• Immune Thrombocytopenic Purpura (ITP) is a blood disorder in which the immune system attacks and destroys platelets in the blood resulting in an abnormally low platelet count. Rigel is focusing its ITP program on the chronic form of this disorder, targeting the underlying autoimmune cause of the disease, rather than stimulating platelet production.


• Approximately 200,000 people in the U.S. suffer from ITP. The majority of these cases are in women, with 50% of the new cases being found in children.


• Antibodies, usually of the IgG type, mediate the destruction in ITP. R788 has a novel mechanism of action, blocking IgG receptor signaling in macrophages and B-cells.

• In November, Rigel released initial results from its Phase 2 ITP trial showing that R788 increased platelet counts for a majority of the patients treated.

• Rigel expects to initiate expanded trials in 2008.

• Rigel R788 Raises Platelet Counts in Immune Thrombocytopenic Purpura (ITP) Patients in Phase 2 Study


• Rigel Provides Clinical Update of R788 Phase 2 Trials in ITP, Rheumatoid Arthritis and Lymphoma

Disease background and current therapeutic approaches
Immune Thrombocytopenic Purpura (ITP) is an autoimmune hematological disease whereby the immune system attacks and destroys platelets in the blood resulting in an abnormally low platelet count, which can result in easy bruising, bleeding gums and internal bleeding. There are two forms of ITP: acute thrombocytopenic purpura, which is most commonly seen in young children (2 to 6 years old) and usually does not recur; and chronic thrombocytopenic purpura, which requires continual follow up care with a hematologist.

Failure of first line medical therapy for the treatment of chronic ITP, consisting mostly of high dose steroids, can lead to a splenectomy (removal of the spleen), which poses the risk of other significant complications. There is no consensus on the appropriate management for persistent ITP, but due to the fact that sustained remission is infrequent – new therapies are needed.