UBX0101 dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
UBX0101 is the first clean-up drug for worn-out cells tested in a proper study against a real symptom. In 183 people with knee arthritis, knee pain at 12 weeks was the same on every dose as on a dummy shot, according to results the maker posted to the US trial registry.
Evidence grade for UBX0101: Moderate. The rule: at least one finished study in people, and at least 100 people who took it. The sum on this page: 1 completed trial, 183 people given it. A grade counts how much has been done to people, not whether it works.
- People given it
- 183
- Human studies
- 1
- Found nothing
- 0
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
1 completed trial, 183 people given it
3 effects reported, 3 unwanted, by people using it, not a trial
Goal pages: Injury, healing and recovery, Bone and joints
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
UBX0101 was an experimental knee shot from Unity Biotechnology. It was meant to kill worn-out cells in arthritic knees. It failed its main study. It is not approved and is no longer being developed for knees.
What people take it for
- Knee arthritis pain.
- Proof that clearing worn-out cells helps people.
What studies in people showed
183 people with knee arthritis got one knee shot of UBX0101 or a dummy shot. After 12 weeks, knee pain had dropped by about half in every group. It went from about 2.1 to 1.12 on the dummy shot, and to 1.04 to 1.16 on the drug. No difference. A follow-up of 161 people was stopped because it could not reach its goals. Two early safety studies, with 78 and 35 people, never posted results. In mice, clearing worn-out cells in the knee eased arthritis and pain.
What people report
Reports, not study results
The good
- We have not collected user reports on this one yet.
The bad
- Serious side effects: 1 of 46 on the dummy shot, and 2, 1 and 3 on the three doses.
- One person on the highest dose died. The record gives no cause.
- Results from 113 people in two safety studies were never made public.
Where these come from: Everything here is from the results posted on the US trial registry, listed on this page. There are no forum reports, since the drug was never sold.
My bottom line
This is the best test so far of clearing worn-out cells in people, and it failed. Remember it next time someone sells you a clean-up drug based on mouse studies.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Measured in people
Goals UBX0101 has been tested for in people, biggest studies first. We count only what the studies on this page say, so the real numbers may be higher.
- Joint and knee pain183 people · 1 study
Animal and lab work, not yet tested in people
Real results, but from animals or cells, not people. What works in a mouse often does not work the same way in a person. Nobody can patent this, so nobody would ever earn back the cost of a study in people. That is usually why there is none. The record on this one is set out below.
- Tendon, ligament and injury healing1 animal or lab study
34 of the 36 indexed goals have no study of any kind behind UBX0101
No study in people, animals or cells on this page reports a result for these. That does not prove UBX0101 does nothing for them. It does mean anything you have heard about UBX0101 and one of these did not come from a study cited here.
Show full evidence
What is UBX0101?
UBX0101 is the first clean-up drug for worn-out cells tested in a proper study against a real symptom. In 183 people with knee arthritis, knee pain at 12 weeks was the same on every dose as on a dummy shot, according to results the maker posted to the US trial registry.
UBX0101 is a small drug from Unity Biotechnology, made to be injected straight into an arthritic knee. It is meant to push worn-out cells to die. It is not the same drug as UBX1325, also called foselutoclax, which Unity tested in eye disease.
The study in people failed, and the results are on the US trial registry. 183 people with painful knee arthritis got one shot in the knee. It was either a dummy shot or UBX0101 at 0.5, 2.0 or 4.0 mg. The main test was knee pain at 12 weeks. Pain fell in every group, from about 2.1 at the start to 1.12 on the dummy shot. On the three doses it was 1.16, 1.04 and 1.10. There is no difference between the drug and the dummy shot in those numbers. Serious side effects happened to 1 of 46 people on the dummy shot, and to 2, 1 and 3 people on the rising doses. One person on the 4.0 mg dose died, and the record gives no cause. A long-term follow-up of 161 of these people was stopped. The registry says it was because the study could not reach its goals.
The common claim that this study failed could not be traced to a published paper. You can check it on the registry, which is where the numbers above come from.
In mice, the reason to try it looked strong. A 2017 paper used mice bred so worn-out cells could be tracked and killed. After a knee ligament injury, worn-out cells built up in the joint. Clearing them eased arthritis and pain and helped cartilage grow. A clean-up drug injected into the knee did the same in normal and old mice. A 2023 paper found UBX0101 cut protein damage in old arthritic mouse knees, with different results in young and old mice.
No clean-up drug has improved health in a proper study in people, and UBX0101 is the clearest example.
How does UBX0101 work?
