Vistrutide (UBT251)

A name that appears in no registry

Vistrutide is not the name on any trial protocol. The compound circulating under it is UBT251, described by its developer as a long-acting synthetic peptide agonist at the GLP-1, GIP and glucagon receptors. It originates with The United Bio-Technology (Hengqin) Co., Ltd., a wholly owned subsidiary of The United Laboratories International Holdings, and was licensed to Novo Nordisk in March 2025 for 200 million US dollars upfront, milestones of up to 1.8 billion, and tiered royalties outside Chinese mainland, Hong Kong, Macau and Taiwan. Every registered trial, every company announcement and the one conference abstract that exists use the development code. None of them uses vistrutide.

The name has the shape of an international nonproprietary name, and the stem would place it with retatrutide and the other triple agonists. WHO Proposed INN Lists 127 through 135 and Recommended Lists 91 through 95 were downloaded and searched in full text in August 2026. The string does not occur in any of them. The same search across the same files returned retatrutide in Proposed List 128 and tapimtrutide in Proposed List 135, so the method locates names of this class where they are present. On the published evidence, vistrutide is not a proposed or recommended INN.

Searches of PubMed, Europe PMC, Crossref, ClinicalTrials.gov, PubChem and the FDA Global Substance Registration System each returned zero records for the name. ClinicalTrials.gov holds twelve studies under UBT251 and none under vistrutide. Where the name occurs is on vendor product listings and on aggregator pages that appear to have taken it from them. Its origin could not be established. Only one of the two names has ever appeared on a trial protocol.

No published structure

Identity data for this compound does not exist in public form. PubChem returned PUGREST.NotFound for compound and substance queries under vistrutide, UBT251 and UBT-251. The FDA Global Substance Registration System returned zero substances for both names. A commercial drug-intelligence record lists UBT 251, UBT-251 and UBT251 as the only synonyms and carries no CAS number, formula or sequence; the corresponding entry in a second commercial drug-intelligence database sits behind authentication and could not be read. Every identity field on this page is therefore null rather than filled with a figure inherited from elsewhere.

What the developer has released is a category. The compound is a long-acting synthetic peptide with agonist activity at three receptors, and that is the whole of the public description. Residue count, non-standard residues, lipidation chemistry, molecular formula and mass have not been disclosed in a registry, a patent traceable to this molecule, or a publication. Material sold under either name cannot be identity-checked against a reference structure, because no reference structure has been published.

What is claimed about the receptors

Potent activity at all three receptors in a preclinical setting is asserted in the licensing announcement. No number accompanies the assertion. Searches of PubMed, Europe PMC and Crossref for in vitro characterisation of UBT251 returned no primary paper, no half-maximal effective concentration at any of the three receptors, and no statement of how the three activities are balanced against one another. Whether this molecule leans toward glucagon receptor signalling or away from it is, on the public record, unknown.

Goldney and colleagues make the same point from the other direction in their 2025 review of triple agonism, observing that agents in this class are likely to differ widely in affinity and potency at each hormone receptor. That is the variable the class is built on, and it is the variable no published source supplies for this compound. Comparisons drawn between UBT251 and retatrutide on receptor grounds are therefore comparisons between one characterised molecule and one that has not been characterised in public at all.

The phase 1b figure, and how it travelled

The licensing announcement of 24 March 2025 carries the first human numbers. It describes a randomised, double-blind, placebo-controlled phase 1b trial in China evaluating multiple subcutaneous injections in people with overweight or obesity. Thirty-six patients were enrolled across three dose groups, given as 1 mg, 1 mg/3 mg and 1 mg/3 mg/6 mg, each using titration, injected once weekly for twelve consecutive weeks. In the highest dose group the average weight of the people who completed the trial fell 15.1% from baseline, against an average increase of 1.5% in the placebo group.

The 15.1% is a completers analysis, not an analysis of everyone randomised. No per-group sample size, dispersion, confidence interval or p-value accompanies it. And the trial itself has no locatable registration. The two phase 1 records ClinicalTrials.gov holds for UBT251 (NCT07710729 and NCT07710768) are Novo Nordisk drug-interaction studies not yet open, neither of which is this trial; a sponsor search of The United Bio-Technology (Hengqin) returns nine studies whose single phase 1 entry is for a different molecule, UBT38006 (NCT07630233).

That figure has since crossed into the indexed literature. Park and colleagues, writing in Frontiers in Endocrinology in 2025, place 15.1% against a 1.5% placebo gain in a table of pipeline anti-obesity agents. Their citation for the row is the company news release. Goldney and colleagues, in Current Cardiovascular Risk Reports the same year, list the diabetes trial by its Chinese registry number CTR20250029 with sample size and endpoint recorded as not reported. Review articles are doing what they should; there is simply nothing underneath to cite.

Which arm produced 19.7 percent

Topline results from the Chinese phase 2 obesity trial were announced on 24 February 2026. The trial randomised 205 Chinese patients with obesity, defined as BMI at or above 28.0, or overweight at 24.0 to under 28.0 with at least one weight-related condition, to weekly subcutaneous UBT251 or placebo for 24 weeks. Baseline mean body weight was 92.2 kg. The highest mean weight loss observed was 19.7%, equal to 17.5 kg, against 2.0% and 1.6 kg on placebo. A footnote records that the figures follow the efficacy estimand, regardless of dose modification.

