<PAGE>

                                                                   Exhibit 10.21

                                LICENSE AGREEMENT

                                 by and between

                             HEAVENLYDOOR.COM, INC.

                                       and

                        INTERNEURON PHARMACEUTICALS, INC

                                      dated

                                  June 14, 2000



<PAGE>

<TABLE>
<CAPTION>
<S>                                                                                                           <C>
Article I         DEFINITIONS....................................................................................1

Article II        LICENSE; SUBLICENSES...........................................................................5
         2.1.     License Grant..................................................................................5
         2.2.     Improvements by Interneuron....................................................................5
         2.3.     Sublicenses....................................................................................5

Article III       DEVELOPMENT AND COMMERCIALIZATION..............................................................5
         3.1.     Exchange of Information........................................................................5
         3.2.     Diligence; Development and Commercialization...................................................6
         3.3.     Regulatory Matters.............................................................................6
         3.4.     Trademark......................................................................................6
         3.5.     Manufacturing..................................................................................6
         3.6.     Adverse Events.................................................................................6
         3.7.     Third Party Agreements.........................................................................6

Article IV        CONFIDENTIALITY AND PUBLICITY..................................................................6
         4.1.     Non-Disclosure and Non-Use Obligations.........................................................7
         4.2.     Permitted Disclosure of Proprietary Information................................................7

Article V         PAYMENTS; ROYALTIES AND REPORTS................................................................8
         5.1.     License Fee....................................................................................8
         5.2.     Milestone Payments.............................................................................8
         5.3.     Royalties; Royalty Buy-Out Option..............................................................9
         5.4.     Royalty Buy-Out Option........................................................................11
         5.5.     Payments from Sublicensee.....................................................................12
</TABLE>

<PAGE>

<TABLE>
<CAPTION>
<S>                                                                                                           <C>
         5.6.     Reports; Payment of Royalty...................................................................12
         5.7.     Audits........................................................................................13
         5.8.     Payment Exchange Rate.........................................................................14
         5.9.     Tax Withholding...............................................................................14
         5.10.    Interest on Late Payments.....................................................................14
         5.11.    Exchange Controls.............................................................................14

Article VI        REPRESENTATIONS AND WARRANTIES................................................................15
         6.1.     HDCI Representations and Warranties...........................................................15
         6.2.     Warranty Disclaimer...........................................................................16
         6.3.     Investment Representations....................................................................16
         6.4.     Interneuron Representations and Warranties....................................................17

Article VII       PATENT MATTERS................................................................................18
         7.1.     Filing, Prosecution and Maintenance of Patent Applications or Patents.........................18
         7.2.     Patent Office Proceedings.....................................................................18
         7.3.     Enforcement and Defense.......................................................................19
         7.4.     Patent Term Extensions and Supplemental Protection Certificates...............................20

Article VIII      TERM AND TERMINATION..........................................................................20
         8.1.     Term and Expiration...........................................................................20
         8.2.     Termination by Notice.........................................................................20
         8.3.     Termination...................................................................................21
         8.4.     Effect of Expiration or Termination...........................................................22

Article IX        MISCELLANEOUS.................................................................................23
</TABLE>

<PAGE>

<TABLE>
<CAPTION>
<S>                                                                                                           <C>
         9.1.     Force Majeure.................................................................................23
         9.2.     Assignment....................................................................................23
         9.3.     Severability..................................................................................23
         9.4.     Notices.......................................................................................23
         9.5.     Applicable Law................................................................................24
         9.6.     Dispute Resolution............................................................................24
         9.7.     Entire Agreement..............................................................................24
         9.8.     Independent Contractors.......................................................................25
         9.9.     Waiver........................................................................................25
         9.10.    Headings......................................................................................25
         9.11.    Counterparts..................................................................................25

</TABLE>

<PAGE>

                                LICENSE AGREEMENT

         THIS LICENSE AGREEMENT effective as of June 14, 2000 ("Effective
Date"), by and between HEAVENLYDOOR.COM, INC. (formerly Procept, Inc.), a
corporation organized and existing under the laws of the State of Delaware and
having its principal office at 1180 Avenue of the Americas, Suite 1447, New
York, New York 10036 ("HDCI") and INTERNEURON PHARMACEUTICALS, INC., a
corporation organized and existing under the laws of the State of Delaware and
having its principal office at 99 Hayden Avenue, Suite 200, Lexington
Massachusetts 02421 ("Interneuron").

                              W I T N E S S E T H:

         WHEREAS, HDCI is the owner of the Patent Assets and HDCI Know-How, as
defined herein;

         WHEREAS, Interneuron desires to obtain exclusive worldwide license
rights, with a right to grant sublicenses, under the Patent Assets and HDCI
Know-How, and HDCI desires to grant such license to Interneuron, upon the terms
and conditions set forth herein;

         NOW, THEREFORE, in consideration of the foregoing premises and the
mutual covenants herein contained, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
Parties hereby agree as follows:

                                   ARTICLE I
                                   DEFINITIONS

         Unless specifically set forth to the contrary herein, the following
terms, where used in the singular or plural, shall have the respective meanings
set forth below:

1.1.   "1933 ACT" means the Securities Act of 1933, and the rules and
       regulations promulgated thereunder, or any successor act, all as the same
       shall be in effect at the time.

1.2.   "AFFILIATE" shall mean (i) any corporation or business entity of which
       more than fifty percent (50%) of the securities or other ownership
       interests representing the equity, the voting stock or general
       partnership interest are owned, controlled or held, directly or
       indirectly, by a Party; (ii) any corporation or business entity which,
       directly or indirectly, owns, controls or holds more than fifty percent
       (50%) (or the maximum ownership interest permitted by law) of the
       securities or other ownership interests representing the equity, voting
       stock or general partnership interest, of a Party or (iii) any
       corporation or business entity of which a Party has the right to acquire,
       directly or indirectly, at least fifty percent (50%) of the securities or
       other ownership interests representing the equity, voting stock or
       general partnership interest thereof.

1.3.   "BUSINESS DAY" means any day that is not a Saturday or a Sunday or a day
       on which the New York Stock Exchange is closed.

<PAGE>

1.4.   "CALENDAR QUARTER" shall mean the respective periods of three (3)
       consecutive calendar months ending on March 31, June 30, September 30 and
       December 31.

1.5.   "CALENDAR YEAR" shall mean each successive period of twelve (12) months
       commencing on January 1 and ending on December 31.

1.6.   "COMPOUND" shall mean a condensation polymer of an aromatic sulfonic acid
       and an aldehyde or a pharmaceutically acceptable salt or prodrug thereof
       or a derivative, homolog, or analog thereof.

1.7.   "COST OF GOODS SOLD" shall mean all direct and indirect manufacturing
       costs incurred by Interneuron or its Affiliates specifically allowable to
       and directly attributable to the production of Compound or Product
       calculated in accordance with GAAP.

1.8.   "EFFECTIVE DATE" shall mean the date first above written.

1.9.   "FAIR MARKET VALUE" shall mean the average closing price for Interneuron
       Stock, as quoted by Nasdaq, for the ten consecutive trading days
       preceding the Election Date.

1.10.  "FDA" shall mean the United States Food and Drug Administration and any
       successor agency having substantially the same functions.

1.11.  "FIRST COMMERCIAL SALE" shall mean, with respect to Product, the first
       sale for end use or consumption of such Product in any country in the
       Territory after all required approvals, including marketing and pricing
       approvals, have been granted by the governing health authority of such
       country or, where government approval is not required, the first sale in
       that country in connection with the nationwide introduction of Product in
       that country by Interneuron, its Affiliates or sublicensees.

1.12.  "GAAP" means generally accepted accounting principles in the United
       States.

1.13.  "HDCI KNOW-HOW" shall mean any and all information and materials,
       including but not limited to, discoveries, information, Improvements,
       processes, formulas, data, inventions, know-how and trade secrets,
       patentable or otherwise, (other than Patent Assets) which

              (a)    relate to Compound or Product; and

              (b)    which are in HDCI's possession or control and as to which
                     HDCI has the right to license or sublicense to third
                     parties, and are necessary or useful in connection with the
                     rights granted and activities contemplated under this
                     Agreement.

       Such know-how shall include, without limitation, all chemical,
       pharmaceutical, toxicological, preclinical, clinical, assay control,
       manufacturing, regulatory, and any other information used or useful for
       the development, manufacturing and/or regulatory approval of Compound or
       Product, including any data included in or generated as a result of or
       under an IND.

<PAGE>

1.14.  "IMPROVEMENT" shall mean any enhancement in the manufacture, formulation,
       ingredients, preparation, presentation, means of delivery or
       administration, dosage, indication, use or packaging of Compound or
       Product.

1.15.  "IND" shall mean an investigational new drug application and any
       supplements and additions thereto relating to the use of Compound or
       Product.

1.16.  "INTERNEURON STOCK" shall mean common stock, $.001 par value, of
       Interneuron.

1.17.  "MRC" shall mean the British Medical Research Council or any successor
       agency having substantially the same functions.

1.18.  "MRC 1996 AGREEMENT" shall mean the Agreement between MRC and HDCI dated
       October 7, 1996 and any amendments thereto.

1.19.  "MRC 1999 AGREEMENT" shall mean the Agreement between MRC and HDCI dated
       February 20, 1999 and any amendments thereto.

1.20.  "NASDAQ" shall mean the Nasdaq National Market segment of the Nasdaq
       Stock Market, or if the Interneuron Stock is not listed on the National
       Market, than Nasdaq shall mean the Nasdaq SmallCap Market.

1.21.  "NDA" shall mean a new drug application filed with the FDA for marketing
       authorization of a Product in the United States.

