Gilead Sciences to Acquire Myogen, Inc. for $2.5 Billion

Gilead Sciences, Inc. (Nasdaq:GILD) and Myogen, Inc. (Nasdaq:MYOG)
announced today that the companies have signed a definitive agreement
under which Gilead plans to acquire Myogen. The transaction has been
structured as a two-step acquisition comprised of a cash tender offer
for all of the outstanding Myogen common stock at $52.50 per share,
followed by a cash merger in which Gilead would acquire any remaining
outstanding Myogen common stock at $52.50 per share. Upon completion
of the second-step merger, Myogen will become a wholly-owned
subsidiary of Gilead. The value of the transaction is approximately
$2.5 billion. The deal is expected to be dilutive to Gilead's earnings
in 2007 and 2008, neutral in 2009 and accretive in 2010 and beyond.

Myogen's lead product candidate, ambrisentan, for the potential
treatment of pulmonary arterial hypertension (PAH), is an orally
available endothelin receptor antagonist. Endothelin is a small
peptide hormone that is believed to play a critical role in the
regulation of blood flow and cell division. Elevated endothelin blood
levels are associated with several cardiovascular disease conditions,
including PAH. Gilead and Myogen believe data from two completed
pivotal Phase III studies (ARIES 1&2) evaluating the safety and
efficacy of the product as a potential treatment for PAH would support
a New Drug Application (NDA). Myogen currently expects to file an NDA
with the U.S. Food and Drug Administration as early as the fourth
quarter of 2006. Ambrisentan has been granted orphan drug status for
the potential treatment of PAH in both the United States and Europe.
GlaxoSmithKline holds rights to the product outside the United States.

"Myogen represents a unique scientific and strategic fit with our
company, bringing to Gilead a late-stage product candidate that
addresses an area of significant unmet medical need and further
enhances our growing focus on pulmonology, as initially established
through our recent acquisition of Corus Pharma," said John C. Martin,
PhD, President and Chief Executive Officer, Gilead Sciences. "We are
excited about the potential of ambrisentan, which we believe could
have important clinical benefit over existing therapies for pulmonary
arterial hypertension. We look forward to welcoming Myogen's
Colorado-based employees to the Gilead team. Working together, we plan
to leverage both our development capabilities and experience
delivering differentiated therapeutics to the medical community to
make ambrisentan available for patients in need as quickly as
possible."

"We are proud to join with Gilead Sciences, one of the premier
biopharmaceutical companies in the world, in advancing the care of
patients suffering from life-threatening diseases," said J. William
Freytag, PhD, President and Chief Executive Officer, Myogen, Inc.
"Myogen was founded 10 years ago with a vision of making important
contributions to the treatment of cardiovascular disorders. Through
the dedication and effort of our talented employees, we have made
tremendous progress. Bringing Myogen and Gilead together will allow us
to build on our progress to date and expand the resources committed to
that vision."

Myogen currently markets and distributes Flolan(R) (epoprostenol
sodium) in the United States through an agreement with
GlaxoSmithKline. Flolan was approved in 1995 and is indicated for the
long-term intravenous treatment of primary pulmonary hypertension.
Additionally, Myogen is exploring darusentan, an endothelin receptor
antagonist, for the potential treatment of resistant hypertension.
Myogen recently initiated a Phase III study of the product. Myogen
also has a research collaboration with Novartis focused on the
identification of disease-modifying drugs for the treatment of chronic
heart failure and related cardiovascular disorders.

Terms of the Transaction

The tender offer is subject to various conditions, including the
tender of at least a majority of the shares of Myogen common stock in
the tender offer and the receipt of clearance under the
Hart-Scott-Rodino Antitrust Improvements Act. The board of directors
of Myogen has voted unanimously to recommend the tender offer and the
merger to its stockholders. Gilead and Myogen expect the tender offer
to close before the end of 2006. Lazard is acting as the exclusive
financial advisor to Gilead in the transaction. Goldman, Sachs & Co.
is acting as the exclusive financial advisor to Myogen.

Conference Call

Gilead will host a conference call today, October 2, 2006, at 8:30
a.m. Eastern Time, to discuss the proposed acquisition. To access the
live call, please dial 1-800-659-1966 (U.S.) or 1-617-614-2711
(international). The conference passcode number is 71673061. Telephone
replay is available approximately one hour after the call through 7:00
p.m. Eastern Time, October 5, 2006. To access, please call
1-888-286-8010 (U.S.) or 1-617-801-6888 (international). The
conference passcode number for the replay is 64040396. The information
provided on the teleconference is only accurate at the time of the
conference call, and Gilead will take no responsibility for providing
updated information.

