Document:

EXHIBIT 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 sales price (or bid price if there were no sales) per Warrant
Security, in either case as reported on the New York Stock Exchange Composite
Tape on the business day which next precedes the day of exercise or, if the
Warrant Securities are not then listed or admitted to trading on the New York
Stock Exchange, on the principal national securities exchange on which the
Warrant Securities are listed or admitted to trading or, if not listed or
admitted to trading on any national securities exchange, the average of the
closing high bid and low asked prices in the over-the-counter market, as
reported by The Nasdaq Stock Market, Inc. (“NASDAQ”) or the Financial
Industry Regulatory Authority, Inc. (“FINRA”), as applicable, or such
other system then in use, or if on any such date the Warrant Securities are not
quoted by any such organization, an amount equal to the same fraction of the
average of the closing bid and asked prices as furnished by any New York Stock
Exchange firm selected from time to time by the Company for that purpose at the
close of business on the business day which 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 [title of Preferred Stock purchasable through the exercise
of the Warrants] is listed or admitted for trading on the New York Stock
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 [title of Preferred Stock purchasable through the exercise of the
Warrants], in either case as reported on the New York Stock Exchange Composite
Tape or, if the [title of Preferred Stock purchasable through the exercise of
the Warrants] is not listed or admitted to trading on the New York Stock
Exchange, on the principal national securities exchange on which the [title of
Preferred Stock purchasable through the exercise of the Warrants] is listed or
admitted to trading or, if not listed or admitted to trading on any national
securities exchange, the average of the closing high bid and low asked prices
in the over-the-counter market, as reported by NASDAQ or FINRA, as applicable,
or such other system then in use, or if on any such date the shares of [title
of Preferred Stock purchasable through the exercise of the Warrants] are not
quoted by any such organization, the average of the closing bid and asked
prices as furnished by any New York Stock Exchange 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 [title of
Preferred Stock purchasable through the exercise of the Warrants], 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
  GuaranteedEXHIBIT 4.13

 

OPTIMER PHARMACEUTICALS, INC.

and

            ,
AS WARRANT AGENT

FORM OF DEBT SECURITIES

WARRANT AGREEMENT

DATED AS OF            

 

 

OPTIMER PHARMACEUTICALS, INC.

 

FORM OF DEBT SECURITIES WARRANT AGREEMENT

 

DEBT SECURITIES 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 has entered into an indenture dated as of [                       
(the “Senior Indenture”), with                        ,
as trustee (such trustee, and any successors to such trustee, herein called the
“Senior Trustee”), providing for the issuance from time to time of its
unsubordinated debt securities, to be issued in one or more series as provided
in the Senior Indenture (the “Debt Securities”);] [                    (the
“Subordinated Indenture”), with                     ,
as trustee (such trustee, and any successors to such trustee, herein called the
“Subordinated Trustee”), providing for the issuance from time to time of its
subordinated debt securities, to be issued in one or more series as provided in
the Subordinated Indenture (the “Debt Securities”);]

 

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 Debt
Securities purchasable through exercise of Warrants] (the “Warrant Debt
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 Debt 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 Debt 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
principal amount of Warrant Debt Securities specified in the applicable Warrant
Certificate at an exercise price of                     %
of the principal amount thereof [plus accrued amortization, if any, of the
original issue discount of the Warrant Debt Securities] [plus accrued interest,
if any, from the most recent date from which interest shall have been paid on
the Warrant Debt Securities or, if no interest shall have been paid on the
Warrant Debt Securities, from the date of their initial issuance.] [The original
issue discount
($                
for each $1,000 principal amount of Warrant Debt Securities) will be amortized
at a                     %
annual rate, computed on a[n] [semi-] annual basis [using a 360-day year
consisting of twelve 30-day months].] Such purchase price for the Warrant Debt
Securities 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 Debt 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 Debt 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 Debt 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 Debt 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 Debt Securities on such date, but shall be effective to constitute such
person as the holder of record of such Warrant Debt Securities for all purposes
at the opening of business on the next succeeding day on which the transfer
books for the Warrant Debt Securities purchasable upon the exercise of such
Warrants shall be opened, and the certificates for the Warrant Debt 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 Debt 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 Debt 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 Debt 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 Debt Securities after such
exercise, and (iv) such other information as the Company or the [Senior]
[Subordinated] Trustee shall reasonably require.

 

(c) As soon as practicable after the exercise of any Warrant, the Company
shall issue, pursuant to the Indenture, in authorized denominations, to or upon
the order of the holder of the Warrant Certificate evidencing such Warrant, the
Warrant Debt 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 Debt 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 Debt Securities, and in the event that any
such transfer is involved, the Company shall not be required to issue or deliver
any Warrant Debt Securities 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 Debt 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 Holders of Warrant Debt Securities
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 Debt Securities, including, without limitation, the right to receive
the payment of principal of (or premium, if any) or interest, if any, on the
Warrant Debt Securities or to enforce any of the covenants in the Indenture.