1.22.  "NET SALES" shall mean the actual gross amount invoiced for the sale of
       Product (except as provided in Section 5.3.1(b)(iii)) commencing upon the
       date of First Commercial Sale by Interneuron, its Affiliates or its
       sublicensees to the first Third Party after deducting in accordance with
       GAAP, if not previously deducted from the amount invoiced:

              (a)    trade, cash, promotional and quantity discounts;

              (b)    recalls, credits and allowances on account of returned or
                     rejected products including, but not limited to, allowance
                     for breakage and spoilage;

              (c)    rebates and chargebacks;

              (d)    retroactive price reductions;

              (e)    sales or excise taxes, VAT or other taxes, transportation
                     and insurance charges and additional special
                     transportation, custom duties, and other governmental
                     charges; and

              (f)    reserves for bad debts or allowances, credits or rebates
                     not covered by (a) through (e) above.

1.23.  "NIH" shall mean the United States National Institutes of Health, or any
       successor agency

<PAGE>

       having substantially the same functions.

1.24.  "OPERATING PROFIT" shall mean the Net Sales received by Interneuron or
       its Affiliates for Compound or Product, less Cost of Goods Sold, selling,
       distribution and inventory management costs and other costs related to or
       allocable to the achievement of Net Sales and determined in accordance
       with GAAP.

1.25.  "PARTY" shall mean HDCI or Interneuron.

1.26.  "PATENT ASSETS" shall mean any and all issued United States and foreign
       patents, patent applications and foreign counterparts thereof (which
       shall be deemed to include certificates of invention and applications for
       certificates of invention) which

              (a)    as of the Effective Date or at any time during the term of
                     this Agreement are owned by HDCI or which HDCI through
                     license or otherwise has or acquires rights (and is not
                     prohibited from sublicensing to third parties), and

              (b)    relate in any way to Compound, Product or any Improvement,
                     including but not limited to compositions of Compound
                     and/or Product, methods of their manufacture, or any uses
                     thereof, including all certificates of invention,
                     divisions, continuations, continuations-in-part, reissues,
                     renewals, extensions, supplementary protection certificates
                     or the like of any such patents, patent applications and
                     foreign counterparts thereof, including but not limited to
                     the patents, patent applications and foreign counterparts
                     thereof listed on Schedule 1.26 hereto, and including
                     domestic and foreign patents, patent applications and
                     foreign counterparts thereof covering any Improvements made
                     by HDCI.

1.27.  "PRODUCT" shall mean any product in final form for commercial sale by
       prescription, over-the-counter, or by any other method, which contains
       Compound in any dosage form as an active ingredient.

1.28.  "PROPRIETARY INFORMATION" shall mean any and all scientific, clinical,
       regulatory, marketing, financial and commercial information or data,
       whether communicated in writing, orally or by any other means, which is
       provided by one Party to the other Party in connection with this
       Agreement.

1.29.  "ROYALTY YEAR" shall mean each successive twelve (12) month period
       commencing with the first day of the first month in which occurs the
       First Commercial Sale.

1.30.  "SEC" means the United States Securities and Exchange Commission.

1.31.  "TERRITORY" shall mean all of the countries in the world.

1.32.  "THIRD PARTY(IES)" shall mean a person or entity who or which is neither
       a Party nor an Affiliate

<PAGE>

       of a Party.

1.33.  "VALID CLAIM" means a claim of an issued and unexpired patent included
       within the Patent Assets, which has not been revoked or held
       unenforceable or invalid by a decision of a court or other governmental
       agency of competent jurisdiction, unappealable or for which an appeal has
       not been filed within the time allowed for appeal, and which has not been
       disclaimed, denied or admitted to be invalid or unenforceable through
       reissue or disclaimer or otherwise.

                                   ARTICLE II
                              LICENSE; SUBLICENSES

2.1.   LICENSE GRANT. HDCI hereby grants to Interneuron an exclusive (even as to
       HDCI), license under the Patent Assets and HDCI Know-How, including the
       right to grant sublicenses, to develop, make, have made, use, import,
       offer for sale, market and sell and otherwise dispose of Compound and
       Product, including any Improvements thereto, in the Territory.

2.2.   IMPROVEMENTS BY INTERNEURON. Title to any general technology or
       Improvement developed or discovered by Interneuron in connection with the
       license granted under Section 2.1 above shall be vested solely in
       Interneuron.

2.3.   SUBLICENSES.

              (a)    Interneuron shall have the right to grant sublicenses to
                     Third Parties to develop, make, have made, use, import,
                     market, sell, have sold, offer to sell and import Compound
                     and Product in the Territory. Any sublicense by Interneuron
                     of the rights granted to Interneuron in this Article 2
                     shall not be inconsistent with the terms of this Agreement
                     and shall include an obligation for the sublicensee to
                     comply with the provisions of Article 4 of this Agreement.
                     Interneuron shall promptly provide HDCI with a fully
                     executed copy of any sublicense agreement.

              (b)    Upon termination of this Agreement by Interneuron, HDCI
                     shall accept assignment of sublicenses, provided that:

                     (i)    the sublicensee is not in breach of its sublicense
                            agreement at the time of termination of this
                            Agreement; and

                     (ii)   the sublicensee acquires no rights from or
                            obligations on the part of HDCI, other than those
                            that are specifically granted in this Agreement, and
                            the sublicensee assumes all obligations to HDCI
                            required of Interneuron by this Agreement.

                                  ARTICLE III
                        DEVELOPMENT AND COMMERCIALIZATION

<PAGE>

3.1.   EXCHANGE OF INFORMATION. Upon execution of this Agreement, HDCI shall
       disclose to Interneuron in writing all HDCI Know-How and Patent Assets
       not previously disclosed to Interneuron. During the term of this
       Agreement, HDCI shall also promptly disclose to Interneuron in writing on
       an ongoing basis all HDCI Know-How and Patent Assets.

3.2.   DILIGENCE; DEVELOPMENT AND COMMERCIALIZATION. Interneuron shall use
       commercially reasonable efforts to develop and commercialize Product. As
       used herein, "commercially reasonable efforts" shall mean efforts and
       resources normally used by Interneuron for a product owned by it or to
       which it has exclusive rights, which is of similar market potential at a
       similar stage in its development or product life, taking into account
       issues of safety and efficacy, product profile, the competitiveness of
       the marketplace, the proprietary position of the compound or product, the
       regulatory and reimbursement structure involved, the profitability of the
       applicable products, and other relevant factors.

       Interneuron will be responsible for all remaining preclinical
       development, toxicology and clinical development, including regulatory
       filings, which are required for commercialization of Product in the
       Territory. Interneuron shall notify HDCI upon the receipt of regulatory
       approvals and of the date of First Commercial Sale.

       Except as specifically set forth in Schedule 3.7 hereof, Interneuron
       shall be responsible for all costs attributable to the development and
       commercialization of Compound and Product which are incurred after the
       Effective Date; provided that with respect to agreements entered into by
       HDCI relating to Compound or Product prior to the Effective Date,
       Interneuron shall be responsible only for the costs under those
       agreements referred to in Schedule 3.7 hereof.

3.3.   REGULATORY MATTERS. Interneuron shall own, control and retain primary
       legal responsibility for the preparation, filing and prosecution of all
       filings and regulatory applications required to obtain authorization to
       commercially develop, sell and use Product in each country in the
       Territory. HDCI shall transfer to Interneuron as soon as practicable
       after the Effective Date (but in no event later than 30 days) any IND or
       other regulatory filings relating to Compound or Product owned by HDCI
       and HDCI shall use its best efforts to allow Interneuron to cross
       reference any other IND or Drug Master File relating to Compound or
       Product to the extent HDCI is legally able to do so.

3.4.   TRADEMARK. Interneuron shall select, own and maintain trademarks for
       Product.

3.5.   MANUFACTURING. Interneuron shall be responsible for manufacture of the
       Compound and Product.

3.6.   ADVERSE EVENTS. HDCI shall promptly furnish to Interneuron all
       information concerning safety or utility of Compound or Product, such as
       adverse or unexpected side effects, injury or other events associated
       with uses, studies, investigations or tests of Compound or Product,
       whether or not HDCI is required to report such information to any
       regulatory authority and whether or not such event is determined to be
       attributable to Compound or Product.

3.7.   THIRD PARTY AGREEMENTS. Agreements entered into by HDCI with third
       parties prior to the

<PAGE>

       Effective Date relating to the Compound or Product shall be handled in
       accordance with Schedule 3.7.

                                   ARTICLE IV
                          CONFIDENTIALITY AND PUBLICITY

4.1.   NON-DISCLOSURE AND NON-USE OBLIGATIONS. All Proprietary Information
       disclosed by one Party to the other Party hereunder shall be maintained
       in confidence and shall not be disclosed to any Third Party or used for
       any purpose except as expressly permitted herein without the prior
       written consent of the Party that disclosed the Proprietary Information
       to the other Party. The foregoing non-disclosure and non-use obligations
       shall not apply to the extent that such Proprietary Information:

              (a)    is known by the receiving Party at the time of its receipt,
                     and not through a prior disclosure by the disclosing Party,
                     as documented by business records;

              (b)    is properly in the public domain;

              (c)    is subsequently disclosed to a receiving Party by a Third
                     Party who may lawfully do so and is not under an obligation
                     of confidentiality to the disclosing Party; or

              (d)    is developed by the receiving Party independently of
                     Proprietary Information received from the other Party, as
                     documented by research and development records.

