Document:

EXHIBIT 4.11

 

OPTIMER
PHARMACEUTICALS, INC.

and

                  ,
AS WARRANT AGENT

FORM OF
COMMON STOCK

WARRANT AGREEMENT

DATED
AS OF                   

 

 

OPTIMER
PHARMACEUTICALS, INC.

 

FORM OF
COMMON STOCK WARRANT AGREEMENT

 

     COMMON STOCK WARRANT AGREEMENT (this “Agreement”),
dated as of                
between OPTIMER PHARMACEUTICALS, INC.,
a Delaware corporation (the “Company”) and, a [corporation] [national banking
association] organized and existing under the laws of                
and having a corporate trust office in                ,
as warrant agent (the “Warrant Agent”).

 

     WHEREAS, the Company proposes to sell [if
Warrants are sold with other securities—[title of such other securities being
offered] (the “Other Securities”) with] warrant certificates evidencing one or
more warrants (the “Warrants” or, individually, a “Warrant”) representing the
right to purchase Common Stock of the Company, par value $0.001 per share (the “Warrant
Securities”), such warrant certificates and other warrant certificates issued
pursuant to this Agreement being herein called the “Warrant Certificates”; and

 

     WHEREAS, the Company desires the Warrant
Agent to act on behalf of the Company, and the Warrant Agent is willing so to
act, in connection with the issuance, registration, transfer, exchange,
exercise and replacement of the Warrant Certificates, and in this Agreement
wishes to set forth, among other things, the form and provisions of the Warrant
Certificates and the terms and conditions on which they may be issued,
registered, transferred, exchanged, exercised and replaced.

 

     NOW THEREFORE, in consideration of the
premises and of the mutual agreements herein contained, the parties hereto
agree as follows:

 

ARTICLE
1

 

ISSUANCE
OF WARRANTS AND EXECUTION AND DELIVERY OF WARRANT CERTIFICATES

 

     1.1 Issuance Of Warrants. [If Warrants
alone—Upon issuance, each Warrant Certificate shall evidence one or more
Warrants.] [If Other Securities and Warrants—Warrant Certificates shall be
[initially] issued in connection with the issuance of the Other Securities [but
shall be separately transferable on and after                
(the “Detachable Date”)] [and shall not be separately transferable] and each
Warrant Certificate shall evidence one or more Warrants.] Each Warrant
evidenced thereby shall represent the right, subject to the provisions
contained herein and therein, to purchase one Warrant Security. [If Other
Securities and Warrants—Warrant Certificates shall be initially issued in units
with the Other Securities and each Warrant Certificate included in such a unit
shall evidence                
Warrants for each [ $               
principal amount] [               shares]
of Other Securities included in such unit.]

 

     1.2 Execution And Delivery Of Warrant Certificates.
Each Warrant Certificate, whenever issued, shall be in registered form
substantially in the form set forth in Exhibit A hereto, shall be dated
the date of its countersignature by the Warrant Agent and may have such
letters, numbers, or other marks of identification or designation and such
legends or endorsements printed, lithographed or engraved thereon as the
officers of the Company executing the same may approve (execution thereof to be
conclusive evidence of such approval) and as are not inconsistent with the
provisions of this Agreement, or as may be required to comply with any law or
with any rule or regulation made pursuant thereto or with any rule or
regulation of any securities exchange on which the Warrants may be listed, or
to conform to usage. The Warrant Certificates shall be signed on behalf of the
Company by any of its present or future chief executive officers, presidents,
senior vice presidents, vice presidents, chief financial officers, chief legal
officers, treasurers, assistant treasurers, controllers, assistant controllers,
secretaries or assistant secretaries under its corporate seal reproduced
thereon. Such signatures may be manual or facsimile signatures of such
authorized officers and may be imprinted or otherwise reproduced on the Warrant
Certificates. The seal of the Company may be in the form of a facsimile thereof
and may be impressed, affixed, imprinted or otherwise reproduced on the Warrant
Certificates.

 

 

     No
Warrant Certificate shall be valid for any purpose, and no Warrant evidenced
thereby shall be exercisable, until such Warrant Certificate has been
countersigned by the manual signature of the Warrant Agent. Such signature by
the Warrant Agent upon any Warrant Certificate executed by the Company shall be
conclusive evidence that the Warrant Certificate so countersigned has been duly
issued hereunder.

 

     In
case any officer of the Company who shall have signed any of the Warrant
Certificates either manually or by facsimile signature shall cease to be such officer
before the Warrant Certificates so signed shall have been countersigned and
delivered by the Warrant Agent, such Warrant Certificates may be countersigned
and delivered notwithstanding that the person who signed Warrant Certificates
ceased to be such officer of the Company; and any Warrant Certificate may be
signed on behalf of the Company by such persons as, at the actual date of the
execution of such Warrant Certificate, shall be the proper officers of the
Company, although at the date of the execution of this Agreement any such
person was not such officer.

 

     The
term “holder” or “holder of a Warrant Certificate” as used herein shall mean
any person in whose name at the time any Warrant Certificate shall be
registered upon the books to be maintained by the Warrant Agent for that
purpose [If Other Securities and Warrants are not immediately detachable—or
upon the registration of the Other Securities prior to the Detachable Date.
Prior to the Detachable Date, the Company will, or will cause the registrar of
the Other Securities to, make available at all times to the Warrant Agent such
information as to holders of the Other Securities as may be necessary to keep
the Warrant Agent’s records up to date].

 

     1.3 Issuance Of Warrant Certificates. Warrant
Certificates evidencing the right to purchase Warrant Securities may be
executed by the Company and delivered to the Warrant Agent upon the execution
of this Warrant Agreement or from time to time thereafter. The Warrant Agent
shall, upon receipt of Warrant Certificates duly executed on behalf of the
Company, countersign such Warrant Certificates and shall deliver such Warrant
Certificates to or upon the order of the Company.

 

ARTICLE
2

 

WARRANT
PRICE, DURATION AND EXERCISE OF WARRANTS

 

     2.1 Warrant Price. During the period
specified in Section 2.2, each Warrant shall, subject to the terms of this
Warrant Agreement and the applicable Warrant Certificate, entitle the holder
thereof to purchase the number of Warrant Securities specified in the applicable
Warrant Certificate at an exercise price of $               per
Warrant Security, subject to adjustment upon the occurrence of certain events,
as hereinafter provided. Such purchase price per Warrant Security is referred
to in this Agreement as the “Warrant Price.”

 

     2.2 Duration Of Warrants. Each Warrant may
be exercised in whole or in part at any time, as specified herein, on or after
[the date thereof] [               ]
and at or before [          ] p.m.,
[City] time, on                
or such later date as the Company may designate by notice to the Warrant Agent
and the holders of Warrant Certificates mailed to their addresses as set forth
in the record books of the Warrant Agent (the “Expiration Date”). Each Warrant
not exercised at or before [          ] p.m.,
[City] time, on the Expiration Date shall become void, and all rights of the
holder of the Warrant Certificate evidencing such Warrant under this Agreement
shall cease.

 

     2.3 Exercise Of Warrants.

 

          (a) During the period specified in Section 2.2,
the Warrants may be exercised to purchase a whole number of Warrant Securities
in registered form by providing certain information as set forth on the reverse
side of the Warrant Certificate and by paying in full, in lawful money of the
United States of America, [in cash or by certified check or official bank check
in New York Clearing House funds] [by bank wire transfer in immediately
available funds] the Warrant Price for each Warrant Security with respect to
which a Warrant is being exercised to the Warrant Agent at its corporate trust
office, provided that such exercise is subject to receipt within five business
days of such payment by the Warrant Agent of the Warrant Certificate with the
form of election to purchase Warrant Securities set forth on the reverse side
of the Warrant Certificate properly completed and duly executed. The date on
which payment in full of the Warrant Price is received by the Warrant Agent
shall, subject to receipt of the Warrant Certificate as aforesaid, be deemed to
be the date on which the Warrant is exercised; provided, however, that if, at
the date of receipt of such 

 

 

Warrant Certificates and
payment in full of the Warrant Price, the transfer books for the Warrant
Securities purchasable upon the exercise of such Warrants shall be closed, no
such receipt of such Warrant Certificates and no such payment of such Warrant
Price shall be effective to constitute the person so designated to be named as
the holder of record of such Warrant Securities on such date, but shall be
effective to constitute such person as the holder of record of such Warrant
Securities for all purposes at the opening of business on the next succeeding
day on which the transfer books for the Warrant Securities purchasable upon the
exercise of such Warrants shall be opened, and the certificates for the Warrant
Securities in respect of which such Warrants are then exercised shall be
issuable as of the date on such next succeeding day on which the transfer books
shall next be opened, and until such date the Company shall be under no duty to
deliver any certificate for such Warrant Securities. The Warrant Agent shall
deposit all funds received by it in payment of the Warrant Price in an account
of the Company maintained with it and shall advise the Company by telephone at
the end of each day on which a payment for the exercise of Warrants is received
of the amount so deposited to its account. The Warrant Agent shall promptly
confirm such telephone advice to the Company in writing.

 

          (b) The Warrant Agent shall, from time
to time, as promptly as practicable, advise the Company of (i) the number
of Warrant Securities with respect to which Warrants were exercised, (ii) the
instructions of each holder of the Warrant Certificates evidencing such
Warrants with respect to delivery of the Warrant Securities to which such
holder is entitled upon such exercise, (iii) delivery of Warrant
Certificates evidencing the balance, if any, of the Warrants for the remaining
Warrant Securities after such exercise, and (iv) such other information as
the Company shall reasonably require.

 

          (c) As soon as practicable after the
exercise of any Warrant, the Company shall issue to or upon the order of the
holder of the Warrant Certificate evidencing such Warrant the Warrant
Securities to which such holder is entitled, in fully registered form,
registered in such name or names as may be directed by such holder. If fewer
than all of the Warrants evidenced by such Warrant Certificate are exercised,
the Company shall execute, and an authorized officer of the Warrant Agent shall
manually countersign and deliver, a new Warrant Certificate evidencing Warrants
for the number of Warrant Securities remaining unexercised.

 

          (d) The Company shall not be required
to pay any stamp or other tax or other governmental charge required to be paid
in connection with any transfer involved in the issue of the Warrant
Securities, and in the event that any such transfer is involved, the Company
shall not be required to issue or deliver any Warrant Security until such tax
or other charge shall have been paid or it has been established to the Company’s
satisfaction that no such tax or other charge is due.

 

          (e) Prior to the issuance of any
Warrants there shall have been reserved, and the Company shall at all times
through the Expiration Date keep reserved, out of its authorized but unissued
Warrant Securities, a number of shares sufficient to provide for the exercise
of the Warrants.

 

ARTICLE
3

 

OTHER
PROVISIONS RELATING TO RIGHTS OF HOLDERS OF WARRANT CERTIFICATES

 

     3.1 No Rights As Warrant Securityholder Conferred By
Warrants Or Warrant Certificates. No Warrant Certificate or Warrant
evidenced thereby shall entitle the holder thereof to any of the rights of a
holder of Warrant Securities, including, without limitation, the right to
receive the payment of dividends or distributions, if any, on the Warrant
Securities or to exercise any voting rights, except to the extent expressly set
forth in this Agreement or the applicable Warrant Certificate.

 

     3.2 Lost, Stolen, Mutilated Or Destroyed Warrant
Certificates. Upon receipt by the Warrant Agent of evidence
reasonably satisfactory to it and the Company of the ownership of and the loss,
theft, destruction or mutilation of any Warrant Certificate and/or indemnity
reasonably satisfactory to the Warrant Agent and the Company and, in the case
of mutilation, upon surrender of the mutilated Warrant Certificate to the
Warrant Agent for cancellation, then, in the absence of notice to the Company
or the Warrant Agent that such Warrant Certificate has been acquired by a bona
fide purchaser, the Company shall execute, and an authorized officer of the
Warrant Agent shall manually countersign and deliver, in exchange for or in lieu
of the lost, stolen, destroyed or mutilated 

 

 

Warrant Certificate, a
new Warrant Certificate of the same tenor and evidencing Warrants for a like
number of Warrant Securities. Upon the issuance of any new Warrant Certificate
under this Section 3.2, the Company may require the payment of a sum
sufficient to cover any tax or other governmental charge that may be imposed in
relation thereto and any other expenses (including the fees and expenses of the
Warrant Agent) in connection therewith. Every substitute Warrant Certificate
executed and delivered pursuant to this Section 3.2 in lieu of any lost,
stolen or destroyed Warrant Certificate shall represent an additional
contractual obligation of the Company, whether or not the lost, stolen or
destroyed Warrant Certificate shall be at any time enforceable by anyone, and
shall be entitled to the benefits of this Agreement equally and proportionately
with any and all other Warrant Certificates duly executed and delivered
hereunder. The provisions of this Section 3.2 are exclusive and shall
preclude (to the extent lawful) all other rights and remedies with respect to
the replacement of mutilated, lost, stolen or destroyed Warrant Certificates.

