Orforglipron ACHIEVE-1: first Phase 3 oral GLP-1 readout
Results from the ACHIEVE-1 trial, published in the New England Journal of Medicine in 2025, represent the first Phase 3 data for an orally administered GLP-1 receptor agonist. Once-daily orforglipron — a small-molecule, non-peptide GLP-1 agonist developed by Eli Lilly — achieved 12.4–14.7% mean weight loss at 36 weeks in adults with obesity or overweight with weight-related comorbidities.
The randomised, double-blind, placebo-controlled trial enrolled adults with a body-mass index of 30 or higher (or 27 with comorbidities). Participants received orforglipron at one of two dose levels or placebo. Both orforglipron arms demonstrated statistically significant weight loss compared with placebo (p<0.001), with the higher-dose arm achieving the greatest reduction.
How oral delivery changes the landscape
Current leading GLP-1 therapies — semaglutide (Wegovy) and tirzepatide (Mounjaro/Zepbound) — require subcutaneous injection, typically once weekly. An effective daily oral tablet could remove a significant barrier to adherence and access, particularly for patients reluctant to self-inject.
Orforglipron is chemically distinct from injectable peptide GLP-1 agonists: it is a small-molecule agonist of the GLP-1 receptor rather than a peptide, which enables oral bioavailability. This distinguishes it from oral semaglutide (Rybelsus), which uses an absorption-enhancer technology but remains a peptide with strict dosing conditions.
Safety profile
The most commonly reported adverse events were gastrointestinal in nature — nausea, diarrhoea, vomiting, and constipation — consistent with the known side-effect profile of GLP-1 receptor agonists. Discontinuation rates due to adverse events were higher in the orforglipron arms than placebo but broadly comparable to those seen with injectable GLP-1 therapies in Phase 3 programmes.
What it means for UK researchers
Orforglipron is not yet licensed in the UK; it remains an investigational compound under clinical development. The ACHIEVE-1 results support its progression toward regulatory submission, with Eli Lilly expected to file with the FDA and EMA. If approved, orforglipron would be the first oral GLP-1 agonist specifically indicated for obesity in the UK market.
For researchers, the data underscore a broader trend: the peptide and peptide-mimetic metabolic pipeline is moving toward oral formulations. Orforglipron's mechanism — full GLP-1 receptor agonism via a non-peptide scaffold — illustrates how small-molecule approaches can replicate the pharmacology of injectable peptides.
Looking ahead
Additional Phase 3 trials (ACHIEVE-2, ACHIEVE-3) are underway, evaluating orforglipron in type 2 diabetes and against comparator GLP-1 therapies. Results from these programmes will determine orforglipron's ultimate positioning relative to semaglutide and tirzepatide.
For a full compound profile, mechanism of action, and UK legal status, see our orforglipron profile.
This article is for research and educational purposes only. Orforglipron is an investigational compound, not a licensed medicine. Nothing here constitutes medical advice.
This article is AI-researched and editorially reviewed. It is provided for research and educational purposes only and is not medical advice. Research peptides are not licensed for human consumption in the UK.