8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of

The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported)

May 5, 2010

OPTIMER PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

Delaware	001-33291	33-0830300
(State or other jurisdiction of	(Commission File Number)	(IRS Employer
incorporation)		Identification No.)

10110 Sorrento Valley Road, Suite C

San Diego, CA  92121

(Address of principal executive offices, including zip code)

(858) 909-0736

(Registrant’s telephone number, including area code)

N/A

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

oWritten communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

oSoliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

oPre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

oPre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 1.01Entry into a Material Definitive Agreement.

The disclosures in Item 5.02 below relating to the Offer Letter, the Consulting Agreement and the Amended Severance Plan are hereby incorporated by reference into this Item 1.01.

Item 1.02Termination of a Material Definitive Agreement.

The disclosures in Item 5.02 below relating to the termination of Dr. Chang’s employment agreement are hereby incorporated by reference into this Item 1.02.

Item 5.02Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On May 5, 2010, our board of directors appointed Mr. Pedro Lichtinger as our President and Chief Executive Officer.  Mr. Lichtinger was also appointed as a member of our board of directors, to serve as a Class II director who’s term will expire at the 2012 Annual Meeting of Stockholders.

Mr. Lichtinger, age 55, previously served as an executive of Pfizer, Inc. from 1995 to 2009, most recently as President of Pfizer’s Global Primary Care Business Unit, where he oversaw operations in North America, Europe, Korea, and Australia.  Prior to this position, he served as Pfizer’s Area President in Europe overseeing all pharmaceutical products including primary care, oncology, specialty and generic.  Prior to this position he served as Pfizer’s President of Global Animal Health Business, and Regional President Europe Animal Health.  Before joining Pfizer, he was an executive of Smith Kline Beecham, last serving as Senior Vice President Europe Animal Health.  Mr. Lichtinger holds an MBA degree from the Wharton School of Business and an Industrial Engineering degree from the National University of Mexico. Mr. Lichtinger currently serves on the board of directors of BioTime, Inc., a publicly-traded biotechnology company focused on blood plasma volume expanders and regenerative medicine. Mr. Lichtinger’s demonstrated leadership in the pharmaceutical field, including development and commercialization activities and his prior senior management experience, as well as his new role as President and Chief Executive Officer of Optimer, contributed to our board of directors’ conclusion that he should serve as a director.

In connection with his appointment as our President and Chief Executive Officer, Mr. Lichtinger entered into an offer letter (the “Offer Letter”) detailing the terms of his employment.  Pursuant to the Offer Letter, as compensation for his service as our President and Chief Executive Officer, Mr. Lichtinger will be entitled to receive (i) a base salary of $450,000 per year, subject to annual adjustments, (ii) a signing bonus of $100,000, (iii) an initial stock option to purchase up to 200,000 shares of our common stock which vests over four years from Mr. Lichtinger’s start date and (iv) additional stock options and restricted stock units to purchase up to an aggregate of 480,000 and 120,000 shares of our common stock, respectively, which vest over time beginning on the dates we achieve specified development and commercialization goals.  As an executive officer, Mr. Lichtinger will be eligible to participate in our 2006 Equity Incentive Plan (“Equity Incentive Plan”), our 2010 Incentive Compensation Plan and the Amended Severance Plan (defined below).   Mr. Lichtinger also entered into our standard form of indemnification agreement.  Pursuant to the Offer Letter, unless earlier terminated by us as provided below, the initial term of Mr. Lichtinger’s employment as our President and Chief Executive Officer will be three years with automatic one-year renewal terms unless we or Mr. Lichtinger provide notice of non-renewal.  In addition, we may terminate Mr. Lichtinger’s employment early for cause or without cause; provided, that in the event Mr. Lichtinger’s employment is terminated without cause or in a constructive termination, he may be eligible to receive severance payments in addition to those set forth in the Amended Severance Plan.  A copy of the Offer Letter is attached as Exhibit 99.1 hereto.

Simultaneously with Mr. Lichtinger’s appointment, Dr. Michael Chang resigned as our President and Chief Executive Officer.  In connection with his resignation, Dr. Chang’s employment agreement with us, dated June 17, 2005, as amended, was terminated, and Dr. Chang entered into a separation and consulting agreement with us (the “Consulting Agreement”), pursuant to which Dr. Chang will provide  general consulting services to us in exchange for compensation in the form of consulting fees and stock options to purchase up to an aggregate of 400,000 shares of our common stock, which vest over time beginning on the dates certain regulatory filings are accepted and approved.  In addition, Dr. Chang will continue to serve as a member of our board of directors as Chairman in exchange for compensation in the form of an annual cash stipend and equity awards.  The Consulting Agreement will continue in effect for 5 years unless earlier terminated by us or Dr. Chang for material breach.  Dr. Chang will continue to be eligible for stock option grants under our Equity Incentive Plan.  A copy of the Consulting Agreement is attached as Exhibit 99.2 hereto.

Also on May 5, 2010, Dr. Alain B. Schreiber, M.D. resigned as a member of our board of directors.  In connection with Dr. Schreiber’s resignation, Dr. Robert L. Zerbe was appointed to the Audit Committee of our board of directors and Joseph Y. Chang, Ph.D. was appointed as our Lead Independent Director.

On May 5, 2010, we also amended our Severance Benefit Plan (the “Amended Severance Plan”) to, among other things, provide that certain eligible employees who resign in a constructive termination will be entitled to benefits, provide for limited vesting acceleration of performance-based equity awards, and lower the requirement to receive enhanced benefits under the plan from three years of service to one year of service.  A copy of the Amended Severance Plan is attached as Exhibit 99.3 hereto.

On May 6, 2010, we issued a press release describing Mr. Lichtinger’s appointment as our President and Chief Executive Officer and Dr. Chang’s transition to a consultant and the Chairman of our board of directors.  A copy of this press release is attached as Exhibit 99.4 hereto.

The foregoing descriptions of the Offer Letter, the Consulting Agreement and the Amended Severance Plan do not purport to be complete and are qualified in their entirety by reference to the full text of those documents attached hereto.

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Item 9.01 Financial Statements and Exhibits.

(d)  Exhibits.

Exhibit No.	Description
99.1	Offer Letter, dated May 5, 2010, by and between Mr. Pedro Lichtinger and Optimer Pharmaceuticals, Inc.
99.2	Separation and Consulting Agreement, dated May 5, 2010, by and between Dr. Michael Chang and Optimer Pharmaceuticals, Inc.
99.3	Optimer Pharmaceuticals, Inc. Amended and Restated Severance Benefit Plan
99.4	Press release dated May 6, 2010

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	OPTIMER PHARMACEUTICALS, INC.
By:	/s/ John D. Prunty
	John D. Prunty
	Chief Financial Officer (Duly Authorized Officer and Principal Financial and Accounting Officer)

Date:  May 6, 2010

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EX-99.1

Exhibit 99.1

Date:       May 5, 2010

To:          Pedro Lichtinger

Dear Pedro:

Optimer Pharmaceuticals, Inc. (the “Company”) is pleased to offer you the position of President and Chief Executive Officer of the Company on the following terms.  Your employment with the Company would be expected to commence on May 5, 2010 (the “Start Date”).

1.You will be responsible for all services, acts or things necessary or advisable to manage and conduct the business of the Company and which are normally associated with the position of President and Chief Executive Officer, consistent with the bylaws of the Company and as required by the Board of Directors of the Company (the “Board”).  It is also anticipated that you will be elected to the Board as a director in connection with your appointment as President and Chief Executive Officer.  During the term of your employment, you will devote your full business energies, interest, abilities and productive time to the proper and efficient performance of your duties as President and Chief Executive Officer, provided that you may spend up to an aggregate of 15% of your productive time to service on boards of directors of up to three other companies, provided further that no such other companies shall be competitors or reasonably likely to become competitors of the Company.

2.Your base salary will be $450,000 per year, less payroll deductions and all required withholdings payable in regular periodic payments in accordance with Company policy.  Such base salary will be prorated for any partial year of employment on the basis of a 365-day fiscal year.  You will also be eligible for standard Company benefits relating to health insurance, vacation time and sick leave as set forth in the Company’s employee handbook and benefits summary.

3.On the first regular payroll date following the Start Date, you will receive $100,000 as a signing bonus.

4.In addition to your base salary, you will be eligible to participate in the Company’s 2010 Incentive Compensation Plan or such other similar discretionary performance bonus plans or programs for Company executives as may be provided from time to time by the Company, subject to the terms and conditions of such plans or programs.  Your target bonus under the Company’s 2010 Incentive Compensation Plan will be 50% of your annual base salary, pro-rated to the Start Date as provided in such plan.

5.Upon the commencement of your employment and subject to approval of the Board and the terms of the Company’s 2006 Equity Incentive Plan (the “Equity Incentive Plan”), you will be granted a stock option under the Equity Incentive Plan to purchase 200,000 shares of the Company’s Common Stock (the “Initial Option”).  The vesting commencement date of the Initial Option will be the Start Date and the Initial Option will be subject to Standard Vesting.  As used in this letter agreement with respect to any equity award described herein, “Standard Vesting” shall mean that 25% of the shares subject to the award vest on the one year anniversary of the applicable vesting commencement date and 1/36 of the remaining shares subject to the award vest monthly thereafter, in each case subject to you continuing to be a Service Provider (as defined in the Equity Incentive Plan) on the applicable vesting dates.  In addition, you will be eligible to receive future options under the Equity Incentive Plan to purchase shares of the Company’s Common Stock as may be determined by the Board and/or its Compensation Committee, in their sole discretion.

6.Also upon the commencement of your employment and subject to approval of the Board and the terms of the Equity Incentive Plan, you will be granted the following stock options and restricted stock units (“RSUs”) (the “Performance-Based Options” and “Performance-Based RSUs”, respectively):

·A RSU covering 20,000 shares of the Company’s Common Stock and a stock option to purchase 80,000 shares of the Company’s Common Stock, each of which will be subject to Standard Vesting and will have a vesting commencement date that is the earlier of (a) the date the Company executes a Transaction Agreement which covers at least Europe (which shall include at minimum the following 7 countries: Germany, France, Spain, Italy, Belgium, Sweden and the United Kingdom), or (b) the date that is the later of the date that the Company’s Board approves a detailed written commercialization plan regarding sales of fidaxomicin by Optimer outside of North America and the date upon which Optimer has made commercial sales of fidaxomicin in at least three of the following countries: Germany, France, Spain, Italy, Belgium, Sweden and the United Kingdom.  For purposes of this letter agreement, the term “Transaction Agreement” shall mean a Board-approved written contractual arrangement entered into by the Company and a third party relating to the commercialization of fidaxomicin and including the grant of an exclusive (or co-exclusive with the Company) license to such third party for such commercialization; provided, however, that in no event shall a Transaction Agreement include (x) any agreement or arrangement that involves a license for commercialization of fidaxomicin solely related to the manufacture and supply of fidaxomicin or (y) any agreement or arrangement related to a Change of Control (as defined in the Company’s Severance Benefit Plan (the “Severance Plan”)).

·A RSU covering 20,000 shares of the Company’s Common Stock and a stock option to purchase 80,000 shares of the Company’s Common Stock, each of which will be subject to Standard Vesting and will have a vesting commencement date that is the date the Company receives approval from the U.S. Food and Drug Administration of the first new drug application for fidaxomicin.

·A RSU covering 20,000 shares of the Company’s Common Stock and a stock option to purchase 80,000 shares of the Company’s Common Stock, each of which will be subject to Two-Year Vesting and will have a vesting commencement date that is January 1 of the year following the first calendar year in which Net Sales of fidaxomicin by the Company in the United States are greater than $70 million.  As used in this letter agreement with respect to any equity award described herein, “Two-Year Vesting” shall mean that 1/24th of the shares subject to the award vest each month after the applicable vesting commencement date, in each case subject to you continuing to be a Service Provider (as defined in the Equity Incentive Plan) on the applicable vesting dates.  As used in this letter agreement, “Net Sales” has the meaning set forth in Exhibit A.

·A RSU covering 60,000 shares of the Company’s Common Stock and a stock option to purchase 240,000 shares of the Company’s Common Stock, each of which will be subject to Two-Year Vesting and will have a vesting commencement date that is January 1 of the year following the first calendar year in which Net Sales of fidaxomicin by the Company in the United States are greater than $200 million; provided, however, that if the Company executes a worldwide Transaction Agreement prior to such vesting commencement date, 30,000 shares of the Company’s Common Stock subject to such RSU and 120,000 shares of the Company’s Common Stock subject to such stock option shall automatically be cancelled, and the remaining portion of such RSU and stock option shall thereafter vest according to Two-Year Vesting starting from the date the Company executes such Transaction Agreement.

With respect to the Performance-Based RSUs and the Performance-Based Options whose vesting commencement dates have not occurred, in lieu of the vesting acceleration otherwise applicable to non-performance-based equity awards under the Severance Plan, the following vesting acceleration will occur upon a Covered Termination that occurs upon or within 12 months following a Change of Control (each as defined in the Severance Plan), subject to the terms and conditions of the Severance Plan:

·The vesting of 50% of the then-unvested shares subject to each such Performance-Based RSU and Performance-Based Option will accelerate if the Covered Termination occurs on or prior to the 1st anniversary of the Start Date.

