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Technology Transfer Agreement - Rigel Pharmaceuticals Inc. and Questcor Pharmaceuticals Inc.

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                          TECHNOLOGY TRANSFER AGREEMENT


         THIS TECHNOLOGY TRANSFER AGREEMENT (the "Agreement") is made and
entered into as of the 22nd day of September, 2000 (the "Effective Date"), by
and between RIGEL PHARMACEUTICALS, INC., a Delaware corporation ("Rigel"), and
QUESTCOR PHARMACEUTICALS, INC., a California corporation ("Questcor").

         WHEREAS, Questcor has developed and owns certain proprietary antiviral
technology comprising HCV IRES and HCV NS5A-PKR and other viral technology and
owns or has licensed certain patent applications and issued patents pertaining
thereto;

         WHEREAS, Rigel desires to pursue the commercial development of certain
applications of such technology; and

         WHEREAS, Rigel desires to obtain, and Questcor is willing to assign to
Rigel, its right, title and interest, on a worldwide basis, in and to such
technology;

         NOW, THEREFORE, Rigel and Questcor hereby agree as follows:

                                  ARTICLE 1

                                 DEFINITIONS

         1.1  "AFFILIATE" means any entity that directly or indirectly Owns,
is Owned by or is under common Ownership, with a party to this Agreement,
where "Owns" or "Ownership" means direct or indirect possession of at least
fifty percent (50%) of the outstanding voting securities of a corporation or
a comparable equity interest in any other type of entity.

         1.2  "CURRENTLY IDENTIFIED COMPOUND(S)" means all compounds
identified as of the Effective Date by Questcor and provided to Rigel as
having potential antiviral activity, together with Homologs and Isomers of
such compounds. "Homolog" means a compound that differs from such Currently
Identified Compound by a -(CH(2))-group. "Isomer" means a compound that has the
same composition as such Currently Identified Compound, but differs in the
positions of aromatic ring substituents, location of double bonds or position
of carbon in alkyl groups, such as propyl and isopropyl, and optical isomers
thereof.

         1.3  "HCV IRES" means Hepatitis C Virus IRES technology.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       1.
<PAGE>

         1.4  "HCV NS5A-PKR" means regulation of Protein Kinase RNA
(PKR)-activated protein by Hepatitis C Virus Non-Structural 5A Protein.

         1.5  "LICENSED PRODUCT(S)" means any product, including without
limitation, compounds, compositions, formulations, any indication therefor,
and any associated methods or processes, developed pursuant to this
Agreement, the manufacture, use, importation or sale of which by Rigel, its
Affiliates or licensees would constitute an infringement of a Valid Claim of
a Questcor Patent or a Washington Patent.

         1.6  "MATERIAL BREACH" means the failure of Rigel to perform the
diligence obligation described in Section 2.4(c), or the failure of Rigel to
perform the research and development obligation described in Section 5.1(b),
or the failure of Rigel to perform any of the payment obligations in Sections
4.1, 4.2, 4.3, 4.4, 4.5 or 6.4, or if Sections 7.2(a) or 7.4 are not true as
of the Effective Date.

         1.7  "NET SALES" means the gross receipts received by Rigel or its
Affiliates for the sale of Licensed Products to Third Parties by Rigel or its
Affiliates, less (a) cash, trade, or quantity discounts actually given, (b)
rebates allowed or granted to governmental agencies or other payors, (c)
credits, returns, and replacements, and (d) taxes, including sales taxes and
duties, incurred by reason of the sale of such Licensed Products but
excluding taxes on income. If Licensed Products are sold in combination with
other products, the price of the Licensed Products for the purpose of
calculating Net Sales shall be deemed to be the then current price at which
the Licensed Products are sold independent of other products, or in the
absence of such independent sales prices, the portion of the sales price of
such combined product which is attributable to the Licensed Product itself.

         1.8  "QUESTCOR MATERIALS" means various reagents, samples and other
tangible materials relating to the HCV IRES, HCV NS5A-PKR and other viral
technologies, which have been, or will be transferred to Rigel, a compilation
of which has previously been provided to Rigel.

         1.9  "QUESTCOR PATENT(S)" means (a) the patents and patent
applications listed on APPENDIX C including all foreign patents and patent
applications, whether now existing or hereafter filed, corresponding to the
patents and patent applications under clause (a); (b) any provisionals,
substitutions, divisionals, reissues, reexaminations, renewals,
continuations, continuations-in-part, substitute applications and inventors'
certificates arising from, or based upon, any of the foregoing patents or
patent applications; and (c) any patents issuing from any of the foregoing
patent applications.

         1.10  "QUESTCOR TECHNOLOGY" means the Currently Identified
Compounds, the Questcor Materials and the modifications, improvements,
know-how, trade secrets, data, information and materials relating to the HCV
IRES, HCV NS5A-PKR and other viral technologies, which have been, or will be
transferred to Rigel, a compilation of which has previously been provided to
Rigel.

         1.11  "SHARES" shall mean the shares of Rigel capital stock to be
issued to Questcor pursuant to Section 4.2, and in the event the shares
initially issued to Questcor are shares of


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       2.
<PAGE>

Rigel Series E Preferred Stock, the term "Shares" shall also refer to any
shares of Rigel Common Stock issued upon conversion thereof, or any other
Rigel securities issued to Questcor in respect of its holdings of Series E
Preferred Stock.

         1.12  "THIRD PARTY" means any entity that is not a party nor an
Affiliate of a party.

         1.13  "VALID CLAIM" means a claim of an issued and unexpired patent,
which claim has not lapsed, been canceled, or become abandoned, and which
claim has not been declared invalid by a court of competent jurisdiction, and
which has not been admitted to be invalid or unenforceable through reissue or
disclaimer.

         1.14  "WASHINGTON LICENSE AGREEMENT" means that certain license
agreement dated as of April 4, 1997, by and between Questcor and the
University of Washington, as amended.

         1.15  "WASHINGTON PATENT(S)" means (a) the patents and patent
applications listed on APPENDIX D licensed by Questcor from the University of
Washington including all foreign patents and patent applications, whether now
existing or hereafter filed, corresponding to the patents and patent
applications under clause (a); (b) any provisionals, substitutions,
divisionals, reissues, reexaminations, renewals, continuations,
continuations-in-part, substitute applications and inventors' certificates
arising from, or based upon, any of the foregoing patents or patent
applications; and (c) any patents issuing from any of the foregoing patent
applications.

