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                                                            --------------------
                                                            Certain confidential
                                                            material contained
                                                            in this document has
                                                            been omitted and
                                                            filed separately
                                                            with the Securities
                                                            and Exchange
                                                            Commission.
                                                            --------------------
CONFIDENTIAL


                                  EXHIBIT 10.1

                       GT 102-279 COLLABORATION AGREEMENT


         THIS COLLABORATION AGREEMENT dated as of December 23, 1999 (the
"Agreement") is made by and among Sankyo Pharma, Inc., a Delaware corporation
having its principal place of business at 2 Hilton Court, Parsippany, New Jersey
07054 ("Sankyo") and GelTex Pharmaceuticals, Inc., a Delaware corporation having
its principal place of business at 153 Second Avenue, Waltham, Massachusetts
02451 ("GelTex"). Sankyo and GelTex are sometimes referred to herein
individually as a "Party" and collectively as the "Parties."

                                    RECITALS

         A. GelTex is currently developing a bile acid sequestrant compound
intended to lower LDL cholesterol;

         B. Sankyo has expertise in the area of commercialization of
biopharmaceutical products;

         C. Sankyo desires to acquire an option to collaborate on the
development and commercialization of Compound in the Territory (as defined
below).


                             ARTICLE 1. DEFINITIONS

         For purposes of this Agreement, the terms defined in this Article shall
have the meanings specified below. Certain other capitalized terms are defined
elsewhere in this Agreement.

"Affiliate" shall mean any corporation or other entity that controls, is
controlled by, or is under common control with a Party. A corporation or other
entity shall be regarded as in control of another corporation or entity if it
owns or directly or indirectly controls at least fifty percent (50%) of the
voting stock or other ownership interest of the other corporation or entity, or
if it possesses, directly or indirectly, the power to direct or cause the
direction of the management and policies of the corporation or other entity or
the power to elect or appoint at least fifty percent (50%) of the members of the
governing body of the corporation or other entity. For purposes of this
Agreement, Sankyo Parke Davis is an Affiliate of Sankyo.

"Compound" shall mean all dosage forms of the bile acid sequestrant compound
known by GelTex as GT 102-279, including any improvements to and combinations of
such compound with another compound.

"Development Costs" with respect to Compound shall mean internal costs incurred
by GelTex and amounts paid by GelTex to Third Parties on or after the Effective
Date with
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respect to work performed by GelTex and its subcontractors in connection with
the conduct of the Development Plan for Compound, including without limitation:
(a) clinical grants, clinical laboratory fees, positive controls and the cost of
studies conducted and services provided by contract research organizations and
individuals, consultants, and toxicology contractors necessary or useful for the
purpose of obtaining Regulatory Approvals for Compound: (b) costs related to the
development of analytical methods; (c) the Fully Absorbed Cost of Goods for
batches of Compound manufactured and supplied for use in non-clinical and
clinical studies; (d) costs related to data management, statistical designs and
studies, document preparation and other expenses associated with the clinical
testing program for Compound; (e) costs for preparing, submitting, reviewing or
developing data or information for the purpose of submission of applications to
obtain Regulatory Approvals for Compound; (f) user fees associated with the
filing of NDAs, supplements and other regulatory submissions; (g) process
development work requested by the Joint Steering Committee (as defined below);
(h) amounts paid to Third Parties for the validation and stability of NDA
registration lots of Compound and (i) the fully burdened cost of GelTex labor
incurred in connection with the conduct of the Development Plan at hourly
billing rates set forth in the schedule attached as Exhibit B, adjusted annually
on the anniversary of the Effective Date for inflation as determined by the
United States Consumer Price Index for All Urban Consumers (the CPI-U") for the
Boston Metropolitan Area. [ * ] All cost determinations made hereunder shall be
made in accordance with GAAP.

"Development Plan" shall mean the comprehensive plan and budget for the
development of Compound under the Development Program, as more specifically
described in Article 5 hereof.

"Development Program" shall mean the non-clinical, clinical and process
development and manufacturing development of Compound, whether occurring prior
to or following Regulatory Approvals, and shall specifically include the
preparation and filing of all applications for Regulatory Approvals for
Compound.

"Drug Substance" shall mean bulk active pharmaceutical ingredient ready for
conversion to tablets.

"Effective Date" shall mean the date first written above on this Agreement.

"FDA" shall mean the United States Food and Drug Administration, any successor
agency or the regulatory authority of any country other than the United States
with responsibilities comparable to those of the United States Food and Drug
Administration.

"Field" shall mean all indications (prescription and over-the-counter) where the
desired therapeutic effect is achieved primarily through the sequestration of
bile acids.



                                       2

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"Fully Absorbed Cost of Goods" with respect to Compound shall mean all amounts
paid to Third Party contract manufacturers, including manufacturers of
intermediates, active ingredient, and finished Compound with respect to
Compound.

"GAAP" shall mean United States generally accepted accounting principles,
consistently applied.

"GelTex Patent Rights" shall mean the: (i) subject matter related to the
development, manufacture, use, offer for sale or sale of Compound claimed in or
covered by the pending patent applications and issued patents recited in Exhibit
A; and any continuations, continuations-in-part, divisionals and foreign
counterpart applications thereof and in any patents issuing on these
applications, including reissues and re-examinations; and (ii) Patent Rights
claiming [ * ] to the extent such Patent Rights relate to or are necessary or
useful for the development, manufacture, use, sale or offer for sale of Compound
and Sankyo agrees that such Patent Rights should be included in GelTex Patent
Rights.

"GelTex Technology" shall mean all present and, to the extent such Technology is
discovered, made or conceived during and in connection with the Program, future
Technology owned or controlled by, or licensed (with the right to sublicense)
to, GelTex relating to or useful for the development, manufacture, use, offer
for sale or sale of Compound.

"NDA" shall mean a new drug application filed with the FDA to obtain marketing
approval for Compound in the United States.

"Net Sales" shall mean the invoiced gross sales of the Compound sold by Sankyo
and its Affiliates to Third Party customers for use or resale in the Territory,
in each case less the following items, as determined in accordance with GAAP:
[ * ]. For purposes of determining Net Sales, the transfer of any Compound by
Sankyo to one of its Affiliates shall not be considered a sale; in such cases
Net Sales shall be determined based on the invoiced sales price to an
independent Third Party customer, less the adjustments allowed under this
Section.

"Patent Rights" shall mean patents, patent applications, certificates of
invention, or applications for certificates of invention, together with any
extensions, registrations,



                                       3

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confirmations, reissues, divisions, foreign counterpart applications,
continuations or continuations-in-part, re-examinations or renewals thereof.
"Program" shall mean the collaboration between GelTex and Sankyo described in
this Agreement.

"Regulatory Approvals" shall mean all approvals from regulatory authorities in
any country or territory required lawfully to market Compound in any such
country or territory, including without limitation, any NDA approvals and
Compound pricing approvals.


"Regulatory Scheme" shall mean the United States Food, Drug and Cosmetic Act, as
amended and the regulations, interpretations and guidelines promulgated
thereunder by the FDA or the regulatory scheme applicable to Compound in any
country or territory other than the United States, as such statues, regulations,
interpretations and guidelines or regulatory schemes may be amended from time to
time.

"Sankyo Patent Rights" shall mean Patent Rights claiming  [ * ] to the
extent such Patent Rights relate to or are necessary or useful for the
development, manufacture, use or sale of Compound.

"Sankyo Technology" shall mean Technology discovered, made or conceived during
and in connection with the Program, that is owned or controlled by, or licensed
(with the right to sublicense) to, Sankyo or its Affiliates relating to or
useful for the development, manufacture, use, sale or offer for sale of
Compound. Sankyo Technology shall not include marketing information developed or
created by Sankyo or its Affiliates.

"Territory" shall mean the United States of America and its territories and
possessions; provided, however, that the Territory may be expanded to include
additional countries or territories as described in Section 3.2.3 below.

"Technology" shall mean inventions, trade secrets, copyrights, know-how, data
and other intellectual property of any kind (including without limitation any
proprietary materials, compounds, reagents, techniques, analytical methodology,
or processes that are not included in Patent Rights).

"Third Party" shall mean any entity other than Sankyo, GelTex and their
respective Affiliates.


