A stem cell-based dopamine neuron replacement therapy for the treatment of motor symptoms in Parkinson’s disease (PD) has received conditional, limited approval for use in Japan, a first for this type of therapy.
The therapy, developed by Sumitomo Pharma and known as raguneprocel, is available only to eligible patients being treated within the Japanese healthcare system and is not currently approved or available to patients in the United States.
Although the treatment is limited to use in Japan, the approval represents an important step forward in the development of therapeutics for Parkinson’s motor symptoms.
“The limited, conditional approval of raguneprocel marks a significant scientific milestone for the Parkinson’s community. It reflects decades of rigorous research into regenerative approaches, and while not available in the U.S., it offers encouraging evidence that cell-based therapies may one day become a meaningful part of Parkinson’s treatment,” says Brian Fiske, PhD, chief scientist at The Michael J. Fox Foundation.
What is Raguneprocel?
Raguneprocel is a stem cell-based dopamine neuron replacement therapy made from donor cells that are developed in the laboratory into dopamine-producing neurons. These lab-grown neurons are surgically transplanted into the putamen, a region of the brain involved in movement control that is affected in Parkinson’s disease.
The therapy was evaluated in a Phase I/II clinical trial at Kyoto University Hospital involving seven people with Parkinson’s disease between the ages of 50 and 69. Participants were followed for 24 months after transplantation. Among the six patients evaluated for motor outcomes, four showed potential clinical benefits when off medication and five when on medication. Brain imaging demonstrated dopamine production from the transplanted cells in the putamen. Researchers concluded that the transplanted cells survived, produced dopamine, did not form tumors and showed signs of potential clinical benefit.
Although study participants showed potential clinical benefits, the therapy is not a cure for Parkinson’s disease, and those receiving the therapy will likely need to continue taking levodopa, which the implanted cells could use to help produce dopamine. Additional data to confirm safety and demonstrate meaningful clinical benefits for treating motor symptoms of PD are also needed.
Where is Raguneprocel Available?
Raguneprocel has been approved for limited, conditional use in Japan, and is meant to treat people whose motor symptoms have not been adequately controlled by existing drug therapies, such as levodopa. Raguneprocel is not approved for use in the U.S. While the company is conducting a clinical trial of a related product in the U.S., there is currently no clear indication of whether or when Sumitomo Pharma will be ready to file for FDA approval of raguneprocel in the U.S. For U.S. patients, this means the treatment cannot be accessed domestically at this time.
The conditional approval for this treatment in Japan lasts for seven years. During this period, the company must collect additional safety and efficacy data to determine whether the therapy qualifies for full approval.
It is important to distinguish novel therapies like raguneprocel from stem cell or cell-based treatments sometimes marketed by medical spas or private centers. Approved and investigational therapies undergo years of laboratory research, carefully designed clinical trials and regulatory review to evaluate safety and effectiveness. In contrast, many stem cell treatments promoted directly to people with Parkinson’s today have not been tested through this level of scientific scrutiny and are not approved therapies for PD.
Research into Stem Cell Therapy for Parkinson’s
The conditional approval of raguneprocel signals continued momentum in the development of stem cell-based therapies. For example, several stem cell–based dopamine neuron replacement therapies are currently advancing in the United States. Among them, BlueRock Therapeutics is conducting a Phase III clinical trial of bemdaneprocel, an investigational therapy that uses stem cell–derived dopamine neurons transplanted into the brain to restore dopamine production. Like raguneprocel, this approach is designed to replace lost neurons and is being carefully evaluated for long-term safety and effectiveness. MJFF supported early efforts to engineer stem cells into dopamine neurons, work that has contributed to programs at companies such as BlueRock.
“While more work lies ahead, each step forward brings us closer to better treatment options and reinforces our commitment to advancing safe, effective therapies for people living with Parkinson’s,” said Dr. Fiske.
The Michael J. Fox Foundation will continue to follow the progress of this and other emerging therapies, supporting thoughtful research and helping move promising treatments forward.