The Niche

More shots with mesenchymal stem cells

Yesterday, I reported on the failure of two late stage trials exploring mesenchymal stem cells to quell the potentally fatal immune response in graft versus host disease. Those trials were led by Osiris, a company in Maryland, which still hopes to look through its data and ongoing trials for signs of efficacy. See Stem-cell drug fails crucial trials

However, they are not the only researchers exploring mesenchymal stem cells: a search on clinicaltrials.gov pulls up 77 studies for a variety of indications. But some scientists are uneasy with the idea of using the cells to quell inflammation, because it’s not clear how they work.

A Karolinska University group published its findings of a 55-person trial in the Lancet, so I asked two of the scientists involved for their thoughts. I reached one, Katarin Le Blanc, in yesterday’s article. This morning another scientist, Olle Ringden, responded. “The findings here will probably preclude mesenchymal stem cells to be used as first-line therapy for acute GVHD.” Ringden, who is working to recruit patients for a similar, double-blind study in Europe, thought that one reason that the Osiris trial did not show efficacy is that the trial included only a few children, and children seem to respond better than adults. He echoedthe thoughts of LeBlanc’s and Pranela Rameshwarof New Jersey Medical School, a scientist uninvolved with either of the studies: “We need to find the optimal way of giving these cells and the optimal conditions. We probably need to find out why mesenchymal stem cells work in some patients and why it doesn’t work in others.”

“The take-home message is that mesenchymal stem cells may be useful in steroid-refractory liver GVHD. In such patients, there was a significantly improved response and also durable complete response, compared to the placebo groups. Mesenchymal stem cells also improved the response rates in patients with steroid-refractory gastrointestinal GVHD. One reason for the poor outcome in this study in contrast to the European trial published in the Lancet may be that there were only few children included in this study (n=28). Children seem to have a better response rate compared to adults.”

Another company is exploring similar stem cells. The small company PluriStem announced this week that it would be starting a second Phase I trial of its product, described as a mesenchymal-like cell derived from placenta. A similar trial is reportedly also underway at Duke. Both trials are for critical limb ischemia, with the idea that these cells can help restore blood flow to jeopardized limbs. The company is also exploring other indications in which inflammation plays a role, including Crohn’s disease and multiple sclerosis.

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