EXHIBIT 10.91



                               AGREEMENT REGARDING
                   REGISTRATION RIGHTS AND RELATED OBLIGATIONS

         This Agreement  Regarding  Registration  Rights and Related Obligations
(this  "Agreement")  is  entered  into this _____ day of  _____________,  199__,
between  Interneuron   Pharmaceuticals,   Inc.,  a  Delaware   corporation  (the
"Company"), and Swiss Bank Corporation,  a Swiss banking corporation,  acting by
and through its London Branch ("SBC").

         WHEREAS, on  _______________,  1997, the Company issued to SBC, and SBC
acquired from the Company,  the Call Warrant,  as defined in Section 1.1 hereof,
in  consideration  of a capped  call  option  issued  on that date by SBC to the
Company,  as well as the other  undertakings  and obligations of the Company set
forth in the Call Warrant; and

         WHEREAS,  pursuant to the terms and conditions of the Call Warrant,  on
____________,  199__ or such later date as is  established  pursuant to the Call
Warrant (the "Maturity  Date"),  SBC has the right to purchase from the Company,
and, upon exercise of that right by SBC, the Company has the obligation,  at its
election,  either (i) to sell to SBC, at the exercise  price provided for in the
Call  Warrant,  the number of shares of the Company's  common  stock,  par value
$.001 per share (the "Common  Stock"),  underlying  the Call Warrant  ("Physical
Settlement")  or (ii) to pay to SBC an amount of cash  calculated as provided in
the Call Warrant ("Cash Settlement"); and

         WHEREAS,  pursuant to the terms and conditions of the Call Warrant,  in
the event the Company elects to discharge its obligations thereunder by Physical
Settlement, the Company and SBC shall enter into this Agreement; and

         WHEREAS, the Company has elected to discharge its obligations under the
Call Warrant by Physical Settlement;

         NOW,  THEREFORE,  in  consideration of the foregoing and other good and
valuable consideration, the Company and SBC hereby agree as follows:


                              ARTICLE I DEFINITIONS

         For  purposes of this  Agreement,  the  following  terms shall have the
following meanings:







         1.1 Call  Warrant.  "Call  Warrant"  shall mean the warrant to purchase
Common Stock  issued by the Company to SBC pursuant to the terms and  conditions
of the Confirmation.

         1.2 Commission.  "Commission"  shall mean the United States  Securities
and Exchange Commission or any successor agency thereto.

         1.3 Confirmation.  "Confirmation"  shall mean the confirmation  setting
forth  the  terms of the  Call  Warrant,  together  with  the  Master  Agreement
incorporated therein, dated as of _________________.

         1.4  Exchange  Act.   "Exchange  Act"  shall  mean  the  United  States
Securities Exchange Act of 1934, as amended.

         1.5 Local Business Day.  "Local Business Day" shall mean a day on which
commercial banks are open for business  (including  dealings in foreign exchange
and foreign currency deposits) in New York, New York.

         1.6 Preliminary  Prospectus.  "Preliminary  Prospectus"  shall mean any
preliminary  prospectus,  including  all  documents  incorporated  by  reference
therein,  included in the  Registration  Statement or filed with the  Commission
pursuant to Rule 424(a) of the rules and regulations of the Commission under the
Securities  Act; any reference to any amendment or supplement to the Preliminary
Prospectus shall be deemed to include any documents filed under the Exchange Act
after the date of such  Preliminary  Prospectus  and  incorporated  by reference
therein;  and  any  reference  to  the  Preliminary  Prospectus  as  amended  or
supplemented shall be deemed to include the Preliminary Prospectus as amended or
supplemented  by any such documents  filed under the Exchange Act after the date
of such Preliminary Prospectus and incorporated by reference therein.

         1.7 Prospectus.  "Prospectus" shall mean any prospectus,  including all
documents  incorporated by reference  therein,  (i) included in the Registration
Statement as of the time that the Registration  Statement is declared  effective
or (ii) filed with the Commission in connection with the Registration  Statement
pursuant to Rule 424(b) of the rules and regulations of the Commission under the
Securities  Act; any reference to any amendment or supplement to the  Prospectus
shall be deemed to include any documents  filed under the Exchange Act after the
date of such Prospectus and incorporated by reference therein; and any reference
to the  Prospectus  as amended or  supplemented  shall be deemed to include  the
Prospectus  as amended or  supplemented  by any such  documents  filed under the
Exchange Act after the date of such  Prospectus  and  incorporated  by reference
therein.

         1.8  Registration  Statement.  "Registration  Statement"  shall  mean a
registration  statement on Form S-3 (or any  applicable  successor  form then in
effect;  provided that if, at the time a registration  statement is to be filed,
the Company is not eligible to use Form


                                        2






S-3 or applicable  successor form for a primary  offering by or on behalf of the
Company,  "Registration  Statement" shall mean a registration  statement on such
form as is then  available  to the  Company),  which  is to be  filed  with  the
Commission  pursuant to Section 4.1  hereof,  covering  the resale of the Shares
from time to time, including all exhibits thereto and all documents incorporated
by reference in the Prospectus  contained in such Registration  Statement at the
time it is  declared  effective,  each as amended  at the time the  Registration
Statement is declared effective.

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

         1.10 Shares.  "Shares"  shall mean the shares of Common Stock  issuable
upon exercise of the Call Warrant.

         1.11  Termination  Date.  "Termination  Date"  shall  mean  the  second
anniversary of the Maturity Date.


            ARTICLE II REPRESENTATIONS AND WARRANTIES OF THE COMPANY

         The Company  represents and warrants to SBC that the following are true
and correct as of the date hereof and as of the "Settlement  Date" (as that term
is defined in the Confirmation):

         2.1  Organization  and  Existence of the Company.  The Company has been
duly  incorporated  and is validly  existing as a  corporation  in good standing
under the laws of the State of Delaware, with power and authority (corporate and
other) to own its  properties  and conduct its business as described in the 1934
Act  Reports,  and has been  duly  qualified  as a foreign  corporation  for the
transaction  of business  and is in good  standing  under the laws of each other
jurisdiction in which the ownership or leasing of properties,  or the conduct of
its business requires such qualification, except to the extent the failure to be
so  qualified  would not have a material  adverse  effect on the Company and its
subsidiaries, taken as a whole; and each subsidiary of the Company has been duly
incorporated  and is validly  existing as a corporation  and is in good standing
under the laws of its jurisdiction of incorporation, except where the failure to
be so  would  not  have a  material  adverse  effect  on  the  Company  and  the
subsidiaries taken as a whole.

