The iPS Cell Breakthroughs Reshaping Drug Discovery for Rare Disease

Developing treatments for neurodegenerative conditions like amyotrophic lateral sclerosis (ALS) has historically faced significant hurdles. Many drug candidates that appeared effective in animal models ultimately failed in human clinical trials. Okano Hideyuki notes that "human and mouse neurons differ fundamentally in their properties and circuitry," which has been a "decisive barrier" for central nervous system diseases and led to repeated failures in drug development.

To overcome this, Okano’s team adopted an approach of generating iPS cells from ALS patients and differentiating them into motor neurons. These human-derived neurons accurately reproduced the disease’s hallmarks in the laboratory, including shortened neurites and early cell death. This precise human cell model allowed for drug repositioning, testing existing approved drugs for new therapeutic effects. The team discovered that ropinirole hydrochloride, a Parkinson’s medication, improved ALS motor neuron phenotypes.

The findings, published in 2018, moved rapidly from the lab to a physician-initiated clinical trial at Keiō University, with encouraging results for about 20 ALS patients. Okano states that the speed from iPS cell-based discovery to clinical testing "would have been unthinkable under the earlier models." This method also accounts for patient-to-patient variability by analyzing iPS cells from numerous patients, marking a new phase of real-world implementation, particularly with Japan's February 2026 announcement of a manufacturing system for iPS cell-based spinal cord injury therapy.