About Gilead Sciences

Gilead Sciences is a biopharmaceutical company that discovers,
develops and commercializes innovative therapeutics in areas of unmet
medical need. The company's mission is to advance the care of patients
suffering from life-threatening diseases worldwide. Headquartered in
Foster City, California, Gilead has operations in North America,
Europe and Australia. For more information on Gilead Sciences, please
visit the company's website at www.gilead.com or call Gilead Public
Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

About Myogen

Myogen has two product candidates in late-stage clinical
development: ambrisentan for the treatment of patients with pulmonary
arterial hypertension (PAH) and darusentan for the treatment of
patients with resistant hypertension. Myogen and GlaxoSmithKline have
entered into a global PAH collaboration in which Myogen has marketing
and distribution rights to GlaxoSmithKline's Flolan(R) (epoprostenol
sodium) for Injection in the United States and GlaxoSmithKline has
licensed ambrisentan from Myogen for all territories outside of the
United States, where Myogen retains exclusive rights. Myogen also
conducts a target and drug discovery research program focused on the
development of disease-modifying drugs for the treatment of chronic
heart failure and related cardiovascular disorders. Please visit
Myogen's website at www.myogen.com.

Forward-Looking Statements

This press release includes forward-looking statements, within the
meaning of the Private Securities Litigation Reform Act of 1995, that
are subject to risks, uncertainties and other factors including the
risks to both companies that the acquisition of Myogen will not be
consummated as the transaction is subject to certain closing
conditions. In addition, if and when the transaction is consummated,
there will be risks and uncertainties related to Gilead's ability to
successfully integrate the products and employees of Gilead and
Myogen, and the ability of ambrisentan for pulmonary arterial
hypertension to receive regulatory approvals or market acceptance.
These risks, uncertainties and other factors, and the general risks
associated with the respective businesses of Gilead and Myogen as
described in the reports and other documents filed by each of them
with the Securities and Exchange Commission, could cause actual
results to differ materially from those referred to in the
forward-looking statements. The reader is cautioned not to rely on
these forward-looking statements. All forward-looking statements are
based on information currently available to Gilead and Myogen, and
neither Gilead nor Myogen assumes any obligation to update any such
forward-looking statements or other statements included in this press
release.

Additional Information and Where to Find It

This announcement is neither an offer to purchase nor a
solicitation of an offer to sell shares of Myogen. Myogen stockholders
are urged to read the relevant tender offer documents when they become
available because they will contain important information that
stockholders should consider before making any decision regarding
tendering their shares. At the time the offer is commenced, Gilead
will file tender offer materials with the U.S. Securities and Exchange
Commission, and Myogen will file a Solicitation/Recommendation
Statement with respect to the offer. The tender offer materials
(including an Offer to Purchase, a related Letter of Transmittal and
certain other offer documents) and the Solicitation/Recommendation
Statement will contain important information, which should be read
carefully before any decision is made with respect to the tender
offer. The Offer to Purchase, the related Letter of Transmittal and
certain other offer documents, as well as the
Solicitation/Recommendation Statement, will be made available to all
stockholders of Myogen at no expense to them. The tender offer
materials and the Solicitation/Recommendation Statement will be made
available for free at the Commission's web site at www.sec.gov. Free
copies of the Offer to Purchase, the related Letter of Transmittal and
certain other offering documents will be made available by Gilead by
mail to Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA
94404, attention: Investor Relations.

In addition to the Offer to Purchase, the related Letter of
Transmittal and certain other offer documents, as well as the
Solicitation/Recommendation Statement, Gilead and Myogen file annual,
quarterly and special reports, proxy statements and other information
with the Securities and Exchange Commission. You may read and copy any
reports, statements or other information filed by Gilead or Myogen at
the SEC public reference room at 100 F Street, N.E., Washington, D.C.
20549. Please call the Commission at 1-800-SEC-0330 for further
information on the public reference room. Gilead's and Myogen's
filings with the Commission are also available to the public from
commercial document-retrieval services and at the website maintained
by the Commission at www.sec.gov.

Interests of Certain Persons in the Offer and the Merger

Gilead will be, and certain other persons may be, soliciting
Myogen stockholders to tender their shares into the tender offer. The
directors and executive officers of Gilead and the directors and
executive officers of Myogen may be deemed to be participants in
Gilead's solicitation of Myogen's stockholders to tender their shares
into the tender offer.