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Shares in Japanese drugmaker Sumitomo Pharmaceuticals fell 15.60% on Friday in what appeared to be profit-taking, a day after the government approved the company’s iPS cell-based treatments for Parkinson’s disease and heart disease.
Sumitomo Pharmaceuticals’ stock last week hit its highest since 2019, after rising more than 300% in 2025 amid growing confidence in Parkinson’s disease treatments. This treatment relies on induced pluripotent stem (iPS) cells, which are adult cells that are reprogrammed into a stem cell-like state.
Stem cells have the ability to self-renew and act as a repair system to replace damaged cells and maintain tissue, allowing their use in regenerative medicine.
“Over the long term, this treatment could be widely used and a blockbuster hit in Japan and the United States, but we expect it to have little profit contribution in the short term,” said Hidemaru Yamaguchi, an analyst at Citigroup Global Markets Japan.
Sumitomo shares are overheated and recent gains have been “overdone,” he added.
According to Japan’s Ministry of Health, Labor and Welfare, official approval will be given within the next one to two months, NHK reported.
The approval comes several years after Kyoto University professor Shinya Yamanaka, who later won the Nobel Prize for stem cell research, was the first to successfully generate iPS cells from mice in 2006.
Japan is working to develop stem cell therapies, and Kyoto University’s CiRA, which operates a clinical-grade iPS cell bank, provides researchers with access to prepared cells that can be used in clinical trials for a variety of conditions.
Sumitomo Pharmaceuticals develops and markets prescription medicines across multiple therapeutic areas, including neuroscience, oncology and regenerative medicine.
