TENDER AND SHAREHOLDER SUPPORT AGREEMENT

Exhibit 4.1

TENDER AND SHAREHOLDER SUPPORT AGREEMENT

          This TENDER AND SHAREHOLDER SUPPORT AGREEMENT (this “ Agreement ”), dated October ___, 2008, is by and among SmithKline Beecham Corporation, a Pennsylvania corporation (“ Parent ”), Gemstone Acquisition Corporation, a California corporation and wholly-owned Subsidiary of Parent (“ Purchaser ”), and certain shareholders of Genelabs Technologies, Inc., a California corporation (the “ Company ”), set forth on Schedule A hereto (each a “ Shareholder ” and, collectively the “ Shareholders ”).

          WHEREAS, Parent, Purchaser and the Company propose to enter into an Agreement and Plan of Merger, dated as of the date hereof (the “ Merger Agreement ”), which provides, among other things, for Purchaser to commence a tender offer for all of the issued and outstanding shares of Common Stock (as defined below) of the Company (the “ Offer ”) and the merger of Purchaser with and into the Company, with the Company continuing as the surviving corporation (the “ Merger ”), upon the terms and subject to the conditions set forth in the Merger Agreement (capitalized terms used herein without definition shall have the respective meanings specified in the Merger Agreement);

          WHEREAS, each Shareholder beneficially owns the number of shares of common stock, no par value, of the Company (the “ Common Stock ”) set forth opposite the name of such Shareholder on Schedule A hereto (such shares of Common Stock, together with any other shares of capital stock of the Company as to which such Shareholder acquires beneficial ownership after the date hereof and prior to the earlier of the Effective Time and the termination of all of the Shareholder’s obligations under this Agreement, including any shares of Common Stock acquired by means of purchase, dividend or distribution, or issued upon the exercise of any warrants or options, or the conversion of any convertible securities or otherwise, being collectively referred to herein as the “ Covered Shares ”); and

          WHEREAS, as a condition to the willingness of Parent and Purchaser to enter into the Merger Agreement and as an inducement and in consideration therefor, the Shareholders have agreed to enter into this Agreement;

          NOW, THEREFORE, in consideration of the foregoing and the mutual covenants and agreements set forth herein and in the Merger Agreement, and intending to be legally bound hereby, the parties hereto agree as follows:

          SECTION 1. Representations and Warranties of the Shareholders . Each Shareholder hereby represents and warrants to Parent and Purchaser, severally and not jointly, and solely as to itself and its Covered Shares, as follows:

               (a) The Shareholder (i) is the beneficial owner (as defined in Rule 13d-3 under the Securities Exchange Act of 1934, as amended) of, and has good and marketable title to, the Covered Shares set forth opposite such Shareholder’s name on Schedule A hereto, free and clear of any and all liens, claims, security interests, proxies, voting trusts or agreements, options, rights, understandings or arrangements or any other encumbrances whatsoever on title, transfer, or exercise of any rights of a Shareholder in respect of such Covered Shares (collectively, “ Encumbrances ”) except for restrictions on transfer under the Securities Act of 1933, as amended, or Encumbrances arising hereunder; (ii) does not own, of record or beneficially, any shares of capital stock of the Company (or rights to acquire any such shares) other than the Covered Shares set forth on Schedule A hereto; and (iii) has the right to vote and dispose of and holds power to issue instructions with respect to the matters set forth in Sections 3, 4, 5 and 6 hereof, power to demand appraisal rights and power to agree to all of the matters set forth in this Agreement with respect to all of such Shareholder’s Covered Shares, with no material limitations, qualifications or restrictions on such rights, subject to applicable federal securities law and the terms of this Agreement.

               (b) In the case of any Shareholder that is a corporation, limited partnership or limited liability company, such Shareholder is an entity duly organized, validly existing and in good standing under the laws of the jurisdiction in which it is incorporated or constituted.

               (c) The Shareholder has the legal capacity and all requisite power and authority to execute and deliver this Agreement and to perform the Shareholder’s obligations hereunder and consummate the transactions contemplated hereby. To the extent applicable, the execution, delivery and performance by the Shareholder of this Agreement and the consummation by the Shareholder of the transactions contemplated hereby have been duly and validly authorized by the Shareholder (or its board of directors or similar governing body, as applicable), and no other actions or proceedings on the part of the Shareholder are necessary to authorize the execution and delivery by the Shareholder of this Agreement and the consummation by the Shareholder of the transactions contemplated hereby. This Agreement has been duly and validly executed and delivered by the Shareholder and constitutes a valid and binding obligation of the Shareholder enforceable in accordance with its terms, subject to the effects of bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and other similar laws relating to or affecting creditors’ rights generally and general equitable principles (whether considered in a proceeding in equity or at law).