Shown in mice and in cells: UBX0101 blocks a protein that normally breaks down p53, a protein that tells damaged cells to die. With more p53 around, worn-out cells, which rely on keeping p53 down to survive, die off. It is injected straight into the joint, to keep the effect in the knee. In people, the studies did not check whether the shot cleared worn-out cells from the joint. They measured pain and function, not worn-out cells.
What have studies in people found about UBX0101?
Four registered studies in knee arthritis: two early safety studies, one larger study with results posted to the US registry, and a long-term follow-up that was stopped. The larger study showed no difference from a dummy shot on knee pain. No published paper on any of these studies was found.
- 183 people, one shot in the knee of UBX0101 or a dummy shot. Knee pain at week 12: 1.12 on the dummy shot, and 1.16, 1.04 and 1.10 on the 0.5, 2.0 and 4.0 mg doses, from starting scores of 2.05 to 2.20. Paid for and reported by the maker.
- Other results in the same study, knee function and average daily pain, also showed no difference at week 12 or week 24.
- Serious side effects by group: 1 of 46 on the dummy shot, and 2 of 45, 1 of 46 and 3 of 46 on the drug. One death on the 4.0 mg dose, with no cause given in the record.
- A long-term follow-up of 161 of those people was stopped. The registry says it could not reach its goals.
- Two early safety studies, with 78 and 35 people, were both marked finished. Neither has posted results or a published paper.
What this does not tell you: One shot into one knee, checked for 12 weeks, cannot rule out that repeat shots, a different drug or a different body part would work differently. It also cannot tell you whether worn-out cells were cleared, because the study measured pain and function, not worn-out cells. What it does show is that clearing worn-out cells this way did not ease knee pain more than a dummy shot in 183 people.
The state of the research
This drug is the single most useful result in the clean-up field, and it is almost missing from published research. Three finished studies and a stopped follow-up produced one posted set of results and no paper we could find. The study's failure is repeated a lot in commentary. The source you can check is the registry, and this page takes its numbers from there, not from the commentary.
The dummy shot group is the other lesson. Knee pain fell by about half on the dummy shot. That is normal in knee injection studies. It is exactly why a clean-up drug study with no dummy group that reports people got better proves very little. The small studies behind the public claims that clean-up drugs help people function better had no dummy group like this one.
The evidence, in charts
Fig. 1a · how many people
183people, across 1 study in people cited here
| Study | People | Share |
|---|---|---|
| ClinicalTrials.gov 2026 | 183 | 100% |
The whole total is one study of 183. Counts are the number of people each study on this page says it signed up. That includes studies that only watched people and gave nobody the compound. 3 more studies in people give no headcount and are not counted here. Studies still signing people up are left out, and only studies cited on this page are counted.
Fig. 1b · evidence mix
4 of 6 sources here are studies in people. The rest are not.
- Study in people · done in people467%
- Animal study · done in animals233%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
The studies cover 3 different years, 2017 to 2026, counted from the list of sources on this page.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 4 · how much does what
Nobody has tested different amounts in people
This chart would show how the effect changes as the amount goes up. For this compound, nobody has measured that in people. So we leave it empty. We will not borrow an animal chart and pretend it works the same in people.
Fig. 5 · what the molecule is
- Kind of compound
- Small molecule
- Molecule weight
- Not on file
- Half-life
- None on file
- Chain length
- None on file
No amino acid sequence is on file for UBX0101, which is expected: a small molecule is not built from amino acids.
The studies we cite
- Study in people2026A Study to Assess the Safety and Efficacy of a Single Dose of UBX0101 in Patients With Osteoarthritis of the Knee
The first clean-up drug ever tested against a real symptom in people failed. 183 people with knee arthritis got one shot of UBX0101 at one of three strengths, or a dummy shot. After 12 weeks, knee pain had fallen from about 2.1 to 1.12 on the dummy shot and to between 1.04 and 1.16 on the drug. Knee function and daily pain matched too. One person in the highest dose group died, with no cause given in the record.
Unity Biotechnology, phase 2, randomised, triple masked, 183 participants (placebo 46, UBX0101 0.5 mg 45, 2.0 mg 46, 4.0 mg 46). Results posted December 2021. WOMAC pain subscale fell from about 2.1 at baseline to 1.12 on placebo versus 1.16, 1.04 and 1.10 on the three doses at week 12. Function and daily pain scores likewise showed no separation. Serious adverse events 1, 2, 1 and 3 by arm; one death recorded in the 4.0 mg arm, cause not given in the posting.
