion as is appropriate to reflect the relative fault of the Company and of
the Holders in connection  with the  statements or omissions  which  resulted in
such  losses,  claims,  damages or  liabilities,  as well as any other  relevant
equitable considerations.

                  (b)   The relative benefits received by the Company on the one
hand and the Holders or the underwriters, as the case may be, on the other shall
be deemed to be in the same proportion as the proceeds from the offering (net of
underwriting  discounts and commissions but before deducting  expenses) received
by the Company from the initial sale of the Registrable Securities, the proceeds
received by the Holders from the sale of Registrable  Securities pursuant to the
Registration  Statement  or the total  underwriting  discounts  and  commissions
received by the  underwriters as set forth in the table on the cover page of the
prospectus  contained  in the  Registration  Statement,  as the case may be. The
relative  fault  of  the  Company  on  the  one  hand  and  of  the  Holders  or
underwriters,  as the case may be, on the other shall be determined by reference
to,  among other  things,  whether the untrue or alleged  untrue  statement of a
material  fact or omission or alleged  omission to state a material fact relates
to information supplied by the Company, by the Holders or by the underwriters.

                  (c)   In no event  shall the  obligation  of any  Indemnifying
Party  (other than the  Company) to  contribute  under this Section 7 exceed the
amount that such  Indemnifying  Party would have been obligated to pay by way of
indemnification if the  indemnification  provided for under Section 6(a) or 6(b)
hereof had been available under the circumstances.

                  (d)   The Company  and the Holders  agree that it would not be
just and equitable if contribution pursuant to this Section 7 were determined by
pro rata allocation (even if the Holders or the underwriters were treated as one
entity for such  purpose) or by any other  method of  allocation  which does not
take  account of the  equitable  considerations  referred to in the  immediately
preceding  paragraphs.  The amount paid or payable by an Indemnified  Party as a
result  of the  losses,  claims,  damages  and  liabilities  referred  to in the
immediately  preceding  paragraphs  shall be deemed to  include,  subject to the
limitations set forth above, any legal or other expenses  reasonably incurred by
such  Indemnified  Party in connection with  investigating or defending any such
action or claim.  Notwithstanding  the provisions of this section, no Holders or
underwriter  shall be required to contribute  any amount in excess of the amount
by which (i) in the case of such Holders, the total price at which the shares of
Common Stock sold by such Holders pursuant to the Registration  Statement exceed
the  amount  paid by such  Holders  for the  securities  which  the  Registrable
Securities sold (including the exercise price of shares of Common Stock acquired
upon the exercise of Warrants) underlie, (ii) in the case of an underwriter, the
total price at which the Registrable  Securities purchased by it and distributed
to the public were offered to the public  exceeds,  in any such case, the amount
of any  damages  that the  Holders  or  underwriter  would have  otherwise  been
required to pay by reason of such untrue or alleged untrue statement or omission
or alleged omission.  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

                                     - 10 -








who was not guilty of such fraudulent misrepresentation.

            8.    Survival. The indemnity and contribution  agreements contained
in  Sections  6 and 7 and the  representations  and  warranties  of the  Company
referred to in Section  2(d)(i)  shall  remain  operative  and in full force and
effect regardless of (i) any termination of this  Registration  Rights Agreement
or any underwriting  agreement,  (ii) any investigation  made by or on behalf of
any  Indemnified  Party  or by or on  behalf  of  the  Company,  and  (iii)  the
consummation of the sale or successive resales of the Registrable Securities.

            9.    Information by Holders.  Each Holder shall promptly furnish to
the Company such  information  regarding such Holder and the sale of Registrable
Securities  proposed by such  Holders as the Company may  reasonably  request in
writing and as shall be reasonably required in connection with any registration,
qualification or compliance  referred to in this Registration  Rights Agreement.
All  information  provided to the Company by such Holder  shall be accurate  and
complete in all  material  respects and such Holder  shall  promptly  notify the
Company if any such information becomes incorrect or incomplete.  If such Holder
does not timely provide all such reasonably requested  information,  such Holder
shall not be entitled to the liquidated damages  contemplated by Section 2(b) to
the extent that such delay in the Registration  Statement  becoming effective is
caused by such failure to timely provide information unless such Holder shall be
able to demonstrate to the Company's  reasonable  satisfaction that such failure
to timely provide did not proportionately contribute to the event giving rise to
the damages.