                                  ARTICLE 2

                            ASSIGNMENT OF RIGHTS

         2.1  ASSIGNMENT OF PATENT RIGHTS. Questcor hereby sells and assigns
to Rigel all of its right, title and interest in and to the Questcor Patents.
Questcor further agrees to promptly execute, upon each request by Rigel,
assignment and other documents, testify and take other acts at Rigel's
expense and as reasonably requested by Rigel, in order to apply for and
obtain, in Rigel's name and for its benefit, patents, trade secrets and other
intellectual property rights throughout the world related to the Questcor
Patents and to transfer, effect, confirm, perfect, record, preserve, protect
and enforce all rights, title and interests transferred hereunder. Questcor
hereby further sells and assigns to Rigel its rights to enforce the Questcor
Patents for any infringement occurring prior to the Effective Date.

         2.2  ASSIGNMENT OF QUESTCOR TECHNOLOGY. Questcor hereby sells and
assigns to Rigel all of its right, title and interest in and to the Questcor
Technology. Following such assignment, Rigel shall have the right to practice
the Questcor Technology without restriction. Questcor hereby further sells
and assigns to Rigel its rights to enforce any misappropriation of Questcor
Technology occurring prior to the Effective Date.

         2.3  WASHINGTON PATENT RIGHTS.

              (a)  Questcor hereby agrees to assign the Washington License
Agreement to Rigel, and will use its reasonable best efforts to obtain the
consent of the University of


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       3.
<PAGE>

Washington to such assignment, as provided for in Section 20.4 of that
agreement. Rigel agrees to cooperate with Questcor in obtaining such
assignment.

              (b)  If the assignment of the Washington License Agreement to
Rigel, with the consent of the University of Washington, under the same
terms, conditions and obligations as enjoyed by Questcor, is not effected
within ninety (90) days of the Effective Date, without the payment of
consideration to the University by Rigel, then within ninety-five (95) days
of the Effective Date, Questcor shall make available to Rigel an exclusive
sublicense of all of its rights to the Washington License Agreement, without
further consideration. If Questcor fails to offer such an assignment or
sublicense of the Washington License Agreement to Rigel within ninety-five
(95) days of the Effective Date, Rigel may elect to terminate this Agreement
pursuant to Article 9.

         2.4  DILIGENCE.

              (a) Rigel shall use commercially reasonable efforts to enforce,
defend, prosecute, and maintain the Questcor Patents and to enforce the
Questcor Technology.

              (b) In addition to the requirements specified in this
Agreement, Rigel shall promptly proceed with the research, development,
manufacture, and sale of Licensed Products, and the development and other
commercial exploitation of the Questcor Patents and Questcor Technology.

              (c) Within two years of the Effective Date, Rigel shall make a
presentation to at least six (6) Third Parties that are pharmaceutical or
biotechnology companies, and, if appropriate, have follow-up discussions with
those same companies, including not more than three companies that may be
identified by Questcor in writing to Rigel within sixty (60) days of the
Effective Date, regarding opportunities to cooperate or collaborate with
Rigel in the commercial development of Licensed Products, Questcor
Technology, or to license such rights from Rigel. Rigel shall report to the
Joint Program Management Team regarding the results of such presentations to
Third Parties.

              (d) During the two-year period from 2001 through 2002, Rigel
shall make expenditures for research and development of Licensed Products as
specified in Article 5.1(b) herein.

                                ARTICLE 3

                      DELIVERY OF QUESTCOR TECHNOLOGY

         3.1  TECHNOLOGY DELIVERY. Promptly after the Effective Date,
Questcor shall deliver and transfer possession and ownership to Rigel of all
tangible manifestations of the Questcor Patents (as listed in Appendix C) and
the Questcor Technology (as listed in Appendix E), including, without
limitation, samples of the Currently Identified Compounds and the Questcor
Materials in the amounts and in the forms specified in Appendix A and B,
respectively.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       4.
<PAGE>

Questcor shall complete the delivery of the Questcor Technology to Rigel
within sixty (60) days of the Effective Date.

         3.2  COMPLETION OF TECHNOLOGY DELIVERY. Rigel will deem the delivery
of Questcor Technology complete when it has verified receipt of all materials
and information listed in Appendix E, which in no event shall be later than
forty-five (45) days after initial delivery of all of the items listed in
Appendix E. Rigel agrees that in the event that Rigel identifies any
materials or information that are not included in such initial delivery,
Rigel will promptly notify Questcor of such omission. Questcor agrees that in
the event it receives any such notification, it will use its commercially
reasonable efforts to promptly deliver such identified omitted materials or
information to Rigel.

         3.3  AVAILABILITY OF QUESTCOR PERSONNEL. Questcor will make its
appropriate employees reasonably available to provide technical advice and
assistance relating to the transferred technology as set forth in Sections
3.1 and 3.2. Following completion of technology transfer according to Section
3.2, for one year from the Effective Date, Questcor will use its commercially
reasonable efforts to make available its employees to Rigel to provide
technical advice and assistance relating to the operation of transferred
technology. Rigel will pay Questcor $100 per hour of technical advice and
assistance provided by Questcor's employees hereunder. Such employees shall
sign a confidentiality agreement directly with Rigel to cover Rigel
confidential information. Questcor hereby consents to Rigel engaging Questcor
consultants to assist in such technology transfer under arrangements agreed
to directly between Rigel and such consultants.

                               ARTICLE 4

                             CONSIDERATION

         4.1  INITIAL PAYMENT. Upon execution of this Agreement Rigel shall
pay to Questcor as an up-front fee, [ * ], in consideration for the rights to
the Questcor Patents, the Currently Identified Compounds, the Questcor
Technology and the Washington License Agreement. Such payment will be
non-creditable and non-refundable.

         4.2  DELIVERY PAYMENT. Rigel shall issue to Questcor $500,000 in
Rigel equity, in the form of 83,333 shares of Rigel Series E Preferred Stock
(valued for this purpose at $6.00 per share), or, if the outstanding shares
of Rigel Series E Preferred Stock shall have converted into Common Stock
prior to the date that payment is due under this Section 4.2, the shares of
Common Stock issuable upon conversion of 83,333 shares of Rigel Series E
Preferred Stock, upon the earlier of: (i) complete transfer of Questcor
Technology pursuant to Section 3.2, if Questcor has executed either an
assignment or sublicense of the Washington License Agreement according to
Section 2.3(a) or Section 2.3(b), or (ii) execution of either an assignment
or sublicense of the Washington License Agreement according to Section 2.3(a)
or Section 2.3(b), if complete transfer of Questcor Technology pursuant to
Section 3.2 has occurred.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       5.
<PAGE>

         4.3  MILESTONE PAYMENTS. Rigel will pay Questcor the following
amounts within thirty (30) days of the occurrence of the following milestone
events with respect to the first Licensed Product to reach such milestone:

              (a) Licensed Product utilizing a Currently Identified Compound:



                  Milestone                                 Amount
          ---------------------------------------------   ----------
                                                      
          -   Preclinical Selection                       $1,000,000

          -   Start of Phase I clinical trial             $2,000,000

          -   Start of Phase III clinical trial           $2,000,000

          -   NDA Filing                                  $5,000,000

          -   After annual sales exceed $100 Million or   $7,000,000
              cumulative sales exceed $200 Million,
              whichever is first


As used herein, "Preclinical Selection" means successful completion of
IND-enabling toxicity studies.

