UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 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): August 18, 2008

OPTIMER PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

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

10110 Sorrento Valley Road, Suite C

San Diego, CA 92121

(Address of principal executive offices, including zip code)

Registrant’s telephone number, including area code: (858) 909-0736

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:

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

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

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

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

Item 1.01

Entry into a Material Definitive Agreement.

On August 18, 2008, Optimer Pharmaceuticals, Inc. (“Optimer”) entered into an office lease agreement (the “Lease”) with Trizec Sorrento Towers, LLC for approximately 7,663 square feet of additional office space in San Diego, California. The initial forty-month term of the Lease commences on the earlier of (i) the date on which Optimer first commences to conduct business in the premises, or (ii) the date on which the premises is ready for occupancy, and expires on November 30, 2011. The total minimum monthly rent payable by Optimer during the initial term is approximately $900,000. In addition, Optimer has the option to extend the Lease for an additional sixty-month term, which would commence upon the expiration of the initial forty-month term. In the event Optimer chooses to extend the term of the Lease, the minimum monthly rent payable for the additional sixty-month term will be determined according to the then-prevailing market annual rental rate.

A copy of the Lease is attached as Exhibit 99.1 hereto and is incorporated herein by reference.

Item 9.01

Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No.		Description

99.1		Office Lease, dated August 18, 2008, by and between Optimer Pharmaceuticals, Inc. and Trizec Sorrento Towers, LLC.

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.

Dated: August 21, 2008	By:	/s/ John D. Prunty
		John D. Prunty Chief Financial Officer (Duly Authorized Officer and Principal Financial and Accounting Officer)