4.2.   PERMITTED DISCLOSURE OF PROPRIETARY INFORMATION. Notwithstanding Section
       4.1, a Party receiving Proprietary Information of another Party may
       disclose such Proprietary Information:

              (a)    to governmental or other regulatory agencies in order to
                     obtain patents subject to this Agreement, or to gain
                     approval to conduct clinical trials or to market Product,
                     but such disclosure may be only to the extent reasonably
                     necessary to obtain such patents or authorizations;

              (b)    by each of Interneuron or HDCI to its respective agents,
                     consultants, Affiliates, Interneuron's sublicensees and/or
                     other Third Parties for the research and development,
                     manufacturing and/or marketing of the Compound and/or
                     Product (or for such parties to determine their interests
                     in performing such activities) on the condition that such
                     Third Parties agree to be bound by the confidentiality
                     obligations contained in this Agreement; or

              (c)    if required to be disclosed by law or court order, provided
                     that notice is promptly delivered to the non-disclosing
                     Party in order to provide an opportunity to challenge or
                     limit the disclosure obligations; PROVIDED, HOWEVER,
                     without limiting any of the foregoing, it is understood
                     that either Party or its Affiliates may make disclosure of
                     this Agreement and the terms hereof in

<PAGE>

                     any filings required by the SEC, may file this Agreement as
                     an exhibit to any filing with the SEC and may distribute
                     any such filing in the ordinary course of its business
                     provided that certain financial and other confidential
                     terms are redacted from such filings to the extent
                     possible, in consultation with the other Party.

              (d)    Neither Party shall use the name of the other Party in any
                     publicity or advertising without the prior written approval
                     of the other Party. Upon execution of this Agreement, the
                     Parties may issue a press release in the form attached as
                     Appendix 4.2(d).

                                   ARTICLE V
                         PAYMENTS; ROYALTIES AND REPORTS

5.1.   LICENSE FEE. Subject to the terms and conditions contained in this
       Agreement, Interneuron shall pay HDCI a fee equal to $500,000 within ten
       (10) days following the Effective Date.

5.2.   MILESTONE PAYMENTS. Subject to the terms and conditions contained in this
       Agreement, Interneuron shall pay HDCI the following milestone payments,
       each milestone payment to be made no more than once with respect to the
       achievement of each such milestone for Compound:

              (a)    $[*] upon initiation of any Phase 2 safety clinical trial
                     in populations at risk for HIV infection or other sexually
                     transmitted diseases by the MRC, NIH or other governmental
                     or non-commercial sponsor which (i) is useful for FDA
                     approval, and (ii) conforms with the guidelines set forth
                     in Appendix 5.2(a), and for which the MRC, NIH or other
                     governmental or non-commercial sponsor agrees to provide
                     funding to cover at least [*] percent ([*] %) of the costs
                     of the clinical trial (excluding the costs of the supply of
                     Compound and any costs for required regulatory filings),
                     provided that if the MRC, NIH or other governmental or
                     non-commercial sponsor agrees to provide less than [*]
                     percent ([*] %) of such costs, the payment to HDCI
                     hereunder shall be reduced by the amount of funding for
                     such study provided by Interneuron (excluding the costs of
                     the supply of Compound and any costs for required
                     regulatory filings); and

              (b)    $[*] upon initiation of any Phase 3 efficacy clinical trial
                     or the Phase 3 portion of any Phase 2/3 clinical trial in
                     populations at risk for HIV infection or other sexually
                     transmitted diseases by the MRC, NIH or other governmental
                     or non-commercial sponsor which (i) is useful for FDA
                     approval, and (ii) conforms with the guidelines set forth
                     in Appendix 5.2(b), and for which the MRC, NIH or other
                     governmental or non-commercial sponsor agrees to provide
                     funding to cover at least [*] percent ([*] %) of the costs
                     of the clinical trial (excluding the costs of the supply of
                     Compound and any costs for required regulatory filings),
                     provided that if the MRC, NIH or other governmental or
                     non-commercial sponsor agrees to provide less than [*]

<PAGE>

                     percent ([* ]%) of such costs, the payment to HDCI
                     hereunder shall be reduced by the amount of funding for
                     such study provided by Interneuron (excluding the costs of
                     the supply of Compound and any costs for required
                     regulatory filings). Notwithstanding the foregoing, in the
                     event that (1) the MRC, NIH or other governmental or
                     non-commercial sponsor conducts a Phase 3 efficacy clinical
                     trial (or a Phase 3 portion of any Phase 2/3 clinical
                     trial) that does not conform with the guidelines set forth
                     in Appendix 5.2(b) and (2) the final results of such
                     clinical trial demonstrate efficacy and are sufficient to
                     obtain approval of the Product by the FDA, then Interneuron
                     shall provide to HDCI the payment under this Section 5.2(b)
                     upon the receipt of FDA approval.

         For purposes of this Section 5.2, initiation of a clinical trial shall
         mean the date of enrollment of the first participant in such trial.
         Interneuron shall notify HDCI in writing within sixty (60) days after
         the achievement of each milestone, and such notice shall be accompanied
         by payment of the appropriate milestone payment.

5.3.   ROYALTIES; ROYALTY BUY-OUT OPTION.

5.3.1  ROYALTIES PAYABLE BY INTERNEURON.

              (a)    (i) Subject to the terms and conditions of this Agreement,
                     Interneuron shall pay to HDCI royalties in an amount equal
                     to the following percentages of Net Sales in each Royalty
                     Year by Interneuron or its Affiliates in each country in
                     the Territory where the manufacture, use or sale of such
                     Product would, absent the license granted hereunder,
                     infringe one or more Valid Claims of the Patent Assets in
                     such country:

<TABLE>
<CAPTION>

            AMOUNT OF NET SALES                                ROYALTY RATE
            -------------------                                ------------
<S>                                                         <C>
            Up to $[*] million                                     [*] %
            Over $[*] million and up to $[*] million               [*] %
            More than $[*] million                                 [*] %

</TABLE>

                     Royalties on Net Sales at the rates set forth above shall
                     accrue as of the date of First Commercial Sale of Product
                     in such country and shall continue and accrue on Net Sales
                     on a country-by-country basis until the expiration of the
                     last applicable patent included within the Patent Assets,
                     which patent includes a Valid Claim that covers the
                     manufacture, use or sale of such Product or Compound in
                     such country. Thereafter, Interneuron shall not be required
                     to make any payments of royalties set forth in this Section
                     5.3.

----------------------
* Confidential treatment requested.

<PAGE>

                     (ii) Subject to the terms and conditions of this Agreement,
                     Interneuron shall pay to HDCI [*] percent ([* ] %) of
                     Operating Profit on sales of Compound or Product by
                     Interneuron or its Affiliates in each country in the
                     Territory where the manufacture, use or sale of such
                     Product does not or would not infringe one or more Valid
                     Claims of the Patent Assets in such country, provided that
                     and for so long as, the manufacture, use or sale of such
                     Product would, absent the license granted hereunder,
                     infringe one or more Valid Claims of the Patent Assets in
                     the U.S., United Kingdom, France, Germany, Italy or Spain.

                     The foregoing share of Operating Profit to HDCI shall
                     accrue as of the date of First Commercial Sale of Product
                     in a country where the manufacture, use or sale of such
                     Product does not infringe one or more Valid Claims of the
                     Patent Assets in such country but would, absent the license
                     granted hereunder, infringe one or more Valid Claims of the
                     Patent Assets in the U.S., United Kingdom, France, Germany,
                     Italy or Spain and shall continue and accrue on a
                     country-by-country basis until the expiration of the last
                     applicable patent included within the Patent Assets in the
                     U.S., United Kingdom, France, Germany, Italy or Spain.
                     Thereafter, Interneuron shall not be required to make any
                     payments of Operating Profits set forth in this Section
                     5.3.

              (b)    The payment of royalties and percentage of Operating Profit
                     set forth above shall be subject to the following
                     conditions:

                     (i)    that only one payment shall be due with respect to
                            the same unit of Product;

                     (ii)   that in the event that Interneuron enters into a
                            sublicense in the Territory to a Third Party or
                            Third Parties, in lieu of royalty and Operating
                            Profit payments set forth in Section 5.3.1(a),
                            Interneuron shall pay HDCI [*] percent ([* ] %) of
                            sublicensing royalties on net sales of Product (s)
                            received by Interneuron from such sublicense(s); and

                     (iii)  no royalties or Operating Profit sharing shall
                            accrue on the disposition of Product by Interneuron,
                            Affiliates or sublicensees as samples (promotion or
                            otherwise) or as donations (for example, to
                            non-profit institutions or government agencies) or
                            to the extent Product is made available at cost or
                            at a substantial discount from the prevailing price
                            for Product in the U.S. pursuant to Section 2.3 of
                            the MRC 1996 Agreement or Section 2.2 of the MRC
                            1999 Agreement.

------------------------
* Confidential treatment requested.

* Confidential treatment requested.

<PAGE>

                     (iv)   HDCI shall remain responsible for payment of any
                            royalties due MRC or any other entity with whom HDCI
                            agreed to pay a royalty on Compound or Product prior
                            to the Effective Date.

5.3.2  ROYALTIES FOR BULK COMPOUND. In those cases where Interneuron sells bulk
       Compound to be incorporated into Product, rather than a Product, to a
       Third Party (excluding sales within or among Interneuron, its Affiliates
       and/or its sublicensees), and is unable to determine Net Sales, royalties
       set forth in this Article V shall be calculated as if the bulk Compound
       is deemed to be Product.

5.3.3  COMPULSORY LICENSES. If a compulsory license is granted to a Third Party
       with respect to Product in any country in the Territory with a royalty
       rate lower than the royalty rate provided by Section 5.3.1, then the
       royalty rate to be paid by Interneuron on Net Sales in that country under
       Section 5.3.1 shall be reduced to the rate paid by the compulsory Third
       Party licensee.

