As Japan approves a stem cell treatment for spinal cord injuries in a landmark — if little noticed — decision, experts around the world have voiced concerns that underscore the trouble that still plague first-gen stem cell therapies.
Commenting at the request of Nature News, 10 specialists in stem cell science or spinal cord injuries poke holes in the small clinical trial that formed the basis of the conditional approval, questioning both the efficacy and safety of the treatment.
The therapy, Stemirac, involves extracting mesenchymal stem cells from a person who suffered from a spinal cord injury, growing about 50 million to 200 million of them in a lab, then intravenously infusing the MSCs back into the patient within 40 days of the injury. Exactly how it works to repair damage to the spinal cord is a bit of a black box now: Researchers led by professor Osamu Honmo at Sapporo Medical University believe it might have to do with reducing inflammation, protecting existing neurons or turning into nerve cells themselves.
Their belief is based on an unpublished 13-patient trial, which saw 12 of them “improve by at least one level on the American Spinal Injury Association impairment scale, an internationally recognized system that ranks people’s ability to contract muscles and sense touch on parts of the body,” Nature News reported.
Skeptics, however, remain leery.
Without a double-blind trial design, there’s no way to prove that the improvements weren’t due to natural healing and physical rehabilitation in the months after an injury, Bruce Dobkin, a neurologist at the University of California, Los Angeles, told Nature News.
“This trial, as designed, cannot reveal efficacy,” he said, adding the claim that the MSCs converted to neurons in the trial is also a red flag.
Another reason to be cautious, according to NIH stem cell researcher Pamela Robey: The fact, shown in previous research, that MSCs infused intravenously tend to get trapped in the lungs “makes it difficult to see how they can be effective in the spinal cord.”
Masanori Fukushima, a government-funded adviser to the project, has stood by Honmo’s work, emphasizing that some patients in the trial were too severely injured to have had achieved natural healing.
When the medical equipment manufacturer Nipro Corp begins selling Stemirac, it can mark some long awaited activity for regenerative medicine in the marketplace after years of delays and disappointments. But it’s not necessarily the entry that the industry — which is now exploring next-gen, often off-the-shelf, stem cell-based therapies for diabetes, Crohn’s disease and graft versus host disease among others — has been looking for.
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