Phase III trial results of Osiris Therapeutics' Prochymal for GvHD to be presented at BMT Tandem Meeting

Osiris Therapeutics, Inc. (NASDAQ:OSIR) today announced that results from the Phase III trial evaluating Prochymal for the treatment of steroid-refractory acute graft vs. host disease (GvHD) will be presented by Paul Martin, M.D., of the Fred Hutchinson Cancer Research Center and Paul Szabolcs, M.D., of Duke University Medical Center at the 2010 BMT Tandem Meeting. The meeting is being held February 24-28 in Orlando, Florida.

“Treatment of Steroid-Refractory Acute GvHD with Mesenchymal Stem Cells Improves Outcomes in Pediatric Patients; Results of the Pediatric Subset in a Phase III Randomized, Placebo-Controlled Study”

“Refractory GvHD is a devastating disease for which there have been no well-controlled studies demonstrating the safety and effectiveness of any therapeutic agent beyond steroids,” said Paul Martin, M.D. of the Fred Hutchinson Cancer Research Center, Professor of Medicine at the University of Washington and principal investigator for the steroid-refractory GvHD trial. “This rigorous study shows significant improvements in gut and liver GvHD above and beyond standard of care, and without additive toxicity. We now have clear evidence demonstrating the benefits of mesenchymal stem cell therapy in the two most deadly and difficult-to-treat forms of the disease.”

Steroid-Refractory Gastrointestinal and Liver GvHD

Dr. Martin will give a presentation entitled, “Prochymal Improves Response Rates in Patients with Steroid-Refractory Acute Graft versus Host Disease (SR-GvHD) Involving the Liver and Gut: Results of a Randomized, Placebo-Controlled, Multicenter Phase III trial in GvHD” (Abstract #41) on Thursday, February 25th. Highlights from the abstract and presentation include:

• Prochymal significantly improved response in steroid-refractory liver (76% vs. 47%,>
• In the sickest patients - those with GvHD affecting all three organs, skin, liver and gastrointestinal tract - treatment with Prochymal resulted in a 63% overall response rate, while none of the placebo-treated patients responded (p<0.05).
• Patients treated with Prochymal had significantly less progression of liver GvHD compared to placebo (37% vs. 65%,>
• Prochymal demonstrated a positive safety profile relative to placebo for key safety outcomes of interest, including recurrent malignancy (8% vs. 10%), infusional toxicity (2% vs. 2%) and discontinuation of study due to an adverse event (1% vs. 5%).

The full abstracts are included in a February supplement issue of the peer-reviewed journal, Biology of Blood and Marrow Transplantation.

Pediatric Steroid Refractory GvHD

Dr. Szabolcs, Associate Professor, Pediatric Blood and Marrow Transplant Program at Duke University Medical Center, will present an abstract entitled “Treatment of Steroid-Refractory Acute GvHD with Mesenchymal Stem Cells Improves Outcomes in Pediatric Patients; Results of the Pediatric Subset in a Phase III Randomized, Placebo-Controlled Study” (Abstract #381) on February 27th. Highlights from the abstract include:

• Children receiving Prochymal had an overall response rate of 64% compared to 36% in patients receiving placebo.
• Prochymal more than doubled complete response rates (64% vs. 29%) and reduced disease progression by half (21% vs. 43%).
• Treatment with Prochymal resulted in a 30 point improvement in 100 day survival compared to placebo (79% vs. 50%).
• There was no infusional toxicity reported, no evidence of Prochymal leading to ectopic tissue and no adverse events leading to discontinuation of therapy.

GvHD, a frequent complication of bone marrow transplantation, is the leading cause of morbidity and mortality for patients receiving allogeneic hematopoietic stem cell (bone marrow) transplants. Currently there is no approved treatment for acute GvHD.