                        ARTICLE 2. EXCLUSIVE RELATIONSHIP

         During the Term and the term of the Agreement related to "Cholestagel"
executed on even date herewith (the "Cholestagel Agreement"), neither GelTex,
nor any of its Affiliates, shall independently, or with a Third Party engage in
the Territory in the marketing, sale or



                                       4

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distribution of products [ * ].  Notwithstanding the above, (i) GelTex and its
Affiliates shall at all times be permitted to independently or with a Third
Party develop and commercialize the Product defined in the Cholestagel Agreement
in Japan and the Europe, and (ii) following the termination of the Cholestagel
Agreement pursuant to Sections 13.2.1, 13.2.2, 13.2.3,(other than 13.2.3 (iv)),
13.2.4 or 6.2.2 of such agreement, GelTex and its Affiliates shall be permitted
to engage in the Territory in the marketing, sale or distribution of the Product
as defined in the Cholestagel Agreement. During the Term and the term of the
Agreement related to Cholestagel executed on even date herewith, neither Sankyo
nor any of its Affiliates, shall independently, or with a Third Party, or engage
in the [ * ]

         ARTICLE 3. LICENSE AND OPTION GRANTS AND RESERVATION OF RIGHTS

         3.1 License Grants to Sankyo.

                  3.1.1 Technology or Patent Rights Developed Outside of the
Program. In the event that GelTex develops, acquires rights to or otherwise
comes to own or control Technology or Patent Rights after the Effective Date
other than GelTex Patent Rights and GelTex Technology and such Technology or
Patent Rights are useful in the Field in the Territory, GelTex hereby grants to
Sankyo an option exercisable after the exercise of the 279 Option described
below, at Sankyo's discretion to obtain an exclusive, irrevocable (during the
Term) right and license and right to sublicense such Technology or Patent Rights
limited to use in the Territory in the Field to the extent useful to enable
Sankyo to develop, make, have made, use, import, offer for sale, have sold and
sell Compound, in each case subject to Sankyo's agreeing in a written document
satisfactory to GelTex to pay: (i) a commercially reasonable portion of all
costs incurred by GelTex to acquire such Technology or Patent Rights; (ii) a
commercially reasonable portion of any and all development or other direct,
documented and reasonable costs or expenses payable by GelTex for the
development of such Technology or Patent Rights since the date GelTex acquired
or gained rights to acquire such Technology or Patent Rights; and (iii) all
royalties, sublicense fees and other costs or expenses payable to Third Parties
associated with the acquisition or use of such license by Sankyo for Compound in
the Field in the Territory provided, however, that if GelTex does not own or
have exclusive rights to such Technology or Patents Rights or cannot grant
Sankyo the right to further sublicense such Technology or Patent Rights, the
license subject to Sankyo's option hereunder shall be for the same level of
exclusivity and subject to the same sublicense terms as the rights held by
GelTex with respect to such Technology or Patent Rights in the Field in the
Territory. Third Party licenses required by a court of competent jurisdiction in
order to sell Compound shall be excluded from this Section 3.1.1



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and shall be governed under the terms of Section 8.7.

         3.2 Option to License Patent Rights.

                  3.2.1 Terms of Option. GelTex hereby grants Sankyo an option
to license Compound (the "279 Option"). The initial term of the 279 Option shall
expire on the later of thirty (30) days after Sankyo's receipt of the draft
study report for Phase 2 clinical trials with respect to Compound commenced
prior to the date of this Agreement, or March 31, 2000. However, Sankyo shall be
entitled to extend the term of the 279 Option for three month periods by
providing GelTex with a written commitment to fund the development expenses, as
approved by the Joint Steering Committee (defined below), related to Compound
that will be incurred during such three month period, including any commitments
that extend beyond such three month period and are not subject to cancellation.
Notwithstanding any extension that might extend beyond such period, the final
extension term of the 279 Option will expire three months following the date of
receipt of the final report for all Phase 3 clinical trials for Compound. Should
the 279 Option expire without being exercised, Sankyo shall have no further
rights to Compound, and Sankyo shall transfer to GelTex all non-clinical,
clinical, material and other information in its possession relating to the
development of Compound. Performance by Sankyo with respect to Sections 4, 5.1,
5.2, 7, 8 (other than 8.1), 9.3, 9.4, 12.3, and 13.1, with respect to Compound
is subject to this Section 3.2.1 and is unenforceable upon expiration of the
unexercised 279 Option.

                  3.2.2 License to be Granted Upon Exercise. Effective upon
GelTex's receipt of written notice of Sankyo's proper exercise of the 279
Option, Sankyo shall be hereby granted the exclusive, irrevocable (during the
Term), right and license under the GelTex Patent Rights and GelTex Technology to
develop, make (subject to the terms of Article 6), have made (subject to the
terms of Article 6), use, import, offer for sale, have sold and sell Compound
for use in the Territory in the Field, and to practice and have practiced the
methods licensed under the GelTex Patent Rights for such purpose. The license
grants under this Section 3.2.2 may be sublicensed by Sankyo following written
notice to GelTex.

                  3.2.3 Expansion of the Territory. Sankyo is hereby granted
options to add Japan and the European Union (which shall mean those countries
which make up the European Union as of the Effective Date and the additional
countries of Norway and Switzerland) to the Territory. The options for Japan and
the European Union shall individually expire on [ * ]. Should Sankyo decide to
so expand the Territory, it shall provide GelTex with written notice of such
decision prior to the expiration of the option, and following GelTex's receipt
of such written notice, the definition of the Territory shall be revised to
include the additional countries and/or territories specified in such notice. As
part of its due diligence obligations Sankyo shall be required to: (i) commence
Phase I clinical trials of Compound in Japan within [ * ] of adding Japan to the
Territory; and (ii) file a Marketing Authorization Application in the European
Union (or equivalent regulatory submissions in at least two countries of the
European Union designated by the mutual agreement of the Parties) within [ * ]
after the NDA for Compound is filed in the United States. If Sankyo fails to
meet either of the due diligence

[ * ] Confidential information omitted and filed separately with the Commission.


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obligations described above, then: (i) the territory in which the obligation was
not meet will be removed from the definition of the Territory, and Sankyo shall
no longer have any rights to Compound in such territory; (ii) Sankyo promptly
shall deliver to GelTex all data, information and material that it may have
regarding the clinical, non-clinical and regulatory development, manufacture,
marketing, and sale of Compound in such territory; and (iii) Sankyo shall not be
entitled to receive reimbursement for a percentage of Development Costs under
Section 5.2.3.

         3.3 License from Sankyo to GelTex.

                  3.3.1 Program License. Sankyo hereby grants to GelTex a
non-exclusive, irrevocable (during the Term), royalty-free, right, license and
sublicense under the GelTex Patent Rights, GelTex Technology, Sankyo Patent
Rights and Sankyo Technology solely to the extent required to permit GelTex to
perform its duties under this Agreement. Sankyo also hereby agrees to grant to
GelTex a non-exclusive, irrevocable (during the Term), royalty-free, right,
license and sublicense under any other Technology or Patent Rights as to which
Sankyo elects to obtain a license pursuant to Section 3.1.1 above solely to the
extent required to permit GelTex to perform its duties under this Agreement.
GelTex shall have the right to sublicense its rights under this Section 3.3.1
with the prior written permission of Sankyo solely to the extent required to
permit GelTex to perform its duties under this Agreement.

                  3.3.2 Non-Exclusive License. Sankyo hereby grants to GelTex a
non-exclusive, irrevocable (during the Term), fully paid-up and royalty-free
license under the Sankyo Patent Rights and the Sankyo Technology to develop,
make, have made, use, import, offer for sale, have sold and sell Compound
outside the Territory.

         3.4 Reservation of Rights. Notwithstanding the license grants set forth
in Section 3.1 and 3.2 above, GelTex at all times reserves the right under the
GelTex Patent Rights, the GelTex Technology and any other Technology or Patent
Rights licensed to Sankyo pursuant to Section 3.1.1 above to: (i) make, have
made and use Compound for research and development purposes outside the Field;
(ii) develop, make, have made, use, import, offer for sale, sell and have sold
Compound outside the Field, but within the Territory; (iii) develop, make, have
made, use, import, offer for sale, sell and have sold Compound outside the
Territory; and (iv) grant licenses to Third Parties for the foregoing purposes.
[ * ]

         3.5 Manufacture of Compound. Notwithstanding anything else contained in
this Article 3, (i) either Party shall have the right to Manufacture or to have
Manufactured Compound in any country in the world for use, offer for sale and
sale by itself or, in the case

[ * ] Confidential information omitted and filed separately with the Commission.


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of GelTex, its licensees, in the territories allocated to it under this
Agreement, and if Sankyo does not elect to Manufacture or have Manufactured
Compound, (ii) GelTex shall have the right to Manufacture or to have
Manufactured Compound in any country in the world for use and sale by Sankyo in
the Territory.


