"This study is the largest of its kind and provides key insights into the mechanism of action of mesenchymal stem cells in the setting of acute myocardial infarction," said Lode Debrabandere, Ph.D., Senior Vice President of Therapeutics at Osiris. "These important mechanistic observations are consistent with data obtained from our preclinical models and from the first placebo-controlled human trial with Prochymal published in the Journal of the American College of Cardiology. Given the quality of the data and highly encouraging results observed thus far, we are extending the trial's duration to capture a better understanding of the long-term clinical benefits of MSCs."
The canned quote from management: Always positive and optimistic. I usually ignore this fluff but in this case, Debrabandere reminds me that Osiris conducted a previous phase I study of Prochymal in patients suffering from a first heart attack. This study enrolled 53 patients and randomized them to treatment with either Prochymal or placebo. In other words, the older phase I study is very similar to the more current phase II study.
The phase I study, "A Randomized, Double-Blind, Placebo-Controlled, Dose-Escalation Study of Intravenous Adult Human Mesenchymal Stem Cells (Prochymal) After Acute Myocardial Infarction" was published the Journal of the American College of Cardiology in December 2009. You can download the study here for free. I won't go into too much detail about the results, but suffice to say, investigators found no statistically significant difference between Prochymal and placebo in ejection fraction or a six-minute walk test.Debrabandere's comment that Osiris is extending the current phase II study to capture the long-term clinical benefit of Prochymal is most perplexing because the phase I study was notable in that measures of cardiac improvement between Prochymal and placebo narrowed and in some cases disappeared with longer follow up. Why results would be different in the phase II study is a mystery, particularly since patients in the study are only treated with single infusion of Prochymal. Perhaps Osiris is extending the phase II study to delay the reporting of negative results? Again, that's a pretty safe assumption absent a better explanation. Osiris: The trial also demonstrated that treatment with Prochymal was safe. There were no infusional toxicities observed in patients receiving Prochymal. Serious adverse events occurred with equal frequency in both treatment groups (31.8%). To date, there have been 5 deaths in the trial, 2 in the Prochymal group and 3 in the placebo group. Prochymal is safe but so is placebo. That's no great comfort. Deaths in the study are essentially equivalent in both arms, a survival benefit favoring Prochymal would have been better. Osiris: "For interventional cardiologists, keeping our myocardial infarction patients from progressing to heart failure is central to our mission," said Mark Vesely, M.D., Principal Investigator on the Study and Assistant Professor of Medicine (Interventional Cardiology) at the University of Maryland School of Medicine. "It is remarkable and very encouraging to see significant changes in clinically meaningful parameters this early in the study. We look forward to the additional data that will be gathered as the study progresses, which will help us to better understand both the magnitude and durability of the benefit to treatment." Vesely's comments were remarkable but not for the reasons he states. Vesely is the researcher in charge of this phase II study and sounds encouraged but he ignores the missing data even though endpoints like EVF and LVEF are more clinically meaningful measures of cardiac health and progression to heart failure than what Osiris chose to disclose Monday. I tried to reach Vesely to ask him about the study and the missing data but he didn't respond to my email. Bill Seiler, a spokesperson for the University of Maryland School of Medicine, reached by phone, said Vesely's comment included in the Osiris press release was not authorized or pre-approved by the school.