·The vesting of 60% of the then-unvested shares subject to each such Performance-Based RSU and Performance-Based Option will accelerate if the Covered Termination occurs after the 1st anniversary of the Start Date and on or prior to the 2nd anniversary of the Start Date.

·The vesting of 75% of the then-unvested shares subject to each such Performance-Based RSU and Performance-Based Option will accelerate if the Covered Termination occurs after the 2nd anniversary of the Start Date and on or prior to the 3rd anniversary of the Start Date.

·The vesting of 85% of the then-unvested shares subject to each such Performance-Based RSU and Performance-Based Option will accelerate if the Covered Termination occurs after the 3rd anniversary of the Start Date and on or prior to the 4th anniversary of the Start Date.

·The vesting of all of the then-unvested shares subject to each such Performance-Based RSU and Performance-Based Option will accelerate if the Covered Termination occurs after the fourth 4th anniversary of the Start Date.

7.The Initial Option and the Performance-Based Options will be governed by and granted pursuant to separate Stock Option Agreements (whose terms shall not be inconsistent with the Equity Incentive Plan and this letter agreement) and the Equity Incentive Plan.  The exercise price per share of the Initial Option and each of the Performance-Based Options will be equal to the fair market value of the Company’s Common Stock on the date of grant as determined by the Board.  Any vested portion of the Initial Option and the Performance-Based Options will be exercisable until the earlier of one year following the date you cease to be a Service Provider or 10 years from the grant date.  The Performance-Based RSUs will be governed by and granted pursuant to separate restricted stock unit agreements (whose terms shall not be inconsistent with the Equity Incentive Plan and this letter agreement) and the Equity Incentive Plan.

8.Your compensation (including base salary, bonus and equity awards) will be reviewed by the Board and/or its Compensation Committee on an annual basis and may be adjusted from time to time as deemed appropriate by the Board and its Compensation Committee; provided that your base salary shall not be reduced below $450,000 per year.  In determining adjustments to your compensation, the Board and/or its Compensation Committee will consider the median compensation of Presidents and Chief Executive Officers of similarly-situated peer companies selected by the Board and/or its Compensation Committee (which will consist primarily of companies that have on-going product revenues after the time that the Company launches its first commercial product), and other factors deemed relevant by the Board and/or its Compensation Committee.  All of your compensation shall be subject to customary withholding taxes and any other employment taxes as are commonly required to be collected or withheld by the Company.

9.You will be eligible to receive severance benefits under, and subject to the terms and conditions of, the Severance Plan.

10.Subject to the remainder of this Section 10, the initial term of your employment will be 3 years (the “Initial Term”) and the term will automatically renew for successive one-year terms thereafter (each an “Additional Term”) unless a notice of non-renewal is provided by either you or the Company to the other at least 6 months prior to the expiration of the Initial Term or the then-current Additional Term, as applicable, or unless earlier terminated by the Company pursuant to the provisions below.  The Company may terminate your employment for Cause (as defined in the Severance Plan) at any time and without prior notice, provided that the Company has previously provided you notice of, and an opportunity for 30 days to cure (if curable), the conditions giving rise to Cause if such conditions relate solely to clauses (ii), (iv), (v) or (vii) of such definition in the

Severance Plan as in effect on the date hereof.  The Company may also terminate your employment at any time without Cause and without prior notice, or you may terminate your employment at any time in a Constructive Termination (as defined in the Severance Plan), provided that if such termination is (a) without Cause or is a Constructive Termination, (b) is not within 12 months following a Change of Control (as defined in the Severance Plan) and (c) is prior to the 8-year anniversary of the Start Date, then the Company shall pay you, in addition to the benefits to which you may be entitled under the Severance Plan, a lump sum cash payment equal to (x) the sum of your then-current base salary plus the annual bonus paid to you for the preceding year, if any, multiplied by (y) a fraction, the numerator of which is the number of days remaining in the Initial Term or then-current Additional Term, as applicable, at the time of such termination and the denominator of which is the total number of days in the Initial Term or then-current Additional Term, as applicable (1,095 days for the Initial Term or 365 days for any Additional Term). Your right to receive such additional cash payment will be subject to your eligibility to receive payments under the Severance Plan, including the obligation to sign a waiver and release of claims and allow it to become effective in accordance with its terms, and will be subject to standard deductions and withholdings.

11.As required by law, this offer is subject to satisfactory proof of your right to work in the United States.

12.As a Company employee, you will be expected to abide by Company policies and procedures, and acknowledge in writing that you have read and will comply with the Company’s employee handbook.  As a condition of employment, you must read, sign and comply with the Company’s standard Employee Proprietary Information Agreement  which is enclosed with this letter agreement.

13.By signing this letter agreement, you represent that you have disclosed to the Company any contract you have signed or other obligations you are bound by that may restrict the performance of your duties on behalf of the Company.

14.This letter agreement will be governed by and construed according to the laws of the State of California. You and the Company hereby expressly consent to the personal jurisdiction of the state and federal courts located in San Diego, California for any lawsuit arising from or related to this letter agreement.  The terms in this letter agreement and the enclosed Employee Proprietary Information Agreement supersede any other agreements or promises made between you and the Company, whether oral or written, with respect to your employment terms.  This letter agreement cannot be changed except in a written agreement signed by you and another duly authorized officer of the Company.

Please sign and date this letter agreement and the enclosed Employee Proprietary Information Agreement if you wish to accept employment at the Company under the terms described above.

We look forward to your favorable reply and to a productive and enjoyable work relationship.

Sincerely,

/s/ Michael N. Chang

Michael N. Chang, for Optimer Pharmaceuticals, Inc.

Accepted:

/s/ Pedro Lichtinger	May 5, 2010
Pedro Lichtinger	Date

Exhibit A

“Net Sales” shall mean the gross amounts invoiced for sales of fidaxomicin by or on behalf of the Company or its affiliates to third parties less the following deductions to the extent included in the gross invoiced sales price for fidaxomicin or otherwise directly paid or incurred by the Company or its affiliates with respect to the sale or other disposition of fidaxomicin:

1.normal and customary trade and quantity discounts actually allowed and properly taken directly with respect to sales of fidaxomicin;

2.credits or allowances given or made for rejection of or return of previously sold fidaxomicin product or for retroactive price reductions and billing errors;

3.rebates and chargeback payments granted to managed health care organizations, pharmacy benefit managers (or equivalents thereof), national, state/provincial, local, and other governments, their agencies and purchasers and reimbursers, or to trade customers;

4.costs of freight, insurance, and other transportation charges directly related to the distribution of fidaxomicin;

5.taxes, duties or other governmental charges (including any tax such as a value added or similar tax, other than any taxes based on income) levied on or measured by the billing amount for fidaxomicin, as adjusted for rebates and refunds; and

6.the actual amount of any write-offs for bad debt directly relating to sales of fidaxomicin during an applicable period.

In no event will any particular amount identified above be deducted more than once in calculating Net Sales.  Sales of fidaxomicin between the Company and its affiliates for resale shall be excluded from the computation of Net Sales, but the subsequent resale of fidaxomicin to a third party shall be included within the computation of Net Sales.  Any free-of-charge disposal or use of fidaxomicin for development, regulatory or marketing purposes, such as clinical trials, compassionate use or indigent patient programs, shall not be deemed a sale for purposes of calculating Net Sales.

EX-99.2

Exhibit 99.2

May 5, 2010

To:  Michael Chang

Dear Michael:

This letter sets forth the terms and conditions of the separation and consulting agreement (the “Agreement”) that Optimer Pharmaceuticals, Inc. (the “Company”) is offering to you to aid in your employment transition.

1.             Resignation From Employment.  You have voluntarily resigned your position as the Company’s President and Chief Executive Officer effective as of May 5, 2010 (the “Separation Date”).  You hereby acknowledge that your resignation of employment is voluntary, is not based on facts that would give rise to a Constructive Termination as defined in the Company’s Amended and Restated Severance Benefit Plan (the “Severance Plan”), and does not otherwise constitute a Covered Termination under the Severance Plan.  Accordingly, except as specifically set forth herein, you will not be entitled to receive any severance benefits following the Separation Date, whether under the Severance Plan or otherwise.

2.             Accrued Salary and Vacation Pay.  On the Separation Date, the Company will pay you any and all accrued and unused vacation and any and all accrued salary earned through the Separation Date, less standard payroll deductions and withholdings.

3.             Health Insurance.  To the extent provided by the federal COBRA law or, if applicable, state insurance laws, and by the Company’s current group health insurance policies, you will be eligible to continue your group health insurance benefits following the Separation Date.  Later, you may be able to convert to an individual policy through the provider of the Company’s health insurance, if you wish.  You will be provided with a separate notice describing your rights and obligations under COBRA.

4.             Service as Chairman of the Board of Directors.  Subject to the approval of the Company’s Board of Directors (the “Board”) you will be appointed as the Chairman of the Board.  For your service as Chairman, you will be entitled to an annual stipend of fifty thousand dollars ($50,000), which amount shall be pro-rated for any partial year of service subject to adjustment from time to time of any policy regarding compensation of non-employee directors.  The stipend shall be paid in arrears in four installments of twelve thousand, five hundred dollars ($12,500) (or the appropriate pro rata portion thereof), to be paid at the end of each calendar quarter in which you serve as Chairman. In addition, and subject to the approval of the Board, following your appointment as Chairman you will receive a grant of sixty-five thousand (65,000) fully-vested shares of the Company’s Common Stock.

5.             Stock Options.  If you sign this Agreement, allow it to become effective, and commence providing consulting services as described below, there will be no disruption in your continuous service as a Service Provider under the Company’s 2006 Equity Incentive Plan (the “Plan”).  Accordingly, your outstanding stock options will continue to vest during the Term of the consulting relationship (as defined below).

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6.             Consulting Relationship.  As part of this Agreement, the Company agrees to retain you, and you agree to make yourself available to perform services, as a consultant under the following terms and conditions:

6.1          Consulting Services.During the Term (as defined below), you agree to make yourself available to perform a minimum of fifty (50) hours of consulting services for the Company per month.  The consulting services shall consist of assisting with the transition of the Company’s new Chief Executive Officer and advising the Company and/or the Board on any matter within your business or professional expertise as they may request from time to time (the “Consulting Services”).

6.2          Compensation.

(a)           Consulting Fees.  In exchange for providing the Consulting Services, the Company shall pay you consulting fees in the amount of twelve thousand, five hundred dollars ($12,500) per month (the “Consulting Fees”).  For the year 2010, in addition to the Consulting Fees, you shall be eligible to earn additional fees of up to one hundred and ninety six thousand, five hundred dollars ($196,500) (the “Additional Consulting Fees”), based on the Company’s achievement relative to the set of pre-established corporate goals (the “Goals”) established by the Compensation Committee of the Board in connection with the Company’s 2010 Incentive Compensation Plan.  A minimum of seventy-five percent (75%) achievement of the Goals is a prerequisite to your receipt of any Additional Consulting Fees.  The Compensation Committee of the Board shall have the sole discretion to determine (i) whether and to what extent the Company has achieved the Goals and (ii) whether and to what extent any Additional Consulting Fees will be paid based on such achievement.

(b)           Stock Options.  Subject to the approval of the Board, you will be granted four stock options, as follows:

(i)            A stock option to purchase 150,000 shares of the Company’s Common Stock, which will be subject to Two-Year Vesting and have a vesting commencement date that is the date the Company receives notice from the U.S. Food and Drug Administration (the “FDA”) of the FDA’s acceptance of the Company’s filing of a new drug application (a “NDA”) for fidaxomicin.  As used in this Agreement with respect to any stock option described herein, “Two-Year Vesting” shall mean that 25% of the shares subject to the stock option vest on the applicable vesting commencement date and 1/24th of the remaining shares subject to the stock option vest monthly thereafter, in each case subject to you continuing to be a Consultant (as defined in the Plan) on the applicable vesting dates.

(ii)           A stock option to purchase 50,000 shares of the Company’s Common Stock, which will be subject to Two-Year Vesting and have a vesting commencement date that is the date the Company receives notice from the European Medicines Agency (the “EMA”) of the EMA’s acceptance of the Company’s filing of a marketing authorization application (a “MAA”) for fidaxomicin.

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(iii)         A stock option to purchase 150,000 shares of the Company’s Common Stock, which will be subject to Two-Year Vesting and have a vesting commencement date that is the date the Company receives approval from the FDA of a NDA for fidaxomicin.

(iv)          A stock option to purchase 50,000 shares of the Company’s Common Stock, which will be subject to Two-Year Vesting and have a vesting commencement date that is the date the Company receives approval from the EMA of a MAA for fidaxomicin.

You will also be eligible to receive additional grants of stock options annually in the Board’s sole discretion.  All stock options under this Agreement will be governed by and granted pursuant to separate Stock Option Agreements and the Plan.  The exercise price per share of the stock options under this Agreement will be equal to the fair market value of the Company’s Common Stock on the date of grant as determined by the Board.  Any vested portion of the stock options will be exercisable until the earlier of one year following the date you cease to be a Service Provider or, for those stock options granted under this Section 6, a Consultant, or 10 years from the grant date.

