10-Q/A

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 10-Q/A

Amendment No. 1

(Mark One)

x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934.

  For the quarterly period ended March 31, 2004.

OR

¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934.

  For the transition period from                      to                     .

Commission File Number:

000-31633

Kosan Biosciences Incorporated

(Exact name of registrant as specified in its charter)

Delaware (State or other jurisdiction of incorporation or organization) 94-3217016 (I.R.S. Employer Identification No.)

3832 Bay Center Place, Hayward, California 94545

(address of principal executive offices)

(510) 732-8400

(Registrant’s telephone number, including area code)

Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 (the “Exchange Act”) during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.  Yes  x  No  ¨

Indicate by check mark whether the Registrant is an accelerated filed (as defined in Rule 12b-2 of the Exchange Act). Yes  x  No  ¨

Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practicable date: Common Stock, $.001 par value; 28,922,010 shares outstanding at April 30, 2004.

EXPLANATORY NOTE

This amendment on Form 10-Q/A amends Item 6 to Part II of the Quarterly Report of Kosan Biosciences Incorporated (the “Company”) on Form 10-Q previously filed for the quarter ended March 31, 2004 (the “Prior Report”), and together these two filings constitute the Quarterly Report of the Company for the quarter ended March 31, 2004 and are referred to herein as the “quarterly report”.

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PART II – OTHER INFORMATION

Item 6. Exhibits and Reports on Form 8-K

(a) Exhibits

Exhibit No.
3.1	Amended and Restated Certificate of Incorporation.(1)
3.2	Amended and Restated Bylaws of Registrant.(2)
4.1	Form of Specimen Common Stock Certificate.(3)
31.1	Certification required by Rule 13a-14(a) or Rule 15d-14(a).
31.2	Certification required by Rule 13a-14(a) or Rule 15d-14(a).
32.1	Certification by the Chief Executive Officer and the Chief Financial Officer of Kosan Biosciences Incorporated, as required by Rule 13a-14(b) or Rule 15d-14(b) and Section 1350 of Chapter 63 of Title 18 of the United Stated Code (18 U.S.C. 1350).(4)

(b) Reports on Form 8-K

On February 26, 2004, we filed a Current Report on Form 8-K, in connection with the announcement of the Company’s financial results for the three and twelve months ended December 31, 2003.

(1) Incorporated herein by reference to an exhibit of our Quarterly Report on Form 10-Q for the period ended June 30, 2001.

(2) Incorporated herein by reference to an exhibit of our Quarterly Report on Form 10-Q for the period ended June 30, 2003.

(3) Incorporated herein by reference to an exhibit of our Registration Statement on Form S-1, Registration No. 333-33732.

(4) Previously filed with our Quarterly Report on Form 10-Q, which this Quarterly Report on Form 10-Q/A amends.

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SIGNATURES

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

	Kosan Biosciences Incorporated
May 18, 2004	By:	/s/    Daniel V. Santi, M.D., Ph.D.
		Daniel V. Santi, M.D., Ph.D. Chairman and Chief Executive Officer
May 18, 2004	By:	/s/    Susan M. Kanaya
		Susan M. Kanaya Senior Vice President, Finance, Chief Financial Officer and Secretary

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EXHIBIT INDEX

Exhibit No.
3.1	Amended and Restated Certificate of Incorporation.(1)
3.2	Amended and Restated Bylaws of Registrant.(2)
4.1	Form of Specimen Common Stock Certificate.(3)
31.1	Certification required by Rule 13a-14(a) or Rule 15d-14(a).
31.2	Certification required by Rule 13a-14(a) or Rule 15d-14(a).
32.1	Certification by the Chief Executive Officer and the Chief Financial Officer of Kosan Biosciences Incorporated, as required by Rule 13a-14(b) or Rule 15d-14(b) and Section 1350 of Chapter 63 of Title 18 of the United Stated Code (18 U.S.C. 1350).(4)

(1) Incorporated herein by reference to an exhibit of our Quarterly Report on Form 10-Q for the period ended June 30, 2001.

(2) Incorporated herein by reference to an exhibit of our Quarterly Report on Form 10-Q for the period ended June 30, 2003.

(3) Incorporated herein by reference to an exhibit of our Registration Statement on Form S-1, Registration No. 333-33732.

(4) Previously filed with our Quarterly Report on Form 10-Q, which this Quarterly Report on Form 10-Q/A amends.

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EX-31.1

Exhibit 31.1

I, Daniel V. Santi, certify that:

1. I have reviewed this quarterly report on Form 10-Q/A of Kosan Biosciences Incorporated;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officers and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(c) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrants other certifying officers and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: May 18, 2004

/s/    Daniel V. Santi, M.D., Ph.D.

Daniel V. Santi, M.D., Ph.D.

Chairman and Chief Executive Officer

EX-31.2

Exhibit 31.2

I, Susan M. Kanaya, certify that:

1. I have reviewed this quarterly report on Form 10-Q/A of Kosan Biosciences Incorporated;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officers and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(c) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrants other certifying officers and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: May 18, 2004

/s/    Susan M. Kanaya

Susan M. Kanaya

Senior Vice President, Finance, Chief Financial officer and Secretary