         2.2  Authorization  of  Transactions  and  Agreement.   The  execution,
delivery and  performance  of this  Agreement  have been duly  authorized by the
board of directors of the Company.  Assuming the due  execution  thereof by SBC,
this  Agreement  constitutes  the legal,  valid and  binding  obligation  of the
Company, enforceable against the Company in accordance with its terms (except as
such  enforceability  may  be  limited  by  applicable  bankruptcy,  insolvency,
reorganization,  moratorium or other laws of general application  relating to or
affecting enforcement of creditors' rights and the application of equitable


                                        3





principles in any action, legal or equitable,  and except as rights to indemnity
or contribution may be limited by applicable law). The Company has the corporate
power to execute and deliver this Agreement and to consummate  the  transactions
contemplated herein.

         2.3 Capitalization. (a) As of __________, 199__, the authorized capital
stock of the Company consists of (i) ___________ shares of Common Stock and (ii)
_________  shares of preferred  stock, par value $.001 per share (the "Preferred
Stock"). As of _______,  199__,  ______________ shares of Common Stock (of which
__________  shares are treasury  shares) and _________ shares of Preferred Stock
were issued and outstanding. In addition, as of __________, 199__, the following
shares of Common  Stock  were  reserved  for  issuance  upon  [SPECIFY  RESERVED
SHARES].

         (b) The  outstanding  shares of Common Stock have been duly and validly
authorized  and  issued  and are fully paid and  non-assessable.  The  Company's
stockholders  have no preemptive  rights with respect to the Shares.  All of the
issued  shares of capital  stock of each  subsidiary  of the  Company  that is a
"significant  subsidiary" (as defined in Rule 12b-2 under the Exchange Act) have
been duly and validly authorized and issued, are fully paid and  non-assessable,
and all such shares that are owned  directly  or  indirectly  by the Company are
owned free and clear of all liens,  encumbrances,  equities or claims, with such
exceptions  as  would  not  have a  material  adverse  effect  on the  Company's
ownership interest in a significant subsidiary.

         (c) The Shares have been duly authorized and, when issued and delivered
upon  exercise of the Call Warrant in accordance  with the terms and  conditions
thereof, will be validly issued, fully paid and nonassessable.

         2.4  SEC  Filings  and  Financial  Statements.   (a)  The  Company  has
heretofore  delivered to SBC copies of the  Company's  (i) Annual Report on Form
10-K for the fiscal year ended [THEN MOST RECENTLY ENDED FISCAL YEAR],  and (ii)
the proxy statement for its 199__ Annual Meeting of Stockholders,  in each case,
substantially   in  the  form  filed  by  the   Company   with  the   Commission
(collectively,  together  with any other reports  filed,  as of the date of this
Agreement,  by the Company under the Exchange Act and the rules and  regulations
of the  Commission  since [TWO YEARS  BEFORE  DATE IN CLAUSE (I)] (the "1934 Act
Reports").  All of the 1934 Act Reports have complied in all material  respects,
as of their  respective  filing dates,  with all applicable  requirements of the
Exchange  Act and the  related  rules and  regulations  thereunder.  As of their
respective  filing  dates,  none of the 1934 Act  Reports  contained  any untrue
statement of a material  fact or omitted to state a material fact required to be
stated therein or necessary to make the statements  therein, in the light of the
circumstances  under  which  they  were  made,  not  misleading.  Any  amending,
correcting or superseding statement made in any subsequent 1934 Act Report shall
be  effective  for this purpose only with respect to the period after the filing
of such subsequent 1934 Act Report.


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         (b) The audited consolidated financial statements and unaudited interim
financial  statements of the Company  contained or  incorporated by reference in
the Company's  1934 Act Reports have been prepared in accordance  with generally
accepted accounting  principles applied on a consistent basis and, together with
the notes thereto,  present fairly the  consolidated  financial  position of the
Company and its subsidiaries at the dates shown and the consolidated  results of
their operations, changes in stockholders' equity and cash flows for the periods
then ended.

         2.5 No  Material  Adverse  Change.  Neither  the Company nor any of its
significant  subsidiaries  has  sustained  since the date of the latest  audited
financial  statements  included or  incorporated  by  reference  in the 1934 Act
Reports  any  material  loss  or  interference  with  its  business  from  fire,
explosion, flood or other calamity, whether or not covered by insurance, or from
any labor dispute or court or governmental  action,  order or decree,  otherwise
than as set forth or contemplated in the 1934 Act Reports. Since the date of the
latest audited financial statements included or incorporated by reference in the
1934 Act Reports, and except as may be set forth or contemplated in the 1934 Act
Reports,  there has not been (i) any material change in the capital stock of the
Company  (other than a change solely  attributable  to, or resulting  from,  the
issuance  of Common  Stock  pursuant to a  director,  officer or employee  stock
option,  benefit  or  compensation  plan),  (ii) any  material  increase  in the
short-term or long-term  consolidated  debt of the Company and its  consolidated
subsidiaries on a consolidated  basis or (iii) any material  adverse change,  or
any development  involving a prospective material adverse change, in the general
affairs,  management,  financial  position,  stockholders'  equity or results of
operations  of the Company and its  subsidiaries,  taken as a whole,  that could
reasonably  be expected to require  disclosure in a primary  public  offering of
Common Stock by the Company under the Securities Act.

