Retatrutide

Graded B: large phase 2 and phase 3 randomized trials, but it is not yet approved or under FDA review.

Strengths: 10, 20, 30, 48, 60 mg
Also known as: LY3437943, GGG tri-agonist (GIP/GLP-1/glucagon)
Molecule: 39-amino-acid lipidated peptide (triple agonist)
Formula: C256H392N64O79
Mol. weight: 4731.2 g/mol
CAS: 2381089-83-2

Origin

An investigational molecule from Eli Lilly, first described in 2022. Aib and α-methyl-leucine residues resist enzyme breakdown, and a C20 fatty diacid binds albumin for a roughly 6-day half-life.

How it works

Activates three receptors at once: GIP, GLP-1 and glucagon. GLP-1 and GIP activity reduce appetite and slow stomach emptying; in animal studies the added glucagon activity raised energy expenditure and is thought to drive large liver-fat reductions.

What the research shows

Phase 2 trials in obesity and type 2 diabetes reported average weight reductions of up to 24% over 48 weeks. The 2025–2026 phase 3 TRIUMPH and TRANSCEND programs studied obesity, type 2 diabetes, knee osteoarthritis pain, sleep apnea and established cardiovascular disease, reporting up to about 28% weight reduction at the top dose at 80 weeks in TRIUMPH-1 (about 30% at 104 weeks in an extension). Cardiovascular outcomes, lean-mass effects and what happens after stopping are still unknown.

Key studies

Jastreboff et al., NEJM 2023 (phase 2) 338 adults; weight change up to −24.2% vs −2.1% on placebo at 48 weeks.
Coskun et al., Cell Metabolism 2022 Discovery paper: glucagon-driven energy expenditure added to weight loss in obese mice.
TRIUMPH-1, 2026 (phase 3) 2,339 adults; weight change up to −28.3% at 80 weeks.
TRIUMPH-4, 2025 (phase 3) Knee osteoarthritis with obesity; WOMAC pain improved 62–67% vs 35%.

Safety findings

Trials reported dose-related nausea, vomiting, diarrhea and constipation. A burning or altered skin sensation (dysesthesia) occurred in 5–21% at higher doses, and heart rate rose with dose. There is no approved label yet, so no formal boxed warnings.

Regulatory status

Not approved anywhere; after positive phase 3 results, Lilly plans to submit its FDA application in the first quarter of 2027. Not lawfully compoundable; FDA has issued warning letters to "research use" sellers marketing it for people, and Lilly sued six sellers in August 2026. Not on WADA's 2026 prohibited list.

Catalog notes

Available in 10, 20, 30, 48 and 60 mg, all with current-lot certificates (99.79–99.9% purity). It is the catalog's top seller.

In kits: Ascend Bundle