                       ARTICLE 4. JOINT STEERING COMMITTEE

         4.1 Joint Steering Committee. Within twenty (20) working days of the
Effective Date, the Parties will establish a Joint Steering Committee to oversee
and control the development of Compound. The Joint Steering Committee will be
composed of [ * ]. The members of the Joint Steering Committee will designate a
secretary to take minutes of the meetings and facilitate the organization of the
meetings. A Party may change one or more of its representatives to the Joint
Steering Committee at any time. Members of the Joint Steering Committee may be
represented at any meeting by another member of the Joint Steering Committee, or
by a deputy. The Joint Steering Committee shall meet as needed and shall
establish procedures for governing itself. Any approval, determination or other
action agreed to by [ * ]. The Joint Steering Committee may designate project
leaders and may form designated subcommittees to the extent they deem it
necessary or advisable.

         4.2 Minutes. The Joint Steering Committee shall keep accurate minutes
of its deliberations which shall record all proposals, decisions and actions
recommended or taken. Draft minutes shall be sent to all members of the Joint
Steering Committee. All records of the Joint Steering Committee shall at all
times be available to both Sankyo and GelTex.

         4.3 General Disagreements. In the event there are disagreements within
the Joint Steering Committee, the representatives to the Joint Steering
Committee will negotiate in good faith to attempt to resolve the dispute. In the
event that the dispute is not resolved, the dispute will be presented to the
Chief Executive Officer of GelTex (or a designee) and to the President of Sankyo
(or a designee). Such executives shall meet or discuss in a telephone or video
conference each of GelTex's and Sankyo's views and explain the basis for such
dispute. [ * ]

                       ARTICLE 5. THE DEVELOPMENT PROGRAMS

         5.1 Development Program.

                  5.1.1 Initial Development Plan. On or about March 31, 2000,
the Joint Steering Committee shall prepare and approve an initial Development
Plan for the

[ * ] Confidential information omitted and filed separately with the Commission.


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development of the Compound in the United States. The Development Plan shall
describe the proposed overall program of development for Compound and the costs
associated therewith, including non-clinical development, clinical trials,
regulatory plans, process and manufacturing development, other key elements
necessary to obtain Regulatory Approvals for Compound and the strategy for
filing, prosecuting and maintaining the GelTex Patent Rights and [ * ] covering
Compound and any formulation thereof.

                  5.1.2 Allocation of Responsibilities Under the Development
Plan. The Development Plan shall allocate among the Parties responsibility for
each of the activities described therein. The Parties agree that the Development
Plan, and all annual updates thereto shall: (i) allocate to Sankyo the
responsibility for preparing and filing all Regulatory Approval filings in the
United States; (ii) allocate to Sankyo the responsibility for completing all
Regulatory Approval filings for Compound outside of the United States, if any;
(iii) allocate responsibility for conducting all pre-NDA clinical and
non-clinical studies with Compound to GelTex; (iv) allocate responsibility for
conducting all post-NDA United States clinical studies with Compound to Sankyo;
and (v) allocate responsibility for filing, prosecuting and maintaining the
GelTex Patent Rights covering Compound or any formulation thereof to GelTex.

                  5.1.3 Updated Development Plan. The Development Plan shall be
updated as necessary, but not less than annually by the Joint Steering Committee
not later than sixty (60) days prior to January 1 of each year during the
Development Program. Such updated Development Plan shall include: (i) an overall
development plan and budget for Compound which sets forth all major development
tasks, if any, remaining to be accomplished prior to submissions for Regulatory
Approvals; and (ii) a detailed description for the development activities
proposed for the forthcoming calendar year, in each case including estimated
time lines to accomplish such major tasks or detailed activities, respectively.
The members of the Joint Steering Committee shall actively consult with one
another throughout the term of the Development Program so as to adjust the
specific work performed under the Development Plan to conform to evolving
developments in technology and the results of work performed.

         5.2 Funding of the Development Programs.

                 5.2.1 Responsibility for Costs and Expenses. All costs and
expenses associated with the performance of the Development Programs shall be
borne solely by Sankyo. To the extent that responsibilities are allocated to
GelTex under a Development Plan, such Development Plan shall contain a budget of
the Development Costs expected to be incurred by GelTex in connection with the
performance of the responsibilities allocated to it. Sankyo shall not be
obligated to reimburse GelTex for any Development Costs incurred by GelTex in
the performance of a Development Plan which exceed one hundred fifteen percent
(115%) of the total amount budgeted under the Development Plan, unless such
excess Development Costs have been approved by the Joint Steering Committee.

                  5.2.2 Quarterly Payments and Quarterly Reconciliations. Within
thirty (30) days following the commencement of each calendar quarter, Sankyo
shall promptly pay

[ * ] Confidential information omitted and filed separately with the Commission.


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GelTex an amount equal to that portion of the budgeted Development Costs
expected to be incurred by GelTex during the calendar quarter in connection with
the performance of the responsibilities allocated to it under the Development
Plan. Within thirty (30) days after the end of each of the first three calendar
quarters of each year and within sixty (60) days after the end of each calendar
year, GelTex shall provide Sankyo with a detailed itemization of its Development
Costs actually incurred during the previous quarter. In the event that the
quarterly statement of actual Development Costs indicates that GelTex incurred
Development Costs in the quarter in excess of the amount paid by Sankyo for such
quarter, then the amount of the next quarterly payment due GelTex shall be
increased by such amount. If the aggregate amount stated to be due from Sankyo
in such quarterly statements for actual Development Costs is less than the
amount already paid by Sankyo for such quarter, then the next quarterly payment
then due GelTex shall be reduced by such amount. [ * ]

                  5.2.3 Reimbursement of Development Expenses. If Sankyo does
not exercise its option to expand the Territory to include the European Union or
Japan, then GelTex will reimburse Sankyo for [ * ], respectively, of the
Development Costs incurred by Sankyo upon the execution by GelTex of a
Definitive Agreement with a Third Party to commercialize Compound in such
territory.

         5.3 Development Information.

                  5.3.1 Reports and Information Exchange. Each of GelTex and
Sankyo shall use commercially reasonable and diligent efforts to disclose to the
other Party, through the Joint Steering Committee, all material information
relating to Compound promptly after it is learned or its materiality is
appreciated. The party performing or supervising clinical trials of Compound in
accordance with a Development Plan shall maintain the database of clinical trial
data accumulated from all clinical trials of Compound and of adverse reaction
information for Compound. Each Party shall keep the Joint Steering Committee
informed as to its progress in the Development Plan.

                  5.3.2 Serious Adverse Experience Reporting. It is understood
that Sankyo shall file the NDA for the Compound with the FDA in accordance with
Section 5.1.2 of the Agreement. Each Party shall have an ongoing obligation to
notify the other Party of any adverse experience report reported to it or any of
its Affiliates in connection with the use of the Compound (or the active
ingredient therein) in any clinical trial, literature report, or spontaneous
post-marketing use. This notification shall occur within seventy-two (72) hours
for an unexpected fatal or life-threatening experience (as used in 21 CFR
Section 314.80) associated with the Compound arising during a clinical trial and
within five (5) days for all other adverse experience report associated with the
Compound (or the active ingredient therein). This notification shall be by fax
at such number(s) designated by each Party. The NDA

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holder shall have responsibility to investigate such adverse experience reports
and for reporting such reports to governmental and regulatory authorities in the
Territory. For purposes of this Agreement, the term "adverse experience report"
shall mean any adverse event associated with the use of the Compound in humans,
whether or not considered drug related, including the following: "An adverse
event occurring in the course of the use of a drug product in professional
practice; an adverse event occurring from drug overdose whether accidental or
intentional; an adverse event occurring from drug abuse; an adverse event
occurring from drug withdrawal; and any failure of expected pharmacological
action."

                  5.3.3 Clinical and Regulatory Audits. GelTex shall permit
Sankyo, and, for so long as GelTex holds any Regulatory Approvals in its name,
Sankyo shall permit GelTex, to have access during regular business hours and
upon reasonable advance notice, at the auditing Party's own expense to the
non-auditing Party's records and facilities relating to the Development Program
for the purpose of monitoring compliance with current Good Manufacturing
Practices, Good Clinical Practices, Good Laboratory Practices and other
applicable requirements of all Regulatory Schemes.

