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Exhibit 4.2    
    


EXHIBIT "F"  


 WARRANT  


No. PW-             


        THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
1933, AS AMENDED OR ANY STATE SECURITIES LAWS. SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE STATE
SECURITIES LAWS.


WARRANT TO PURCHASE 30,000 SHARES

OF COMMON STOCK OF

OPTIMER PHARMACEUTICALS, INC.

(Void after                        , 2010)  


        This certifies that Pacific Sorrento Technology Park, or its assigns ("Holder"), for value received, is entitled to purchase from Optimer
Pharmaceuticals, Inc., a California corporation ("Company"), having a place of business at                        , 30,000
fully paid and nonassessable shares of the Company's Common Stock ("Common
Stock") for cash at a price equal to $5.00 ("Stock Purchase Price") at any time or from time to time up to and including 5:00 p.m. (Pacific Time) on the earlier of (i) one year after the
closing of the initial public offering of the Company's Common Stock pursuant to a registration statement under the Securities Act of 1933, as amended (the "Initial Public Offering") or
(ii) ten (10) years from
the date of this Warrant, such earlier day being referred to herein as the "Expiration Date," upon surrender to the Company at its principal office (or at such other location as the Company may advise
the Holder in writing) of this Warrant with the Form of Subscription attached hereto duly filled in and signed and, if applicable, upon payment in cash or by check of the aggregate Stock Purchase
Price for the number of shares for which this Warrant is being exercised determined in accordance with the provisions hereof. The Company shall deliver notice of the Initial Public Offering to the
Holder at least 30 days prior to the closing thereof. The Stock Purchase Price and the number of shares purchasable hereunder are subject to adjustment as provided in Paragraph 3 of this
Warrant. 


        This
Warrant is subject to the following terms and conditions: 



        1.    EXERCISE; ISSUANCE OF CERTIFICATES; PAYMENT FOR SHARES.    


        1.1    General.    This Warrant is exercised at the option of the
holder of record hereof, at any time or from time to time, up to the Expiration Dare for all or any part of the shares of Common Stock (but not for a fraction of a share) which may be purchased
hereunder. The Company agrees that the shares of Common Stock purchased under this Warrant shall be and are deemed to be issued to the Holder hereof as the record owner of such shares as of the close
of business on the date on which this Warrant shall have been surrendered, properly endorsed, the completed, executed Form of Subscription delivered and payment made for such shares. Certificates for
the shares of Common Stock so purchased, together with any other securities or property to which the Holder hereof is entitled upon such exercise, shall be delivered to the Holder hereof by the
Company at the Company's expense as promptly as practicable and in any event within five (5) business days after the rights represented by this Warrant have been so exercised. In case of a
purchase of less than all the shares which may be purchased under this Warrant, the Company shall cancel this Warrant and execute and deliver a new Warrant or Warrants of like tenor for the balance of
the shares purchasable under the Warrant surrendered upon such purchase to the Holder hereof as promptly as practicable and in any event within five (5) business days. Each stock certificate so
delivered shall be in such denominations of 


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Common
Stock as may be requested by the Holder hereof and shall be registered in the name of such Holder. 


        1.2    Net Issue Exercise.    Notwithstanding any provisions herein to
the contrary, if the fair market value of one share of the Company's Common Stock is greater than the Stock Purchase Price (at the date of calculation as set forth below), in lieu of exercising this
Warrant for cash, the Holder may elect to receive shares equal to the value (as determined below) of this Warrant (or the portion thereof being canceled) by surrender of this Warrant at the principal
office of the Company together with the properly endorsed Form of Subscription and notice of such election in which event the Company shall issue to the Holder a number of shares of Common Stock
computed using the following formula: 



	X =	Y (A-B), where
	 	     A






X =
the number of shares of Common Stock to be issued to the Holder 


Y =
the number of shares of Common Stock purchasable under the Warrant or, if only a portion of the Warrant is being exercised, the portion of the Warrant being canceled (at the date of such
calculation) 


A =
the fair market value of one share of the Company's Common Stock (at the date of such calculation) 


B =
Stock Purchase Price (as adjusted to the date of such calculation) 




For
purposes of the above calculation, prior to the Company's initial public offering, fair market value of one share of Common Stock shall be determined by the Company's Board of Directors in good
faith. 


