Rigel
Pharmaceuticals, Inc. (Nasdaq: RIGL) 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.
About Rigel
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.
Rigel Pharmaceuticals, Inc.
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