Preliminary results of Phase III Gvhd trials announced by Osiris Therapeutics

Sep 8 2009

Osiris Therapeutics, Inc. (NASDAQ: OSIR) today announced preliminary results for two phase III trials evaluating Prochymal for the treatment of acute graft versus host disease (GvHD). GvHD, the most common complication of bone marrow transplantation, is a life-threatening disease for which there is currently no approved treatment. Prochymal showed significant improvements in response rates in difficult-to-treat liver and gastrointestinal GvHD, however neither trial reached its primary endpoint.

Key findings from the GvHD trials include:

• There was no statistical difference between Prochymal and placebo on the primary endpoints for either the steroid-refractory (35% vs. 30%,>
• The primary endpoint for the steroid-refractory GvHD trial (durable complete response) for the per-protocol population approached statistical significance (40% vs. 28%,>
• In patients with steroid-refractory liver GvHD, treatment with Prochymal significantly improved response (76% vs. 47%,>
• Prochymal significantly improved response rates in patients with steroid-refractory gastrointestinal GvHD (88% vs. 64%,>
• In pediatric patients, Prochymal showed a strong trend of improvement in response rates (86% vs. 57%,>

“These data are still preliminary and further analysis is needed to gain a full appreciation of the results of these rigorous, double-blind, placebo-controlled trials,” said C. Randal Mills, Ph.D., President and Chief Executive Officer of Osiris Therapeutics. “We are encouraged to see Prochymal significantly improve response rates above standard of care in GvHD patients who currently have no good treatment options. We will meet with the FDA as soon as possible to discuss the most appropriate and efficient path forward for Prochymal in this life-threatening indication.”

Protocol 265 was designed to evaluate Prochymal as a first-line agent for the treatment of acute GvHD in combination with steroid therapy. The majority of patients in this trial were suffering from skin GvHD, which responded significantly better to steroids than had been previously reported in controlled trials. This high response rate to standard of care diminished the potential for Prochymal to demonstrate an effect.

In the more severe, steroid-refractory GvHD setting (protocol 280), the benefit of adding Prochymal to second-line therapy was evaluated. Prochymal approached statistical significance for the primary endpoint in the per-protocol patient population which is the group of patients that met all of the study protocol requirements, such as inclusion and exclusion criteria. Additionally, Prochymal significantly improved response rates to liver and gastrointestinal GvHD, for which there is currently no known reliable therapy. Notably, the Prochymal cohort had more severe GvHD (27% of Prochymal patients had grade D GvHD, the most severe form, vs. 16% of placebo patients,>

Based upon the results of the steroid-refractory GvHD trial, Osiris plans to file an amendment with the FDA to the current expanded access program, broadening the entry criteria to include patients with severe GvHD of the liver.

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