02 Jul More stem cell trial problems for Osiris Therapeutics
Clinical trials can be vexing, just ask anyone associated with Osiris Therapeutics, a leading stem cell therapeutic company. The company recently announced that their mid-stage, Phase II trials to treat chronic obstructive pulmonary disease (COPD) with adult stem cells (called Prochymal) did a great job reducing inflammation, but failed to improve pulmonary function. The 62 patients enrolled in the trial will be followed for two years in order to assess possible long term effects of the therapy. Nevertheless, these results reveal how complicated and unpredictable clinical trials can be.
COPD is really a combination of two maladies, chronic bronchitis and emphysema, rolled into one diagnosis. The disease commonly is caused by smoking, which triggers an abnormal inflammatory response in the lung in some individuals. In the larger airways, this inflammation causes chronic bronchitis, while in the microscopic lung sacks called alveoli, the inflammatory response causes emphysema, which is the destruction of the lung tissues where oxygen and carbon dioxide are exchanged. The result of this double inflammatory whammy is to limit the flow of air to and from the lungs causing shortness of breath. COPD is poorly reversible and usually gets progressively worse over time. In 1990, COPD was the third leading cause of death worldwide.
Given the central role of inflammation in the pathogenesis of COPD, anyone would have predicted a priori that reducing lung inflammation would translate to improved lung function. But, this is like believing that the baseball team with the most hits will automatically win the game. It is not uncommon for such surrogate measurements of efficacy to fail to predict the final outcome—the full game must still be played and the clinical trial done before the outcome can be certain.
Osiris is also testing Prochymal for its ability to treat other inflammatory diseases, so the reduced inflammation seeing in the COPD trial might be a good omen for these other maladies, even if Prochymal is of little benefit to patients with COPD. Unfortunately, however, last month Osiris was forced to discontinue enrollment in a phase III trial to treat the chronic inflammatory bowel condition known as Crohn’s disease. The reason for this, according to the company, is that patients on the placebo arm of the trial were doing unexpectedly well and interim data analysis indicated that this response would make it impossible to show a benefit of the Prochymal therapy. After examining the data with the FDA, it was concluded that that there was a potential “systematic design flaw” in the trial that “might be related to the fact that patients responding to the initial stem cell therapy were eligible to participate in a second, longer-term trial evaluating Prochymal as a maintenance therapy. Because the current standard for determining response of Crohn’s patients to therapy is largely subjective, there may have been response bias to meet the eligibility requirements for continuation of therapy in the longer-term maintenance trial”.
Prochymal is a preparation of mesenchymal stem cells obtained from the bone marrow of healthy donors and specially formulated for intravenous infusion. In addition to Crohn’s disease, Prochymal also is being tested in two other Phase III studies to treat both acute and steroid-refractory graft-vs-host diseases (or GvHD). The FDA granted Prochymal Fast Track status for these and Crohn’s diseases and both the FDA and the European Medicines Agency granted Prochymal Orphan Drug status for GvHD. In addition to the COPD trail, Osiris is also conducting Phase II Prochymal trials for the treatment of acute myocardial infarction and type 1 diabetes. The therapy also is being developed as a potential treatment for acute radiation syndrome.
Osiris also has another stem cell product in the pipeline, called Chrondrogen, which is being tested for its ability to regenerate cartilage. Last November, Genzyme paid Osiris $130 million upfront and promised up to $1.3 billion more in milestone and other payments to gain commercialization rights to Prochymal and Chondrogen outside the U.S. Osiris retains the rights to market these products in North America. Clearly, the company has a lot riding on Prochymal and can ill afford any further clinical trial snafus.
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