               (d) Neither the execution and delivery of this Agreement by the Shareholder, the performance by the Shareholder of such Shareholder’s obligations hereunder nor the consummation by the Shareholder of the transactions contemplated hereby will (i) result in a violation or breach of, or constitute (with or without notice or lapse of time or both) a default under, or conflict with (A) to the extent applicable, any provisions of the organizational documents of the Shareholder or (B) any note, bond, mortgage, indenture, contract, agreement, lease, license, permit or other instrument or obligation of any kind to which such Shareholder is a party or by which such Shareholder’s Covered Shares are bound, except with respect to clause (B) for any such violations, breaches, defaults or conflicts as could not reasonably be expected, either individually or in the aggregate, to materially impair the ability of such Shareholder to perform his or its obligations hereunder or to consummate the transactions contemplated hereby on a timely basis, or (ii) violate, or require any consent, approval, or notice under, any provision of any judgment, order or decree or any federal, state, local or foreign statute, law, ordinance, rule, regulation, order, judgment, decree or legal requirement applicable to such Shareholder or any of such Shareholder’s Covered Shares (other than filings required pursuant to the Securities Exchange Act of 1934, as amended, and the rules promulgated thereunder).

          SECTION 2. Representations and Warranties of Parent and Purchaser . Each of Parent and Purchaser hereby, jointly and severally, represents and warrants to the Shareholders as follows:

               (a) Each of Parent and Purchaser is a corporation duly organized, validly existing and in good standing under the laws of the jurisdiction in which it is incorporated, and each of Parent and Purchaser has all requisite corporate power and corporate authority to execute and deliver this Agreement and to perform its obligations hereunder and consummate the transactions contemplated hereby, and has taken all necessary corporate action to authorize the execution, delivery and performance of this Agreement.

               (b) This Agreement has been duly authorized, executed and delivered by each of Parent and Purchaser and constitutes a valid and binding obligation of Parent and Purchaser enforceable in accordance with its terms, subject to the effects of bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and other similar laws relating to or affecting creditors’ rights generally and general equitable principles (whether considered in a proceeding in equity or at law).

               (c) Neither the execution and delivery of this Agreement by Parent and Purchaser, the performance by Parent and Purchaser of their obligations hereunder nor the consummation by Parent and Purchaser of the transactions contemplated hereby will (i) result in a violation or breach of, or constitute (with or without notice or lapse of time or both) a default under, or conflict with (A) any provisions of the organizational documents of Parent or Purchaser or (B) any note, bond, mortgage, indenture, contract, agreement, lease, license, permit or other instrument or obligation of any kind to which such Parent or Purchaser is a party or by which Parent or Purchaser or their assets are bound, except with respect to clause (B) for any such violations, breaches, defaults or conflicts as could not reasonably be expected, either individually or in the aggregate, to materially impair the ability of Parent or Purchaser to perform its obligations hereunder or to consummate the transactions contemplated hereby on a timely basis, or (ii) violate, or require any consent, approval, or notice under, any provision of any judgment, order or decree or any federal, state, local or foreign statute, law, ordinance, rule, regulation, order, judgment, decree or legal requirement applicable to Parent or Purchaser or their assets (other than filings required pursuant to Securities Exchange Act of 1934, as amended, and the rules promulgated thereunder).

          SECTION 3. Tender of the Covered Shares . Unless this Agreement shall have been terminated in accordance with its terms, and subject to Section 5, each Shareholder hereby agrees that it shall (i) tender its Covered Shares or cause to be tendered (and deliver any certificates evidencing such Covered Shares or an appropriate affidavit of lost certificate with respect thereto to the extent any of such certificates have been lost, misplaced or destroyed), into the Offer promptly following the date the Offer is commenced, and in any event no later than five (5) Business Days prior to the Initial Expiration Date of the Offer, free and clear of all Encumbrances and (ii) not withdraw or cause to be withdrawn, its Covered Shares from the Offer at any time. If a Shareholder acquires Covered Shares after the date hereof, unless this Agreement shall have been terminated in accordance with its terms, such Shareholder shall (A) tender, or cause to be tendered, such Covered Shares into the Offer on or before the fifth (5 ^th ) Business Day prior to the Initial Expiration Date or, if later, on or before the second (2 ^nd ) Business Day after such acquisition but in any event prior to the Expiration Date, and (B) not withdraw, or cause to be withdrawn, such Covered Shares from the Offer at any time.

          SECTION 4. Option .

               (a) On the terms and subject to the conditions set forth herein, each Shareholder hereby grants to Parent an irrevocable option (the “ Option ”) to purchase all of the right, title and interest of such Shareholder in and to such Shareholder’s Covered Shares at a

price equal to the Offer Price. Parent may exercise an Option in whole, but not in part, if, but only if, (i) Purchaser has acquired shares of Common Stock pursuant to the Offer and (ii) such Shareholder shall have failed to tender into the Offer any Covered Shares or shall have withdrawn the tender of any Covered Shares into the Offer. Parent may exercise an Option at any time within the sixty (60) days following the date when such Option first becomes exercisable.

               (b) In the event that Parent is entitled to and wishes to exercise an Option, Parent shall send a written notice to the relevant Shareholder(s) specifying the place and the date for the closing of such purchase, which date shall be not more than sixty (60) days after the date of such notice; provided that in the event that p