         2.6 No Conflicts.  The execution and delivery of this Agreement and the
consummation of the transactions  herein  contemplated will not conflict with or
result  in a breach  or  violation  of any of the  terms or  provisions  of,  or
constitute  a  default   under,   any  indenture,   mortgage,   deed  of  trust,
sale/leaseback  agreement,  loan  agreement,   similar  financing  agreement  or
instrument  or other  agreement or instrument to which the Company or any of its
significant  subsidiaries  is a party  or by  which  the  Company  or any of its
significant  subsidiaries  is bound or to which any of the property or assets of
the Company or any of its significant  subsidiaries is subject,  except for such
conflicts, breaches or violations as would not have a material adverse effect on
the  Company  and its  subsidiaries,  taken as a whole,  or on the  transactions
contemplated by this Agreement or the Confirmation; nor will such actions result
in any  violation of the  provisions  of the  Certificate  of  Incorporation  or
by-laws of the  Company or any statute  applicable  to the Company or any of its
significant subsidiaries or any order, judgment, decree, rule or


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regulation  applicable to the Company or any of its significant  subsidiaries of
any court or governmental agency or body having jurisdiction over the Company or
any of its significant subsidiaries or any of their properties;  and no consent,
approval,  authorization,  order,  registration or  qualification of or with any
such court or  governmental  agency or body is required for the  consummation by
the Company of the transactions  contemplated by this Agreement,  except such as
may be required  under the  Securities Act prior to the resale of Shares and any
such consents, approvals, authorizations, registrations or qualifications as may
be  required  under state  securities  or Blue Sky laws in  connection  with the
resale of Shares.

         2.7 Litigation. Other than as set forth or contemplated in the 1934 Act
Reports,  there are no legal or  governmental  proceedings  pending to which the
Company or any of its  subsidiaries  is a party or of which any  property of the
Company or any of its subsidiaries is the subject which, if determined adversely
to  the  Company  or  any  of its  subsidiaries,  would  individually  or in the
aggregate have a material adverse effect on the consolidated financial position,
stockholders'   equity  or  results  of   operations  of  the  Company  and  its
subsidiaries; and to the Company's knowledge, no such proceedings are threatened
or contemplated by governmental authorities or threatened by others.

         2.8 Independence of Public Accountants. Coopers & Lybrand LLP, who have
audited  certain  financial  statements  of the  Company  and  its  consolidated
subsidiaries,  are independent  public accountants as required by the Securities
Act and  the  Exchange  Act and the  rules  and  regulations  of the  Commission
thereunder.

         2.9  Not an  Investment  Company.  The  Company  is not an  "investment
company" as such term is defined  under the  Investment  Company Act of 1940, as
amended.

         2.10 No  Registration  Rights.  Except as  provided  in  Schedule  2.10
hereto,  or in other  agreements with SBC, no person has any right to request or
demand to have any shares of Common  Stock or other  securities  of the  Company
registered  pursuant  to the  Registration  Statement  or  another  registration
statement pursuant to the Securities Act.

         2.11  Registrant  Requirements  for Form  S-3.  The  Company  meets the
registrant  requirements  of  General  Instruction  I.A.  of Form S-3  under the
Securities Act, as in effect on the date of this Agreement.

                ARTICLE III REPRESENTATIONS AND WARRANTIES OF SBC

         SBC  represents and warrants to the Company that the following are true
and correct as of the date hereof and as of the Settlement Date:


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         3.1  Organization  and  Existence of SBC. SBC is a banking  corporation
organized under the laws of Switzerland, with power and authority (corporate and
other) to own its properties and conduct its business.

         3.2  Authorization  of  Transactions  and  Agreement.   The  execution,
delivery and  performance of this  Agreement  have been duly  authorized by SBC.
Assuming the due execution  thereof by the Company,  this Agreement  constitutes
the legal,  valid and  binding  obligation  of SBC,  enforceable  against SBC in
accordance  with its terms  (except  as such  enforceability  may be  limited by
applicable bankruptcy, insolvency,  reorganization,  moratorium or other laws of
general  application  relating to or affecting  enforcement of creditors' rights
and the application of equitable  principles in any action,  legal or equitable,
and except as rights to indemnity or  contribution  may be limited by applicable
law).  SBC has the corporate  power to execute and deliver this Agreement and to
consummate the transactions contemplated herein.

         3.3 No Conflicts.  The execution and delivery of this Agreement and the
consummation of the transactions  herein  contemplated will not conflict with or
result  in a breach  or  violation  of any of the  terms or  provisions  of,  or
constitute a default under,  any agreement or instrument to which SBC is a party
or by which  SBC is bound or to which  any of the  property  or assets of SBC is
subject,  nor will such action result in any violation of the charter or by-laws
of SBC or any statute or any order, judgment,  decree, rule or regulation of any
court or governmental  agency or body having jurisdiction over SBC or any of its
properties,  except for such conflicts, breaches or violations as would not have
a material adverse effect on the transactions  contemplated by this Agreement or
the Confirmation; and no consent, approval,  authorization,  order, registration
or  qualification  of or with any such court or  governmental  agency or body is
required for the  consummation by SBC of the  transactions  contemplated by this
Agreement,  except such as may be required under the Securities Act prior to the
resale of Shares and any such consents, approvals, authorizations, registrations
or  qualifications as may be required under state securities or Blue Sky laws in
connection with the resale of Shares.


                      ARTICLE IV AGREEMENTS OF THE COMPANY

         The Company  agrees,  with respect to the period  beginning on the date
hereof through and including the earlier of the Termination  Date or the date on
which the Company  receives  written notice from SBC that all of the Shares have
been resold (except that the provisions of Section 4.9 may continue by its terms
after such date), as follows:

         4.1 Filing of  Registration  Statement.  (a) The  Company  has filed or
shall expeditiously file with the Commission a registration statement,  covering
the resale of the Shares from time to time by SBC and such  affiliated  entities
as SBC may designate on


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securities  exchanges or  over-the-counter or in such other lawful manner as SBC
may specify, in a form previously reviewed by SBC.

