BALTIMORE--(BUSINESS WIRE)--Dec. 20, 2005--Osiris Therapeutics, Inc. announced today that it has received orphan drug designation from the U.S. Food and Drug Administration (FDA) for PROCHYMAL(TM), an adult stem cell product under investigation for the treatment of acute Graft vs. Host Disease (GVHD). Orphan drug status provides market exclusivity to the company for up to 7 years. PROCHYMAL is a formulation of a specific type of adult stem cell that has the ability to modulate the immune system in a way that may benefit patients suffering from a variety of immunological disorders. Osiris has two ongoing clinical trials of PROCHYMAL for the treatment of GVHD, a complication of bone marrow transplantation. In January of this year, PROCHYMAL became the first stem cell drug to be granted Fast Track status from FDA. FDA established the Fast Track program to expedite the development of promising treatments for life-threatening conditions.