Illustration.
Research and Clinical Trials
Each registered CL2020 trial we could find, what it tested, how many people took part, and what it found, in plain words.
The Short Version
Between 2018 and about 2022, eight registered trials in Japan tested one product, CL2020: donor (Allogeneic From a different person of the same species: donor cells rather than the patient’s own (which are called autologous).) Muse cells from bone marrow, made by Life Science Institute, Inc., a Mitsubishi Chemical group company. It was given by intravenous drip, without tissue matching or anti-rejection drugs.38,39,40
Six trials have published results, covering 57 treated people. All were small, and only the stroke trial was randomized and placebo-controlled, with 25 people on CL2020 and 10 on placebo.32,33,34,35,36,38 The confirmatory heart trial and the COVID-19 respiratory failure trial have no published results that we could find.40
Most investigators disclosed funding, fees or patents linked to the developer. That is normal for early development, and it is why independent, larger trials are the next step.33,34,35,38,39
Evidence: Early human trials (one small controlled trial) (stage 3 of 4)The CL2020 Trials
The eight registered trials of CL2020, with their registry numbers, size, design and published results.
| Condition | Registry | Phase | Treated | Design | Status | Published result |
|---|---|---|---|---|---|---|
| Heart attack (acute myocardial infarction, STEMI) with reduced pumping (LVEF 45 percent or less) | JapicCTI-183834 | 1/2 | 3 CL2020 | Open-label, single group with no control group; one dose about 4 days after blood flow to the heart was restored | Completed, published | In the 3 people given CL2020, heart pumping (LVEF) rose from 40.7 to 52.0 percent at 12 weeks, with no treatment-related adverse events. There was no control group.32,40 |
| Heart attack (acute myocardial infarction, STEMI) | JapicCTI-195067 | 2/3 (per a review table) | Unconfirmed | Described as a confirmatory trial; design details unconfirmed. Listed as ongoing in 2022; status after the 2023 discontinuation of CL2020 unconfirmed. | Status unconfirmed | None found40 |
| Stroke (subacute ischemic, mRS 3 or more) | JapicCTI-184103 | 2 (exploratory) | 25 CL2020, 10 placebo | Randomized, double-blind, placebo-controlled, single center (Tohoku University Hospital); one dose 14 to 28 days after the stroke | Completed, published | At 12 weeks, 40.0 percent of people given CL2020 (95 percent CI 21.1 to 61.3) had regained independence in daily life (mRS 0 to 2), compared with 10.0 percent on placebo. The lower confidence limit was above the preset 8.7 percent threshold. Upper-limb movement scores (Fugl-Meyer) also improved. This was one small trial; no confirmatory trial has been published.34 |
| Dystrophic epidermolysis bullosa, a severe blistering skin disease (adults) | JapicCTI-184563 | 1/2 | 5 CL2020 | Open-label, non-randomized, single group; one dose | Completed, published | After one CL2020 infusion, skin ulcer area improved at week 4 (2 of 5 people had more than a 50 percent reduction), but ulcers returned to baseline by week 12.33 |
| Spinal cord injury in the neck from trauma (cervical, C4 to C7, modified Frankel B1/B2) | jRCT1080224764JapicCTI-194841 | 1/2 (per a review table) | 10 CL2020 | Multicenter, non-randomized, non-blinded, single group; one dose | Completed, published | After one CL2020 dose, movement, daily-living and quality-of-life scores improved compared with before treatment. There was no control group.36,38,40 |
| ALS (sporadic, limb onset) | jRCT2063200047 | 2 | 5 CL2020 | Single center, open-label, single group; six monthly doses | Completed, published | Six monthly CL2020 doses were well tolerated. The change on the ALS rating scale “trended upward” but was not statistically significant, and blood inflammation markers rose for up to 6 months. There was no control group.35 |
| COVID-19 acute respiratory distress syndrome (ARDS) | jRCT2043210005 | 1/2 (per a review table) | Unconfirmed (press reports: 3 at first, 40 planned) | Unconfirmed. Announced in April 2021, with a planned start in May 2021. | No published results found | None found38,40,60 |
| Newborn brain injury from lack of oxygen (hypoxic-ischemic encephalopathy), alongside cooling therapy (therapeutic hypothermia); the SHIELD trial | NCT04261335jRCT2043190112 | 1 | 9 CL2020 (3 low dose, 6 high dose) | Single center, open-label, 3+3 dose escalation; one dose at 5 to 14 days of age | Completed, published | All 9 infants given CL2020 survived to 78 weeks, and 67 percent had normal developmental scores in all three areas tested. There was no control group, and the authors call for a randomized trial.37,38,65 |
The Japanese registry pages (JAPIC CTI and jRCT) could not be opened when this page was prepared, so their numbers come from the published papers that cite them.