         (b) If such registration  statement has not yet become  effective,  the
Company  shall use its best  efforts to cause  such  registration  statement  to
become  effective no later than the Maturity Date. The Company shall (i) use its
best efforts to cause such registration  statement to remain in effect until the
earlier  of the  Termination  Date or the date on  which  the  Company  receives
written notice from SBC that all of the Shares have been resold, (ii) inform SBC
promptly upon notice from the  Commission  that the  Registration  Statement has
been declared effective,  (iii) advise SBC promptly of any proposed amendment or
supplement to the  Prospectus  after the effective  date thereof and furnish SBC
with a draft  prior to the filing  thereof,  (iv) for so long as  delivery  of a
prospectus  is required in  connection  with the  offering or sale of any of the
Shares, (A) unless the Company is legally required to so amend or supplement the
Prospectus, make no further amendment or any supplement to the Prospectus (other
than any such  amendment or supplement  resulting  from the filing of reports or
statements  under the  Exchange Act which are  incorporated  by reference in the
Prospectus)  after the effective  date thereof to which SBC  reasonably  objects
within two business days after  receipt of a draft of the proposed  amendment or
supplement  and (B)  file  promptly  all  reports  and any  definitive  proxy or
information  statements  required to be filed by the Company pursuant to Section
13(a),  13(c),  14 or 15(d) of the  Exchange  Act,  (v) during such same period,
advise SBC, promptly after the Company receives notice thereof,  (A) of the time
when any  amendment  to the  Registration  Statement  has been  filed or becomes
effective or any supplement to the Prospectus or any amended Prospectus has been
filed with the  Commission,  (B) of the issuance by the  Commission  of any stop
order  or of any  order  preventing  or  suspending  the  use of any  prospectus
relating to the Shares, (C) of the suspension of the qualification of the Shares
for offering or sale in any  jurisdiction,  (D) of the initiation or threatening
of any proceeding for any such purpose,  or (E) of any request by the Commission
for  the  amending  or  supplementing  of  the  Registration  Statement  or  the
Prospectus or for additional information,  and (vi) in the event of the issuance
of any such stop order or of any such order  preventing or suspending the use of
any prospectus relating to the Shares or suspending any such qualification,  use
promptly its best efforts to obtain the  withdrawal  of such order.  The Company
shall not include in the  Registration  Statement any securities  other than the
Shares.

         4.2  Qualification  of the Shares  under  State  Securities  Laws.  The
Company  shall  promptly  take,  from  time  to  time,  such  action  as SBC may
reasonably  request  to  qualify  the  Shares  for  offering  and sale under the
securities  laws of such of the United  States as SBC may  request and to comply
with such laws so as to permit the continuance of sales and dealings  therein in
such jurisdictions for as long as may be necessary to complete the resale of the
Shares (but not to exceed the period  specified  in the first  paragraph of this
Article IV);  provided that, in connection  therewith,  the Company shall not be
required to

                                        8





qualify  as a foreign  corporation  or to file a general  consent  to service of
process in any jurisdiction.

         4.3 Preparation of Registration  Statement;  Reasonable  Investigation.
The Company shall (a) give SBC, its designated affiliated entities,  counsel and
accountants   the   opportunity  to  participate  in  the   preparation  of  the
Registration  Statement  and,  to the  extent  practicable,  each  amendment  or
supplement thereto and document incorporated by reference therein which is filed
with the Commission after the filing of the Registration Statement, (b) give SBC
and its  representatives  such  reasonable  access  to the  books,  records  and
properties of the Company and its subsidiaries (to the extent  customarily given
to  those  who  are   underwriters   of  the  Company's   securities)  and  such
opportunities  to discuss the  business of the Company with its officers and the
independent public  accountants who have certified its financial  statements and
will have such  officers and  accountants  supply such  information  as shall be
reasonably  requested  by  SBC  or  its  representatives  in  connection  with a
"reasonable investigation" within the meaning of Section 11(b) of the Securities
Act and (c)  furnish  SBC with  copies  of any  press  release  or other  public
announcement  which it intends  to issue,  or any  report or  document  which it
intends to file under the Exchange Act with the  Commission or other  regulatory
agency,  insofar as such press  release,  public  announcement,  report or other
document   regards  this  Agreement  and  the  Call  Warrant   promptly   (where
practicable, at least two business days prior to the proposed issuance or filing
thereof),  and consider in good faith any comments  received from SBC concerning
the timing and content of such press  release,  public  announcement,  report or
other document.

         4.4 Compliance with Applicable Law and Commission Requirements. (a) The
Registration  Statement and Prospectus and all amendments or supplements thereto
shall conform in all material respects to the requirements of the Securities Act
and the rules and regulations of the Commission  thereunder and shall not, as of
the applicable effective date as to the Registration Statement and any amendment
thereto and as of the applicable filing date of the Prospectus and any amendment
or supplement thereto, contain an untrue statement of a material fact or omit to
state a material  fact  required to be stated  therein or  necessary in order to
make the statements made therein,  in the light of the circumstances under which
they were made, not misleading;  provided, however, that this covenant shall not
apply to any  statements  or omissions  made in reliance  upon and in conformity
with information furnished in writing to the Company by SBC expressly for use in
the Prospectus or any amendment or supplement thereto.

