Protocol 610 is enrolling subjects who successfully achieved clinical benefit (reduction in Crohn's Disease Activity Index (CDAI) of at least 100 points) in Protocol 603. Protocol 610 is evaluating the length of initial effect of PROCHYMAL® adult human mesenchymal stem cells and the ability of these cells to successfully re-induce clinical benefit.

A significant number of individuals with Crohn's disease do not find relief with existing steroidal, immunosuppressive, or biologic therapies, and are forced to seek surgery or other drastic measures for treatment.

PROCHYMAL® adult human stem cells are manufactured from healthy, volunteer donors, extensively tested, and are stored to be available as needed. Human and animal studies have shown that the cells do not require any donor-recipient matching. The cells may have both immunosuppressive and healing benefits in Crohn's disease. The cells naturally migrate specifically to sites of inflammation, so their effects are believed to be local and self-limiting rather than systemic.

Protocol 610 is an extension study offered only to those subjects who successfully achieved clinical benefit (reduction of CDAI of at least 100 points) in Protocol 603.

Inclusion Criteria:

• Participation in Osiris Protocol 603, with drop of at least 100 points in CDAI at Day 28

Exclusion Criteria:

• Substance abuse
• Failure to receive full dose of all interventions in Protocol 603