                  5.3.4 Right to Use Non-Clinical, Clinical and Other
Information. Notwithstanding anything else herein to the contrary, GelTex shall
be entitled to disclose, deliver and authorize the use of any non-clinical,
clinical and any other information relating to Compound (which may include the
full text of an NDA or other regulatory filing) to a Third Party who becomes a
licensee of Compound outside the Territory, provided that, the Parties will
negotiate in good faith to reimburse Sankyo for a pro-rata portion of any phase
IV clinical data obtained by Sankyo. Should GelTex disclose or deliver to any
Third Party any information hereunder that is subject to the confidentiality
provisions of Article 11, GelTex shall ensure that such Third Party shall be
bound by substantially the same terms and conditions as are set forth in Article
11 with respect to such confidential information. In addition, GelTex shall be
permitted to use, and allow Third Party licensees to use all such non-clinical,
clinical and other information outside of the Field. Notwithstanding anything
else herein to the contrary, Sankyo shall be entitled to disclose, deliver and
authorize the use of any non-clinical, clinical and any other information
relating to Compound (which may include the full text of an NDA or other
regulatory filing) to a Third Party who becomes a licensee of Compound inside
the Territory and in the Field. Should Sankyo disclose or deliver to any Third
Party any information hereunder that is subject to the confidentiality
provisions of Article 11, Sankyo shall ensure that such Third Party shall be
bound by substantially the same terms and conditions as are set forth in Article
11 with respect to such confidential information.

                           ARTICLE 6. COMPOUND SUPPLY

         6.1 Agreement to Supply Compound.

                  6.1.1 Supply of Compound. The Parties acknowledge that GelTex
is in the early stages of defining contractual relationships with contract
manufacturers for the manufacture and supply of Compound. The Parties agree that
Sankyo and GelTex will work



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together in identifying and contracting with manufacturers of Drug Substance, as
well as formulators to tablet, package and label the final Compound in
quantities sufficient to meet the requirements of Sankyo. The parties further
agree that any contractual relationships will be subject to the commitments to
DSM Chemie Linz made prior to the Effective Date. In addition, GelTex agrees to
provide to Sankyo written notice of the key terms of any manufacturing contract
relating to the manufacture of the Compound prior to the execution of the
contract, and to consider any comments Sankyo provides regarding the key
contract terms. Sankyo will source all of its requirements for Drug Substance
from GelTex, and the terms and conditions under which GelTex shall supply such
Drug Substance shall be set forth in separate supply and quality agreements to
be entered into between the Parties at such time as GelTex has further defined
its relationships with contract manufacturers. Such terms and conditions shall
be substantially similar to those terms and conditions under which GelTex is
obligated to supply Cholestagel, as set forth in the Cholestagel Agreement.

                  6.1.2 Compound Price. The Parties acknowledge that a firm
commitment for the purchase price of Compound has not been established. GelTex
agrees to negotiate in good faith with DSM Chemie Linz with the intent of
obtaining an agreement that will allow GelTex to commit to supply the Drug
Substance for commercial lots of Compound to Sankyo for [ * ]. Notwithstanding
the above, the supply price charged by GelTex to Sankyo for commercial supply of
Drug Substance for Compound shall not exceed [ * ]. If both Parties mutually
agree that the commercial supply price for Compound is not commercially
reasonable, the Parties may mutually agree to revise the royalty rates for
Compound.


                          ARTICLE 7. COMMERCIALIZATION

         7.1 Responsibility for Commercialization. All sales, marketing,
  distribution and other costs associated with the commercialization of Compound
  in the Territory shall be borne exclusively by Sankyo. All terms of sale,
  including, without limitation pricing policies, credit terms, cash discounts
  and returns and allowances, shall be set by Sankyo in its sole discretion.

         7.2 Due Diligence.

                  7.2.1 Affirmative Obligation to Seek Regulatory Approval and
Launch. Sankyo will use commercially reasonable and diligent efforts to pursue
regulatory approval for, promote, market and sell Compound in all countries in
the Territory. GelTex shall provide all assistance reasonably requested by
Sankyo in connection with obtaining regulatory approval of Compound. If: (i)
Sankyo exercises the 279 Option; or (ii) Sankyo has extended the 279 Option and
has not yet permitted the 279 Option to terminate, Sankyo will use commercially
reasonable efforts to develop, seek regulatory approval for, promote, market and
sell Compound in all countries in the Territory. GelTex shall provide all
assistance reasonably requested by Sankyo in connection with obtaining
regulatory approval of Compound. In all cases the assistance provided to Sankyo
by GelTex hereunder shall be part of the Development Plan, and the costs
associated with such assistance shall be

[ * ] Confidential information omitted and filed separately with the Commission.


                                       12
<PAGE>   13
CONFIDENTIAL



Development Costs.

         Without limiting the generality of the foregoing, Sankyo will use
commercially reasonable and diligent efforts to launch commercial sales in each
country and/or territory within the Territory, within [ * ] of the receipt by
Sankyo of regulatory approval applicable to the country to promote, market and
sell Compound for use in the Field, unless a legal or governmental prohibition
or restriction, out of Sankyo's control, prevents Sankyo from so doing.

                  7.2.2 Consequence of Failure to Launch. If Sankyo fails to
launch the promotion, marketing and sales of Compound for use in the Field
within the [ * ] period of Article 7.2.1, within any given country in a given
territory for any reason, other than a legal or governmental prohibition or
restriction, including, but not limited to, the delay of listing on
reimbursement price schedules which are out of Sankyo's control,GelTex shall
have the right to provide written notice to Sankyo of its decision to remove the
country in question from the Territory. If GelTex makes such determination,
then: (i) such country shall be removed from the Territory with respect to
Compound for use in the Field and the right to promote, market and sell Compound
for use in the Field within such country shall automatically revert to GelTex at
GelTex's expense; (ii) all rights and licenses granted to Sankyo under this
Agreement with respect to Compound in such country shall automatically
terminate; (iii) any applicable Regulatory Approval and clinical data relating
to Compound and the country that is owned or licensed by Sankyo shall be
assigned to GelTex for use within such country; and (iv) any trademarks owned or
licensed by Sankyo with respect to Compound and the country and/or territory
shall be assigned to GelTex at GelTex's expense. If the country in which Sankyo
fails to launch the promotion, marketing and sales of Compound for use in the
Field within the [ * ] period is the United States, GelTex shall have the right
to provide written notice to Sankyo of its decision to terminate this Agreement,
and the rights and obligations of the parties shall be those set forth in
Section 14.3.2.

             ARTICLE 8. INTELLECTUAL PROPERTY RIGHTS AND OBLIGATIONS

         8.1 Ownership. The Parties acknowledge that the ownership rights set
forth herein: (i) shall not be affected by the participation in the development
of an Invention by the Joint Steering Committee in the course of discharging its
duties hereunder; and (ii) are subject to the license grants set forth in
Article 3 above.

                  8.1.1 Ownership of Discoveries and Improvements. All right,
title and interest in all writings, inventions, discoveries, improvements and
other Technology, whether or not patentable or copyrightable, and any patent
applications, patents or copyrights based thereon that are discovered, made or
conceived during and in connection with the Program (collectively, the
"Inventions")


                                       13

[*] Confidential information omitted and filed separately with the Commission.
<PAGE>   14
CONFIDENTIAL



[ * ] Each of GelTex and Sankyo shall promptly disclose to the other Party the
making, conception or reduction to practice of Inventions by employees or others
acting on behalf of such Party or inventions licensed to the other Party
hereunder. Patent Rights and Technology covering [ * ] shall be automatically
licensed to Sankyo in accordance with Section 3.2.2 hereof to the extent that
Sankyo has determined to include such [ * ] in the definition of GelTex Patent
Rights. Patent Rights and Technology covering [ * ] shall be automatically
licensed to GelTex in accordance with Sections 3.3.1 and 3.3.2 hereof.

                  8.1.2 Determination of Inventorship. Inventorship shall be
determined in accordance with United States patent law.

                  8.1.3 Ownership of Trademarks. Sankyo shall select all
trademarks for the sale and use of Compound in the Territory and Sankyo shall
bear all expenses thereof.

                  8.1.4 Cooperation of Employees. Each of Sankyo and GelTex
represents and agrees that all employees or others acting on its behalf in
performing its obligations under this Agreement shall be obligated under a
binding written agreement to assign to such Party, or as such Party shall
direct, all Inventions made or conceived by such employee or other person. In
the case of non-employees working for other companies or institutions on behalf
of GelTex or Sankyo, GelTex or Sankyo, as applicable, shall use commercially
reasonable and diligent efforts to obtain licenses for all Inventions made by
such non-employees on behalf of Sankyo or GelTex, as applicable, in accordance
with the policies of said company or institution. Sankyo and GelTex agree to
undertake to use commercially reasonable and diligent efforts to enforce such
agreements (including, where appropriate, by legal action) considering, among
other things, the commercial value of such Inventions.