         (b) All of the documents  incorporated by reference in the Registration
Statement  and  Prospectus,  or any  amendment or  supplement  thereto,  whether
previously filed with the Commission or filed with the Commission  following the
date hereof,  at their respective  times of filing,  (i) shall have conformed or
shall conform,  as applicable,  in all material  respects to the requirements of
the  Securities  Act or the  Exchange  Act,  as  applicable,  and the  rules and
regulations of the Commission thereunder and (ii) shall not have contained


                                        9





or shall not contain,  as applicable,  an untrue statement of a material fact or
omit to state a material  fact  required to be stated  therein or  necessary  in
order to make the  statements  made therein,  in the light of the  circumstances
under  which  they were  made,  not  misleading;  provided,  however,  that this
representation  and warranty  shall not apply to (A) any statements or omissions
made in reliance upon and in conformity with information furnished in writing to
the Company by or on behalf of SBC  expressly  for use in the  Prospectus or any
amendment or supplement  thereto or (B)  statements or omissions  that have been
superseded or otherwise  corrected by an  amendment,  supplement or other filing
under  the  Exchange  Act  but  only  with  respect  to the  period  after  such
correction.

         4.5  Furnishing of  Prospectuses;  Notice to SBC of Need for Amendment.
The  Company  shall  furnish SBC with copies of the  Prospectus,  including  any
amendments or supplements  thereto,  in such  quantities as SBC may from time to
time reasonably request. If, while the Registration Statement is effective,  the
delivery of a prospectus is required at any time during the period  specified in
the first  paragraph of this Article IV in connection with the offering and sale
of the Shares by SBC and if, at such time,  any event  shall have  occurred as a
result of which the  Prospectus,  including  the  Prospectus  as then amended or
supplemented,  would  include an untrue  statement of a material fact or omit to
state any material fact  necessary in order to make the statements  therein,  in
the light of the  circumstances  under which they were made when such Prospectus
is delivered, not misleading,  or, if for any other reason it shall be necessary
during such same period to amend or supplement  the  Prospectus or to file under
the Exchange Act any document  incorporated  by reference in the  Prospectus  in
order to comply with the  Securities  Act or the Exchange Act, the Company shall
notify SBC in writing and, as promptly as  reasonably  possible,  provided  that
where such report is required  under this  Section 4.5 solely to comply with the
periodic  reporting  provisions  under the Exchange Act, such report need not be
filed sooner than required by such  provisions and no such written notice to SBC
shall be  required,  shall  amend or  supplement  the  Prospectus  or file  such
document so as to correct such  statement or omission or effect such  compliance
and shall  prepare and  furnish to SBC without  charge as many copies as SBC may
from time to time reasonably  request of any amended Prospectus or supplement to
the Prospectus.

         4.6 Listing of the Shares.  The Company  shall use its best  efforts to
have the Shares  approved for quotation on the Nasdaq  National Market or listed
on such other  exchange as the Company Common Stock is listed as of the Maturity
Date.

         4.7 Delivery of Opinion and Comfort  Letter.  On the effective  date of
the Registration  Statement,  the Company shall cause to be furnished to SBC (i)
an opinion or opinions of counsel for the Company, addressed to SBC and dated as
of the effective date of the Registration  Statement,  in substantially the form
of  Exhibit  A hereto,  and (ii) a letter  signed  by  Coopers  &  Lybrand  LLP,
addressed  to  SBC  and  dated  as of the  effective  date  of the  Registration
Statement, in substantially the form set forth in Exhibit B hereto, provided SBC
provides Coopers & Lybrand LLP with an appropriate request.


                                       10





         4.8  Furnishing  of  Additional  Information.  Until the earlier of the
Termination  Date or  completion  of resale of the  Shares,  the  Company  shall
furnish  to SBC  copies of all  reports or other  communications  (financial  or
other) generally  furnished to stockholders  and, as soon as they are available,
copies of any reports and  financial  statements  furnished to or filed with the
Commission or any national  securities exchange on which the Shares or any class
of  securities of the Company are listed (such  financial  statements to be on a
consolidated   basis  to  the  extent  the  accounts  of  the  Company  and  its
subsidiaries are consolidated in reports furnished to its stockholders generally
or to the Commission).

         4.9 Payment of Expenses.  The Company shall pay or cause to be paid the
following: (i) the fees, disbursements and expenses of the Company's counsel and
accountants  in  connection  with the  registration  of the Shares and all other
expenses  in  connection  with  the  preparation,  printing  and  filing  of the
Registration  Statement,  the  Prospectus  and any  amendments  and  supplements
thereto and the mailing and delivering of copies thereof, (ii) any fees incurred
in connection  with any stock exchange  listing or approval for quotation of the
Shares on the Nasdaq National Market,  (iii) all expenses in connection with the
qualification of the Shares for offering and sale under Section 4.2 hereof, (iv)
the cost of preparing  certificates for the Shares,  (v) the cost and charges of
any transfer agent or registrar or dividend disbursing agent, and (vi) all other
costs incident to the performance of the Company's  obligations under Article IV
hereof which are not otherwise  specifically provided for in this Section. It is
understood,  however,  that except as provided in this Section 4.9, SBC will pay
all of its own  costs  and  expenses,  including  the  fees of its  counsel  and
brokerage fees and commissions and transfer taxes on resale of any of the Shares
by SBC.


                           ARTICLE V AGREEMENTS OF SBC

         SBC agrees,  with  respect to the period  beginning  on the date hereof
through and including the Termination Date, as follows:

         5.1 Information  for Use in the Prospectus.  As soon as practicable but
in no event later than the third business day following the receipt of a written
request from the Company,  SBC shall  furnish the Company with such  information
regarding  SBC and its proposed  dispositions  of Shares as the Company may from
time to time reasonably request for use in preparing the Registration  Statement
and Prospectus, including any amendments or supplements thereto.

         5.2 Suspension of Disposition of Shares. Upon receipt of written notice
from the Company  pursuant to Section 4.5 that an event has occurred as a result
of which, or that the Company has discovered that, the Prospectus, including the
Prospectus as then amended or  supplemented,  includes an untrue  statement of a
material fact or omits to state any material fact necessary in order to make the
statements therein, in the light of the


                                       11





circumstances under which they were made, not misleading,  SBC shall immediately
discontinue  disposition of the Shares  pursuant to the  Registration  Statement
until such time as SBC shall have received  copies of an amended or supplemented
Prospectus  or until it receives  notice from the Company that  dispositions  of
Shares may be resumed without amendment or supplementation of the Prospectus.