              (b) Licensed Products not utilizing any Currently Identified
Compounds:



                  Milestone                                 Amount
          ---------------------------------------------   ----------
                                                      
          -   Start of Phase I clinical trial             $1,000,000

          -   Start of Phase III clinical trial           $1,000,000

          -   NDA Filing                                  $2,500,000

          -   After annual sales exceed $100 Million or   $3,500,000
              cumulative sales exceed $200 Million,
              whichever is first


Rigel will make a milestone payment only once for each milestone event,
regardless of the number of Licensed Products.

         4.4  ROYALTIES. As additional consideration for the rights to the
Questcor Patents assigned to Rigel pursuant to Article 2 (Assignment), Rigel
will pay to Questcor royalties on Net Sales by Rigel or its Affiliates of
Licensed Products that are covered in whole or in part by a Valid Claim in
the Questcor Patents or the Washington Patents. The royalties will be paid at
the following rates:


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       6.
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              (a) Licensed Product utilizing a Currently Identified Compound:



                  Portion of Annual Net Sales               Royalty
          ---------------------------------------------   -----------
                                                      

          -   On Net Sales less than $100,000,000             4%

          -   On Net Sales $100,000,000 -- $500,000,000       6%

          -   On Net Sales greater than $500,000,000         10%


              (b) Licensed Products not utilizing a Currently Identified
Compound:



                  Portion of Annual Net Sales               Royalty
          ---------------------------------------------   -----------
                                                      


          -   On Net Sales less than $100,000,000             3%

          -   On Net Sales $100,000,000 -- $500,000,000       5%

          -   On Net Sales greater than $500,000,000          8%



In the event of a license by Rigel to a non-Affiliate, this Section 4.4 will
not apply to any Licensed Product developed pursuant to such license, and
instead Rigel shall make payments regarding such Licensed Product in
accordance with Section 4.5.

         4.5  LICENSE FEES. In the event that Rigel, or its Affiliates, at
its sole discretion, licenses all or part of the Questcor Patents or
Washington Patents to a Third Party for research, development, and/or
commercialization, Rigel will pay Questcor a portion of the license fees
received by Rigel as follows:

              (a) if the license granted to the Third Party includes the
right to commercialize Currently Identified Compounds, Rigel will pay
Questcor 35% of all upfront and milestone cash payments received by Rigel and
35% of royalties received by Rigel based on Net Sales of Licensed Products
that are covered in whole or in part by a Valid Claim in the Questcor Patents
or the Washington Patents;

              (b) if the license granted to the Third Party includes the
right to practice Questcor Technology which is then covered by a Valid Claim
of a Questcor Patent or a Washington Patent but excludes the right to
commercialize Currently Identified Compounds, Rigel will pay Questcor 25% of
all upfront and milestone cash payments received by Rigel and 25% of
royalties received by Rigel based on Net Sales of Licensed Products that are
covered in whole or in part by a Valid Claim in the Questcor Patents or the
Washington Patents, provided,


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       7.
<PAGE>

however that none of the following events has occurred: (1) Rigel has spent
over $1,000,000 in internal and external research expenses on the Antiviral
Program (as defined in Article 5); or (2) twelve months have passed from the
Effective Date; or (3) Rigel includes in such license intellectual property
developed solely by Rigel subsequent to the Effective Date;

              (c) if the license granted to the Third Party includes the
right to practice Questcor Technology which is then covered by a Valid Claim
of a Questcor Patent or a Washington Patent but excludes the right to
commercialize Currently Identified Compounds, and where any of the events
specified in the proviso of Section 4.5(b) has occurred, Rigel will pay
Questcor 15% of all upfront and milestone cash payments received by Rigel and
15% of royalties received by Rigel based on Net Sales of Licensed Products
that are covered in whole or in part by a Valid Claim in the Questcor Patents
or the Washington Patents; and

              (d) in the event Rigel or its Affiliates license all or part of
the Questcor Patents or the Washington Patents to a Third Party at a time
when one or more applications for a Questcor Patent or a Washington Patent
remains pending, and no payment is due under (a), (b) or (c), then promptly
following the issuance of such patent the parties shall reasonably determine
in good faith whether a payment would have been due under (a), (b) or (c)
above if such patent had issued prior to the granting of such license. If
such a payment would have been due, Rigel shall then promptly make payments
under this Section 4.5 as if such patent had issued prior to the granting of
the license.

         4.6  DATE OF PAYMENT. Payment of the royalties and fees specified in
Sections 4.4 and 4.5 will be made by Rigel or its Affiliates to Questcor
within thirty (30) days after March 31, June 30, September 30 and December 31
of each year during the term of this Agreement, for the Net Sales received by
Rigel during the previous calendar quarter. Each quarterly payment will be
accompanied by a written statement by Rigel detailing Net Sales received by
Rigel for which such royalties and fees are due.

         4.7  RECORDS; DISCREPANCY PAYMENTS. Rigel will keep, and require its
Affiliates and licensees to keep, complete and accurate records of the Net
Sales of Licensed Products, as set forth in this Article. Following
reasonable advance written notice to Rigel, Questcor will have the right, at
its cost and expense, through an independent national firm of certified
public accountants reasonably acceptable to Rigel and bound by obligations of
confidentiality not to disclose Rigel's records, to examine such records once
per calendar year during regular business hours, during the period of time
during which such payments are due and payable hereunder and for two (2)
years thereafter. Notwithstanding the preceding sentence: (i) if such
examination reveals an underpayment by Rigel to Questcor, Rigel will promptly
pay such underpayment amount to Questcor; (ii) if such examination reveals an
underpayment of five percent (5%) or more, Rigel will also pay the costs of
such examination; and (iii) if such examination reveals an overpayment by
Rigel, Questcor will promptly remit such overpayment to Rigel.

