February 14, 2007

Osiris Therapeutics announced six-month interim results in its evaluation of Chondrogen for the regeneration of meniscus in the knee. A total of 55 patients were treated in the Phase I/II, double-blind study evaluating the safety and exploratory effectiveness of Chondrogen, a preparation of adult stem cells formulated for direct injection into the knee after surgery. At the six-month time point, the study met its primary endpoint, demonstrating the safety of the product.

But the trial did not demonstrate that Chondrogen resulted in a statistically significant increase in the volume of meniscus as compared with placebo; however, an improvement in baseline cartilage and joint condition was noted in patients treated with the stem cell drug that was not seen in patients who received placebo.

The study was designed to assess the safety of an injection of stem cells into the joint capsule and to gain preliminary efficacy data on the extent of tissue regeneration using magnetic resonance imaging (MRI). Patients in the study underwent standard meniscectomy surgery to remove torn or damaged tissue in their meniscus. One week following surgery, the patients were given a single injection of either placebo, or a low dose (50 million cells) or high dose (150 million cells) of Chondrogen. Patients will be followed for safety and additional preliminary efficacy, such as pain, cartilage damage and changes in the meniscus for two years under the current study protocol.

An initial review of the data showed that Chondrogen was well tolerated, was not associated with serious adverse events, did not result in any adverse hematological events and did not result in the formation of any unwanted or ectopic tissue. There was no significant change in the volume of meniscus on MRI at six months in patients who received Chondrogen compared with those patients receiving placebo.