         5.3 Notice of  Completion.  SBC shall  notify the Company  within three
business days of completion of its disposition of the Shares.

         5.4  Resales of Shares.  SBC agrees  that it will not offer,  transfer,
sell, pledge,  hypothecate or otherwise dispose of any of the Shares (or solicit
any  offers  to buy,  purchase  or  otherwise  acquire  or take a pledge  of any
Shares),  except  in  compliance  with  the  Securities  Act and the  rules  and
regulations  of the Commission  thereunder,  and in compliance  with  applicable
state securities or Blue Sky laws.


                           ARTICLE VI INDEMNIFICATION

         The Company and SBC further agree as follows:

         6.1 Indemnification with Respect to the Registration Statement. (a) The
Company will indemnify and hold harmless SBC against any losses, claims, damages
or liabilities,  joint or several,  to which SBC may become  subject,  under the
Securities Act, the Exchange Act or otherwise,  insofar as such losses,  claims,
damages or liabilities (or actions in respect thereof) arise out of or are based
upon an  untrue  statement  or  alleged  untrue  statement  of a  material  fact
contained in any Preliminary Prospectus,  any preliminary prospectus supplement,
the  Registration  Statement,  the  Prospectus  or any  amendment or  supplement
thereto,  or arise out of or are based upon the omission or alleged  omission to
state therein a material fact required to be stated therein or necessary to make
the  statements  therein,  in light of the  circumstances  under which they were
made,  not  misleading,  and will  reimburse SBC for any legal or other expenses
reasonably  incurred by SBC in connection  with  investigating  or defending any
such action or claim as such expenses are incurred;  provided, however, that the
Company  shall not be liable in any such case to the extent  that any such loss,
claim, damage or liability arises out of or is based upon an untrue statement or
alleged untrue statement or omission or alleged omission made in any Preliminary
Prospectus,  any supplement thereto, the Registration Statement,  the Prospectus
or any amendment or supplement  thereto in reliance upon and in conformity  with
written  information  furnished to the Company by or on behalf of SBC  expressly
for use therein.

         (b) SBC will  indemnify  and hold  harmless  the  Company  against  any
losses,  claims, damages or liabilities to which the Company may become subject,
under the Securities Act, the Exchange Act or otherwise, insofar as such losses,
claims, damages


                                       12




or liabilities (or actions in respect thereof) arise out of or are based upon an
untrue statement or alleged untrue statement of a material fact contained in any
Preliminary Prospectus,  any preliminary prospectus supplement, the Registration
Statement,  the Prospectus and any amendment or supplement thereto, or arise out
of or are  based  upon the  omission  or  alleged  omission  to state  therein a
material fact required to be stated  therein or necessary to make the statements
therein,  in  light  of the  circumstances  under  which  they  were  made,  not
misleading, in each case to the extent, but only to the extent, that such untrue
statement or alleged untrue  statement or omission or alleged  omission was made
in any  Preliminary  Prospectus,  any  preliminary  prospectus  supplement,  the
Registration Statement, the Prospectus or any amendment or supplement thereto in
reliance  upon and in  conformity  with  written  information  furnished  to the
Company by or on behalf of SBC expressly for use therein and will  reimburse the
Company for any legal or other  expenses  reasonably  incurred by the Company in
connection  with  investigating  or  defending  any such action or claim as such
expenses are incurred.

         (c) Promptly after receipt by an indemnified party under subsection (a)
or (b) above of notice of the commencement of any action, such indemnified party
shall,  if a claim in respect  thereof is to be made  against  the  indemnifying
party under such  subsection,  notify the  indemnifying  party in writing of the
commencement thereof; but the omission so to notify the indemnifying party shall
not relieve it from any  liability  which it may have to any  indemnified  party
otherwise than under such  subsection.  In case any such action shall be brought
against any indemnified party and it shall notify the indemnifying  party of the
commencement  thereof,  the indemnifying  party shall be entitled to participate
therein  and,  to the  extent  that  it  shall  wish,  jointly  with  any  other
indemnifying  party  similarly  notified,  to assume the defense  thereof,  with
counsel  satisfactory to such indemnified  party (who shall not, except with the
consent of the indemnified  party, be counsel to the indemnifying  party),  and,
after  notice  from  the  indemnifying  party to such  indemnified  party of its
election so to assume the defense thereof,  the indemnifying  party shall not be
liable to such indemnified party under such subsection for any legal expenses of
other counsel or any other expenses,  in each case subsequently incurred by such
indemnified  party, in connection with the defense thereof other than reasonable
costs of investigation.

         (d)  If  the  indemnification  provided  for  in  this  Section  6.1 is
unavailable  to or  insufficient  to hold  harmless an  indemnified  party under
subsection  (a) or (b)  above in  respect  of any  losses,  claims,  damages  or
liabilities  (or actions 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 the Company on the one hand and SBC 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


                                       13




fact  relates to  information  supplied by the Company on the one hand or SBC on
the other and the parties' relative intent, knowledge, access to information and
opportunity  to correct or prevent such  statement or omission.  The Company and
SBC agree that it would not be just and  equitable if  contribution  pursuant to
this  subsection  (d) 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  subsection  (d).  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  subsection (d) 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.

         (e) The  obligations  of the Company under this Section 6.1 shall be in
addition to any liability which the Company may otherwise have and shall extend,
upon the same terms and  conditions,  to each  "affiliate" (as defined under the
Securities  Act) of SBC,  to each  director  and each  officer of SBC and of its
affiliates,  to each person,  if any, who controls SBC or any of its  affiliates
within the meaning of the Securities  Act; and the obligations of SBC under this
Section 6.1 shall be in addition to any liability  which SBC may otherwise  have
and shall  extend,  upon the same  terms and  conditions,  to each  officer  and
director of the Company and to each  person,  if any,  who  controls the Company
within the meaning of the Securities Act.


