Celldex Therapeutics (CLDX) 10-Q 2007 Q3 Quarterly report

Exhibit 32.1

SECTION 1350 CERTIFICATIONS

The undersigned officers of AVANT Immunotherapeutics, Inc. (the “Company”) hereby certify to their knowledge and in their respective capacities that the Company’s quarterly report on Form 10-Q to which this certification is attached (the “Report”), as filed with the Securities and Exchange Commission on the date hereof, fully complies with the requirements of Section 13(a) or 15(d), as applicable, of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and that the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: November 7, 2007	By:	/s/ UNA S. RYAN
	Name:	Una S. Ryan, Ph.D.
	Title:	President and Chief Executive Officer
Date: November 7, 2007	By:	/s/ AVERY W. CATLIN
	Name:	Avery W. Catlin
	Title:	Senior Vice President and
		Chief Financial Officer

This certification shall not be deemed “filed” for any purpose, nor shall it be deemed to be incorporated by reference into any filing under the Securities Act of 1933 or the Exchange Act.