Skip to content
Comparisons·Published 2026-08-11

Semaglutide vs Tirzepatide vs Retatrutide: the incretin agonists

The progression from mono to triple agonist — semaglutide, tirzepatide, and retatrutide — what the literature shows, and how to evaluate each compound's COA.

By MX-1 Labs Editorial Team

On this page

Research use only. This content is for laboratory research; not for human or veterinary use, diagnosis, or treatment.

Producto para uso experimental en laboratorio. No es medicamento ni producto de consumo humano.

Semaglutide, tirzepatide, and retatrutide represent three generations of the same approach: activating incretin receptors. The difference between them is how many receptors they activate — one, two, or three. This comparison orders the three molecules by their documented mechanism and — most relevant to a lab — explains how to evaluate and contrast the quality of each one when sourcing it for research.

The three molecules, in one line

  • Semaglutide: single-receptor agonist (GLP-1). The compound behind Ozempic® and Wegovy®; broad clinical literature [3].
  • Tirzepatide (LY3298176): dual agonist (GIP + GLP-1). SURPASS / SURMOUNT programs [2].
  • Retatrutide (LY3437943): triple agonist (GIP + GLP-1 + glucagon). More recent published evidence [4].

The shared axis and what each one adds

All three share the GLP-1 receptor, associated with satiety and glucose-dependent insulin secretion. Tirzepatide adds the GIP receptor, linked to insulin sensitivity and lipid metabolism. Retatrutide further adds the glucagon receptor, which the literature associates with energy expenditure and hepatic lipid metabolism. It is a progression from one to three receptors.

What the published evidence shows

Each molecule has its heaviest reference. For semaglutide, STEP-1 in the New England Journal of Medicine [3]; for tirzepatide, SURMOUNT-1 [2]; for retatrutide, its phase 2 trial, also in NEJM [4]. There is also a direct comparison between tirzepatide and semaglutide, SURPASS-2 [1]. All are human studies cited as scientific context for the compounds; they are not a usage guide or an administration recommendation.

How to compare quality when sourcing any of the three

For a lab, the decision is settled by documentation, not marketing. The criteria are identical for all three molecules:

  1. Lot-specific certificate of analysis (COA) with HPLC (reverse-phase) purity and mass-spectrometry (MS) identity confirmation.
  2. Traceability: a lot number and analysis date that map to the vial you received.
  3. Endotoxin (LAL) testing where the in-vitro protocol requires it.
  4. Documented storage conditions and stability data for the lyophilized material.

How to choose for your protocol

The choice depends on the research axis. Semaglutide is the single-receptor reference with the most consolidated clinical literature; tirzepatide adds the GIP axis with a published head-to-head [1]; retatrutide incorporates the glucagon axis and is the most recent triple design. In all three cases, prioritize the lot with a verifiable COA and documented purity above any other consideration.

References

  1. [[1]] Frías JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). N Engl J Med. 2021;385(6):503–515. NEJM 2021 · doi:10.1056/NEJMoa2107519
  2. [[2]] Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205–216. NEJM 2022 · doi:10.1056/NEJMoa2206038
  3. [[3]] Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP-1). N Engl J Med. 2021;384(11):989–1002. NEJM 2021 · doi:10.1056/NEJMoa2032183
  4. [[4]] Jastreboff AM, Kaplan LM, Frías JP, et al. Triple–hormone-receptor agonist retatrutide for obesity — a phase 2 trial. N Engl J Med. 2023;389(6):514–526. NEJM 2023 · doi:10.1056/NEJMoa2301972

Related reading