Affymax, Inc. 4001 Miranda Avenue Palo Alto, California 94304 Attn: Robert Naso, Ph.D. Executive Vice President, R&D Re: Second Extension of Letter Agreement for TFPI Product Candidates Dear Dr. Naso:

Exhibit 10.29

[EntreMed Logo] xxx.xxxxxxxx.xxx

December 19, 2005

Affymax, Inc.
0000 Xxxxxxx Xxxxxx
Xxxx Xxxx, Xxxxxxxxxx 00000
Attn: Xxxxxx Xxxx, Ph.D.
          Executive Vice President, R&D

Re:     Second Extension of Letter Agreement for TFPI Product Candidates

Dear Xx. Xxxx:

        I am writing with reference to the Letter Agreement between Affymax, Inc. ("Affymax") and EntreMed, Inc. ("EntreMed") dated as of September 20, 2004 (together with each of the exhibits thereto, the "Letter Agreement") and the related Extension Letter dated as of August 23, 2005 between Affymax and EntreMed (the "First Extension Letter"), pursuant to which EntreMed and Affymax agreed to extend the Term of the Letter Agreement to December 31, 2005. All capitalized terms used but not defined herein shall have the meaning given to such terms in the Letter Agreement.

        As both parties would like to continue the Research Collaboration under the Letter Agreement, pending our current negotiations relating to a Co-Development and Co-Commercialization Agreement, the Term of the Letter Agreement is agreed to be further extended until February 28, 2006. Both Affymax and XxxxxXxx acknowledge and agree that, except as otherwise set forth herein, all terms and conditions of the Letter Agreement and the First Extension Letter remain unchanged and in full force and effect.

        Please confirm your agreement to extend the Term of the Letter Agreement (including, without limitation, the period to enter into a Co-Development and Co-Commercialization Agreement) to February 28, 2006, by countersigning this Letter and returning the countersigned letter to EntreMed.

		Very truly yours,
		EntreMed, Inc.
		By:	/s/ Xxxx Xxxxxxx Name: Xxxx Xxxxxxx Title: Vice President, Corporate Development

ACCEPTED AND AGREED:
Affymax, Inc.
By:	/s/ Xxxxxx Xxxx Name: Xxxxxx Xxxx Title: Exec. V.P. Date: 20 Dec 2005

EntreMed, Inc. / 0000 Xxxxxxx Xxxxxx Xxxxx / Xxxxxxxxx, XX 00000
000.000.0000 phone / 000.000.0000 fax