Osiris falls on Prochymal miss

Osiris Therapeutics Inc. (NASDAQ:OSIR) fell $4.18 (34%) to $8.03 on Tuesday after IV Prochymal missed the primary endpoints in two double-blind, international Phase III trials to treat acute graft-versus-host disease (GvHD). Preliminary data from a trial in 260 patients showed that IV Prochymal twice weekly for four weeks missed the primary endpoint of significantly improving durable complete response rate vs. placebo (35% vs. 30%, p=0.3). Prochymal also missed the primary endpoint vs. placebo in the per protocol population (n=179; 40% vs. 28%, p=0.087).

Preliminary data from the other trial, which enrolled 192 patients with newly diagnosed acute GvHD, showed that IV Prochymal plus steroid therapy missed the primary endpoint of significantly improving the proportion of patients surviving at least 90 days who achieved a complete response vs. steroid therapy alone (45% vs. 46%, p=0.8). Osiris said there was a high placebo response in patients with skin GvHD, which composed the majority of patients in the trial. ...