COMMONSTOCK PURCHASE WARRANT

Exhibit 4.8

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “1933 ACT”), OR ANY APPLICABLE STATE SECURITIES LAWS, AND MAY NOT BE SOLD OR TRANSFERRED UNLESS SUCH SALE OR TRANSFER IS IN ACCORDANCE WITH THE REGISTRATION REQUIREMENTS OF SUCH ACT AND APPLICABLE LAWS OR SOME OTHER EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF SUCH ACT AND APPLICABLE LAWS IS AVAILABLE WITH RESPECT THERETO.

COMMON STOCK PURCHASE WARRANT

ARYX THERAPEUTICS, INC.

Effective as of October 17, 2008

Void after October 17, 2013

1.             Issuance.  This Common Stock Purchase Warrant (the “Warrant”) is issued to LIGHTHOUSE CAPITAL PARTNERS V, L.P. (the “Holder”) by ARYX THERAPEUTICS, INC., a Delaware corporation (hereinafter with its successors called the “Company”).

2.                                      Purchase Price; Number of Shares.

(a)           The registered holder of this Warrant, commencing on the date hereof, is entitled upon surrender of this Warrant with the subscription form annexed hereto duly executed, at the principal office of the Company, to purchase from the Company, at a price per share equal to $3.97516 (the “Purchase Price”), 158,770 fully paid and nonassessable shares of the Company’s Common Stock, par value $0.001 per share  (the “Common Stock”).

Any term not defined herein shall have the meaning as set forth in the Loan Agreement.

Until such time as this Warrant is exercised in full or expires, the Purchase Price and the securities issuable upon exercise of this Warrant are subject to adjustment as hereinafter provided.  The person or persons in whose name or names any certificate representing shares of Common Stock is issued hereunder shall be deemed to have become the holder of record of the shares represented thereby as at the close of business on the date this Warrant is exercised with respect to such shares, whether or not the transfer books of the Company shall be closed.

3.             Payment of Purchase Price.  The Purchase Price may be paid (i) in cash or by check, (ii) by the surrender by the Holder to the Company of any promissory notes or other obligations issued by the Company, with all such notes and obligations so surrendered being credited against the Purchase Price in an amount equal to the principal amount thereof plus accrued interest to the date of surrender, or (iii) by any combination of the foregoing.

4.             Net Issue Election.  The Holder may elect to receive, without the payment by the Holder of any additional consideration, shares of Common Stock equal to the value of this Warrant or any portion hereof by the surrender of this Warrant or such portion to the Company, with the net issue election notice annexed hereto duly executed, at the principal office of the Company.  Thereupon, the Company shall issue to the Holder such number of fully paid and nonassessable shares of Common Stock as is computed using the following formula:

For purposes of this Warrant, the “Fair Market Value” of a share of Common Stock as of the date that the net issue election is made (the “Determination Date”) shall mean: (i) if traded on a securities exchange or the NASDAQ Global Market, the fair market value of the Common Stock shall be deemed to be the average of the closing or last reported sale prices of the Common Stock on such exchange or market for the five (5) consecutive trading days immediately prior to the Determination Date, or (ii) if otherwise traded in an over-the-counter market, the fair market value of the Common Stock shall be deemed to be the average of the closing ask prices of the Common Stock for the five (5) consecutive trading days immediately prior to the Determination Date, or (iii) if there is no public market for the Common Stock or if the fair market value cannot be calculated as of the Determination Date on any of the foregoing bases, then the fair market value shall be determined in good faith by the Company’s Board of Directors.

5.             Partial Exercise.  This Warrant may be exercised in part, and the Holder shall be entitled to receive a new warrant, which shall be dated as of the date of this Warrant, covering the number of shares in respect of which this Warrant shall not have been exercised.

6.             Fractional Shares.  In no event shall any fractional share of Common Stock be issued upon any exercise of this Warrant.  If, upon exercise of this Warrant in its entirety, the Holder would, except as provided in this Section 6, be entitled to receive a fractional share of Common Stock, then the Company shall, in lieu of issuance of any fractional share, pay the Holder otherwise entitled to such fraction a sum in cash equal to the product resulting from multiplying the then current Fair Market Value of one share of Common Stock by such fraction.

