Improvements in gut and liver GvHD beyond standard-of-care and without increased toxicity were observed.

Osiris Therapeutics’ stem cell product Prochymal showed significant benefits as a treatment for steroid-refractory acute graft vs. host disease (SR-GvHD) in both adults and children, according to Phase III trial results. Prochymal comprises a preparation of expanded mesenchymal stem cells (MSC) derived from the bone marrow of healthy young adult donors. The stem cells are formulated for intravenous administration.

Data from a Phase III trial (Protocol 280) in adults are being presented at the 2010 BMT Tandem Meeting. The study included 244 patients with GvHD, who were treated using either Prochymal or placebo in addition to standard-of-care therapy.

Overall results showed that the addition of Prochymal resulted in a 76% response rate among patients with steroid-refractory liver and an 82% response rate for patients with gastrointestinal GvHD. For individuals with GvHD affecting the skin, liver, and gastrointestinal tract, treatment with Prochymal produced a 63% overall response rate. None of the placebo-treated patients in this group responded.

The pediatric trial (Protocol 275) showed that Prochymal therapy resulted in a 64% overall response rate compared with 36% for the placebo group. Treatment with Prochymal also more than doubled the complete response rate to 64% and halved disease progression to 21%.

“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,” states Paul Martin, M.D., professor of medicine at the University of Washington and principal trial investigator at the Fred Hutchinson Cancer Research Center. “This rigorous study shows significant improvements in gut and liver GvHD above and beyond standard-of-care and without additive toxicity.” 

Prochymal is currently undergoing Phase III trials against steroid-refractory GvHD, acute GvHD, and Crohn disease. The treatment is the first stem cell product to receive FDA expanded access approval, Osiris points out. Phase II trials with Prochymal are also under way for the treatment of acute myocardial infarction, pulmonary disease, and type 1 diabetes.

Last month Osiris bagged a $750,000 milestone payment from the Juvenile Diabetes Research Foundation on completing enrolment into the Phase II diabetes trial. Osiris has separately partnered with Genzyme to develop Prochymal as a medical countermeasure to nuclear terrorism and other radiological emergencies.

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