Exhibit 32.1
CERTIFICATION PURSUANT TO
SECTION 1350, CHAPTER 63 OF TITLE 18, UNITED STATES CODE,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
Pursuant to Section 1350, Chapter 63 of Title 18, United States Code, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, the undersigned, as principal executive officer and principal financial officer of CombinatoRx, Incorporated (the “Company”), do hereby certify that to their knowledge:
1) the Company’s Form 10-K for the fiscal year ended December 31, 2006 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and
2) the information contained in the Company’s Form 10-K for the fiscal year ended December 31, 2006 fairly presents, in all material respects, the financial condition and results of operations of the Company.
| | /s/ALEXIS BORISY |
| | Alexis Borisy |
| | President and Chief Executive Officer |
| | (principal executive officer) |
| | |
| | /s/ROBERT FORRESTER |
| | Robert Forrester |
| | Executive Vice President and Chief Financial Officer |
| | (principal financial officer) |
Dated: March 15, 2007