 

     3.3 Holder Of Warrant Certificate May Enforce
Rights. Notwithstanding any of the provisions of this Agreement, any
holder of a Warrant Certificate, without the consent of the Warrant Agent, the
holder of any Warrant Securities or the holder of any other Warrant
Certificate, may, in such holder’s own behalf and for such holder’s own
benefit, enforce, and may institute and maintain any suit, action or proceeding
against the Company suitable to enforce, or otherwise in respect of, such
holder’s right to exercise the Warrants evidenced by such holder’s Warrant
Certificate in the manner provided in such holder’s Warrant Certificate and in
this Agreement.

 

     3.4 Adjustments.

 

          (a) In case the Company shall at any
time subdivide its outstanding shares of Common Stock into a greater number of
shares, the Warrant Price in effect immediately prior to such subdivision shall
be proportionately reduced and the number of Warrant Securities purchasable
under the Warrants shall be proportionately increased. Conversely, in case the
outstanding shares of Common Stock of the Company shall be combined into a
smaller number of shares, the Warrant Price in effect immediately prior to such
combination shall be proportionately increased and the number of Warrant
Securities purchasable under the Warrants shall be proportionately decreased.

 

          (b) If at any time or from time to
time the holders of Common Stock (or any shares of stock or other securities at
the time receivable upon the exercise of the Warrants) shall have received or
become entitled to receive, without payment therefore,

 

               (i) Common Stock or any shares of
stock or other 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;

 

               (ii) any cash paid or payable
otherwise than as a cash dividend paid or payable out of the Company’s current
or retained earnings;

 

               (iii) any evidence of the Company’s
indebtedness or rights to subscribe for or purchase the Company’s indebtedness;
or

 

               (iv) Common Stock or additional stock
or other securities or property (including cash) by way of spinoff, 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 Section 3.4(a) above),
then and in each such case, the holder of each Warrant shall, upon the exercise
of the Warrant, be entitled to receive, in addition to the number of Warrant
Securities receivable thereupon, and without payment of any additional
consideration therefore, the amount of stock and other securities and property
(including cash and indebtedness or rights to subscribe for or purchase
indebtedness) which such holder would hold on the date of such exercise had he
been the holder of record of such Warrant Securities as of the date on which
holders of Common Stock received or became entitled to receive such shares or
all other additional stock and other securities and property.

 

          (c) In case of (i) any
reclassification, capital reorganization, or change in the Common Stock of the
Company (other than as a result of a subdivision, combination, or stock
dividend provided for in Section 3.4(a) or Section 3.4(b) above),
(ii) share exchange, merger or similar transaction of the Company with or
into another person 

 

 

or entity (other than a
share exchange, merger or similar transaction in which the Company is the
acquiring or surviving corporation and which does not result in any change in
the Common Stock other than the issuance of additional shares of Common Stock)
or (iii) the sale, exchange, lease, transfer or other disposition of all
or substantially all of the properties and assets of the Company as an entirety
(in any such case, a “Reorganization Event”), then, as a condition of such
Reorganization Event, lawful provisions shall be made, and duly executed
documents evidencing the same from the Company or its successor shall be
delivered to the holders of the Warrants, so that the holders of the Warrants
shall have the right at any time prior to the expiration of the Warrants to
purchase, at a total price equal to that payable upon the exercise of the
Warrants, the kind and amount of shares of stock and other securities and
property receivable in connection with such Reorganization Event by a holder of
the same number of Warrant Securities as were purchasable by the holders of the
Warrants immediately prior to such Reorganization Event. In any such case
appropriate provisions shall be made with respect to the rights and interests
of the holders of the Warrants so that the provisions hereof shall thereafter
be applicable with respect to any shares of stock or other securities and
property deliverable upon exercise the Warrants, and appropriate adjustments
shall be made to the Warrant Price payable hereunder provided the aggregate
purchase price shall remain the same. In the case of any transaction described
in clauses (ii) and (iii) above, the Company shall thereupon be
relieved of any further obligation hereunder or under the Warrants, and the
Company as the predecessor corporation may thereupon or at any time thereafter
be dissolved, wound up or liquidated. Such successor or assuming entity
thereupon may cause to be signed, and may issue either in its own name or in
the name of the Company, any or all of the Warrants issuable hereunder which
heretofore shall not have been signed by the Company, and may execute and
deliver securities in its own name, in fulfillment of its obligations to
deliver Warrant Securities upon exercise of the Warrants. All the Warrants so
issued shall in all respects have the same legal rank and benefit under this
Agreement as the Warrants theretofore or thereafter issued in accordance with
the terms of this Agreement as though all of such Warrants had been issued at
the date of the execution hereof. In any case of any such Reorganization Event,
such changes in phraseology and form (but not in substance) may be made in the
Warrants thereafter to be issued as may be appropriate.

 

     The
Warrant Agent may receive a written opinion of legal counsel as conclusive
evidence that any such Reorganization Event complies with the provisions of
this Section 3.4.

 

          (d) The Company may, at its option, at
any time until the Expiration Date, reduce the then current Warrant Price to
any amount deemed appropriate by the Board of Directors of the Company for any
period not exceeding twenty consecutive days (as evidenced in a resolution
adopted by such Board of Directors), but only upon giving the notices required
by Section 3.5 at least ten days prior to taking such action.

 

          (e) Except as herein otherwise
expressly provided, no adjustment in the Warrant Price shall be made by reason
of the issuance of shares of Common Stock, or securities convertible into or
exchangeable for shares of Common Stock, or securities carrying the right to
purchase any of the foregoing or for any other reason whatsoever.

 

          (f) No fractional Warrant Securities shall be issued
upon the exercise of Warrants.  If more than one Warrant shall be
exercised at one time by the same holder, the number of full Warrant Securities
which shall be issuable upon such exercise shall be computed on the basis of
the aggregate number of Warrant Securities purchased pursuant to the Warrants
so exercised.  Instead of any fractional Warrant Security which would
otherwise be issuable upon exercise of any Warrant, the Company shall pay a
cash adjustment in respect of such fraction in an amount equal to the same
fraction of the last reported sale price (or bid price if there were no sales)
per Warrant Security, in either case as reported on the principal registered
national securities exchange on which the Warrant Securities are listed or
admitted to trading on the business day that next precedes the day of exercise
or, if the Warrant Securities are not then listed or admitted to trading on any
registered national securities exchange, the average of the closing high bid
and low asked prices as reported on the OTC Bulletin Board Service (the “OTC Bulletin Board”) operated by the
Financial Industry Regulatory Authority, Inc. (“FINRA”) or, if not available on the OTC Bulletin Board, then the
average of the closing high bid and low asked prices as reported on any other
U.S. quotation medium or inter-dealer quotation system on such date, or if on
any such date the Warrant Securities are not listed or admitted to trading on a
registered national securities exchange, are not included in the OTC Bulletin
Board, and are not quoted on any other U.S. quotation medium or inter-dealer
quotation system, an amount equal to the same fraction of the average of the
closing bid and asked prices as furnished by any FINRA member firm selected
from time to time by the Company for that purpose at the close of business on
the business day that next precedes the day of exercise.

 

 

          (g) Whenever the Warrant Price then in
effect is adjusted as herein provided, the Company shall mail to each holder of
the Warrants at such holder’s address as it shall appear on the books of the
Company a statement setting forth the adjusted Warrant Price then and
thereafter effective under the provisions hereof, together with the facts, in
reasonable detail, upon which such adjustment is based.

 

     3.5 Notice To Warrantholders. In case the
Company shall (a) effect any dividend or distribution described in Section 3.4(b),
(b) effect any Reorganization Event, (c) make any distribution on or
in respect of the Common Stock in connection with the dissolution, liquidation
or winding up of the Company, or (d) reduce the then current Warrant Price
pursuant to Section 3.4(d), then the Company shall mail to each holder of
Warrants at such holder’s address as it shall appear on the books of the
Warrant Agent, at least ten days prior to the applicable date hereinafter
specified, a notice stating (x) the record date for such dividend or
distribution, or, if a record is not to be taken, the date as of which the
holders of record of Common Stock that will be entitled to such dividend or
distribution are to be determined, (y) the date on which such
Reorganization Event, dissolution, liquidation or winding up is expected to
become effective, and the date as of which it is expected that holders of
Common Stock of record shall be entitled to exchange their shares of Common
Stock for securities or other property deliverable upon such Reorganization
Event, dissolution, liquidation or winding up, or (z) the first date on
which the then current Warrant Price shall be reduced pursuant to Section 3.4(d).
No failure to mail such notice nor any defect therein or in the mailing thereof
shall affect any such transaction or any adjustment in the Warrant Price
required by Section 3.4.

 

     3.6 [If The Warrants Are Subject To Acceleration By
The Company, Insert—Acceleration Of Warrants By The Company.

 

          (a) At any time on or after                        ,
the Company shall have the right to accelerate any or all Warrants at any time
by causing them to expire at the close of business on the day next preceding a
specified date (the “Acceleration Date”), if the Market Price (as hereinafter
defined) of the Common Stock equals or exceeds                   
percent (                  %)
of the then effective Warrant Price on any twenty Trading Days (as hereinafter
defined) within a period of thirty consecutive Trading Days ending no more than
five Trading Days prior to the date on which the Company gives notice to the
Warrant Agent of its election to accelerate the Warrants.

 

          (b) “Market Price” for each Trading Day shall be, if the Common Stock
is listed or admitted to trading on any registered national securities
exchange, the last reported sale price, regular way (or, if no such price is
reported, the average of the reported closing bid and asked prices, regular
way) of Common Stock, in either case as reported on the principal registered
national securities exchange on which the Common Stock is listed or admitted to
trading or, if not listed or admitted to trading on any registered national
securities exchange, the average of the closing high bid and low asked prices
as reported on the OTC Bulletin Board operated by FINRA, or if not available on
the OTC Bulletin Board, then the average of the closing high bid and low asked
prices as reported on any other U.S. quotation medium or inter-dealer quotation
system, or if on any such date the shares of Common Stock are not listed or
admitted to trading on a registered national securities exchange, are not
included in the OTC Bulletin Board, and are not quoted on any other U.S.
quotation medium or inter-dealer quotation system, the average of the closing
bid and asked prices as furnished by any FINRA member firm selected from time
to time by the Company for that purpose. “Trading Day” shall be each Monday through Friday, other than any
day on which securities are not traded in the system or on the exchange that is
the principal market for the Common Stock, as determined by the Board of
Directors of the Company.

 

          (c) In the event of an acceleration of
less than all of the Warrants, the Warrant Agent shall select the Warrants to
be accelerated by lot, pro rata or in such other manner as it deems, in its
discretion, to be fair and appropriate.

 

          (d) Notice of an acceleration
specifying the Acceleration Date shall be sent by mail first class, postage
prepaid, to each registered holder of a Warrant Certificate representing a
Warrant accelerated at such holder’s address appearing on the books of the
Warrant Agent not more than sixty days nor less than thirty days before the
Acceleration Date. Such notice of an acceleration also shall be given no more
than twenty days, and no less than ten days, prior to the mailing of notice to
registered holders of Warrants pursuant to this Section 3.6, by
publication at least once in a newspaper of general circulation in the City of
New York.

 

          (e) Any Warrant accelerated may be exercised
until [          ] p.m.,
[City] time, on the business day next preceding the Acceleration Date. The
Warrant Price shall be payable as provided in Section 2.]

 

 

ARTICLE
4

 

EXCHANGE
AND TRANSFER OF WARRANT CERTIFICATES

 

     4.1 Exchange And Transfer Of Warrant Certificates.
[If Other Securities with Warrants which are immediately detachable—Upon] [If
Other Securities with Warrants which are not immediately detachable—Prior to
the Detachable Date, a Warrant Certificate may be exchanged or transferred only
together with the Other Security to which the Warrant Certificate was initially
attached, and only for the purpose of effecting or in conjunction with an
exchange or transfer of such Other Security. Prior to any Detachable Date, each
transfer of the Other Security shall operate also to transfer the related
Warrant Certificates. After the Detachable Date, upon] surrender at the
corporate trust office of the Warrant Agent, Warrant Certificates evidencing
Warrants may be exchanged for Warrant Certificates in other denominations
evidencing such Warrants or the transfer thereof may be registered in whole or
in part; provided that such other Warrant Certificates evidence Warrants for
the same aggregate number of Warrant Securities as the Warrant Certificates so
surrendered. The Warrant Agent shall keep, at its corporate trust office, books
in which, subject to such reasonable regulations as it may prescribe, it shall
register Warrant Certificates and exchanges and transfers of outstanding
Warrant Certificates, upon surrender of the Warrant Certificates to the Warrant
Agent at its corporate trust office for exchange or registration of transfer,
properly endorsed or accompanied by appropriate instruments of registration of
transfer and written instructions for transfer, all in form satisfactory to the
Company and the Warrant Agent. No service charge shall be made for any exchange
or registration of transfer of Warrant Certificates, but the Company may
require payment of a sum sufficient to cover any stamp or other tax or other
governmental charge that may be imposed in connection with any such exchange or
registration of transfer. Whenever any Warrant Certificates are so surrendered
for exchange or registration of transfer, an authorized officer of the Warrant Agent
shall manually countersign and deliver to the person or persons entitled
thereto a Warrant Certificate or Warrant Certificates duly authorized and
executed by the Company, as so requested. The Warrant Agent shall not be
required to effect any exchange or registration of transfer which will result
in the issuance of a Warrant Certificate evidencing a Warrant for a fraction of
a Warrant Security or a number of Warrants for a whole number of Warrant
Securities and a fraction of a Warrant Security. All Warrant Certificates
issued upon any exchange or registration of transfer of Warrant Certificates
shall be the valid obligations of the Company, evidencing the same obligations
and entitled to the same benefits under this Agreement as the Warrant
Certificate surrendered for such exchange or registration of transfer.