6.3          Term and Termination.

(a)           Term.  The term of this Agreement will begin on May 5, 2010 (the “Consulting Commencement Date”), and will continue until the earlier of the five year anniversary of the Consulting Commencement Date or termination by either party as provided herein (the “Term”).  The Term may be extended by the mutual agreement of the parties.

(b)           Termination.  Either party may terminate this Agreement for material breach by the other party upon giving the other party 30 days’ prior written notice specifying the nature of the breach, if such breach has not been cured within such 30-day period.  Notwithstanding the foregoing, the Company may elect to terminate this Agreement immediately and without prior notice if it determines that you have refused to and/or are unable to perform the Consulting Services.

6.4          Confidentiality.

(a)           Definition.  “Confidential Information” means any non-public information that relates to the actual or anticipated business or research and development of the Company, technical data, trade secrets or know-how, including, but not limited to, research, product plans or other information regarding Company’s products or services and markets therefor, customer lists and customers (including, but not limited to, customers of the Company on whom you called or with whom you became acquainted during the term of this Agreement), software, developments, inventions, processes, formulas, technology, designs, drawing, engineering, hardware configuration

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information, marketing, finances or other business information.  Confidential Information does not include information that (i) is known to you at the time of disclosure (other than in connection with your previous employment with the Company) as evidenced by your written records, (ii) has become publicly known and made generally available through no wrongful act of your own; or (iii) you have rightfully received from a third party who is authorized to make such disclosure.

(b)           Nonuse and Nondisclosure.  You will not, during or subsequent to the Term of this Agreement, (i) use the Confidential Information for any purpose whatsoever other than the performance of the Consulting Services or your duties as Chairman of the Board on behalf of the Company or (ii) disclose the Confidential Information to any third party.  You agree that all Confidential Information will remain the sole property of the Company.  You also agree to take all reasonable precautions to prevent any unauthorized disclosure of such Confidential Information.  Without the Company’s prior written approval, you will not directly or indirectly disclose to anyone the existence of this Agreement or the fact that you have this arrangement with the Company.

(c)           Former Client Confidential Information.  You agree that you will not, during the Term of this Agreement, improperly use or disclose any proprietary information or trade secrets of any former or current employer or other person or entity with which you have an agreement or duty to keep in confidence information you have acquired, if any.  You also agree that you will not bring onto the Company’s premises any unpublished document or proprietary information belonging to any such employer, person or entity unless consented to in writing by such employer, person or entity.

(d)           Third-Party Confidential Information.  You recognize that the Company has received and in the future will receive from third parties their confidential or proprietary information subject to a duty on the Company’s part to maintain the confidentiality of such information and to use it only for certain limited purposes.  You agree that, during the Term of this Agreement and thereafter, you owe the Company and such third parties a duty to hold all such confidential or proprietary information in the strictest confidence and not to disclose it to any person, firm or corporation or to use it except as necessary in carrying out the Services for the Company consistent with the Company’s agreement with such third party.

(e)           Return of Materials.  Upon the termination of this Agreement, or upon Company’s earlier request, you will deliver to the Company all of the Company’s property, including but not limited to all electronically stored information and passwords to access such property, or Confidential Information that you may have in your possession or control.

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6.5          Ownership.

(a)           Assignment.  You agree that all copyrightable material, notes, records, drawings, designs, inventions, improvements, developments, discoveries and trade secrets conceived, discovered, developed or reduced to practice by you, solely or in collaboration with others, during the Term that relate in any manner to the business of the Company that you may be directed to undertake, investigate or experiment with or that you may become associated with in work, investigation or experimentation in the Company’s line of business in performing the Consulting Services under this Agreement (collectively, “Inventions”), are the sole property of the Company. You also agree to assign (or cause to be assigned) and hereby assign fully to the Company all Inventions and any copyrights, patents, mask work rights or other intellectual property rights relating to all Inventions.

(b)           Further Assurances.  You agree to assist Company, or its designee, at the Company’s expense, in every proper way to secure the Company’s rights in Inventions and any copyrights, patents, mask work rights or other intellectual property rights relating to all Inventions in any and all countries, including the disclosure to the Company of all pertinent information and data with respect to all Inventions, the execution of all applications, specifications, oaths, assignments and all other instruments that the Company may deem necessary in order to apply for and obtain such rights and in order to assign and convey to the Company, its successors, assignees and nominees the sole and exclusive right, title and interest in and to all Inventions, and any copyrights, patents, mask work rights or other intellectual property rights relating to all Inventions.  You also agree that your obligation to execute or cause to be executed any such instrument or papers shall continue after the termination of this Agreement.

(c)           Pre-Existing Materials.  Subject to subsection (a), you agree that if, in the course of performing the Services, you incorporate into any Invention developed under this Agreement any pre-existing invention, improvement, development, concept, discovery or other proprietary information owned by you or in which you have an interest, (i) you will inform Company in writing, before incorporating such invention, improvement, development, concept, discovery or other proprietary information into any Invention, and (ii) the Company is hereby granted a nonexclusive, royalty-free, perpetual, irrevocable, worldwide license to make, have made, modify, use and sell such item as part of or in connection with such Invention. You will not incorporate any invention, improvement, development, concept, discovery or other proprietary information owned by any third party into any Invention without Company’s prior written permission.

6.6          Independent Contractor; Benefits.

(a)           Independent Contractor.  It is the express intention of you and the Company that you will perform the Consulting Services as an independent contractor to the Company.  Nothing in this Agreement is intended or shall in any way be construed to make you an agent, employee or representative of the Company.  Without limiting the generality of the foregoing, you are not authorized to bind the Company to any liability or obligation or to represent that you have any such authority.  You agree to furnish (or reimburse the Company for) all tools and materials necessary to accomplish this Agreement and shall incur all expenses associated with performance, except as expressly provided herein.  As an independent contractor, you will be solely responsible for, and will file, on a timely basis, all tax returns and payments required to be filed with, or made to, any federal, state or local tax authority with respect to the performance of Consulting

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Services and receipt of benefits under this Agreement.  No part of your Consulting Fees will be subject to withholding by the Company for the payment of any social security, federal, state or any other payroll tax.  The Company will report any compensatory amounts paid to you under this Agreement by filing a Form 1099-MISC with the Internal Revenue Service as required by law.

(b)           Benefits.  The Company and you agree that you will receive no Company-sponsored benefits from the Company.  If you are reclassified by a state or federal agency or court as Company’s employee, you will become a reclassified employee and will receive no benefits from the Company, except those mandated by state or federal law, even if by the terms of the Company’s benefit plans or programs of the Company in effect at the time of such reclassification, Consultant would otherwise be eligible for such benefits.

6.7          Indemnification.  You agree to indemnify and hold harmless the Company and its directors, officers and employees from and against all taxes, losses, damages, liabilities, costs and expenses, including attorneys’ fees and other legal expenses, arising directly or indirectly from or in connection with (i) any negligent, reckless or intentionally wrongful act of yours or your assistants, employees or agents, (ii) a determination by a court or agency that you are not an independent contractor, (iii) any breach by you or your assistants, employees or agents of any of the covenants contained in this Agreement, (iv) your failure to perform the Consulting Services in accordance with all applicable laws, rules and regulations, or (v) any violation or claimed violation of a third party’s rights resulting in whole or in part from the Company’s use of your work product under this Agreement.

7.             No Other Compensation or Benefits.You acknowledge that, except as expressly provided in this Agreement, you will not be entitled to receive any additional compensation, severance, or benefits from the Company after the Separation Date.

8.             Expense Reimbursements. You agree that, within ten (10) days of the Separation Date, you will submit your final documented expense reimbursement statement reflecting all business expenses you incurred through the Separation Date, if any, for which you seek reimbursement.  The Company will reimburse you for these expenses pursuant to its regular business practice.  During the Term, you will be eligible for reimbursement of up to twenty thousand dollars ($20,000.00) per calendar year (pro rated for any partial year of service) of documented, reasonable expenses for travel associated with: (i) performance of the Consulting Services and/or (ii) attendance at Board and committee meetings.  These amounts shall be reimbursed pursuant to the Company’s regular business practice.

9.             Proprietary Information Obligations.  You acknowledge and affirm your agreement to adhere to your continuing obligations under your Employee Proprietary Information Agreement.

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10.          Release of Claims.In exchange for the consideration provided to you by this Agreement that you are not otherwise entitled to receive, including but not limited to the opportunity to consult for the Company following the Separation Date, you hereby generally and completely release the Company and its current and former directors, officers, employees, stockholders, partners, agents, attorneys, predecessors, successors, parent and subsidiary entities, insurers, affiliates, and assigns (collectively, the “Released Parties”) from any and all claims, liabilities and obligations, both known and unknown, that arise out of or are in any way related to events, acts, conduct, or omissions occurring prior to or on the date that you sign this Agreement (collectively, the “Released Claims”).  The Released Claims include, but are not limited to:  (a) all claims arising out of or in any way related to your employment with the Company, or the termination of that employment; (b) all claims related to your compensation or benefits from the Company including salary, bonuses, commissions, vacation pay, expense reimbursements, severance pay, fringe benefits, stock, stock options, or any other ownership interests in the Company; (c) all claims for breach of contract, wrongful termination, and breach of the implied covenant of good faith and fair dealing, including but not limited to claims arising under or related to your Employment Agreement; (d) all tort claims, including claims for fraud, defamation, emotional distress, and discharge in violation of public policy; and (e) all federal, state, and local statutory claims, including claims for discrimination, harassment, retaliation, attorneys’ fees, or other claims arising under the federal Civil Rights Act of 1964 (as amended), the federal Americans with Disabilities Act of 1990, the federal Age Discrimination in Employment Act of 1967 (as amended) (the “ADEA”), the California Labor Code, and the California Fair Employment and Housing Act (as amended).  Notwithstanding the foregoing, the following are not included in the Released Claims (the “Excluded Claims”): (a) any rights or claims for indemnification you may have pursuant to any written indemnification agreement with the Company to which you are a party, the charter, bylaws, or operating agreements of the Company, or under applicable law; (b) any rights that are not waivable as a matter of law; or (c) any claims arising from the breach of this Agreement.  You hereby represent and warrant that, other than the Excluded Claims, you are not aware of any claims you have or might have against any of the Released Parties that are not included in the Released Claims.

11.          ADEA Waiver.  You acknowledge that you are knowingly and voluntarily waiving and releasing any rights you may have under the ADEA (“ADEA Waiver”).  You also acknowledge that the consideration given for the ADEA Waiver is in addition to anything of value to which you were already entitled.  You are advised by this writing, as required by the ADEA, that:  (a) your waiver and release do not apply to any claims that may arise after you sign this Agreement; (b) you should consult with an attorney prior to executing this release; (c) you have twenty-one (21) days within which to consider this release (although you may choose to voluntarily execute this release earlier); (d) you have seven (7) days following the execution of this release to revoke this Agreement (in a written revocation sent to me); and (e) this Agreement will not be effective until the eighth day after you sign this Agreement, provided that you have not earlier revoked this Agreement (the “Effective Date”).  You will not be entitled to receive any of the benefits specified by this Agreement unless and until it becomes effective.

12.          Section 1542 Waiver.  In giving the releases set forth in this Agreement, which include claims which may be unknown to you at present, you acknowledge that you have read and understand Section 1542 of the California Civil Code which reads as follows:  “A general release does not extend to claims which the creditor does not know or suspect to exist in his favor at the time of executing the release, which if known by him must have materially affected his settlement with the debtor.”  You hereby expressly waive and relinquish all rights and benefits under that section and any law or legal principle of similar effect in any jurisdiction with respect to the releases granted herein, including but not limited to the release of unknown and unsuspected claims granted in this Agreement.

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13.          Miscellaneous.  This Agreement constitutes the complete, final and exclusive embodiment of the entire agreement between you and the Company with regard to its subject matter.  Without limiting the foregoing, each of you and the Company hereby acknowledge and agree that the Employment Agreement between you and the Company, dated June 17, 2005, as amended, is hereby terminated in its entirety.  This Agreement is entered into without reliance on any promise or representation, written or oral, other than those expressly contained herein, and it supersedes any other such promises, warranties or representations.  This Agreement may not be modified or amended except in a writing signed by both you and a duly authorized officer of the Company.  This Agreement will bind the heirs, personal representatives, successors and assigns of both you and the Company, and inure to the benefit of both you and the Company, and your and its heirs, successors and assigns.  If any provision of this Agreement is determined to be invalid or unenforceable, in whole or in part, this determination will not affect any other provision of this Agreement and the provision in question will be modified so as to be rendered enforceable.  This Agreement will be deemed to have been entered into and will be construed and enforced in accordance with the laws of the State of California as applied to contracts made and to be performed entirely within California.  Any ambiguity in this Agreement shall not be construed against either party as the drafter.  Any waiver of a breach of this Agreement shall be in writing and shall not be deemed to be a waiver of any successive breach.  This Agreement may be executed in counterparts and facsimile signatures will suffice as original signatures.

If this Agreement is acceptable to you, please sign below and return the original to me.

Sincerely,

OPTIMER PHARMACEUTICALS, INC.

