When Novo Nordisk licensed UBT251 in March 2025, the evidence behind it was a 36-person phase 1b study in China. Novo agreed to pay $200 million upfront anyway, with up to $1.8 billion more in potential milestone payments. Now the first full UBT251 phase 2 obesity results have been published in Cell Metabolism, and they give the agreement a more substantial clinical dataset.
In 205 Chinese adults with overweight or obesity, the weekly injection produced average weight loss ranging from 13.6% to 19.7% at 24 weeks, compared with 2.0% on placebo. These were results from a randomized, double-blind, placebo-controlled trial involving people without type 2 diabetes.
The results are promising. They also come with an important limitation: 24 weeks is not enough to establish the full weight-loss potential, long-term safety or clinical durability of an experimental obesity medicine.
Novo Licensed a Triple Agonist After Just 12 Weeks of Human Data
UBT251 is a long-acting synthetic peptide designed to activate three hormone receptors: glucagon-like peptide-1, or GLP-1; glucose-dependent insulinotropic polypeptide, or GIP; and glucagon.
That is the same broad three-receptor strategy being investigated with Eli Lilly’s retatrutide, whose triple-agonist biology Grey Pepper has explained previously. The two molecules are different compounds, and sharing a receptor strategy does not mean that their clinical effects or safety profiles are interchangeable.
The scientific logic is to combine hormonal actions that influence appetite, glucose regulation and energy balance. GLP-1 and GIP signaling contribute to glucose control and weight regulation, while glucagon receptor activation may influence energy expenditure and liver metabolism.
Balancing those effects is complicated. Glucagon signaling can also increase glucose production, while activation of these hormonal pathways may affect heart rate, gastrointestinal function and other physiological processes. A successful triple agonist must produce sufficient benefit without making the treatment difficult to tolerate.
UBT251 was developed by United Biotechnology, a subsidiary of China’s The United Laboratories. Under the March 24, 2025 licensing agreement, Novo obtained exclusive rights to develop, manufacture and commercialize the compound outside mainland China, Hong Kong, Macau and Taiwan.
The agreement included a $200 million upfront payment, up to $1.8 billion in additional potential milestones and tiered royalties on net sales in Novo’s territories. The milestone ceiling represented conditional future consideration, not another $1.8 billion already paid.
At the time, the most attention-grabbing human result came from a 36-person phase 1b trial. In the highest-dose group, participants who completed 12 weeks of treatment lost an average of 15.1% of their starting body weight, compared with a 1.5% average gain among placebo recipients.
Those early findings offered an encouraging signal but limited certainty. The trial was small, relatively short and primarily designed to investigate safety, tolerability and pharmacological behavior.
Novo made a substantial licensing commitment before the compound had completed a larger randomized phase 2 obesity trial. The October 2026 publication provides a more rigorous basis for evaluating that decision.
The UBT251 Phase 2 Results: Four Dose Groups and Up to 19.7% Weight Loss
The obesity study was published online in Cell Metabolism on October 8, 2026. It enrolled 205 Chinese adults aged 18 to 61 years with overweight or obesity but without type 2 diabetes. Women represented approximately 59% of the participants.
Participants were randomly assigned to receive once-weekly subcutaneous UBT251 at a target dose of 2 mg, 4 mg or 6 mg, or placebo, over 24 weeks.
The investigators also divided the 4 mg dose into two groups with different starting doses: 0.5 mg and 1 mg. This allowed the study to investigate whether the initial dose and escalation approach influenced efficacy and tolerability.
The primary endpoint was percentage change in body weight from baseline to week 24. The least-squares mean changes were substantial across all UBT251 groups.
| Treatment group | Mean weight change at 24 weeks |
|---|---|
| UBT251 2 mg | −13.6% |
| UBT251 4 mg, starting at 0.5 mg | −16.2% |
| UBT251 4 mg, starting at 1 mg | −19.7% |
| UBT251 6 mg | −18.7% |
| Placebo | −2.0% |
The largest observed reduction was 19.7% in the 4 mg group that began treatment at 1 mg. Notably, this result exceeded the 18.7% reduction observed in the 6 mg group.
