Japan’s drugmaker Sumitomo Pharma has applied for manufacturing and marketing approval of a new treatment for advanced Parkinson’s disease that involves transplanting stem cells directly into patients’ brains. The company, working with its partner RACTHERA, has submitted the application for an allogeneic induced pluripotent stem (iPS) cell–derived therapy known as “raguneprocel” and secured priority review status under Japan’s fast-track Sakigake system. This treatment is designed to improve motor symptoms during the “off” periods in Parkinson’s, when medication wears off and symptoms return, according to Sumitomo Pharma and reporting from Nampa.
How the trial paved the way
The approval bid is based on data from a Phase I/II clinical trial led by Kyoto University Hospital and the Center for iPS Cell Research and Application (CiRA). In the trial, patients aged 50 to 69 received injections of iPS-derived dopaminergic progenitor cells—precursors to dopamine-producing neurons—into the putamen, a brain area tied to motor control. The trial focused on safety, monitoring each participant for two years. No serious adverse events occurred; minor side effects included temporary itching and a short-lived drop in kidney function. Encouragingly, four out of six patients assessed showed measurable improvements in motor function during off-medication periods.
Japan’s regenerative medicine framework allows conditional approval based on safety and potential benefit, with the condition that follow-up efficacy trials continue. As Nature reports, two other therapies have been given such temporary approval in the past, with mixed long-term outcomes. Raguneprocel’s early results have sparked optimism, but it will need further validation to stay on the market.
For patients whose symptoms are increasingly hard to control with levodopa and other medications, a therapy that could replace lost neurons rather than only manage symptoms offers a new layer of hope.
The road ahead
Even if approved, Sumitomo will need to prove it can scale production of the iPS-derived cells while keeping quality consistent. There are also practical hurdles, such as cost, insurance coverage under Japan’s national health system, and long-term monitoring for safety and efficacy. Internationally, interest is already growing. A related trial is underway at the University of California San Diego, with Sumitomo supplying the cell implants, according to The Asahi Shimbun. If results align, the therapy could make its way to other countries.
While not a cure, this is a meaningful step toward treatments that might one day slow, or even reverse, Parkinson’s disease progression.