By:	/s/ Pedro Lichtinger
	Pedro Lichtinger, Chief Executive Officer and President
UNDERSTOOD AND AGREED:
/s/ Michael Chang
Michael Chang
Date: May 5, 2010

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EX-99.3

Exhibit 99.3

OPTIMER PHARMACEUTICALS, INC.

AMENDED AND RESTATED SEVERANCE BENEFIT PLAN

Section 1.INTRODUCTION.

The Optimer Pharmaceuticals, Inc. Amended and Restated Severance Benefit Plan (the “Plan”) was established effective May 5, 2010 (the “Effective Date”) and amends and restates in its entirety the Optimer Pharmaceuticals, Inc. Severance Benefit Plan established effective October 2, 2008 (the “Prior Plan”).  The purpose of the Plan is to provide for the payment of severance benefits to certain eligible employees of Optimer Pharmaceuticals, Inc. (the “Company”) whose employment with the Company is terminated in a covered termination and who meet the eligibility criteria set forth in Section 2(a) below.  This document constitutes the written instrument under which the Plan is maintained and supersedes any prior plan or practice of the Company or any written agreement between the Company and any employee that provides for payments or benefits in the event of termination of employment or a change in control of the Company, including but not limited to the Prior Plan, except to the extent such written agreement expressly contemplates that such persons are eligible to receive benefits additional to or in lieu of those provided under the Plan.  This Plan document also is the Summary Plan Description for the Plan.

Section 2.ELIGIBILITY FOR BENEFITS.

(a)General Rules.  Subject to the requirements set forth in this Section, the Company will grant severance benefits under the Plan to Eligible Employees.

(1)Definition of “Eligible Employee.”  For purposes of this Plan, an Eligible Employee is a full-time or a part-time regular hire employee of the Company who is notified by the Company in writing that he or she is eligible for participation in the Plan and (i) whose employment is terminated in a Covered Termination (as defined further in Section 2(c) below) provided that the employee has been continuously employed by the Company for at least one hundred eighty (180) days; or (ii) who is selected by the Plan Administrator in its sole discretion to receive the benefits set forth herein.  The determination of whether an employee is an Eligible Employee shall be made by the Company, in its sole discretion, and such determination shall be binding and conclusive on all persons.  For purposes of this Plan, part-time employees are those regular hire employees who are regularly scheduled to work more than twenty (20) hours per week but less than a full-time work schedule.  Regular hire employees working twenty (20) hours per week or less and temporary employees are not eligible for severance benefits under the Plan.

(2)In order to be eligible to receive any benefits under the Plan, an Eligible Employee who is terminated in a Covered Termination must remain on the job until his or her date of termination as scheduled by the Company, which may not exceed thirty (30) days from the date of any notification of termination.

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(3)In order to be eligible to receive any benefits under the Plan, an Eligible Employee also must execute a general waiver and release in substantially the form attached hereto as Exhibit A, Exhibit B or Exhibit C, as appropriate, and such release must become effective in accordance with its terms.  The Company, in its discretion, may modify the form of the required release to comply with applicable law and shall determine the form of the required release, which may be incorporated into a termination agreement or other agreement with the Eligible Employee.

(b)Exceptions to Benefit Entitlement.  An employee, including an employee who otherwise is an Eligible Employee, will not receive benefits under the Plan (or will receive reduced benefits under the Plan) in the following circumstances, as determined by the Company in its sole discretion:

(1)The employee has executed an individually negotiated employment contract or agreement with the Company relating to severance benefits that is in effect on his or her termination date, in which case such employee’s severance benefit, if any, shall be governed by the terms of such individually negotiated employment contract or agreement and shall be governed by this Plan only to the extent that the reduction pursuant to Section 3(c) below does not entirely eliminate benefits under this Plan.

(2)The employee voluntarily terminates employment with the Company for any reason not constituting a Constructive Termination.  Voluntary terminations include, but are not limited to, resignation, retirement or failure to return from a leave of absence on the scheduled date.

(3)The employee is offered an identical or substantially equivalent or comparable position with the Company or an affiliate of the Company.  For purposes of the foregoing, a “substantially equivalent or comparable position” is one that offers the employee substantially the same level of responsibility and compensation and does not require a relocation of the employee’s place of employment by more than thirty (30) miles from its previous location.

(4)The employee is offered immediate reemployment by a successor to the Company or an affiliate of the Company or by a purchaser of its assets, as the case may be, following a change in ownership of the Company or a sale of substantially all of the assets of a division or business unit of the Company.  For purposes of the foregoing, “immediate reemployment” means that the employee’s employment with the successor to the Company or an affiliate of the Company or the purchaser of its assets, as the case may be, results in uninterrupted employment such that the employee does not incur a lapse in pay as a result of the change in ownership of the Company or the sale of its assets.

(5)The employee is rehired by the Company or an affiliate of the Company prior to the date benefits under the Plan are scheduled to commence.

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(6)The employee does not confirm in writing that he or she is and shall remain subject to the Company’s Proprietary Information and Inventions Agreement, including the failure to sign a termination statement under such Agreement.

(7)Following notification of involuntary termination by the Company, the employee does not satisfactorily perform his or her assigned job duties until the date set by the Company for the termination of employment.

(8)The employee terminates employment due to the employee’s death or Disability.

(c)Definitions:  For purposes of this Plan, the following terms shall have the meanings set forth below:

(1)“Base Salary” means the Eligible Employee’s base pay (excluding incentive pay, premium pay, commissions, overtime, bonuses and other forms of variable compensation), at the rate in effect during the last regularly scheduled payroll period immediately preceding the Eligible Employee’s termination date.  For any Eligible Employees that are regular part-time employees, “Base Salary” shall mean the pro-rata equivalent of the Eligible Employee’s base pay which reflects the part-time status of the Eligible Employee.

(2)“Cause” for termination of employment means a termination resulting from the occurrence of any of the following events that has a material negative impact on the business or reputation of the Company:

(i)the employee’s attempted commission of, or participation in, a fraud or act of dishonesty against the Company;

(ii)the employee’s intentional, material violation of any contract or agreement between the employee and the Company or of any statutory duty owed to the Company;

(iii)the employee’s unauthorized use or disclosure of the Company’s confidential information or trade secrets;

(iv)an employee’s intentional refusal or intentional failure to act in accordance with any lawful and proper direction or order of his or her superiors;

(v)an employee’s habitual neglect of the duties of employment;

(vi)an employee’s indictment, charge, or conviction of a felony or any crime involving moral turpitude, or participation in any act of theft or dishonesty; or

(vii)the employee’s gross misconduct.

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(3)“Change of Control” means any of the following events:

(i)a sale, lease or disposition of all or substantially all of the assets of the Company; or;

(ii)a merger or consolidation (in a single transaction or a series of related transactions) of the Company with or into any other corporation or corporations or other entity, or any other corporate reorganization, where the stockholders of the Corporation immediately prior to such event do not retain more than fifty percent (50%) of the voting power of and interest in the successor entity (excluding any transactions if the primary purpose of the transaction is to obtain financing from new or existing investors).

The Board shall have the right to determine whether a Change of Control has occurred in accordance with the foregoing definition, and its determination shall be final, binding and conclusive on all persons.

(4)“Constructive Termination” means the occurrence of one or more of the following events, provided that the Eligible Employee has first provided written notice to the Company within 90 days of the first such occurrence of such condition specifying the event(s) constituting Constructive Termination and specifying that the Eligible Employee intends to terminate employment not earlier than 30 days after providing such notice, and the Company (or surviving corporation) has not cured such event(s) within 30 days (or such longer period as may be specified by the Eligible Employee in such notice) after such written notice is received by the Company (the “Cure Period”), and the Eligible Employee resigns within 30 days following the end of the Cure Period:

(i)a material diminution in the Eligible Employee’s authority, duties or responsibilities; or

(ii)the relocation by the Company of the principle place for the rendering of the Eligible Employee’s services hereunder to a location that requires a one-way increase in the Eligible Employee’s driving distance of more than 45 miles; or

(iii)a material reduction by the Company of annual base compensation, which reduction is not applicable to all of the Company’s senior executive employees.

However, none of the foregoing will constitute a Constructive Termination to the extent mutually agreed upon in advance of the occurrence thereof by the Eligible Employee.

(5)“Covered Termination” means (i) an involuntary termination of an employee’s employment by the Company other than for Cause or (ii) a Constructive Termination by an Eligible Employee who is the Chief Executive Officer, or a Company Officer.  A Covered Termination does not include a termination of employment resulting from such Eligible Employee’s resignation for any reason not constituting a Constructive Termination, or due to the Eligible Employee’s death or Disability.

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(6)“Disability” means the employee is prevented from performing his duties hereunder by reason of any physical or mental incapacity that results in the employee’s satisfaction of all requirements necessary to receive benefits under the Company’s long-term disability plan due to a total disability.  If the Company has no long-term disability plan in place, “Disability” shall mean a physical or mental disability or infirmity of the employee, as determined by a physician of recognized standing selected by the Company, that prevents (or, in the opinion of such physician, is reasonably expected to prevent) the normal performance of his duties as an employee of the Company for any continuous period of 180 days, or for 180 days during any one 12-month period.

(7)“Equity Award” means any stock option, restricted stock, restricted stock unit, or other equity award to acquire shares of the Company’s stock.  Notwithstanding the foregoing, for all purposes of the Plan “Equity Award” does not include any equity award issued under or held in any plan that is intended to be qualified under Section 401(a) of the Internal Revenue Code.

(8)“Non-Performance Vesting Equity Award” means at any given time an Equity Award that is not a Performance Vesting Equity Award.

(9)“Performance Vesting Equity Award” means at any given time an Equity Award listed on Appendix C hereto (as may be amended from time to time by the Company) for which the vesting commencement is subject to the attainment of performance goals that have not been attained at such time so that the vesting commencement date for such Equity Award has not yet occurred.

(10)“Year of Service” means each complete year of employment in which an Eligible Employee has been employed by the Company.  For purposes of this definition, a year of employment shall be a 365 day period (or 366 day period in case of a leap year) that, for the first year of employment, commences on the Eligible Employee’s date of hire and that, for any subsequent year, commences on an anniversary of that hire date.  A Year of Service shall include any leave of absence period that was approved by the Company.

Section 3.AMOUNT OF BENEFIT.

(a)Severance Benefits.  Subject to the exceptions set forth in Section 2(b), Severance benefits under the Plan, if any, shall be provided to Eligible Employees described in Section 2(a) as follows:

(i)Eligible Employees that have less than one Year of Service at the time of the Covered Termination shall receive the severance benefits described on Appendix A attached hereto.

(ii)Eligible Employees that have one or more Years of Service at the time of the Covered Termination shall receive the severance benefits described on Appendix B attached hereto.

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(iii)Severance benefits shall be provided to an Eligible Employee either under Appendix A or Appendix B, as applicable, but not both.

(b)Additional Benefits.  Notwithstanding the foregoing, the Company may, in its sole discretion, provide benefits in addition to those benefits set forth in Section 3(a) to Eligible Employees and the provision of any such benefits to an Eligible Employee shall in no way obligate the Company to provide such benefits to any other Eligible Employee or to any other employee, even if similarly situated.

(c)Certain Reductions.  The Company, in its sole discretion, shall have the authority to reduce an Eligible Employee’s severance benefits, in whole or in part, by any other severance benefits, pay in lieu of notice, or other similar benefits payable to the Eligible Employee by the Company or an affiliate of the Company that become payable in connection with the Eligible Employee’s termination of employment pursuant to (i) any applicable legal requirement, including, without limitation, the Worker Adjustment and Retraining Notification Act, the California Plant Closing Act, or any other similar state law, (ii) a written employment or severance agreement with the Company, or (iii) any Company policy or practice providing for the Eligible Employee to remain on the payroll for a limited period of time after being given notice of the termination of the Eligible Employee’s employment, and the Plan Administrator shall so construe and implement the terms of the Plan; provided, however, that notwithstanding the foregoing and any other provision in the Plan to the contrary, such reductions shall in no event reduce the cash severance benefits provided under this Plan to less than two (2) weeks of Base Salary.  The Company’s decision to apply such reductions to the severance benefits of one Eligible Employee and the amount of such reductions shall in no way obligate the Company to apply the same reductions in the same amounts to the severance benefits of any other Eligible Employee, even if similarly situated.  In the Company’s sole discretion, such reductions may be applied on a retroactive basis, with severance benefits previously paid being re-characterized as payments pursuant to the Company’s statutory obligation.

(d)Non-Duplication of Benefits.  No Eligible Employee is eligible to receive benefits under this Plan more than one time.

(e)Termination of Benefits.  With respect to each Eligible Employee, benefits under this Plan shall terminate immediately if such Eligible Employee, at any time, violates any material proprietary information, non-disparagement, confidentiality or non-solicitation obligation to the Company.

