Underwriting Agreement

“ Applicable Time ” means 8:15 A.M. (Eastern time) on the date of this Agreement.

“ Closing Date ” has the meaning defined in Section 3 hereof.

“ Commission ” means the Securities and Exchange Commission.

“ Effective Time ” of a Registration Statement relating to the Offered Securities means the time of the first contract of sale for the Offered Securities.

“ Exchange Act ” means the Securities Exchange Act of 1934, as amended.

“ Final Prospectus ” means the Statutory Prospectus that discloses the public offering price, other 430B Information and other final terms of the Offered Securities and otherwise satisfies Section 10(a) of the Act.

“ General Use Issuer Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is intended for general distribution to prospective investors, as evidenced by its being so specified in Schedule B to this Agreement.

“ Issuer Free Writing Prospectus ” means any “issuer free writing prospectus,” as defined in Rule 433, relating to the Offered Securities in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained in the Company’s records pursuant to Rule 433(g).

“ Limited Use Issuer Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is not a General Use Issuer Free Writing Prospectus.

“ Rules and Regulations ” means the rules and regulations of the Commission.

“ Securities Laws ” means, collectively, the Sarbanes-Oxley Act of 2002 (“ Sarbanes-Oxley ”), the Act, the Exchange Act, the Rules and Regulations, the auditing principles, rules, standards and practices applicable to auditors of “issuers” (as defined in Sarbanes-Oxley) promulgated or approved by the Public Company Accounting Oversight Board and, as applicable, the rules of the NASDAQ Stock Market (the “ NASDAQ Rules ”).

“ Statutory Prospectus ” with reference to any particular time means the prospectus relating to the Offered Securities that is included in a Registration Statement immediately prior to that time, including all 430B Information and all 430C Information with respect to the Registration Statement.  For purposes of the foregoing definition, 430B Information shall be considered to be included in the Statutory Prospectus only as of the actual time that form of prospectus (including a prospectus supplement) is filed with the Commission pursuant to Rule 424(b) and not retroactively.

(ii)  (A) As to each Registration Statement (1) at the time the Registration Statement initially became effective, (2) at the time of each amendment thereto for the purposes of complying with Section 10(a)(3) of the Act (whether by post-effective amendment, incorporated report or form of prospectus), (3) at the Effective Time relating to the Offered Securities and (4) on the Closing Date, the Registration Statement conformed and will conform in all respects to the requirements of the Act and the Rules and Regulations and did not and will not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading and (B) (1) on its date, (2) at the time of filing the Final Prospectus pursuant to Rule 424(b) and (3) on the Closing Date, the Final Prospectus will conform in all respects to the requirements of the Act and the Rules and Regulations, and will not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading.  The preceding sentence does not apply to statements in, or omissions from, any such document in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representative specifically for use therein, it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 7(b) hereof.

(iii)  (A) The date of this Agreement is not more than three years subsequent to the initial effective date of the Initial Registration Statement.  If, immediately prior to the third anniversary of the initial effective date of the Initial Registration Statement, any of the Offered Securities remain unsold by the Underwriters,

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the Company will prior to that third anniversary file, if it has not already done so, a new shelf registration statement relating to the Offered Securities, in a form satisfactory to the Representative, will use its best efforts to cause such registration statement to be declared effective within 180 days after that third anniversary, and will take all other action necessary or appropriate to permit the public offering and sale of the Offered Securities to continue as contemplated in the expired registration statement relating to the Offered Securities.  References herein to the Registration Statements shall include such new shelf registration statement.

(iv)  (A)  At the earliest time after the filing of each Registration Statement that the Company or another offering participant made a bona fide offer (within the meaning of Rule 164(h)(2)) of the Offered Securities and (B) at the date of this Agreement, the Company was not and is not an “ineligible issuer,” as defined in Rule 405, including (x) the Company or any other subsidiary in the preceding three years not having been convicted of a felony or misdemeanor or having been made the subject of a judicial or administrative decree or order as described in Rule 405 and (y) the Company in the preceding three years not having been the subject of a bankruptcy petition or insolvency or similar proceeding, not having had a registration statement be the subject of a proceeding under Section 8 of the Act and not being the subject of a proceeding under Section 8A of the Act in connection with the offering of the Securities, all as described in Rule 405.

