Exhibit
99.1
Rigel R788 Raises Platelet Counts in Immune
Thrombocytopenic Purpura (ITP) Patients in Phase 2 Study
SOUTH SAN FRANCISCO, Calif., November 9, 2007 – Rigel Pharmaceuticals,
Inc. (Nasdaq:RIGL) today announced results of its Phase 2 clinical study of
R788, a novel, oral Syk kinase inhibitor, in patients with Immune
Thrombocytopenic Purpura (ITP). The single-center, open-label, dose-escalating
study showed that R788 (tamatinib fosdium) can improve platelet counts in this
autoimmune disorder in which the body attacks and destroys its own blood
platelets.
Initiated in January 2007, the study evaluated the safety and efficacy
of R788 in adult ITP patients who had previously undergone and failed to
respond to available treatments. Despite the severity of their disease, a
majority of the patients responded favorably to the study drug. The primary
side effects were gastrointestinal related events in certain patients.
“The effects of R788 treatment in this very refractory group of ITP
patients are impressive. The majority of these patients have reported important
clinical benefit from R788, and I look forward to further studies with this
exciting agent,” said James B. Bussel, M.D., director of the Platelet Research
and Treatment program at the Phyllis and David Komansky Center for Children’s
Health and NewYork-Presbyterian Hospital/Weill Cornell Medical Center and
professor of pediatrics in obstetrics and gynecology and in medicine at the
Weill Cornell Medical College, and principal investigator on this study.
Elliott Grossbard, M.D., senior vice president of medical development
at Rigel, said, “We are pleased with the results of this Phase 2 study of R788
and have already begun to review the data to determine the appropriate next
steps.” He added, “Rigel’s oral R788 drug candidate may not only help patients
with ITP, but may also have potential therapeutic benefit in patients with
rheumatoid arthritis and lymphoma, where we have additional Phase 2 studies
ongoing.”
Study Design and Results
This single-center, ascending dose, proof-of-concept study evaluated
various doses of R788 with most patients receiving between 100 to 175 mg/day
BID. The study enrolled adult patients in the U.S. who have chronic refractory
ITP. The patients were monitored for safety and early efficacy, with the
primary efficacy marker being the measure of platelet counts compared to each
patient’s baseline measurement taken prior to introduction of R788.
Nine of the first 14 patients (64%) studied responded favorably to R788
treatment with higher stable platelet counts; six of these had peak platelet
counts of greater than 100,000 platelets/ul of blood. Two patients, who had
previously failed a wide range of other treatments and were receiving weekly IV
gammaglobulin, maintained platelet counts while on only R788 for 20 weeks of
the study. For those two patients, this marked the first time in 10 years that
each achieved prolonged avoidance of intravenous immunoglobulin G injections.
Overall these patients were highly refractory with most having failed several
other therapies, 10 had failed splenectomy and 5 were over 70 years old. The
primary side effects were GI-related symptoms. R788 elevated blood pressure in
some patients but appeared not to have significant effect on neutrophil counts.
An abstract of these results is available on the American Society of
Hematology (ASH) website. A more complete and updated poster presentation will
be made at the ASH meeting on December 8, 2007, from 9:00a.m. – 7:30p.m., in
Atlanta, GA.
Immune Thrombocytopenic Purpura
ITP affects
approximately 200,000 people in the U.S., with an estimated 30,000 new cases
each year. 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. Failure of first-line medical therapy for
ITP, which is primarily steroids, can lead to the removal of the spleen, which
poses the risk of other significant complications. Other therapies in late
study aim to boost blood platelet production while R788 is attempting to
address the autoimmune basis of the disease.
Taken in tablet
form, R788 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 R788, it
interrupts this immune cell function and allows the platelets to escape
destruction. Preclinical and early clinical data show that R788 may be useful
in stopping platelet destruction and may provide therapeutic benefit in
treating this rare autoimmune disorder.
Further information
on ITP and R788 in ITP is available at Rigel’s website: http://www.rigel.com/rigel/ITP
About Rigel (www.rigel.com)
Rigel is a clinical-stage drug development company that discovers and
develops novel, small-molecule drugs for the treatment of
inflammatory/autoimmune diseases and cancer, as well as viral and metabolic
diseases. Our goal is to file one new investigational new drug (IND)
application in a significant indication each year. Rigel has achieved this goal
every year since 2002. Our pioneering research focuses on intracellular
signaling pathways and related targets that are critical to disease mechanisms.
Rigel’s productivity has resulted in strategic collaborations with large
pharmaceutical partners to develop and market our product candidates. Rigel has
product development programs in inflammatory/autoimmune diseases such as
rheumatoid arthritis, thrombocytopenia and asthma, as well as in cancer.
This press release contains “forward-looking” statements, including
statements related to the potential efficacy of Rigel’s product candidates. 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 “plans,”
“intends,” “indicates,” “promising,” “expects,” “anticipates” and similar
expressions are intended to identify these forward-looking statements. There
are a number of important factors that could cause Rigel’s results to differ
materially from those indicated by these forward-looking statements, including
risks associated with the timing and success of clinical trials and the
commercialization of product candidates, as well as other risks detailed from
time to time in Rigel’s SEC reports, including its Form 10-Q for the quarter
ended September 30, 2007. Rigel does not undertake any obligation to update
forward-looking statements.
Contact: Raul Rodriguez
Phone: 650.624.1302
Email: invrel@rigel.com
Rigel Media Contact: Susan C. Rogers, Alchemy Consulting, Inc.
Phone: 650.430.3777
Email: susan@alchemyemail.com