 

     4.2 Treatment Of Holders Of Warrant Certificates.
[If Other Securities and Warrants are not immediately detachable—Prior to the
Detachable Date, the Company, the Warrant Agent and all other persons may treat
the owner of the Other Security as the owner of the Warrant Certificates
initially attached thereto for any purpose and as the person entitled to
exercise the rights represented by the Warrants evidenced by such Warrant
Certificates, any notice to the contrary notwithstanding. After the Detachable
Date and prior to due presentment of a Warrant Certificate for registration of
transfer, the] [The] Company, the Warrant Agent and all other persons may treat
the registered holder of a Warrant Certificate as the absolute owner thereof
for any purpose and as the person entitled to exercise the rights represented
by the Warrants evidenced thereby, any notice to the contrary notwithstanding.

 

     4.3 Cancellation Of Warrant Certificates.
Any Warrant Certificate surrendered for exchange, registration of transfer or
exercise of the Warrants evidenced thereby shall, if surrendered to the
Company, be delivered to the Warrant Agent and all Warrant Certificates
surrendered or so delivered to the Warrant Agent shall be promptly canceled by
the Warrant Agent and shall not be reissued and, except as expressly permitted
by this Agreement, no Warrant Certificate shall be issued hereunder in exchange
therefor or in lieu thereof.

 

     The
Warrant Agent shall deliver to the Company from time to time or otherwise
dispose of canceled Warrant Certificates in a manner satisfactory to the
Company.

 

ARTICLE
5

 

CONCERNING
THE WARRANT AGENT

 

     5.1 Warrant Agent. The Company hereby
appoints                        
as Warrant Agent of the Company in respect of the Warrants and the Warrant
Certificates upon the terms and subject to the conditions herein set forth, 

 

 

and                        
hereby accepts such appointment. The Warrant Agent shall have the powers and authority
granted to and conferred upon it in the Warrant Certificates and hereby and
such further powers and authority to act on behalf of the Company as the
Company may hereafter grant to or confer upon it. All of the terms and
provisions with respect to such powers and authority contained in the Warrant
Certificates are subject to and governed by the terms and provisions hereof.

 

     5.2 Conditions Of Warrant Agent’s Obligations.
The Warrant Agent accepts its obligations herein set forth upon the terms and
conditions hereof, including the following to all of which the Company agrees
and to all of which the rights hereunder of the holders from time to time of
the Warrant Certificates shall be subject:

 

          (a) Compensation And Indemnification.
The Company agrees promptly to pay the Warrant Agent the compensation to be
agreed upon with the Company for all services rendered by the Warrant Agent and
to reimburse the Warrant Agent for reasonable out-of-pocket expenses (including
reasonable counsel fees) incurred without negligence, bad faith or willful
misconduct by the Warrant Agent in connection with the services rendered
hereunder by the Warrant Agent. The Company also agrees to indemnify the
Warrant Agent for, and to hold it harmless against, any loss, liability or
expense incurred without negligence, bad faith or willful misconduct on the
part of the Warrant Agent, arising out of or in connection with its acting as
Warrant Agent hereunder, including the reasonable costs and expenses of
defending against any claim of such liability.

 

          (b) Agent For The Company. In acting
under this Warrant Agreement and in connection with the Warrant Certificates,
the Warrant Agent is acting solely as agent of the Company and does not assume
any obligations or relationship of agency or trust for or with any of the
holders of Warrant Certificates or beneficial owners of Warrants.

 

          (c) Counsel. The Warrant Agent may
consult with counsel satisfactory to it, which may include counsel for the
Company, and the written advice of such counsel shall be full and complete
authorization and protection in respect of any action taken, suffered or
omitted by it hereunder in good faith and in accordance with the advice of such
counsel.

 

          (d) Documents. The Warrant Agent shall
be protected and shall incur no liability for or in respect of any action taken
or omitted by it in reliance upon any Warrant Certificate, notice, direction,
consent, certificate, affidavit, statement or other paper or document
reasonably believed by it to be genuine and to have been presented or signed by
the proper parties.

 

          (e) Certain Transactions. The Warrant
Agent, and its officers, directors and employees, may become the owner of, or
acquire any interest in, Warrants, with the same rights that it or they would
have if it were not the Warrant Agent hereunder, and, to the extent permitted
by applicable law, it or they may engage or be interested in any financial or
other transaction with the Company and may act on, or as depositary, trustee or
agent for, any committee or body of holders of Warrant Securities or other
obligations of the Company as freely as if it were not the Warrant Agent
hereunder. Nothing in this Warrant Agreement shall be deemed to prevent the
Warrant Agent from acting as trustee under any indenture to which the Company
is a party.

 

          (f) No Liability For Interest. Unless
otherwise agreed with the Company, the Warrant Agent shall have no liability
for interest on any monies at any time received by it pursuant to any of the
provisions of this Agreement or of the Warrant Certificates.

 

          (g) No Liability For Invalidity. The
Warrant Agent shall have no liability with respect to any invalidity of this
Agreement or any of the Warrant Certificates (except as to the Warrant Agent’s
countersignature thereon).

 

          (h) No Responsibility For Representations.
The Warrant Agent shall not be responsible for any of the recitals or
representations herein or in the Warrant Certificates (except as to the Warrant
Agent’s countersignature thereon), all of which are made solely by the Company.

 

          (i) No Implied Obligations. The
Warrant Agent shall be obligated to perform only such duties as are herein and
in the Warrant Certificates specifically set forth and no implied duties or
obligations shall be read into this Agreement or the Warrant Certificates
against the Warrant Agent. The Warrant Agent shall not be under any 

 

 

obligation to take any
action hereunder which may tend to involve it in any expense or liability, the
payment of which within a reasonable time is not, in its reasonable opinion,
assured to it. The Warrant Agent shall not be accountable or under any duty or
responsibility for the use by the Company of any of the Warrant Certificates authenticated
by the Warrant Agent and delivered by it to the Company pursuant to this
Agreement or for the application by the Company of the proceeds of the Warrant
Certificates. The Warrant Agent shall have no duty or responsibility in case of
any default by the Company in the performance of its covenants or agreements
contained herein or in the Warrant Certificates or in the case of the receipt
of any written demand from a holder of a Warrant Certificate with respect to
such default, including, without limiting the generality of the foregoing, any
duty or responsibility to initiate or attempt to initiate any proceedings at
law or otherwise or, except as provided in Section 6.2 hereof, to make any
demand upon the Company.

 

     5.3 Resignation, Removal And Appointment Of Successors.

 

          (a) The Company agrees, for the
benefit of the holders from time to time of the Warrant Certificates, that
there shall at all times be a Warrant Agent hereunder until all the Warrants
have been exercised or are no longer exercisable.

 

          (b) The Warrant Agent may at any time
resign as agent by giving written notice to the Company of such intention on
its part, specifying the date on which its desired resignation shall become
effective; provided that such date shall not be less than three months after
the date on which such notice is given unless the Company otherwise agrees. The
Warrant Agent hereunder may be removed at any time by the filing with it of an
instrument in writing signed by or on behalf of the Company and specifying such
removal and the intended date when it shall become effective. Such resignation
or removal shall take effect upon the appointment by the Company, as
hereinafter provided, of a successor Warrant Agent (which shall be a bank or
trust company authorized under the laws of the jurisdiction of its organization
to exercise corporate trust powers) and the acceptance of such appointment by
such successor Warrant Agent. The obligation of the Company under Section 5.2(a) shall
continue to the extent set forth therein notwithstanding the resignation or
removal of the Warrant Agent.

 

          (c) In case at any time the Warrant
Agent shall resign, or shall be removed, or shall become incapable of acting,
or shall be adjudged a bankrupt or insolvent, or shall commence a voluntary
case under the Federal bankruptcy laws, as now or hereafter constituted, or
under any other applicable Federal or state bankruptcy, insolvency or similar
law or shall consent to the appointment of or taking possession by a receiver,
custodian, liquidator, assignee, trustee, sequestrator (or other similar
official) of the Warrant Agent or its property or affairs, or shall make an
assignment for the benefit of creditors, or shall admit in writing its
inability to pay its debts generally as they become due, or shall take
corporate action in furtherance of any such action, or a decree or order for
relief by a court having jurisdiction in the premises shall have been entered
in respect of the Warrant Agent in an involuntary case under the Federal
bankruptcy laws, as now or hereafter constituted, or any other applicable
Federal or state bankruptcy, insolvency or similar law, or a decree or order by
a court having jurisdiction in the premises shall have been entered for the
appointment of a receiver, custodian, liquidator, assignee, trustee,
sequestrator (or similar official) of the Warrant Agent or of its property or
affairs, or any public officer shall take charge or control of the Warrant
Agent or of its property or affairs for the purpose of rehabilitation,
conservation, winding up or liquidation, a successor Warrant Agent, qualified
as aforesaid, shall be appointed by the Company by an instrument in writing,
filed with the successor Warrant Agent. Upon the appointment as aforesaid of a
successor Warrant Agent and acceptance by the successor Warrant Agent of such
appointment, the Warrant Agent shall cease to be Warrant Agent hereunder.

 

          (d) Any successor Warrant Agent
appointed hereunder shall execute, acknowledge and deliver to its predecessor
and to the Company an instrument accepting such appointment hereunder, and
thereupon such successor Warrant Agent, without any further act, deed or
conveyance, shall become vested with all the authority, rights, powers, trusts,
immunities, duties and obligations of such predecessor with like effect as if
originally named as Warrant Agent hereunder, and such predecessor, upon payment
of its charges and disbursements then unpaid, shall thereupon become obligated
to transfer, deliver and pay over, and such successor Warrant Agent shall be
entitled to receive, all monies, securities and other property on deposit with
or held by such predecessor, as Warrant Agent hereunder.

 

 

          (e) Any corporation into which the
Warrant Agent hereunder may be merged or converted or any corporation with
which the Warrant Agent may be consolidated, or any corporation resulting from
any merger, conversion or consolidation to which the Warrant Agent shall be a
party, or any corporation to which the Warrant Agent shall sell or otherwise
transfer all or substantially all the assets and business of the Warrant Agent,
provided that it shall be qualified as aforesaid, shall be the successor Warrant
Agent under this Agreement without the execution or filing of any paper or any
further act on the part of any of the parties hereto.

 

ARTICLE
6

 

MISCELLANEOUS

 

     6.1 Amendment. This Agreement may be
amended by the parties hereto, without the consent of the holder of any Warrant
Certificate, for the purpose of curing any ambiguity, or of curing, correcting
or supplementing any defective provision contained herein, or making any other
provisions with respect to matters or questions arising under this Agreement as
the Company and the Warrant Agent may deem necessary or desirable; provided
that such action shall not materially adversely affect the interests of the
holders of the Warrant Certificates.

 

     6.2 Notices And Demands To The Company And Warrant
Agent. If the Warrant Agent shall receive any notice or demand
addressed to the Company by the holder of a Warrant Certificate pursuant to the
provisions of the Warrant Certificates, the Warrant Agent shall promptly
forward such notice or demand to the Company.

 

     6.3 Addresses. Any communication from the
Company to the Warrant Agent with respect to this Agreement shall be addressed
to                 ,
Attention:                
and any communication from the Warrant Agent to the Company with respect to
this Agreement shall be addressed to Optimer Pharmaceuticals, Inc., 10110
Sorrento Valley Road, Suite C, San Diego, California, 92121, Attention:
Corporate Secretary (or such other address as shall be specified in writing by
the Warrant Agent or by the Company).

 

     6.4 Governing Law. This Agreement and each
Warrant Certificate issued hereunder shall be governed by and construed in
accordance with the laws of the State of New York.

 

     6.5 Delivery Of Prospectus. The Company
shall furnish to the Warrant Agent sufficient copies of a prospectus meeting
the requirements of the Securities Act of 1933, as amended, relating to the
Warrant Securities deliverable upon exercise of the Warrants (the “Prospectus”),
and the Warrant Agent agrees that upon the exercise of any Warrant, the Warrant
Agent will deliver to the holder of the Warrant Certificate evidencing such
Warrant, prior to or concurrently with the delivery of the Warrant Securities
issued upon such exercise, a Prospectus.

 

     The
Warrant Agent shall not, by reason of any such delivery, assume any
responsibility for the accuracy or adequacy of such Prospectus.

