Gilead Sciences, Inc. and Arresto Biosciences, Inc., a
privately-held, development-stage biotechnology company focused on medicines to
treat fibrotic diseases and cancer, today announced the signing of a definitive
agreement pursuant to which Gilead will
acquire Arresto. Under the terms of the agreement, Gilead
will acquire Arresto for $225 million and potential future payments based on
achievement of certain sales levels. Gilead
anticipates that the deal would close in the first quarter of 2011, subject to satisfaction
of certain closing conditions, and plans to finance the acquisition through
available cash on hand.

Arresto develops medicines that target enzymes involved in
the synthesis of the extracellular matrix, which appear to play a role in the
etiology of a variety of fibrotic diseases and cancer. The company’s lead
product is AB0024, a humanized monoclonal antibody (mAb) targeting the human
lysyl oxidase-like-2 (LOXL2) protein. The company recently initiated a Phase I
study evaluating AB0024 in patients with idiopathic pulmonary fibrosis (IPF). A
Phase I study of AB0024 in patients with advanced solid tumors is also ongoing.

“Arresto’s research and development expertise is well
aligned with Gilead’s areas of focus, including our ongoing clinical program
for ambrisentan in IPF,” said Norbert W. Bischofberger, PhD, Gilead’s Executive Vice President, Research and
Development and Chief Scientific Officer. “We look forward to working with
the team from Arresto to advance the development of novel therapies for serious
fibrotic diseases and explore their potential for the treatment of tumors.”
“Gilead shares Arresto’s vision of
bringing innovative new therapeutic options to patients with unmet medical
needs,” said Peter Van Vlasselaer, PhD, Arresto’s President and Chief
Executive Officer.

“Arresto was founded based on the promise of selective
antibody therapies and I am confident the combined resources of our companies best
position us to build upon our early scientific results.” “Under
Peter’s direction, Arresto has accomplished a remarkable amount in three short
years,” said Beth Seidenberg, MD, Arresto Chairman of the Board, and
Partner at Kleiner Perkins Caufield & Byers. “Peter’s leadership is
extraordinary and proven in several companies. The board is proud of the
accomplishment of the Arresto team and enthusiastic about Gilead’s
commitment to advancing the programs for the treatment of patients with
fibrosis and cancer.”