5.3.4  THIRD PARTY LICENSES. If one or more licenses from a Third Party or
       Parties are obtained by Interneuron or its Affiliates to develop, make,
       have made, use, sell or import Compound or Product in a particular
       country within the Territory, [*] percent ([*] %) of any royalties or
       other payments paid under such Third Party patent licenses by Interneuron
       in such country for such Calendar Quarter shall be creditable against the
       royalty or other payments to be paid to HDCI by Interneuron in such
       country; provided, however, that the royalties payable to HDCI hereunder
       shall not be reduced by more than [*] percent ([*] %) unless, absent the
       said license(s), Interneuron or its Affiliates would be prevented from
       practicing the Patent Assets licensed under Article 2 hereof, in which
       case the royalties or other payments payable to HDCI hereunder may be
       reduced by more than [*] percent ([*] %).

5.4.   ROYALTY BUY-OUT OPTION.

5.4.1  OPTION. At any time prior to the date Interneuron is notified officially
       by a representative of the study group in writing or verbally of the
       preliminary statistical evaluation of the Pivotal Trial, Interneuron
       shall have the option (the "Royalty Buy-Out Option"), to buy out the
       royalty obligations set forth in Section 5.3 for $[*], whereupon this
       license shall become a perpetual, royalty-free fully-paid up license. For
       purposes of this Section 5.4.1 the Pivotal Trial shall mean the clinical
       trial described in Section 5.2(b).

5.4.2  NOTICE PERIOD. In the event Interneuron determines to exercise the
       Royalty Buy-Out Option, it shall notify HDCI in writing. The date of
       Interneuron's notice to HDCI shall be the Election Date.

5.4.3  PAYMENTS IN INTERNEURON STOCK. In the event that Interneuron elects to
       exercise the

<PAGE>

       Royalty Buy-out Option, [*] percent ([*] %) of the payment shall be due
       in cash and [*] percent ([*] %) of the payment shall be due in shares of
       Interneuron Stock. The number of shares of Interneuron Stock to be issued
       as [* ] % of the payment to HDCI shall equal the number of shares of
       Interneuron Stock, rounded to the nearest whole number, having a Fair
       Market Value as of the Election Date equal to $[* ].

5.5.   PAYMENTS FROM SUBLICENSEE. Interneuron will pay HDCI [*] percent ([*] %)
       of (i) any lump sum, milestone or other cash payments (other than
       royalties) or (ii) any securities of a sublicensee issued by such
       sublicensee, in either case received by Interneuron from sublicensees of
       Interneuron which payments or securities constitute advance royalties or
       other consideration for a sublicense agreement relating to the Patent
       Assets, excluding amounts received by Interneuron from Third Parties in
       connection with the issuance of debt or equity securities in Interneuron
       or to fund or reimburse research and development of Product; PROVIDED,
       HOWEVER, that (i) any payments made to HDCI under this Section 5.5 that
       arise as a result of payments from sublicensees that are refunded by
       Interneuron shall be refunded by HDCI to Interneuron, or at Interneuron's
       election, credited against the milestones payable to HDCI listed under
       Section 5.2 (a) and (b) and (ii) only one payment hereunder shall be due
       with respect to the same payment made to Interneuron by a sublicensee.

       In the event Interneuron sublicenses the rights granted under Article 2
       hereof and, in lieu of the consideration referred to in the immediately
       preceding paragraph, Interneuron receives from the sublicensee for such
       sublicense rights in the sublicensee's technology, products or compounds
       (the "Technology"), then (a) if Interneuron sublicenses the Technology to
       a subsequent Third Party, Interneuron shall pay to HDCI [*] percent ([*]
       %) of any lump sum, milestone, royalty, other cash payments or securities
       received by Interneuron from the subsequent Third Party sublicensee which
       payments constitute consideration for a sublicense of the Technology to
       the subsequent Third Party sublicensee or (b) if Interneuron or its
       Affiliates commercializes the Technology internally, Interneuron shall
       pay to HDCI [*] percent ([*] %) of the operating profit on sales of
       product containing or utilizing the Technology. For purposes of this
       Section 5.5, "operating profit" shall mean the net sales received by
       Interneuron or its Affiliates for a product containing or utilizing the
       Technology, less the direct and indirect manufacturing costs incurred by
       Interneuron or its Affiliates specifically allowable to and directly
       attributable to the product, selling, distribution and inventory
       management costs and other

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

* Confidential treatment requested.

* Confidential treatment requested.

<PAGE>

       costs related to or allocable to the achievement of net sales and
       determined in accordance with GAAP.

5.6.   REPORTS; PAYMENT OF ROYALTY. Following the First Commercial Sale of a
       Product and during the term of the Agreement for so long as royalty or
       Operating Profit payments are due, Interneuron shall furnish to HDCI a
       quarterly written report for the Calendar Quarter showing the sales of
       all Products subject to royalty or Operating Profit payments sold by
       Interneuron, its Affiliates and its sublicensees in the Territory during
       the reporting period and the royalties or Operating Profit payable under
       this Agreement. Reports shall be due on the ninetieth (90th) day
       following the close of each Calendar Quarter. Royalties and Operating
       Profit shown to have accrued by each royalty report, if any, shall be due
       and payable on the date such royalty report is due. Interneuron shall
       keep complete and accurate records in sufficient detail to enable the
       royalties and Operating Profit payable hereunder to be determined.

5.7.   AUDITS.

              (a)    Upon the written request of HDCI and not more than once in
                     each Calendar Year, Interneuron shall permit an independent
                     certified public accounting firm of nationally recognized
                     standing selected by HDCI and reasonably acceptable to
                     Interneuron, to have access during normal business hours at
                     times mutually convenient to the Parties and upon
                     reasonable notice to Interneuron to such of the records of
                     Interneuron as may be reasonably necessary to verify the
                     accuracy of the royalty reports hereunder for any year
                     ending not more than twenty-four (24) months prior to the
                     date of such request. The accounting firm shall disclose
                     only to HDCI only whether the royalty reports are correct
                     or incorrect and the specific details concerning any
                     discrepancies.

              (b)    If such accounting firm concludes, and Interneuron agrees,
                     that additional royalties or Operating Profit were owed
                     during such period, Interneuron shall pay the additional
                     royalties or Operating Profit (plus accrued interest at the
                     rate announced by Fleet National Bank in Boston,
                     Massachusetts (or its successors or assigns) as its prime
                     rate in effect on the date that such payment was first due)
                     within sixty (60) days of the date HDCI delivers to
                     Interneuron such accounting firm's written report so
                     concluding; provided that, in the event that Interneuron
                     shall not be in agreement with the conclusion of such
                     report (a) Interneuron shall not be required to pay such
                     additional royalties or Operating Profit and (b) such
                     matter shall be resolved pursuant to the provisions of
                     Section 9.6 herein. In the event such accounting firm
                     concludes that amounts were overpaid by Interneuron during
                     such period, HDCI shall reimburse Interneuron the amount of
                     such overpayment within thirty (30) days of receipt of such
                     accounting firm's written report. The fees charged by such
                     accounting firm shall be paid by HDCI; PROVIDED, HOWEVER,
                     that if an error in favor of

<PAGE>

                     HDCI in the payment of royalties or Operating Profit of
                     more than the greater of (i) $100,000 or (ii) ten percent
                     (10%) of the royalties or Operating Profit due hereunder
                     for the period being reviewed is discovered, then the fees
                     and expenses of the accounting firm shall be reimbursed by
                     Interneuron.

              (c)    Upon the expiration of twenty-four (24) months following
                     the end of any Royalty Year the calculation of royalties or
                     Operating Profit payable with respect to such year shall be
                     binding and conclusive upon HDCI, and Interneuron shall be
                     released from any liability or accountability with respect
                     to royalties and Operating Profit for such year.

              (d)    HDCI shall treat all financial information subject to
                     review under this Section 5.7 in accordance with the
                     confidentiality provisions of this Agreement.

5.8.   PAYMENT EXCHANGE RATE. All payments to HDCI under this Agreement shall be
       made in United States dollars. In the case of sales outside the United
       States, the rate of exchange to be used in computing the amount of
       currency equivalent in United States dollars due HDCI shall be calculated
       monthly in accordance with GAAP and based on the average of the
       conversion rates on the first and last Business Day of each month during
       each Calendar Quarter published in the Wall Street Journal, Eastern
       edition.

5.9.   TAX WITHHOLDING. If laws, rules or regulations require withholding of
       income taxes or other taxes imposed upon payments set forth in this
       Article V, HDCI shall provide Interneuron, prior to any such payment,
       annually or more frequently if required, with all forms or documentation
       required by any applicable taxation laws, treaties or agreements to such
       withholding or as necessary to claim a benefit thereunder (including, but
       not limited to, Form 1001 and any successor form) and Interneuron shall
       make such withholding payments as required and subtract such withholding
       payments from the payments set forth in this Article V. Interneuron shall
       submit appropriate proof to HDCI of payment of the withholding taxes
       within a reasonable period of time. Interneuron will use commercially
       reasonable efforts consistent with its usual business practices to ensure
       that any withholding taxes imposed are reduced as far as possible under
       the provisions of the current or any future taxation treaties or
       agreements between foreign countries, and HDCI shall cooperate with such
       efforts.

5.10.  INTEREST ON LATE PAYMENTS. Except as otherwise set forth in this
       Agreement, any payments by Interneuron that are not paid on or before the
       date such payments are due under this Agreement shall bear interest, to
       the extent permitted by applicable law, at the rate announced from time
       to time by Fleet National Bank in Boston, Massachusetts (or its successor
       or assigns) as its prime rate, calculated on the number of days payment
       is delinquent; PROVIDED, that if such payment has been delayed because it
       is related to a dispute raised by a Party in good faith that is
       undergoing the dispute resolution procedures set forth in Section 9.6
       hereof, interest shall be calculated on the number of days payment is
       delinquent starting on the day after such dispute is finally resolved.