         8.2 Filing, Prosecution and Maintenance of Patent Rights.

                  8.2.1 Filing, Prosecution and Maintenance. Each of Sankyo and
GelTex shall be responsible for the reasonable and diligent filing, prosecution,
maintenance and all patent term extensions of all patent applications and
patents which make up its Patent Rights, except that the Parties will determine,
on a case-by-case basis, which Party shall be responsible for the filing,
prosecuting and maintenance of all patent applications and patents covering
[ * ]. For so long as any of the license grants set forth in Section 3.2.2
hereof remain in effect in the Territory, GelTex agrees to file and prosecute
patent applications, obtain patent term extensions, where available and maintain
the patents covering its Patent Rights in any such country in the Territory.
GelTex shall consult with and keep Sankyo informed of all material issues
relating to the preparation and filing, prosecution and maintenance of such
patent applications and patents.

                  8.2.2 Patent Filing Costs. All reasonable and documented costs
incurred after the Effective Date associated with filing, prosecuting and
maintaining patent


                                       14

[*] Confidential information omitted and filed separately with the Commission.
<PAGE>   15
CONFIDENTIAL



applications and patents covering each of GelTex's Patent Rights with claims
applicable to the Field in the Territory shall be deemed Development Costs and
shall be funded by [ * ].

         8.3 Cooperation. Each of GelTex and Sankyo shall, at its own expense,
make available to the other Party (or to the other Party's authorized attorneys,
agents or representatives) its employees, agents or consultants to the extent
necessary or appropriate to enable the appropriate Party to file, prosecute and
maintain patent applications and resulting patents with respect to Inventions
owned by a Party and for periods of time sufficient for such Party to obtain the
assistance it needs from such personnel. Where appropriate, each of GelTex and
Sankyo shall sign or cause to have signed all documents relating to said patent
applications or patents at no charge to the other Party.

         8.4 Notification of Patent Term Restoration. Each of GelTex and Sankyo
shall notify the other Party of: (a) the receipt of the Notice of Issuance of
each United States patent included within the notifying Party's Patent Rights,
giving the date of issue and patent number for each such patent; and (b) each
notice pertaining to any patent included within the notifying Party's Patent
Rights which it receives as patent owner pursuant to the Drug Price Competition
and Patent Term Restoration Act of 1984, including notices pursuant to Sections
101 and 103 of such Act from persons who have filed an abbreviated NDA. Such
notices shall be given promptly, but in any event within ten (10) business days
after receipt of each such notice pursuant to such Act. Each of GelTex and
Sankyo shall notify the other Party of each filing for patent term restoration
under such Act, any allegations of failure to show due diligence and all awards
of patent term restoration (extensions) with respect to the notifying Party's
Patent Rights.

         8.5 No Other Technology Rights. Except as otherwise expressly provided
in this Agreement, under no circumstances shall a Party, as a result of this
Agreement, obtain any ownership interest in or other right to the Patent Rights
or Technology of the other Party, including items owned, controlled or developed
by the other Party, or transferred by the other Party to said Party at any time
pursuant to this Agreement.

         8.6 Enforcement of Patent Rights. GelTex and Sankyo shall promptly
notify the other in writing of any alleged or threatened infringement of GelTex
Patent Rights or Sankyo Patent Rights of which it becomes aware.

                  8.6.1 First Right to Respond. [ * ] shall have the first
right, but not obligation, to prosecute or prevent such infringement in the
Field in the Territory. [ * ] Any action taken by [ * ] pursuant to this Section
8.6.1 shall be at the sole cost and expense of [ * ], provided, however, that
[ * ] shall have the right to participate in any such action at its own expense.
[ * ]


                                       15

[*] Confidential information omitted and filed separately with the Commission.
<PAGE>   16
CONFIDENTIAL



[ * ]

                  8.6.2 Second Right to Respond. If Sankyo does not exercise its
right to respond to such infringement within sixty (60) days of becoming aware
of or being notified of such infringement, then GelTex shall have the right, but
not the obligation, to do so at its sole expense. In such case, GelTex shall
have the right to retain for itself all amounts recovered in connection with the
infringement whether by judgment, award, decree or settlement.

                  8.6.3 Cooperation. If either Party has exercised its right to
prosecute or prevent the infringement of GelTex Patent Rights or Sankyo Patent
Rights as described in Sections 8.6.1 and 8.6.2 hereof, then the other Party
shall provide reasonable and diligent cooperation with such Party in all matters
concerning any such infringement and shall make available any relevant records,
documents, or information if requested to do so.

         8.7 Third Party Licenses.

                  8.7.1 For Identified Patents. If Sankyo is required in its
reasonable judgement or by a court of competent jurisdiction to obtain a license
from the owners, assignees or licensees of the [ * ] in order to sell Compound
in a given country, [ * ].

                  8.7.2 For All Other Patents. If Sankyo is required, in its
reasonable judgment or by a court of competent jurisdiction, to obtain a license
from a Third Party under any issued patent [ * ] in order to sell Compound in a
given country in the Territory, [ * ].


                  ARTICLE 9. INITIAL, MILESTONE AND ROYALTIES PAYMENTS

         9.1 Status of Payments. All initial payments, milestones and other
amounts payable by Sankyo under this Agreement will be non-refundable and
non-creditable against future royalty or milestone obligations. [ * ]



                                       16

[*] Confidential information omitted and filed separately with the Commission.
<PAGE>   17
CONFIDENTIAL



         9.2 Initial Payments. Sankyo shall pay GelTex $3,000,000 on or before
December 31, 1999.

         9.3 Milestone Payments. Sankyo shall pay GelTex the amounts set forth
below within thirty (30) business days following written notice from GelTex that
the applicable milestone has been achieved. Upon receipt of the first regulatory
approval to market Compound in any country in the European Union, Sankyo shall
pay GelTex [ * ] and upon receipt of regulatory approval to market Compound
in Japan, Sankyo shall pay GelTex [ * ].

         9.4 Royalties on Net Sales of the Compound in the Territory. In
consideration of the licenses granted hereunder, Sankyo agrees to pay to GelTex
during the Term a royalty on Net Sales of Compound sold by Sankyo in the
Territory at the rates set forth below:

<TABLE>
<CAPTION>
         Amount of Annual Net Sales in the Territory % of Annual Net Sales
<S>                                                                   <C>
         [ * ]
</TABLE>

         If prior to the exercise or expiration of the 279 Option, Sankyo
reasonably determines that the royalty rates set forth above are commercially
unacceptable in Japan and/or the European Union, the parties may mutually agree
to renegotiate the royalty rates for Japan and/or the European Union. However,
any decrease in the royalty rate may be accompanied by a mutually agreeable
increase in initial or milestone payments.

                            ARTICLE 10. PAYMENT TERMS

         10.1 Royalty Reports. During the Term and commencing with the first
calendar quarter in which the first commercial sale of Compound occurs, Sankyo
shall, within fifty days following the end of the calendar quarter, furnish to
GelTex a written report showing, on a country by country basis, the gross sales
of Compound sold to Third Party customers during the quarter and the calculation
of Net Sales and the amount payable as royalties pursuant to Article 9 hereof.
Within sixty days following the end of the calendar quarter, Sankyo shall pay to
GelTex the amount of royalties shown to be due thereon with annual adjustments
for discrepancies between estimated allowances booked in accordance with GAAP
and actual deductions to invoiced gross sales. If no royalties shall be due,
Sankyo shall so report.

         10.2 Records. Sankyo shall keep and maintain proper and complete
records and books of account documenting all information relating to royalties
payable hereunder. Sankyo shall permit independent accountants retained by
GelTex and acceptable to Sankyo to have access to its records and books for the
sole purpose of determining the accuracy of such royalties. Such examination
shall be during regular business hours and upon reasonable advance notice and no
more than once in each calendar year during the term of this


                                       17

[*] Confidential information omitted and filed separately with the Commission.
<PAGE>   18
CONFIDENTIAL



Agreement. The accountant shall not disclose to GelTex or any Third Party any
information except that which should properly be contained in such a report. If
such examination reveals that any royalties have been understated, any
underpayment shall be paid within thirty (30) days. GelTex shall pay the fees
and expenses of the accountant engaged to perform the audit, unless such audit
reveals an underpayment of five percent (5%) or more for the period examined, in
which case, Sankyo shall pay all reasonable costs and expenses of the
accountant.

         10.3 Payment Method. Except as otherwise provided in this Agreement or
agreed to by the Parties, all payments under this Agreement shall be made by
electronic bank transfer in United States dollars available on the date due, to
such account as GelTex specifies to Sankyo in writing within a reasonable period
before such payment is due.