7.             Expiration Date; Automatic Exercise.  This Warrant shall expire at the earliest to occur of (i) the close of business on October 17, 2013; or (ii) the effective date of a Merger as defined below, unless otherwise assumed per the language below (the “Expiration Date”) and shall be void thereafter.

“Merger” means: (i) a sale, license or other disposition of all or substantially all of the Company’s assets to an Unaffiliated Entity (as defined below), or (ii) the merger, consolidation or acquisition of the Company with, into or by an Unaffiliated Entity (other than a merger or consolidation for the principle purpose of changing the domicile of the Company or a bona fide stock equity financing), the result of which is that stockholders of the Company immediately prior to the merger, consolidation or acquisition do not own or control more than fifty percent (50%) of the voting power of the surviving entity immediately following such merger, consolidation or acquisition.  “Unaffiliated Entity” means any entity that is owned or controlled by parties who own less than twenty percent (20%) of the combined voting power of the voting securities of the Company immediately prior to such merger, consolidation or acquisition.  Notwithstanding the foregoing, in the event that any outstanding warrants to purchase equity securities of the Company are assumed by the successor entity of a Merger (or parent thereof), this Warrant will be similarly assumed.    Notwithstanding anything to the contrary in this Warrant, if Holder exercises this Warrant after receiving a notice from the Company of a proposed merger or if the exercise was otherwise precipitated by such proposed Merger, the Company will hold the exercise notice, without processing such notice, until immediately prior to the consummation of the Merger, at which time the exercise notice shall be processed. If the Merger is terminated, the Holder will have ten (10) business days from the date the Company gives Holder notice indicating such termination to rescind its exercise notice, otherwise the exercise notice shall be processed by

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the Company as set forth herein.  In the event of such rescission, this Warrant will continue to be exercisable on the same terms and conditions.

Notwithstanding the foregoing, this Warrant shall automatically be deemed to be exercised in full pursuant to the provisions of Section 4 hereof, without any further action on behalf of the Holder, immediately prior to the time this Warrant would otherwise expire pursuant to this Section 7, unless otherwise assumed per above.

8.             Reserved Shares; Valid Issuance.  The Company covenants that it will at all times from and after the date hereof reserve and keep available such number of its authorized shares of Common Stock issuable upon exercise of this Warrant free from all preemptive or similar rights therein.  The Company further covenants that such shares as may be issued pursuant to such exercise will, upon issuance, be duly and validly issued, fully paid and nonassessable and free from all taxes, liens and charges with respect to the issuance thereof.

9.             Stock Splits and Dividends.  If after the date hereof the Company shall subdivide the Common Stock, by split-up or otherwise, or combine the Common Stock, or issue additional shares of Common Stock in payment of a stock dividend on the Common Stock, the number of shares of Common Stock issuable on the exercise of this Warrant shall forthwith be proportionately increased in the case of a subdivision or stock dividend, or proportionately decreased in the case of a combination, and the Purchase Price shall forthwith be proportionately decreased in the case of a subdivision or stock dividend, or proportionately increased in the case of a combination.

11.          Mergers and Reclassifications.  Subject to Section 7, if after the date hereof the Company shall enter into any Reorganization (as hereinafter defined), then, as a condition of such Reorganization, lawful provisions shall be made, and duly executed documents evidencing the same from the Company or its successor shall be delivered to the Holder, so that the Holder shall thereafter have the right to purchase, at a total price not to exceed that payable upon the exercise of this Warrant in full, the kind and amount of shares of stock and other securities and property receivable upon such Reorganization by a holder of the number of shares of Common Stock which might have been purchased by the Holder immediately prior to such Reorganization, and in any such case appropriate provisions shall be made with respect to the rights and interest of the Holder to the end that the provisions hereof (including without limitation, provisions for the adjustment of the Purchase Price and the number of shares issuable hereunder and the provisions relating to the net issue election) shall thereafter be applicable in relation to any shares of stock or other securities and property thereafter deliverable upon exercise hereof.  For the purposes of this Section 11, the term “Reorganization” shall include without limitation any reclassification, capital reorganization or change of the Common Stock (other than as a result of a subdivision, combination or stock dividend provided for in Section 9 hereof), or any consolidation of the Company with, or merger of the Company into, another corporation or other business organization (other than a merger in which the Company is the surviving corporation and which does not result in any reclassification or change of the outstanding Common Stock), or any sale or conveyance to another corporation or other business organization of all or substantially all of the assets of the Company.