- Study in people2026Long-Term Follow-Up Study of Patients With Osteoarthritis of the Knee Treated With UBX0101
The follow-up study was stopped because the drug had not worked. 161 people had signed up. The registry says it was stopped because it could not reach its goals, which is the maker's own way of saying it failed. We checked the record was live in September 2026. A stopped follow-up is a result, not a gap.
161 participants enrolled, status TERMINATED. The registry states the reason for stopping as inability to achieve primary or secondary study objectives. Verified live September 2026.
- Study in people2026A Safety and Tolerability Study of UBX0101 in Patients With Osteoarthritis of the Knee
This study was run, finished, and never reported. 78 people took part in an early safety test of UBX0101 in knee arthritis. The registry marks it finished and posts no results. We could not find a published paper either. So the safety data from 78 people who got the shot is not available to anyone outside the company.
Phase 1, 78 participants, status COMPLETED. No results are posted on the registry record and no peer-reviewed publication of this trial was located.
- Study in people2026A Study of Single and Repeat Dose Administration of UBX0101 in Patients With Osteoarthritis of the Knee
Another UBX0101 safety study finished and vanished. 35 people got one or more doses in this early study. The registry marks it finished, posts no results, and no paper could be found. Two of the four registered UBX0101 studies ended this way. What those people went through is not on the public record.
Phase 1 single and repeat dosing, 35 participants, status COMPLETED. No results posted and no publication located.
- Animal study2017Local clearance of senescent cells attenuates the development of post-traumatic osteoarthritis and creates a pro-regenerative environment
In mice. In mice bred so worn-out cells could be tracked and killed, clearing worn-out cells after a knee ligament injury eased arthritis and pain and helped cartilage grow. A clean-up drug injected into the knee did the same in normal and old mice. Cells from people having knee replacements were treated in a dish, not in the people.
Mouse. Using the p16-3MR transgenic model after anterior cruciate ligament transection, selective elimination of senescent cells attenuated post-traumatic osteoarthritis, reduced pain and increased cartilage development, reproduced by intra-articular injection of a senolytic molecule in transgenic, non-transgenic and aged mice. Cells from patients undergoing knee replacement were treated in culture, not in the patients.
- Animal study2023Senolytic treatment reduces oxidative protein stress in an aging male murine model of post-traumatic osteoarthritis
In mice. UBX0101 cut protein damage in old arthritic mouse knees. Young and old mice responded differently, which suggests any benefit depends on how old the joint is.
Mouse. UBX0101 reduced protein oxidative modification in aged arthritic knee joints, with divergent responses between young and aged animals, suggesting the benefit of senolysis in the joint depends on the age of the tissue.
Common questions
Has UBX0101 been tested in people?
Yes. 183 people given it across 1 completed trial cited here, 0 of which found nothing. UBX0101 is the first clean-up drug for worn-out cells tested in a proper study against a real symptom. In 183 people with knee arthritis, knee pain at 12 weeks was the same on every dose as on a dummy shot, according to results the maker posted to the US trial registry.
What is the UBX0101 dosage?
No human dose established. Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose. 1 completed trial, 183 people given it
Is UBX0101 FDA-approved?
Not approved. Still investigational. The mid-stage study in osteoarthritis, the wear-and-tear kind of arthritis, finished in 2020. Its results were posted to ClinicalTrials.gov in December 2021. The long-term follow-up study was stopped because it could not meet its main or other goals.
Did the UBX0101 osteoarthritis trial fail?
The posted results show no difference from a dummy shot. In 183 people, knee pain at 12 weeks was 1.12 on the dummy shot and 1.16, 1.04 and 1.10 on the three doses. The long-term follow-up was stopped, and the registry says it could not reach its goals. No published paper on the study was found, so the registry is the source.
Is UBX0101 the same as UBX1325?
No. UBX0101 was injected into arthritic knees and works by protecting p53, a protein that tells damaged cells to die. UBX1325, also called foselutoclax, blocks a different protein, BCL-xL, and is injected into the eye for eye disease. Same company, different drugs, different programs.
Why did the placebo group improve so much?
Getting a shot of anything in a painful knee makes it feel a lot better in studies. That is why having a dummy shot group matters here. Knee pain fell by about half on the dummy shot, about the same as on every dose of the drug.
Does this mean senolytics do not work?
It means one clean-up drug, given once into one knee, did not beat a dummy shot on knee pain over 12 weeks in 183 people. It is the only proper study of a clean-up drug against a symptom that has reported results. As of September 2026, no clean-up drug has improved health in a proper study in people.