GVHD is a potentially deadly complication stemming from bone marrow transplants in which transplanted immune cells attack a patient's own organs and tissue as foreign.

I previously predicted that Osiris would not be successful in gaining Canadian approval for Prochymal as a treatment for GVHD. Obviously I was wrong, but with an asterisk because newly released documents show that Health Canada granted conditional approval to Prochymal out of compassion for children with a very rare fatal illness and not based on convincing scientific evidence.

The Health Canada documents -- a summary report on an expert advisory panel that reviewed Prochymal and the drug's Canadian-approved label -- show that the decision to approve the stem cell therapy was based on clinical data culled in part from a failed study found to be "limited" and "suggestive but not definitive with respect to efficacy" by the Canadian agency's expert advisors.

This is how the six-member Expert Advisory Panel on Prochymal summed up Procyhmal's efficacy data:

"The panel noted that severe Grade D GvHD is an extremely serious disease that affects a very small patient population. A few panel members have seen in their clinical experience how pediatric patients dramatically responded to treatment with Prochymal. However, this positive anecdotal evidence is not adequately reflected in the efficacy data.

"The panel further noted that there is very limited efficacy data; the data is suggestive but not definitive with respect to efficacy. There is a very small post-hoc analysis (in children) from a randomized sic trial, protocol 280 that demonstrated a small change in effects between the Prochymal arm and the placebo arm. In addition, protocol 275 is a cohort study for severe refractory GvHD with limited efficacy endpoints and vague inclusion criteria. In protocol 275, the survival probability through 180 days post onset of acute GvHD in refractory Grade D pediatric patients is 56.2% for the Prochymal group and 31% for the historical control group. From a clinical perspective, this is a positive effect; however, it is not a conclusive indication of efficacy."

Despite lack of convincing evidence, the advisory panel, which met Jan. 26 under the auspices of Health Canada, deemed Prochymal to be safe and "most probably effective" for a small group of severely ill patients (kids with GVHD) who had run out of medical treatment options.

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