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Exhibit 10.16    
    


[LOGO]


        June 15,
2006 


Kevin
Poulos

[address] 


Dear
Kevin: 


It
is with great pleasure that I offer you the position of Vice President, Marketing and Sales with Optimer Pharmaceuticals, Inc. reporting to Dr. Michael N. Chang. 


Associated
with this opportunity, we offer the following compensation and benefits: 



	1.
	Annual
Salary: $180,000 US Dollars, paid semi-monthly.



	2.
	Optimer
offers a competitive benefit package to you and your eligible dependents that includes Medical, Dental, 401(k), Vision, and Group Term Life Insurance.



	3.
	Stock
Options: The Company will provide the Executive with the following long-term incentive compensation arrangement in accordance with the terms of Company's 1998
Incentive Stock Option Plan ("Stock Option Plan"). 





Following
commencement of your employment and pending approval by Optimer's Board of Directors, you will be granted an Option to purchase 160,000 shares of Optimer Pharmaceuticals, Inc.
Common Stock at the current fair market value as determined by the Board. The vesting schedule for this Option is over a four year period with a one-year cliff and monthly thereafter. 



	4.
	Optimer
has 11 official holidays. In addition, you will begin accruing paid vacation at a rate of 17 days per year (5.67 hours per pay period) beginning with your
first pay period as a full-time employee. You will also be provided with 5 days of sick time per year.



	5.
	Severance/Acceleration:



	a.
	If
your employment is terminated by the Company without Cause (as defined below) (other than by reason of death or Disability (as defined in
Section 22(e)(3) of the Internal Revenue Code of 1986, as amended)), then you shall be entitled to receive, subject to your execution of a general release of claims containing customary
provisions and reasonably acceptable to the Company and your continued compliance with the provisions of your Employee Proprietary Information Agreement, continued payment of your then current base
salary pursuant to the Company's standard payroll policies and subject to applicable withholding for a three month period following the date of such termination.



	b.
	If
your employment is terminated by the Company without Cause (other than by reason of death or Disability) within 12 months after a Change of Control (as defined below),
then you shall be entitled to receive, subject to your execution of a general release of claims containing customary provisions and reasonably acceptable to the Company and your continued compliance
with the provisions of your Employee Proprietary Information Agreement, continued payment of your then current base salary pursuant to the Company's standard payroll policies and subject to applicable
withholding for a six month period following the date of such termination, and all of your unvested options shall become immediately fully vested.



	c.
	If
you are terminated without Cause, you shall only be entitled to the benefits set forth in either Section 5(a) or Section 5(b). 













	d.
	For
purposes herein, "Cause" shall mean (i) failure to perform your assigned duties or responsibilities as a service provider (other than a failure resulting from the your
Disability) after notice thereof from the Company describing your failure to perform such duties or responsibilities; (ii) your engaging in any act of dishonesty, fraud or misrepresentation;
(iii) your violation of any federal or state law or regulation applicable to the business of the Company or its affiliates; (iv) your breach of any confidentiality agreement or invention
assignment agreement between you and the Company (or any affiliate of the Company); or (v) your being convicted of, or entering a plea of nolo
contendere to, any crime or committing any act of moral turpitude.



	e.
	For
purposes herein, "Change of Control" shall mean (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).






	6.
	Relocation
and housing search in San Diego.    Optimer will reimburse you for reasonable costs associated with moving your household goods to San Diego. Optimer will
arrange and pay for your travel to San Diego on up to two occasions to assist with your search for a new residence and for your airfare when you travel to San Diego to move. In addition, if needed,
Optimer will reimburse you for up to 30 days temporary housing in San Diego. You may have a taxable event for funds reimbursed towards temporary living expenses. It is recommended you seek the
advice of a tax professional.



	7.
	Bonus
Program. Currently Optimer does not have a bonus program, but we will be recommending a Company wide annual bonus program for approval by Optimer's Board of Directors in 2006.
For Vice President level positions, approval will be requested for a cash bonus of up to 20% (twenty percent) of Executive's annual salary at that time. The Compensation Committee will be asked to
waive pro-ration calculation for your first year bonus. 




Start
date is scheduled for on or before July 17, 2006. 


You
should be aware that your employment with the Company is for no specified period and constitutes at-will employment. As a result, you are free to resign at any time, for any reason or
for no reason. Similarly, the Company is free to conclude its employment relationship with you at any time, with or without cause, and with or without notice. 


For
purposes of federal immigration law, you will be required to provide to the Company documentary evidence of your identity and eligibility for employment in the United States. Such
documentation must be provided to us within three (3) business days of your date of hire, or our employment relationship with you may be terminated. 



As
a Company employee, you will be expected to abide by company rules and regulations. You will be specifically required to sign an acknowledgment that you have read and understand the company rules
of conduct, which is included in our employee handbook. You will also be expected to sign and comply with an Employee Proprietary Information Agreement, which requires, among other provisions, the
assignment of patent rights to any invention made during your employment at the Company and non-disclosure of proprietary information. You will receive an electronic copy of both our
employee handbook and our Employee Proprietary Information Agreement for your review with this employment offer. 



We
look forward to working with you as part of the Optimer team. If you accept the position, please sign and return your acceptance letter to Diane McCarty, no later than June 20, 2006, If you
have any questions, please e-mail or call me or Diane at your convenience. 


Best
Regards, 


Michael
Chang

Chief Executive Officer 



	I accept the offer as stipulated above:	 	
	 	

	 	 	Signature	 	Date













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Exhibit 10.16