         4.8  PAYMENT CURRENCY AND METHOD. Unless otherwise provided for
herein, and subject to foreign exchange regulations then prevailing, all
payments payable under this Agreement will be paid in cash in U.S. dollars.
All payments provided for herein shall be made by check or wire transfer.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       8.
<PAGE>

         4.9  LATE PAYMENTS. In the event of a late payment due hereunder,
the party from whom the payment is due will pay to the other party interest
at the lower of: (a) the highest rate permitted by law; or (b) the prime rate
charged by Citibank, N.A. as stated in The Wall Street Journal, New York
edition, on the date such payment is due (or the immediately preceding
business date if such payment date is not a business day) plus two percent
(2%), in either case on the outstanding balance until such late payment and
such interest accrued thereon is paid in full to the party to whom the
payment is owed. The acceptance by the party to whom the payment is made of
any such late payment will not act as a waiver of any rights such party may
have hereunder due to a breach by the party from whom the payment is due
relating to such late payment.

                                  ARTICLE 5

                           RESEARCH AND DEVELOPMENT

         5.1  RIGEL RESEARCH AND DEVELOPMENT PROGRAM.

              (a) Rigel will assume primary responsibility (directly or
through licensees) for research and development of Licensed Products. Rigel
will commit high-throughput screening, chemistry, virology, and other
discovery research, and preclinical and clinical development resources to
this anti-viral program (the "Antiviral Program") consistent with the
resources it commits to other similar research programs at Rigel. Any efforts
by Rigel licensees directed toward the Antiviral Program shall be treated as
efforts of Rigel under this Section 5.1.

              (b) During the two-year period of calendar years 2001 and 2002,
Rigel will spend, or have executed firm commitments to spend, a total of two
million dollars ($2,000,000) in research and development expenses related to
the Questcor Technology and the development of Licensed Products.

         5.2  JOINT PROGRAM MANAGEMENT TEAM. Questcor and Rigel will each
designate up to three and no less than two representatives to a Joint Program
Management Team that will oversee the activities of the Antiviral Program and
seek to ensure that goals are set appropriately and timelines are met. The
Joint Program Management Team will also oversee Rigel's business development
obligations as set forth in Section 2.4. The Joint Program Management Team
will meet periodically, but at least four times a year, at times to be agreed
upon. In conjunction with each meeting, Rigel will make reports to the Joint
Program Management Team in sufficient detail so as to determine compliance by
Rigel under this Article 5 and Section 2.4. This Section 5.2 shall expire
upon the commencement of the first Phase I clinical trial of a product
arising from the Antiviral Program.

         5.3  ACCESS TO QUESTCOR PERSONNEL. Rigel will have access to certain
Questcor employees and consultants on a consulting basis as specified in
Section 3.3.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       9.
<PAGE>

                               ARTICLE 6

                    PATENT PROSECUTION AND MAINTENANCE

         6.1  PATENT PROSECUTION. Rigel shall have the sole right to
prosecute and maintain patents and applications included in the Questcor
Patents.

         6.2  PATENT MAINTENANCE. Rigel shall have the sole right to maintain
and enforce any issued Questcor Patents at Rigel's own expense.

         6.3  WASHINGTON PATENTS. Subject to the approval of the University
of Washington, Rigel shall have the same rights and obligations to prosecute,
maintain and enforce the Washington Patents as Questcor currently has under
the Washington License Agreement or such other specification of such rights
as Rigel and the University of Washington may agree.

         6.4  REIMBURSEMENT OF PATENT EXPENSES. Rigel will reimburse Questcor
for all of Questcor's expenses associated with preparing, maintaining,
prosecuting, enforcing and defending the Questcor Patents that Questcor
incurred prior to the Effective Date. Rigel will also reimburse Questcor for
the patent expenses paid by Questcor under the Washington License Agreement
that Questcor incurred prior to the effective date of such assignment (or
exclusive sublicense). Rigel will pay Questcor under this section within
thirty (30) days after receiving an itemized accounting of each set of prior
patent expenses. The total amount reimbursed to Questcor under this Section
6.4 shall not exceed $250,000.

                                   ARTICLE 7

                         REPRESENTATIONS AND WARRANTIES

         7.1  QUESTCOR REPRESENTATIONS AND WARRANTIES. Questcor hereby
represents and warrants to Rigel as follows:

              (a) TECHNOLOGY OWNERSHIP. (i) Questcor owns all right, title
and interest in and to the Questcor Patents and Questcor Technology listed on
APPENDICES A, B AND C; (ii) it has not granted any license under the Questcor
Patents and is under no obligation to grant any such license to any Third
Party, (iii) there are no outstanding liens, encumbrances, agreements or
understandings of any kind, either written, oral or implied, regarding the
Questcor Patents or Questcor Technology that are inconsistent or in conflict
with any provision of this Agreement;

              (b) EMPLOYEES AND CONSULTANTS. Each of the Questcor employees
and consultants who contributed to the development of the Questcor Technology
performed such work under a written agreement with Questcor that assigned to
Questcor all of such individual's right, title and interest in and to such
technology;

              (c) PATENT DISCLOSURES. To the best of its knowledge, the
Questcor Patents were filed prior to any publication of the inventions
described therein or other act that would bar the issuance of a patent
thereon; complies as to form with the requirements of a patent


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       10.
<PAGE>

application filed in the United States Patent and Trademark Office; and makes
all necessary disclosures for a patent application;

              (d) INVENTION ASSIGNMENTS. The Questcor Patents properly
identify the inventors of the inventions described therein, and such
inventors have assigned to Questcor all of their right, title and interest in
and to such patent rights;

              (e) WASHINGTON LICENSE AGREEMENT. As of the Effective Date, the
Washington License Agreement is in full force and effect, and there has been
no material breach by either party to the Washington License Agreement; and

              (f) PATENT PROCEEDINGS AND THIRD PARTY CLAIMS. To the best of
its knowledge, no patent application within the Questcor Patents or the
Washington Patents is the subject of any pending interference, opposition,
cancellation or other protest proceeding. Questcor further represents and
warrants that, it has not received and is not aware of any Third Party claims
that the practice of the Patents infringes any proprietary rights of such
Third Party.

         7.2  MUTUAL REPRESENTATIONS AND WARRANTIES.  Each party hereby
represents and warrants:

              (a) DUE AUTHORIZATION. Such party is duly authorized to execute
and deliver this Agreement and to perform its obligations hereunder.

              (b) BINDING AGREEMENT; NO CONFLICT. This Agreement is a legal
and valid obligation binding upon it and enforceable in accordance with its
terms. The execution, delivery and performance of this Agreement by such
party does not conflict with any agreement, instrument or understanding, oral
or written, to which it is a party or by which it may be bound, nor violate
any law or regulation of any court, governmental body or administrative or
other agency having jurisdiction over it.