 

     6.6 Obtaining Of Governmental Approvals.
The Company will from time to time take all action which may be necessary to
obtain and keep effective any and all permits, consents and approvals of
governmental agencies and authorities and securities act filings under United
States Federal and state laws (including without limitation a registration
statement in respect of the Warrants and Warrant Securities under the
Securities Act of 1933, as amended), which may be or become requisite in
connection with the issuance, sale, transfer, and delivery of the Warrant
Securities issued upon exercise of the Warrants, the issuance, sale, transfer
and delivery of the Warrants or upon the expiration of the period during which
the Warrants are exercisable.

 

     6.7 Persons Having Rights Under Warrant Agreement.
Nothing in this Agreement shall give to any person other than the Company, the
Warrant Agent and the holders of the Warrant Certificates any right, remedy or
claim under or by reason of this Agreement.

 

     6.8 Headings. The descriptive headings of
the several Articles and Sections of this Agreement are inserted for
convenience only and shall not control or affect the meaning or construction of
any of the provisions hereof.

 

 

     6.9 Counterparts. This Agreement may be
executed in any number of counterparts, each of which as so executed shall be
deemed to be an original, but such counterparts shall together constitute but
one and the same instrument.

 

     6.10 Inspection Of Agreement. A copy of
this Agreement shall be available at all reasonable times at the principal
corporate trust office of the Warrant Agent for inspection by the holder of any
Warrant Certificate. The Warrant Agent may require such holder to submit his
Warrant Certificate for inspection by it.

 

     IN WITNESS WHEREOF, the parties hereto have
caused this Agreement to be duly executed, all as of the day and year first
above written.

 

	
   

  	
  OPTIMER
  PHARMACEUTICALS, INC.

  
	
   

  	
   

  
	
   

  	
  By

  	
   

  
	
   

  	
   

  	
  Its

  	
   

  
	
   

  	
   

  
	
  Attest:

  	
   

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  Warrant Agent

  
	
   

  	
   

  	
   

  
	
   

  	
  By

  	
   

  
	
   

  	
   

  	
  Its

  	
   

  
	
   

  	
   

  
	
  Attest:

  	
   

  

 

 

[SIGNATURE PAGE TO
COMMON STOCK WARRANT AGREEMENT]

 

 

EXHIBIT
A

 

FORM OF
WARRANT CERTIFICATE

 

[FACE
OF WARRANT CERTIFICATE]

 

	
   

  	
   

  	
   

  
	
  [[Form if Warrants
  are attached to Other Securities and are not immediately detachable.] 

  	
   

  	
  [Prior to                      
     , this Warrant Certificate cannot be transferred or
  exchanged unless attached to a [Title of Other Securities].]

  
	
   

  	
   

  	
   

  
	
  [Form of Legend if
  Warrants are not immediately exercisable.] 

  	
   

  	
  [Prior to                      
     , Warrants evidenced by this Warrant Certificate cannot be
  exercised.]

  

 

EXERCISABLE ONLY
IF COUNTERSIGNED BY THE WARRANT AGENT AS PROVIDED HEREIN

VOID AFTER [       
    ] P.M., [CITY] TIME, ON       
                 ,

 

 

OPTIMER
PHARMACEUTICALS, INC.

 

WARRANT
CERTIFICATE REPRESENTING

WARRANTS TO PURCHASE

 

COMMON
STOCK, PAR VALUE $0.001 PER SHARE

 

	
  No.                 
  

  	
   

  	
  Warrants

  

 

     This certifies that                
or registered assigns is the registered owner of the above indicated number of
Warrants, each Warrant entitling such owner [if Warrants are attached to Other
Securities and are not immediately detachable—, subject to the registered owner
qualifying as a “Holder” of this Warrant Certificate, as hereinafter defined),]
to purchase, at any time [after [               ] p.m.,
[City] time, on           
and] on or before [          ] p.m.,
[City] time, on           ,                
shares of Common Stock, par value $0.001 per share (the “Warrant Securities”),
of Optimer Pharmaceuticals, Inc. (the “Company”) on the following basis:
during the period from                ,
through and including                ,
the exercise price per Warrant Security will be $          ,
subject to adjustment as provided in the Warrant Agreement (as hereinafter
defined) (the “Warrant Price”). The Holder may exercise the Warrants evidenced
hereby by providing certain information set forth on the back hereof and by
paying in full, in lawful money of the United States of America, [in cash or by
certified check or official bank check in New York Clearing House funds] [by
bank wire transfer in immediately available funds], the Warrant Price for each
Warrant Security with respect to which this Warrant is exercised to the Warrant
Agent (as hereinafter defined) and by surrendering this Warrant Certificate,
with the purchase form on the back hereof duly executed, at the corporate trust
office of [name of Warrant Agent], or its successor as warrant agent (the “Warrant
Agent”), which is, on the date hereof, at the address specified on the reverse
hereof, and upon compliance with and subject to the conditions set forth herein
and in the Warrant Agreement (as hereinafter defined).

 

     The
term “Holder” as used herein shall mean [if Warrants are attached to Other
Securities and are not immediately detachable—prior to                     ,
               
(the “Detachable Date”), the registered owner of the Company’s [title of Other
Securities] to which this Warrant Certificate was initially attached, and after
such Detachable Date,] the person in whose name at the time this Warrant
Certificate shall be registered upon the books to be maintained by the Warrant
Agent for that purpose pursuant to Section 4 of the Warrant Agreement.

 

     The
Warrants evidenced by this Warrant Certificate may be exercised to purchase a
whole number of Warrant Securities in registered form. Upon any exercise of
fewer than all of the Warrants evidenced by this Warrant Certificate, there
shall be issued to the Holder hereof a new Warrant Certificate evidencing
Warrants for the number of Warrant Securities remaining unexercised.

 

     This
Warrant Certificate is issued under and in accordance with the Warrant
Agreement dated as of                       ,
               
(the “Warrant Agreement”), between the Company and the Warrant Agent and is
subject to the terms and provisions contained in the Warrant Agreement, to all
of which terms and provisions the Holder of this Warrant Certificate consents
by acceptance hereof. Copies of the Warrant Agreement are on file at the
above-mentioned office of the Warrant Agent.

 

     [If
Warrants are attached to Other Securities and are not immediately detachable —
Prior to the Detachable Date, this Warrant Certificate may be exchanged or
transferred only together with the [Title of Other Securities] (the “Other
Securities”) to which this Warrant Certificate was initially attached, and only
for the purpose of effecting or in conjunction with, an exchange or transfer of
such Other Security. Additionally, on or prior to the Detachable Date, each
transfer of such Other Security on the register of the Other Securities shall
operate also to transfer this Warrant Certificate. After such date, transfer of
this] [If Warrants are attached to Other Securities and are immediately
detachable — Transfer of this] Warrant Certificate may be registered when this
Warrant Certificate is surrendered at the corporate trust office of the Warrant
Agent by the registered owner or such owner’s assigns, in the manner and
subject to the limitations provided in the Warrant Agreement.

 

 

     [If
Other Securities with Warrants which are not immediately detachable — Except as
provided in the immediately preceding paragraph, after] [If Other Securities
with Warrants which are immediately detachable or Warrants alone — After]
countersignature by the Warrant Agent and prior to the expiration of this
Warrant Certificate, this Warrant Certificate may be exchanged at the corporate
trust office of the Warrant Agent for Warrant Certificates representing
Warrants for the same aggregate number of Warrant Securities.

 

     This
Warrant Certificate shall not entitle the Holder hereof to any of the rights of
a holder of the Warrant Securities, including, without limitation, the right to
receive payments of dividends or distributions, if any, on the Warrant
Securities (except to the extent set forth in the Warrant Agreement) or to
exercise any voting rights.

 

     Reference
is hereby made to the further provisions of this Warrant Certificate set forth
on the reverse hereof, which further provisions shall for all purposes have the
same effect as if set forth at this place.

 

     This
Warrant Certificate shall not be valid or obligatory for any purpose until
countersigned by the Warrant Agent.

 

     IN WITNESS WHEREOF, the Company has caused
this Warrant to be executed in its name and on its behalf by the facsimile
signatures of its duly authorized officers.

 

	
  Dated:

  	
   

  
	
   

  	
   

  
	
   

  	
  OPTIMER
  PHARMACEUTICALS, INC.

  
	
   

  	
  By

  	
   

  
	
   

  	
   

  	
  Its

  	
   

  
	
   

  	
   

  
	
   

  	
   

  
	
  Attest:

  	
   

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  Countersigned:  

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  As Warrant Agent

  
	
   

  	
   

  
	
   

  	
  By

  	
   

  
	
   

  	
         Authorized
  Signature

  

 

 

[REVERSE
OF WARRANT CERTIFICATE]

 

(Instructions
for Exercise of Warrant)

 

     To
exercise any Warrants evidenced hereby for Warrant Securities (as hereinafter
defined), the Holder must pay, in lawful money of the United States of America,
[in cash or by certified check or official bank check in New York Clearing
House funds] [by bank wire transfer in immediately available funds], the
Warrant Price in full for Warrants exercised, to [Warrant Agent] [address of
Warrant Agent], Attn:                ,
which payment must specify the name of the Holder and the number of Warrants
exercised by such Holder. In addition, the Holder must complete the information
required below and present this Warrant Certificate in person or by mail
(certified or registered mail is recommended) to the Warrant Agent at the
appropriate address set forth above. This Warrant Certificate, completed and duly
executed, must be received by the Warrant Agent within five business days of
the payment.

 

(To be executed
upon exercise of Warrants)

 

     The
undersigned hereby irrevocably elects to exercise                
Warrants, evidenced by this Warrant Certificate, to purchase                 shares
of the Common Stock, par value $0.001 per share (the “Warrant Securities”), of
Optimer Pharmaceuticals, Inc. and represents that he has tendered payment
for such Warrant Securities, in lawful money of the United States of America,
[in cash or by certified check or official bank check in New York Clearing
House funds] [by bank wire transfer in immediately available funds], to the
order of Optimer Pharmaceuticals, Inc., c/o [insert name and address of
Warrant Agent], in the amount of $           
in accordance with the terms hereof. The undersigned requests that said Warrant
Securities be in fully registered form in the authorized denominations,
registered in such names and delivered all as specified in accordance with the
instructions set forth below.

 

     If
the number of Warrants exercised is less than all of the Warrants evidenced
hereby, the undersigned requests that a new Warrant Certificate evidencing the
Warrants for the number of Warrant Securities remaining unexercised be issued
and delivered to the undersigned unless otherwise specified in the instructions
below.

 

	
  Dated

  	
   

  	
   

  	
  Name

  	
   

  
	
   

  	
   

  	
   

  	
  Please Print

  
	
   

  	
   

  	
   

  	
   

  
	
  Address:

  	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
  (Insert Social Security
  or Other Identifying Number of Holder)

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
  Signature 

  	
   

  	
   

  
	
  Guaranteed

  	
   

  	
   

  	
   

  
	
   

  	
  Signature

  	
   

  	
   

  
						

 

 

(Signature must conform
in all respects to name of holder as specified on the face of this Warrant
Certificate and must bear a signature guarantee by a bank, trust company or
member broker of the New York, Midwest or Pacific Stock Exchange).

 

This Warrant may be
exercised at the following addresses:

 

	
  By hand 

  	
   

  	
   

  
	
  at

  	
   

  	
   

  
	
   

  	
   

  
	
   

  	
   

  
	
  By mail 

  	
   

  	
   

  
	
  at

  	
   

  	
   

  
	
   

  	
   

  
	
   

  	
   

  
	
  [Instructions as to
  form and delivery of Warrant Securities and, if applicable, Warrant
  Certificates evidencing Warrants for the number of Warrant Securities
  remaining unexercised—complete as appropriate.]

  

 

 

ASSIGNMENT

 

[Form of
assignment to be executed if Warrant Holder desires to transfer Warrant)

 

FOR VALUE
RECEIVED,                
hereby sells, assigns and transfers unto:

 

 

	
  (Please print name and
  address including zip code) 

  	
   

  	
  Please print Social
  Security or other identifying number

  

 

the right represented by
the within Warrant to purchase                        
shares of [Title of Warrant Securities] of Optimer Pharmaceuticals, Inc.
to which the within Warrant relates and appoints                       
attorney to transfer such right on the books of the Warrant Agent with full
power of substitution in the premises.

 

	
  Dated

  	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  	
   

  	
  Signature

  
					

(Signature must
conform in all respects to name of holder as specified on the face of the
Warrant)

 

	
  Signature GuaranteedEXHIBIT 4.12

 

OPTIMER PHARMACEUTICALS, INC.

and

                ,
AS WARRANT AGENT

FORM OF PREFERRED STOCK

WARRANT AGREEMENT

DATED AS OF               

 

 

OPTIMER PHARMACEUTICALS, INC.

 

FORM OF PREFERRED STOCK WARRANT AGREEMENT

 

     PREFERRED STOCK WARRANT AGREEMENT (this “Agreement”),
dated as of                
between OPTIMER PHARMACEUTICALS, INC.,
a Delaware corporation (the “Company”) and                ,
a [corporation] [national banking association] organized and existing under the
laws of                
and having a corporate trust office in                ,
as warrant agent (the “Warrant Agent”).