(v)  As of the Applicable Time, neither (A) the General Use Issuer Free Writing Prospectus(es) issued at or prior to the Applicable Time and, the preliminary prospectus supplement, dated September 16, 2009, including the base prospectus, dated April 30, 2009 (which is the most recent Statutory Prospectus distributed to investors generally), and the other information, if any, stated in Schedule B to this Agreement, all considered together (collectively, the “ General Disclosure Package ”), nor (B) any individual Limited Use Issuer Free Writing Prospectus, when considered together with the General Disclosure Package, included any untrue statement of a material fact or omitted to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.  The preceding sentence does not apply to statements in, or omissions from, any Statutory Prospectus or any Issuer Free Writing Prospectus in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representative specifically for use therein, it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 7(b) hereof.

(vi)  Each Issuer Free Writing Prospectus, as of its issue date and at all subsequent times through the completion of the public offer and sale of the Offered Securities or until any earlier date that the Company notified or notifies the Representative as described in the next sentence, did not, does not and will not include any information that conflicted, conflicts or will conflict with the information then contained in a Registration Statement.  If at any time following issuance of an Issuer Free Writing Prospectus there occurred or occurs an event or development as a result of which such Issuer Free Writing Prospectus conflicted or would conflict with the information then contained in a Registration Statement or as a result of which such Issuer Free Writing Prospectus, if republished immediately following such event or development, would include an untrue statement of a material fact or omitted or would omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading, (A) the Company has promptly notified or will promptly notify the Representative and (B) the Company has promptly amended or will promptly amend or supplement such Issuer Free Writing Prospectus to eliminate or correct such conflict, untrue statement or omission.  The preceding two sentences do not apply to statements in, or omissions from, any such document in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representative specifically for use therein, it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 7(b) hereof.

(vii)  The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Delaware, with power and authority (corporate and other) to own its properties and conduct its business as described in the General Disclosure Package; and the Company is duly qualified to do

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business as a foreign corporation in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification except for such jurisdictions where the failure to so qualify or be in good standing would not, individually or in the aggregate, have a material adverse effect on the condition (financial or other), business, prospects, properties or results of operations of the Company (“ Material Adverse Effect ”).

(viii)  The Company does not have any subsidiaries (as such term is defined in Rule 405 under the Act) other than Rigel Pharmaceuticals Limited, a private limited company registered in England and Wales, which has no assets, liabilities, operations, contracts or employees.

(ix)  The Offered Securities and all other outstanding shares of capital stock of the Company have been duly authorized; all outstanding shares of capital stock of the Company are, and when the Offered Securities have been delivered and paid for in accordance with this Agreement on the Closing Date, such Offered Securities will have been, validly issued, fully paid and nonassessable; and all outstanding shares of capital stock of the Company, and the Offered Securities will, conform to the description thereof contained in the General Disclosure Package under the heading “Description of Capital Stock”; and the stockholders of the Company have no preemptive or similar rights with respect to the Securities that have not been properly waived.

(x)  Except as disclosed in the General Disclosure Package, there are no contracts, agreements or understandings between the Company and any person that would give rise to a valid claim against the Company or any Underwriter for a brokerage commission, finder’s fee or other like payment in connection with this offering.

(xi)  Except as disclosed in the General Disclosure Package, there are no contracts, agreements or understandings between the Company and any person granting such person the right to require the Company to file a registration statement under the Act with respect to any securities of the Company owned or to be owned by such person or to require the Company to include such securities in the securities registered pursuant to any Registration Statement or in any securities being registered pursuant to any other registration statement filed by the Company under the Act.  There are no contracts, agreements or understandings between the Company and any person granting such person the right to include any securities of the Company owned or to be owned by such person in the securities registered pursuant to the Registration Statements except such rights that have been properly waived or satisfied prior to the date hereof.

(xii)  The Offered Securities are approved for listing on the NASDAQ Global Market.

(xiii)  No consent, approval, authorization, or order of, or filing with, any governmental agency or body or any court is required to be obtained or made by the Company for the consummation of the transactions contemplated by this Agreement in connection with the sale of the Offered Securities, except such as have been obtained and made under the Act and such as may be required under state securities laws.

(xiv)  The execution, delivery and performance of this Agreement by the Company, and the consummation by the Company of the transactions herein contemplated will not result in a breach or violation of any of the terms and provisions of, or constitute a default under, any statute, any rule, regulation or order of any governmental agency or body or any court, domestic or foreign, having jurisdiction over the Company or any of its properties, or any agreement or instrument to which the Company is a party or by which the Company is bound or to which any of the properties of the Company is subject, or the charter or by-laws of the Company.

