Rigel Initiates Phase 3 Studies of Fostamatinib in ITP

            Rigel Initiates Phase 3 Studies of Fostamatinib in ITP

PR Newswire

SOUTH SAN FRANCISCO, Calif., July 16, 2014

SOUTH SAN FRANCISCO, Calif., July 16, 2014 /PRNewswire/ -- Rigel
Pharmaceuticals, Inc. (Nasdaq: RIGL) today announced the initiation of a Phase
3 clinical program for its oral SYK inhibitor, fostamatinib, in patients with
ITP (immune thrombocytopenic purpura). The focus of these clinical studies is
to evaluate the potential of fostamatinib to increase the platelet counts of
patients with chronic ITP. Fostamatinib may provide a novel therapeutic for
the underlying cause of this autoimmune disease of the blood.

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"Based on our extensive clinical experience with this product candidate, which
includes more than 4,500 patient-years of data, we hope to demonstrate that
fostamatinib can provide a new treatment option for patients with chronic
ITP," said James M. Gower, chairman and chief executive officer of Rigel.
Results of Rigel's Phase 2 clinical study, published in Blood (volume 113,
number 14), showed that fostamatinib significantly increased the platelet
counts of certain ITP patients, including those who had failed other currently
available agents.

Fostamatinib in ITP Phase 3 Program Design
A total of 150 ITP patients will be randomized into two identical
multi-center, double-blind, placebo-controlled clinical studies. The patients
will have been diagnosed with persistent or chronic ITP, and have blood
platelet counts consistently below 30,000 per microliter of blood. Two thirds
of the subjects will receive fostamatinib orally at 100 mg bid (twice daily),
the other third will receive placebo on the same schedule. Subjects are
expected to remain on treatment for 24 weeks. At week 4 of treatment, subjects
who meet certain platelet count and tolerability thresholds will have their
dosage of fostamatinib (or corresponding placebo) increased to 150 mg bid.

The primary efficacy endpoint of this program is a stable platelet response by
week 24 with platelet counts at or above 50,000 per microliter of blood for at
least 4 of the final 6 qualifying blood draws. Results are expected at
year-end 2015.

Immune Thrombocytopenic Purpura
Chronic ITP affects an estimated 60,000 – 125,000 people in the US. In
patients with ITP, the immune system attacks and destroys the body's own blood
platelets, which play an active role in blood clotting and healing. ITP
patients can suffer extraordinary bruising, bleeding and fatigue as a result
of low platelet counts. Current therapies for ITP include steroids, blood
platelet production boosters (TPOs) and splenectomy. Fostamatinib is the only
potential therapy that may address the autoimmune basis of the disease.

Taken in tablet form, fostamatinib blocks the activation of SYK kinase inside
immune cells. ITP causes the body to produce antibodies that attach to
healthy platelets in the blood stream. Immune cells recognize these antibodies
and affix to them, which activates the SYK enzyme inside the immune cell, and
triggers the destruction of the antibody and the attached platelet. When SYK
is inhibited by fostamatinib, it interrupts this immune cell function and
allows the platelets to escape destruction.

About Rigel (www.rigel.com)
Rigel Pharmaceuticals, Inc. is a clinical-stage drug development company that
discovers and develops novel, small-molecule drugs for the treatment of
inflammatory and autoimmune diseases, as well as muscle disorders. Rigel's
pioneering research focuses on intracellular signaling pathways and related
targets that are critical to disease mechanisms. Rigel currently has five
product candidates in development: fostamatinib, an oral SYK inhibitor in
Phase 3 clinical trials for ITP and expected to enter into a Phase 2 clinical
trial for IgA nephropathy in the second half of 2014; R348, a topical JAK/SYK
inhibitor currently in Phase 2 clinical trials for dry eye; R118, an AMPK
activator in Phase 1 development; and two oncology product candidates in Phase
1 development with partners BerGenBio and Daiichi Sankyo.

This press release contains "forward-looking" statements, including, without
limitation, statements related to Rigel's clinical development plans,
including the timing, design and nature of planned clinical trials and the
timing and nature of results of those trials, as well as the potential
activity of fostamatinib with respect to ITP and the ability of fostamatinib
to provide a new treatment option for patients with chronic ITP. Any
statements contained in this press release that are not statements of
historical fact may be deemed to be forward-looking statements. Words such as
"planned," "will," "may," "expect," and similar expressions are intended to
identify these forward-looking statements. These forward-looking statements
are based on Rigel's current expectations and inherently involve significant
risks and uncertainties. Actual results and the timing of events could differ
materially from those anticipated in such forward looking statements as a
result of these risks and uncertainties, which include, without limitation,
the availability of resources to develop Rigel's product candidates, Rigel's
need for additional capital in the future to sufficiently fund Rigel's
operations and research, the uncertain timing of completion of and the success
of clinical trials, market competition, risks associated with and Rigel's
dependence on Rigel's corporate partnerships, as well as other risks detailed
from time to time in Rigel's reports filed with theSecurities and Exchange
Commission, including its Quarterly Report on Form10-Q for thequarter ended
March 31, 2014. Rigel does not undertake any obligation to update
forward-looking statements and expressly disclaims any obligation or
undertaking to release publicly any updates or revisions to any
forward-looking statements contained herein.

Contact: Raul Rodriguez
Phone: 650.624.1302
Email: invrel@rigel.com

Media Contact: Susan C. Rogers, Rivily, Inc.
Phone: 650.430.3777
Email: susan@rivily.com

Rigel Pharmaceuticals, Inc.

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SOURCE Rigel Pharmaceuticals, Inc.

Website: http://www.rigel.com
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