<PAGE>

5.11.  EXCHANGE CONTROLS. Notwithstanding any other provision of this Agreement,
       if at any time legal restrictions prevent the prompt remittance of part
       or all of the royalties with respect to Net Sales or Operating Profits in
       any country, payment shall be made through such lawful means or methods
       as Interneuron may determine. When in any country the law or regulations
       prohibit both the transmittal and deposit of royalties on sales or
       Operating Profits in such a country, royalty payments or Operating
       Profits shall be suspended for as long as such prohibition is in effect
       (and such suspended payments shall not accrue interest), and promptly
       after such prohibition ceases to be in effect, all royalties that
       Interneuron or its Affiliates or sublicensees would have been obligated
       to transmit or deposit, but for the prohibition, shall be deposited or
       transmitted, as the case may be, to the extent allowable (with any
       interest earned on such suspended royalties which were placed in an
       interest-bearing bank account in that country, less any transactional
       costs). If the royalty rate specified in this Agreement should exceed the
       permissible rate established in any country, the royalty rate for sales
       in such country shall be adjusted to the highest legally permissible or
       government-approved rate.

                                   ARTICLE VI
                         REPRESENTATIONS AND WARRANTIES

6.1.   HDCI REPRESENTATIONS AND WARRANTIES. HDCI represents and warrants to
       Interneuron that as of the Effective Date:

              (a)    to the best of its knowledge, there is no reason that the
                     presumption of validity would not apply to the issued
                     patents included in the Patent Assets and no reason that a
                     court of competent jurisdiction would, upon investigation,
                     find such patents unenforceable;

              (b)    this Agreement has been duly executed and delivered by it
                     and constitutes legal, valid, and binding obligations of it
                     enforceable against it in accordance with its terms;

              (c)    no approval, authorization, consent, or other order or
                     action of or filing with any court, administrative agency
                     or other governmental authority is required for the
                     execution and delivery by it of this Agreement or the
                     consummation by it of the transactions contemplated hereby;

              (d)    it has the full right, power and authority to enter into
                     and deliver this Agreement, to perform and to grant the
                     licenses granted under Article II hereof and to consummate
                     the transactions contemplated hereby. All corporate acts
                     and other proceedings required to be taken to authorize
                     such execution, delivery, and consummation have been duly
                     and properly taken and obtained;

              (e)    it has not previously assigned, transferred, conveyed or
                     otherwise encumbered its right, title and interest in the
                     Patent Assets or HDCI Know-How or entered into any
                     agreement with any Third Party which is in conflict with
                     the

<PAGE>

                     rights granted to Interneuron pursuant to this Agreement;

              (f)    it is the sole and exclusive owner under the Patent Assets
                     and HDCI Know-How, all of which are free and clear of any
                     liens, charges and encumbrances, and no other person,
                     corporate or other private entity, or governmental entity
                     or subdivision thereof, has any valid claim of ownership
                     with respect to the Patent Assets and HDCI Know-How,
                     whatsoever. HDCI shall notify the U.S. Patent & Trademark
                     Office and foreign patent offices that Procept, Inc.
                     changed its name to HDCI and take any other actions
                     necessary to effect this change;

              (g)    to the best of HDCI's knowledge, the Patent Assets and HDCI
                     Know-How practiced as contemplated herein and the
                     development, manufacture, use and sale of Compound and
                     Products do not and will not infringe any patent rights
                     owned or possessed by any Third Party;

              (h)    there are no claims, judgments or settlements against or
                     owed by HDCI or pending or, threatened claims or litigation
                     relating to the Patent Assets and HDCI Know-How;

              (i)    it has disclosed to Interneuron all relevant information
                     known by it regarding the Patent Assets and HDCI Know-How
                     reasonably related to the activities contemplated under
                     this Agreement; and

              (j)    to its knowledge, no contract research organization,
                     corporation, business entity or individual which have been
                     involved in any studies conducted for the purpose of
                     obtaining regulatory approvals have been debarred
                     individuals or entities within the meaning of 21 U.S.C.
                     section 335(a) or (b).

6.2.   WARRANTY DISCLAIMER. EXCEPT AS OTHERWISE EXPRESSLY PROVIDED IN THIS
       AGREEMENT, HDCI MAKES NO WARRANTY, EXPRESS OR IMPLIED, WITH RESPECT TO
       THE PATENT ASSETS, HDCI KNOW-HOW OR OTHER SUBJECT MATTER OF THIS
       AGREEMENT AND HEREBY DISCLAIMS WARRANTIES OF MERCHANTABILITY, FITNESS FOR
       A PARTICULAR PURPOSE AND NON-INFRINGEMENT WITH RESPECT TO ANY AND ALL OF
       THE FOREGOING.

6.3.   INVESTMENT REPRESENTATIONS.

              (a)    ACQUISITION FOR INVESTMENT. In the event the Royalty
                     Buy-Out Option is exercised, HDCI hereby represents that it
                     is acquiring the Interneuron Stock as principal for its own
                     account for investment and not with a view to any sale or
                     distribution thereof within the meaning of the 1933 Act and
                     not for the benefit of any other person. HDCI understands
                     that the Interneuron Stock that may be acquired hereby will
                     not been registered under the 1933 Act, by reason of its
                     issuance by Interneuron in a transaction exempt from the
                     registration requirements of the 1933 Act, and

<PAGE>

                     that any such unregistered shares must be held by HDCI
                     indefinitely unless a subsequent disposition thereof is
                     registered under the 1933 Act and any applicable state
                     securities or blue sky laws or unless an exemption from
                     registration is available.

              (b)    ACKNOWLEDGMENTS OF HDCI. HDCI acknowledges that:

                     (i)    HDCI has obtained all the necessary information
                            concerning Interneuron that it requires and that it
                            does not require any additional information about
                            Interneuron or the Interneuron Stock;

                     (ii)   an investment in the Interneuron Stock is highly
                            speculative and could result in a total loss of its
                            investment and that HDCI has a net worth sufficient
                            to permit HDCI to afford a total loss of its
                            investment without substantially affecting HDCI `s
                            present business affairs;

                     (iii)  in completing the sale of the Interneuron Stock to
                            HDCI, Interneuron will rely on the representations
                            and warranties of HDCI contained in this Agreement;

                     (iv)   Interneuron has not provided HDCI with investment,
                            legal or tax advice or acted as an adviser with
                            respect to this subscription and HDCI is relying
                            solely on its own professional advisers, if any, for
                            any necessary advice; and

                     (v)    HDCI has had an opportunity to ask questions and
                            receive answers concerning Interneuron and its
                            proposed business, and that any request for such
                            information has been complied with to HDCI's
                            satisfaction.

              (c)    CERTIFICATES TO BEAR LEGENDS. The certificate or
                     certificates evidencing the Interneuron Stock shall bear
                     the following legend until such time as the legend may be
                     removed pursuant to Section 6.2(d) herein:

                     "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT
                     BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
                     AMENDED (THE "SECURITIES ACT") OR ANY STATE SECURITIES LAWS
                     AND MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO (i) AN
                     EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT,
                     OR (ii) AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES
                     ACT."

              (d)    REMOVAL OF LEGENDS AND TRANSFER RESTRICTIONS. The legends
                     endorsed on each certificate for the Interneuron Stock
                     pursuant to Section 6.2(c) shall be

<PAGE>

                     removed and Interneuron shall issue a certificate without
                     such legends to HDCI if (x) such Securities are registered
                     under the 1933 Act and a prospectus meeting the
                     requirements of Section 10 of the 1933 Act is available and
                     the Interneuron Stock is sold thereunder, or (y) there is
                     available an exemption from registration under the 1933
                     Act, and Interneuron shall have received an opinion of
                     counsel to HDCI to such effect.

6.4.   INTERNEURON REPRESENTATIONS AND WARRANTIES. Interneuron represents and
       warrants to HDCI that as of the Effective Date:

              (a)    this Agreement has been duly executed and delivered by it
                     and constitutes legal, valid, and binding obligations of it
                     enforceable against it in accordance with its terms;

              (b)    it has full corporate power and authority to execute and
                     deliver this Agreement and to consummate the transactions
                     contemplated hereby. All corporate acts and other
                     proceedings required to be taken to authorize such
                     execution, delivery, and consummation have been duly and
                     properly taken and obtained; and

              (c)    no approval, authorization, consent, or other order or
                     action of or filing with any court, administrative agency
                     or other governmental authority is required for the
                     execution and delivery by it of this Agreement or the
                     consummation by it of the transactions contemplated hereby.

                                  ARTICLE VII
                                 PATENT MATTERS

7.1.   FILING, PROSECUTION AND MAINTENANCE OF PATENT APPLICATIONS OR PATENTS.
       Interneuron shall file, prosecute and maintain the patent applications
       and patents included in the Patent Assets, in HDCI's name using counsel
       reasonably acceptable to HDCI (including counsel listed on Schedule 7.1
       hereto), in such countries in the Territory as Interneuron shall
       determine in its sole discretion. HDCI shall be responsible for the
       payment of all patent costs incurred prior to the Effective Date and
       Interneuron shall pay all patent costs incurred after the Effective Date.
       If Interneuron elects not to file, prosecute or maintain a patent
       application or patent included in the Patent Assets, and advises HDCI in
       writing that it intends not to file, prosecute, or maintain such patent
       application or patent, HDCI shall have the right, at its sole expense, to
       file, prosecute, or maintain such patent application or patent, and
       Interneuron shall cooperate in the filing, prosecution, or maintenance of
       such patent application or patent. In each case, the filing Party shall
       give the non-filing Party an opportunity to review the text of the
       application before filing, shall consult with the non-filing Party with
       respect thereto, and shall supply the non-filing Party with a copy of the
       application as filed, together with notice of its filing date and serial
       number. The filing Party shall keep the non-filing Party advised of the
       status of the actual and prospective patent application filings and upon
       the request of the non-filing Party,

<PAGE>

       provide advance copies of any papers related to the filing, prosecution,
       or maintenance of such patent application filings. Interneuron shall give
       notice to HDCI of the grant, lapse, revocation, surrender, invalidation
       or abandonment of any patent licensed to Interneuron by HDCI. The Party
       that is the filing Party under this Section shall be responsible for the
       payment of all costs and expenses related to such filing and subsequent
       prosecution and maintenance thereof.