         10.4 Books of Account; Audit. GelTex shall keep and maintain proper and
complete records and books of account documenting all Development Costs incurred
by it. GelTex shall permit independent accountants retained by Sankyo and
acceptable to GelTex to have access to its records and books for the sole
purpose of determining the accuracy of Development Costs charged by GelTex. Such
examination shall be during regular business hours and upon reasonable advance
notice and no more than once in each calendar year during the term of this
Agreement. The accountant shall not disclose to Sankyo or any Third Party any
information except that which should properly be contained in a report of costs
incurred. If such examination reveals that any costs including, without
limitation, Development Costs have been overstated, any overpayment shall be
refunded within thirty (30) days. Sankyo shall pay the fees and expenses of the
accountant engaged to perform the audit, unless such audit reveals an overcharge
of five percent (5%) or more for the period examined, in which case, GelTex
shall pay all reasonable costs and expenses of the accountant.


                           ARTICLE 11. CONFIDENTIALITY

         11.1. Nondisclosure Obligations. Except as otherwise provided in this
Article 11, during the Term and for a period of five (5) years thereafter, the
Parties shall maintain in confidence and use only for purposes specifically
authorized under this Agreement: (a) confidential information and data resulting
from or related to the Program and/or the development of Compound; (b) all
information and data not described in clause (a) but supplied by another Party
under this Agreement and marked "Confidential"; or (c) information that by its
nature should be considered confidential.

         For purposes of this Article 11, information and data described in
clause (a), (b) or (c) of the preceding paragraph shall be referred to as
"Information." To the extent it is reasonably necessary or appropriate to
fulfill its obligations or exercise its rights under this Agreement, a Party may
disclose Information it is otherwise obligated under this Section not to
disclose to its Affiliates, consultants, outside contractors and clinical
investigators, on a need-to-know basis and on the condition that such entities
or persons agree to keep the


                                       18
<PAGE>   19
CONFIDENTIAL



Information confidential for the same time periods and to the same extent as
such Party is required to keep the Information confidential; and a Party or its
sublicensees may disclose such Information to government or other regulatory
authorities to the extent that such disclosure is reasonably necessary to obtain
patents or authorizations to conduct clinical trials with and to market
commercially Compound. The obligation not to disclose Information shall not
apply to any part of such Information that: (i) is or becomes patented,
published or otherwise becomes publicly known other than by acts of the Party
obligated not to disclose such Information or its Affiliates in contravention of
this Agreement; (ii) can be shown by written documents to have been disclosed to
the receiving Party or its Affiliates by a Third Party, provided that such
Information was not obtained by such Third Party directly or indirectly from the
other Party under this Agreement; (iii) prior to disclosure under this
Agreement, was already in the possession of the receiving Party or its
Affiliates, provided that such Information was not obtained directly or
indirectly from the other Party under this Agreement; (iv) can be shown by
written documents to have been independently developed by the receiving Party or
its Affiliates without breach of any of the provisions of this Agreement; or (v)
is disclosed by the receiving Party or its Affiliates pursuant to a subpoena
lawfully issued by a court or governmental agency, provided that the receiving
Party or its Affiliates, as the case may be, notifies the other Parties
immediately upon receipt of any such subpoena.

         11.2 Terms of this Agreement and other Public Disclosures. The Parties
acknowledge that GelTex will be required to file this Agreement with the
Securities and Exchange Commission, and GelTex agrees to seek confidential
treatment for portions of this Agreement when making such filing upon review by
Sankyo. Except as permitted by the foregoing provisions or as otherwise required
by law, each of the Parties hereby agrees not to disclose any terms or
conditions of this Agreement to any Third Party without the prior consent of the
other Party; provided, that each Party shall be entitled to disclose the terms
of this Agreement without such consent to potential investors or other financing
sources on the condition that such entities or persons agree to keep such terms
confidential for the same time periods and to the same extent as such Party is
required to keep such terms confidential. The Parties agree to coordinate the
timing and scope of any other public disclosures discussing results of the
Program.

         11.3 Publications. Each Party recognizes the mutual interest in
obtaining valid patent protection. Consequently, any party, its employees or
consultants wishing to make a publication (including any oral disclosure made
without obligation of confidentiality) relating to work performed by such Party
as part of the Program (the "Publishing Party") shall transmit to the other
Party (the "Reviewing Party") a copy of the proposed written publication at
least forty-five (45) days prior to submission for publication, or an abstract
of such oral disclosure at least fifteen (15) days prior to submission of the
abstractor the oral disclosure. The Reviewing Party shall have the right to (a)
request a delay in publication or presentation in order to protect patentable
information, (b) propose modifications to the publication for patent reasons or
(c) request that the information be maintained as a trade secret.



                                       19
<PAGE>   20
CONFIDENTIAL



         If the Reviewing Party requests a delay as described in clause (a)
above, the Publishing Party shall delay submission or presentation of the
publication for a period of ninety (90) days to enable patent applications
protecting each Party's rights in such information to be filed. Upon the
expiration of forty-five (45) days, in the case of proposed written disclosures,
or fifteen (15) days, in the case of an abstract of proposed oral disclosures,
from transmission of such proposed disclosures to the Reviewing Party, the
Publishing Party shall be free to proceed with the written publication or the
oral presentation, respectively, unless the Reviewing Party has requested the
delay described above.

         To the extent possible in the reasonable exercise of its discretion,
the Publishing Party shall incorporate all modifications proposed under clause
(b) above. If a trade secret that is the subject of a request made under clause
(c) above cannot be otherwise protected without unreasonable expense to the
Reviewing Party, such information shall be omitted from the publication.


                   ARTICLE 12. REPRESENTATIONS AND WARRANTIES

         12.1 Authorization. Each Party warrants and represents to the other
that: (i) it has the legal right and power to enter into this Agreement, to
extend the rights and licenses granted to the other in this Agreement, and to
perform fully its obligations hereunder; (ii) this Agreement has been duly
authorized, executed and delivered and is a valid and binding agreement of such
Party, enforceable in accordance with its terms subject to applicable
bankruptcy, insolvency, reorganization, and other laws of general application
limiting the enforcement of creditor's rights; (iii) such Party has obtained all
necessary approvals to the transactions contemplated hereby; (iv) such Party has
not made nor will it make any commitments to others in conflict with or in
derogation of such rights or this Agreement; (v) GelTex Patent Rights and
Technology comprise all the intellectual property owned by GelTex which is
necessary and useful for manufacturing and commercializing Compound in the Field
and in the Territory; and (vi) GelTex is not debarred under Section 306(a) or
(b) of the Generic Drug Enforcement Act of 1992.

         12.2 Intellectual Property Rights.

                  12.2.1 Existing Rights. GelTex hereby represents and warrants
that: (i) immediately prior to the execution of this Agreement it possesses an
exclusive right, title and interest to the existing GelTex Patent Rights and the
GelTex Technology (except for licenses granted to Chemie); (ii) that the GelTex
Patent Rights and the GelTex Technology are, and during the Term will remain,
free and clear of any lien or other encumbrance; and (iii) that GelTex has the
right to enter into the obligations set forth in this Agreement and to grant the
rights and licenses set forth in Article 3 hereof.

                  12.2.2 [ * ]


[ * ] Confidential information omitted and filed separately with the Commission.


                                       20
<PAGE>   21
CONFIDENTIAL



[ * ]


         12.3 Sankyo Warranties. Sankyo warrants that Compound sold pursuant to
this Agreement will be marketed and sold in all material respects: (i) in
accordance with the conditions of any applicable Regulatory Approvals and any
applicable labeling claims; and (ii) any applicable requirements of the
Regulatory Scheme regarding the sale and/or distribution of Compound.

         12.4 Disclaimer of Representations and Warranties. EXCEPT AS OTHERWISE
EXPRESSLY SET FORTH IN THIS AGREEMENT, NEITHER GELTEX NOR SANKYO MAKES ANY
REPRESENTATIONS OR EXTENDS ANY WARRANTIES OF ANY KIND, EITHER EXPRESS OR
IMPLIED, INCLUDING WITHOUT LIMITATION WARRANTIES OF MERCHANTABILITY, FITNESS FOR
A PARTICULAR PURPOSE, AND THE NON-INFRINGEMENT OF ANY THIRD-PARTY PATENTS OR
PROPRIETARY RIGHTS. ALL UNIFORM COMMERCIAL CODE WARRANTIES ARE EXPRESSLY
DISCLAIMED BY THE PARTIES.

         12.5 Limitation of Liability. It is agreed by the Parties that neither
Party shall have a right to or shall claim special, indirect or consequential
damages, including lost profits, for breach of this Agreement. Remedies shall be
limited to claims for amounts due hereunder or as otherwise provided in this
Agreement, including claims for indemnification as provided in Article 13
hereof.


                              ARTICLE 13. INDEMNITY

         13.1 Sankyo Indemnity Obligations. Except to the extent such claims,
losses, damages or expenses result from GelTex's negligence or a breach of a
representation or warranty by GelTex, Sankyo agrees to defend, indemnify and
hold GelTex, its Affiliates, licensees and their respective directors, officers,
employees and agents harmless from all claims, losses, damages or expenses
arising out of or relating to: [ * ].