                               ARTICLE VII GENERAL

         7.1 Notices.  (a) Any notice or other  communication in respect of this
Agreement  may be given in any manner set forth  below to the  address or number
specified in paragraph  (b) of this Section 7.1 and will be deemed  effective as
indicated:  (i) if in writing and delivered in person or by courier, on the date
it is  delivered;  (ii) if sent by  facsimile  transmission,  on the  date  that
transmission  is received by a responsible  employee of the recipient in legible
form (it being  agreed that the burden of proving  receipt will be on the sender
and will not be met by a transmission report generated by the sender's facsimile
machine);  or (iii) if sent by certified or  registered  mail or the  equivalent
(return receipt  requested),  on the date that mail is delivered or its delivery
is attempted;  unless that delivery (or attempted  delivery) or that receipt, as
applicable, is not on a Local Business Day or occurs after the close of business
on a Local  Business  Day, in which case that notice or  communication  shall be
deemed given and effective on the first  following day that is a Local  Business
Day.

         (b)  Notices  shall be  given to the  addresses  or  facsimile  numbers
reflected below:


                                       14





If to SBC, to:                      Swiss Bank Corporation, London Branch
                                    c/o SBC Warburg Inc.
                                    141 West Jackson Boulevard
                                    Chicago, Illinois 60604

                                    Attention:       Legal Department
                                    Facsimile:       (312) 554-5734
                                    Telephone:       (312) 554-5376

If to the Company, to:              Interneuron Pharmaceuticals, Inc.
                                    99 Heyden Ave.
                                    Lexington, MA 02173

                                    Attention:       Chief Financial Officer
                                    Facsimile:       617-674-2448
                                    Telephone:       617-861-8444

         (c)  Either  party may by notice to the other  change  the  address  or
facsimile number at which notices or other communications are to be given to it.

         7.2 Entire Agreement.  This Agreement,  together with the Confirmation,
constitute the entire agreement and understanding of the parties with respect to
their subject  matter and supersede all oral  communications  and prior writings
with respect thereto.

         7.3  Governing  Law and  Jurisdiction.  (a)  This  Agreement  shall  be
governed by and construed in accordance with New York law (without  reference to
choice of law doctrine).

         (b) With respect to any suit,  action or  proceedings  relating to this
Agreement   ("Proceedings"),   each  party   irrevocably   (i)  submits  to  the
non-exclusive jurisdiction of the courts of the State of New York and the United
States  District Court located in the Borough of Manhattan in New York City, and
(ii) waives any  objection  which it may have at any time to the laying of venue
of any  Proceedings  brought  in any such  court,  waives  any  claim  that such
Proceedings  have been brought in an  inconvenient  forum and further waives the
right to object, with respect to such Proceedings, that such court does not have
any  jurisdiction  over such party.  Nothing in this Agreement  precludes either
party from bringing Proceedings in any other jurisdiction, nor will the bringing
of  Proceedings  in any one or  more  jurisdictions  preclude  the  bringing  of
Proceedings in any other jurisdiction.

         (c) SBC hereby appoints Swiss Bank  Corporation,  New York Branch,  222
Broadway, New York, New York 10038, Attention: Legal Affairs, to receive, for it
and  on  its  behalf,  service  of  process  of  any  Proceedings.  The  parties
irrevocably consent to


                                       15





service of process  given in the manner  provided  for  notices in Section  7.1.
Nothing in this Agreement will affect the right of either party to serve process
in any other manner permitted by law.

         7.4 Amendments  and Waivers.  No amendment,  modification  or waiver in
respect of this Agreement  shall be effective  unless in writing and executed by
each of the  parties.  A failure  or delay in  exercising  any  right,  power or
privilege  in respect of this  Agreement  shall not be presumed to preclude  any
subsequent or further exercise of that right, power or privilege or the exercise
of any other right, power or privilege.

         7.5 Remedies Cumulative.  The rights,  powers,  remedies and privileges
provided in this  Agreement  are  cumulative  and not  exclusive  of any rights,
powers, remedies and privileges provided by law.

         7.6 Headings.  The headings used in this Agreement are for  convenience
of  reference  only and shall not affect the  construction  of, or be taken into
consideration in interpreting, this Agreement.

         7.7 No  Third-Party  Beneficiaries.  Except as  expressly  provided  in
Section  6.1(e),  nothing in this Agreement is intended or shall be construed to
confer upon any person other than the parties hereto any right,  remedy or claim
under or by reason of this Agreement.

         7.8  Survival.   The  representations,   warranties,   indemnities  and
agreements  contained in this  Agreement  shall remain in full force and effect,
regardless of any  investigation by or on behalf of any party, and shall survive
delivery of the Shares to SBC and resale of the Shares by SBC or any  affiliated
entity.

         7.9  Counterparts.  This  Agreement  may be  executed  in  one or  more
counterparts  with the same effect as if the signatures to each counterpart were
upon the same instrument.

         7.10  Assignability.  This  Agreement is not assignable by either party
without the prior  written  consent of the other;  provided that the Company may
assign this  Agreement to a successor in interest  pursuant to a transfer of all
or substantially all of its assets or pursuant to a consolidation or merger.



                                       16





         IN WITNESS WHEREOF,  Interneuron  Pharmaceuticals,  Inc. and Swiss Bank
Corporation,  London Branch, have executed this Agreement as of the day and year
first written above.


                                         INTERNEURON PHARMACEUTICALS, INC.


