High-Dose Administration of iPS Cell-Derived Cardiomyocyte Spheroids Shows Efficacy in Clinical Trial

The Yomiuri Shimbun

13:28 JST, October 4, 2025

High doses of cardiomyocyte spheroids derived from induced pluripotent stem (iPS) cells are effective in treating severe heart failure, according to interim results of a clinical trial.

Cardiomyocyte spheroids are specialized muscle cells that make up the heart that have been cultured into a 3D shape.

The results, which were announced by a group of medical institutions at a meeting of the Japanese College of Cardiology on Sept. 20, also confirmed that it is safe for patients to be administered doses three times higher than previously thought.

The clinical trial was conducted by Heartseed Inc., a Tokyo-based startup funded by Keio University.

From 2022 to January this year, cardiomyocyte spheroids were transplanted into the hearts of 10 patients with severe heart failure at Tokyo Women’s Medical University, the Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, Nihon University Itabashi Hospital and other medical institutions. Initially, a low dose of about 50,000 cardiomyocyte spheroids was administered to five patients, which enabled the researchers to confirm that there were no safety concerns. Higher doses of about 150,000 cardiomyocyte spheroids were then transplanted into the remaining five patients.

At the meeting, participating doctors from the institutions reported that three patients who received the high dose had no serious complications and showed improvements in areas such as cardiac contractility, which is the ability of the heart muscle to pump blood.

Heartseed plans to confirm whether the high doses yield greater efficacy in improving heart conditions than current methods. The company intends to submit the results of the clinical trial to the Health, Labor and Welfare Ministry and apply for approval to manufacture and market the therapeutic product as early as 2026, with the aim of putting it into practical use in 2027.

“We want to make this new treatment available to patients as soon as possible,” said Heartseed Chief Executive Officer Keiichi Fukuda, who is also a professor emeritus at Keio University.

Shinshu University Prof. Koichiro Kuwahara, who specializes in cardiology, said, “It’s still too early to say for sure, but the results suggest that there are therapeutic effects and give us hope that the method can advance to the next phase.”