Exhibit 24 - POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS, that each person whose
signature appears below hereby constitutes and appoints Raymond
Charest, Alexia Pearsall and Jonathan J. Fleming, and each of
them, with full power to act without the other, his true and
lawful attorney-in-fact and agent, with full power of
substitution, for him and in his name, place and stead, in any
and all capacities (until revoked in writing) to sign any and
all instruments, certificates and documents required to be
executed on behalf of himself as an individual or in his
capacity as a general partner or authorized signatory, as the
case may be, on behalf of any of Oxford Bioscience Partners
IV L.P., mRNA II L.P., or OBP Management IV L.P., pursuant to
section 13 or 16 of the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), and any and all regulations
promulgated thereunder and to file the same, with all
exhibits thereto, and any other documents in connection
therewith, with the Securities and Exchange Commission, and
with any other entity when and if such is mandated by the
Exchange Act or by the By-laws of the National Association of
Securities Dealers, Inc., granting unto said attorney-in-fact
and agent full power and authority to do and perform each and
every act and thing requisite and necessary fully to all
intents and purposes as he might or could do in person
thereby ratifying and confirming all that said attorney-in-fact
and agent, or his substitute or substitutes, may lawfully do
or cause to be done by virtue hereof, or may have done in
connection with the matters described above.

IN WITNESS WHEREOF, this Power of Attorney has been signed as
of the 8th day of April, 2004.


OXFORD BIOSCIENCE PARTNERS IV L.P.
by its General Partner, OBP MANAGEMENT IV L.P.

By: /s/ Jonathan Fleming
Name:  Jonathan J. Fleming
Title:  General Partner


MRNA FUND II L.P.
By its General Partner, OBP MANAGEMENT IV L.P.

By: /s/ Jonathan Fleming
Name:  Jonathan J. Fleming
Title:  General Partner


OBP MANAGEMENT IV L.P.

By:/s/ Jonathan Fleming
Name:  Jonathan J. Fleming
Title:  General Partner



/s/ Jeffrey T. Barnes
Jeffrey T. Barnes



/s/ Mark P. Carthy
Mark P. Carthy



/s/ Jonathan J. Fleming
Jonathan J. Fleming



/s/ Michael E. Lytton
Michael E. Lytton



/s/ Alan G. Walton
Alan G. Walton