         13.2 GelTex Indemnity Obligations.

                  13.2.1 For Compound Claims. Except to the extent such claims,
losses, damages or expenses result from Sankyo's negligence or a breach of a
representation or warranty by Sankyo, GelTex agrees to defend, indemnify and
hold harmless Sankyo, its Affiliates, licensees and their respective directors,
officers, employees and agents harmless from all claims, losses, damages or
expenses arising out of or relating to [ * ]


[ * ] Confidential information omitted and filed separately with the Commission.


                                       21
<PAGE>   22
CONFIDENTIAL



[ * ]

                  13.2.2 For Intellectual Property Claims. In the event that a
claim or assertion of patent, copyright, know-how and/or trademarks infringement
is made against Sankyo by any Third Party in any country of the Territory
including any assignee or licensee of the [ * ], by reason of the making, having
made, using, selling, having sold and offering for sale the Compound by Sankyo
hereunder, [ * ].

         13.3 Procedure. Should a Party or any of its Affiliates or its
employees or agents (the "Indemnitee") intend to claim indemnification under
this Article 13, such Indemnitee shall promptly notify the other Party (the
"Indemnitor") in writing of any loss, claim, damage, liability or action in
respect of which the Indemnitee intends to claim such indemnification, and the
Indemnitor shall be entitled to assume the defense thereof with counsel selected
by the Indemnitor and approved by the Indemnitee, such approval not to be
unreasonably withheld; provided, however, that if representation of Indemnitee
by such counsel first selected by the Indemnitor would be inappropriate due to a
conflict of interest between such Indemnitee and any other party represented by
such counsel, then Indemnitor shall select other counsel for the defense of
Indemnitee, with the fees and expenses to be paid by the Indemnitor, such other
counsel to be approved by Indemnitee and such approval not to be unreasonably
withheld. The indemnity agreement in this Article 13 shall not apply to amounts
paid in settlement of any loss, claim, damage, liability or action if such
settlement is effected without the consent of the Indemnitor, which consent
shall not be withheld unreasonably. The failure to deliver notice to the
Indemnitor within a reasonable time after the commencement of any such action,
if prejudicial to its ability to defend such action, shall relieve such
Indemnitor of any liability to the Indemnitee under this Article 13, but the
omission so to deliver notice to the Indemnitor will not relieve it of any
liability that it may have to any Indemnitee otherwise than under this Article
13. The Indemnitee under this Article 13, its officers, directors, employees and
agents, shall cooperate fully with the Indemnitor and its legal representatives
in the investigation of any action, claim or liability covered by this
indemnification. In the event that each Party claims indemnity from the other
and one Party is finally held liable to indemnify the other, the Indemnitor
shall additionally be liable to pay the reasonable legal costs and attorneys'
fees incurred by the Indemnitee in establishing its claim for indemnity.

                        ARTICLE 14. TERM AND TERMINATION

         14.1 Term.

                  14.1.1 Expiration. Unless terminated earlier pursuant to
Section 14.2, this Agreement shall continue in full force and effect until the
expiration of the last of any



[ * ] Confidential information omitted and filed separately with the Commission.


                                       22
<PAGE>   23
CONFIDENTIAL



GelTex Patent Rights.

                  14.1.2 Effect of Expiration. Expiration of the Agreement shall
not relieve the Parties of any obligation accruing prior to such expiration.
Upon expiration of this Agreement in connection with Compound pursuant to
Section 14.1.1 above: (i) Sankyo shall have a paid-up non-exclusive license with
right to sublicense, under the GelTex Patent Rights and GelTex Technology to
make, have made, use, offer for sale, have sold and sell Compound the Territory
for use in the Field; and (ii) GelTex shall have a paid-up license under the
Sankyo Patent Rights and Sankyo Technology to make, have made, use, offer for
sale, have sold and sell Compound in the Territory.

         14.2 Termination. This Agreement may be terminated in the following
circumstances:

                  14.2.1 For Certain Material Breaches. If: (i) either GelTex or
Sankyo fails to use commercially reasonable and diligent efforts to perform any
material duty imposed upon such Party, or materially breaches any representation
or warranty made by such Party under this Agreement; or (ii) Sankyo fails to use
commercially reasonable to commercialize Compound in the Territory, and in any
case, such failure to perform is not cured within ninety (90) days of written
notice thereof from the non-breaching Party, the non-breaching Party may elect,
in its sole discretion, to: (i) enforce the terms of this Agreement and seek any
and all remedies available to it at law and in equity; and/or (ii) terminate
this Agreement with the consequences set forth in Section 14.3 below. Such
90-day period shall be extended to one hundred eighty (180) days if the
breaching Party has engaged in good faith efforts to remedy such default within
such 90-day period that it believes that it will be able to remedy the default
within such 180-day period, but such extension shall apply only so long as the
breaching Party is engaging in good faith efforts to remedy such default.

                  14.2.2 Upon Bankruptcy. Either GelTex or Sankyo may terminate
this Agreement upon the bankruptcy, insolvency, dissolution or winding-up of the
other Party, except in the case of a petition in bankruptcy filed involuntarily
against a Party, if such petition is dismissed within sixty (60) days of the
date of its filing.

                  14.2.3 For Changed Circumstances. Sankyo shall have the right
to terminate this Agreement if: (i) after submitting a Hart-Scott-Rodino filing
with the Federal Trade Commission (FTC), FTC does not approve the transaction as
set forth herein or requires modifications to the transaction that are
unacceptable to Sankyo, or (ii) a generic version of the Compound is approved by
the FDA and is being sold in the Territory for use in the Field. In addition,
this Agreement shall terminate upon the expiration of the unexercised 279
Option.

                  14.2.4 Following Certain Infringement Claims. This Agreement
shall be terminated as to Compound should a Patent Claim (as defined in Section
13.2.2) result in the issuance of a final injunction prohibiting the future
development and/or commercialization of



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Compound.

         14.3 Effects of Termination. Termination of the Agreement shall not
relieve the Parties of any obligation accruing prior to such expiration.

                  14.3.1 Termination by Sankyo. Upon any termination by Sankyo
pursuant to Section 14.2.1 or 14.2.2 above: [ * ]. Additionally, upon
termination by Sankyo or otherwise pursuant to Subsections 14.2.3 or 14.2.4
above: [ * ].

                  14.3.2 Termination by GelTex. Upon any termination by GelTex
pursuant to Sections 14.2.1, 14.2.2 or 7.2.2 above: [ * ]


[ * ] Confidential information omitted and filed separately with the Commission.


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                            ARTICLE 15. MISCELLANEOUS

         15.1 Exchange Controls. All payments due hereunder shall be paid in
United States dollars. If at any time legal restrictions prevent the prompt
remittance of part or all payments with respect to any country where Compound is
sold, payment shall be made through such lawful means or methods as the Parties
may determine.

         15.2 Withholding Taxes. If applicable laws require that taxes be
withheld from payments made hereunder, Sankyo shall (a) deduct such taxes, (b)
timely pay such taxes to the proper authority and (c) send written evidence of
payment to GelTex within sixty (60) days after payment. Sankyo will assist
GelTex in claiming tax refunds, deductions or credits at GelTex's request and
will cooperate to minimize the withholding tax, if available, under various
treaties applicable to any payment made hereunder.

         15.3 Force Majeure. No Party shall be held liable or responsible to the
other Party nor be deemed to have defaulted under or breached this Agreement for
failure or delay in fulfilling or performing any term of this Agreement when
such failure or delay is caused by or results from causes beyond the reasonable
control of the affected Party, including but without limitation fire, floods,
embargoes, war, acts of war (whether war is declared or not), insurrections,
riots, civil commotions, strikes, lockouts or other labor disturbances, acts of
God or acts, omissions or delays in acting by any governmental authority or one
or both of the other Parties; provided, however, that the Party so affected
shall use commercially reasonable and diligent efforts to avoid or remove such
causes of non-performance, and shall continue performance hereunder with
reasonable and diligent dispatch whenever such causes are removed. Each Party
shall provide the other Party with prompt written notice of any delay or failure
to perform that occurs by reason of force majeure. The Parties shall mutually
seek a resolution of the delay or the failure to perform as noted above. Upon
termination of force majeure, the performance of any suspended obligation or
duty shall promptly recommence. Neither Party shall be liable to the other Party
for any direct, indirect, consequential, incidental, special, punitive or
exemplary damages arising out of or relating to the suspension or termination of
any of its obligations or duties under this Agreement by reason of the
occurrence of force majeure.

