Semaglutide

Semaglutide is a selective GLP-1 receptor agonist with extensive Phase 3 clinical trial data supporting its mechanisms in humans.

The displayed 31-residue backbone is a sequence shorthand, not the complete chemical structure: residue 2 is aminoisobutyric acid (Aib), residue 20 is the lysine acylated through a linker with a C18 fatty diacid, and residue 28 is arginine. NIH’s substance record and the FDA Wegovy label identify these structural features.

How It Works (Simplified)

Semaglutide mimics GLP-1, a natural hormone released after eating, producing multiple therapeutic effects:

Key Research: STEP 1 randomized 1,961 adults with overweight or obesity to injectable semaglutide 2.4 mg or placebo and reported 14.9% versus 2.4% mean weight reduction at 68 weeks (PMID:33567185). A separate 72-person mechanistic study measured lower ad libitum lunch intake (PMID:33269530); it was not an outcomes trial.

2025-2026 Developments

Oral Wegovy and Wegovy HD: The current FDA Wegovy label distinguishes 25 mg oral tablets, labeled for adult weight reduction and for major cardiovascular event reduction in adults with established cardiovascular disease and overweight or obesity, from the injection. Wegovy HD 7.2 mg injection is labeled for additional weight reduction in selected adults. The tablet and 7.2 mg injection have not established safety and effectiveness for pediatric use or MASH; 7.2 mg is not the labeled cardiovascular or MASH maintenance dose. In STEP UP, 7.2 mg produced 20.7% mean weight loss under the efficacy estimand; the FDA label also reports dysesthesia in 22% at 7.2 mg, 6% at 2.4 mg, and 0.3% with placebo across its higher-dose trials. These are indication- and dose-specific results.

MASH Indication: Wegovy injection received US accelerated approval for adults with noncirrhotic MASH and F2-F3 fibrosis on the basis of histologic MASH and fibrosis endpoints. The FDA label says continued approval may depend on confirmatory clinical benefit; oral Wegovy has no MASH indication.

Acute kidney injury: The FDA label warns of acute kidney injury due to volume depletion, including with persistent GI adverse reactions. A FAERS disproportionality signal (PMID:41227073) cannot estimate incidence or establish causation.

Anti-doping status: WADA’s 2026 Monitoring Program lists markers of semaglutide and tirzepatide in and out of competition. Monitoring is expressly for substances outside the Prohibited List and is not a prohibition.

Head-to-head against a combination product (REIMAGINE 2). REIMAGINE 2, published on 7 June 2026, put semaglutide 2.4 mg and 1.0 mg directly against cagrilintide-semaglutide and against cagrilintide alone in 2,713 adults with type 2 diabetes across 30 countries over 68 weeks (PMID:42251859, NCT06065540). On the efficacy estimand, which the paper names as primary, HbA1c fell 1.91 percentage points on the combination against 1.75 on semaglutide 2.4 mg. The difference of 0.16 percentage points (95% CI 0.05 to 0.27) reached statistical significance. Read from semaglutide’s side, that is the size of the gap a second mechanism opened over semaglutide alone in this population, and it came with more adverse events: 86.9% versus 81.2%.

Indirect comparison with orforglipron. A population-adjusted indirect treatment comparison built oral semaglutide 25 mg against orforglipron 36 mg using individual patient data from OASIS 4 and aggregate data from ATTAIN-1 (PMID:42225305). It reported greater weight loss with oral semaglutide by 3.2 percentage points on the treatment-regimen estimand (95% CI -5.9 to -0.4) and 3.0 points on the efficacy estimand (95% CI -5.8 to -0.3), and higher discontinuation with orforglipron. Two caveats belong beside that result: the analysis is indirect, comparing arms from separate trials rather than randomised head-to-head, and it was funded and authored by the manufacturer of the winning compound.

STEP 12 — semaglutide 2.4 mg in Chinese adults. STEP 12 was a phase 3b trial at 19 sites across mainland China and Taiwan, published in Lancet Diabetes & Endocrinology on 10 August 2026 (PMID:42575111, NCT06041217). It enrolled 242 adults at locally defined BMI thresholds — 24 to under 28 with a weight-related comorbidity, or 28 to under 30 — randomised 2:1 to semaglutide 2.4 mg or placebo for 44 weeks. Body weight fell 12.1% versus 2.2%, an estimated treatment difference of 9.9 percentage points (95% CI -11.8 to -8.0), and 80.5% versus 24.4% reached at least 5% reduction. The BMI entry thresholds are lower than in the Western STEP trials, which is the point of the trial and also the limit on transferring its numbers.

OASIS 2 — oral semaglutide 50 mg in an East Asian population. OASIS 2 was a 68-week phase 3a trial in Japan and South Korea, published in JAMA Internal Medicine in October 2025 (PMID:40758358, NCT05132088). Of 201 participants, about a quarter had type 2 diabetes. Body weight fell 14.3% versus 1.3% on placebo, an estimated treatment difference of 13.07 percentage points (95% CI -15.61 to -10.52), and 84.3% versus 17.2% reached at least 5% reduction. Gastrointestinal adverse events were reported by 63.4% of the semaglutide group.

REALYSE — registry results only. REALYSE (NCT05035082, phase 4, n=1,018) posted results to ClinicalTrials.gov on 10 August 2026. A dateless PubMed search on 17 August 2026 for both the registration number and the trial name returned no indexed publication, so no figures are quoted from it here.

Important Limitations

• The favourable indirect comparison against orforglipron was authored and funded by semaglutide’s manufacturer, and indirect comparisons cannot substitute for a head-to-head trial
• Common GI side effects: Nausea (30-45%), vomiting, diarrhea, and constipation, especially during dose titration
• Boxed warning: Thyroid C-cell tumors observed in rodents; contraindicated in personal/family history of medullary thyroid carcinoma (MTC) or MEN2
• Gallbladder disease: A labeled warning; trial incidence varies by product, dose, population, and event definition.
• Pancreatitis: A labeled warning; the FDA label directs discontinuation if suspected. Trial rates vary by product and population.
• Pregnancy: Wegovy is not contraindicated under label section 4 for pregnancy, but the label’s instructions differ by indication: discontinue when pregnancy is recognized for weight or CV indications; for MASH, use only if the potential benefit justifies fetal risk. Its preconception language also depends on indication.
• Weight regain: About two-thirds of prior loss returned within one year in the STEP 1 extension subset after drug and structured lifestyle intervention stopped (PMID:35441470); this estimate is not from STEP 4.
• Body composition: Trial lean-mass changes depend on the measurement and population; a universal percentage of weight lost as muscle is not established here.