WARRANT FOR THE PURCHASE OF SHARES

Exhibit 10.23

THIS WARRANT AND THE SECURITIES ISSUABLE UPON THE EXERCISE HEREOF HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”) OR ANY STATE SECURITIES LAWS. THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED, HYPOTHECATED OR OTHERWISE TRANSFERRED IN THE ABSENCE OF A REGISTRATION STATEMENT IN EFFECT WITH RESPECT TO THE SECURITIES UNDER SUCH ACT OR AN EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF SUCH ACT.

Void after the Tenth Anniversary hereof

WARRANT FOR THE
PURCHASE OF SHARES OF COMMON STOCK

of

THERAPEUTIC GENOMICS, INC.

(Incorporated under the laws of the State of Delaware)

     THIS CERTIFIES THAT, for value received, Alexandria Real Estate Equities, L.P., a Delaware limited partnership, together with its successors and assigns (each, a “holder”), is entitled to purchase Fifteen Thousand (15,000) duly authorized validly issued, fully paid and nonassessable shares of Common Stock, no par value per share, (the “Common Stock”) of Therapeutic Genomics, Inc., a Delaware corporation (the “Company”), at the per share purchase price described in Section 1.3 below, subject to the provisions and upon the terms and conditions hereinafter set forth.

     1.  Exercise of Warrant . The terms and conditions upon which this Warrant may be exercised and the Common Stock covered hereby (the “Warrant Stock”) may be purchased are as follows:

          1.1 Term . The purchase right represented by this Warrant may be exercised in whole or in part at any time and from time to time from and after the date hereof and on or before the tenth anniversary hereof; provided , that if the last day on which this Warrant may be exercised is not a Business Day (as defined in Section 12 hereof), this Warrant may be exercised prior to 5:00 p.m. (New York time) on the next succeeding full Business Day with the same force and effect as if exercised on such last day specified herein.

          1.2 Number of Shares . This Warrant is initially exercisable for Fifteen Thousand (15,000) shares of Common Stock, subject to adjustment pursuant to Section 2 of this Warrant.

          1.3 Purchase Price . The initial per share purchase price for the shares of Common Stock to be issued upon exercise of this Warrant shall be $2.00, subject to adjustment pursuant to Section 2 of this Warrant (the “Warrant Price”).

          1.4 Method of Exercise . The exercise of the purchase rights evidenced by this Warrant shall be effected by (a) the surrender of this Warrant, together with a duly executed copy of the form of subscription attached hereto, to the Company at its principal offices and (b) the delivery of the purchase price (i) by check or bank draft payable to the Company’s order or by wire transfer to the Company’s account for the number of shares for which the purchase rights hereunder are being exercised or any other form of consideration approved by the Company’s Board of Directors or (ii) pursuant to the procedure set forth in Section 1.5.

          Each exercise of this Warrant shall be deemed to have been effected immediately prior to the close of business on the day on which this Warrant shall have been surrendered to the Company as provided herein or at such later date as may be specified in the executed form of subscription, and at such time the person or persons in whose name or names any certificate or certificates for shares of Common Stock shall be issuable upon such exercise as provided herein shall be deemed to have become the holder or holders of record thereof.

          1.5 Cashless Exercise. In addition to and without limiting the rights of the holder hereof under the terms hereof, at the holder’s option this Warrant may be exercised in whole or in part at any time or from time to time prior to its expiration for a number of shares of Common Stock having an aggregate fair market value on the date of such exercise equal to the difference between (a) the fair market value of the number of shares of Warrant Stock designated for exercise by the holder hereof on the date of exercise and (b) the aggregate Warrant Price for such shares in effect at such time.

