Monthly recap
May 2026: GLP-1 research cadence settles, retatrutide approaches first Phase 3 readout
Monthly UK metabolic-peptide brief — April → May 2026. TRIUMPH-1 readout window narrows; SURMOUNT-MMO interim disclosed; tirzepatide MHRA labelling steady.
The state of the field this month
April quietly closed a stretch of nine months in which no first-time positive Phase 3 readout for a metabolic peptide has been reported. That changes in the next quarter. TRIUMPH-1 — Eli Lilly's first Phase 3 trial of retatrutide in obesity — sits inside its expected H1 2026 readout window, and Eli Lilly's Q1 earnings call (29 April) kept the guidance unchanged. The TRIUMPH-1 read is the most-watched single data event in the class this year.
SURMOUNT-MMO interim slide-pack
The Q1 update to investors included a single slide on SURMOUNT-MMO, the cardiovascular-outcomes trial for tirzepatide in non-diabetic obesity. Event-rate tracking remains on the originally-projected schedule; final readout is now guided to late 2026 or early 2027. The interim hazard ratio was not disclosed but the tone — "consistent with our pre-specified expectations" — read as directional confirmation of the SELECT signal.
MHRA stays quiet on tirzepatide labelling
No new MHRA bulletins this month on the tirzepatide weight-management indication. The steady-state position is that Mounjaro is licensed for both T2DM and chronic weight management; private supply remains the primary access route in the UK as NHS weight-management services continue to operate within capped referral pathways. The MHRA's most recent Drug Safety Update touching the class was the gastrointestinal-tolerability reminder issued late 2025 — no change to the labelling.
What this means for UK researchers
Three things to do in the next six weeks. First, lock in any retatrutide-related literature reviews now — the post-TRIUMPH-1 publication wave will overwhelm sub-classification work within a quarter of readout. Second, if your research design uses tirzepatide as a comparator, check whether your dose schedule matches the SURMOUNT-MMO arm; the trial sets the methodological template for the next round of investigator-initiated work. Third, the trial readout watchlist is now the single best place to track what's coming.
New on the site this month
- A dynamic comparison matrix at /compare covering all 8 peptides on the site, sortable by half-life, weight reduction, UK status.
- Eight new condition-specific summaries — type-2 diabetes, obesity, NASH, OSA, CKD, heart failure, visceral adiposity, insulin resistance.
- Six brand-name landings — Mounjaro, Wegovy, Zepbound, Ozempic, Saxenda, Rybelsus.
- A 62-term glossary across six categories — hormones, pharmacology, anatomy, trials methodology, regulatory, chemistry.
- A site-wide searchable FAQ hub aggregating every peptide FAQ plus cross-cutting questions.
Next month: TRIUMPH-1 readout (if it lands inside the projected window), recapitulation of the Phase 3 retatrutide programme, and the first MHRA position update we expect post-readout.