That matters because the results do not show a strictly increasing response at every higher target dose. Dose escalation strategy, individual variation and the relatively small size of some groups may all influence the observed pattern. The results should not be interpreted as proof that 4 mg will always outperform 6 mg.
After accounting for the 2.0% weight reduction in the placebo group, the placebo-adjusted differences ranged from 11.5 to 17.7 percentage points. All UBT251 groups were statistically superior to placebo on the primary endpoint.
The investigators also reported improvements in waist circumference, body mass index, blood pressure, lipid measures and markers of glucose regulation.
Those findings extend the evidence beyond weight change alone. However, improvements in cardiometabolic risk markers over 24 weeks are not equivalent to demonstrating fewer heart attacks, strokes or other major clinical outcomes.
The Companion Diabetes Trial Adds a More Demanding Comparison
A separate UBT251 phase 2 study involving people with type 2 diabetes was published in Cell Metabolism on October 26, 2026.
This trial enrolled 211 Chinese adults with diabetes and included an active comparator: once-weekly semaglutide 1 mg. Participants were assigned to several UBT251 regimens, semaglutide or placebo for 24 weeks.
The primary outcome focused on glycated hemoglobin, or HbA1c, a measure of average blood glucose over approximately three months.
UBT251 produced least-squares mean HbA1c reductions ranging from 1.98 to 2.16 percentage points. The corresponding changes were 1.77 percentage points with semaglutide 1 mg and 0.66 percentage points with placebo.
Weight loss was also greater in the UBT251 groups than with either comparator. The study reported reductions of up to 9.8% with UBT251, compared with 4.8% for semaglutide and 1.4% for placebo.
The active comparator makes these findings particularly informative. Unlike an indirect comparison against separate studies, this trial evaluated UBT251 and semaglutide within the same randomized research program.
There is still an important qualification. The comparator was semaglutide 1 mg, a dose used in diabetes treatment. It was not the higher semaglutide doses studied and used for obesity management.
Consequently, the diabetes trial does not establish that UBT251 is superior to every clinically relevant dose of semaglutide, nor does it demonstrate superiority over tirzepatide or retatrutide.
The two phase 2 trials also involved different populations. Adults with type 2 diabetes often experience different weight-loss responses from adults without diabetes, making direct comparisons of the headline percentages inappropriate.
Together, the obesity and diabetes studies strengthen the evidence that UBT251 has meaningful metabolic activity. They do not yet resolve its long-term comparative effectiveness.
Why 24 Weeks Is Still the Catch
Some of the largest weight-loss results reported in modern obesity medicine come from trials lasting 48 to 72 weeks or longer. Weight can continue to decline for many months before reaching a plateau, and the timing of that plateau differs among treatments and populations.
A mean reduction of 19.7% after 24 weeks is therefore striking. But it cannot be placed beside longer results from other drugs as though the studies had identical designs, participants, doses and observation periods.
A strong 24-week curve is evidence of what happened during the first six months. It is not a measurement of where weight loss will eventually stabilize.
The population also matters. The obesity trial involved Chinese adults without diabetes, with an average baseline weight of approximately 92 kilograms and a mean body mass index of about 33.
Those characteristics define the participants for whom the results were observed. Larger studies across different geographic populations, baseline weights, age groups and medical conditions will be needed to determine how broadly the findings apply.
Safety and tolerability are another limitation. The most frequently reported treatment-emergent adverse events were gastrointestinal problems, including symptoms commonly observed with incretin-based medicines.
Novo’s November 4 investor presentation reported treatment-emergent adverse events in 92.3% of participants in its 4 mg grouping, compared with 88.0% on placebo. Discontinuations due to adverse events occurred in 4% of the 4 mg grouping, with none reported in the 2 mg, 6 mg or placebo groups in that summary.