7.2.   PATENT OFFICE PROCEEDINGS. Each Party shall inform the other Party of any
       request for, filing, or declaration of any proceeding before a patent
       office seeking to protest, oppose, cancel, reexamine, declare an
       interference proceeding, initiate a conflicts proceeding, or analogous
       process involving a patent application or patent included in the Patent
       Assets. HDCI thereafter shall cooperate fully with Interneuron with
       respect to any such patent office proceeding that Interneuron chooses in
       its sole discretion to defend. HDCI will provide Interneuron with any
       information or assistance that Interneuron reasonably may request.
       Interneuron shall bear the expense of defending any such patent office
       proceeding that Interneuron chooses to defend.

7.3.   ENFORCEMENT AND DEFENSE.

              (a)    Each Party shall promptly give the other Party notice of
                     any infringement in the Territory of any patent application
                     or patent included in the Patent Assets that comes to such
                     Party's attention. The Parties will thereafter consult and
                     cooperate fully to determine a course of action, including,
                     without limitation, the commencement of legal action by any
                     Party. However, Interneuron, upon notice to HDCI, shall
                     have the first right to initiate and prosecute such legal
                     action at its own expense and in the name of HDCI and
                     Interneuron, or to control the defense of any declaratory
                     judgment action relating to Patent Assets. Interneuron
                     shall promptly inform HDCI if Interneuron elects not to
                     exercise such first right, and HDCI thereafter shall have
                     the right either to initiate and prosecute such action or
                     to control the defense of such declaratory judgment action
                     in the name of HDCI and, if necessary, Interneuron. In no
                     event shall Interneuron enter into any settlement which
                     would adversely affect the Patent Assets in any material
                     respect without the prior written consent of HDCI, which
                     consent shall not be unreasonably withheld.

              (b)    If Interneuron elects not to initiate and prosecute an
                     infringement or defend a declaratory judgment action in any
                     country in the Territory as provided in Subsection 7.3(a),
                     and HDCI elects to do so, the cost of any agreed-upon
                     course of action, including the costs of any legal action
                     commenced or any declaratory judgment action defended,
                     shall be borne solely by HDCI.

              (c)    For any such legal action or defense, in the event that any
                     Party is unable to initiate, prosecute, or defend such
                     action solely in its own name, the other Party will join
                     such action voluntarily and will execute all documents

<PAGE>

                     necessary for the Party to prosecute, defend and maintain
                     such action. In connection with any such action, the
                     Parties will cooperate fully and will provide each other
                     with any information or assistance that either reasonably
                     may request. Each Party shall keep the other informed of
                     developments in any such action or proceeding, including,
                     to the extent permissible by law, the status of any
                     settlement negotiations and the terms of any offer related
                     thereto.

              (d)    Any recovery obtained by Interneuron or HDCI shall be
                     shared as follows:

                     (i)    the Party that initiated and prosecuted, or
                            maintained the defense of, the action shall recoup
                            all of its costs and expenses incurred in connection
                            with the action, whether by settlement or otherwise;

                     (ii)   the other Party then shall, to the extent possible,
                            recover its costs and expenses incurred in
                            connection with the action;

                     (iii)  if HDCI initiated and prosecuted, or maintained the
                            defense of, the action, the amount of any recovery
                            remaining then shall be retained by HDCI; and

                     (iv)   if Interneuron initiated and prosecuted, or
                            maintained the defense of, the action, the amount of
                            any recovery remaining shall be retained by
                            Interneuron except that HDCI shall receive a portion
                            equivalent to the royalties they would have received
                            on such remaining amount if such amount were deemed
                            Net Sales and the Royalty Buy-Out Option has not
                            been exercised.

              (e)    HDCI shall inform Interneuron of any certification
                     regarding any Patent Assets it has received pursuant to
                     either 21 U.S.C. Sections 355(b)(2)(A)(iv) or
                     (j)(2)(A)(vii)(IV) or under Canada's Patented Medicines
                     (Notice of Compliance) Regulations Article 5 and shall
                     provide Interneuron with a copy of such certification
                     within five (5) days of receipt. HDCI `s and Interneuron's
                     rights with respect to the initiation and prosecution, or
                     defense, of any legal action as a result of such
                     certification or any recovery obtained as a result of such
                     legal action shall be allocated as defined in Subsections
                     7.3(a) through (d); PROVIDED, HOWEVER, that Interneuron
                     shall exercise the first right to initiate and prosecute,
                     or defend, any action and shall inform HDCI of such
                     decision within fifteen (15) days of receipt of the
                     certification, after which time, if Interneuron has not
                     advised HDCI of its intention to initiate and prosecute, or
                     defend, such action, HDCI shall have the right to initiate
                     and prosecute, or defend, such action.

7.4.   PATENT TERM EXTENSIONS AND SUPPLEMENTAL PROTECTION CERTIFICATES. The
       Parties shall cooperate in obtaining patent term extensions or
       supplemental protection certificates or their equivalents in any country
       in the Territory where applicable and where desired by

<PAGE>

       Interneuron. If elections with respect to obtaining such extension or
       supplemental protection certificates are to be made, Interneuron shall
       have the right to make the election and HDCI shall abide by such
       election.

                                  ARTICLE VIII
                              TERM AND TERMINATION

8.1.   TERM AND EXPIRATION. This Agreement shall be effective as of the
       Effective Date and unless terminated earlier pursuant to Section 8.2 and
       8.3 below, the term of this Agreement shall continue in effect until
       expiration of all royalty and Operating Profit payment obligations
       hereunder. Upon expiration of the royalty and Operating Profit
       obligations with respect to a Product hereunder, including upon exercise
       of the Royalty Buy-Out Option, Interneuron's license hereunder pursuant
       to Section 2.1 shall become a fully paid-up, perpetual license.

8.2.   TERMINATION BY NOTICE. Notwithstanding anything contained herein to the
       contrary, Interneuron shall have the right to terminate this Agreement at
       any time by giving thirty (30) days advance written notice to HDCI.
       Except as set forth in this Agreement, in the event of such termination,
       (i) the rights and obligations hereunder, excluding any payment
       obligation which has accrued as of the termination date, shall terminate
       and (ii) Interneuron shall have no further rights with respect to the
       Patent Assets or HDCI Know-How.

8.3.   TERMINATION.

8.3.1  TERMINATION FOR CAUSE. Either Party may terminate this Agreement by
       notice to the other Party at any time during the term of this Agreement
       as follows:

              (a)    if the other Party is in breach of its material obligations
                     hereunder by causes and reasons within its control, or has
                     breached, in any material respect, any representations or
                     warranties set forth in Article VI, and if capable of being
                     cured, has not cured such breach within ninety (90) days
                     after notice requesting cure of the breach provided,
                     however, that if the breach is not capable of being cured
                     within ninety (90) days of such written notice, the
                     Agreement may not be terminated so long as the breaching
                     Party commences and is taking commercially reasonable
                     actions to cure such breach as promptly as practicable; or

              (b)    upon the filing or institution of bankruptcy,
                     reorganization, liquidation or receivership proceedings, or
                     upon an assignment of a substantial portion of the assets
                     for the benefit of creditors by the other Party; PROVIDED,
                     HOWEVER, in the case of any involuntary bankruptcy,
                     reorganization, liquidation, receivership or assignment
                     proceeding such right to terminate shall only become
                     effective if the Party consents to the involuntary
                     proceeding or such proceeding is not dismissed within
                     ninety (90) days after the filing thereof.

<PAGE>

8.3.2  LICENSEE RIGHTS NOT AFFECTED.

              (a)    In the event Interneuron terminates this Agreement under
                     Section 8.3.1(b), or this Agreement is otherwise terminated
                     under Section 8.3.1(b), or HDCI is a debtor in a bankruptcy
                     proceeding, whether voluntary or involuntary, all rights
                     and licenses granted pursuant to this Agreement are, and
                     shall otherwise be deemed to be, for purposes of Section
                     365(n) of 11 U.S.C. Section101 et seq. (the "Bankruptcy
                     Code"), licenses of rights to "intellectual property" as
                     defined under Section 101(35A) of the Bankruptcy Code. The
                     Parties agree that Interneuron, as a licensee of such
                     rights under this Agreement, shall retain and may fully
                     exercise all of its rights, remedies and elections under
                     the Bankruptcy Code. The Parties further agree that, in the
                     event of the commencement of a bankruptcy proceeding by or
                     against HDCI under the Bankruptcy Code, Interneuron shall
                     be entitled to all applicable rights under Section 365 of
                     the Bankruptcy Code, including but not limited to, entitled
                     to a complete duplicate of (or complete access to, as
                     appropriate) any such intellectual property and all
                     embodiments of such intellectual property upon written
                     request therefor by Interneuron.