         7.3  INVESTMENT REPRESENTATIONS.

              (a) Questcor is acquiring the Shares for its own account, and
not as nominee or agent, for investment and not with a view to, or for resale
in connection with, any distribution or public offering thereof within the
meaning of the Securities Act of 1933, as amended (the "Securities Act"). In
this regard:

                       (i) Questcor understands that (i) the Shares have not
been registered under the Securities Act by reason of a specific exemption
therefrom, that such securities must be held by it indefinitely, and that
Questcor must, therefore, bear the economic risk of such investment
indefinitely, unless a subsequent disposition thereof is registered under the
Securities Act or is exempt from such registration; (ii) each certificate
representing the Shares will be endorsed with the following legends:

                                (1) THE SECURITIES REPRESENTED HEREBY HAVE
NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"),
OR UNDER THE SECURITIES LAWS OF CERTAIN STATES. THESE


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       11.
<PAGE>

SECURITIES ARE SUBJECT TO RESTRICTIONS ON TRANSFERABILITY AND RESALE AND MAY
NOT BE TRANSFERRED OR RESOLD EXCEPT AS PERMITTED UNDER THE ACT AND THE
APPLICABLE STATE SECURITIES LAWS, PURSUANT TO REGISTRATION OR EXEMPTION
THEREFROM. THE ISSUER OF THESE SECURITIES MAY REQUIRE AN OPINION OF COUNSEL
IN FORM AND SUBSTANCE SATISFACTORY TO THE ISSUER TO THE EFFECT THAT ANY
PROPOSED TRANSFER OR RESALE IS IN COMPLIANCE WITH THE ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.

                                (2) THE SECURITIES REPRESENTED BY THIS
CERTIFICATE ARE SUBJECT TO THE TERMS AND CONDITIONS, INCLUDING RESTRICTIONS
ON TRANSFERABILITY, OF THAT CERTAIN TECHNOLOGY TRANSFER AGREEMENT, DATED
SEPTEMBER 22, 2000. A COPY OF SUCH TECHNOLOGY TRANSFER AGREEMENT WILL BE
FURNISHED TO THE RECORD HOLDER OF THIS CERTIFICATE WITHOUT CHARGE UPON
WRITTEN REQUEST TO RIGEL PHARMACEUTICALS, INC. AT ITS PRINCIPAL PLACE OF
BUSINESS.

                                (3) Any legend required to be placed thereon
by Rigel's By-laws (and shown on Exhibit A hereto or as may hereafter be
added to such By-laws with respect to all Common Stock of Rigel) or under
applicable state securities laws;

and (iii) Rigel will instruct any transfer agent not to register the transfer of
the Shares (or any portion thereof) unless the conditions specified in the
foregoing legends are satisfied, until such time as a transfer is made, pursuant
to the terms of this Agreement, and in compliance with Rule 144 or pursuant to a
registration statement or, if the opinion of counsel referred to above is to the
further effect that such legend is not required in order to establish compliance
with any provisions of the Act or of this Agreement.

                       (ii) Questcor has been furnished with such materials
and has been given access to such information relating to Rigel as it has
requested, and Questcor has been afforded the opportunity to ask questions
regarding Rigel and the Shares, all as it has found necessary to make an
informed investment decision.

                       (iii) Questcor is itself a research stage
biotechnology company, and acknowledges that it can bear the economic risk of
its investment and has such knowledge and experience in financial or business
matters that it is capable of evaluating the merits and risks of the
investment in the Shares.

                       (iv) Questcor is an "accredited investor" as such term
is defined in Rule 501 of the General Rules and Regulations prescribed by the
Securities and Exchange Commission pursuant to the Act, and Questcor was not
formed for the specific purpose of acquiring the Shares.

              (b) STAND OFF; RESTRICTION ON TRANSFER. If so requested by
Rigel or any managing underwriter of Rigel's initial public offering of
securities, Questcor shall not sell or otherwise transfer any of the Shares
or other securities of Rigel during a period of up to 180 days following the
effective date of the registration statement covering such initial public
offering. If


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       12.
<PAGE>

so requested, Questcor shall execute a form of standstill agreement directly
with such managing underwriter, provided that the duration of such agreement
shall not exceed such 180-day period and that each of the officers and
directors of Rigel has executed an equivalent standstill agreement. Questcor
shall not sell, assign or otherwise transfer the Shares to any other person
(other than a sale to the general public under Rule 144 or in an acquisition
or reorganization of Rigel) without the prior consent of Rigel, which shall
not be unreasonably withheld but may be conditioned on the execution by the
transferee of an undertaking as set forth in this Section 7.3(b).

         7.4  RIGEL REPRESENTATION AND COVENANT.

              (a) REPRESENTATION. All corporate action on the part of Rigel,
its officers, directors and stockholders necessary for the authorization,
execution and delivery of this Agreement has been taken. The Shares which
will be acquired by Questcor hereunder, when issued, sold and delivered in
accordance with the terms hereof for the consideration expressed herein, will
be duly authorized, validly issued, fully paid and nonassessable.

              (b) COVENANT. With a view to making available to Questcor the
benefits of Rule 144 and any other rule or regulation of the Securities and
Exchange Commission that may permit Questcor to sell the Shares to the public
without registration, the Company agrees to make and keep public information
available, as those terms are defined in Rule 144, at all times after ninety
(90) days after the effective date of the first registration statement filed
by Rigel for the offering of its Common Stock to the general public.

         7.5  DISCLAIMER. EXCEPT AS SPECIFIED HEREIN, QUESTCOR EXPRESSLY
DISCLAIMS ANY AND ALL WARRANTY, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
TO THE IMPLIED WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE, AND NON-INFRINGEMENT. EXCEPT AS SPECIFIED HEREIN, QUESTCOR DOES NOT
WARRANT OR REPRESENT THE PATENTABILITY, VALIDITY, SCOPE, OR USEFULNESS OF THE
QUESTCOR PATENTS OR QUESTCOR TECHNOLOGY.

                                 ARTICLE 8

                        INDEMNIFICATION AND LIABILITY

         8.1  INDEMNITY. Rigel agrees to indemnify, hold harmless and defend
Questcor against any and all Third Party claims, suits, losses, damages,
costs, fees and expenses (collectively, "Claims") resulting from the
possession, manufacture, use, sale, offer for sale, import or administration
of Licensed Products by Rigel, its Affiliates or its licensees, including,
but not limited to, any claims with respect to death or injury to any person
and damage to any property of any end user of Licensed Products or customer
of such end user, provided, however, that Rigel shall not have any obligation
of indemnification with respect to liability caused in whole or in part by
the intentional wrongdoing or negligence of Questcor.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       13.
<PAGE>

         8.2  PROCEDURE. If Questcor desires to make a claim under Section
8.1, it shall give Rigel prompt notice of such claim and all related
information known to Questcor and shall permit Rigel to control the defense
and settlement of such matter.

