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Aleniglipron Phase 2 Shows 16% Weight Loss in Oral Trial

Structure Therapeutics' aleniglipron hit 16.3% placebo-adjusted weight loss in Phase 2 ACCESS II — no liver injury or QTc signals across 625 participants.

May 19, 2026 · 3 min read

Structure Therapeutics announced positive topline data from its Phase 2 ACCESS II trial on March 16, 2026, showing its once-daily oral GLP-1 receptor agonist aleniglipron delivered 16.3% placebo-adjusted weight loss at 44 weeks at the 180 mg dose — without the liver injury or cardiac safety concerns that have shadowed earlier small-molecule GLP-1 candidates. The company expects an End-of-Phase 2 meeting with FDA in Q2 2026, with Phase 3 launch targeted for the second half of 2026.

What happened

ACCESS II enrolled more than 625 participants across multiple cohorts with obesity (BMI ≥30) or overweight with comorbidities. The primary cohorts tested once-daily oral aleniglipron at 120 mg, 180 mg, and 240 mg, with a starting dose of 5 mg titrated up over approximately 16 weeks.

Efficacy results at 44 weeks (placebo-adjusted):

  • 180 mg: -16.3% mean body weight loss (-39 lbs)
  • 240 mg: -16.0% mean body weight loss (-37 lbs)
  • No evidence of a weight-loss plateau at week 44

An open-label extension showed continued weight loss, with the 120 mg cohort reaching -16.2% (40.5 lbs) by week 56. A separate lower-start-dose cohort (2.5 mg starting dose) achieved approximately -6.8% weight loss at 20 weeks with notably fewer GI-related discontinuations than the 5 mg start cohort.

The safety read was notably clean: across more than 625 participants, there were no cases of drug-induced liver injury (DILI), no persistent liver enzyme elevations, and no QTc prolongation. Earlier small-molecule GLP-1 receptor agonists, including some candidates abandoned in Phase 1-2, had raised concerns about hepatotoxicity or cardiac conduction effects. Aleniglipron appears to avoid both.

Why it matters

Until recently, the oral GLP-1 landscape looked like a two-horse race: Novo Nordisk's oral semaglutide (approved as the Wegovy pill in December 2025, requiring 30-minute pre-meal fasting) and Lilly's orforglipron/Foundayo (approved April 1, 2026, with no food restrictions). Aleniglipron, if it passes Phase 3, would be a third entrant — and based on Phase 2 data, it delivers efficacy numbers comparable to injectable semaglutide at 2.4 mg/week (~15% weight loss at 68 weeks), in an oral, once-daily format.

The competitive significance: unlike peptide-based drugs (semaglutide, tirzepatide), aleniglipron is a small molecule — meaning it's simpler and cheaper to manufacture. Small-molecule GLP-1 agonists, if they replicate injectable-level efficacy with manageable tolerability, could eventually drive manufacturing cost structures down in ways that peptide synthesis cannot easily match.

For context on what the oral GLP-1 landscape means for patients currently on injectables, the orforglipron/Foundayo transition data is worth reading alongside this.

What to watch

The End-of-Phase 2 FDA meeting in Q2 2026 will determine whether the FDA agrees with Structure Therapeutics' proposed Phase 3 design. Key questions the meeting will address: minimum effective dose for Phase 3, whether a cardiovascular outcomes trial will be required before or after approval, and whether the 2.5 mg lower start dose — with its better tolerability profile — will be the recommended starting approach in Phase 3.

The lower-dose start data suggests Structure Therapeutics is actively working on the tolerability problem that has held back other small-molecule GLP-1 programs. If the 2.5 mg cohort's tolerability advantage holds in Phase 3, it could make aleniglipron meaningfully more patient-friendly than earlier oral GLP-1 candidates at equivalent efficacy doses.

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