     The “fair market value” of shares of Common Stock shall, for all purposes under this Warrant, be calculated on the basis of (a) if the Common Stock is then traded on a securities exchange, the average of the closing prices of the Common Stock on such exchange over the twenty (20) trading day period ending three (3) trading days prior to the date of exercise, (b) if the Common Stock is then regularly traded over-the-counter, the average of the sale prices or, if sale prices for the Common Stock are not regularly and publicly reported, the closing bid of the Common Stock over the twenty (20) trading day period ending three (3) trading days prior to the date of exercise, or (c) if there is no active public market for the Common Stock, the fair market value thereof shall be determined in good faith by the Company’s Board of Directors; provided , that if the holder disputes such a determination by the Company’s Board of Directors, then such value may be determined by a nationally recognized investment banking firm, mutually acceptable

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to the Company and the holder, with the costs of such valuation being borne by the holder. If the holder of this Warrant exercises this Warrant contingent upon the closing of a public offering, the “fair market value” of a share of Common Stock on the date of exercise shall be equal to the initial price to the public specified in the final prospectus with respect to such public offering. The following illustrates how many shares would be issued upon exercise of this Warrant pursuant to this Section 1.5:

No payment of any cash or other consideration to the Company shall be required from the holder of this Warrant in connection with any exercise of this Warrant pursuant to this Section 1.5. Such exercise shall be effective upon the date of receipt by the Company of this Warrant surrendered for cancellation and a written request from the holder hereof that the exercise pursuant to this section be made, or at such later date as may be specified in such request.

          1.6 Issuance of Shares . As soon as reasonably practicable after each exercise of this Warrant, in whole or in part, the Company at its expense (including the payment by it of any applicable issue taxes) shall cause to be issued in the name of and delivered to the holder hereof or as such holder (upon payment by such holder of any applicable transfer taxes) may direct, (a) a certificate or certificates for the number of duly authorized, validly issued, fully paid and nonassessable shares of Common Stock to which such holder shall be entitled upon such exercise, and (b) in case such exercise is in part only, a new Warrant or Warrants of like tenor, representing in the aggregate the right to purchase the number of shares of Common Stock equal (without giving effect to any adjustment thereof provided for in Section 2) to the number of such shares stated in this Warrant minus the number of such shares designated by the holder upon such exercise as provided herein.

     2.  Certain Adjustments .

          2.1 Mergers. Consolidations or Sale of Assets . If after the date hereof there shall be a capital reorganization (other than a combination or subdivision of Common Stock otherwise provided for herein), or spin-off, or a merger or consolidation of the Company with or into another corporation, a limited liability company, a partnership or any other legal entity (each

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of the foregoing being referred to herein as a “Person”), or the sale of all or substantially all of the Company’s properties and assets to any other Person, then, as a part of such transaction, lawful provision shall be made so that the holder shall thereafter be entitled to receive upon exercise of this Warrant, during the period specified in this Warrant and upon payment of the purchase price required by this Warrant, the number of shares of stock or other securities, cash or property of the Company or the successor corporation or other Person resulting from such transaction, to which a holder of the Common Stock deliverable upon exercise of this Warrant would have been entitled under the provisions of the agreement in such transaction (or otherwise pursuant to such transaction) if this Warrant had been exercised immediately before such transaction. In any such case, appropriate adjustment (as determined reasonably and in good faith by the Company’s Board of Directors) shall be made in the application of the provisions of this Warrant with respect to the rights and interests of the holder after such transaction to the end that the provisions of this Warrant (including adjustment of the Warrant Price then in effect and the number of shares of Common Stock issuable upon exercise hereof) shall be applicable after the transaction, as near as reasonably may be, in relation to any shares or other property deliverable after the transaction upon exercise of this Warrant.

          2.2 Splits and Subdivisions; Dividends . If the Company should effect or fix a record date for the effectuation of a split or subdivision of the outstanding shares of Common Stock or the determination of the holders of Common Stock entitled to receive a dividend or other distribution payable in additional shares of Common Stock or other securities or warrants, options or other rights convertible into, or entitling the holder thereof to receive directly or indirectly, additional shares of Common Stock (hereinafter referred to as “Common Stock Equivalents”) without payment of any consideration by such holder for the additional shares of Common Stock or Common Stock Equivalents (including the additional shares of Common Stock issuable upon conversion or exercise thereof), then, as of such record date (or the date of such distribution, split or subdivision if no record date is fixed), the per share Warrant Price shall be appropriately decreased, and the number of shares of Common Stock issuable upon exercise hereof shall be appropriately increased, in proportion to such increase of outstanding shares.