        2.    SHARES TO BE FULLY PAID; RESERVATION OF SHARES.    The Company
covenants and agrees that all shares of Common Stock which may be issued upon the exercise of the rights represented by this Warrant will, upon issuance, be duly authorized, validly issued, fully paid
and nonassessable and free from all preemptive rights of any shareholder and see of all taxes, liens and charges with respect to the issue thereof. The Company further covenants and agrees that,
during the period within which the rights represented by this Warrant may be exercised, the Company will at all times have authorized and reserved, for the purpose of issue or transfer upon exercise
of the subscription rights evidenced by this Warrant, a sufficient number of shares of authorized but unissued Common Stock, or other securities and property, when and as required to provide for the
exercise of the rights represented by this Warrant. The Company will take all such action as may be necessary to assure that such shares of Common Stock may be issued as provided herein without
violation of any applicable law or regulation, or of any requirements of any domestic securities exchange upon which the Common Stock may be listed; provided, however, that the Company shall not be
required to effect a registration under Federal or State securities laws with respect to such exercise. 



        3.    ADJUSTMENT OF STOCK PURCHASE PRICE AND NUMBER OF SHARES.    The
Stock Purchase Price and the number of shares purchasable upon the exercise of this Warrant shall be subject to adjustment from time to time upon the occurrence of certain events described in this
Paragraph 3. Upon each adjustment of the Stock Purchase Price, the Holder of this Warrant shall thereafter be entitled to purchase, at the Stock Purchase Price resulting from such adjustment,
the number of shares obtained by multiplying the Stock Purchase Price in effect immediately prior to such adjustment by the number of shares purchasable pursuant hereto immediately prior to such
adjustment, and dividing the product thereof by the Stock Purchase Price resulting from such adjustment. 



        3.1    Subdivision or Combination of Stock.    In case the Company
shall at any time subdivide its outstanding shares of Common Stock into a greater number of shares, the Stock Purchase Price 



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in
effect immediately prior to such subdivision shall be proportionately reduced, and conversely, in case the outstanding shares of Common Stock of the Company shall be combined into a smaller number
of shares, the Stock Purchase Price in effect immediately prior to such combination shall be proportionately increased. 


        3.2    Dividends in Common Stock, Other Stock, Property,
Reclassification.    If at any time or from time to time the Holders of Common Stock (or my shares of stock or other securities at the time receivable upon the
exercise of this Warrant) shall have received or become entitled to receive, without payment therefor, 



        (a)   Common
Stock or any shares of stock or anther securities which are at any time directly or indirectly convertible into or exchangeable for Common Stock, or any rights or
options to subscribe for, purchase or otherwise acquire any of the foregoing by way of dividend or other distribution, 


        (b)   any
cash paid or payable otherwise than as a cash dividend, or 


        (c)   Common
Stock or additional stock or other securities or property (including cash) by way of spin-off, split-up, reclassification, combination of
shares or similar corporate rearrangement, (other than shares of Common Stock issued as a stock split or adjustments in respect of which shall be covered by the terms of Paragraph 3.1 above),
then and in each such case, the Holder hereof shall, upon the exercise of this Warrant, be entitled to receive, in addition to the number of shares of Common Stock receivable thereupon, and without
payment of any additional consideration therefor, the amount of stock and other securities and property (including cash in the cases referred to in clause (b) above and this clause (c))
which such Holder would hold on the dale of such exercise had he been the holder of record of such Common Stock as of the dare on which holders of Common
Stock received or became entitled to receive such shares or all other additional stock and other securities and property. 




        3.3    Reorganization, Reclassification, Consolidation, Merger or
Sale.    If any recapitalization, reclassification or reorganization of the capital stock of the Company, or any consolidation or merger of the Company with another
corporation, or the sale of all or substantially all of its assets or other transaction shall be effected in such a way that holders of Common Stock shall be entitled to receive stock, securities, or
other assets or property (an "Organic Change"), then, as a condition of such Organic Change, lawful and adequate provisions shall be made by the Company whereby the Holder hereof shall thereafter have
the right to purchase and receive (in lieu of the shares of the Common Stock of the Company immediately theretofore purchasable and receivable upon the exercise of the rights represented hereby) such
shares of stock, securities or other assets or property as may be issued or payable with respect to or in exchange for a number of outstanding shares of such Common Stock equal to the number of shares
of such stock immediately theretofore purchasable and receivable upon the exercise of the rights represented hereby. In the event of any Organic Change, appropriate provision shall be made by the
Company with respect to the rights and interests of the Holder of this Warrant to the end that the provisions hereof (including, without limitation, provisions for adjustments of the Stock Purchase
Price and of the number of shares purchasable and receivable upon the exercise of this Warrant) shall thereafter be applicable, in relation to any shares of stock, securities of assets thereafter
deliverable upon the exercise hereof. The Company will not effect any such consolidation, merger or sale unless, prior to the consummation thereof, the successor corporation (if other than the
Company) resulting from such consolidation or the corporation purchasing such assets shall assume by written instrument reasonably satisfactory in form and substance to the Holders of a majority of
the warrants to purchase Common Stock then outstanding, executed and mailed or delivered to the registered Holder hereof at the last address of such Holder appearing on the books of the 