(f)Vesting Acceleration of Equity Awards.In order to give effect to any acceleration of vesting of Equity Awards to which an Eligible Employee may be entitled under this Plan, notwithstanding anything to the contrary set forth in the Eligible Employee’s Equity Award agreements or the Company’s equity plans regarding immediate forfeiture of unvested shares upon termination or service, following an Eligible Employee’s Covered Termination, the shares subject to any unvested portion of such Eligible Employee’s Equity Awards shall not be forfeited or returned to the applicable

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equity plan before any vesting acceleration of such Equity Awards provided by this Plan is finally determined and given effect, if applicable; provided, however, that nothing in this Section 3(f) prohibits the Company or a successor organization (or its parent) from causing such Equity Awards to earlier terminate pursuant to the terms of the applicable equity plan or award agreements in connection with a Change of Control, merger, acquisition or other similar corporate transaction where such Equity Awards will terminate and not be assumed by the successor or acquiring entity.

Section 4.SECTION 409A COMPLIANCE.

(a)Notwithstanding anything to the contrary set forth herein, any payments and benefits provided under the Plan (the “Severance Benefits”) that constitute “deferred compensation” within the meaning of Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”) and the regulations and other guidance thereunder and any state law of similar effect (collectively “Section 409A”) shall not commence in connection with an Eligible Employee’s termination of employment unless and until the Eligible Employee has also incurred a “separation from service” (as such term is defined in Treasury Regulation Section 1.409A-1(h) (“Separation From Service”), unless the Company reasonably determines that such amounts may be provided to the Eligible Employee without causing the Eligible Employee to incur the additional 20% tax under Section 409A.

(b)It is intended that each installment of the Severance Benefits payments provided for in this Plan is a separate “payment” for purposes of Treasury Regulation Section 1.409A-2(b)(2)(i).  For the avoidance of doubt, it is intended that payments of the Severance Benefits set forth in this Plan satisfy, to the greatest extent possible, the exemptions from the application of Section 409A provided under Treasury Regulation Sections 1.409A-1(b)(4), 1.409A-1(b)(5) and 1.409A-1(b)(9).  However, if the Company (or, if applicable, the successor entity thereto) determines that the Severance Benefits constitute “deferred compensation” under Section 409A and the Eligible Employee is, on the termination of service, a “specified employee” of the Company or any successor entity thereto, as such term is defined in Section 409A(a)(2)(B)(i) of the Code, then, solely to the extent necessary to avoid the incurrence of the adverse personal tax consequences under Section 409A, the timing of the Severance Benefit payments shall be delayed until the earlier to occur of: (i) the date that is six months and one day after the Eligible Employee’s Separation From Service, or (ii) the date of the Eligible Employee’s death (such applicable date, the “Specified Employee Initial Payment Date”), the Company (or the successor entity thereto, as applicable) shall (A) pay to the Eligible Employee a lump sum amount equal to the sum of the Severance Benefit payments that the Eligible Employee would otherwise have received through the Specified Employee Initial Payment Date if the commencement of the payment of the Severance Benefits had not been so delayed pursuant to this Section and (B) commence paying the balance of the Severance Benefits in accordance with the applicable payment schedules set forth in this Plan.

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(c)Notwithstanding anything to the contrary set forth herein, the Eligible Employee shall receive the Severance Benefits described above, if and only if the Eligible Employee duly executes and returns to the Company within the applicable time period set forth therein, but in no event more than forty-five days following Separation From Service, a separation agreement containing the Company’s standard form of release of claims in favor of the Company (attached to this Agreement as Exhibits A, B and C) and other standard provisions, including without limitation, those relating to non-disparagement and confidentiality (the “Separation Agreement”), and permits the release of claims contained therein to become effective in accordance with its terms.   Notwithstanding any other payment schedule set forth in this Plan, none of the Severance Benefits will be paid or otherwise delivered prior to the effective date of the Separation Agreement.  Except to the extent that payments may be delayed until the Specified Employee Initial Payment Date pursuant to the preceding paragraph, on the first regular payroll pay day following the effective date of the Separation Agreement, the Company will pay the Eligible Employee the Severance Benefits the Eligible Employee would otherwise have received under the Plan on or prior to such date but for the delay in payment related to the effectiveness of the Separation Agreement, with the balance of the Severance Benefits being paid as originally scheduled.

Section 5.PARACHUTE PAYMENTS

(a)In the event that the payments provided herein and benefits otherwise payable to an Eligible Employee (i) constitute “parachute payments” within the meaning of Section 280G of the Code, or any comparable successor provisions, and (ii) but for this Section 5 would be subject to the excise tax imposed by Section 4999 of the Code, or any comparable successor provisions (the “Excise Tax”), then such Eligible Employee’s benefits hereunder shall be either:

(i)provided to such Eligible Employee in full, or

(ii)provided to such Eligible Employee as to such lesser extent which would result in no portion of such benefits being subject to the Excise Tax,

whichever of the foregoing amounts, when taking into account applicable federal, state, local and foreign income and employment taxes, the Excise Tax, and any other applicable taxes, results in the receipt by such Eligible Employee, on an after-tax basis, of the greatest amount of benefits, notwithstanding that all or some portion of such benefits may be taxable under the Excise Tax (the “Reduced Amount”).  If a reduction in payments or benefits constituting “parachute payments” is necessary so that the Payment equals the Reduced Amount, reduction shall occur in the following order:  reduction of cash payments; cancellation of accelerated vesting of stock awards; reduction of employee benefits.  If acceleration of vesting of stock award compensation is to be reduced, such acceleration of vesting shall be cancelled in the reverse order of the date of grant of the Eligible Employee’s stock awards.

(b)Unless the Company and such Eligible Employee otherwise agree in writing, any determination required under this Section 5 shall be made in writing in good faith by the Company’s independent certified public accountants (the “Accountants”).  For purposes of making the calculations required by this Section 5, the Accountants may make reasonable assumptions and approximations concerning applicable taxes and may rely on reasonable, good faith interpretations concerning the application of the Code, and other applicable legal authority.  The Company and such Eligible Employee shall furnish to the Accountants such information and documents as the Accountants may reasonably request in order to make a determination under this Section 5.  The Company shall bear all costs the Accountants may reasonably incur in connection with any calculations contemplated by this Section 5.

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(c)If, notwithstanding any reduction described in this Section 5, the IRS determines that such Eligible Employee is liable for the Excise Tax as a result of the receipt of the payment of benefits as described above, then such Eligible Employee shall be obligated to pay back to the Company, within thirty (30) days after a final IRS determination or in the event that such Eligible Employee challenges the final IRS determination, a final judicial determination, a portion of the payment equal to the “Repayment Amount.”  The Repayment Amount with respect to the payment of benefits shall be the smallest such amount, if any, as shall be required to be paid to the Company so that such Eligible Employee’s net after-tax proceeds with respect to any payment of benefits (after taking into account the payment of the Excise Tax and all other applicable taxes imposed on such payment) shall be maximized.  The Repayment Amount with respect to the payment of benefits shall be zero if a Repayment Amount of more than zero would not result in such Eligible Employee’s net after-tax proceeds with respect to the payment of such benefits being maximized.  If the Excise Tax is not eliminated pursuant to this paragraph, such Eligible Employee shall pay the Excise Tax.

(d)Notwithstanding any other provision of this Section 5, if (i) there is a reduction in the payment of benefits as described in this Section 5, (ii) the IRS later determines that such Eligible Employee is liable for the Excise Tax, the payment of which would result in the maximization of such Eligible Employee’s net after-tax proceeds (calculated as if such Eligible Employee’s benefits had not previously been reduced), and (iii) such Eligible Employee pays the Excise Tax, then the Company shall pay to such Eligible Employee those benefits which were reduced pursuant to this Section 5 contemporaneously or as soon as administratively possible after such Eligible Employee pays the Excise Tax so that such Eligible Employee’s net after-tax proceeds with respect to the payment of benefits is maximized.

(e)If an Eligible Employee either (i) brings any action to enforce such Eligible Employee’s rights pursuant to this Section 5, or (ii) defends any legal challenge to such Eligible Employee’s rights hereunder, such Eligible Employee shall be entitled to recover attorneys’ fees and costs incurred in connection with such action, regardless of the outcome of such action; provided, however, that in the event such action is commenced by such Eligible Employee, the court finds the claim was brought in good faith.

Section 6.IMPACT ON OTHER EMPLOYEE BENEFITS

(a)Continued Group Health Plan Benefits.  If the Eligible Employee was enrolled in a group health plan (e.g., medical, dental, or vision plan) sponsored by the Company or an affiliate immediately prior to termination, the Eligible Employee may be eligible to continue coverage under such group health plan (or to convert to an individual policy), at the time of the Eligible Employee’s termination of employment, under the Consolidated Omnibus Budget Reconciliation Act of 1985 (“COBRA”).  The Company will notify the Eligible Employee of any such right to continue such coverage at the time of termination pursuant to COBRA.  No provision of this Plan will affect the continuation coverage rules under COBRA.

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(b)Other Employee Benefits.  All other benefits (such as life insurance, disability coverage, and 401(k) plan coverage) terminate as of the Eligible Employee’s termination date (except to the extent that a conversion privilege may be available thereunder).

Section 7.COMPANY PROPERTY.

(a)Return of Company Property.  Except as provided in Section 7(b) below, an Eligible Employee will not be entitled to any severance benefit under the Plan unless and until the Eligible Employee returns all Company Property.  For this purpose, “Company Property” means all Company documents (and all copies thereof) and other Company property which the Eligible Employee had in his or her possession at any time, including, but not limited to, Company files, notes, drawings records, plans, forecasts, reports, studies, analyses, proposals, agreements, financial information, research and development information, sales and marketing information, operational and personnel information, specifications, code, software, databases, computer-recorded information, tangible property and equipment (including, but not limited to, leased vehicles, computers, facsimile machines, mobile telephones, servers), credit cards, entry cards, identification badges and keys; and any materials of any kind which contain or embody any proprietary or confidential information of the Company (and all reproductions thereof in whole or in part).  As a condition to receiving benefits under the Plan, Eligible Employees must not make or retain copies, reproductions or summaries of any such Company property.

(b)Retention of Certain Company Equipment.  Notwithstanding the provisions of Section 7(a), the Company and an Eligible Employee may agree to allow the Eligible Employee to retain certain Company equipment (e.g., laptops, printers, facsimile machines, copiers, etc.) (“Company Equipment”) for his or her personal use following the Eligible Employee’s termination of employment.  As a condition to retaining any Company Equipment, the Eligible Employee must execute a general waiver and release in substantially the form attached hereto as Exhibit A, Exhibit B or Exhibit C, as appropriate, and such release must become effective in accordance with its terms. The Eligible Employee acknowledges that the Eligible Employee will have imputed income related to the retention of any Company Equipment.  The Eligible Employee will follow all Company instructions as to the return and/or deletion of any Company information contained on the Company Equipment.

Section 8.WITHHOLDING TAXES AND OFFSETS FOR INDEBTEDNESS.

All payments under the Plan will be subject to applicable withholding for federal, state and local taxes.  If an Eligible Employee is indebted to the Company at his or her termination date, the Company reserves the right to offset any severance payments under the Plan by the amount of such indebtedness to the extent permitted by applicable laws.  Additionally, if an Eligible Employee is subject to withholding for taxes related to any non-Plan benefits, the Company may offset any severance payments under the Plan by the amount of such withholding taxes.

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Section 9.REEMPLOYMENT.

In the event of an Eligible Employee’s reemployment by the Company or an affiliate of the Company during the period of time in respect of which severance benefits pursuant to Sections 3(a) and 3(b) have been paid, the Company, in its sole and absolute discretion, may require such Eligible Employee to repay to the Company all or a portion of such severance benefits as a condition of reemployment.

Section 10.RIGHT TO INTERPRET PLAN; AMENDMENT AND TERMINATION.

(a)Exclusive Discretion.  The Plan Administrator (as defined in Section 13(a) herein) shall have the exclusive discretion and authority to establish rules, forms, and procedures for the administration of the Plan and to construe and interpret the Plan and to decide any and all questions of fact, interpretation, definition, computation or administration arising in connection with the operation of the Plan, including, but not limited to, the eligibility to participate in the Plan and amount of benefits paid under the Plan.  The rules, interpretations, computations and other actions of the Plan Administrator shall be binding and conclusive on all persons.

(b)Amendment or Termination.  The Company reserves the right to amend or terminate this Plan (including Appendix A and Appendix B) or the benefits provided hereunder at any time; provided, however, that no such amendment or termination shall adversely affect the right to any unpaid benefit of any Eligible Employee whose termination date has occurred prior to amendment or termination of the Plan.  In addition, following a Change of Control, no such amendment or termination may adversely affect the benefits to which an employee would become entitled under the Plan as an Eligible Employee upon a Covered Termination if the Plan had not been so amended or terminated, without the consent of the affected employee.  Furthermore, no such amendment or termination may adversely affect the benefits to which a Company officer would become entitled under the Plan as an Eligible Employee upon a Covered Termination if the Plan had not been so amended or terminated, without the consent of such affected officer.  Any action amending or terminating the Plan shall be in writing and executed by the Chief Executive Officer or Chief Financial Officer of the Company.

Section 11.NO IMPLIED EMPLOYMENT CONTRACT.

The Plan shall not be deemed (i) to give any employee or other person any right to be retained in the employ of the Company or (ii) to interfere with the right of the Company to discharge any employee or other person at any time, with or without cause, which right is hereby reserved.

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Section 12.LEGAL CONSTRUCTION.