 

     WHEREAS, the Company proposes to sell [if
Warrants are sold with other securities - [title of such other securities being
offered] (the “Other Securities”) with] warrant certificates evidencing one or
more warrants (the “Warrants” or, individually, a “Warrant”) representing the
right to purchase [title of Preferred Stock purchasable through exercise of
Warrants] (the “Warrant Securities”), such warrant certificates and other
warrant certificates issued pursuant to this Agreement being herein called the “Warrant
Certificates”; and

 

     WHEREAS, the Company desires the Warrant
Agent to act on behalf of the Company, and the Warrant Agent is willing so to
act, in connection with the issuance, registration, transfer, exchange,
exercise and replacement of the Warrant Certificates, and in this Agreement
wishes to set forth, among other things, the form and provisions of the Warrant
Certificates and the terms and conditions on which they may be issued,
registered, transferred, exchanged, exercised and replaced.

 

     NOW THEREFORE, in consideration of the
premises and of the mutual agreements herein contained, the parties hereto
agree as follows:

 

ARTICLE 1

 

ISSUANCE OF WARRANTS AND EXECUTION AND DELIVERY OF
WARRANT CERTIFICATES

 

     1.1 Issuance of Warrants. [If Warrants
alone — Upon issuance, each Warrant Certificate shall evidence one or more
Warrants.] [If Other Securities and Warrants — Warrant Certificates shall be
[initially] issued in connection with the issuance of the Other Securities [but
shall be separately transferable on and after                                
(the “Detachable Date”)] [and shall not be separately transferable] and each
Warrant Certificate shall evidence one or more Warrants.] Each Warrant
evidenced thereby shall represent the right, subject to the provisions
contained herein and therein, to purchase one Warrant Security. [If Other
Securities and Warrants — Warrant Certificates shall be initially issued in
units with the Other Securities and each Warrant Certificate included in such a
unit shall evidence                
Warrants for each [$                  
principal amount] [           shares]
of Other Securities included in such unit.]

 

     1.2 Execution And Delivery Of Warrant Certificates. Each
Warrant Certificate, whenever issued, shall be in registered form substantially
in the form set forth in Exhibit A hereto, shall be dated the date of its
countersignature by the Warrant Agent and may have such letters, numbers, or
other marks of identification or designation and such legends or endorsements
printed, lithographed or engraved thereon as the officers of the Company
executing the same may approve (execution thereof to be conclusive evidence of
such approval) and as are not inconsistent with the provisions of this
Agreement, or as may be required to comply with any law or with any rule or
regulation made pursuant thereto or with any rule or regulation of any
securities exchange on which the Warrants may be listed, or to conform to
usage. The Warrant Certificates shall be signed on behalf of the Company by any
of its present or future chief executive officers, presidents, senior vice
presidents, vice presidents, chief financial officers, chief legal officers,
treasurers, assistant treasurers, controllers, assistant controllers,
secretaries or assistant secretaries under its corporate seal reproduced
thereon. Such signatures may be manual or facsimile signatures of such authorized
officers and may be imprinted or otherwise reproduced on the Warrant
Certificates. The seal of the Company may be in the form of a facsimile thereof
and may be impressed, affixed, imprinted or otherwise reproduced on the Warrant
Certificates.

 

 

     No
Warrant Certificate shall be valid for any purpose, and no Warrant evidenced
thereby shall be exercisable, until such Warrant Certificate has been
countersigned by the manual signature of the Warrant Agent. Such signature by
the Warrant Agent upon any Warrant Certificate executed by the Company shall be
conclusive evidence that the Warrant Certificate so countersigned has been duly
issued hereunder.

 

     In
case any officer of the Company who shall have signed any of the Warrant
Certificates either manually or by facsimile signature shall cease to be such
officer before the Warrant Certificates so signed shall have been countersigned
and delivered by the Warrant Agent, such Warrant Certificates may be
countersigned and delivered notwithstanding that the person who signed Warrant
Certificates ceased to be such officer of the Company; and any Warrant
Certificate may be signed on behalf of the Company by such persons as, at the
actual date of the execution of such Warrant Certificate, shall be the proper
officers of the Company, although at the date of the execution of this
Agreement any such person was not such officer.

 

     The
term “holder” or “holder of a Warrant Certificate” as used herein shall mean
any person in whose name at the time any Warrant Certificate shall be
registered upon the books to be maintained by the Warrant Agent for that
purpose [If Other Securities and Warrants are not immediately detachable—or
upon the registration of the Other Securities prior to the Detachable Date.
Prior to the Detachable Date, the Company will, or will cause the registrar of
the Other Securities to, make available at all times to the Warrant Agent such
information as to holders of the Other Securities as may be necessary to keep
the Warrant Agent’s records up to date].

 

     1.3 Issuance Of Warrant Certificates. Warrant
Certificates evidencing the right to purchase Warrant Securities may be
executed by the Company and delivered to the Warrant Agent upon the execution
of this Warrant Agreement or from time to time thereafter. The Warrant Agent
shall, upon receipt of Warrant Certificates duly executed on behalf of the
Company, countersign such Warrant Certificates and shall deliver such Warrant
Certificates to or upon the order of the Company.

 

ARTICLE 2

 

WARRANT PRICE, DURATION AND EXERCISE OF WARRANTS

 

     2.1 Warrant Price. During the period
specified in Section 2.2, each Warrant shall, subject to the terms of this
Warrant Agreement and the applicable Warrant Certificate, entitle the holder
thereof to purchase the number of Warrant Securities specified in the
applicable Warrant Certificate at an exercise price of $          
per Warrant Security, subject to adjustment upon the occurrence of certain
events, as hereinafter provided. Such purchase price per Warrant Security is
referred to in this Agreement as the “Warrant Price.”

 

     2.2 Duration Of Warrants. Each Warrant may
be exercised in whole or in part at any time, as specified herein, on or after
[the date thereof] [                    ]
and at or before [          ] p.m.,
[City] time, on                     
or such later date as the Company may designate by notice to the Warrant Agent
and the holders of Warrant Certificates mailed to their addresses as set forth
in the record books of the Warrant Agent (the “Expiration Date”). Each Warrant
not exercised at or before [          ] p.m.,
[City] time, on the Expiration Date shall become void, and all rights of the
holder of the Warrant Certificate evidencing such Warrant under this Agreement
shall cease.

 

     2.3 Exercise Of Warrants.

 

          (a) During the period specified in Section 2.2,
the Warrants may be exercised to purchase a whole number of Warrant Securities
in registered form by providing certain information as set forth on the reverse
side of the Warrant Certificate and by paying in full, in lawful money of the
United States of America, [in cash or by certified check or official bank check
in New York Clearing House funds] [by bank wire transfer in immediately
available funds] the Warrant Price for each Warrant Security with respect to
which a Warrant is being exercised to the Warrant Agent at its corporate trust
office, provided that such exercise is subject to receipt within five business
days of such payment by the Warrant Agent of the Warrant Certificate with the
form of election to purchase Warrant Securities set forth on the reverse side
of the Warrant Certificate properly completed and duly executed. The date on
which payment in full of the Warrant Price is received by the Warrant Agent
shall, subject to receipt of the Warrant Certificate as aforesaid, be deemed to
be the date on which the Warrant is exercised; provided, however, that if, at
the date of receipt of such 

 

 

Warrant
Certificates and payment in full of the Warrant Price, the transfer books for
the Warrant Securities purchasable upon the exercise of such Warrants shall be
closed, no such receipt of such Warrant Certificates and no such payment of
such Warrant Price shall be effective to constitute the person so designated to
be named as the holder of record of such Warrant Securities on such date, but
shall be effective to constitute such person as the holder of record of such
Warrant Securities for all purposes at the opening of business on the next
succeeding day on which the transfer books for the Warrant Securities
purchasable upon the exercise of such Warrants shall be opened, and the
certificates for the Warrant Securities in respect of which such Warrants are
then exercised shall be issuable as of the date on such next succeeding day on
which the transfer books shall next be opened, and until such date the Company
shall be under no duty to deliver any certificate for such Warrant Securities.
The Warrant Agent shall deposit all funds received by it in payment of the
Warrant Price in an account of the Company maintained with it and shall advise
the Company by telephone at the end of each day on which a payment for the
exercise of Warrants is received of the amount so deposited to its account. The
Warrant Agent shall promptly confirm such telephone advice to the Company in
writing.

 

          (b) The Warrant Agent shall, from time
to time, as promptly as practicable, advise the Company of (i) the number
of Warrant Securities with respect to which Warrants were exercised, (ii) the
instructions of each holder of the Warrant Certificates evidencing such
Warrants with respect to delivery of the Warrant Securities to which such
holder is entitled upon such exercise, (iii) delivery of Warrant
Certificates evidencing the balance, if any, of the Warrants for the remaining
Warrant Securities after such exercise, and (iv) such other information as
the Company shall reasonably require.

 

          (c) As soon as practicable after the
exercise of any Warrant, the Company shall issue to or upon the order of the
holder of the Warrant Certificate evidencing such Warrant the Warrant
Securities to which such holder is entitled, in fully registered form,
registered in such name or names as may be directed by such holder. If fewer
than all of the Warrants evidenced by such Warrant Certificate are exercised,
the Company shall execute, and an authorized officer of the Warrant Agent shall
manually countersign and deliver, a new Warrant Certificate evidencing Warrants
for the number of Warrant Securities remaining unexercised.

 

          (d) The Company shall not be required
to pay any stamp or other tax or other governmental charge required to be paid
in connection with any transfer involved in the issue of the Warrant
Securities, and in the event that any such transfer is involved, the Company
shall not be required to issue or deliver any Warrant Security until such tax
or other charge shall have been paid or it has been established to the Company’s
satisfaction that no such tax or other charge is due.

 

          (e) Prior to the issuance of any
Warrants there shall have been reserved, and the Company shall at all times
through the Expiration Date keep reserved, out of its authorized but unissued
Warrant Securities, a number of shares sufficient to provide for the exercise
of the Warrants.

 

ARTICLE 3

 

OTHER PROVISIONS RELATING TO RIGHTS OF HOLDERS OF
WARRANT CERTIFICATES

 

     3.1 No Rights As Warrant Securityholder Conferred By
Warrants or Warrant Certificates. No Warrant Certificate or Warrant
evidenced thereby shall entitle the holder thereof to any of the rights of a
holder of Warrant Securities, including, without limitation, the right to
receive the payment of dividends or distributions, if any, on the Warrant
Securities or to exercise any voting rights, except to the extent expressly set
forth in this Agreement or the applicable Warrant Certificate.

 

     3.2 Lost, Stolen, Mutilated or Destroyed Warrant
Certificates. Upon receipt by the Warrant Agent of evidence
reasonably satisfactory to it and the Company of the ownership of and the loss,
theft, destruction or mutilation of any Warrant Certificate and/or indemnity
reasonably satisfactory to the Warrant Agent and the Company and, in the case
of mutilation, upon surrender of the mutilated Warrant Certificate to the
Warrant Agent for cancellation, then, in the absence of notice to the Company
or the Warrant Agent that such Warrant Certificate has been acquired by a bona
fide purchaser, the Company shall execute, and an authorized officer of the
Warrant Agent shall manually countersign and deliver, in exchange for or in
lieu of the lost, stolen, destroyed or mutilated 

 

 

Warrant
Certificate, a new Warrant Certificate of the same tenor and evidencing
Warrants for a like number of Warrant Securities. Upon the issuance of any new
Warrant Certificate under this Section 3.2, the Company may require the
payment of a sum sufficient to cover any tax or other governmental charge that
may be imposed in relation thereto and any other expenses (including the fees
and expenses of the Warrant Agent) in connection therewith. Every substitute
Warrant Certificate executed and delivered pursuant to this Section 3.2 in
lieu of any lost, stolen or destroyed Warrant Certificate shall represent an
additional contractual obligation of the Company, whether or not the lost,
stolen or destroyed Warrant Certificate shall be at any time enforceable by
anyone, and shall be entitled to the benefits of this Agreement equally and
proportionately with any and all other Warrant Certificates duly executed and
delivered hereunder. The provisions of this Section 3.2 are exclusive and
shall preclude (to the extent lawful) all other rights and remedies with
respect to the replacement of mutilated, lost, stolen or destroyed Warrant
Certificates.

 

     3.3 Holder of Warrant Certificate May Enforce
Rights. Notwithstanding any of the provisions of this Agreement, any
holder of a Warrant Certificate, without the consent of the Warrant Agent, the
holder of any Warrant Securities or the holder of any other Warrant Certificate,
may, in such holder’s own behalf and for such holder’s own benefit, enforce,
and may institute and maintain any suit, action or proceeding against the
Company suitable to enforce, or otherwise in respect of, such holder’s right to
exercise the Warrants evidenced by such holder’s Warrant Certificate in the
manner provided in such holder’s Warrant Certificate and in this Agreement.

