Two Receptor Strategies

Tirzepatide simultaneously activates two receptors – GLP-1 and GIP – and is therefore considered a “dual agonist”.

Retatrutide goes a step further, additionally activating the glucagon receptor. Studies associate this third pathway with increased hepatic fat oxidation – an effect that pure GLP-1/GIP combinations do not show.

Approval Status Compared

Tirzepatide is FDA approved under the brand names Mounjaro (type 2 diabetes) and Zepbound (weight management, obstructive sleep apnea).

Retatrutide, by contrast, is still in clinical testing. The Phase 3 TRIUMPH program is underway; an FDA submission is expected in late 2026/early 2027. Until any approval, retatrutide remains a research compound only.

What the Evidence Shows

Published Phase 2 data on retatrutide (Jastreboff et al., NEJM 2023) showed weight reduction over 24 weeks that exceeded previously published results for semaglutide and tirzepatide. However, differing study populations and designs do not allow for a direct comparison.

For tirzepatide, the SURMOUNT trial program provides a considerably broader and longer-running evidence base, as the compound has already been in clinical use for several years.

No Direct Head-to-Head Comparison

Since no study directly testing retatrutide against tirzepatide has been published to date, all comparisons rely on different study populations and should be interpreted with corresponding caution.

Sources

  • Jastreboff AM, et al. NEJM. 2023;389(6):514–526.
  • Rosenstock J, et al. The Lancet. 2023;402(10401):529–544. PMID 37385280
  • Jastreboff AM, et al. NEJM. 2022;387(3):205–216.
  • Aronne LJ, et al. NEJM. 2025;393(1):26–36. PMID 40353578

References without a PMID can be located via the respective publisher.