Photo/Illutration Jun Takahashi, left, director of Kyoto University’s Center for iPS Cell Research and Application, speaks at a news conference in Kyoto in April. (Kazuhiro Fujitani)

KYOTO—Researchers have safely transplanted nerve cells generated from induced pluripotent stem (iPS) cells into the brains of Parkinson’s disease patients in a clinical trial, opening new treatment possibilities for the progressive neurological disorder.

No major adverse effects were found in the health of the seven patients involved in the trial and four showed improvements in their Parkinson’s symptoms, the Kyoto University researchers said on April 17.

“It is a significant achievement that we have been able to confirm improvement in patients’ symptoms,” said Jun Takahashi, director of Kyoto University’s Center for iPS Cell Research and Application, who is leading the research. “We hope to deliver this treatment to patients as soon as possible.”

Sumitomo Pharma Co. plans to apply for approval to manufacture and sell a treatment based on the results of the clinical trial by the end of fiscal 2025.

This would be the second application for a regenerative medical product using iPS cells, following cardiomyocyte sheets developed by a startup based on Osaka University’s technology.

The results of the clinical trial were published in the British scientific journal Nature on April 16.

In Parkinson’s disease, the loss of brain nerve cells that produce dopamine causes limb tremors and difficulty in movement.

There are about 250,000 Parkinson’s patients in Japan, according to the health ministry.

Drugs are used to suppress symptoms by replenishing dopamine in the brain. However, these medications become less effective over time and symptoms progress.

Kyoto University started the investigator-initiated clinical trial in 2018.

The researchers transformed human iPS cells into progenitor cells that will differentiate into dopamine-producing nerve cells. A total of 5 million to 10 million progenitor cells were transplanted into both sides of each patient’s brain.

The researchers then studied whether the transplanted cells would produce dopamine.

The subjects were seven patients in their 50s to 60s whose Parkinson’s symptoms were difficult to control as the efficacy of their medications had decreased.

The clinical trial studied the safety of the treatment on all seven patients and tracked its effectiveness on six.

The patients were monitored for two years after receiving the transplants.

No serious adverse events, such as the transplanted cells turning cancerous, were observed. However, milder side effects, such as itching wounds and a temporary decline in kidney functions, were reported.

The research team confirmed that the transplanted cells remained in the patients’ brains and produced dopamine. The amount of the neurotransmitter also increased.

Four of the six patients showed improvement in their Parkinson’s symptoms based on a score that quantifies and evaluates motor functions when medications are not working.

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