            10.   Transfer or  Assignment  of  Registration  Rights.  The rights
granted  to the  Purchasers  by  the  Company  under  this  Registration  Rights
Agreement  to cause  the  Company  to  register  Registrable  Securities  may be
transferred or assigned to a transferee or assignee of any Holder, provided that
the Company is given written notice by any applicable  Holders at the time of or
within a reasonable time after said transfer or assignment, stating the name and
address of said  transferee  or assignee and  identifying  the  securities  with
respect to which such registration rights are being transferred or assigned; and
provided  further  that the  transferee  or assignee  of such  rights  agrees in
writing to be bound by this Registration Rights Agreement.

            11.   Miscellaneous.

                  (a)   Entire Agreement.  This  Registration  Rights Agreement,
the Agreements, the Debentures and the Warrants contain the entire understanding
and  agreement  of the  parties,  and may not be  amended,  waived,  discharged,
modified or terminated  except by a written  agreement  signed in the case of an
amendment,  modification or  termination,  by holders of at least 66 2/3% of the
Registrable  Securities,  and in the case of a waiver or  discharge by the party
against whom enforcement of such waiver or discharge is sought.

                  (b)   Notices. Unless otherwise provided herein, any notice or
other  communication  to a party  hereunder  shall be  sufficiently  given if in
writing and personally  delivered or sent by facsimile with copy sent in another
manner  herein  provided  or sent by  courier  (which for all  purposes  of this
Warrant  shall  include  Federal  Express,  UPS or  other  recognized  overnight
courier) or mailed to said party by certified mail, return receipt requested, at
its address  provided for herein or such other  address as either may  designate
for itself in such notice to the other and

                                     - 11 -








communications  shall be deemed to have been received when delivered  personally
on the scheduled  arrival date when sent by next day or 2-day courier service or
if sent by facsimile upon receipt of transmittal confirmation or if sent by mail
three days after deposit in the mail.

                  (c)   Gender of Terms.  All terms used herein  shall be deemed
to include the feminine and the neuter,  and the singular and the plural, as the
context requires.

                  (d)   Choice  of Law and  Venue;  Waiver of Jury  Trial.  THIS
REGISTRATION  RIGHTS AGREEMENT SHALL BE CONSTRUED UNDER THE LAWS OF THE STATE OF
NEW YORK  WITHOUT  REGARD TO  PRINCIPLES  OF  CONFLICTS  OF LAW OR CHOICE OF LAW
(OTHER THAN SECTION 5-1401 OF THE NEW YORK GENERAL OBLIGATIONS LAW). The parties
hereby agree that all actions or proceedings arising directly or indirectly from
or in connection with this Registration Rights Agreement shall be litigated only
in the  Supreme  Court of the State of New York or the  United  States  District
Court for the  Southern  District of New York  located in New York  County,  New
York. The parties consent to the  jurisdiction and venue of the foregoing courts
and consent that any process or notice of motion or other  application to either
of said courts or a judge  thereof may be served  inside or outside the State of
New York or the Southern District of New York by registered mail, return receipt
requested,  directed as provided in Section  11(b) (and service so made shall be
deemed complete five (5) days after the same has been posted as aforesaid) or by
personal  service or in such other manner as may be permissible  under the rules
of said  courts.  The parties  hereto  hereby waive any right to a jury trial in
connection with any litigation pursuant to this Registration Rights Agreement.

                  (e)   Titles.  The  titles  used in this  Registration  Rights
Agreement  are  used  for  convenience  only  and  are not to be  considered  in
construing or interpreting this Registration Rights Agreement.

                  (f)   Counterparts.  This  Agreement  may be  executed  in any
number of counterparts,  each of which shall be enforceable  against the parties
actually  executing such  counterpart and all of which together shall constitute
one instrument.

                                     - 12 -







            IN WITNESS WHEREOF, the parties hereto have caused this Registration
Rights Agreement to be duly executed as of the date first above written.


                                   PURCHASERS:

                                   [________________________________]

                                        By: [_______________________]

                                        Its:


                                        By:  _______________________________
                                        Name:
                                        Its:

                                        Address:

                                        Telephone Number:
                                        Facsimile Number:


                                   AMERICAN BIOGENETIC SCIENCES, INC.,
                                   a Delaware corporation


                                   By:    /s/ Josef C. Schoell
                                        ---------------------------
                                        Name: Josef C. Schoell
                                        Title:   Vice President Finance - CFO
                                        Address: 1375 Akron Street, Copiague, NY
                                                 11726
                                        Telephone Number:   (516) 789-2600
                                        Facsimile Number:   (516) 789-1669



                                     - 13 -