This Plan is intended to be governed by and shall be construed in accordance with the Employee Retirement Income Security Act of 1974 (“ERISA”) and, to the extent not preempted by ERISA, the laws of the State of California (without regard to principles of conflict of laws).

Section 13.CLAIMS, INQUIRIES AND APPEALS.

(a)Applications for Benefits and Inquiries.  Any application for benefits, inquiries about the Plan or inquiries about present or future rights under the Plan must be submitted to the Plan Administrator in writing by an applicant (or his or her authorized representative).  The Plan Administrator is:

Optimer Pharmaceuticals, Inc.

Attn:  Director of Human Resources

10110 Sorrento Valley Road, Suite C

San Diego, CA  92121

(b)Denial of Claims.  In the event that any application for benefits is denied in whole or in part, the Plan Administrator must provide the applicant with written or electronic notice of the denial of the application, and of the applicant’s right to review the denial.  Any electronic notice will comply with the regulations of the U.S. Department of Labor.  The notice of denial will be set forth in a manner designed to be understood by the applicant and will include the following:

(1)the specific reason or reasons for the denial;

(2)references to the specific Plan provisions upon which the denial is based;

(3)a description of any additional information or material that the Plan Administrator needs to complete the review and an explanation of why such information or material is necessary; and

(4)an explanation of the Plan’s review procedures and the time limits applicable to such procedures, including a statement of the applicant’s right to bring a civil action under Section 502(a) of ERISA following a denial on review of the claim, as described in Section 11(d) below.

This notice of denial will be given to the applicant within ninety (90) days after the Plan Administrator receives the application, unless special circumstances require an extension of time, in which case, the Plan Administrator has up to an additional ninety (90) days for processing the application.  If an extension of time for processing is required, written notice of the extension will be furnished to the applicant before the end of the initial ninety (90) day period.

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This notice of extension will describe the special circumstances necessitating the additional time and the date by which the Plan Administrator is to render its decision on the application.

(c)Request for a Review.  Any person (or that person’s authorized representative) for whom an application for benefits is denied, in whole or in part, may appeal the denial by submitting a request for a review to the Plan Administrator within sixty (60) days after the application is denied.  A request for a review shall be in writing and shall be addressed to:

Optimer Pharmaceuticals, Inc.

Attn:  Director of Human Resources

10110 Sorrento Valley Road, Suite C

San Diego, CA  92121

A request for review must set forth all of the grounds on which it is based, all facts in support of the request and any other matters that the applicant feels are pertinent.  The applicant (or his or her representative) shall have the opportunity to submit (or the Plan Administrator may require the applicant to submit) written comments, documents, records, and other information relating to his or her claim.  The applicant (or his or her representative) shall be provided, upon request and free of charge, reasonable access to, and copies of, all documents, records and other information relevant to his or her claim.  The review shall take into account all comments, documents, records and other information submitted by the applicant (or his or her representative) relating to the claim, without regard to whether such information was submitted or considered in the initial benefit determination.

(d)Decision on Review.  The Plan Administrator will act on each request for review within sixty (60) days after receipt of the request, unless special circumstances require an extension of time (not to exceed an additional sixty (60) days), for processing the request for a review.  If an extension for review is required, written notice of the extension will be furnished to the applicant within the initial sixty (60) day period.  This notice of extension will describe the special circumstances necessitating the additional time and the date by which the Plan Administrator is to render its decision on the review.  The Plan Administrator will give prompt, written or electronic notice of its decision to the applicant. Any electronic notice will comply with the regulations of the U.S. Department of Labor.  In the event that the Plan Administrator confirms the denial of the application for benefits in whole or in part, the notice will set forth, in a manner calculated to be understood by the applicant, the following:

(1)the specific reason or reasons for the denial;

(2)references to the specific Plan provisions upon which the denial is based;

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(3)a statement that the applicant is entitled to receive, upon request and free of charge, reasonable access to, and copies of, all documents, records and other information relevant to his or her claim; and

(4)a statement of the applicant’s right to bring a civil action under Section 502(a) of ERISA.

(e)Rules and Procedures.  The Plan Administrator will establish rules and procedures, consistent with the Plan and with ERISA, as necessary and appropriate in carrying out its responsibilities in reviewing benefit claims.  The Plan Administrator may require an applicant who wishes to submit additional information in connection with an appeal from the denial of benefits to do so at the applicant’s own expense.

(f)Exhaustion of Remedies.  No legal action for benefits under the Plan may be brought until the applicant (i) has submitted a written application for benefits in accordance with the procedures described by Section 13(a) above, (ii) has been notified by the Plan Administrator that the application is denied, (iii) has filed a written request for a review of the application in accordance with the appeal procedure described in Section 13(c) above, and (iv) has been notified that the Plan Administrator has denied the appeal.  Notwithstanding the foregoing, if the Plan Administrator does not respond to a applicant’s claim or appeal within the relevant time limits specified in this Section 13, the applicant may bring legal action for benefits under the Plan pursuant to Section 502(a) of ERISA.

Section 14.BASIS OF PAYMENTS TO AND FROM PLAN.

The Plan shall be unfunded, and all cash payments under the Plan shall be paid only from the general assets of the Company.  An Eligible Employee’s right to receive payments under the Plan is no greater than that of the Company’s unsecured general creditors.  Therefore, if the Company were to become insolvent, the Eligible Employee might not receive benefits under the Plan.

Section 15.OTHER PLAN INFORMATION.

(a)Employer and Plan Identification Numbers. The Employer Identification Number assigned to the Company (which is the “Plan Sponsor” as that term is used in ERISA) by the Internal Revenue Service is 33-0830300.  The Plan Number assigned to the Plan by the Plan Sponsor pursuant to the instructions of the Internal Revenue Service is 511.

(b)Ending Date for Plan’s Fiscal Year and Type of Plan.  The date of the end of the fiscal year for the purpose of maintaining the Plan’s records is December 31.  The Plan is a welfare benefit plan.

(c)Agent for the Service of Legal Process.  The agent for the service of legal process with respect to the Plan is:

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Optimer Pharmaceuticals, Inc.

Attn:  Director of Human Resources

10110 Sorrento Valley Road, Suite C

San Diego, CA  92121

(d)Plan Sponsor and Administrator.  The Plan Sponsor and the “Plan Administrator” of the Plan is:

Optimer Pharmaceuticals, Inc.

Attn:  Director of Human Resources

10110 Sorrento Valley Road, Suite C

San Diego, CA  92121

The Plan Sponsor’s and Plan Administrator’s telephone number is (858) 909-0736.  The Plan Administrator is the named fiduciary charged with the responsibility for administering the Plan.

Section 16.STATEMENT OF ERISA RIGHTS.

Participants in this Plan are entitled to certain rights and protections under ERISA.  If you are an Eligible Employee, you are considered a participant in the Plan and, under ERISA, you are entitled to:

(a)Receive Information About Your Plan and Benefits

(1)Examine, without charge, at the Plan Administrator’s office and at other specified locations, such as worksites, all documents governing the Plan and a copy of the latest annual report (Form 5500 Series), if applicable, filed by the Plan with the U.S. Department of Labor and available at the Public Disclosure Room of the Employee Benefits Security Administration;

(2)Obtain, upon written request to the Plan Administrator, copies of documents governing the operation of the Plan and copies of the latest annual report (Form 5500 Series), if applicable, and an updated (as necessary) Summary Plan Description.  The Administrator may make a reasonable charge for the copies; and

(3)Receive a summary of the Plan’s annual financial report, if applicable.  The Plan Administrator is required by law to furnish each participant with a copy of this summary annual report.

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(b)Prudent Actions by Plan Fiduciaries.  In addition to creating rights for Plan participants, ERISA imposes duties upon the people who are responsible for the operation of the employee benefit plan.  The people who operate the Plan, called “fiduciaries” of the Plan, have a duty to do so prudently and in the interest of you and other Plan participants and beneficiaries.  No one, including your employer, your union or any other person, may fire you or otherwise discriminate against you in any way to prevent you from obtaining a Plan benefit or exercising your rights under ERISA.

(c)Enforce Your Rights.  If your claim for a Plan benefit is denied or ignored, in whole or in part, you have a right to know why this was done, to obtain copies of documents relating to the decision without charge, and to appeal any denial, all within certain time schedules as set forth in detail in Section 13 herein.

Under ERISA, there are steps you can take to enforce the above rights.  For instance, if you request a copy of Plan documents or the latest annual report from the Plan, if applicable, and do not receive them within 30 days, you may file suit in a Federal court and you are not required to follow the claims procedure set forth in Section 13 herein.  In such a case, the court may require the Plan Administrator to provide the materials and pay you up to $110 a day until you receive the materials, unless the materials were not sent because of reasons beyond the control of the Plan Administrator.

If you have completed the claims and appeals procedure described in Section 11 and have a claim for benefits which is denied or ignored, in whole or in part, you may file suit in a state or Federal court.

If you are discriminated against for asserting your rights, you may seek assistance from the U.S. Department of Labor, or you may file suit in a Federal court.  The court will decide who should pay court costs and legal fees.  If you are successful, the court may order the person you have sued to pay these costs and fees.  If you lose, the court may order you to pay these costs and fees, for example, if it finds your claim is frivolous.

(d)Assistance with Your Questions.  If you have any questions about the Plan, you should contact the Plan Administrator.  If you have any questions about this statement or about your rights under ERISA, or if you need assistance in obtaining documents from the Plan Administrator, you should contact the nearest office of the Employee Benefits Security Administration, U.S. Department of Labor, listed in your telephone directory or the Division of Technical Assistance and Inquiries, Employee Benefits Security Administration, U.S. Department of Labor, 200 Constitution Avenue N.W., Washington, D.C. 20210.  You may also obtain certain publications about your rights and responsibilities under ERISA by calling the publications hotline of the Employee Benefits Security Administration or accessing its website at http://www.dol.gov/ebsa/.

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Section 17.GENERAL PROVISIONS.

(a)Notices.  Any notice, demand or request required or permitted to be given by either the Company or an Eligible Employee pursuant to the terms of this Plan shall be in writing and shall be deemed given when delivered personally or deposited in the U.S. mail, First Class with postage prepaid, and addressed to the parties, in the case of the Company, at the address set forth in Section 15(d) and, in the case of an Eligible Employee, at the address as set forth in the Company’s employment file maintained for the Eligible Employee as previously furnished by the Eligible Employee or such other address as a party may request by notifying the other in writing.

(b)Transfer and Assignment.  The rights and obligations of an Eligible Employee under this Plan may not be transferred, assigned or alienated.  This Plan shall be binding upon any surviving entity resulting from a Change of Control and upon any other person who is a successor by merger, acquisition, consolidation or otherwise to the business formerly carried on by the Company without regard to whether or not such person or entity actively assumes the obligations hereunder.

(c)Waiver.  Any party’s failure to enforce any provision or provisions of this Plan shall not in any way be construed as a waiver of any such provision or provisions, nor prevent any party from thereafter enforcing each and every other provision of this Plan.  The rights granted the parties herein are cumulative and shall not constitute a waiver of any party’s right to assert all other legal remedies available to it under the circumstances.

(d)Severability.  Should any provision of this Plan be declared or determined to be invalid, illegal or unenforceable, the validity, legality and enforceability of the remaining provisions shall not in any way be affected or impaired.

(e)Section Headings.  Section headings in this Plan are included for convenience of reference only and shall not be considered part of this Plan for any other purpose.

Section 18.EXECUTION.

To record the adoption of the Plan as set forth herein, effective as of May 5, 2010, Optimer Pharmaceuticals, Inc. has caused its duly authorized officer to execute the same this 5th day of May, 2010.

OPTIMER PHARMACEUTICALS, INC.
By:	/s/ John D. Prunty
Title:	Chief Financial Officer
	and Vice President

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APPENDIX A

OPTIMER PHARMACEUTICALS, INC. SEVERANCE BENEFIT PLAN

BENEFITS FOR ELIGIBLE EMPLOYEES WITH LESS THAN ONE YEAR OF SERVICE

Certain capitalized terms not specifically defined in this Appendix A are defined in the Plan.

Severance benefits to be provided to Eligible Employees under the Optimer Pharmaceuticals, Inc. Amended and Restated Severance Benefit Plan (the “Plan”) who are terminated pursuant to a Covered Termination and who have less than one Year of Service on the date of such termination are as provided on this Appendix A.

1.Conditions to Receipt of Benefits:  Subject to the exceptions set forth in Section 2(b) of the Plan, the Eligible Employee must meet all the requirements set forth in Sections 2(a) and 7(a) of the Plan, including, without limitation, executing a general waiver and release in substantially the form attached to the Plan as Exhibit A, Exhibit B or Exhibit C, as appropriate (the “Release”), within the applicable time period set forth therein and permit such release to become effective in accordance with its terms.  The Company, in its sole discretion, may modify the form of the required general waiver and release to comply with applicable law, and may incorporate such waiver and release into a termination agreement or other agreement with the Eligible Employee.

2.Regular Covered Termination Severance Benefits.  Eligible Employees that are terminated in a Covered Termination that occurs either prior to, or more than 12 months following, a Change of Control, and who have less than one Year of Service on the date of such termination, shall receive the benefits set forth in this Section 2.