Arm-level numbers arrived four months later, in a late-breaking abstract presented at the American Diabetes Association Scientific Sessions and published in Diabetes as 3090-LB. Participants were randomised 2:1:1:2:2 to UBT251 at 2.0 mg, 4.0 mg with a 0.5 mg initial dose, 4.0 mg with a 1.0 mg initial dose, 6.0 mg, or placebo. Least-squares mean weight loss at week 24 was 13.6%, 16.2%, 19.7% and 18.7% respectively, against 2.0% on placebo, all at P<0.001. Mean age was 34.1 years, mean BMI 33.1, mean waist circumference 104.1 cm, and 59% of participants were female.

Read against each other, the two documents settle a point that secondary coverage got wrong. The 19.7% belongs to a 4.0 mg arm titrated from a 1.0 mg start; the 6.0 mg arm recorded 18.7%. The announcement never attributed the figure to a dose, only to the best-performing group, and several trade summaries converted that into a 6 mg result. The registry record and the abstract also list four active arms where the announcement lists three doses, because the two 4.0 mg arms differ only in starting dose.

The diabetes trial and its comparator

A second Chinese phase 2 trial reported on 25 March 2026. It randomised 211 Chinese patients with type 2 diabetes managed by lifestyle intervention alone or with metformin, double-blind, against both placebo and semaglutide 1 mg, for 24 weeks. Baseline mean HbA1c was 8.12%, mean body weight 80.1 kg and mean BMI 29.1. The primary endpoint was change in HbA1c at 24 weeks. The largest mean HbA1c reduction recorded on UBT251 was 2.16%, against 1.77% on semaglutide 1 mg and 0.66% on placebo. Mean body weight reduction reached 9.8%, against 4.8% and 1.4%.

Semaglutide 1 mg is a glycaemic dose; the weight-management presentation is 2.4 mg, so the body-weight column compares a triple agonist at its trial maximum against a comparator at a dose not selected for weight. The announcement gives no arm-level breakdown at all, so no dose result in this population is attributable: which arm produced the 2.16% is unpublished. As in the obesity trial, the registry record lists four active UBT251 arms — 2.0 mg, 4.0 mg from a 0.5 mg start, 4.0 mg from a 1.0 mg start and 6.0 mg — where the announcement names three doses (NCT07163624). That record also shows the trial completed on 30 December 2025 with no results posted, and Crossref returns no abstract for it.

Twelve registered trials, nothing reported

As of August 2026 ClinicalTrials.gov holds twelve studies naming UBT251. Two are complete, both phase 2 in China, at 205 and 211 participants, both first submitted to the registry on 1 September 2025 for trials that began the previous March. Four are recruiting: a phase 2 in chronic kidney disease at 180, a phase 2 in metabolic dysfunction-associated steatohepatitis at 156, a Novo Nordisk phase 2 in overweight or obesity at 333 across the United States and Canada, and a Novo Nordisk phase 2 in type 2 diabetes at 300. Four phase 3 trials in China and two phase 1 interaction studies have not yet opened. None of the twelve has posted results.

The publication position is narrower still. PubMed indexes nothing under either name. Crossref returns exactly one item, the ADA abstract, which PubMed does not index and which carries no correction notice. Europe PMC full-text search returns three articles containing the string UBT251, and all three are reviews: Park 2025, Goldney 2025 and Pardali 2026. None carries a retraction or expression of concern. The entire primary record for this compound is one conference abstract and three corporate announcements.

UBT251 is classed as a Class 1 innovative drug in China and has cleared clinical-trial applications there for type 2 diabetes, overweight or obesity, metabolic dysfunction-associated fatty liver disease and chronic kidney disease, and in the United States for type 2 diabetes, overweight or obesity and chronic kidney disease. Clearance to run a trial is not approval. The compound is not an approved medicine in any jurisdiction, and material offered outside a registered trial has not passed the identity, purity or sterility controls that govern investigational supply.

Longest exposure anywhere in that record is 24 weeks. Adverse events have been reported by category rather than by rate: gastrointestinal disorders were the most frequent class in both phase 2 trials and in the phase 1b, described as mostly mild to moderate, with no incidence figures, no discontinuation counts and no serious-event tally released. No heart-rate, body-composition, liver-fat or lipid figures have been published for this molecule. No cardiovascular outcome trial is registered.

What is not known

The published record runs to 24 weeks and no further. Nothing is established about durability, weight regain after discontinuation, or safety beyond six months. Adverse events have been described only by class, so incidence rates, discontinuation rates, serious-event counts and any dose relationship are unpublished. No heart-rate data exist, which matters for a molecule with glucagon receptor activity; no body-composition data exist, so the split between fat mass and lean mass in the recorded weight change is unknown; no liver-fat or lipid figures have been released despite improvements on those endpoints being asserted. Both completed trials enrolled Chinese adults only, with a mean age of 34.1 years in the obesity trial, and the global trials that would test generalisability do not report until 2027 at the earliest. Structure is undisclosed, so no independent laboratory can confirm that a given sample is this molecule. Nothing addresses use in pregnancy, lactation, adolescents, older adults, type 1 diabetes or renal impairment. UBT251 is not approved anywhere, and the name vistrutide has no regulatory standing at all.

Questions