SOUTH SAN FRANCISCO, Calif., April 29 RigelPharmaceuticals, Inc. (Nasdaq: RIGL) announced today that its lead productcandidate, R788, has successfully treated lupus prone mice and significantlyimproved their survival as reported in a recently published study of the drugcandidate. R788 (fostamatinib disodium) is an orally bioavailable syk kinaseinhibitor, which has shown clinically significant results in treating patientswith rheumatoid arthritis and immune thrombocytopenic purpura in clinicaltrials. A third clinical trial of R788 in patients with B-cell lymphoma willbe completed later this year. Rigel also expects to initiate a Phase 2clinical trial in lupus in the second half of 2008.
The study, which evaluated the potential of R788's effect on the immunecascade in an in vivo lupus model, has been published in Arthritis andRheumatism and is titled - "An Orally Bioavailable Spleen Tyrosine KinaseInhibitor Delays Disease Progression and Prolongs Survival in Murine Lupus,"(May 2008, Volume 58, No. 5, p.1433).
"These results are impressive and consistent with R788's mechanism ofaction," said Donald G. Payan, M.D., executive vice president and president ofdiscovery and research at Rigel. "Given this mechanism, R788 has the potentialto treat a broad range of immune-related disorders, a number of which we areadvancing in the clinic."
Summary of results
The study evaluated the effects of three doses of R788 versus a controlgroup and an untreated group of lupus-prone mice. The mice in the R788 groupsorally received 10 mg/kg, 20 mg/kg or 40 mg/kg twice a day, for 240 days.Baseline, periodic and terminal measurements of renal enzymes and proteinuria(presence of proteins in the urine associated with kidney malfunctions), bloodurea nitrogen, and other tests were done on all subjects in the treatment andcontrol groups.
At the completion of the study, only 2 of the 29 mice in the 40 mg/kggroup had elevated proteinuria compared to 21 of the 30 mice in the controlgroup. All 29 (100%) of the mice treated with 40 mg/kg of R788 survived theduration of the study, compared to 14 of the 30 (47%) mice in the controlgroup. The mice treated with 10 mg/kg and 20 mg/kg of R788 demonstratedresults that were between those of the control group and the 40 mg/kg group.In a separate study, where treatment was initiated after the onset of disease,the researchers noted that the majority of the animals (~95%) given the 40mg/kg dose had elevated proteinuria levels that decreased following the onsetdrug treatment.
Systemic Lupus Erythematosus (SLE)
Lupus is an autoimmune disease, which affects nearly 2 million Americans,the majority of whom are women (90%). The disease affects various parts ofthe body including the kidneys, skin, joints, heart, lungs, and brain. Itseffects can be mild, limited to a couple of organs in the body and occasionalflare-ups, or can cause serious and life-threatening complications. Likeother autoimmune diseases the primary characteristic of lupus is inflammation,which causes swelling, pain, loss of function and may ultimately destroy theinvolved organ if left untreated. Current therapies for lupus treat thesymptoms of the disease and include non-steroidal anti-inflammatory drugs(NSAIDS), corticosteroids, and, in severe cases where organ damage is at risk,immunosuppressant drugs.
About Rigel (http://www.Rigel.com)
Rigel is a clinical-stage drug development company that discovers anddevelops novel, small-molecule drugs for the treatment ofinflammatory/autoimmune diseases and cancer, as well as viral and metabolicdiseases. Our goal is to file one new investigational new drug (IND)application in a significant indication each year. Rigel has achieved thisgoal every year since 2002. Our pioneering research focuses on intracellularsignaling pathways and related targets that are critical to diseasemecha