Athersys Inc said it sold the rights of its stem-cell therapy to treat inflammatory bowel disease to Pfizer Inc, the world's biggest drugmaker, and shares of Athersys nearly doubled in value.

Under the agreement, Pfizer will pay Athersys $6 million upfront and up to $105 million in milestones for the investigational stem cell therapy, MultiStem.

Athersys may elect to co-develop the therapy with Pfizer and both the companies will share expenses as well as profits and losses on an agreed basis, beginning at late-stage study, it said in a statement.

Inflammatory bowel disease is a group of inflammatory and autoimmune conditions that affect the colon and small intestine, typically resulting in severe abdominal pain, weight loss, vomiting and diarrhea.

Athersys' cells, which are derived from human bone marrow, have yet to be tested in people with inflammatory bowel disease.

Stem cells are the body's ultimate master cells. They make up days-old embryos and have the power to give rise to all the cells and tissues in the body.

Stem cell research-based companies Geron Corp and Cytori Therapeutics Inc have made similar deals with U.S. conglomerate General Electric Corp's healthcare unit.

Shares of Athersys almost doubled to $1.99 in pre-market trade. They closed at $1 Friday on Nasdaq.