Osiris Therapeutics, Inc. was an American company founded in March 1993 following the identification of mesenchymal stem cells (MSCs) by Dr. Arnold Caplan and colleagues at Case Western Reserve University in Cleveland, Ohio.

[1] Dr. Caplan contributed a license to certain technology and joined Kevin Kimberlin, James S. Burns, a biotech venture capitalist,[2][3] and Peter Friedli, as lead investor, to launch Osiris, named after the Egyptian god of fertility, resurrection, and the afterlife.

[1] The only direct competitor of Osiris at the time was a unit of Novartis, Systemix, which focused on stem cell treatments for cancer.

[1] Osiris also held a majority stake in Gryphon, a blood stem cell technology firm spun out of Johns Hopkins Medical School.

[12] In May 2012, Osiris received the first regulatory clearance in the world for a systemically administered stem cell drug,[13] called Prochymal or remestemcel-L,[14] which was approved for pediatric Graft-versus-Host Disease (GvHD).

[24] Ryoncil was tested in a March 2020 pilot study at Mount Sinai Hospital in New York City on late-stage, ventilator-assisted COVID-19 patients suffering Acute Respiratory Distress Syndrome (ARDS).

[26] In December 2024, the FDA approved Ryoncil (remestemcel-L), as the first mesenchymal stromal cell (MSC) therapy for pediatric patients with steroid-refractory acute graft-versus-host disease (GVHD).