12.          Certificate of Adjustment.  Whenever the Purchase Price is adjusted, as herein provided, the Company shall promptly deliver to the Holder a certificate of the Company’s chief financial officer setting forth the Purchase Price after such adjustment and setting forth a brief statement of the facts requiring such adjustment.

13.          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 for the purpose of determining the holders thereof who are entitled to receive any dividend or other distribution, or any right to subscribe for, purchase, sell or otherwise acquire or dispose of any shares of stock of any class or any other securities or property, or to receive any other right;

(b)           any reclassification of the capital stock of the Company, capital reorganization of the Company, consolidation or merger involving the Company, or sale or conveyance of all or substantially all of its assets; or

(c)           any voluntary or involuntary dissolution, liquidation or winding-up of the Company;

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then in each such event the Company will provide or cause to be provided to the Holder a written notice thereof.  Such notice shall be provided at least ten (10) business days prior to the date specified in such notice on which any such action is to be taken.

14.          Representations, Warranties and Covenants.  This Warrant is issued and delivered by the Company and accepted by each Holder on the basis of the following representations, warranties and covenants made by the Company:

(a)           The Company has all necessary authority to issue, execute and deliver this Warrant and to perform its obligations hereunder.  This Warrant has been duly authorized issued, executed and delivered by the Company and is the valid and binding obligation of the Company, enforceable in accordance with its terms.

(b)           The shares of Common Stock issuable upon the exercise of this Warrant have been duly authorized and reserved for issuance by the Company and, when issued in accordance with the terms hereof, will be validly issued, fully paid and nonassessable.

(c)           The issuance, execution and delivery of this Warrant do not, and the issuance of the shares of Common Stock upon the exercise of this Warrant in accordance with the terms hereof will not, (i) violate or contravene the Company’s Certificate of Incorporation or by-laws, or any law, statute, regulation, rule, judgment or order applicable to the Company, (ii) violate, contravene or result in a material breach or default under any material contract, material agreement or material instrument to which the Company is a party or by which the Company or any of its assets are bound or (iii) require the consent or approval of or the filing of any notice or registration with any person or entity.

16.          Amendment.  The terms of this Warrant may be amended, modified or waived only with the written consent of the Holder and the Company.

17.          Representations and Covenants of the Holder.  This Warrant has been entered into by the Company in reliance upon the following representations and covenants of the Holder, which by its execution hereof the Holder hereby confirms:

(a)           Investment Purpose.  The right to acquire Common Stock issuable upon exercise of the Holder’s rights contained herein will be acquired for investment and not with a view to the sale or distribution of any part thereof, and the Holder has no present intention of selling or engaging in any public distribution of the same except pursuant to a registration or exemption.

(b)           Accredited Investor.  Holder is an “accredited investor” within the meaning of Rule 501 of Regulation D promulgated under the 1933 Act.

(c)           Private Issue.  The Holder understands (i) that the Common Stock issuable upon exercise of the Holder’s rights contained herein is not registered under the 1933 Act or qualified under applicable state securities laws on the ground that the issuance contemplated by this Warrant will be exempt from the registration and qualifications requirements thereof, and (ii) that the Company’s reliance on such exemption is predicated on the representations set forth in this Section 17.

(d)           Financial Risk.  Holder understands that the purchase of this Warrant and its underlying securities involves substantial risk.  Holder has experience as an investor in securities of companies in the development stage and acknowledges that Holder can bear the economic risk of such Holder’s investment in this Warrant and its underlying securities and has such knowledge and experience in financial or business matters that Holder is capable of evaluating the merits and risks of its investment in this Warrant and its underlying securities and/or has a preexisting personal or business relationship with the Company and certain of its officers, directors or controlling persons of a nature and duration that enables Holder to be aware of the character, business acumen and financial circumstances of such persons.