         8.3  LIMITATION OF LIABILITY. IN NO EVENT SHALL EITHER PARTY, ITS
DIRECTORS, OFFICERS, EMPLOYEES, AGENTS, LICENSEES OR AFFILIATES BE LIABLE TO
THE OTHER PARTY FOR ANY INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY OR
CONSEQUENTIAL DAMAGES, WHETHER BASED UPON A CLAIM OR ACTION OF CONTRACT,
WARRANTY, NEGLIGENCE, STRICT LIABILITY OR OTHER TORT, OR OTHERWISE, ARISING
OUT OF THIS AGREEMENT.

                                  ARTICLE 9

                             TERM AND TERMINATION

         9.1  TERM. The term of this Agreement shall commence upon the
Effective Date and shall continue in effect until the last to expire of the
claims of the Questcor Patents or the Washington Patents, unless otherwise
terminated by a Party.

         9.2  TERMINATION AT RIGEL'S OPTION. Upon written notice to Questcor,
Rigel may terminate this Agreement if: (i) the Washington License Agreement
is not assigned or sublicensed in a manner acceptable to Rigel within
ninety-five (95) days of the Effective Date, as set forth in Section 2.3(b);
or (ii) the technology transfer described in Article 3 is not completed
within sixty (60) days of the Effective Date.

         9.3  ROYALTY TERM. Upon the expiration of the Questcor Patents and
the Washington Patents, Rigel will have no further obligation to make any
payment to Questcor under this Agreement in respect of Net Sales, apart from
those payments that are accrued hereunder but unpaid by the date of such
expiration, for which payments Rigel will remain liable.

         9.4  MATERIAL BREACH: NOTICE, ARBITRATION, TERMINATION:

              (a) In addition to its other rights and remedies, either party
(the "Non-Breaching Party") may terminate this Agreement following at least
sixty (60) days (the "Notice Period") prior written notice (the "Notice of
Breach") to the other party (the "Breaching Party") in the event that the
Breaching Party has committed a Material Breach under this Agreement and the
Breaching Party fails to cure such breach within such Notice Period.

              (b) If the Breaching Party, in good faith, disputes the
assertion that a Material Breach has occurred, it shall respond in writing to
the Notice of Breach within thirty (30) days of receipt of the Notice of
Breach. If the Non-Breaching Party still contends a Material Breach has
occurred, the Chief Executive Officers of the parties (or their designees)
shall confer within forty-five (45) days of receipt of the original Notice of
Breach. If the Chief Executive Officers are unable to resolve the dispute,
the Breaching Party may give notice, prior to completion of the 60-day Notice
Period, that it is invoking the Arbitration provision of Section 11.3 below
on the issue of the Material Breach. The Non-Breaching Party's right to
terminate this agreement is suspended during the pendency of the Arbitration
Proceedings.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       14.
<PAGE>

              (c) Upon giving such notice of Arbitration the Breaching Party
shall place into escrow any payments that the Non-Breaching Party has
asserted it is due under the Notice of Breach.

              (d) If the Arbitration rules that no Material Breach has
occurred the funds shall be released from escrow to the Breaching Party, and
the Notice of Breach shall have no force or effect.

              (e) If the ruling of the Arbitration is that a Material Breach
has occurred:

                       (i) the funds (or the appropriate portion of the
funds) held in escrow and due the Non-Breaching Party shall be released to
the Non-Breaching Party, and

                       (ii) The Breaching Party shall pay the reasonable
costs of the Arbitration of the Non-Breaching Party, and

                       (iii) The Breaching Party may either:

                                  (1) accept a termination of the Agreement
if requested by the Non-Breaching Party, or

                                  (2) agree to abide by the ruling of the
Arbitration with respect to the issue of the Material Breach

                       (iv) If the Breaching Party agrees to abide by the
ruling of the Arbitration, the Notice of Breach shall be considered withdrawn
and the Agreement shall continue in effect as interpreted by the Arbitration
ruling, and the Breaching Party shall have no further right to invoke the
Arbitration provision of this Agreement on the issue or issues decided by the
Arbitration.

              (f) If Questcor terminates this Agreement pursuant to a
Material Breach by Rigel, upon request by Questcor, Rigel will assign all
rights in the Questcor Patents, the Washington Patents, and the Questor
Technology back to Questcor.

         9.5  EFFECT OF TERMINATION. Termination of this Agreement under
Section 9.2 or Section 9.4 by reason of Material Breach by Rigel will not
terminate any licenses granted hereunder by Rigel to Third Parties. Questcor
shall accept assignment of such Third Party Licenses from Rigel to Questcor,
or renegotiate such licenses on substantially equivalent economic terms as
were contained in the original Licenses from Rigel. Termination of this
Agreement will not affect any rights or obligations of the parties accrued
prior to the effective date of such termination, including without
limitations obligations with respect to payments accrued hereunder prior to
the effective date of such termination. In the event of Termination under
Section 9.2 or Section 9.4 by reason of Material Breach by Rigel, Rigel will
promptly cease any use of the Questcor Technology and return the Questcor
Technology to Questcor.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       15.
<PAGE>

         9.6  SURVIVING OBLIGATIONS. Article 1 (Definitions), Section 4.7
(Records; Discrepancy Payments), Article 9 (Term and Termination), Article 10
(Confidentiality), and Article 11 (Dispute Resolution) will survive
expiration or termination of this Agreement.

                                 ARTICLE 10

                               CONFIDENTIALITY

         10.1  CONFIDENTIAL INFORMATION. Questcor shall not disclose any of
the Questcor Technology, the Questcor Patent applications or Washington
Patent applications (hereinafter referred to as the "Confidential
Information") to any Third Party without prior the written consent by Rigel
or as permitted by Section 10.2.

         10.2  PERMITTED DISCLOSURES.  Questcor shall not be obligated to
keep confidential any information which:

               (a) is now, or hereafter becomes, through no breach of any
confidentiality obligation on the part of Questcor, generally known or
available;

               (b) is hereafter furnished to Questcor by a Third Party, as a
matter of right and without breach of any confidentiality obligation by such
Third Party;

               (c) is the subject of a written permission to disclose
provided by Rigel;

               (d) is in response to a valid order of a court or other
governmental body of the United States or any political subdivision thereof;
PROVIDED, HOWEVER, that the responding party shall first have given notice to
the other party hereto and shall have made a reasonable effort to obtain a
protective order requiring that the Confidential Information so disclosed be
used only for the purposes for which the order was issued; or

               (e) is otherwise required by law or regulation to be disclosed
(including without limitation disclosures required by regulations promulgated
by the U.S. Securities and Exchange Commission).