(xv)  The Company has all requisite corporate power and authority to execute, deliver and perform its obligations under this Agreement.  This Agreement has been duly authorized, executed and delivered by the Company.

(xvi)  Except as disclosed in the General Disclosure Package, the Company has good and marketable title to all real properties and all other properties and assets owned by it, in each case free from liens,

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encumbrances and defects that would materially affect the value thereof or materially interfere with the use made or to be made thereof by it; and except as disclosed in the General Disclosure Package, the Company holds any leased real or personal property under valid and enforceable leases with no exceptions that would materially interfere with the use made or to be made thereof by it.

(xvii)  The Company possesses adequate certificates, authorities or permits issued by appropriate governmental agencies or bodies necessary to conduct the business now operated by it as described in the General Disclosure Package except where the lack thereof would not have a Material Adverse Effect, including without limitation all such certificates, authorities or permits required by the United States Food and Drug Administration (“ FDA ”) or any other federal, state or foreign agencies or bodies engaged in the regulation of pharmaceuticals or biohazardous materials, and has not received any notice of proceedings relating to the revocation or modification of any such certificate, authority or permit that, if determined adversely to the Company, would individually or in the aggregate have a Material Adverse Effect or could reasonably be expected to have a Material Adverse Effect.

(xviii)  No labor dispute with the employees of the Company exists or, to the knowledge of the Company, is imminent that could reasonably be expected to have a Material Adverse Effect.

(xix)  The Company owns, possesses or can acquire on reasonable terms, adequate trademarks, trade names and other rights to inventions, know-how, patents, copyrights, confidential information and other intellectual property (collectively, “ intellectual property rights ”) necessary to conduct the business now operated by it, or presently employed by it, and has not received any notice of infringement of or conflict with asserted rights of others with respect to any intellectual property rights that, if determined adversely to the Company, would individually or in the aggregate have a Material Adverse Effect.  The expiration of any of the Company’s owned or licensed intellectual property rights upon their respective natural terms would not result in a Material Adverse Effect.  There is no claim being made against the Company regarding intellectual property rights.  The Company does not in the conduct of its business, as now conducted or proposed to be conducted as described in the General Disclosure Package, infringe or conflict with any intellectual property rights of a third party or any intellectual property rights which are the subject of any patent application filed by any third party, which infringement or conflict could reasonably be expected to result in a Material Adverse Effect.  The Company is not aware of any prior art that may render any patent application owned by the Company unpatentable which has not been disclosed to the United States Patent and Trademark Office and which would reasonably be expected to have a Material Adverse Effect.

(xx)  The Company (A) is not in violation of any statute or any rule, regulation, decision or order of any governmental agency or body or any court, domestic or foreign, relating to the use, disposal or release of hazardous or toxic substances or relating to the protection or restoration of the environment or human exposure to hazardous or toxic substances (collectively, “ environmental laws ”), (B) does not own or operate any real property contaminated with any substance that is subject to any environmental laws, (C) is not liable for any off-site disposal or contamination pursuant to any environmental laws, or (D) is not subject to any claim relating to any environmental laws, which violation, contamination, liability or claim would individually or in the aggregate have a Material Adverse Effect; and the Company is not aware of any pending investigation which might lead to such a violation, liability or claim or uncover such contamination.

(xxi)  Except as disclosed in the General Disclosure Package, there are no pending actions, suits, inquiries, investigations or proceedings against the Company or any of its properties that, if determined adversely to the Company, would individually or in the aggregate have a Material Adverse Effect, or would materially and adversely affect the ability of the Company to perform its obligations under this Agreement, or which are otherwise material in the context of the sale of the Offered Securities; and no such actions, suits, inquiries, investigations or proceedings have been threatened or, to the Company’s knowledge, contemplated.

(xxii) The financial statements included in the Registration Statements and the General Disclosure Package present fairly the financial position of the Company as of the dates shown and their results of operations and cash flows for the periods shown, and such financial statements have been prepared in conformity with the generally accepted accounting principles in the United States applied on a consistent basis and the schedules included in the Registration Statements and General Disclosure Package present fairly the information required to be stated therein.

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(xxiii)  Except as disclosed in the General Disclosure Package, since the date of the latest audited financial statements included in the General Disclosure Package there has been no material adverse change, nor any development or event involving a prospective material adverse change, in the condition (financial or other), business, properties or results of operations of the Company and, except as disclosed in or contemplated by the General Disclosure Package, there has been no dividend or distribution of any kind declared, paid or made by the Company on any class of its capital stock.

