Bone Marrow Stem Cells for Spinal Cord Injury: Stemirac Endorsed for Full Approval in Japan, Plus Keio iPS 4-Year Data

Summary — Bone marrow stem cell therapy for spinal cord injury has passed an important milestone in Japan. On 15 October 2026 a subcommittee of Japan's Pharmaceutical Affairs Council endorsed full (regular) approval for Stemirac Injection, a product made from mesenchymal stem cells cultured from the patient's own bone marrow. It is the first regenerative medicine product to move from conditional, time-limited approval (granted in 2018) to full approval. In July of the same year, a Keio University team published in Nature Medicine the up-to-four-year follow-up of a phase 1 study in which iPS cell-derived neural progenitor cells were transplanted into patients with spinal cord injury. This article summarises both, based on Japanese announcements from the last six months.

Spinal cord injury and current standard care

Spinal cord injury occurs when the spinal cord is damaged by traffic accidents, falls or sports injuries, impairing motor, sensory and autonomic function below the injury. Injuries to the cervical (neck) cord can affect both arms and legs. Severity is usually graded with the ASIA Impairment Scale (AIS): A means a complete injury with no motor or sensory function below the level, B to D are incomplete injuries with some function preserved, and E is normal. Standard care consists of surgery to stabilise the spine and relieve compression, management of complications, and sustained rehabilitation. Because restoring the damaged nerve tissue itself has long remained a research goal, stem cell-based regenerative medicine has drawn great interest. For an overview, see our spinal cord injury stem cell page.

Stemirac, a bone marrow stem cell product for spinal cord injury — full approval endorsed in Japan

According to the Japanese pharmaceutical press (Yakuji Nippo and Nikkan Yakugyo, reports of 15–19 October 2026), the Regenerative Medicine Products and Biological Technology Subcommittee endorsed full approval of Stemirac Injection, developed by Nipro with Sapporo Medical University. The Ministry of Health, Labour and Welfare plans to grant formal approval in about one month. Stemirac consists of mesenchymal stem cells (MSCs) cultured from the patient's own bone marrow fluid and given by intravenous drip. It is indicated for patients with traumatic spinal cord injury graded AIS A to C, to improve neurological symptoms and functional impairment caused by the injury. It received a seven-year conditional, time-limited approval in December 2018, and Nipro applied for full approval in November 2025. At a press conference on 16 October, Health Minister Kenichiro Ueno described it as a highly groundbreaking product.

Results of the post-marketing comparative survey

Full approval was based on a post-marketing comparative use-results survey. According to Yakuji Nippo, 206 patients were registered in the product group and 263 in the control group; the primary analysis included 73 and 66 patients respectively. The survey was open-label, and patients were divided into two cohorts by AIS grade at 6–8 weeks after injury and followed up to 6 months after injury (or discharge from the rehabilitation hospital). In cohort 1 (AIS A), the proportion improving by two or more AIS grades was 42.1% in the product group versus 3.8% in the control group. In cohort 2 (AIS B or C), the proportion improving by one or more grades was 59.3% versus 25.0%. Both differences were reported as statistically significant, and the safety evaluation, including about seven years of post-marketing data, raised no new concerns.

The reports note that the product group received more rehabilitation than the control group; after analyses that took patient background into account, the Ministry concluded that efficacy had been confirmed. Committee members commented that it is difficult in routine care to separate the effect of the cells from that of rehabilitation, so adding rehabilitation data collection to the approval conditions is under consideration. During the seven-year re-examination period after full approval, all treated patients will be surveyed until registration reaches 300. The current price is 15,234,750 yen per dose, and pricing after full approval is expected to be discussed by the Central Social Insurance Medical Council. Intravenous bone marrow stem cells have also been studied in stroke; see our article on intravenous bone marrow stem cells for stroke.

