Retatrutide phase 3 papers
Weekly Research Update · October 5, 2026
INDUSTRY UPDATE
This week's update covers September 28 through October 5. The first full phase 3 papers on retatrutide reached the journals, and Lilly reported a phase 2b combination of eloralintide plus tirzepatide. FDA drug news for September 28-October 4 listed no peptide, 503A, 503B, or shortage action.
Must-know
1) Phase 3 retatrutide papers (Sep 29). The New England Journal of Medicine published TRIUMPH-1 (DOI 10.1056/NEJMoa2604169). TRIUMPH-2 appeared the same day in The Lancet, alongside the European Association for the Study of Diabetes 2026 meeting. TRIUMPH-1 randomized 2,339 adults with obesity and without diabetes for 80 weeks. On the treatment-regimen estimand, mean weight change was -17.6% at 4 mg, -23.7% at 9 mg, and -25.0% at 12 mg, compared with -3.9% on placebo. Gastrointestinal events were the most common adverse events. TRIUMPH-2 enrolled adults with obesity and type 2 diabetes. Lilly's figure for the 12 mg arm was about 20% weight loss, and up to 49.6 lb in the company statement. Lilly said it plans an application in the first quarter of 2027.
These are journal papers on an unapproved triple agonist. They are not a compounding authorization. FDA's public position remains that retatrutide and cagrilintide cannot be used in compounding. A research-use-only label has not insulated sellers when a site adds dosing, reconstitution, or human-use content. The results do not make a research peptide a lawful drug, and they do not describe the contents of any vial other than Lilly's.
ALSO ON THE RADAR
Eloralintide plus tirzepatide
On September 30, Reuters and a Lilly investor release reported a phase 2b study of eloralintide plus tirzepatide (EloraTZP), presented at the European Association for the Study of Diabetes meeting. The trial enrolled 367 adults with obesity or overweight and type 2 diabetes in the United States and Argentina. The highest tested combination dose produced 23.3% mean weight loss at 48 weeks, compared with 14.8% on tirzepatide alone and 11.1% on the highest eloralintide dose alone. Discontinuation drew more notice than the point estimate. Late-stage EloraTZP trials are planned for the fourth quarter of 2026. Eloralintide is an investigational amylin-pathway peptide. It sits beside the cagrilintide discussion, and it is not an approved substance for compounding.
Classification commentary
On October 2, BioPharm International ran a commentary on whether amino-acid count would classify retatrutide as a biologic. Counsel restated that the Seventh Circuit argument on September 24, which falls outside this window, turns on the protein line and on exclusivity: 12 years or 5. No decision had issued as of October 3. Neither outcome approves retatrutide or places it on a bulks list, so compounding stays unlawful either way.
Set aside this week: recycled July 2026 Pharmacy Compounding Advisory Committee explainers on BPC-157, TB-500, KPV, MOTS-c, epitalon, and semax, still circulating with fresh crawl dates; the April 30 proposal to keep semaglutide, tirzepatide, and liraglutide off the 503B bulks list; BioPharma Dive's account of six Lilly lawsuits, filed August 12; and a September 29 McDermott recap of the August 24 research-seller warning letters and the older Paradigm Peptides sentencing. Those items sit outside this seven-day window or repeat earlier reporting.
Window: Sep 28-Oct 5, 2026. Also checked: FDA drug news and the warning-letter index, the Federal Register and the 503B docket, The Lancet and EASD reporting, BioPharma Dive, STAT, Fierce Pharma, and ClinicalTrials.gov. No new peptide rule appeared, and no newly posted U.S. trial for the catalog peptides cleared a primary-source date check inside these seven days.
RECENT RESEARCH & SCIENCE LINKS
TRIUMPH-1, New England Journal of Medicine (Sep 29, 2026)
https://www.nejm.org/doi/full/10.1056/NEJMoa2604169
Eloralintide plus tirzepatide, Reuters (Sep 30, 2026)
Amino-acid count and retatrutide classification, BioPharm International (Oct 2, 2026)
https://www.biopharminternational.com/view/amino-acid-count-retatrutide-biologic-drug-classification
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