 

     3.4 Adjustments.

 

          (a) In case the Company shall at any
time subdivide its outstanding shares of [title of Preferred Stock purchasable
through exercise of Warrants] into a greater number of shares, the Warrant
Price in effect immediately prior to such subdivision shall be proportionately
reduced and the number of Warrant Securities purchasable under the Warrants
shall be proportionately increased. Conversely, in case the outstanding shares
of [title of Preferred Stock purchasable through exercise of Warrants] of the
Company shall be combined into a smaller number of shares, the Warrant Price in
effect immediately prior to such combination shall be proportionately increased
and the number of Warrant Securities purchasable under the Warrants shall be
proportionately decreased.

 

          (b) If at any time or from time to
time the holders of [title of Preferred Stock purchasable through exercise of
Warrants] (or any shares of stock or other securities at the time receivable
upon the exercise of the Warrants) shall have received or become entitled to
receive, without payment therefore,

 

               (i) [title of Preferred Stock
purchasable through exercise of Warrants] or any shares of stock or other
securities which are at any time directly or indirectly convertible into or
exchangeable for [title of Preferred Stock purchasable through exercise of
Warrants], or any rights or options to subscribe for, purchase or otherwise
acquire any of the foregoing by way of dividend or other distribution;

 

               (ii) any cash paid or payable
otherwise than in accordance with the terms of [title of Preferred Stock purchasable
through exercise of Warrants] or otherwise than as a cash dividend paid or
payable out of the Company’s current or retained earnings;

 

               (iii) any evidence of the Company’s
indebtedness or rights to subscribe for or purchase the Company’s indebtedness;
or

 

               (iv) [title of Preferred Stock
purchasable through exercise of Warrants] or additional stock or other
securities or property (including cash) by way of spinoff, split-up,
reclassification, combination of shares or similar corporate rearrangement
(other than shares of [title of Preferred Stock purchasable through exercise of
Warrants] issued as a stock split or adjustments in respect of which shall be
covered by the terms of Section 3.4(a) above), then and in each such
case, the holder of each Warrant shall, upon the exercise of the Warrant, be
entitled to receive, in addition to the number of Warrant Securities receivable
thereupon, and without payment of any additional consideration therefore, the
amount of stock and other securities and property (including cash and
indebtedness or rights to subscribe for or purchase indebtedness) which such
holder would hold on the date of such exercise had he been the holder of record
of such Warrant Securities as of the date on which holders of [title of
Preferred Stock purchasable through exercise of Warrants] received or became
entitled to receive such shares or all other additional stock and other
securities and property.

 

 

          (c) In case of (i) any
reclassification, capital reorganization, or change in the [title of Preferred
Stock purchasable through the exercise of the Warrants] of the Company (other
than as a result of a subdivision, combination or stock dividend provided for
in Section 3.4(a) or Section 3.4(b) above), (ii) share
exchange, merger or similar transaction of the Company with or into another
person or entity (other than a share exchange, merger or similar transaction in
which the Company is the acquiring or surviving corporation and which does not
result in any change in the [title of Preferred Stock purchasable through the
exercise of the Warrants] other than the issuance of additional shares of
[title of Preferred Stock purchasable through the exercise of the Warrants]) or
(iii) the sale, exchange, lease, transfer or other disposition of all or
substantially all of the properties and assets of the Company as an entirety
(in any such case, a “Reorganization Event”), then, as a condition of such
Reorganization Event, lawful provisions shall be made, and duly executed
documents evidencing the same from the Company or its successor shall be
delivered to the holders of the Warrants, so that the holders of the Warrants
shall have the right at any time prior to the expiration of the Warrants to
purchase, at a total price equal to that payable upon the exercise of the
Warrants, the kind and amount of shares of stock and other securities and
property receivable in connection with such Reorganization Event by a holder of
the same number of shares of [title of Preferred Stock purchasable through the
exercise of the Warrants] as were purchasable by the holders of the Warrants
immediately prior to such Reorganization Event. In any such case appropriate
provisions shall be made with respect to the rights and interests of the
holders of the Warrants so that the provisions hereof shall thereafter be
applicable with respect to any shares of stock or other securities and property
deliverable upon exercise the Warrants, and appropriate adjustments shall be
made to the Warrant Price payable hereunder provided the aggregate purchase
price shall remain the same. In the case of any transaction described in
clauses (ii) and (iii) above, the Company shall thereupon be relieved
of any further obligation hereunder or under the Warrants, and the Company as
the predecessor corporation may thereupon or at any time thereafter be
dissolved, wound up or liquidated. Such successor or assuming entity thereupon
may cause to be signed, and may issue either in its own name or in the name of
the Company, any or all of the Warrants issuable hereunder which heretofore
shall not have been signed by the Company, and may execute and deliver
securities in its own name, in fulfillment of its obligations to deliver
Warrant Securities upon exercise of the Warrants. All the Warrants so issued
shall in all respects have the same legal rank and benefit under this Agreement
as the Warrants theretofore or thereafter issued in accordance with the terms
of this Agreement as though all of such Warrants had been issued at the date of
the execution hereof. In any case of any such Reorganization Event, such
changes in phraseology and form (but not in substance) may be made in the
Warrants thereafter to be issued as may be appropriate.

 

     The
Warrant Agent may receive a written opinion of legal counsel as conclusive
evidence that any such Reorganization Event complies with the provisions of
this Section 3.4.

 

          (d) The Company may, at its option, at
any time until the Expiration Date, reduce the then current Warrant Price to
any amount deemed appropriate by the Board of Directors of the Company for any
period not exceeding twenty consecutive days (as evidenced in a resolution
adopted by such Board of Directors), but only upon giving the notices required
by Section 3.5 at least ten days prior to taking such action.

 

          (e) Except as herein otherwise
expressly provided, no adjustment in the Warrant Price shall be made by reason
of the issuance of any securities of the Company or for any other reason
whatsoever.

 

          (f) No fractional Warrant Securities
shall be issued upon the exercise of Warrants.  If more than one
Warrant shall be exercised at one time by the same holder, the number of full
Warrant Securities which shall be issuable upon such exercise shall be computed
on the basis of the aggregate number of Warrant Securities purchased pursuant
to the Warrants so exercised.  Instead of any fractional Warrant
Security which would otherwise be issuable upon exercise of any Warrant, the
Company shall pay a cash adjustment in respect of such fraction in an amount
equal to the same fraction of the last reported sale price (or bid price if
there were no sales) per Warrant Security, in either case as reported on the
principal registered national securities exchange on which the Warrant
Securities are listed or admitted to trading on the business day that next
precedes the day of exercise or, if the Warrant Securities are not then listed
or admitted to trading on any registered national securities exchange, the average
of the closing high bid and low asked prices as reported on the OTC Bulletin
Board Service (the “OTC Bulletin Board”)
operated by the Financial Industry Regulatory Authority, Inc. (“FINRA”) or, if not available on the
OTC Bulletin Board, then the average of the closing high bid and low asked
prices as reported on any other U.S. quotation medium or inter-dealer quotation
system on such date, or if on any such date the Warrant Securities are not
listed or admitted to trading on a registered national securities exchange, are
not included in the OTC Bulletin Board, and are not quoted on any other U.S.
quotation medium or inter-dealer quotation system, an amount equal to the same
fraction of the average of the closing bid and asked prices as furnished by any
FINRA member firm selected from time to time by the Company for that purpose at
the close of business on the business day that next precedes the day of
exercise.

 

 

          (g) Whenever the Warrant Price then in
effect is adjusted as herein provided, the Company shall mail to each holder of
the Warrants at such holder’s address as it shall appear on the books of the
Company a statement setting forth the adjusted Warrant Price then and
thereafter effective under the provisions hereof, together with the facts, in
reasonable detail, upon which such adjustment is based.

 

     3.5 Notice to Warrantholders. In case the
Company shall (a) effect any dividend or distribution described in Section 3.4(b),
(b) effect any Reorganization Event, (c) make any distribution on or
in respect of the [title of Preferred Stock purchasable through the exercise of
the Warrants] in connection with the dissolution, liquidation or winding up of
the Company, or (d) reduce the then current Warrant Price pursuant to Section 3.4(d),
then the Company shall mail to each holder of Warrants at such holder’s address
as it shall appear on the books of the Warrant Agent, at least ten days prior
to the applicable date hereinafter specified, a notice stating (x) the
record date for such dividend or distribution, or, if a record is not to be
taken, the date as of which the holders of record of [title of Preferred Stock
purchasable through the exercise of Warrants] that will be entitled to such
dividend or distribution are to be determined, (y) the date on which such
Reorganization Event, dissolution, liquidation or winding up is expected to
become effective, and the date as of which it is expected that holders of
[title of Preferred Stock purchasable through the exercise of the Warrants] of
record shall be entitled to exchange their shares of [title of Preferred Stock
purchasable through the exercise of the Warrants] for securities or other
property deliverable upon such Reorganization Event, dissolution, liquidation
or winding up, or (z) the first date on which the then current Warrant
Price shall be reduced pursuant to Section 3.4(d). No failure to mail such
notice nor any defect therein or in the mailing thereof shall affect any such
transaction or any adjustment in the Warrant Price required by Section 3.4.

 

     3.6 [IF THE WARRANTS ARE SUBJECT TO ACCELERATION BY
THE COMPANY, INSERT—ACCELERATION OF WARRANTS BY THE COMPANY.

 

          (a) At any time on or after                     ,
the Company shall have the right to accelerate any or all Warrants at any time
by causing them to expire at the close of business on the day next preceding a
specified date (the “Acceleration Date”), if the Market Price (as hereinafter
defined) of the [title of Preferred Stock purchasable through the exercise of
the Warrants] equals or exceeds                     
percent (          %) of the
then effective Warrant Price on any twenty Trading Days (as hereinafter
defined) within a period of thirty consecutive Trading Days ending no more than
five Trading Days prior to the date on which the Company gives notice to the
Warrant Agent of its election to accelerate the Warrants.

 

          (b) “Market Price” for each Trading Day shall be, if the Common Stock
is listed or admitted to trading on any registered national securities
exchange, the last reported sale price, regular way (or, if no such price is
reported, the average of the reported closing bid and asked prices, regular
way) of Common Stock, in either case as reported on the principal registered
national securities exchange on which the Common Stock is listed or admitted to
trading or, if not listed or admitted to trading on any registered national
securities exchange, the average of the closing high bid and low asked prices
as reported on the OTC Bulletin Board operated by FINRA, or if not available on
the OTC Bulletin Board, then the average of the closing high bid and low asked
prices as reported on any other U.S. quotation medium or inter-dealer quotation
system, or if on any such date the shares of Common Stock are not listed or
admitted to trading on a registered national securities exchange, are not
included in the OTC Bulletin Board, and are not quoted on any other U.S.
quotation medium or inter-dealer quotation system, the average of the closing
bid and asked prices as furnished by any FINRA member firm selected from time
to time by the Company for that purpose. “Trading Day” shall be each Monday through Friday, other than any
day on which securities are not traded in the system or on the exchange that is
the principal market for the Common Stock, as determined by the Board of
Directors of the Company.

 

          (c) In the event of an acceleration of
less than all of the Warrants, the Warrant Agent shall select the Warrants to
be accelerated by lot, pro rata or in such other manner as it deems, in its
discretion, to be fair and appropriate.

 

 

          (d) Notice of an acceleration
specifying the Acceleration Date shall be sent by mail first class, postage
prepaid, to each registered holder of a Warrant Certificate representing a
Warrant accelerated at such holder’s address appearing on the books of the
Warrant Agent not more than sixty days nor less than thirty days before the
Acceleration Date. Such notice of an acceleration also shall be given no more
than twenty days, and no less than ten days, prior to the mailing of notice to
registered holders of Warrants pursuant to this Section 3.6, by
publication at least once in a newspaper of general circulation in the City of
New York.

 

          (e) Any Warrant accelerated may be
exercised until [          ] p.m.,
[City] time, on the business day next preceding the Acceleration Date. The
Warrant Price shall be payable as provided in Section 2.]