(xxiv)  The Company is subject to the reporting requirements of either Section 13 or Section 15(d) of the Securities Exchange Act of 1934 and files reports with the Commission on the Electronic Data Gathering, Analysis, and Retrieval (EDGAR) system.

(xxv)  The Company is not and, after giving effect to the offering and sale of the Offered Securities by the Company and the application of the proceeds thereof as described in the General Disclosure Package, will not be an “investment company” as defined in the Investment Company Act of 1940.

(xxvi)  The Company and the Company’s Board of Directors (the “ Board ”) are in compliance in all material respects with Sarbanes-Oxley and all applicable NASDAQ Rules.  The Company maintains a system of internal accounting controls sufficient to provide reasonable assurances that:  (A) transactions are executed in accordance with management’s general or specific authorization; (B) transactions are recorded as necessary to permit preparation of financial statements in conformity with GAAP and to maintain accountability for assets; (C) access to assets is permitted only in accordance with management’s general or specific authorization; and (D) the recorded accountability for assets is compared with existing assets at reasonable intervals and appropriate action is taken with respect to any differences.  The Company’s system of internal accounting controls are overseen by the Audit Committee (the “ Audit Committee” ) of the Board.  The Company has not publicly disclosed or reported to the Audit Committee or the Board, and within the next 90 days the Company does not as of the date hereof reasonably expect to publicly disclose or report to the Audit Committee or the Board, a significant deficiency, a material weakness, a material change in its system of internal accounting controls or fraud involving management or other employees who have a significant role in its system of internal accounting controls, any material violation of, or failure to comply with, the Securities Laws, or, except to the extent disclosed in the General Disclosure Package, any other matter which, if determined adversely, would have a Material Adverse Effect.

(xxvii)  Each Investigational New Drug (“ IND ”) application to the FDA or similar application to foreign regulatory bodies, and related documents and information, has been filed, approved and maintained in compliance in all material respects with applicable statutes, rules, regulations, standards, guides or order administered or promulgated by the FDA or other regulatory body, and all pre-clinical and clinical studies undertaken to support approval of products for commercialization have been conducted in compliance with all applicable current Good Laboratory Practices and Good Clinical Practices in all material respects.  No filing or submission to the FDA or any other regulatory body, that is intended to be the basis for any approval, contains any material omission or material false information.  Except to the extent disclosed in the General Disclosure Package, the Company has operated and currently is in compliance in all material respects with all applicable rules, regulations and policies of the FDA and comparable drug regulatory agencies outside of the United States.

(xxviii)  The clinical trials conducted by or on behalf of the Company that are described in the General Disclosure Package, or the results of which are referred to in the General Disclosure Package, if any, are the only clinical trials currently being conducted by or on behalf of the Company, and, to the best of the Company’s knowledge, such studies and tests were and, if still pending, are being, conducted in accordance with experimental protocols, procedures and controls pursuant to accepted professional scientific standards; and the descriptions of the results of the studies, tests and trials contained in the General Disclosure Package are accurate and complete in all material respects and fairly present the data derived from such studies and tests.  Except as described in the General Disclosure Package, the Company

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has no knowledge of any other studies or test, the results of which are inconsistent with or otherwise call into question the results of the clinical trials described in the General Disclosure Package.  The Company has not received any notices or correspondence from the FDA or any other governmental agency requiring the termination, suspension or modification of any clinical trials conducted by, or on behalf of, the Company or in which the Company has participated that are described in the General Disclosure Package.

(xxix)  As of the date of filing of each Registration Statement, including the date of any amendment thereto, and as of the date hereof, the Company satisfied and satisfies the registrant eligibility requirements for registration statement Form S-3 pursuant to the standards for such form prior to October 21, 1992.  The aggregate market value of voting stock held by non-affiliates of the Company is $100 million or more and the Company has an annual trading volume for its Securities of 3 million shares or more, as determined pursuant to the instructions set forth in the registration statement on Form S-3 prior to October 21, 1992.

(xxx)  The statements in the General Disclosure Package and the Final Prospectus under the heading “Description of Capital Stock,” insofar as such statements summarize legal matters, agreements, documents or proceedings discussed therein, are accurate and fair summaries of such legal matters, agreements, documents or proceedings and present the information required to be shown.

(xxxi)  The Company has not taken and will not take, directly or indirectly, any action designed to or that has constituted or that could reasonably be expected to cause or result in the stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

3.  Purchase, Sale and Delivery of