PEP-RTA-3 vs PEP-TZP-2: which fits the research question?
PEP-TZP-2 activates two receptors, GIP and GLP-1. PEP-RTA-3 activates those two plus the glucagon receptor. Choose PEP-TZP-2 for questions about dual incretin signalling, insulin secretion and appetite; choose PEP-RTA-3 when the question involves energy expenditure, hepatic fat or the glucagon pathway. Both are lyophilized, lot-tested and sold for laboratory research only.
| PEP-RTA-3 | PEP-TZP-2 | |
|---|---|---|
| Receptors | GIP, GLP-1, glucagon | GIP, GLP-1 |
| Length | 39 amino acids | 39 amino acids |
| Backbone | Glucagon-derived | GIP-derived |
| Side chain | C20 fatty diacid | C20 fatty diacid |
| Distinguishing pathway | Glucagon receptor: energy expenditure, hepatic lipid | GIP receptor bias: insulin potentiation, adipose |
| Typical research use | Triple-agonist comparisons, expenditure models | Dual-incretin reference compound |
| Key clinical context | Phase 2, NEJM 2023 | SURMOUNT-1, NEJM 2022 |
| Current lot purity | 99.83% (RETA10-0803) | 99.80% (TIR10-0803) |
| Vial | 10 mg, $105 | 10 mg, $120 |
What does the glucagon receptor add?
Glucagon receptor activation raises energy expenditure and hepatic fat oxidation, effects the incretin receptors do not produce on their own. On its own it also raises blood glucose, which is why a triple agonist has to balance the glucagon component against the incretin components. Studies that measure expenditure by indirect calorimetry, or hepatic lipid content, are the ones where PEP-RTA-3's extra receptor matters.
When is PEP-TZP-2 the better choice?
When the question is about the incretin pathways themselves. PEP-TZP-2's GIP receptor bias is a research topic in its own right, and its larger published dataset makes it the cleaner comparator for GLP-1-only compounds like PEP-SMG-1. Adding a glucagon arm would confound an incretin question.
Can they be run side by side?
Yes, and that is the most common design. The Metabolic trio bundle ships PEP-RTA-3, PEP-TZP-2 and PEP-SMG-1 as three lot-matched vials with three certificates, so a three-arm comparison starts from verified material.
What do the current certificates show?
Pharmacology decides which compound answers the question; the certificate decides what is actually in the vial. These are the current lots for each, read from the certificate library:
| Compound | Lot | Identity | Purity | Content | Issued |
|---|---|---|---|---|---|
| PEP-RTA-3 | RETA10-0803 | LC-MS/MS | 99.83% | 10.61 mg vs 10 mg label | Aug 17, 2026 |
| PEP-TZP-2 | TIR10-0803 | LC-MS/MS | 99.80% | 10.18 mg vs 10 mg label | Aug 17, 2026 |
Purity on both lines is area percent by RP-HPLC at 214 nm, which the area-percent post explains is a ratio of peak areas and not a weight, so the two figures are comparable only because the method is the same. Content is the measured mass against the label, and the lot-to-lot post is the case for using it rather than the label in any calculation. All 114 certificates read together are in the certificate dataset.
Common questions
Is PEP-RTA-3 just PEP-TZP-2 with an extra receptor?
Functionally that is the difference in receptor coverage, but they are distinct 39-residue sequences with different backbones — PEP-RTA-3 is glucagon-derived, PEP-TZP-2 GIP-derived. They are not the same molecule with an addition.
Which one should a metabolic study use?
It depends on what the design needs to attribute. PEP-TZP-2 isolates incretin signalling; PEP-RTA-3 adds glucagon receptor activity, so an effect seen only with PEP-RTA-3 points at that third pathway.
Where to go next
For laboratory research use only. Clinical trial results are cited as context and do not describe use of the material sold here.