Aleniglipron oral GLP-1: what its 36-week Phase 2b trial found

What the source reports

A peer-reviewed Phase 2b trial published in Nature Medicine tested aleniglipron, an experimental once-daily oral GLP-1 receptor agonist, in adults with obesity or overweight. Unlike peptide GLP-1 medicines, aleniglipron is a chemically manufactured small molecule.

The ACCESS trial randomly assigned 230 participants to escalating daily doses targeting 45 mg, 90 mg or 120 mg, or to placebo. At week 36, average weight reduction increased with dose and was statistically greater than placebo in all three aleniglipron groups.

This is a meaningful mid-stage development result, not an approval. Aleniglipron remains investigational, and the trial was designed to select doses and titration strategies for larger Phase 3 studies.

How the ACCESS trial worked

The study was randomised, double-blind and placebo-controlled across 38 sites in the United States. Participants and trial staff were not intended to know which treatment was assigned during the 36-week comparison.

Everyone assigned to aleniglipron began at 5 mg daily. The dose increased every four weeks until the participant reached the assigned 45 mg, 90 mg or 120 mg maintenance target. Placebo participants followed a matching schedule.

Participants had obesity, or overweight with at least one weight-related condition, and did not have diabetes. Their average age was 49.8 years, average body mass index was 39.5 kg/m² and average starting weight was 114.8 kg; 54% were women.

The weight-loss results

At 36 weeks, model-estimated average weight change from baseline was −9.0% with 45 mg, −10.7% with 90 mg and −12.1% with 120 mg, compared with −0.8% for pooled placebo. The corresponding placebo-adjusted differences were −8.2%, −9.8% and −11.3%.

In the 120 mg group, an estimated 86% of participants reached at least 5% weight loss, 70% reached at least 10%, and 38% reached at least 15%. The placebo figures were 23%, 7% and 1%, respectively.

These are group estimates, not expected outcomes for every user. The primary analysis estimated what would happen if eligible participants completed treatment, while a separate analysis that included data regardless of adherence produced a similar average of −11.4% in the 120 mg group.

Why a small-molecule tablet matters

Aleniglipron activates the GLP-1 receptor but is not a peptide copy of the natural hormone. Its small-molecule structure is intended to make oral dosing, conventional chemical manufacturing and simpler storage possible.

That could eventually affect manufacturing scale and how people choose between daily tablets and weekly injections. It does not establish that tablets will be cheaper, easier to access or preferable for every individual; those outcomes depend on approval, pricing, supply and real-world use.

The study did not directly compare aleniglipron with semaglutide, tirzepatide, orforglipron or another active treatment. Percentages from separate trials should not be used to rank medicines because their populations, duration, doses, analysis and support differ.

Gastrointestinal effects and discontinuation

The most common treatment-emergent adverse effects were gastrointestinal, including nausea, diarrhoea, vomiting and constipation. The trial actively asked participants to record these symptoms in an electronic diary after dose increases, which may capture more events than ordinary unsolicited reporting.

Across the aleniglipron groups, 10.4% discontinued treatment because of an adverse effect. Most of those discontinuations involved gastrointestinal symptoms and occurred during the earlier dose-escalation steps rather than after reaching the maintenance dose.

The investigators reported that gastrointestinal events were generally mild to moderate and became less frequent over time. That description should be read alongside the discontinuation rate: a side effect can be classified as mild or moderate yet still be difficult enough for an individual to stop treatment.

What the safety data can—and cannot—tell us

Serious treatment-emergent adverse events occurred in one participant in the 45 mg group, none in the 90 mg group, four in the 120 mg group and three receiving placebo. No deaths occurred during the trial.

The paper reported no drug-induced liver injury or persistent liver-enzyme elevation. Small temporary elevations occurred and returned to baseline without treatment being stopped. Average heart rate rose by approximately two to four beats per minute compared with placebo, depending on dose and measurement timing.

A 230-person, 36-week trial cannot reliably identify very rare harms or establish long-term safety. Larger Phase 3 studies and post-approval monitoring would be needed before the safety profile could be understood at population scale.

The extension offers an early clue, not a controlled answer

Participants who completed the blinded phase could enter a 36-week open-label extension. At a prespecified interim analysis, those continuing aleniglipron had further average weight reduction, with reported totals between 13.3% and 16.2% after 56 weeks depending on the original group.

The previous placebo group started aleniglipron at a lower 2.5 mg dose with smaller escalation steps. After a median 20 weeks, that group had 6.4% average weight reduction, no recorded vomiting and no adverse-effect-related discontinuations, although 39.9% reported nausea.

Because everyone knew they were receiving active treatment and follow-up lengths varied, the extension cannot provide the same level of comparison as the double-blind phase. It does, however, help researchers choose a lower starting dose for subsequent trials.

Who was—and was not—represented

All trial sites were in the United States and the participants were predominantly White. People with diabetes were excluded, as were those weighing 80 kg or less and people with several significant medical histories or recent use of weight-management medicines.

These criteria are useful for an early dose-ranging study but limit generalisation. The results do not establish how aleniglipron would perform in people with type 2 diabetes, more diverse populations, lower starting weights or complex health conditions.

Approximately three quarters of each treatment group completed the assigned study treatment. Missing data were handled with prespecified statistical models, but longer and larger trials will still need to examine persistence and adherence.

Sponsor involvement and the publisher correction

Structure Therapeutics funded the study. According to the paper, the sponsor designed the trial, collected and analysed the data, and participated in preparing the manuscript. Seven authors were company employees, while several academic authors disclosed relationships with Structure Therapeutics and other drug developers.

The article underwent peer review and provides its protocol, statistical plan and source data. It also received a publisher correction on 24 June 2026 involving figures for a 120 mg weight value and gastrointestinal-event presentation; the online article and PDF were updated.

Sponsor involvement does not invalidate the findings, but independent replication and regulatory review remain important—particularly when the company is developing the medicine commercially.

What remains uncertain

The trial cannot tell us whether aleniglipron maintains weight reduction for years, what happens after discontinuation, or whether it improves cardiovascular events, diabetes incidence, quality of life or other long-term health outcomes.

There is no head-to-head evidence showing how it compares with approved oral or injectable medicines. The optimal maintenance dose and the extent to which a slower starting schedule improves tolerability also require confirmation.

Phase 3 must reproduce the weight findings in a larger and more varied population while providing substantially more safety exposure. Regulatory approval is neither automatic nor guaranteed.

What this means for the individual

Aleniglipron is not an available treatment and should not be confused with an approved GLP-1 tablet. Trial doses cannot be converted into doses of another medicine because the compounds have different structures and pharmacology.

For someone currently receiving GLP-1 treatment, this research does not provide a reason to switch, change dose or seek an unapproved product. It shows what developers are testing and what evidence regulators will eventually need to assess.

The broader practical message is that oral options are expanding, but route of administration is only one part of treatment. Effectiveness, adverse effects, approved purpose, dosing instructions, access and individual medical history still matter.

Bottom line

In a well-controlled 230-person Phase 2b trial, once-daily aleniglipron produced dose-related average weight loss of up to 12.1% at 36 weeks, compared with 0.8% for placebo. The result supports moving the small-molecule oral GLP-1 into larger trials.

The 10.4% adverse-effect discontinuation rate, selected US population and short follow-up are equally important. Aleniglipron is a promising experimental tablet—not yet a proven long-term treatment or an approved alternative to current GLP-1 medicines.