(a)Base Salary Continuation Benefit.  Eligible Employees shall be entitled to receive continued Base Salary payments for the time period following a Covered Termination as set forth below next to the respective Eligible Employees’ position in effect at the time of the Covered Termination.

Position	Base Salary Continuation Period
Chief Executive Officer	6 months
Company Officers and Vice Presidents	3 months
All Director levels, Managers, and Non-Managerial Staff with annual Base Salary in excess of $100,000	2 weeks, plus 2 weeks for each Year of Service
Non-Managerial Staff with annual Base Salary of $100,000 or less	2 weeks, plus 1 week for each Year of Service

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(b)Vesting Acceleration for Non-Performance Vesting Equity Awards.  All Non-Performance Vesting Equity Awards granted by the Company to the Eligible Employee (determined as of the date of the Eligible Employee’s Covered Termination) shall be subject to accelerated vesting, if any, for the time period or to the extent set forth below next to the Eligible Employee’s respective position.  If such accelerated vesting is with respect to less than 100% of the Non-Performance Vesting Equity Award, if applicable, such acceleration shall be determined in accordance with the vesting schedule applicable to such Equity Award as if the Eligible Employee had been employed for the additional period of time indicated next to the Eligible Employee’s position as of the date of his or her Covered Termination.

Position	Time Period or Extent of Vesting Acceleration for Non-Performance Vesting Equity Awards
Chief Executive Officer	6 months
Company Officers and Vice Presidents	6 months
All Director levels, Managers, , and Non-Managerial Staff with annual Base Salary in excess of $100,000	None
Non-Managerial Staff with annual Base Salary of $100,000 or less	None

3.Change of Control Covered Termination Severance Benefits.  Eligible Employees that are terminated in a Covered Termination that occurs upon or within twelve (12) months following a Change of Control, and who have less than one Year of Service on the date of such termination shall receive the benefits set forth in this Section 3.

(a)Base Salary Continuation Benefit.  Eligible Employees shall be entitled to receive continued Base Salary payments for the time period following a Covered Termination as set forth below next to the respective Eligible Employees’ position in effect at the time of the Covered Termination.

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Position	Base Salary Continuation Period
Chief Executive Officer	12 months
Company Officers and Vice Presidents	6 months
All Director levels, Managers, and Non-Managerial Staff with annual Base Salary in excess of $100,000	2 weeks, plus 2 weeks for each Year of Service
Non-Managerial Staff with annual Base Salary of $100,000 or less	None

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(b)Vesting Acceleration of Equity Awards.

(1)All Non-Performance Vesting Equity Awards granted by the Company to the Eligible Employee (determined as of the date of the Eligible Employee’s Covered Termination) shall be subject to accelerated vesting for the time period or to the extent set forth below next to the Eligible Employee’s respective position.  If such accelerated vesting is with respect to less than 100% of the Equity Award such acceleration shall be determined in accordance with the vesting schedule applicable to such Equity Award as if the Eligible Employee had been employed for the additional period of time indicated next to the Eligible Employee’s position as of the date of his or her Covered Termination.

Position	Time Period or Extent of Vesting Acceleration for Non-Performance Vesting Equity Awards
Chief Executive Officer	All unvested Equity Awards immediately vest 100%
Company Officers and Vice Presidents	All unvested Equity Awards immediately vest 100%
All Director levels, Managers, and Non-Managerial Staff with annual Base Salary in excess of $100,000	12 months
Non-Managerial Staff with annual Base Salary of $100,000 or less	12 months

(2)Any Performance Vesting Equity Awards (determined as of the date of the Eligible Employee’s Covered Termination) shall be subject to accelerated vesting with respect to 50% of the then unvested shares.

4.Time and Form of Base Salary Continuation Payments.  Subject to the provisions of Section 4 of the Plan, all Base Salary continuation payments shall be paid in accordance with the Company’s standard payroll practices, and shall commence with the first payroll period following the effective date of the Release.  The Company will pay the Eligible Employee the Base Salary continuation severance benefits the Eligible Employee would otherwise have received under the Plan on or prior to such date but for the delay in payment related to the effectiveness of the Release, with the balance of the Base Salary continuation severance benefits being paid as originally scheduled.

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5.Reductions Pursuant to Section 3(c) of the Plan.  The severance benefits set forth in this Appendix A are subject to certain reductions under Section 3(c) of the Plan.

6.Amendment of Appendix A.  The foregoing severance benefits are subject to such change as the Company, pursuant to Section 10(b) of the Plan, may determine in its sole and absolute discretion.  Any such change in severance benefits shall be set forth in a revised version of this Appendix A.

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APPENDIX B

OPTIMER PHARMACEUTICALS, INC. SEVERANCE BENEFIT PLAN

BENEFITS FOR ELIGIBLE EMPLOYEES WITH ONE OR MORE YEARS OF SERVICE

Certain capitalized terms not specifically defined in this Appendix B are defined in the Plan.

Severance benefits to be provided to Eligible Employees under the Optimer Pharmaceuticals, Inc. Amended and Restated Severance Benefit Plan (the “Plan”) who are terminated pursuant to a Covered Termination and who have one or more Years of Service on the date of such termination are as provided on this Appendix B.

1.Conditions to Receipt of Benefits:  Subject to the exceptions set forth in Section 2(b) of the Plan, the Eligible Employee must meet all the requirements set forth in Sections 2(a) and 7(a) of the Plan, including, without limitation, executing a general waiver and release in substantially the form attached to the Plan as Exhibit A, Exhibit B or Exhibit C, as appropriate (the “Release”), within the applicable time period set forth therein and permit such release to become effective in accordance with its terms.  The Company, in its sole discretion, may modify the form of the required general waiver and release to comply with applicable law, and may incorporate such waiver and release into a termination agreement or other agreement with the Eligible Employee.

2.Regular Covered Termination Severance Benefits.  Eligible Employees that are terminated in a Covered Termination that occurs either prior to, or more than 12 months following, a Change of Control, and who have one or more Years of Service on the date of such termination, shall receive the benefits set forth in this Section 2.

(a)Base Salary Continuation Benefit.  Eligible Employees shall be entitled to receive continued Base Salary payments for the time period following a Covered Termination as set forth below next to the respective Eligible Employees’ position in effect at the time of the Covered Termination.

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Position	Base Salary Continuation Period
Chief Executive Officer	12 months
Company Officers	6 months, plus 1 month for each Year of Service above 1 year, up to a maximum of 12 months
Vice Presidents	3 months, plus 1 month for each Year of Service above 3 years, up to a maximum of 9 months
All Director levels, Managers, and Non-Managerial Staff with annual Base Salary in excess of $100,000	2 weeks, plus 2 weeks for each Year of Service, up to a maximum of 36 weeks
Non-Managerial Staff with annual Base Salary of $100,000 or less	2 weeks, plus 1 week for each Year of Service, up to a maximum of 26 weeks

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(b)Vesting Acceleration for Non-Performance Vesting Equity Awards.  All Non-Performance Vesting Equity Awards granted by the Company to the Eligible Employee (determined as of the date of the Eligible Employee’s Covered Termination) shall be subject to accelerated vesting, if any, for the time period or to the extent set forth below next to the Eligible Employee’s respective position.  If such accelerated vesting is with respect to less than 100% of the Equity Award such acceleration shall be determined in accordance with the vesting schedule applicable to such Equity Award as if the Eligible Employee had been employed for the additional period of time indicated next to the Eligible Employee’s position as of the date of his or her Covered Termination.

Position	Time Period or Extent of Vesting Acceleration for Non-Performance Vesting Equity Awards
Chief Executive Officer	24 months
Company Officers and Vice Presidents	12 months
Managers, Executive Directors, and Non-Managerial Staff with annual Base Salary in excess of $100,000	None
Non-Managerial Staff with annual Base Salary of $100,000 or less	None

3.Change of Control Covered Termination Severance Benefits.  Eligible Employees that are terminated in a Covered Termination that occurs upon or within twelve (12) months following a Change of Control, and who have one or more Years of Service on the date of such termination shall receive the benefits set forth in this Section 3.

(a)Base Salary Continuation Benefit.  Eligible Employees shall be entitled to receive continued Base Salary payments for the time period following a Covered Termination as set forth below next to the respective Eligible Employees’ position in effect at the time of the Covered Termination.

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Position	Base Salary Continuation Period
Chief Executive Officer	12 months
Company Officers	12 months
Vice Presidents	9 months
Managers, Executive Directors, and Non-Managerial Staff with annual Base Salary in excess of $100,000	2 weeks, plus 2 weeks for each Year of Service, up to a maximum of 36 weeks
Non-Managerial Staff with annual Base Salary of $100,000 or less	2 weeks, plus 1 week for each Year of Service, up to a maximum of 26 weeks

(b)Equity Vesting Acceleration.

(1)Vesting Acceleration for Non-Performance Vesting Equity Awards.  All Non-Performance Vesting Equity Awards granted by the Company to the Eligible Employee (determined as of the date of the Eligible Employee’s Covered Termination) shall be subject to accelerated vesting for the time period or to the extent set forth below next to the Eligible Employee’s respective position.

Position	Time Period or Extent of Vesting Acceleration for Non-Performance Vesting Equity Awards
Chief Executive Officer	immediately vest 100%
Company Officers and Vice Presidents	immediately vest 100%
Managers, Executive Directors, and Non-Managerial Staff with annual Base Salary in excess of $100,000	immediately vest 100%
Non-Managerial Staff with annual Base Salary of $100,000 or less	immediately vest 100%

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(2)Any Performance Vesting Equity Awards (determined as of the date of the Eligible Employee’s Covered Termination) shall be subject to accelerated vesting, if any, to the extent set forth below.

Years of Service at time of Covered Termination	Extent of Vesting Acceleration for Performance Vesting Equity Award
At least one, but less than 2	60% of unvested shares at time of Covered Termination
At least 2, but less than 3	75% of unvested shares at time of Covered Termination
At least 3, but less than 4	85% of unvested shares at time of Covered Termination
At least 4	100% of unvested shares at time of Covered Termination

4.Time and Form of Base Salary Continuation Payments.  Subject to the provisions of Section 4 of the Plan, all Base Salary continuation payments shall be paid in accordance with the Company’s standard payroll practices, and shall commence with the first payroll period following the effective date of the Release.  The Company will pay the Eligible Employee the Base Salary continuation severance benefits the Eligible Employee would otherwise have received under the Plan on or prior to such date but for the delay in payment related to the effectiveness of the Release, with the balance of the Base Salary continuation severance benefits being paid as originally scheduled.

5.Reductions Pursuant to Section 3(c) of the Plan.  The severance benefits set forth in this Appendix B are subject to certain reductions under Section 3(c) of the Plan.

6.Amendment of Appendix B.  The foregoing severance benefits are subject to such change as the Company, pursuant to Section 10(b) of the Plan, may determine in its sole and absolute discretion.  Any such change in severance benefits shall be set forth in a revised version of this Appendix B.

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APPENDIX C

CERTAIN EQUITY AWARDS

Award Type	Grantee	Shares Covered by Award	Grant Date
Restricted Stock Unit	Pedro Lichtinger	20,000	May 5, 2010
Restricted Stock Unit	Pedro Lichtinger	20,000	May 5, 2010
Restricted Stock Unit	Pedro Lichtinger	20,000	May 5, 2010
Restricted Stock Unit	Pedro Lichtinger	60,000	May 5, 2010
Stock Option	Pedro Lichtinger	80,000	May 5, 2010
Stock Option	Pedro Lichtinger	80,000	May 5, 2010
Stock Option	Pedro Lichtinger	80,000	May 5, 2010
Stock Option	Pedro Lichtinger	240,000	May 5, 2010

For Employees Age 40 or Older

Individual Termination

EXHIBIT A

RELEASE AGREEMENT

I understand and agree completely to the terms set forth in the Optimer Pharmaceuticals, Inc. Severance Benefit Plan (the “Plan”).

I understand that this Release, together with the Plan, constitutes the complete, final and exclusive embodiment of the entire agreement between the Company, affiliates of the Company and me with regard to the subject matter hereof.  I am not relying on any promise or representation by the Company that is not expressly stated therein.  Certain capitalized terms used in this Release are defined in the Plan.

I hereby confirm my obligations under my proprietary information and inventions agreement with the Company.

Except as otherwise set forth in this Release, I hereby generally and completely release the Company and its parents, subsidiaries, successors, predecessors and affiliates, and their partners, members, directors, officers, employees, stockholders, shareholders, agents, attorneys, predecessors, insurers, affiliates and assigns, from any and all claims, liabilities and obligations, both known and unknown, that arise out of or are in any way related to events, acts, conduct, or omissions occurring at any time prior to and including the date I sign this Release.  This general release includes, but is not limited to: (a) all claims arising out of or in any way related to my employment with the Company, or its affiliates, or the termination of that employment; (b) all claims related to my compensation or benefits, including salary, bonuses, commissions, vacation pay, expense reimbursements, severance pay, fringe benefits, stock, stock options, or any other ownership interests in the Company, or its affiliates; (c) all claims for breach of contract, wrongful termination, and breach of the implied covenant of good faith and fair dealing; (d) all tort claims, including claims for fraud, defamation, emotional distress, and discharge in violation of public policy; and (e) all federal, state, and local statutory claims, including claims for discrimination, harassment, retaliation, attorneys’ fees, or other claims arising under the federal Civil Rights Act of 1964 (as amended), the federal Americans with Disabilities Act of 1990 (as amended), the federal Age Discrimination in Employment Act (as amended) (“ADEA”), the federal Employee Retirement Income Security Act of 1974 (as amended), and the California Fair Employment and Housing Act (as amended); provided, however, that nothing in this paragraph shall be construed in any way to release the Company or its affiliates from its obligation to indemnify me pursuant to agreement or applicable law.

