Exhibit 31.1
CERTIFICATION
I, Anthony S. Marucci, certify that:
1. I have reviewed this Amendment No. 1 to Annual Report on Form 10-K/A of Celldex Therapeutics, Inc.; and
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.
| /s/ ANTHONY S. MARUCCI |
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| Anthony S. Marucci |
| President and Chief Executive Officer |
Dated: March 31, 2010