AKESIS PHARMACEUTICALS, INC. WARRANT TO PURCHASE CAPITAL STOCK

Exhibit 4.2

THIS WARRANT AND THE UNDERLYING SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”). NO SALE OR DISPOSITION THEREOF MAY BE EFFECTED EXCEPT IN COMPLIANCE WITH RULE 144 UNDER SUCH ACT OR AN EFFECTIVE REGISTRATION STATEMENT RELATED THERETO OR AN OPINION OF COUNSEL FOR THE HOLDER SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED UNDER THE ACT OR RECEIPT OF A NO-ACTION LETTER FROM THE U.S. SECURITIES AND EXCHANGE COMMISSION.

AKESIS PHARMACEUTICALS, INC.

WARRANT TO PURCHASE CAPITAL STOCK

Void After [ — ], 2013

T HIS C ERTIFIES T HAT , for value received, Avalon Ventures VII, L.P. (the “Holder” ) is entitled to subscribe for and purchase during the Exercise Period (as defined below) for the Applicable Price Per Share (as defined below) from A KESIS P HARMACEUTICALS , I NC . , a Nevada corporation (the “Company” ), up to that number of fully paid and nonassessable shares of Warrant Stock (as defined below) as is determined in accordance with Section 2.1 below.

This Warrant to Purchase Capital Stock (this “Warrant” ) has been issued pursuant to that certain Note and Warrant Purchase Agreement, dated as of September 29, 2008 (the “Agreement” ), by and between the Company and Holder. Pursuant to the Agreement, the Company also issued to Holder a Convertible Promissory Note, dated as of even date herewith (the “Note” ), for the aggregate principal amount of $ [•] (the “Original Holder Principal Amount” ).

1. D EFINITIONS . Capitalized terms used and not otherwise defined herein are intended to have the meanings given to them in the Note. In addition, the following capitalized terms used herein shall have the following respective meanings:

1.1 “Applicable Per Share Price” shall mean the price per Qualifying Financing Share paid by investors in a Qualifying Financing; provided , however , that the Applicable Price Per Share shall be subject to adjustment from time to time in accordance with Section 4.

1.2 “Coverage Amount” shall mean and be equal to fifteen percent (15%) of the Original Holder Principal Amount.

1.3 “Exercise Period” shall mean the period commencing on the date of the closing of a Qualifying Financing (if any) and ending on [•] , 2013, unless earlier terminated as provided below.

1.4 “Fair Market Value” shall mean, as applicable: (i) in the case of any Warrant Stock traded on a national securities exchange, the value equal to the average of the closing prices of such Warrant Stock on such exchange over the ten (10) trading day period ending one (1) trading day prior to the date this Warrant is being exercised; (ii) in the case of Warrant Stock actively traded over-the-counter, the value equal to the average of the closing bid or sale prices (whichever is applicable) over the ten (10) trading day period ending one (1) trading day prior to the date this Warrant is being exercised; and (iii) in the event that there is no active public market for the Warrant Stock, the value equal to the fair market value thereof, as determined in good faith by the Board of Directors of the Company on the date this Warrant is being exercised.

1.5 “Warrant Price” shall mean, in connection with any exercise of this Warrant, the aggregate exercise price for the shares of Warrant Stock being acquired in connection with such exercise, as determined by multiplying the number of shares of Warrant Stock being acquired in connection with such exercise by the Applicable Price Per Share.

1.6 “Warrant Stock” shall mean Qualifying Financing Shares.

2. E XERCISE OF W ARRANT .

2.1 General. At any time during the Exercise Period, this Warrant may be exercised, in whole or in part and in accordance with the provisions set forth in this Section 2, for that number of shares of Warrant Stock as is equal to: (i) the Coverage Amount; divided by (ii) the Applicable Per Share Price.

2.2 Mechanics of Exercise. In order to effect the exercise of this Warrant, Holder shall deliver to the Company: (i) this Warrant; (ii) an executed Notice of Exercise in the form attached hereto as Exhibit A ; and (ii) except as set forth in Section 2.3, payment of the Warrant Price in cash by wire transfer of immediately available funds or such other form of cash payment as may be accepted by the Company in its discretion. Upon receipt of all of the foregoing, the Company shall promptly: (x) issue to Holder a certificate representing the shares of Warrant Stock being acquired hereunder; and (y) if applicable, issue to Holder a new warrant, substantially identical in form and substance to this Warrant, representing the right to purchase the remaining shares of Warrant Stock underlying this Warrant.

2.3 Net Exercise . Notwithstanding any provisions herein to the contrary, if the Fair Market Value of one share of Warrant Stock is greater than the Applicable Per Share Price on the date on which this Warrant is exercised, in lieu of exercising this Warrant by payment of cash, Holder may elect to receive that number of shares of Warrant Stock as determined in accordance with the following formula:

X = Y(A-B)

            A

Where:       X =   the number of shares of Warrant Stock to be issued to Holder;

2.

3. C OVENANTS OF THE C OMPANY .

3.1 Covenants as to Exercise Shares. The Company covenants and agrees that all shares of Warrant Stock that may be issued upon the exercise of the rights represented by this Warrant will, upon issuance, be validly issued and outstanding, fully paid and nonassessable, and free from all taxes, liens and charges with respect to the issuance thereof, other than taxes, liens or charges created by or imposed upon Holder through no action of the Company.

3.2 Notices of Record Date. In the event of 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, the Company shall deliver to Holder, at l