          2.3 Combination of Shares . If the number of shares of Common Stock outstanding at any time after the date hereof is decreased by a combination of the outstanding shares of Common Stock, the per share Warrant Price shall be appropriately increased, and the number of shares of Common Stock issuable upon exercise hereof shall be appropriately decreased, in proportion to such decrease in outstanding shares.

          2.4 Adjustments for Other Distributions . In the event the Company shall declare a distribution payable in securities of the Company (other than Common Stock or Common Stock Equivalents) or other Persons, evidences of indebtedness issued by the Company or other Persons, assets (including cash dividends) or options or rights not referred to in subsection 2.2, then, in each such case, upon exercise of this Warrant the holder hereof shall be entitled to a proportionate share of any such distribution as though such holder was the holder of the number of shares of

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Common Stock of the Company into which this Warrant may be exercised as of the record date fixed for the determination of the holders of Common Stock of the Company entitled to receive such distribution.

          2.5 Issuance of Additional Common Stock .

then, and in each such case, the Warrant Price theretofore in effect shall be reduced, concurrently with such issue or sale, to a price (calculated to the nearest. 001 of a cent) determined by multiplying such Warrant Price by a fraction:

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               (b) For the purposes of this Section 2.5, the consideration for the issue or sale of Additional Shares shall, irrespective of the accounting treatment of such consideration, (i) insofar as it consists of cash, be computed at the net amount of cash received by the Company, and (ii) insofar as it consists of property (including securities) other than cash, be computed at the fair market value thereof at the time of such issue or sale as determined in good faith by the Company’s Board of Directors. In the event of a dispute by the holder as to the fair market value of any consideration consisting of property, the Company shall, at the option of the holder, engage a consulting firm or investment banking firm mutually agreed to by the holder and the Company to prepare an independent appraisal of the fair market value of such property to be distributed. The expenses of such appraisal shall be borne by the holder.

               (c) Notwithstanding anything contained herein to the contrary, the consideration for any Common Stock Equivalents shall be deemed to be the total amount of consideration received by the Company for the issuance of such Common Stock Equivalents plus the minimum amount of consideration payable to the Company upon exercise, conversion or exchange of Common Stock Equivalents (the “Net Consideration”), determined as of the date of issuance of such Common Stock Equivalents. Any obligation, agreement or understanding to issue Common Stock Equivalents at any time in the future shall be deemed to be an issuance at the time such obligation or agreement is made or arises. No adjustment of the Warrant Price shall be made under this Section 2.5 upon the issuance of any shares of Common Stock which are issued pursuant to the exercise, conversion or exchange of any Common Stock Equivalents if any adjustment shall previously have been made upon the issuance of any such Common Stock Equivalents.

                    Should the Net Consideration for any such Common Stock Equivalents be increased or decreased from time to time, then, upon the effectiveness of such change, the Warrant Price will be that which would have been obtained (i) had the adjustments made upon the issuance of such Common Stock Equivalents been made upon the basis of the actual Net Consideration (as so increased or decreased) of such Common Stock Equivalents, and (ii) had adjustments to such Warrant Price since the date of issuance of such Common Stock Equivalents been made to such Warrant Price as adjusted pursuant to (i) above. Any adjustment of the Warrant Price pursuant to this paragraph which relates to Common Stock Equivalents shall be disregarded if, as, and when all of such Common Stock Equivalents expire or are canceled without being exercised, so that the Warrant Price effective immediately upon cancellation or expiration shall be equal to the Warrant Price in effect at the time of the issuance of the expired or canceled Common Stock Equivalents, with such additional adjustments as would have been made to such Warrant Price had the expired or canceled Common Stock Equivalents not been issued.

