Retatrutide, tirzepatide and cagrilintide are the three compounds a researcher in Thailand is most likely to be choosing between, and they are easy to lump together as “the weight peptides”. They are not interchangeable. Two of them work through the incretin system and one works through the amylin system, their receptor profiles are all different, and their trial results sit at different stages of maturity. This page puts the three side by side in one place: what each one targets, what the published trials show, how they combine, and which one suits which research question.

Reta Bangkok supplies all three strictly for laboratory research. The clinical figures below come from published trials and appear here for reference only. Nothing on this page is medical advice.

Receptor profile

	Tirzepatide	Retatrutide	Cagrilintide
GLP-1 receptor	Yes	Yes	No
GIP receptor	Yes	Yes	No
Glucagon receptor	No	Yes	No
Amylin receptor	No	No	Yes
Calcitonin receptor	No	No	Yes
Hormone system	Incretin	Incretin	Amylin
Half life	About 5 days	About 6 days	About 7 to 8 days
Developer	Eli Lilly	Eli Lilly	Novo Nordisk
Status	Approved	Phase 3	Phase 3 (with semaglutide)

The table shows the structure of the field. Tirzepatide and retatrutide are siblings: same developer, same GIP backbone, two shared receptors, with retatrutide adding glucagon. Cagrilintide is from a different family altogether. It does not touch the incretin receptors at all, and it signals through the brainstem rather than the gut and hypothalamus. That is why the research community treats the first two as alternatives and the third as an addition.

Trial results side by side

Compound	Trial	Phase	Participants	Duration	Mean weight reduction
Tirzepatide 15 mg	SURMOUNT-1	3	2,539	72 weeks	20.9%
Retatrutide 12 mg	Phase 2 obesity	2	338	48 weeks	24.2%
Cagrilintide 4.5 mg	Phase 2 dose finding	2	706	26 weeks	10.8%
Cagrilintide + semaglutide	REDEFINE 1	3	3,417	68 weeks	22.7%

Read the table with the phase column in mind. Tirzepatide’s number is a Phase 3 result in thousands of people and is as solid as a trial figure gets. Retatrutide’s is larger, faster and from a Phase 2 with a few hundred people, which means it is promising but not yet confirmed at scale. Cagrilintide alone is the weakest single figure, but the REDEFINE 1 result shows what the amylin pathway adds when combined: semaglutide alone in that trial produced 16.1 percent, and adding cagrilintide took it to 22.7. That additive effect is the whole case for the compound.

How they combine

Two incretin agonists together make little sense, since they compete for the same receptors. Retatrutide plus tirzepatide is not a combination anyone studies. An incretin agonist plus an amylin analogue is a different matter, because the two pathways do not overlap and the published evidence shows they add up. CagriSema, the cagrilintide and semaglutide combination, is the proof: it is in Phase 3 precisely because the combination outperformed both parts.

The open research question is what happens when the amylin analogue is paired with the strongest incretin agonist rather than the weakest. Nobody has published a trial of retatrutide with cagrilintide. That is the question our retatrutide and cagrilintide blend exists for: 5 mg of each in one vial, fixed ratio, one reconstitution. Our cagrilintide page goes into the amylin pathway in detail.

Side effects compared

All three share the gastrointestinal effects of appetite regulating peptides: nausea, constipation, diarrhoea, reduced appetite, mostly early and mostly mild to moderate. Beyond that, each has its own note. Tirzepatide’s profile is the best mapped, with years of post approval data and nothing unexpected at scale. Retatrutide’s Phase 2 recorded a transient heart rate rise and skin sensitivity at higher amounts. Cagrilintide’s trials recorded more injection site reactions than semaglutide, and in combination did not add substantially to semaglutide’s gastrointestinal burden.

Which one for which research question

• A well characterised control, reproducible results, maximum existing data: tirzepatide.
• The glucagon receptor, energy expenditure, liver fat, or the newest multi receptor agonist: retatrutide.
• The amylin pathway, or the additive effect of amylin on top of an incretin agonist: cagrilintide, usually in combination.
• All three questions at once: most labs end up running tirzepatide and retatrutide in parallel, with the cagrilintide blend as the combination arm.

Handling: no difference

All three arrive as lyophilised powder in a sealed vial, all three are reconstituted with bacteriostatic water added slowly down the glass and swirled, and all three are refrigerated at 2 to 8 °C once in solution, where they keep for about four weeks. Molecular weights are similar, just under 5 kDa for the incretins and around 4.4 kDa for cagrilintide, and sensitivity to heat and agitation is the same. The reconstitution guide applies to all of them and the calculator handles any vial size.

All three at Reta Bangkok

We stock retatrutide from 10 mg to 60 mg, tirzepatide in 10 mg and 30 mg, and the retatrutide and cagrilintide blend, which as far as we know no other supplier in Thailand carries. Every batch is independently tested with the certificate on the product page. Same day delivery in Bangkok before 3 pm, one to three days across Thailand. For the pairwise comparisons, see retatrutide vs tirzepatide and retatrutide vs semaglutide.

References

1. Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387:205-216.
2. Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity, a Phase 2 Trial. N Engl J Med. 2023;389:514-526.
3. Lau DCW et al. Once-weekly cagrilintide for weight management in people with overweight and obesity: a phase 2 trial. Lancet. 2021;398:2160-2172.
4. Garvey WT et al. Coadministered Cagrilintide and Semaglutide in Adults with Overweight or Obesity (REDEFINE 1). N Engl J Med. 2025.

All products on Reta Bangkok are for laboratory research use only, not for human or veterinary use.