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Company,
the obligation to deliver to such Holder such shares of stock, securities or assets as, in accordance with the foregoing provisions, such Holder may be entitled to purchase. 


        3.4    Certain Events.    If any change in the outstanding Common
Stock of the Company or any other event occurs as to which the other provisions of this Paragraph 3 are not strictly applicable or if strictly applicable would not fairly protect the purchase
rights of the Holder of the Warrant in accordance with such provisions then the Board of Directors of the Company shall make an adjustment in the number and class of shares available under the
Warrant, the Stock Purchase Price or the application of such provisions, so as to protect such purchase rights as aforesaid. The adjustment shall be such as will give the Holder of the Warrant upon
exercise for the same aggregate Stock Purchase Price the total number, class and kind of shares as he would have owned had the Warrant been exercised prior to the event and had he continued to hold
such shares until after the event requiring adjustment. 


        3.5    Notices of Change.    



        (a)   Immediately
upon any adjustment in the number or class of shares subject to this Warrant and of the Stock Purchase Price, the Company shall give written notice thereof
to the Holder, setting forth in reasonable detail and certifying the calculation of such adjustment. 



        (b)   The
Company shall give written notice to the Holder at least 10 business days prior to the date on which the Company closes its books or takes a record for determining
rights to receive my dividends or distributions. 


        (c)   The
Company shall also give written notice to the Holder at least 30 business days prior to the date on which an Organic Change shall take place. 





        4.    ISSUE TAX.    The issuance of certificates for shares of Common
Stock upon the exercise of the Warrant shall be made without charge to the Holder of the Warrant for any issue tax (other than any applicable income taxes) in respect thereof; provided, however, that
the Company shall not be required to pay any tax which may be payable in respect of any transfer involved in the issuance and delivery of any certificate in a name other than that of the then Holder
of the Warrant being exercised. 


        5.    CLOSING OF BOOKS.    The Company will at no time close its
transfer books against the transfer of any warrant or of any shares of Common Stock issued or issuable upon the exercise of any warrant in any manner which interferes with the timely exercise of this
Warrant. 


        6.    NO VOTING OR DIVIDEND RIGHTS; LIMITATION OF
LIABILITY.    Nothing contained in this Warrant shall be construed as conferring upon the Holder hereof the right to vote or to consent or to receive notice as a
shareholder of the Company or any other matters or any rights whatsoever as a shareholder of the Company. No dividends or interest shall be payable or accrued in respect of this Warrant or the
interest represented hereby or the shares purchasable hereunder until, and only to the extent that, this Warrant shall have been exercised. No provisions hereof, in the absence of affirmative action
by the holder to purchase shares of Common Stock, and no mere enumeration herein of the rights or privileges of the holder hereof, shall give rise to any liability of such Holder for the Stock
Purchase Price or as a shareholder of the Company, whether such liability is asserted by the Company or by its creditors. 


        7.    WARRANTS TRANSFERABLE.    Subject to compliance with applicable
federal and state securities laws, this Warrant and all rights hereunder are transferable, in whole or in part, without charge to the holder hereof (except for transfer taxes), upon surrender of this
Warrant properly endorsed. Each taker and holder of this Warrant, by taking or holding the same, consents and agrees that this Warrant, when endorsed in blank, shall be deemed negotiable, and that the
holder hereof, when this Warrant shall have been so endorsed, may be treated by the Company, at the Company's option, and all other persons dealing with this Warrant as the absolute owner hereof for
any purpose and as the person 


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entitled
to exercise the rights represented by this Warrant, or to the transfer hereof on the books of the Company any notice to the contrary notwithstanding; but until such transfer on such books,
the Company may treat the registered owner hereof as the owner for all purposes. 



