Portola Pharmaceuticals Announces Proposed Offering of Common Stock

SOUTH SAN FRANCISCO, Calif., March 9, 2015 (GLOBE NEWSWIRE) -- Portola
Pharmaceuticals, Inc. (Nasdaq:PTLA) today announced that it has
commenced an underwritten public offering of shares of its common stock
and expects to raise gross proceeds of approximately $100,000,000. All
of the shares of common stock in the offering will be sold by Portola
Pharmaceuticals. Subject to market and other conditions, the offering
is expected to price before 9:30 a.m., EDT, on March 10, 2015.

Morgan Stanley is acting as the book-running manager for the offering.
A registration statement related to the offering has been filed with
the Securities and Exchange Commission. A preliminary prospectus
supplement and final prospectus supplement, when available, may be
obtained from the offices of Morgan Stanley & Co. LLC, Attention:
Prospectus Department, 180 Varick Street, 2nd Floor, New York, NY
10014, or by email at [email protected]

This press release shall not constitute an offer to sell or the
solicitation of an offer to buy, nor shall there be any sale of these
securities in any state or jurisdiction in which such offer,
solicitation or sale would be unlawful prior to registration or
qualification under the securities laws of any such state or
jurisdiction. Any offer, if at all, will be made only by means of a
prospectus, including a prospectus supplement, forming a part of the
effective registration statement.

About Portola Pharmaceuticals, Inc.

Portola Pharmaceuticals is a biopharmaceutical company developing
product candidates that could significantly advance the fields of
thrombosis and other hematologic diseases. The Company is advancing its
three wholly-owned programs using novel biomarker and genetic
approaches that may increase the likelihood of clinical, regulatory and
commercial success of its potentially life-saving therapies. Portola's
partnered program is focused on developing selective Syk inhibitors for
inflammatory conditions.

Forward-Looking Statements

This announcement contains forward-looking statements, including
statements relating to Portola Pharmaceuticals' expectations regarding
the completion, timing and size of the proposed public offering. These
statements are subject to significant risks and uncertainties and
actual results could differ materially from those projected. Portola
Pharmaceuticals cautions investors not to place undue reliance on the
forward-looking statements contained in this release. These risks and
uncertainties include, without limitation, risks and uncertainties
related to market conditions and satisfaction of customary closing
conditions related to the public offering. There can be no assurance
that Portola Pharmaceuticals will be able to complete the public
offering on the anticipated terms, or at all. Risks and uncertainties
relating to Portola Pharmaceuticals and its business can be found in
the "Risk Factors" section of Portola Pharmaceuticals' Form 10-K for
the year ended December 31, 2014 filed with the SEC on March 2, 2015,
and in the preliminary prospectus supplement related to the proposed
offering filed with the SEC. Portola Pharmaceuticals undertakes no duty
or obligation to update any forward-looking statements contained in
this release as a result of new information, future events or changes
in Portola Pharmaceuticals' expectations.

CONTACT: Media: Joey Fleury, BrewLife,
         [email protected], 415.946.1090

         Investors: Alexandra Santos, Portola Pharmaceuticals,
         [email protected], 650.246.7239