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(e)           Rule 144. The Holder is aware that neither the Warrant, nor the Common Stock issuable upon conversion thereof may be sold pursuant to Rule 144 adopted under the 1933 Act unless certain conditions are met, including, among other things, the existence of a public market for the shares, the availability of certain current public information about the Company, the resale following the required holding period under Rule 144 and the number of shares being sold during any three month period not exceeding specified limitations. Holder is aware that the Company has no obligation hereunder to satisfy the conditions for resale set forth in Rule 144.

18.          Notices, Transfers, Etc.

(a)           Any notice or written communication required or permitted hereunder shall be in writing and shall be deemed effectively given: (a) upon personal delivery to the party to be notified, (b) when sent by confirmed facsimile to the facsimile number specified in writing by the recipient if sent during normal business hours of the recipient on a business day, if not, then on the next business day, or (c) the next business day after deposit with a nationally recognized overnight courier, specifying next day delivery, with written verification of receipt.  All communications shall be sent to the Company or the Holder at the address listed on the signature page hereto or at such other address as the Company or Holder may designate by ten (10) days advance written notice to the other party hereto.

(b)           Subject to compliance with applicable federal and state securities laws and the terms hereof, this Warrant may be transferred by the Holder with respect to any or all of the shares purchasable hereunder.  Upon surrender of this Warrant to the Company, together with the assignment notice annexed hereto duly executed, for transfer of this Warrant as an entirety by the Holder, the Company shall issue a new warrant of the same denomination to the assignee.  Upon surrender of this Warrant to the Company, together with the assignment hereof properly endorsed, by the Holder for transfer with respect to a portion of the shares of Common Stock purchasable hereunder, the Company shall issue a new warrant to the assignee, in such denomination as shall be requested by the Holder hereof, and shall issue to such Holder a new warrant covering the number of shares in respect of which this Warrant shall not have been transferred.

(c)           In case this Warrant shall be mutilated, lost, stolen or destroyed, the Company shall, on such terms as to indemnity or otherwise as it may reasonably impose (which shall, in the case of a mutilated Warrant, include the surrender thereof), issue a new warrant of like tenor and denomination and deliver the same (i) in exchange and substitution for and upon surrender and cancellation of any mutilated Warrant, or (ii) in lieu of any Warrant lost, stolen or destroyed, upon receipt of an affidavit of the Holder or other evidence reasonably satisfactory to the Company of the loss, theft or destruction of such Warrant

19.          Governing Law.  The provisions and terms of this Warrant shall be governed by and construed in accordance with the internal laws of the State of California without giving effect to its principles regarding conflicts of laws.

20.          Successors and Assigns.  This Warrant shall be binding upon the Company’s successors and assigns and shall inure to the benefit of the Holder’s successors, legal representatives and permitted assigns.

21.          Business Days.  If the last or appointed day for the taking of any action required or the expiration of any rights granted herein shall be a Saturday or Sunday or a legal holiday in California, then such action may be taken or right may be exercised on the next succeeding day which is not a Saturday or Sunday or such a legal holiday.

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22.          No Stockholder Rights. This Warrant in and of itself shall not entitle the Holder to any voting rights or other rights as a stockholder of the Company.

Accepted and Agreed:

LIGHTHOUSE CAPITAL PARTNERS V, L.P.

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Subscription

The undersigned hereby subscribes for                                    shares of Common Stock covered by this Warrant.  The certificate(s) for such shares shall be issued in the name of the undersigned or as otherwise indicated below:

Net Issue Election Notice

The undersigned hereby elects under Section 4 to surrender the right to purchase shares of Common Stock pursuant to this Warrant.  The certificate(s) for such shares issuable upon such net issue election shall be issued in the name of the undersigned or as otherwise indicated below:

Assignment

For value received                                                                                hereby sells, assigns and transfers unto

[Please print or typewrite name and address of Assignee]

the within Warrant, and does hereby irrevocably constitute and appoint                                                                      its attorney to transfer the within Warrant on the books of the within named Company with full power of substitution on the premises.