I acknowledge that I am knowingly and voluntarily waiving and releasing any rights I may have under the ADEA, and that the consideration given under the Plan for the waiver and release in the preceding paragraph hereof is in addition to anything of value to which I was already entitled.  I further acknowledge that I have been advised by this writing, as required by the ADEA, that:  (a) my waiver and

release do not apply to any rights or claims that may arise after the date I sign this Release; (b) I should consult with an attorney prior to signing this Release (although I may choose voluntarily not do so); (c) I have twenty-one (21) days to consider this Release (although I may choose voluntarily to sign this Release earlier); (d) I have seven (7) days following the date I sign this Release to revoke the Release by providing written notice to an officer of the Company; and (e) this Release shall not be effective until the date upon which the revocation period has expired, which shall be the eighth day after I sign this Release.

I acknowledge that I have read and understand Section 1542 of the California Civil Code which reads as follows: “A general release does not extend to claims which the creditor does not know or suspect to exist in his favor at the time of executing the release, which if known by him must have materially affected his settlement with the debtor.”  I hereby expressly waive and relinquish all rights and benefits under that section and any law of any jurisdiction of similar effect with respect to my release of any claims hereunder.

I acknowledge that to become effective, I must sign and return this Release to the Company so that it is received not later than twenty-one (21) days following the date it is provided to me.

EMPLOYEE

Name:

Date:

For Employees Age 40 or Older

Group Termination

EXHIBIT B

RELEASE AGREEMENT

I understand and agree completely to the terms set forth in the Optimer Pharmaceuticals, Inc. Severance Benefit Plan (the “Plan”).

I understand that this Release, together with the Plan, constitutes the complete, final and exclusive embodiment of the entire agreement between the Company, affiliates of the Company and me with regard to the subject matter hereof.  I am not relying on any promise or representation by the Company that is not expressly stated therein.  Certain capitalized terms used in this Release are defined in the Plan.

I hereby confirm my obligations under my proprietary information and inventions agreement with the Company.

Except as otherwise set forth in this Release, I hereby generally and completely release the Company and its parents, subsidiaries, successors, predecessors and affiliates, and their partners, members, directors, officers, employees, stockholders, shareholders, agents, attorneys, predecessors, insurers, affiliates and assigns, from any and all claims, liabilities and obligations, both known and unknown, that arise out of or are in any way related to events, acts, conduct, or omissions occurring at any time prior to and including the date I sign this Release.  This general release includes, but is not limited to: (a) all claims arising out of or in any way related to my employment with the Company, or its affiliates, or the termination of that employment; (b) all claims related to my compensation or benefits, including salary, bonuses, commissions, vacation pay, expense reimbursements, severance pay, fringe benefits, stock, stock options, or any other ownership interests in the Company, or its affiliates; (c) all claims for breach of contract, wrongful termination, and breach of the implied covenant of good faith and fair dealing; (d) all tort claims, including claims for fraud, defamation, emotional distress, and discharge in violation of public policy; and (e) all federal, state, and local statutory claims, including claims for discrimination, harassment, retaliation, attorneys’ fees, or other claims arising under the federal Civil Rights Act of 1964 (as amended), the federal Americans with Disabilities Act of 1990 (as amended), the federal Age Discrimination in Employment Act (as amended) (“ADEA”), the federal Employee Retirement Income Security Act of 1974 (as amended), and the California Fair Employment and Housing Act (as amended); provided, however, that nothing in this paragraph shall be construed in any way to release the Company or its affiliates from its obligation to indemnify me pursuant to agreement or applicable law.

I acknowledge that I am knowingly and voluntarily waiving and releasing any rights I may have under the ADEA, and that the consideration given under the Plan for the waiver and release in the preceding paragraph hereof is in addition to anything of value to which I was already entitled.  I further acknowledge that I have been advised by this writing, as required by the ADEA, that:  (a) my waiver and

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release do not apply to any rights or claims that may arise after the date I sign this Release; (b) I should consult with an attorney prior to signing this Release (although I may choose voluntarily not to do so); (c) I have forty-five (45) days to consider this Release (although I may choose voluntarily to sign this Release earlier); (d) I have seven (7) days following the date I sign this Release to revoke the Release by providing written notice to an office of the Company; (e) this Release shall not be effective until the date upon which the revocation period has expired, which shall be the eighth day after I sign this Release; and (f) I have received with this Release a detailed list of the job titles and ages of all employees who were terminated in this group termination and the ages of all employees of the Company in the same job classification or organizational unit who were not terminated.

I acknowledge that I have read and understand Section 1542 of the California Civil Code which reads as follows: “A general release does not extend to claims which the creditor does not know or suspect to exist in his favor at the time of executing the release, which if known by him must have materially affected his settlement with the debtor.”  I hereby expressly waive and relinquish all rights and benefits under that section and any law of any jurisdiction of similar effect with respect to my release of any claims hereunder.

I acknowledge that to become effective, I must sign and return this Release to the Company so that it is received not later than forty-five (45) days following the date it is provided to me.

EMPLOYEE

Name:

Date:

2

For Employees Under Age 40

Individual and Group Termination

EXHIBIT C

RELEASE AGREEMENT

I understand and agree completely to the terms set forth in the Optimer Pharmaceuticals, Inc. Severance Benefit Plan (the “Plan”).

I understand that this Release, together with the Plan, constitutes the complete, final and exclusive embodiment of the entire agreement between the Company, affiliates of the Company and me with regard to the subject matter hereof.  I am not relying on any promise or representation by the Company that is not expressly stated therein.  Certain capitalized terms used in this Release are defined in the Plan.

I hereby confirm my obligations under my proprietary information and inventions agreement with the Company.

Except as otherwise set forth in this Release, I hereby generally and completely release the Company and its parents, subsidiaries, successors, predecessors and affiliates, and their partners, members, directors, officers, employees, stockholders, shareholders, agents, attorneys, predecessors, insurers, affiliates and assigns, from any and all claims, liabilities and obligations, both known and unknown, that arise out of or are in any way related to events, acts, conduct, or omissions occurring at any time prior to and including the date I sign this Release.  This general release includes, but is not limited to: (a) all claims arising out of or in any way related to my employment with the Company, or its affiliates, or the termination of that employment; (b) all claims related to my compensation or benefits, including salary, bonuses, commissions, vacation pay, expense reimbursements, severance pay, fringe benefits, stock, stock options, or any other ownership interests in the Company, or its affiliates; (c) all claims for breach of contract, wrongful termination, and breach of the implied covenant of good faith and fair dealing; (d) all tort claims, including claims for fraud, defamation, emotional distress, and discharge in violation of public policy; and (e) all federal, state, and local statutory claims, including claims for discrimination, harassment, retaliation, attorneys’ fees, or other claims arising under the federal Civil Rights Act of 1964 (as amended), the federal Americans with Disabilities Act of 1990 (as amended), the federal Age Discrimination in Employment Act (as amended) (“ADEA”), the federal Employee Retirement Income Security Act of 1974 (as amended), and the California Fair Employment and Housing Act (as amended); provided, however, that nothing in this paragraph shall be construed in any way to release the Company or its affiliates from its obligation to indemnify me pursuant to agreement or applicable law.

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I acknowledge that I have read and understand Section 1542 of the California Civil Code which reads as follows: “A general release does not extend to claims which the creditor does not know or suspect to exist in his favor at the time of executing the release, which if known by him must have materially affected his settlement with the debtor.”  I hereby expressly waive and relinquish all rights and benefits under that section and any law of any jurisdiction of similar effect with respect to my release of any claims hereunder.

I acknowledge that to become effective, I must sign and return this Release to the Company so that it is received not later than fourteen (14) days following the date it is provided to me.

EMPLOYEE

Name:

Date:

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EX-99.4

Exhibit 99.4

Optimer Pharmaceuticals Appoints Pedro Lichtinger as President and CEO to Succeed Michael N. Chang, Ph.D., Who Will Serve as Chairman of the Board

SAN DIEGO — May 6, 2010 - Optimer Pharmaceuticals, Inc. (NASDAQ: OPTR) today announced that Pedro Lichtinger has been appointed President and Chief Executive Officer of the Company as well as to the Board of Directors.  Pedro Lichtinger joins Optimer with more than 30 years of global business experience in the pharmaceutical and animal health industries.    Michael N. Chang, Ph.D., co-founder of Optimer, who has led the Company as President and Chief Executive Officer since inception, will serve as Chairman of the Board of Directors and as a consultant.

“Pedro Lichtinger is an exceptional fit for the role of President and CEO of Optimer Pharmaceuticals.  Pedro’s successful track record in the global pharmaceutical industry will benefit us as we focus on the commercialization of our lead drug candidate, fidaxomicin, “ said Michael N. Chang, Ph.D.  “His experience leading research and development and commercial operations will be invaluable.  I look forward to my new role as Chairman of the Board of Optimer and working with Pedro on matters of strategic importance to the Company.”

Pedro Lichtinger previously served as an executive of Pfizer, Inc. from 1995 to 2009, most recently as President of Pfizer’s Global Primary Care Business Unit, where he oversaw operations in North America, Europe, Korea, and Australia with revenues of $23 billion, 15,000 employees, and more than 60 development projects.  Prior to this position, he served as Pfizer’s Area President in Europe overseeing all pharmaceutical products including primary care, oncology, specialty and generic.  Prior to this position he served as Pfizer’s President of Global Animal Health Business, and Regional President Europe Animal Health.  Before joining Pfizer, he was an executive of Smith Kline Beecham, last serving as Senior Vice President Europe Animal Health.  Mr. Lichtinger holds an MBA degree from the Wharton School of Business and an Industrial Engineering degree from the National University of Mexico. Mr. Lichtinger currently serves on the board of directors of BioTime, Inc., a publicly-traded biotechnology company focused on blood plasma volume expanders and regenerative medicine.

“Optimer has two late stage product candidates including an exciting opportunity with fidaxomicin to address the significant unmet medical need in Clostridium difficile infection,” said Mr. Lichtinger.  “I look forward to working with Michael in his new role as Chairman and with the Optimer team to lead the Company to the next phase of growth.”

The Company also announced that on May 5, 2010 Alain B. Schreiber, M.D., a Managing Partner at ProQuest Investments, stepped down from his position as a director of the Company.  Dr. Schreiber had served on the Company’s Board since 2001, advising Optimer as a private company and then working with Optimer in its transition to a public company. Dr. Schreiber will continue to follow his pursuits in venture capital, serving on the boards of many privately held companies.  Dr. Schreiber’s departure is not related to relations with the Company’s Board members or with the Company.

“We would like to express our gratitude to Alain for his years of dedicated service to the Company.  His board experience and leadership have been invaluable as the Company has grown from a private company and transitioned to a public company,” said Michael N. Chang, Ph.D.  “We wish him great success in his future endeavors.”

About Optimer Pharmaceuticals

Optimer Pharmaceuticals, Inc. is a biopharmaceutical company focused on discovering, developing and commercializing innovative anti-infectives to treat serious infections and address unmet medical needs. Optimer has two late-stage anti-infective product candidates under development. Fidaxomicin is a narrow spectrum antibiotic being developed for the treatment of Clostridium difficile infection. Optmer has reported positive top-line results from two Phase 3 trials of fidaxomicin.  Pruvel™ is a prodrug in the fluoroquinolone class of antibiotics being developed as a treatment for infectious diarrhea.  Optimer has also successfully completed two Phase 3 trials with Pruvel.  Additional information can be found at http://www.optimerpharma.com.

Forward Looking Statements

Statements included in this press release that are not a description of historical facts are forward-looking statements, including without limitation all statements related to the anticipated development or commercialization of Optimer’s product candidates and the future roles and contributions of Pedro Lichtinger and Michael N. Chang at Optimer. Words such as “believes,” “anticipates,” “plans,” “expects,” “intend,” “will,” “goal” and similar expressions are intended to identify forward-looking statements. The inclusion of forward-looking statements should not be regarded as a representation by Optimer that any of its plans will be achieved. Actual results may differ materially from those set forth in this release due to the risks and uncertainties inherent in Optimer’s business including, without limitation, risks relating to: the timing, progress and likelihood of success of its product research and development programs, the timing and status of its preclinical and clinical development of potential drugs, the timing and status of regulatory filings, receipt of regulatory approvals and commercialization efforts and other risks detailed in Optimer’s filings with the Securities and Exchange Commission.

Contacts

Optimer Pharmaceuticals, Inc.

Christina Donaghy, Corporate Communications Manager

John D. Prunty, Chief Financial Officer & VP Finance

858-909-0736

Canale Communications, Inc.

Jason I. Spark, Senior Vice President

619-849-6005