Rigel's bleeding disorder drug fails late-stage study

(Reuters) - Rigel Pharmaceuticals Inc said its lead drug to treat a bleeding disorder failed in a second late-stage trial, sending its shares tumbling 32 percent in premarket trading on Thursday. Data showed that one patient receiving a placebo achieved a stable platelet response, the main goal of the study, indicating there was no statistical significance, the company said. The drug, fostamatinib, was successful in an earlier late-stage study, achieving a stable platelet response compared with no response in those on placebo. Rigel is developing the drug to treat chronic immune thrombocytopenia (ITP) in which the immune system attacks and destroys the body's own blood platelets, resulting in bleeding. ITP patients can suffer extreme bruising, bleeding and fatigue due to low platelet count. The company, however, said on Thursday when data from both late-stage studies were combined, the patients showed a significant increase in their platelet counts within weeks of initial treatment, highlighting the potential benefit. Rigel's shares were trading at $2.16 in premarket trading. Up to Wednesday's close of $3.22, the stock had risen about 22 percent since the company announced positive first late-stage study in August. (Reporting by Dipika Jain in Bengaluru; Editing by Martina D'Couto and Sriraj Kalluvila)