              (b)    In the event Interneuron is a debtor in a bankruptcy
                     proceeding, whether voluntary or involuntary, all rights
                     and licenses granted pursuant to this Agreement are, and
                     shall otherwise be deemed to be, for purposes of Section
                     365 of the Bankruptcy Code, executory contracts. The
                     Parties agree that applicable law does not excuse HDCI from
                     accepting performance by, or rendering performance under
                     this Agreement and all rights and licenses granted
                     hereunder to, a person or entity other than Interneuron.
                     Interneuron, as a licensee of such rights under this
                     Agreement, shall retain and may fully exercise all of its
                     rights, remedies and elections under the Bankruptcy Code.

8.4.   EFFECT OF EXPIRATION OR TERMINATION. Expiration or termination of this
       Agreement shall not relieve the Parties of any obligation accruing prior
       to such expiration or termination. In addition to any other provisions of
       this Agreement which by their terms continue after the expiration of this
       Agreement, the provisions of Article IV shall survive the expiration or
       termination of this Agreement and shall continue in effect for five (5)
       years from the date of expiration or termination. Any expiration or early
       termination of this Agreement shall be without prejudice to the rights of
       any Party against the other accrued or accruing under this Agreement
       prior to termination, including the obligation to pay royalties for
       Product (s) or Compound sold prior to such termination.

       Except as otherwise provided in this Section 8, in the event of
       termination by Interneuron pursuant to Section 8.2, Interneuron shall
       promptly return any and all HDCI Know-How in its possession at the time
       of termination. If requested by HDCI, Interneuron and HDCI shall
       negotiate in good faith the commercially reasonable terms of an exclusive
       license from Interneuron to HDCI of all information, materials,
       Improvements, processes,

<PAGE>

       formulas, data, inventions, know-how, trademarks, patent applications,
       patents, regulatory approvals and intellectual property rights which
       relate to Compound or Product and which are in Interneuron's possession
       or control and as to which Interneuron has the right to license or
       sublicense to HDCI without compensation to any third party (unless HDCI
       agrees to pay Interneuron any such compensation) and Interneuron shall
       use reasonable efforts to have all relevant contracts with third parties
       related to Compound or Product assigned to HDCI, provided HDCI assumes
       related obligations under such contracts.

       Except as otherwise provided in this Section 8, in the event of
       termination by HDCI pursuant to Section 8.3.1(a), Interneuron shall
       promptly return any and all HDCI Know-How in its possession at the time
       of termination. If requested by HDCI, Interneuron and HDCI shall
       negotiate in good faith the commercially reasonable terms of a
       non-exclusive license from Interneuron to HDCI of all information,
       materials, Improvements, processes, formulas, data, inventions, know-how,
       trademarks, patent applications, patents, regulatory approvals and
       intellectual property rights which relate to Compound or Product and
       which are in Interneuron's possession or control and as to which
       Interneuron has the right to license or sublicense to HDCI without
       compensation to any third party (unless HDCI agrees to pay Interneuron
       any such compensation) and Interneuron shall use reasonable efforts to
       have all relevant contracts with third parties related to Compound or
       Product assigned to HDCI, provided HDCI assumes related obligations under
       such contracts.

                                   ARTICLE IX
                                  MISCELLANEOUS

9.1.   FORCE MAJEURE. Neither Party shall be held liable or responsible to the
       other Party nor be deemed to have defaulted under or breached the
       Agreement for failure or delay in fulfilling or performing any term of
       the Agreement during the period of time when such failure or delay is
       caused by or results from causes beyond the reasonable control of the
       affected Party including, but not limited to, fire, flood, embargo, war,
       acts of war (whether war be declared or not), insurrection, riot, civil
       commotion, strike, lockout or other labor disturbance, act of God or act,
       omission or delay in acting by any governmental authority or the other
       Party. The affected Party shall notify the other Party of such force
       majeure circumstances as soon as reasonably practicable.

9.2.   ASSIGNMENT. The Agreement may not be assigned or otherwise transferred,
       nor, except as expressly provided hereunder, may any right or obligations
       hereunder be assigned or transferred by a Party; PROVIDED, HOWEVER, that
       either Party may assign this Agreement and its rights and obligations
       hereunder to an Affiliate or in connection with the transfer or sale of
       all or substantially all of its assets related to Compound or Product or
       its business or in the event of its merger or consolidation or change in
       control or similar transaction. Except as otherwise set forth herein, any
       permitted assignee shall assume all obligations of its assignor under
       this Agreement.

9.3.   SEVERABILITY. In the event that any of the provisions contained in this
       Agreement are held invalid,

<PAGE>

       illegal or unenforceable in any respect, the validity, legality and
       enforceability of the remaining provisions contained herein shall not in
       any way be affected or impaired thereby, unless the absence of the
       invalidated provision(s) adversely affect the substantive rights of the
       Parties. In such event, the Parties shall replace the invalid, illegal or
       unenforceable provision(s) with valid, legal and enforceable provision(s)
       which, insofar as practical, implement the purposes of this Agreement.

9.4.   NOTICES. All notices or other communications which are required or
       permitted hereunder shall be in writing and sufficient if delivered
       personally, sent by facsimile (and promptly confirmed by personal
       delivery, registered or certified mail or overnight courier), sent by
       nationally-recognized overnight courier or sent by registered or
       certified mail, postage prepaid, return receipt requested, addressed as
       follows:

                  if to Interneuron to:

                           Interneuron Pharmaceuticals, Inc.
                           99 Hayden Avenue, Suite 200
                           Lexington, MA  02421
                           Attention:  President
                           Fax No.:  781-862-3859

                  if to HeavenlyDoor.com, Inc. to:

                           HeavenlyDoor.com, Inc.
                           1180 Avenue of the Americas, Suite 1447
                           New York, NY 10036
                           Attention:  President
                           Fax No.:   212-899-5291

or to such other address as the Party to whom notice is to be given may have
furnished to the other Parties in writing in accordance herewith. Any such
communication shall be deemed to have been given when delivered if personally
delivered or sent by facsimile on a Business Day, upon confirmed delivery by
nationally-recognized overnight courier if so delivered and on the third
Business Day following the date of mailing if sent by registered or certified
mail.

9.5.   APPLICABLE LAW. The Agreement shall be governed by and construed in
       accordance with the laws of the United States of America and State of New
       York and the United States without reference to any rules of conflict of
       laws.

9.6.   DISPUTE RESOLUTION. The Parties agree to attempt initially to solve all
       claims, disputes, or controversies arising under, out of, or in
       connection with this Agreement by conducting good faith negotiations. If
       the Parties are unable to settle the matter between themselves within
       forty-five (45) days, either Party may initiate mediation upon written
       notice to the other Party. If the Parties have not reached a settlement
       within forty-five (45) days of the initiation of the mediation, then
       either Party may initiate binding arbitration proceedings. Whenever a
       Party shall decide to institute arbitration proceedings, it shall give
       written

<PAGE>

       notice to that effect to the other Party. The Party giving such notice
       shall refrain from instituting the arbitration proceedings for a period
       of sixty (60) days following such notice. During such period, the Parties
       shall continue to make good faith efforts to amicably resolve the dispute
       without arbitration. Any arbitration hereunder shall be conducted under
       the rules of the American Arbitration Association ("AAA"). Each such
       arbitration shall be conducted by a panel of three arbitrators: one
       arbitrator shall be appointed by each of Interneuron and HDCI and the
       third shall be appointed by the AAA. Any such arbitration shall be held
       in New York, New York. The arbitrators shall have the authority to grant
       specific performance. Judgment upon the award so rendered may be entered
       in any court having jurisdiction or application may be made to such court
       for judicial acceptance of any award and an order of enforcement, as the
       case may be. In no event shall a demand for arbitration be made after the
       date when institution of a legal or equitable proceeding based on such
       claim, dispute or other matter in question would be barred by the
       applicable statute of limitations. Each Party shall bear its own costs
       and expenses incurred in connection with any arbitration proceeding and
       the Parties shall equally share the cost of the arbitration levied by the
       AAA

9.7.   ENTIRE AGREEMENT. This Agreement contains the entire understanding of the
       Parties with respect to the subject matter hereof. All express or implied
       agreements and understandings, either oral or written, heretofore made
       are expressly merged in and made a part of this Agreement. This Agreement
       may be amended, or any term hereof modified, only by a written instrument
       duly executed by all Parties hereto.

9.8.   INDEPENDENT CONTRACTORS. It is expressly agreed that the Parties shall be
       independent contractors and that the relationship between the Parties
       shall not constitute a partnership, joint venture or agency. Neither
       Party shall have the authority to make any statements, representations or
       commitments of any kind, or to take any action, which shall be binding on
       the other Party, without the prior consent of such other Party.

9.9.   WAIVER. The waiver by a Party hereto of any right hereunder or the
       failure to perform or of a breach by another Party shall not be deemed a
       waiver of any other right hereunder or of any other breach or failure by
       said other Party whether of a similar nature or otherwise.

9.10.  HEADINGS. The captions to the several Articles and Sections hereof are
       not a part of the Agreement, but are merely guides or labels to assist in
       locating and reading the several Articles and Sections hereof.

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

         IN WITNESS WHEREOF, the Parties have executed this Agreement as of the
date first set forth above.

HEAVENLYDOOR.COM, INC.

<PAGE>


By:
         Name:    John Dee
         Title:   Vice Chairman




INTERNEURON PHARMACEUTICALS, INC.