        8.    REGISTRATION RIGHTS.    At any time after exercising this
Warrant, in whole or in part, Holder shall have the right to participate in any registration of Common Stock by the Company under the Securities Act of 1933, as amended, on terms and conditions at
least as favorable as any other holder of Common Stock. 


        9.    RIGHTS AND OBLIGATIONS SURVIVE EXERCISE OF WARRANT.    The
rights and obligations of the Company, of the holder of this Warrant and of the holder of shares of Common Stock issued upon exercise of this Warrant, shall survive the exercise of this Warrant. 


        10.    MODIFICATION AND WAIVER.    This Warrant and any provision
hereof may be changed, waived, discharged or terminated only by an instrument in writing signed by the party against which enforcement of the same is sought. 


        11.    NOTICES.    Any notice, request or other document required or
permitted to be given or delivered to the holder hereof or the Company shall be delivered or shall be sent by certified mail, postage prepaid, to each such holder at its address as shown on the books
of the Company or to the Company at the address indicated therefor in the first paragraph of this Warrant of such other address as either may from time to time provide to the other in writing. 


        12.    BINDING EFFECT ON SUCCESSORS.    This Warrant shall be binding
upon any corporation succeeding the Company by merger, consolidation or acquisition of all or substantially all of the Company's assets. All of the obligations of the Company relating to the Common
Stock issuable upon the exercise of this Warrant shall survive the exercise and termination of this Warrant. All of the covenants and agreements of the Company shall inure to the benefit of the
successors and assigns of the holder hereof. 


        13.    DESCRIPTIVE HEADINGS AND GOVERNING LAW.    The description
headings of the several sections and paragraphs of this Warrant are inserted for convenience only and do not constitute a part of this Warrant. This Warrant shall be construed and enforced in
accordance with, and the rights of the parties shall be governed by, the laws of the State of California. 



        14.    LOST WARRANTS.    The Company represents and warrants to the
Holder hereof that upon receipt of evidence reasonably satisfactory to the Company of the loss, theft, destruction, or mutilation of this Warrant and, in the case of any such loss, theft or
destruction, upon receipt of an indemnity reasonably satisfactory to the Company, or in the case of any such mutilation upon surrender and cancellation of such Warrant, the Company, at its expense,
will make and deliver a new Warrant, of like tenor, in lieu of the lost, stolen, destroyed or mutilated Warrant. 



        15.    FRACTIONAL SHARES.    No fractional shares shall be issued upon
exercise of this Warrant. The Company shall, in lieu of issuing any fractional share, pay the holder entitled to such fraction a sum in cash equal to such fraction multiplied by the then effective
Stock Purchase Price. 


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        IN WITNESS WHEREOF, the Company has caused this Warrant to be duly executed by its officers, thereunto duly authorized this
            day of                        , 2000. 



	 	 	OPTIMER PHARMACEUTICALS, INC.

a California corporation
	

 	
 	

By:	
 	

/s/ MICHAEL CHANG
	 	 	 	 	

	 	 	Title:	 	CEO
	 	 	 	 	

	 	 	By:	 	/s/ TESSIE M. CHE
	 	 	 	 	

	 	 	Title:	 	Sr. V.P., Corp. Dev.
	 	 	 	 	






	ATTEST:	 	 
	 	 	 
	
 Secretary	 	 




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EXHIBIT A 


SUBSCRIPTION
FORM 


Date:                        ,
2000 


[Company Name]

[address]


Attn:
President 


Ladies
and Gentlemen: 


	o
	The
undersigned hereby elects to exercise the warrant issued to it by                        (the "Company") and dated
                             ,        Warrant
No.    (the "Warrant") and to purchase
thereunder                                        
        shares of the Common Stock of the Company
(the "Shares") at a purchase price
of                                         
       Dollars ($            ) per Share or an aggregate purchase price
of                        Dollars ($            ) (the "Purchase
Price").



	o
	The
undersigned hereby elects to convert                        percent (    %) of the value of the Warrant
pursuant to the provisions
of Paragraph 1.2 of the Warrant. 



        Pursuant to the terms of the Warrant the undersigned has delivered the Purchase Price herewith in full, in cash or by certified check or wire transfer. 



	 	 	Very truly yours,
	 	 	 	 	 
	 	 	 	 	 
	 	 	

	 	 	By:	 	 
	 	 	 	 	

	 	 	 	 	 
	 	 	Title:	 	 
	 	 	 	 	





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Exhibit 4.2