A trial to expand the indication is under way

The Hokkaido Shimbun (10 July 2026) reported that Nipro is running a company-sponsored trial at 22 sites across Japan, using an investigational product with the same component as Stemirac, to expand the indication to amyotrophic lateral sclerosis (ALS). Spinal cord injury patients receive a single dose, whereas the ALS trial uses multiple doses; at Sapporo Medical University Hospital a participant received a second dose in April 2026.

iPS cells broaden spinal cord injury stem cell research — Keio's four-year follow-up

A team led by Professor Hideyuki Okano of the Keio University Regenerative Medicine Research Center and Professor Masaya Nakamura of the Department of Orthopaedic Surgery published the results of a phase 1 study in subacute spinal cord injury in Nature Medicine online on 21 July 2026 (British Summer Time). It is the world's first clinical study transplanting iPS cell-derived neural stem/progenitor cells into the injured human spinal cord. Four patients with complete cervical spinal cord injury (AIS A) in the subacute phase, 14–28 days after injury, took part and were followed for two to four years after transplantation.

According to the researchers, no tumour formation, including teratoma, and no serious adverse events attributable to the transplanted cells were seen, meeting the primary safety objective. In exploratory assessments, two of the four patients improved from complete paralysis (AIS A) to grade C or D. At 52 weeks the ISNCSCI motor score improved by a median of 13 points, a larger gain than in a historical control group of 52 patients (7 points), and independence in daily life (SCIM III) also improved. The team plans a larger placebo-controlled, double-blind trial to confirm efficacy and to develop combination therapy with rehabilitation and neurotrophic factors.

Research stage and how to read the results

The two studies are at different stages. Stemirac is an approved product already used in routine care in Japan, now moving to full approval on the basis of post-marketing comparative data. Keio's iPS cell study is a phase 1 study in four patients, and a controlled trial is being prepared as the next step. The efficacy figures in the phase 1 study come from a comparison with historical data, and the Stemirac survey was open-label, so other factors such as rehabilitation should be considered when reading them. An improvement being reported is different from the same benefit being proven for every patient. Japan's conditional, time-limited approval system is explained in our timeline of regenerative medicine in Japan, and the difference between the approved spinal cord product and knee regenerative medicine in our article on spinal cord and knee stem cells in Japan.

Frequently asked questions

Who is eligible for bone marrow stem cell therapy for spinal cord injury?

Under the approved indication, Stemirac is for patients with traumatic spinal cord injury graded AIS A to C. Because the cells are cultured from the patient's own bone marrow, the timing of treatment and cell preparation are considered together. Specific conditions and individual suitability are judged by the treating medical team.

What changes with full approval?

Conditional, time-limited approval is granted when efficacy is presumed; full approval follows confirmation of efficacy and safety with post-marketing data. Stemirac is the first product to make this transition, so it is watched as a model for other regenerative medicine products. Details such as pricing will be discussed by the Central Social Insurance Medical Council after formal approval.

How do iPS cell therapy and bone marrow stem cell therapy differ?

Stemirac delivers mesenchymal stem cells from the patient's own bone marrow intravenously, aiming at reducing inflammation and protecting nerves around the injury. Keio's study transplants neural progenitor cells made from iPS cells directly into the injured spinal cord to replenish nerve tissue. The cell types, routes of delivery and research stages differ.

Conclusion

Stemirac, a bone marrow stem cell product for spinal cord injury, showed higher proportions of patients with improved AIS grades than controls in a post-marketing comparative survey and is approaching full approval in Japan, while iPS cell-derived neural progenitor transplantation is preparing for its next trial with up to four years of safety data. The options for regenerative medicine combined with rehabilitation are steadily widening in Japan. Suitability and risks of any treatment are judged by the treating medical team, and we will update this summary from the original sources when formal approval and new results are published.

This article summarises public news reports, university announcements and a journal article. Names of companies, universities and medical institutions are given only to identify sources and are not an introduction or recommendation of any medical institution. Suitability of treatment is judged by the treating medical team.

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