         10.3  RIGEL'S OBLIGATIONS. Rigel shall treat the Confidential
Information at the same level of confidentiality as it does its other
confidential information.

                              ARTICLE 11

                        MISCELLANEOUS PROVISIONS

         11.1  COMPLIANCE WITH LAW. Each party agrees to comply with all
applicable federal, state and local law, regulations, and orders, including
such law, regulations and orders relating to the research, development and
commercial exploitation of Licensed Products.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       16.
<PAGE>

         11.2  GOVERNING LAW. This Agreement shall be governed and construed
in accordance with the laws of the State of California, as applied to
contracts executed and performed entirely within the State of California,
without regard to conflicts of laws rules.

         11.3  DISPUTE RESOLUTION. The parties agree that any dispute or
controversy arising out of or relating to any interpretation, construction,
performance, breach, or Material Breach of this Agreement shall be settled by
arbitration to be held in San Francisco, California, in accordance with the
Commercial Rules then in effect of the American Arbitration Association. The
arbitrator may grant injunctions or other relief in such dispute or
controversy. The decision of the arbitrator shall be final, conclusive, and
binding on the parties to the arbitration. Judgment may be entered on the
arbitrator's decision in any court of competent jurisdiction. Questcor and
Rigel shall each pay one-half of the costs and expenses of such arbitration
(including the arbitrator's fees), and each shall separately pay its
respective attorneys' fees and expenses.

         11.4  ASSIGNMENT. Except as otherwise provided herein, this
Agreement may not be assigned in part or in whole by any party without the
prior written consent of the other party; PROVIDED, HOWEVER, that either
party may assign this Agreement to any of its Affiliates or to any successor
by merger or sale of substantially all of its business unit to which this
Agreement relates. This Agreement will be binding upon the successors and
permitted assigns of the parties and the name of a party appearing herein
will be deemed to include the names of such party's successors and permitted
assigns to the extent necessary to carry out the intent of this Agreement.
Any assignment which is not in accordance with this Section 11.4 will be void.

         11.5  NOTICES. All notices and other communications hereunder will
be in writing and will be deemed given if delivered personally or by
facsimile transmission (receipt verified), telexed, or sent by express
courier service, to the parties at the following addresses (or at such other
address for a party as will be specified by like notice; provided, that
notices of a change or address will be effective only upon receipt thereof):

                           If to Rigel, addressed to:

                           Rigel Pharmaceuticals, Inc.
                           240 East Grand Avenue
                           South San Francisco, CA 94080

                           With a copy to:

                           Cooley Godward LLP
                           Five Palo Alto Square
                           Palo Alto, CA 94306
                           Attention:  Robert L. Jones, Esq.

                           If to Questcor, addressed to:

                           Questcor Pharmaceuticals, Inc.
                           26118 Research Road
                           Hayward, CA 94545


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       17.
<PAGE>

                           Latham & Watkins
                           135 Commonwealth Drive
                           Menlo Park, CA 94025
                           Attention:  Elizabeth Powers, Esq.


         11.6  AMENDMENT. No amendment, modification or supplement of any
provision of the Agreement will be valid or effective unless made in writing
and signed by an authorized representative of each party.

         11.7  WAIVER. No provision of the Agreement will be waived by any
act, omission or knowledge of a party or its agents or employees except by an
instrument in writing expressly waiving such provision and signed by a duly
authorized officer of the waiving party.

         11.8  SEVERABILITY. Whenever possible, each provision of the
Agreement will be interpreted in such manner as to be effective and valid
under applicable law, but if any provision of the Agreement is held to be
prohibited by or invalid under applicable law, such provision will be
ineffective only to the extent of such prohibition or invalidity, without
invalidating the remainder of the Agreement.

         11.9  ENTIRE AGREEMENT OF THE PARTIES. This Agreement constitutes
and contains the complete, final and exclusive understanding and agreement of
the parties and cancel and supersede any and all prior negotiations,
correspondence, understandings and agreements, whether oral or written,
between the parties respecting the subject matter thereof.

         11.10 PUBLICITY. Within five (5) days from the Effective Date, the
parties shall issue a joint press release regarding the business relationship
set forth in this Agreement, with at least one executive-level quote from
each party, and such press release shall be approved by advance by both
parties. Rigel shall approve such joint press release unless, in conjunction
with its initial public offering, it receives reasonable advice of counsel
that such press release should not be made at such time. Each party shall
have the right to identify the other party (other by listing such other
party's name and logo) as a business partner in marketing and publicity
materials and on each party's Web site. Except as otherwise specified in this
paragraph, a party shall not use the other party's name or logo except with
the prior consent of such other party.

         IN WITNESS WHEREOF, the parties hereto have duly executed this
Agreement as of the Effective Date.


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       18.
<PAGE>

QUESTCOR PHARMACEUTICALS, INC.                  RIGEL PHARMACEUTICALS, INC.

By:  /s/ Charles J. Casamento                   By:  /s/ Raul R. Rodriguez
    -----------------------------                   ----------------------------

Name:  Charles J. Casamento                     Name:  Raul R. Rodriguez
                                                      --------------------------
Title:  Chairman, President & CEO               Title:  Vice President Business
                                                        Development
                                                       -------------------------


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       19.
<PAGE>

                                       APPENDIX A

                                     QUESTCOR PATENTS

U.S. Patent No. 5,738,985

and

METHOD FOR SELECTIVE INACTIVATION OF VIRAL REPLICATION                   CANADA

Owner: RIBOGENE, INC.

         Inventors - MILES, VINCENT J.; MATHEWS, MICHAEL B.; KATZE, MICHAEL G.;
         WITHERELL, GARY W.; WATSON, JULIA C.
    Pat No:                                                     FILED WAIT EXAM
    App No: 2,159,639          APRIL 01, 1994
Basic App: PCT/US94/03623      APRIL 02, 1993
Publication No. 1: WO94/23041  OCTOBER 13, 1994
Priority Date: APRIL 02, 1993
--------------------------------------------------------------------------------


METHOD FOR SELECTIVE INACTIVATION OF VIRAL REPLICATION                    JAPAN

Owner: RIBOGENE, INC.

