Osiris appears to have thrown out the real endpoints called for in the phase II trial and replaced them with new endpoints which just happen to show Prochymal in the best light. Why would Osiris do this? Perhaps the pre-defined endpoints in the study all failed? That's a pretty safe assumption when companies decide to swap out trial endpoints with no disclosure or explanation.
Again, here is where Clinicaltrials.gov is a good fact checker. The site's listing of the
Prochymal acute myocardial infarction (AMI) study
shows left ventricular end systolic volume (ESV) as the primary endpoint. Secondary endpoints in the study are left ventricular ejection fraction (LVEF), infarct size and major adverse cardiovascular events (MACE).
ESV measures the volume of blood in a ventricle at the end of the heart's contraction -- an important assessment of how well the heart is able to pump blood to the rest of the body. [More blood left in the ventricle after contraction signals a weakened a heart muscle.]
Similarly, LVEF measures the percentage of blood that is pumped out of the ventricle with each heartbeat. A higher LVEF signals a stronger heart.
Osiris designed the phase II study with ESV and LVEF as two key efficacy endpoints based on the belief that the stem cells contained in Prochymal would help rebuild heart muscle, thereby lowering ESV and raising LVEF compared to placebo.
Osiris' silence on the outcomes of these two important endpoints should be deafening to investors -- and not in a good way.
The mechanistic data is complemented by clinical data showing treatment with Prochymal resulted in a statistically significant reduction in heart failure. In the study, seven patients who were treated with placebo have progressed to heart failure requiring treatment with intravenous diuretics, compared to none of the Prochymal patients (p=0.01). Furthermore, patients receiving placebo tended to require re-hospitalization for cardiac issues sooner than the patients receiving Prochymal (median 27.5 days vs. 85.5 days).
These are interesting observations, but again, largely irrelevant for the purposes of this study since these weren't predefined endpoints. Importantly, Osiris doesn't disclose the time point at which these purported benefits occurred, nor does the company tell us anything about the number of patients analyzed. How was heart failure defined? Osiris doesn't say. What was the baseline incidence of heart failure in the study? Osiris doesn't say. The study only allowed for a single infusion of Prochymal or a placebo immediately after the first heart attack but patients were followed for six months or a year, so how do follow-up therapies in each arm of the study compare? Were they balanced? Again, Osiris doesn't say.