What the Trials Reported About Safety
No trial was stopped for safety, and investigators judged nearly all serious medical events unrelated to the cells. Serious events did occur, and trials this small cannot detect rare harms.39
| Trial | Treated | Follow-up | What was reported |
|---|---|---|---|
| Heart attack, first in human | 3 | 12 weeks | No adverse events related to CL2020.32 |
| Epidermolysis bullosa | 5 | 52 weeks | Adverse events were mild or resolved on their own; one Grade 3 stomach pain; one possibly related temporary tingling that resolved in 14 days.33 |
| Stroke (randomized, placebo-controlled) | 25 (plus 10 placebo) | 52 weeks | 7 serious events in 5 treated patients (20 percent) against 1 on placebo (10 percent). One seizure event (Grade 4 status epilepticus) could not be ruled out as related. One death from pneumonia, judged unrelated. Gray or white hair turned black in 6 treated patients, counted as a treatment-related reaction.34 |
| ALS | 5 (six monthly doses) | 12 months | Mostly headache and fatigue; one serious event (a fracture from a fall), judged unrelated.35 |
| Spinal cord injury | 10 | 52 weeks | Two severe events, both judged unrelated: one death from pneumonia and one bladder stone needing surgery.36 |
| Newborn brain injury (SHIELD) | 9 | 78 weeks | One serious infection; one possibly related mild liver enzyme rise; one testicular tumor that genetic testing showed came from the infant’s own cells, not the donor cells. No deaths.38 |
Timeline
- 2010
Prof. Mari Dezawa’s team at Tohoku University in Japan reports adult human stem cells that can form cell types from all three germ layers starting from a single cell, tolerate stress, and did not form teratomas when implanted in mice. They name them Muse cells.1
- 2011
The same group reports that, among skin fibroblasts, induced pluripotent stem (iPS) cells arise from the Muse cell fraction.2
- 2013
A U.S. group isolates Muse cells from human fat using stress conditions, and the Dezawa lab publishes a step-by-step isolation protocol.5,3
- 2015
The Mitsubishi Chemical group begins developing Muse cell products through Life Science Institute, Inc.54
- 2016 to 2018
Independent groups in Argentina and Italy report immune-calming effects and strong tolerance of DNA damage in lab studies. Muse cell counts in the blood are found to rise after stroke and heart attack.6,15,12,13
- 2018
A rabbit study shows Muse cells travel to the injured heart by sensing the S1P signal through their S1PR2 receptor. The first clinical trials of the donor Muse cell product CL2020 begin in Japan.16,42,55
- 2020
The first-in-human heart attack study of CL2020 (3 patients) is published.32
- 2021
The epidermolysis bullosa trial of CL2020 (5 patients) is published. In December, Mitsubishi Chemical says that instead of filing CL2020 for conditional, time-limited approval in Japan, it will seek full approval after a larger confirmatory study, with the agreement of Japan’s regulator, PMDA.33,55
- 2023
In February, Mitsubishi Chemical Group discontinues CL2020, citing “the latest clinical developments, timelines for commercialization, and its pharmaceutical business strategy.” Its announcement states no safety or efficacy concern. The same day, Prof. Dezawa publicly questions how the company presented the trial data. The randomized stroke trial (25 given CL2020, 10 placebo) and the ALS trial (5 patients) of CL2020 are published. By late 2023, the rights have returned to Prof. Dezawa and Tohoku University, which will lead development.54,56,34,35,59
- 2024
The spinal cord injury trial (10 patients) and the newborn brain injury trial (9 patients) of CL2020 are published.36,38
- 2025
A review by Prof. Dezawa reports that a Singapore company holds the rights to the basic Muse cell patents and licenses the isolation methods.41
- 2026
Systematic reviews of Muse cell isolation and of heart studies call for standardized methods and larger randomized trials. From July, Muse cell products are offered through private providers in four U.S. states without FDA evaluation or approval. These products are not CL2020, the product tested in the Japanese trials.43,44,61,62,63
Regulatory Status
No Muse cell product has been approved by the FDA, Japan’s PMDA or, as far as we know, any other regulator.53,73
Japan
CL2020’s developer had planned to seek conditional, time-limited approval for stroke, then decided with the regulator’s agreement to pursue full approval after a larger confirmatory study.55 In February 2023 it discontinued CL2020, citing its clinical development, timelines and business strategy, and stated no safety or efficacy concern.54 The rights returned to Prof. Mari Dezawa and Tohoku University.58,59 Whether new trials have been registered in Japan since 2024 is not confirmed.
United States
No Muse cell product is on the FDA’s list of approved cellular and gene therapy products.53 Since July 2026, Muse cell products have been offered through private providers in four states; the company that licenses them states they have not been evaluated or approved by the FDA.61,63 The regulatory basis for those providers is not stated in the materials we reviewed.
Elsewhere
We found no regulatory approval for any Muse cell product in any other country.
What We Don’t Know Yet
- Whether the encouraging early results hold up in larger, independent, controlled trials.39,44
- Long-term safety beyond about 18 months, and rare side effects that small trials cannot detect.39
- Whether injected Muse cells travel to injured tissue in people, as they do in animals.39
- How long donor cells survive in the body, and why they seem to avoid rejection.39
- Whether products made by other manufacturers, or from other tissues, behave like CL2020.39
- Standard methods to isolate and count Muse cells, which still vary between laboratories.43
Last reviewed against its sources: . How we check claims
Next: Areas Under Study
Have a Question About Muse Cell Research?
Dr. Albert’s team will read it and reply by email.