Wyeth and Ambrx Form Multi-target Alliance to Leverage Recent Ambrx Biologics Platform...

Wyeth and Ambrx Form Multi-target Alliance to Leverage Recent Ambrx Biologics
Platform Advances

COLLEGEVILLE, Pa. and SAN DIEGO, Sept. 18 /PRNewswire/ -- Wyeth
Pharmaceuticals, a division of Wyeth (NYSE: WYE) and Ambrx Inc. today
announced the formation of a worldwide alliance to discover, develop, and
commercialize protein drug candidates for three undisclosed targets in
multiple therapeutic areas. The alliance will capitalize on Ambrx's recent
breakthroughs in applying its protein medicinal chemistry platform to proteins
produced in mammalian cells such as antibodies and antibody-toxin conjugates.

Ambrx anticipates earning near term payments from an upfront commitment,
target loading fees and research funding. In addition, Ambrx will be eligible
to receive escalating preclinical, clinical, regulatory and commercial
milestone payments as well as tiered royalties on sales of products resulting
from the collaboration.

"This collaboration with Ambrx reinforces Wyeth's commitment to sustaining and
growing our already robust capabilities in the field of biologics drug
discovery through partnerships with biotech innovators," said Mikael Dolsten,
M.D., Ph.D., President, Wyeth Research. "We are enthusiastic about working
with Ambrx, a company with the ability to create and advance precisely
engineered biologic drug candidates into clinical trials using its proprietary
platform."

Stephen Kaldor, Ph.D., President and CEO of Ambrx, said: "Wyeth is a
long-standing leader in protein therapeutics with a strong record of
successfully developing innovative products. We are pleased that Wyeth
recognizes the power of the Ambrx EuCODE(TM) platform and look forward to
collaborating with Wyeth's talented personnel to produce the next generation
of biologic drugs."

About Ambrx

Ambrx Inc. is a clinical stage biopharmaceutical company with a broad
biologics platform that allows it to create best-in-class therapeutics,
including improved versions of native proteins and therapeutic antibodies.
Its most advanced product candidate, ARX201, is a long-acting growth hormone
partnered with Merck Serono that has successfully completed initial clinical
trials. The company has further validated its biologics platform through
additional partnerships with Merck Serono, Eli Lilly and Company and Merck &
Co. Ambrx is advancing a robust portfolio of product opportunities spanning
multiple therapeutic areas that are high optimized for efficacy, safety and
ease of use. For additional information, visit www.ambrx.com.

About Wyeth

Wyeth Pharmaceuticals, a division of Wyeth, has leading products in the areas
of women's health care, infectious disease, gastrointestinal health, central
nervous system, inflammation, transplantation, hemophilia, oncology, vaccines,
and nutritional products. Wyeth is one of the world's largest research-driven
pharmaceutical and health care products companies. It is a leader in the
discovery, development, manufacturing, and marketing of pharmaceuticals,
vaccines, biotechnology products, nutritionals and non-prescription medicines
that improve the quality of life for people worldwide. The Company's major
divisions include Wyeth Pharmaceuticals, Wyeth Consumer Healthcare and Fort
Dodge Animal Health.

The statements in this press release that are not historical facts are
forward-looking statements that are subject to risks and uncertainties that
could cause actual results to differ materially from those expressed or
implied by such statements. These risks and uncertainties include, among
others, risks related to our proposed merger with Pfizer, including
satisfaction of the conditions of the proposed merger on the proposed
timeframe or at all, contractual restrictions on the conduct of our business
included in the merger agreement, and the potential for loss of key personnel,
disruption in key business activities or any impact on our relationships with
third parties as a result of the announcement of the proposed merger; the
inherent uncertainty of the timing and success of, and expense associated
with, research, development, regulatory approval and commercialization of our
products and pipeline products; government cost-containment initiatives;
restrictions on third-party payments for our products; substantial competition
in our industry, including from branded and generic products; emerging data on
our products and pipeline products; the importance of strong performance from
our principal products and our anticipated new product introductions; the
highly regulated nature of our business; product liability, intellectual
property and other litigation risks and environmental liabilities; the outcome
of government investigations; uncertainty regarding our intellectual property
rights and those of others; difficulties associated with, and regulatory
compliance with respect to, manufacturing of our products; risks associated
with our strategic relationships; global economic conditions; interest and
currency exchange rate fluctuations and volatility in the credit and financial
markets; changes in generally accepted accounting principles; trade buying
patterns; the impact of legislation and regulatory compliance; risks and
uncertainties associated with global operations and sales; and other risks and
uncertainties, including those detailed from time to time in our periodic
reports filed with the Securities and Exchange Commission, including our
current reports on Form 8-K, quarterly reports on Form 10-Q and annual report
on Form 10-K, particularly the discussion under the caption "Item 1A, Risk
Factors" in our Annual Report on Form 10-K for the year ended December 31,
2008, which was filed with the Securities and Exchange Commission on February
27, 2009. The forward-looking statements in this press release are qualified
by these risk factors. We assume no obligation to publicly update any
forward-looking statements, whether as a result of new information, future
developments or otherwise.

Media Contact:
Heidi Chokeir, Ph.D.
Russo Partners
T: (619)528-2217
M: (858)-380-6584
heidi.chokeir@russopartnersllc.com

SOURCE Ambrx Inc.

Heidi Chokeir, Ph.D., Russo Partners, +1-619-528-2217, +1-858-380-6584,
heidi.chokeir@russopartnersllc.com