GLP-1 / GIP / glucagon triple agonist
Investigational once-weekly injectable for obesity/metabolic disease (Eli Lilly, LY3437943).
| Class / type | GLP-1 / GIP / glucagon triple agonist |
|---|---|
| Category | Metabolic & Weight |
| Status (Jul 2026) | Investigational |
Retatrutide (Lilly code LY3437943) is an experimental once-weekly injectable that hits three metabolic receptors at once. It has generated intense interest because its trial weight-loss numbers are the highest reported for this drug class to date.
Crucially, it is not approved. It is still in Phase 3 testing, so its long-term safety is not established and any 'retatrutide' sold online is unapproved, unregulated material.
Retatrutide agonizes the GLP-1 and GIP receptors (like tirzepatide) and adds glucagon-receptor activity. The glucagon arm is thought to raise energy expenditure and fat oxidation, potentially adding a fat-burning effect on top of the appetite suppression that GLP-1/GIP drugs provide.
Phase 3 results (the TRIUMPH program) have now landed and are the strongest in this drug class: TRIUMPH-1 confirmed about 28.3% average weight loss at 80 weeks (reported May 2026), and TRIUMPH-4 reported about 28.7% at 68 weeks. A diabetes-specific trial (TRANSCEND-T2D-1) reported roughly a 2.0% A1c reduction with 16.8% weight loss.
A few remaining TRIUMPH trials are still reporting through 2026. Eli Lilly's FDA submission (NDA) is expected around Q4 2026-Q1 2027, so these figures are now Phase 3-confirmed but the drug is not yet approved.
The largest average weight loss reported for this class so far, with strong metabolic and (in studies) liver-fat improvements.
The added glucagon mechanism may help people who plateau on GLP-1/GIP drugs, though this is still being studied.
GI effects (nausea, constipation) during dose escalation are common, as with other incretin drugs.
Trials have reported dose-dependent increases in resting heart rate, plus fatigue and, in some participants, a tingling or sunburn-like skin sensation. Long-term safety is unknown, it is not approved, and gray-market material carries purity and dosing risks.
There is no approved retatrutide product and no sanctioned human dosing. With NDA submission expected around Q4 2026-Q1 2027, realistic FDA approval and launch fall in the late-2027 to mid-2028 window, pending the full trial package.
In August 2026 Eli Lilly opened a limited early-access program for a defined group of patients ahead of approval. It remains investigational, and standard prescribing is not available.
Dramatic appetite reduction and unusually large fat loss; some report more energy.
NOT FDA-approved. All four Phase 3 TRIUMPH trials are now complete; the NDA is expected around Q4 2026-Q1 2027, with possible approval late 2027-2028. In Aug 2026 Eli Lilly opened a limited early-access program for a defined patient group ahead of approval. Anything otherwise sold now is gray-market / research-use-only.
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