8-K

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): April 14, 2008

Kosan Biosciences Incorporated

(Exact name of registrant as specified in its charter)

Delaware

(State or other jurisdiction of incorporation)

000-31633	94-3217016
(Commission File Number)	(IRS Employer Identification No.)

3832 Bay Center Place, Hayward, CA 94545

(Address of principal executive offices, including Zip Code)

Registrant’s telephone number, including area code: (510) 732-8400

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 8.01. Other Events.

On April 14, 2008, Kosan Biosciences Incorporated announced the initiation of a Phase 2 trial of Epothilone KOS-1584 in patients with non-small cell lung cancer.

A copy of the press release issued in connection with this announcement is attached as Exhibit 99.1 to this current report and is incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

(d)     Exhibits

Number	Description
99.1	Press Release of Kosan Biosciences Incorporated, dated April 14, 2008

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.

	KOSAN BIOSCIENCES INCORPORATED
Dated: April 15, 2008	By:	/s/ Jonathan K. Wright
		Jonathan K. Wright
		Senior Vice President and General Counsel

EXHIBIT INDEX

Number	Description
99.1	Press Release of Kosan Biosciences Incorporated, dated April 14, 2008

EX-99.1

Exhibit 99.1

KOSAN BIOSCIENCES

Contact:

Jane Green

VP, Corporate Communications

510.731.5335 (office)

415.652.4819 (mobile)

green@kosan.com

FOR IMMEDIATE RELEASE

KOSAN INITIATES PHASE 2 TRIAL OF EPOTHILONE KOS-1584

IN NON-SMALL CELL LUNG CANCER

HAYWARD, CA – April 14, 2008 - Kosan Biosciences Incorporated (Nasdaq: KOSN) today announced that the Phase 2 trial of epothilone KOS-1584 in patients with non-small cell lung cancer has been initiated. The Phase 2 trial is an open-label, multi-center, monotherapy study of KOS-1584 in patients with measurable advanced or metastatic non-small cell lung cancer who have previously received only one prior chemotherapy regimen. The primary endpoint of the Phase 2 trial is objective response rate. Secondary endpoints include progression-free survival, time to progression, time to treatment failure, time to response, duration of response and overall survival. KOS-1584 will be administered via a 3-hour intravenous infusion weekly for two weeks out of every three weeks at a dose of 25 mg/m². The Phase 2 trial will enroll up to 50 patients in a two-stage Simon design.

“We have been impressed by the breadth and level of activity and tolerability we have observed with KOS-1584 in our Phase 1 trials and believe that KOS-1584 has competitive potential in the emerging epothilone class of anticancer agents,” said Helen S. Kim, Kosan’s President and Chief Executive Officer. “Kosan’s epothilone strategy is to advance KOS-1584 to its next inflection point while seeking a corporate partner to conduct a registration program and advance our preclinical product candidate, KOS-1803, into clinical development. We believe that KOS-1584’s therapeutic profile and potential for near-term commercialization enhance its value for potential pharmaceutical collaborators.”

KOS-1584 is a member of a class of cytotoxic macrolides (epothilones) capable of causing mitotic arrest by polymerization of cellular microtubules. Since microtubules are essential for mitosis, motility, secretion and proliferation, the observed antitumor effects of epothilones have been attributed to their ability to initiate cell death by inhibiting such processes. KOS-1584 has demonstrated in vitro cytotoxicity, more potent or equipotent to that of Taxol^® (paclitaxel) in a panel of human cell lines. KOS-1584 has shown significant antitumor activity in a range of xenograft models, including non-small cell lung cancer models resistant to paclitaxel and those expressing multidrug resistance. A long elimination half-life was seen in Phase I trials. KOS-1584 has demonstrated antitumor activity and favorable tolerability in Phase 1 trials in patients with solid tumors, including substantial tumor shrinkage measured by objective responses in non-small cell lung, ovarian and pancreatic cancers, as well as durable stable disease in many additional tumors.

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About Kosan

Kosan Biosciences is a biotechnology company advancing two new classes of anticancer agents through clinical development – a Hsp90 (heat shock protein 90) inhibitor and an epothilone. Hsp90 inhibitors have a novel mechanism of action targeting multiple pathways involved in cancer cell growth and survival. Tanespimycin (KOS-953) is being tested in combination with Velcade^® (bortezomib) in patients with multiple myeloma in a clinical program called TIME. Tanespimycin is also being studied in HER2-positive metastatic breast cancer in combination with Herceptin^® (trastuzumab). Epothilones inhibit cell division with a mechanism of action similar to taxanes, one of the most successful classes of anti-tumor agents. KOS-1584 is in a Phase 2 clinical trial in patients with non-small cell lung cancer. Kosan’s motilin agonist compound, KOS-2187, licensed to Pfizer for development in gastroesophagel reflux disease, is in a Phase 1 trial. For additional information on Kosan Biosciences, please visit the company’s website at http://www.kosan.com.

This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995 (the “Act”). Such forward-looking statements include but are not limited to statements regarding the further development and potential safety, efficacy, regulatory status, commercial potential and other characteristics of Kosan’s product candidates; the continuation of current clinical trials; the initiation of additional clinical trials and the timing thereof and the use of Kosan’s financial resources. Words such as “will,” “expect,” “believe,” “may,” “intend,” “plan,” “potential” and similar expressions are intended to identify forward-looking statements. Any statements contained in this press release that are not statements of historical fact may be deemed to be forward-looking statements. These forward-looking statements are based upon Kosan’s current expectations. Forward-looking statements involve risks and uncertainties. Kosan’s actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, risks related to the uncertain progress and results of Kosan’s preclinical and clinical testing, including the risks that studies and trials may not demonstrate safety and efficacy sufficient to initiate clinical trials on the timing currently anticipated, or at all, continue clinical development, obtain the requisite regulatory approvals or result in a marketable product; the conduct of clinical trials; manufacturing; regulatory approval requirements and process; the effort and expense necessary for further development of Kosan’s product candidates, including the costs of bortezomib; intellectual property matters, including Kosan’s ability to obtain valid and enforceable patents covering its product candidates; Kosan’s dependence on its collaboration with Pfizer for development of its motilin agonist product candidate; Kosan’s need for additional financing and Kosan’s strategy to enter into partnering or licensing arrangements. These and other risk factors are discussed under “Risk Factors” in Kosan’s Annual Report on Form 10-K for the year ended December 31, 2007 and other periodic filings with the SEC. Kosan expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein.

Velcade^® (bortezomib) is a registered trademark of Millennium Pharmaceuticals, Inc.

Herceptin^® (trastuzumab) is a registered trademark of Genentech, Inc.

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