         15.4 Assignment. This Agreement may not be assigned or otherwise
transferred by any Party without the consent of the other Party; provided,
however, that either GelTex or Sankyo may, without such consent, assign its
rights and obligations under this Agreement: (a) in connection with a corporate
reorganization, to any member of an affiliated group, all or substantially all
of the equity interest of which is owned and controlled by such Party or its
direct or indirect parent corporation; or (b) in connection with a merger,
consolidation or sale of substantially all of such Party's assets to an
unrelated Third Party; provided, however, that such Party's rights and
obligations under this Agreement shall be assumed by its successor in interest
in any such transaction and shall not be transferred separate from all or
substantially all of its other business assets, including those business assets
that are the subject of this Agreement. Any purported assignment in violation of
the preceding sentence shall be void.


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Any permitted assignee shall assume all obligations of its assignor under this
Agreement in writing.

         15.5 Severability. Each Party hereby agrees that it does not intend to
violate any public policy, statutory or common laws, rules, regulations, treaty
or decision of any government agency or executive body thereof of any country or
community or association of countries. Should one or more provisions of this
Agreement be or become invalid, the Parties will substitute, by mutual consent,
valid provisions for such invalid provisions, which valid provisions in their
economic effect are sufficiently similar to the invalid provisions that it can
be reasonably assumed that the Parties would have entered into this Agreement
with such valid provisions. In case such valid provisions cannot be agreed upon,
the invalidity of one or several provisions of this Agreement shall not affect
the validity of this Agreement as a whole, unless the invalid provisions are of
such essential importance to this Agreement that it is to be reasonably assumed
that the Parties would not have entered into this Agreement without the invalid
provisions.

         15.6 Notices. Any consent, notice or report required or permitted to be
given or made under this Agreement by one of the Parties hereto to the other
shall be in writing, delivered personally or by facsimile (and promptly
confirmed by personal delivery or courier) or courier, postage prepaid (where
applicable), addressed to such other Party at its address indicated below, or to
such other address as the addressee shall have last furnished in writing to the
addressor in accordance with this Section 15.6, and shall be effective upon
receipt by the addressee.

         If to GelTex:              GelTex Pharmaceuticals, Inc.
                                    153 Second Avenue
                                    Waltham, MA 02451
                                    Attention:  President
                                    Facsimile:  (781) 672-5822

         with a copy to:            GelTex Pharmaceuticals, Inc.
                                    153 Second Avenue
                                    Waltham, MA 02451
                                    Attention:  Corporate Counsel
                                    Facsimile:  (781) 895-4982

         If to Sankyo:              Sankyo Parke Davis
                                    Two Hilton Court
                                    Parsippany, NJ  07054
                                    Attention:  President
                                    Facsimile:  (973)  359-2605


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         with a copy to:            Sankyo Pharma Inc.
                                    Two Hilton Court
                                    Parsippany, NJ  07054
                                    Attention:  President
                                    Facsimile:  (973) 359-2629

         15.7 Applicable Law. This Agreement shall be governed by and construed
in accordance with the laws of the Commonwealth of Massachusetts.

         15.8 Arbitration. Any disputes arising between the Parties relating to,
arising out of or in any way connected with this Agreement or any term or
condition hereof, or the performance by either Party of its obligations
hereunder, whether before or after termination of this Agreement (a "Dispute"),
which has not resolved in accordance with the provisions of Section 4.3 hereof,
shall be finally resolved by binding arbitration as herein provided.

                  15.8.1 General. Except as otherwise provided in this Section
15.8, any arbitration hereunder shall be conducted under the commercial rules of
the American Arbitration Association. Each such arbitration shall be conducted
in the English language by a panel of three arbitrators (the "Arbitration
Panel"). Each of GelTex and Sankyo shall appoint one arbitrator to the
Arbitration Panel and the third arbitrator shall be appointed by the two
arbitrators appointed by GelTex and Sankyo. The Arbitration Panel shall be
convened upon delivery of the Notice of Arbitration (as defined below). Any such
arbitration shall be held in Boston, Massachusetts. The Arbitration Panel shall
have the authority to grant specific performance, and to allocate between the
Parties the costs of arbitration in such equitable manner as it shall determine.
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.

                  15.8.2 Procedure.

                           (a) Whenever a Party (the "Claimant") shall decide to
institute arbitration proceedings, it shall give written notice to that effect
(the "Notice of Arbitration") to the other Party (the "Respondent"). The Notice
of Arbitration shall set forth in detail the nature of the Dispute, the facts
upon which the claimant relies and the issues to be arbitrated (collectively the
"Arbitration Issues"). Within thirty (30) days of its receipt of the Notice of
Arbitration, the Respondent shall send the Claimant and the Arbitration Panel a
written Response (the "Response"). The Response shall set forth in detail the
facts upon which the Respondent relies. In addition, the Response shall contain
all counterclaims which the Respondent may have against the Claimant which are
within the Arbitration Issues, whether or not such claims have previously been
identified. If the Response sets forth a counterclaim, the Claimant may, within
thirty (30) days of the receipt of the Response, deliver to the Respondent and
the Arbitration Panel a rejoinder answering such counterclaim.



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                           (b) Within fifteen (15) days after the later of (i)
the expiration of the period provided in clause (a) above for the Claimant to
deliver a rejoinder or (ii) the completion of any discovery proceedings
authorized by the Arbitration Panel: (A) the Claimant shall send to the
Arbitration Panel a proposed resolution of the Arbitration Issues and a proposed
resolution of any counterclaims set forth in the Response (the "Claimant's
Proposal"), including the amount of monetary damages, if any, or other relief
sought; and (B) the Respondent shall send to the Arbitration Panel a proposed
resolution of the Arbitration Issues, a proposed resolution of any counterclaims
set forth in the Response and a proposed resolution of any rejoinder submitted
by the Claimant (the "Respondent's Proposal"), including the amount of monetary
damages, if any, or other relief sought. Once both the Claimant's Proposal and
the Respondent's Proposal have been submitted, the Arbitration Panel shall
deliver to each Party a copy of the other Party's proposal.

                           (c) Within fifteen (15) days after delivery of both
the Claimant's Proposal and the Respondent's Proposal, the Arbitration Panel
shall provide notice to the Claimant and the Respondent of the date of a hearing
to be held no later than sixty (60) days following the date of the notice. At
such hearing, both parties shall have the opportunity to discuss the facts
giving rise to the dispute and the proposals that have been presented. The
Arbitration Panel will determine the procedure for the hearing.

                           (d) The Arbitration Panel shall issue an opinion with
respect to any Dispute, which opinion shall explicitly accept either the
Claimant's Proposal or the Respondent's Proposal in its entirety (the "Final
Decision"). The Arbitration Panel shall not have the authority to reach a Final
Decision that provides remedies or requires payments other than those set forth
in the Claimant's Proposal or the Respondent's Proposal. The concurrence of two
(2) arbitrators shall be sufficient for the entry of a Final Decision. The
arbitrators shall issue a Final Decision within one (1) month from the later of
(i) the last day for submission of proposals under clause (b) above, or (ii) the
date of the final hearing on any Dispute held by the Arbitration Panel. A Final
Decision shall be binding on all of the Parties.

         15.9 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 the Parties.

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

         15.11 Independent Contractors. It is expressly agreed that GelTex and
Sankyo shall be independent contractors and that the relationship between the
two Parties shall not constitute a partnership, joint venture or agency. Neither
GelTex nor Sankyo 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, without the prior consent of the other Party to do


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so.

         15.12 Waivers. No delay on the part of any party in exercising any
right, power or privilege hereunder shall operate as a waiver thereof nor shall
any waiver on the part of any party of any such right, power or privilege, nor
any single or partial exercise of any such right, power or privilege, preclude
any further exercise thereof or the exercise of any other such right, power or
privilege.

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

         15.14 Interpretation. The Parties hereto acknowledge and agree that (i)
each Party and its counsel reviewed and negotiated the terms and provisions of
this Agreement and have contributed to its revision; (ii) the rule of
construction to the effect that any ambiguities are resolved against the
drafting Party shall not be employed in the interpretation of this Agreement;
(iii) the terms and provisions of this Agreement shall be construed fairly as to
all Parties hereto and not in favor of or against any Party, regardless of which
Party was generally responsible for the preparation of this Agreement.




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

                                        GELTEX PHARMACEUTICALS, INC.

                                        By:

                                        /s/ Mark Skaletsky
                                        ------------------------------
                                        Mark Skaletsky

                                        Title: President and CEO


                                        SANKYO PHARMA, INC.

                                        By:

                                        /s/ Takashi Chiba
                                        ------------------------------
                                        Takashi Chiba

                                        Title: President







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