                                         By:    ___________________________
                                         Title: ___________________________


                                         SWISS BANK CORPORATION,
                                         LONDON BRANCH


                                         By:   ___________________________ 
                                         Title:___________________________ 
                                               

                                         By:   ___________________________ 
                                         Title:___________________________ 
                                               


                                       17




                                                                       EXHIBIT A

                           Form of Opinion of Counsel
                    In Connection With Registration Statement


         Counsel reasonably  satisfactory to SBC shall have furnished to SBC his
or  their  written  opinion,  dated  the  effective  date  of  the  Registration
Statement,  in form and substance reasonably  satisfactory to SBC, to the effect
that:

         (i) The Company has been duly incorporated and is validly existing as a
corporation  in good  standing  under  the laws of the State of  Delaware,  with
corporate  power and authority to own its properties and conduct its business as
described  in the  prospectus;  and each  subsidiary  of the  Company  that is a
"significant  subsidiary"  (as defined in Rule 12b-2 under the Exchange Act) has
been duly  incorporated  and is validly existing as a corporation and is in good
standing under the laws of its jurisdiction of  incorporation,  except where the
failure to be so would not have a material adverse effect on the Company and its
significant subsidiaries taken as a whole;

         (ii) The Company has been duly qualified as a foreign  corporation  for
the  transaction  of  business  and is in good  standing  under the laws of each
jurisdiction  other than the State of Delaware in which the ownership or leasing
of its properties, or the conduct of its business,  requires such qualification,
except to the extent the failure to be so  qualified in any  jurisdiction  would
not  have  a  material  adverse  effect  on  the  Company  and  its  significant
subsidiaries taken as a whole (such counsel being entitled to rely in respect of
the  opinion in this clause  upon  opinions  of local  counsel and in respect of
matters of fact upon certificates of officers of the Company, provided that such
counsel  shall state that they believe  that both SBC and they are  justified in
relying upon such opinions and certificates);

         (iii) The  Company's  authorized  capital  stock  conforms  as to legal
matters  in all  material  respects  to the  description  thereof  set  forth or
incorporated  by reference in the  Prospectus,  and all of the issued  shares of
capital stock of the Company  (including the Shares delivered in exercise of the
Call Warrant and registered for resale pursuant to the  Registration  Statement)
have  been  duly and  validly  authorized  and  issued  and are  fully  paid and
non-assessable;  all of the issued  shares of capital  stock of the  significant
subsidiaries  held  directly or  indirectly  by the  Company  have been duly and
validly  authorized  and  issued,  are fully  paid and  non-assessable;  and the
Company's  stockholders  have no  preemptive  rights with  respect to the Shares
delivered in exercise of the Call Warrant (such  counsel being  entitled to rely
in respect of the opinion in this clause upon  opinions of local  counsel and in
respect of matters of fact upon  certificates  of officers of the Company or its
subsidiaries, provided that such counsel shall state that they believe that both
SBC and they are justified in relying upon such opinions and certificates);






         (iv) To the best of such  counsel's  knowledge  and  other  than as set
forth or  incorporated  by  reference in the  Prospectus,  there are no legal or
governmental  proceedings pending to which the Company or any of its significant
subsidiaries  is a party or of which any  property  of the Company or any of its
significant  subsidiaries is the subject which,  if determined  adversely to the
Company or any of its  significant  subsidiaries,  would  individually or in the
aggregate  have  a  material   adverse   effect  on  the  business   operations,
consolidated  financial position,  shareholders' equity or results of operations
of the Company and its significant subsidiaries,  taken as a whole; and, to such
counsel's  knowledge,   no  such  proceedings  are  threatened  by  governmental
authorities  or  threatened by others,  provided that such counsel  expresses no
opinion on any such  matter  relating to the U.S.  Food and Drug  Administration
("FDA");

         (v) The documents  incorporated  by reference in the Prospectus  (other
than the financial statements, related schedules and other financial information
therein, as to which such counsel need express no opinion), when they were filed
with  the  Commission  complied  as to form in all  material  respects  with the
requirements of the Exchange Act and the rules and regulations of the Commission
thereunder; and

         (vi) The  Registration  Statement  and the  Prospectus  (other than the
financial statements, related schedules and other financial information therein,
as to which  such  counsel  need  express no  opinion)  comply as to form in all
material  respects with the requirements of the Securities Act and the rules and
regulations  thereunder;  and such  counsel do not know of any  amendment to the
Registration  Statement required to be filed or any contracts or other documents
of a character required to be filed as an exhibit to the Registration  Statement
or required to be  incorporated  by reference into the Prospectus or required to
be described in the Registration Statement or the Prospectus which are not filed
or incorporated by reference or described as required.

         In  addition to the matters  set forth  above,  the opinion  shall also
contain a statement to the effect that while such counsel are not passing  upon,
and do not assume responsibility for, the accuracy,  completeness or fairness of
the   Registration   statement  or  the  Prospectus,   including  the  documents
incorporated by reference therein, based upon the procedures referred to in such
opinion  nothing has come to the  attention of such  counsel  which leads him or
them to believe (i) that the Registration  Statement as of its effective date or
the  Prospectus  as of its date (other than the  financial  statements,  related
schedules and other financial  information therein as to which such counsel need
express no belief)  contains an untrue  statement of a material fact or omits to
state a material  fact  required to be stated  therein or  necessary to make the
statements  therein,  in light of the circumstances  under which they were made,
not  misleading or (ii) that any of the documents  incorporated  by reference in
the Prospectus which were filed with the Commission prior to such effective time
(other than the financial  statements,  related  schedules  and other  financial
information therein, as to which such counsel need express no belief), as of the
respective dates when they were filed with the Commission in each


                                        2




case  after  excluding  any  statement  in any  such  document  which  does  not
constitute part of the Registration Statement or the Prospectus pursuant to Rule
412 of Regulation C under the Securities Act and after substituting therefor any
statement modifying or superseding such excluded statement,  contained an untrue
statement of a material  fact or omitted to state a material  fact  necessary in
order to make the statements  therein,  in the light of the circumstances  under
which they were made when such documents were so filed, not misleading, provided
in each case that such counsel expresses no opinion as to FDA or patent matters.



                                        3