AGREEMENT

Exhibit B

AGREEMENT

     Pursuant to Rule 13d-1(k)(1) promulgated pursuant to the Securities Exchange Act of 1934, as amended, the undersigned agree that the attached Schedule 13D/A is being filed on behalf of each of the undersigned.

July 18, 2005

		VENROCK ASSOCIATES by a General Partner VENROCK ASSOCIATES III, L.P., by its General Partner, Venrock Management III LLC VENROCK ENTREPRENEURS FUND III, L.P. by its General Partner, VEF Management III LLC
		By:		/s/ Xxxxx X. Xxxxxxx
				Name:		Xxxxx X. Xxxxxxx
				Title:		As a General Partner or Member