By:
         Name:    Glenn L. Cooper, M.D.
         Title:   President and Chief Executive Officer






<PAGE>

                                  SCHEDULE 1.26
                                  PATENT ASSETS

<TABLE>
<CAPTION>

---------------------------------------------------------------------------------------------------------------------
        DOCKET                             SUMMARY OF CLAIMS                               CURRENT STATUS
      (US FILING)
---------------------------------------------------------------------------------------------------------------------
<S>                   <C>                                                      <C>
PRO93-13                Use of aldehyde/aromatic sulfonic acid condensates to    Abandoned in favor of
(11/23/93)              inhibit gp120/CD4 binding and HIV infection of CD4+      PRO93-13A
                        cells in an individual and in blood preparations.
---------------------------------------------------------------------------------------------------------------------
PRO93-13A               Use of aldehyde/aromatic sulfonic acid condensates to    Issued as U. S. Patent 5,614,559
(5/19/94)               inhibit or treat HIV infection in an individual, and to  (3/25/97)
                        inhibit HIV infection in a blood preparation.            Filed in PCT (11/17/94)
                        EPO Application contains composition claims.             National/regional filings in
                                                                                 Canada, Japan, EPO (only)
                                                                                 (5/23/96)
---------------------------------------------------------------------------------------------------------------------
PRO93-13A2**            Use of aldehyde/aromatic sulfonic acid condensates to    Issued as U. S. Patent 5,677,343
(6/6/95)                prevent or treat HIV infection in an individual, and to  (10/14/97)
                        inhibit HIV infection in a blood preparation.            No international filing
                        Composition claims abandoned.
---------------------------------------------------------------------------------------------------------------------
PRO93-13AB**            Composition claims to narrow or monodispersed            Issued as U. S. Patent 6,075,050
(6/6/95)                condensation polymer of naphthalene sulfonic acid and    (6/13/00)
                        aldehyde.  Method claims abandoned.                      No international filing
---------------------------------------------------------------------------------------------------------------------
[*]                     [*]                                                      [*]
---------------------------------------------------------------------------------------------------------------------
PRO97-01                Method of preventing pregnancy.                          Issued as U.S. Patent 5,958,399
(5/1/97)                                                                         (9/28/99)
                                                                                 Filed in PCT and South Africa
                                                                                 (4/30/98);  Allowed in South
                                                                                 Africa (2/25/99)
                                                                                 National/regional filings in EPO,
                                                                                 Russian Fed., Canada, Mexico,
                                                                                 Brazil, China, Japan, S. Korea,
                                                                                 Australia and New Zealand
---------------------------------------------------------------------------------------------------------------------
</TABLE>

-----------------------
*  Confidential treatment requested.

**  PRO93-13A2, AB, and AC filed as identical applications; AC abandoned

<PAGE>

                                  SCHEDULE 3.7

                             THIRD PARTY AGREEMENTS

1.      MRC. Interneuron hereby assumes the obligations of HDCI under
Section 2.3 of the MRC 1996 Agreement and Section 2.2 of the MRC 1999 Agreement.
The Parties shall use commercially reasonable efforts to promptly execute an
agreement among MRC, HDCI and Interneuron which includes an obligation for MRC
to release HDCI from the obligations assumed by Interneuron hereunder and,
during the negotiation of such agreement, HDCI shall use commercially reasonable
efforts to assist in obtaining MRC's agreement to modify the terms of Section
2.3 of the MRC 1996 Agreement and Section 2.2 of the MRC 1999 Agreement as
acceptable to Interneuron.

         HDCI shall remain responsible for and shall pay when due any royalties
required to be paid to MRC under the MRC 1996 Agreement.

         HDCI shall pay any remaining study payments due to MRC under the MRC
1996 Agreement or the MRC 1999 Agreement to the extent incurred prior to the
Effective Date (including without limitation the payment of $[*] due upon
submission of the data summary and the payment of $[*] for additional studies as
outlined in the letter from MRC dated May 20, 1999). HDCI has received the final
data summary and shall use its best efforts to obtain all research results from
MRC under the MRC 1999 Agreement, and shall provide such data summary and
research results to Interneuron when received.

2.      DAIDS. HDCI shall pay any remaining amounts due for the distribution
of Compound (anticipated to be less than $[*]) or any other payments to the
extent incurred prior to the Effective Date under the Clinical Trial Agreement
between the Division of AIDS, National Institute of Allergy and Infectious
Diseases ("DAIDS") and HDCI dated March 3, 1999 (the "NIH Agreement").
Notwithstanding the foregoing, Interneuron shall be responsible for any costs
associated with an optional ancillary study involving the analysis of plasma
under the NIH Agreement payable after the Effective Date (anticipated to be
approximately $[* ]) only if Interneuron notifies HDCI that Interneuron wants
such study performed. HDCI shall use its best efforts to obtain the research
results from DAIDS and shall provide such research results to Interneuron when
received. In the event HDCI is unable to obtain the research results from DAIDS,
HDCI hereby grants Interneuron permission to obtain the data directly from
DAIDS.

3.      SCHWEIZERHALL. Promptly after the Effective Date, HDCI shall terminate
the Agreement between HDCI and Schweizerhall dated February 10, 2000 (the
"Schweizerhall Agreement"). HDCI shall be responsible for any costs associated
with the termination of the Schweizerhall Agreement.

----------------------
* Confidential treatment requested.

<PAGE>

4.      PHARM-ECO. HDCI shall use its best efforts to obtain the results of
Pharm-Eco's activities under the Research and Manufacturing Contract between
HDCI and Pharm-Eco Laboratories, Inc. ("Pharm-Eco") dated March 14, 1994 (the
"Pharm-Eco Agreement") from Pharm-Eco and shall provide such results to
Interneuron when received. HDCI shall pay any remaining amounts due to Pharm-Eco
to the extent incurred prior to the Effective Date including without limitation
the costs of the May, 2000 stability study pull, except that Interneuron shall
be responsible for the payment of any fees for the one (1) stability study pull
scheduled to be performed after the Effective Date of this Agreement (which are
anticipated to be approximately $[*]). As set forth in the letter from Pharm-Eco
to the FDA dated June 8, 2000, Interneuron may cross-reference or otherwise
refer to the drug master files for the Compound.

5.      DOW. HDCI shall inform Dow Pharmaceutical Sciences ("Dow") that HDCI
grants its permission for Interneuron to continue the stability studies and
protocols that are being conducted at Dow. HDCI shall pay any remaining amounts
due to Dow to the extent incurred prior to the Effective Date (including without
limitation, the fee of approximately $[* ] for the stability study pull
authorized on April 19, 2000) and Interneuron shall be responsible for the
payment of any fees for any stability study pulls performed after the Effective
Date of this Agreement. HDCI shall use its best efforts to obtain the data
generated by Dow and shall provide such data to Interneuron when it is received.




----------------------
* Confidential treatment requested.

<PAGE>

                                  APPENDIX 4.2

                              FORM OF PRESS RELEASE







<PAGE>

                                 APPENDIX 5.2(A)

                            PHASE 2 STUDY GUIDELINES

         Phase 2 clinical trials of vaginal microbicides are designed primarily
to evaluate safety in populations of women at risk for acquiring HIV infection
and/or other sexually transmitted diseases. It is envisioned that these studies
will be conducted in developing countries; [*] female participants will be asked
to apply the product for two or more weeks while engaging in sexual intercourse.
Detailed safety assessments will be performed on each participant.

         A Phase 2 study protocol ("PREVENT") is being developed by the Medical
Research Council (MRC) Clinical Trials Unit (London, U.K.) in association with
investigators at Imperial College School of Medicine (London, U.K.), The
Institute for Tropical Medicine (Antwerp, Belgium), the MRC Programme on AIDS in
Uganda (Entebbe, Uganda), Nsambya Hospital (Kampala, Uganda) and the CENTRE DE
CONFIANCE (Abidjan, Cote d'Ivoire). The study is partially funded through a
grant awarded by the European Commission. Two populations will be involved: a
cohort of female commercial sex workers recruited in Abidjan, Cote d'Ivoire, and
a cohort of women recruited at family planning and infertility clinics in
Uganda. Currently, it is envisioned that [*] women will be randomized to receive
PRO 2000 Gel ([*]) or a matched placebo gel ([*]). These participants will be
asked to apply the gel prior to each act of sexual intercourse for four weeks.
Pelvic examinations (with colposcopy) will be conducted at [* ] intervals, and
the incidence of epithelial disruption determined. In addition, effects on the
vaginal microenvironment and laboratory safety parameters will be assessed.
Acceptability will be assessed using questionnaires.


--------------------
* Confidential treatment requested.

<PAGE>

                                 APPENDIX 5.2(B)

                            PHASE 3 STUDY GUIDELINES

         Phase 3 clinical trials of vaginal microbicides are designed to gather
information on long-term safety and protective efficacy. Such studies will be
conducted in populations of women who are at risk for acquiring HIV infection
and/or other sexually transmitted diseases. The sample size will need to be
sufficiently large to assess the risks and benefits of the product; exact
numbers of participants will be determined by statisticians based on the level
of protection anticipated, the proposed dosing period, the incidence of
infection in the target population(s), and the expected loss to follow-up.

         The HIV Prevention Trials Network (HPTN) of the National Institute of
Allergy and Infectious Diseases (NIAID) is developing a protocol for a Phase 3
trial. The HPTN Science Working Group currently envisions a multi-center,
randomized, double-blind, placebo-controlled design that will be sized to
detect, with statistical significance, an [*] % or [* ] reduction in HIV/STD
transmission rates. Women will be asked to use the product prior to each act of
intercourse for six months or more, and will be monitored periodically for
evidence of infection and safety problems. For ethical reasons, the use of male
condoms by the participant's sexual partners will be promoted, but it is
envisioned that enrollment will be limited to women who report difficulty in
adhering to a program of consistent condom use. The protocol may be divided into
Phase 2 safety and Phase 3 safety and efficacy stages.




---------------------
* Confidential treatment requested.

<PAGE>

                                  APPENDIX 7.1

                  Patent Counsel Reasonably Acceptable to HDCI

1.       Gilberto (Ybet) Villacorta