               (d) “Additional Shares” means all shares of Common Stock, whether or not subsequently reacquired or retired by the Company, other than (i) shares of Common Stock issued or to be issued to directors, officers, employees and consultants of the Company pursuant to any bona fide qualified or non-qualified stock option plan, stock purchase plan, stock restriction

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agreement, or employee stock ownership plan (“ESOP”); (ii) all shares of Common Stock issued or deemed to be issued and outstanding under this Section 2.5 on the date of this Warrant; (iii) all securities issued pursuant to any agreement to license technology and/or provide sponsored research upon approval of the Board; and (iv) all securities issued in connection with the lease of equipment or in similar transactions upon the approval of the Board.

               (e) The number of shares of Common Stock that the holder of this Warrant shall be entitled to receive upon each exercise hereof after any adjustment pursuant to this Section 2.5 shall be determined by multiplying (i) the number of shares of Common Stock that were issuable immediately prior to such adjustment, by (ii) the fraction of which (A) the numerator is the Warrant Price immediately prior to such adjustment and (B) the denominator is the Warrant Price immediately following such adjustment.

          2.6 Certificate as to Adjustments . In the case of each adjustment or readjustment of the Warrant Price pursuant to this Section 2, the Company at its expense shall promptly compute such adjustment or readjustment in accordance with the terms hereof and cause a certificate, signed by the Company’s Chief Financial Officer, setting forth such adjustment or readjustment and showing in detail the facts upon which such adjustment or readjustment is based, to be delivered to the holder of this Warrant. The certificate furnished to such holder shall set forth (a) such adjustments and readjustments, (b) the Warrant Price at the time in effect and how it was calculated and (c) the number of shares of Common Stock issuable upon exercise hereof and the amount, if any, of other property at the time receivable upon the exercise of this Warrant.

          2.7 No Impairment . The Company shall not, by amendment of its articles of incorporation or through any consolidation, merger, reorganization, transfer of assets, dissolution, issue or sale of securities or any other voluntary action, avoid or seek to avoid the observance or performance of any of the terms of this Warrant, but shall at all times in good faith assist in the carrying out of all such terms and in the taking of all such action as may be necessary or appropriate in order to protect the rights of the holder of this Warrant against impairment. Without limiting the generality of the foregoing, the Company (a) shall not permit the par value of any shares of stock receivable upon the exercise of this Warrant to exceed the amount payable therefor upon such exercise, (b) shall take all such action as may be necessary or appropriate in order that the Company may validly and legally issue fully paid and nonassessable shares of stock on the exercise of the Warrants from time to time outstanding; and (c) shall not take any action which results in any adjustments of the Warrant Price if the total number of shares of Common Stock issuable after the action upon the exercise of all of the Warrants would exceed the total number of shares of Common Stock then authorized by the Company’s certificate of incorporation and available for the purpose of issue upon such exercise.

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          2.8 Notices of Record Date, etc . In the event of:

               (a) any taking by the Company of a record of the holders of any class of securities of the Company for the purpose of determining the holders thereof who are entitled to receive any dividend (other than a cash dividend payable out of earned surplus at the same rate as that of the last such cash dividend theretofore paid) or other distribution, or any right to subscribe for, purchase or otherwise acquire any shares of stock of any class or any other securities or property, or to receive any other right;

               (b) any capital reorganization of the Company, any reclassification or recapitalization of the capital stock of the Company or any transfer of all or substantially all of the assets of the Company to any other person or any consolidation or merger involving the Company; or

               (c) any voluntary or involuntary dissolution, liquidation or winding-up of the Company, the Company shall mail to the holder of this Warrant at least thirty (30) days prior to the earliest date specified below, a notice specifying: (i) the date on which any such record is to be taken for the purpose of such dividend, distribution or right, and the amount and character of such dividend, distribution or right; and (ii) the date on which any such reorganization, reclassification, transfer, consolidation, merger, dissolution, liquidation or winding-up is expected to become effective and the record date for determining stockholders entitled to vote thereon and the time,