AZN returns fostamatinib rights to Rigel

AstraZeneca plc (LSE:AZN; NYSE:AZN) said it will not proceed with regulatory submissions for fostamatinib and will return rights to the compound to Rigel Pharmaceuticals Inc. (NASDAQ:RIGL) after the partners reported mixed primary endpoint data from the Phase III OSKIRA-2 and OSKIRA-3 trials in rheumatoid arthritis (RA). In the trials, two regimens of fostamatinib led to ACR20 response rates at month six of 28-40%. However, the response rates are lower than that of competing RA drug Xeljanz tofacitinib from Pfizer Inc. (NYSE:PFE). According to its label, Xeljanz produced ACR20 response rates of 69% in patients with an inadequate response to a DMARD and 51% in patients with an inadequate response to a tumor necrosis factor (TNF) alpha inhibitor in Phase III trials. OSKIRA-2 enrolled patients with an inadequate response to DMARDs, including methotrexate, and OSKIRA-3 enrolled patients with an inadequate response to methotrexate and a TNF alpha antagonist.

AstraZeneca said its decision was based on the totality of data from the OSKIRA program in RA, including previously reported data from the Phase III OSKIRA-1 trial in patients who had an inadequate response to methotrexate. In that trial, fostamatinib produced ACR20 response rates of 44-49% at month six and missed the co-primary endpoint of improving modified total Sharp score (mTSS). Rigel shed 40% in April on the OSKIRA-1 data (see BioCentury Extra, April 5). ...