 

ARTICLE 4

 

EXCHANGE AND TRANSFER OF WARRANT CERTIFICATES

 

     4.1 Exchange and Transfer of Warrant Certificates. [If
Other Securities with Warrants which are immediately detachable—Upon] [If Other
Securities with Warrants which are not immediately detachable—Prior to the
Detachable Date, a Warrant Certificate may be exchanged or transferred only
together with the Other Security to which the Warrant Certificate was initially
attached, and only for the purpose of effecting or in conjunction with an
exchange or transfer of such Other Security. Prior to any Detachable Date, each
transfer of the Other Security shall operate also to transfer the related
Warrant Certificates. After the Detachable Date, upon] surrender at the
corporate trust office of the Warrant Agent, Warrant Certificates evidencing
Warrants may be exchanged for Warrant Certificates in other denominations
evidencing such Warrants or the transfer thereof may be registered in whole or
in part; provided that such other Warrant Certificates evidence Warrants for
the same aggregate number of Warrant Securities as the Warrant Certificates so
surrendered. The Warrant Agent shall keep, at its corporate trust office, books
in which, subject to such reasonable regulations as it may prescribe, it shall
register Warrant Certificates and exchanges and transfers of outstanding Warrant
Certificates, upon surrender of the Warrant Certificates to the Warrant Agent
at its corporate trust office for exchange or registration of transfer,
properly endorsed or accompanied by appropriate instruments of registration of
transfer and written instructions for transfer, all in form satisfactory to the
Company and the Warrant Agent. No service charge shall be made for any exchange
or registration of transfer of Warrant Certificates, but the Company may
require payment of a sum sufficient to cover any stamp or other tax or other
governmental charge that may be imposed in connection with any such exchange or
registration of transfer. Whenever any Warrant Certificates are so surrendered
for exchange or registration of transfer, an authorized officer of the Warrant
Agent shall manually countersign and deliver to the person or persons entitled
thereto a Warrant Certificate or Warrant Certificates duly authorized and
executed by the Company, as so requested. The Warrant Agent shall not be
required to effect any exchange or registration of transfer which will result
in the issuance of a Warrant Certificate evidencing a Warrant for a fraction of
a Warrant Security or a number of Warrants for a whole number of Warrant
Securities and a fraction of a Warrant Security. All Warrant Certificates
issued upon any exchange or registration of transfer of Warrant Certificates
shall be the valid obligations of the Company, evidencing the same obligations
and entitled to the same benefits under this Agreement as the Warrant Certificate
surrendered for such exchange or registration of transfer.

 

     4.2 Treatment of Holders of Warrant Certificates. [If
Other Securities and Warrants are not immediately detachable—Prior to the
Detachable Date, the Company, the Warrant Agent and all other persons may treat
the owner of the Other Security as the owner of the Warrant Certificates
initially attached thereto for any purpose and as the person entitled to
exercise the rights represented by the Warrants evidenced by such Warrant Certificates,
any notice to the contrary notwithstanding. After the Detachable Date and prior
to due presentment of a Warrant Certificate for registration of transfer, the]
[The] Company, the Warrant Agent and all other persons may treat the registered
holder of a Warrant Certificate as the absolute owner thereof for any purpose
and as the person entitled to exercise the rights represented by the Warrants
evidenced thereby, any notice to the contrary notwithstanding.

 

     4.3 Cancellation of Warrant Certificates. Any
Warrant Certificate surrendered for exchange, registration of transfer or
exercise of the Warrants evidenced thereby shall, if surrendered to the
Company, be delivered to the Warrant Agent and all Warrant Certificates
surrendered or so delivered to the Warrant Agent shall be promptly canceled by
the Warrant Agent and shall not be reissued and, except as expressly permitted
by this Agreement, no Warrant Certificate shall be issued hereunder in exchange
therefor or in lieu thereof. The Warrant Agent shall 

 

 

deliver
to the Company from time to time or otherwise dispose of canceled Warrant
Certificates in a manner satisfactory to the Company.

 

ARTICLE 5

 

CONCERNING THE WARRANT AGENT

 

     5.1 Warrant Agent. The Company hereby
appoints                                 
as Warrant Agent of the Company in respect of the Warrants and the Warrant
Certificates upon the terms and subject to the conditions herein set forth, and
                               
hereby accepts such appointment. The Warrant Agent shall have the powers and
authority granted to and conferred upon it in the Warrant Certificates and
hereby and such further powers and authority to act on behalf of the Company as
the Company may hereafter grant to or confer upon it. All of the terms and provisions
with respect to such powers and authority contained in the Warrant Certificates
are subject to and governed by the terms and provisions hereof.

 

     5.2 Conditions of Warrant Agent’s Obligations. The
Warrant Agent accepts its obligations herein set forth upon the terms and
conditions hereof, including the following to all of which the Company agrees
and to all of which the rights hereunder of the holders from time to time of
the Warrant Certificates shall be subject:

 

          (a) Compensation and Indemnification. The
Company agrees promptly to pay the Warrant Agent the compensation to be agreed
upon with the Company for all services rendered by the Warrant Agent and to
reimburse the Warrant Agent for reasonable out-of-pocket expenses (including
reasonable counsel fees) incurred without negligence, bad faith or willful
misconduct by the Warrant Agent in connection with the services rendered
hereunder by the Warrant Agent. The Company also agrees to indemnify the
Warrant Agent for, and to hold it harmless against, any loss, liability or
expense incurred without negligence, bad faith or willful misconduct on the
part of the Warrant Agent, arising out of or in connection with its acting as
Warrant Agent hereunder, including the reasonable costs and expenses of
defending against any claim of such liability.

 

          (b) Agent for the Company. In acting
under this Warrant Agreement and in connection with the Warrant Certificates,
the Warrant Agent is acting solely as agent of the Company and does not assume
any obligations or relationship of agency or trust for or with any of the
holders of Warrant Certificates or beneficial owners of Warrants.

 

          (c) Counsel. The Warrant Agent may
consult with counsel satisfactory to it, which may include counsel for the
Company, and the written advice of such counsel shall be full and complete
authorization and protection in respect of any action taken, suffered or
omitted by it hereunder in good faith and in accordance with the advice of such
counsel.

 

          (d) Documents. The Warrant Agent shall
be protected and shall incur no liability for or in respect of any action taken
or omitted by it in reliance upon any Warrant Certificate, notice, direction,
consent, certificate, affidavit, statement or other paper or document
reasonably believed by it to be genuine and to have been presented or signed by
the proper parties.

 

          (e) Certain Transactions. The Warrant
Agent, and its officers, directors and employees, may become the owner of, or
acquire any interest in, Warrants, with the same rights that it or they would
have if it were not the Warrant Agent hereunder, and, to the extent permitted
by applicable law, it or they may engage or be interested in any financial or
other transaction with the Company and may act on, or as depositary, trustee or
agent for, any committee or body of holders of Warrant Securities or other
obligations of the Company as freely as if it were not the Warrant Agent
hereunder. Nothing in this Warrant Agreement shall be deemed to prevent the
Warrant Agent from acting as trustee under any indenture to which the Company
is a party.

 

          (f) No Liability for Interest. Unless
otherwise agreed with the Company, the Warrant Agent shall have no liability
for interest on any monies at any time received by it pursuant to any of the
provisions of this Agreement or of the Warrant Certificates.

 

 

          (g) No Liability for Invalidity. The
Warrant Agent shall have no liability with respect to any invalidity of this
Agreement or any of the Warrant Certificates (except as to the Warrant Agent’s
countersignature thereon).

 

          (h) No Responsibility for Representations. The
Warrant Agent shall not be responsible for any of the recitals or
representations herein or in the Warrant Certificates (except as to the Warrant
Agent’s countersignature thereon), all of which are made solely by the Company.

 

          (i) No Implied Obligations. The
Warrant Agent shall be obligated to perform only such duties as are herein and
in the Warrant Certificates specifically set forth and no implied duties or
obligations shall be read into this Agreement or the Warrant Certificates
against the Warrant Agent. The Warrant Agent shall not be under any obligation
to take any action hereunder which may tend to involve it in any expense or
liability, the payment of which within a reasonable time is not, in its
reasonable opinion, assured to it. The Warrant Agent shall not be accountable
or under any duty or responsibility for the use by the Company of any of the
Warrant Certificates authenticated by the Warrant Agent and delivered by it to
the Company pursuant to this Agreement or for the application by the Company of
the proceeds of the Warrant Certificates. The Warrant Agent shall have no duty
or responsibility in case of any default by the Company in the performance of
its covenants or agreements contained herein or in the Warrant Certificates or
in the case of the receipt of any written demand from a holder of a Warrant
Certificate with respect to such default, including, without limiting the
generality of the foregoing, any duty or responsibility to initiate or attempt
to initiate any proceedings at law or otherwise or, except as provided in Section 6.2
hereof, to make any demand upon the Company.

 

     5.3 Resignation, Removal and Appointment of
Successors.

 

          (a) The Company agrees, for the
benefit of the holders from time to time of the Warrant Certificates, that
there shall at all times be a Warrant Agent hereunder until all the Warrants
have been exercised or are no longer exercisable.

 

          (b) The Warrant Agent may at any time
resign as agent by giving written notice to the Company of such intention on
its part, specifying the date on which its desired resignation shall become
effective; provided that such date shall not be less than three months after
the date on which such notice is given unless the Company otherwise agrees. The
Warrant Agent hereunder may be removed at any time by the filing with it of an
instrument in writing signed by or on behalf of the Company and specifying such
removal and the intended date when it shall become effective. Such resignation
or removal shall take effect upon the appointment by the Company, as
hereinafter provided, of a successor Warrant Agent (which shall be a bank or
trust company authorized under the laws of the jurisdiction of its organization
to exercise corporate trust powers) and the acceptance of such appointment by
such successor Warrant Agent. The obligation of the Company under Section 5.2(a) shall
continue to the extent set forth therein notwithstanding the resignation or
removal of the Warrant Agent.

 

          (c) In case at any time the Warrant
Agent shall resign, or shall be removed, or shall become incapable of acting,
or shall be adjudged a bankrupt or insolvent, or shall commence a voluntary
case under the Federal bankruptcy laws, as now or hereafter constituted, or
under any other applicable Federal or state bankruptcy, insolvency or similar
law or shall consent to the appointment of or taking possession by a receiver,
custodian, liquidator, assignee, trustee, sequestrator (or other similar official)
of the Warrant Agent or its property or affairs, or shall make an assignment
for the benefit of creditors, or shall admit in writing its inability to pay
its debts generally as they become due, or shall take corporate action in
furtherance of any such action, or a decree or order for relief by a court
having jurisdiction in the premises shall have been entered in respect of the
Warrant Agent in an involuntary case under the Federal bankruptcy laws, as now
or hereafter constituted, or any other applicable Federal or state bankruptcy,
insolvency or similar law, or a decree or order by a court having jurisdiction
in the premises shall have been entered for the appointment of a receiver,
custodian, liquidator, assignee, trustee, sequestrator (or similar official) of
the Warrant Agent or of its property or affairs, or any public officer shall
take charge or control of the Warrant Agent or of its property or affairs for
the purpose of rehabilitation, conservation, winding up or liquidation, a
successor Warrant Agent, qualified as aforesaid, shall be appointed by the
Company by an instrument in writing, filed with the successor Warrant Agent.
Upon the appointment as aforesaid of a successor Warrant Agent and acceptance
by the successor Warrant Agent of such appointment, the Warrant Agent shall
cease to be Warrant Agent hereunder.

 

 

          (d) Any successor Warrant Agent
appointed hereunder shall execute, acknowledge and deliver to its predecessor
and to the Company an instrument accepting such appointment hereunder, and
thereupon such successor Warrant Agent, without any further act, deed or
conveyance, shall become vested with all the authority, rights, powers, trusts,
immunities, duties and obligations of such predecessor with like effect as if
originally named as Warrant Agent hereunder, and such predecessor, upon payment
of its charges and disbursements then unpaid, shall thereupon become obligated
to transfer, deliver and pay over, and such successor Warrant Agent shall be
entitled to receive, all monies, securities and other property on deposit with
or held by such predecessor, as Warrant Agent hereunder.

 

          (e) Any corporation into which the
Warrant Agent hereunder may be merged or converted or any corporation with
which the Warrant Agent may be consolidated, or any corporation resulting from
any merger, conversion or consolidation to which the Warrant Agent shall be a
party, or any corporation to which the Warrant Agent shall sell or otherwise
transfer all or substantially all the assets and business of the Warrant Agent,
provided that it shall be qualified as aforesaid, shall be the successor
Warrant Agent under this Agreement without the execution or filing of any paper
or any further act on the part of any of the parties hereto.

 

ARTICLE 6

 

MISCELLANEOUS

 

     6.1 Amendment. This Agreement may be
amended by the parties hereto, without the consent of the holder of any Warrant
Certificate, for the purpose of curing any ambiguity, or of curing, correcting
or supplementing any defective provision contained herein, or making any other
provisions with respect to matters or questions arising under this Agreement as
the Company and the Warrant Agent may deem necessary or desirable; provided
that such action shall not materially adversely affect the interests of the
holders of the Warrant Certificates.

 

     6.2 Notices and Demands to the Company and Warrant
Agent. If the Warrant Agent shall receive any notice or demand
addressed to the Company by the holder of a Warrant Certificate pursuant to the
provisions of the Warrant Certificates, the Warrant Agent shall promptly
forward such notice or demand to the Company.

 

     6.3 Addresses. Any communication from the
Company to the Warrant Agent with respect to this Agreement shall be addressed
to                                ,
Attention:                               
and any communication from the Warrant Agent to the Company with respect to
this Agreement shall be addressed to Optimer Pharmaceuticals, Inc., 10110
Sorrento Valley Road, Suite C, San Diego, California, 92121, Attention:
Corporate Secretary (or such other address as shall be specified in writing by
the Warrant Agent or by the Company).

 

     6.4 Governing Law. This Agreement and each
Warrant Certificate issued hereunder shall be governed by and construed in
accordance with the laws of the State of New York.