These figures do not mean that most participants experienced serious adverse events. The majority of gastrointestinal symptoms described in the publication were mild to moderate. Nevertheless, adverse-event frequency, severity and treatment discontinuation will matter greatly in larger trials.
Multi-receptor medicines can present challenging tradeoffs between effectiveness and tolerability. The dual GLP-1 and glucagon agonist survodutide, for example, demonstrated substantial weight reduction in phase 3 but also raised questions about gastrointestinal tolerability and discontinuations, which Grey Pepper explored in its coverage of survodutide’s phase 3 results.
UBT251’s two 4 mg escalation regimens offer useful evidence for investigating those tradeoffs. But short-duration studies cannot establish the full safety profile, particularly for uncommon events or complications that may emerge after prolonged treatment.
Other unanswered questions include changes in heart rate, preservation of lean mass, long-term glucose control, treatment persistence and what happens after the medicine is discontinued.
Novo Has a Phase 3 Plan, but UBT251 Has Not Proven Long-Term Success
UBT251 now occupies a more credible position in Novo’s obesity pipeline than it did when the licensing agreement was announced in March 2025.
The original decision was based largely on early safety and weight-loss signals from a small phase 1b trial. The published phase 2 studies add randomized evidence from separate populations with and without type 2 diabetes.
The development strategy has also become clearer. In its November 4, 2026 investor presentation, Novo outlined an expected phase 1b/2a obesity trial readout in the first half of 2027 and plans to initiate a phase 3 weight-management program around mid-2027.
Those are planned milestones, not completed studies. The timing may change, and the future program will need to address questions that the current phase 2 evidence cannot answer.
The company has also identified sleep apnea and metabolic dysfunction-associated steatohepatitis, or MASH, as potential future indications for investigation. These remain development possibilities rather than established benefits of UBT251.
There is a broader competitive question. Novo is developing UBT251 alongside CagriSema and several other obesity candidates, while Eli Lilly continues to advance retatrutide and other metabolic therapies.
UBT251’s 24-week results suggest it could become an important candidate within the triple-agonist class. But claims of superiority over competing medicines require appropriately controlled comparative evidence, not comparisons between different clinical trials.
The research also has commercial context. The phase 2 obesity publication disclosed involvement by employees of United Biotechnology and Novo Nordisk, with other investigators receiving research funding from the study sponsor. Such relationships are common in pharmaceutical development but remain relevant to transparent interpretation of the evidence.
The next major tests will examine how effectively UBT251 performs beyond six months, whether its adverse-event profile remains manageable in larger populations and whether its benefits justify continued development alongside competing medicines.
For now, UBT251 has passed a milestone that many early licensed drug candidates never reach: published randomized phase 2 evidence of substantial weight reduction in humans.
That makes Novo’s original $200 million upfront commitment look more scientifically grounded than it did when the public evidence involved only 36 participants. It does not establish that the investment will become commercially successful or that the drug will ultimately receive regulatory approval.
The next test is not whether UBT251 can produce an impressive six-month number. It is whether those results can be sustained, reproduced and safely extended into the longer trials required for a new obesity medicine.
Original obesity study: Zhou Z. et al. UBT251, a novel triple GLP-1, GIP, and glucagon receptor agonist, in adults with overweight or obesity: A multicenter, randomized phase 2 trial. Cell Metabolism, published October 8, 2026.
Companion diabetes study: Zhou Z. et al. UBT251, a novel triple GLP-1, GIP, and glucagon receptor agonist, in adults with type 2 diabetes: A multicenter, randomized phase 2 trial. Cell Metabolism, published October 26, 2026.
Licensing announcement: The United Laboratories and Novo Nordisk announce exclusive license agreement for UBT251, March 24, 2025.
Development update: Novo Nordisk Q3 2026 investor presentation, slide 59, November 4, 2026.
