First-of-a-kind stem cell therapies set for approval in Japan

Nature

by Asher Mullard

February 23, 2026

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Japan’s health ministry is set to approve two groundbreaking stem cell therapies, Amchepry and ReHeart, marking a significant milestone in regenerative medicine. These treatments, developed using induced pluripotent stem (iPS) cells, aim to address conditions like Parkinson’s disease and severe heart failure. However, some researchers caution that the clinical trial data is still limited, raising concerns about their readiness for widespread use. Amchepry, designed to treat Parkinson’s by converting blood cells into dopamine-producing progenitor cells, has been tested in seven patients. While early results show reduced tremors in at least four participants and no serious side effects, the Phase I/II trial was small and lacked a control group, leaving questions about long-term safety and efficacy. Similarly, ReHeart, which uses iPS cells to create heart muscle cell patches for those with ischaemic cardiomyopathy, has shown promise in a small Phase I trial but faces similar limitations. Critics argue that larger, double-blind controlled trials are essential to fully assess the benefits and risks of these therapies. Hiroshi Kawaguchi, an orthopaedic surgeon, describes the current data as “very weak” due to the lack of robust evidence from adequately sized studies. Paul Knoepfler, a stem-cell researcher at UC Davis, warns that rushing these treatments to market could pose serious risks. Japan’s approach to regenerative medicine is unique, allowing therapies with exploratory clinical trial data to receive conditional approval. While this may accelerate access to innovative treatments, it also raises concerns about oversight and patient safety. The Ministry of Health has recommended conditional approval for both Amchepry and ReHeart, with plans to finalize the decision by March 2024. The commercialization of these therapies will likely set

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Originally published on Nature on 2/23/2026