Contract

EXHIBIT 10.61

[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

June 12, 2008

Xx. Xxxxx Xxxxxxx

Cystic Fibrosis Foundation Therapeutics, Inc.

0000 Xxxxxxxxx Xxxx

Xxxxxxxx, XX 00000

Dear Xx. Xxxxxxx:

The purpose of this letter (“Letter”) is to further amend the Study Funding Agreement, between the undersigned parties, dated June 17, 2003, as amended (the “Agreement”). By signing below, the undersigned parties agree to the following:

In Section 8.1(c) of the Agreement, [ * ] shall be replaced with [ * ].

All other terms and provisions of the Agreement shall remain unchanged and are in full force and effect.

XXXXXX-XXXX PHARMACEUTICALS, INC.
By:		/s/    Xxxxxx X. Xxxxx				Date: 6/12/08
		Xxxxxx X. Xxxxx
		Interim Chief Financial Officer,
		Chief Accounting Officer and
		Vice President, Operations

Agreed to and Acknowledged by:

CYSTIC FIBROSIS FOUNDATION THERAPEUTICS, INC.
By:		/s/    Xxxxxx X. Xxxxx				Date: 6/25/08
		Xxxxxx X. Xxxxx, Ph.D.
		President and CEO