EXHIBIT 10.10 Paul A. Brooke 21 E. 90th Street, #14AB New York, New York 10128 March 31, 2002 Jean-Pierre Sommadossi, Ph.D. Novirio Pharmaceuticals Limited c/o Novirio Pharmaceuticals, Inc. 125 CambridgePark Drive Cambridge, MA 02140 Dear Jean-Pierre:...

                                                                   EXHIBIT 10.10

                                 Xxxx X. Xxxxxx
                            00 X. 00xx Xxxxxx, #00XX
                            Xxx Xxxx, Xxx Xxxx 00000

March 31, 2002

Xxxx-Xxxxxx Sommadossi, Ph.D.
Novirio Pharmaceuticals Limited
c/o Novirio Pharmaceuticals, Inc.
000 XxxxxxxxxXxxx Xxxxx
Xxxxxxxxx, XX 00000

Dear Xxxx-Xxxxxx:

This letter is inform you that I resign effective immediately as a director of
Novirio Pharmaceuticals Limited and, as we have agreed, will terminate my
service as a consultant to the Company. Please acknowledge your receipt of this
letter and your agreement and acknowledgement that the 60,000 Ordinary Shares
which are the subject of the Stock Restriction Agreement dated as of December
15, 2000 by and between Novirio and me will become vested in full as of the
effective date of this termination of service.

Very truly yours,

/s/ Xxxx X. Brooke

Xxxx X. Xxxxxx



Acknowledged and Agreed this 31st day of March 2002

NOVIRIO PHARMACEUTICALS LIMITED


By: /s/ Xxxx-Xxxxxx Sommadossi
   ------------------------------------
   Xxxx-Xxxxxx Sommadossi, Ph.D.
   Chairman and Chief Executive Officer