 

     6.5 Delivery of Prospectus. The Company
shall furnish to the Warrant Agent sufficient copies of a prospectus meeting
the requirements of the Securities Act of 1933, as amended, relating to the
Warrant Securities deliverable upon exercise of the Warrants (the “Prospectus”),
and the Warrant Agent agrees that upon the exercise of any Warrant, the Warrant
Agent will deliver to the holder of the Warrant Certificate evidencing such
Warrant, prior to or concurrently with the delivery of the Warrant Securities
issued upon such exercise, a Prospectus.

 

     The
Warrant Agent shall not, by reason of any such delivery, assume any
responsibility for the accuracy or adequacy of such Prospectus.

 

     6.6 Obtaining of Governmental Approvals. The
Company will from time to time take all action which may be necessary to obtain
and keep effective any and all permits, consents and approvals of governmental
agencies and authorities and securities act filings under United States Federal
and state laws (including without limitation a registration statement in
respect of the Warrants and Warrant Securities under the Securities Act of
1933, as amended), which may be or become requisite in connection with the
issuance, sale, transfer, and delivery of the Warrant Securities issued upon
exercise of the Warrants, the issuance, sale, transfer and delivery of the
Warrants or upon the expiration of the period during which the Warrants are
exercisable.

 

 

     6.7 Persons Having Rights Under Warrant Agreement. Nothing
in this Agreement shall give to any person other than the Company, the Warrant
Agent and the holders of the Warrant Certificates any right, remedy or claim
under or by reason of this Agreement.

 

     6.8 Headings. The descriptive headings of
the several Articles and Sections of this Agreement are inserted for
convenience only and shall not control or affect the meaning or construction of
any of the provisions hereof.

 

     6.9 Counterparts. This Agreement may be executed
in any number of counterparts, each of which as so executed shall be deemed to
be an original, but such counterparts shall together constitute but one and the
same instrument.

 

     6.10 Inspection of Agreement. A copy of
this Agreement shall be available at all reasonable times at the principal
corporate trust office of the Warrant Agent for inspection by the holder of any
Warrant Certificate. The Warrant Agent may require such holder to submit his
Warrant Certificate for inspection by it.

 

     IN WITNESS WHEREOF, the parties hereto have
caused this Agreement to be duly executed, all as of the day and year first
above written.

 

 

	
   

  	
  OPTIMER PHARMACEUTICALS, INC.

  
	
   

  	
   

  
	
   

  	
  By

  	
   

  
	
   

  	
   

  	
  Its

  	
   

  
	
   

  	
   

  
	
  Attest:

  	
   

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  Warrant
  Agent

  
	
   

  	
   

  
	
   

  	
  By

  	
   

  
	
   

  	
   

  	
  Its

  	
   

  
	
   

  	
   

  
	
  Attest:

  	
   

  

 

 

[SIGNATURE
PAGE TO PREFERRED STOCK WARRANT AGREEMENT]

 

 

EXHIBIT A

 

FORM OF WARRANT CERTIFICATE

[FACE OF WARRANT CERTIFICATE]

 

	
   

  	
   

  	
   

  
	
  [[Form if
  Warrants are attached to Other Securities and are not immediately
  detachable.] 

  	
   

  	
  [Prior
  to                     ,this Warrant Certificate cannot be transferred or exchanged unless
  attached to a [Title of Other Securities].]

  
	
   

  	
   

  	
   

  
	
  [Form of
  Legend if Warrants are not immediately exercisable.] 

  	
   

  	
  [Prior
  to                     ,
  Warrants evidenced by this Warrant Certificate cannot be exercised.]

  

 

EXERCISABLE ONLY IF COUNTERSIGNED BY THE WARRANT AGENT AS PROVIDED
HEREIN

VOID AFTER [          ] P.M.,
[CITY] TIME, ON                      ,

 

 

OPTIMER PHARMACEUTICALS, INC.

 

WARRANT CERTIFICATE REPRESENTING

WARRANTS TO PURCHASE

 

[TITLE OF WARRANT SECURITIES]

 

	
  No.               
  

  	
   

  	
  Warrants

  

 

     This
certifies that                
or registered assigns is the registered owner of the above indicated number of
Warrants, each Warrant entitling such owner [if Warrants are attached to Other
Securities and are not immediately detachable—, subject to the registered owner
qualifying as a “Holder” of this Warrant Certificate, as hereinafter defined),]
to purchase, at any time [after [          ] p.m.,
[City] time, on                             
and] on or before [          ] p.m.,
[City] time, on                               shares
of [Title of Warrant Securities] (the “Warrant Securities”), of Optimer
Pharmaceuticals, Inc. (the “Company”) on the following basis: during the
period from                ,
through and including                ,
the exercise price per Warrant Security will be $                  , 
subject to adjustment as provided in the Warrant Agreement (as hereinafter
defined) (the “Warrant Price”). The Holder may exercise the Warrants evidenced
hereby by providing certain information set forth on the back hereof and by
paying in full, in lawful money of the United States of America, [in cash or by
certified check or official bank check in New York Clearing House funds] [by
bank wire transfer in immediately available funds], the Warrant Price for each
Warrant Security with respect to which this Warrant is exercised to the Warrant
Agent (as hereinafter defined) and by surrendering this Warrant Certificate,
with the purchase form on the back hereof duly executed, at the corporate trust
office of [name of Warrant Agent], or its successor as warrant agent (the “Warrant
Agent”), which is, on the date hereof, at the address specified on the reverse
hereof, and upon compliance with and subject to the conditions set forth herein
and in the Warrant Agreement (as hereinafter defined).

 

     The
term “Holder” as used herein shall mean [if Warrants are attached to Other
Securities and are not immediately detachable—prior to                (the
“Detachable Date”), the registered owner of the Company’s [title of Other
Securities] to which this Warrant Certificate was initially attached, and after
such Detachable Date,] the person in whose name at the time this Warrant
Certificate shall be registered upon the books to be maintained by the Warrant
Agent for that purpose pursuant to Section 4 of the Warrant Agreement.

 

     The
Warrants evidenced by this Warrant Certificate may be exercised to purchase a
whole number of Warrant Securities in registered form. Upon any exercise of
fewer than all of the Warrants evidenced by this Warrant Certificate, there
shall be issued to the Holder hereof a new Warrant Certificate evidencing
Warrants for the number of Warrant Securities remaining unexercised.

 

     This
Warrant Certificate is issued under and in accordance with the Warrant
Agreement dated as of                ,
          (the “Warrant
Agreement”), between the Company and the Warrant Agent and is subject to the
terms and provisions contained in the Warrant Agreement, to all of which terms
and provisions the Holder of this Warrant Certificate consents by acceptance
hereof. Copies of the Warrant Agreement are on file at the above-mentioned
office of the Warrant Agent.

 

     [If
Warrants are attached to Other Securities and are not immediately detachable —
Prior to the Detachable Date, this Warrant Certificate may be exchanged or
transferred only together with the [Title of Other Securities] (the “Other
Securities”) to which this Warrant Certificate was initially attached, and only
for the purpose of effecting or in conjunction with, an exchange or transfer of
such Other Security. Additionally, on or prior to the Detachable Date, each
transfer of such Other Security on the register of the Other Securities shall
operate also to transfer this Warrant Certificate. After such date, transfer of
this] [If Warrants are attached to Other Securities and are immediately
detachable — Transfer of this] Warrant Certificate may be registered when this
Warrant Certificate is surrendered at the corporate trust office of the Warrant
Agent by the registered owner or such owner’s assigns, in the manner and
subject to the limitations provided in the Warrant Agreement.

 

 

     [If
Other Securities with Warrants which are not immediately detachable — Except as
provided in the immediately preceding paragraph, after] [If Other Securities
with Warrants which are immediately detachable or Warrants alone — After]
countersignature by the Warrant Agent and prior to the expiration of this
Warrant Certificate, this Warrant Certificate may be exchanged at the corporate
trust office of the Warrant Agent for Warrant Certificates representing
Warrants for the same aggregate number of Warrant Securities.

 

     This
Warrant Certificate shall not entitle the Holder hereof to any of the rights of
a holder of the Warrant Securities, including, without limitation, the right to
receive payments of dividends or distributions, if any, on the Warrant
Securities (except to the extent set forth in the Warrant Agreement) or to
exercise any voting rights.

 

     Reference
is hereby made to the further provisions of this Warrant Certificate set forth
on the reverse hereof, which further provisions shall for all purposes have the
same effect as if set forth at this place.

 

     This
Warrant Certificate shall not be valid or obligatory for any purpose until
countersigned by the Warrant Agent.

 

     IN WITNESS WHEREOF, the Company has caused
this Warrant to be executed in its name and on its behalf by the facsimile
signatures of its duly authorized officers.

 

	
  Dated:

  	
   

  
	
   

  	
   

  
	
   

  	
  OPTIMER PHARMACEUTICALS, INC.

  
	
   

  	
   

  
	
   

  	
  By

  	
   

  
	
   

  	
   

  	
  Its

  	
   

  
	
  Attest:

  	
   

  
	
   

  	
   

  
	
   

  	
  Countersigned:
  

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  As
  Warrant Agent

  
	
   

  	
   

  
	
   

  	
  By

  	
   

  
	
   

  	
         Authorized
  Signature

  

 

 

[REVERSE OF WARRANT CERTIFICATE]

 

(Instructions for Exercise of Warrant)

 

     To
exercise any Warrants evidenced hereby for Warrant Securities (as hereinafter
defined), the Holder must pay, in lawful money of the United States of America,
[in cash or by certified check or official bank check in New York Clearing
House funds] [by bank wire transfer in immediately available funds], the
Warrant Price in full for Warrants exercised, to [Warrant Agent] [address of
Warrant Agent], Attn:                ,
which payment must specify the name of the Holder and the number of Warrants
exercised by such Holder. In addition, the Holder must complete the information
required below and present this Warrant Certificate in person or by mail
(certified or registered mail is recommended) to the Warrant Agent at the appropriate
address set forth above. This Warrant Certificate, completed and duly executed,
must be received by the Warrant Agent within five business days of the payment.

 

(To be executed upon exercise of Warrants)

 

     The
undersigned hereby irrevocably elects to exercise                
Warrants, evidenced by this Warrant Certificate, to purchase                 shares
of the [Title of Warrant Securities] (the “Warrant Securities”), of Optimer
Pharmaceuticals, Inc. and represents that he has tendered payment for such
Warrant Securities, in lawful money of the United States of America, [in cash
or by certified check or official bank check in New York Clearing House funds]
[by bank wire transfer in immediately available funds], to the order of Optimer
Pharmaceuticals, Inc., c/o [insert name and address of Warrant Agent], in
the amount of $           in
accordance with the terms hereof. The undersigned requests that said Warrant
Securities be in fully registered form in the authorized denominations,
registered in such names and delivered all as specified in accordance with the
instructions set forth below.

 

     If
the number of Warrants exercised is less than all of the Warrants evidenced
hereby, the undersigned requests that a new Warrant Certificate evidencing the
Warrants for the number of Warrant Securities remaining unexercised be issued
and delivered to the undersigned unless otherwise specified in the instructions
below.

 

	
  Dated

  	
   

  	
   

  	
  Name

  	
   

  
	
   

  	
  Please Print

  
	
   

  	
   

  
	
  Address:

  	
                                                                                   

  	
   

  	
   

  
	
   

  	
   

  
	
   

  	
   

  	
   

  
	
  (Insert
  Social Security or Other Identifying Number of Holder)

  	
   

  
	
   

  
	
  Signature
  Guaranteed

  	
   

  	
   

  
	
   

  	
  Signature

  	
   

  
								

 

(Signature
must conform in all respects to name of holder as specified on the face of this
Warrant Certificate and must bear a signature guarantee by a bank, trust
company or member broker of the New York, Midwest or Pacific Stock Exchange).

 

This
Warrant may be exercised at the following addresses:

 

	
  By
  hand at

  	
   

  	
   

  
	
   

  	
   

  
	
   

  	
   

  
	
  By
  mail at

  	
   

  	
   

  
	
   

  	
   

  
	
   

  	
   

  
	
  [Instructions
  as to form and delivery of Warrant Securities and, if applicable, Warrant
  Certificates evidencing Warrants for the number of Warrant Securities
  remaining unexercised—complete as appropriate.]

  

 

 

ASSIGNMENT

 

[Form of assignment to be executed if Warrant Holder desires to
transfer Warrant)

 

FOR VALUE RECEIVED,                     
hereby sells, assigns and transfers unto:

 

	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
  (Please
  print name and address including zip code)

  	
   

  	
  Please
  print Social Security or other identifying 

  number

  

 

the
right represented by the within Warrant to purchase                                    shares
of [Title of Warrant Securities] of Optimer Pharmaceuticals, Inc. to which
the within Warrant relates and appoints                                   
attorney to transfer such right on the books of the Warrant Agent with full
power of substitution in the premises.

 

	
  Dated

  	
   

  	
   

  	
   

  
	
   

  	
  Signature

  

 

(Signature
must conform in all respects to name of holder as specified on the face of the
Warrant)

 

	
  Signature
  Guaranteed

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