Chrondrogen is one of these MSC-derived therapies, which Osiris hopes to develop into a product that could be used to repair damaged or torn knee tissue, or even as an effective treatment for osteoarthritis. Last February, Osiris released the first results from a phase II study of 55 patients who were undergoing surgery to repair a torn or damaged meniscus, the spongy, shock-absorbing cartilage between the tibia and femur. Osiris injected Chrondrogen into the knees of half the patients with the hope that stem cells in Chondrogen would implant in the knee and regenerate into new meniscus tissue. But after six months, patients given Chondrogen showed no increase in meniscus volume compared with patients given a placebo injection, the company reported. The results announced Tuesday come from the same study, which has now been followed out one year. In patients with meniscus damage and osteoarthritis at the time of surgery, a single injection of Chrondrogen led to a statistically significant reduction in pain compared with patients injected with hyaluronic acid, a therapy already approved for treatment of osteoarthritis, Osiris stated. (Hyaluronic acid is also marketed by Genzyme ( GENZ).) Furthermore, changes to bone in the knee joints that are associated with osteoporosis were reported in 21% of control patients but only 6% of Chrondrogen-treated patients. While these results suggest a positive signal of efficacy for Chrondrogen, Osiris failed to disclose that it gleaned these data from a retrospective analysis of a subgroup of patients in the trial.