 

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 principal amount of Warrant Debt
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 any Warrant Certificate,
without the consent of the Warrant Agent, the [Senior] [Subordinated] Trustee,
the holder of any Warrant Debt 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 Certificates and in
this Agreement.

 

3.4 Merger, Sale, Conveyance or Lease. In case of (a) any 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) or (b) 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’s
successor shall be delivered to the holders of the Warrants, so that such
successor shall succeed to and be substituted for the Company, and assume all
the Company’s obligations under, this Agreement and the Warrants. 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 Debt 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.

 

3.5 Notice To Warrantholders. In case the Company shall (a) effect any
Reorganization Event or (b) make any distribution on or in respect of the
[title of Warrant Debt Securities] in connection with the dissolution,
liquidation or winding up of the Company, 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 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 Warrant Debt
Securities] of record shall be entitled to exchange their shares of [title of
Warrant Debt Securities] for securities or other property deliverable upon such
Reorganization Event, dissolution, liquidation or winding up. No failure to
mail such notice nor any defect therein or in the mailing thereof shall affect
any such transaction.

 

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 principal amount of
Warrant Debt 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 Debt
Security or a number of Warrants for a whole number of Warrant Debt Securities
and a fraction of a Warrant Debt 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 Debt 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 [Senior] [Subordinated] Trustee under the [Senior] [Subordinated] Indenture.

 

 

(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 Debt 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 Debt 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 Debt
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 Debt 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 DEBT SECURITIES 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 DEBT 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                     ,
$                
principal amount of [Title of Warrant Debt Securities] (the “Warrant Debt
Securities”), of Optimer Pharmaceuticals, Inc. (the “Company”), issued or
to be issued under the Indenture (as hereinafter defined), on the following
basis: during the period from                     
        , through and including                     ,
each Warrant shall entitle the Holder thereof, subject to the provisions of
this Agreement, to purchase the principal amount of Warrant Debt Securities
stated in the Warrant Certificate at the warrant price (the “Warrant Price”) of
                    %
of the principal amount thereof [plus accrued amortization, if any, of the
original issue discount of the Warrant Debt Securities] [plus accrued interest,
if any, from the most recent date from which interest shall have been paid on
the Warrant Debt Securities or, if no interest shall have been paid on the
Warrant Debt Securities, from the date of their original issuance]. [The
original issue discount
($             for
each $1,000 principal amount of Warrant Debt Securities) will be amortized at a
                    %
annual rate, computed on a[n] [semi-]annual basis [using a 360-day year
consisting of twelve 30-day months]. 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 Debt 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
Warrant Debt Securities in the principal amount of $1,000 or any integral
multiple thereof 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 aggregate
principal amount of Warrant Debt 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.

 

 

The
Warrant Debt Securities to be issued and delivered upon the exercise of
Warrants evidenced by this Warrant Certificate will be issued under and in
accordance with an Indenture, [dated as of                     ,
                    (the
“Senior Indenture”), between the Company and                     ,
as trustee (such trustee, and any successors to such trustee, the “Senior
Trustee”)] [dated as of                     ,
                    ,
(the “Subordinated Indenture”), between the Company and                     
, as trustee (such trustee, and any successors to such trustee, the “Subordinated
Trustee”)] and will be subject to the terms and provisions contained in the
Warrant Debt Securities and in the Indenture. Copies of the [Senior]
[Subordinated] Indenture, including the form of the Warrant Debt Securities,
are on file at the corporate trust office of the Trustee.

 

[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 principal amount of Warrant Debt Securities.

 

This
Warrant Certificate shall not entitle the Holder hereof to any of the rights of
a holder of the Warrant Debt Securities, including, without limitation, the
right to receive payments of principal of (and premium, if any) or interest, if
any, on the Warrant Debt Securities or to enforce any of the covenants of the
Indenture.

 

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 Debt 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, represented by this Warrant Certificate, to purchase
$            
principal amount of the [Title of Warrant Debt Securities] (the “Warrant Debt
Securities”) of Optimer Pharmaceuticals, Inc. and represents that he has
tendered payment for such Warrant Debt 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 principal
amount of Warrant Debt 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 the Warrants evidenced
hereby, the undersigned requests that a new Warrant Certificate evidencing the
Warrants for the aggregate principal amount of Warrant Debt 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 Debt Securities and, if applicable, Warrant
Certificates evidencing Warrants for the number of Warrant Debt 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 $                      aggregate principal amount of [Title of Warrant Debt 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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