         Inventors - MILES, VINCENT J.; MATHEWS, MICHAEL B.; KATZE, MICHAEL G.;
         WITHERELL, GARY W.; WATSON, JULIA C.
    Pat No:                                                     FILED WAIT EXAM
    App No: 6-522423           APRIL 01, 1994
Basic App: PCT/US94/03623      APRIL 02, 1993 ()
Publication No. 1: WO94/23041  OCTOBER 13, 1994
Priority Date: APRIL 02, 1993



METHOD FOR SELECTIVE INACTIVATION OF VIRAL REPLICATION                HONG KONG

Owner: RIBOGENE, INC.

         Inventors - MILES, VINCENT J.; MATHEWS, MICHAEL B.; KATZE, MICHAEL G.;
         WITHERELL, GARY W.; WATSON, JULIA C.
    Pat No:                                                     FILED WAIT EXAM
    App No: 94912387.1     SEPTEMBER 24, 1998
Basic App: PCT/US94/03623  APRIL 01, 1994 ()
Priority Date: APRIL 01, 1994




[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       E-1.
<PAGE>


METHOD FOR SELECTIVE INACTIVATION OF VIRAL REPLICATION    EUROPEAN PATENT CONV.
                                                               J. A. KEMP & CO.
Owner: RIBOGENE, INC.                                      Agent Ref.: N.68947A

         Inventors - MILES, VINCENT J.; MATHEWS, MICHAEL B.; KATZE, MICHAEL G.;
         WITHERELL, GARY W.; WATSON, JULIA C.
    Pat No:                                                             PENDING
    App No: 94912387.1      APRIL 01, 1994
Basic App: PCT/US94/03623   APRIL 02, 1993 ()
Publication No. 1: 0693126  JANUARY 24, 1996
Priority Date: APRIL 02, 1993
--------------------------------------------------------------------------------

METHOD FOR SELECTIVE INACTIVATION OF VIRAL REPLICATION                      PCT

Owner: RIBOGENE, INC.                                  Agent Ref.: 7960-030-228

         Inventors - MILES, VINCENT J.; MATHEWS, MICHAEL B.; KATZE, MICHAEL G.;
         WITHERELL, GARY W.; WATSON, JULIA C.
    Pat No:                                                           PUBLISHED
    App No: PCT/US94/03623     APRIL 01, 1994
Basic App: PCT/US94/03623      APRIL 02, 1993 ()
Publication No. 1: WO94/23041  OCTOBER 13, 1994
Priority Date: APRIL 02, 1993

                                                               Archive:  13,419


METHOD FOR SELECTIVE INACTIVATION OF VIRAL REPLICATION            UNITED STATES

Owner: RIBOGENE, INC.

         Inventors - MILES, VINCENT J.; MATHEWS, MICHAEL B.; KATZE, MICHAEL G.
    Pat No: 5,738,985  APRIL 14, 1998   Expires: APRIL 14, 2015        PATENTED
    App No: 08/221,816 APRIL 01, 1994


Priority Date: APRIL 02, 1993

                                                               Archive:  14,052
--------------------------------------------------------------------------------


METHOD FOR SELECTIVE INACTIVATION OF VIRAL REPLICATION            UNITED STATES

         Inventors - MILES, VINCENT J.; MATTHEWS, MICHAEL B.; KATZE, MICHAEL G.;
         WITHERELL, GARY W.; WATSON, JULIA C.
    Pat No:                                                             ALLOWED
    App No: 08/925,156     SEPTEMBER 08, 1997
    Continuation of App No 08/221,816 now Pat No 5,738,985

Priority Date: APRIL 01, 1994
--------------------------------------------------------------------------------


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       E-2.
<PAGE>

NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY              CANADA
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 2,283,379          MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997
--------------------------------------------------------------------------------



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY           AUSTRALIA
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                             PENDING
    App No: 66840/98           MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997
--------------------------------------------------------------------------------



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY         NEW ZEALAND
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 337703             MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY              MEXICO
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 998116             MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997
--------------------------------------------------------------------------------


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       E-3.
<PAGE>

NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY               JAPAN
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 10-538754          MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997
--------------------------------------------------------------------------------



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY              NORWAY
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 19994295           MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT              RUSSIAN FEDERATION
SELECTIVELY INHIBIT HEPATITIS C VIRUS REPLICATION.
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 99120790           MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY             HUNGARY
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                    Expires:     MARCH 05, 2018      FILED WAIT EXAM
    App No: P0001395        MARCH 05, 1998
Basic App: PCT/US98/04226   MARCH 05, 1997 ()

Priority Date: MARCH 05, 1997


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       E-4.
<PAGE>

NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY              TURKEY
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                    Expires:     MARCH 05, 2018      FILED WAIT EXAM
    App No: 1999/02561         MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997


NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY               CHINA
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                             PENDING
    App No: 98804841.8         MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY      CZECH REPUBLIC
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: PV3149-99          MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY              POLAND
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: P335721            MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       E-5.
<PAGE>

NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY              ISRAEL
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 131730             MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997

NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY              TAIWAN
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 87103232        MARCH 05, 1998


Priority Date: MARCH 05, 1997
--------------------------------------------------------------------------------



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY       KOREA (SOUTH)
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 7008068/99         MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT           EUROPEAN PATENT CONV.
SELECTIVELY INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                     FILED WAIT EXAM
    App No: 98908928.9         MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       E-6.
<PAGE>

NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY                 PCT
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: RIBOGENE, INC.

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                           COMPLETED
    App No: PCT/US98/04226     MARCH 05, 1998
Basic App: PCT/US98/04226      MARCH 05, 1997 ()
Publication No. 1: WO98/39487  SEPTEMBER 11, 1998
Priority Date: MARCH 05, 1997
--------------------------------------------------------------------------------



[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       E-7.
<PAGE>

                                 APPENDIX B

                             WASHINGTON PATENTS


Pending U.S. Patent Application  U.S.S.N. 60/027,982

and

NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY        UNITED STATES
INHIBIT HEPATITIS C VIRUS REPLICATION
Owner: UNIVERSITY OF WASHINGTON

         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No: 6,030,785      FEBRUARY 29, 2000                            PATENTED
    App No: 09/035,619     MARCH 05, 1998


Priority Date: MARCH 05, 1997



NOVEL SCREENING METHODS TO IDENTIFY AGENTS THAT SELECTIVELY        UNITED STATES
INHIBIT HEPATITIS C VIRUS REPLICATION
         Inventors -  KATZE, MICHAEL G.; GALE, JR., MICHAEL J.
    Pat No:                                                              PENDING
    App No: 09/514,006      FEBRUARY 25, 2000
    Continuation of App No 09/035,619 now Pat No 6,030,785

Priority Date: MARCH 05, 1998



[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                       E-1.