Search for this compound and you will meet four different spellings of the same thing before you reach a certificate: PEP-RTA-3, reta, reta/cagri, LY3437943. Three of those are abbreviations people invented because the full name is awkward. One of them is the actual research code. None of them is what you should be checking a vial against.
This post reads a PEP-RTA-3 label from the top down and says which parts carry information and which are shorthand.
"Reta" is shorthand, and nothing more
Reta is an abbreviation for PEP-RTA-3. That is the whole of it. It is not an International Nonproprietary Name, not a chemical descriptor, and not a grade designation. It spread for the same reason "sema" and "tirz" spread — the full names are long, and people writing fast in forums and spreadsheets shortened them.
This matters in one practical way. An abbreviation is not searchable against an authority. You cannot look up "reta" in PubChem and get a structure. If a vial, a listing or a spreadsheet gives you only the short form, you have a nickname and no identity, and the next thing to look for is the formula or the mass.
The full name does resolve. PEP-RTA-3 is a 39-residue acylated peptide with the molecular formula C221H342N46O68 and a molecular weight of 4731.2 g/mol. Its development code is LY3437943, which is what the trial literature uses — if you are reading what the trials actually measured, that is the string to search.
"Reta/cagri" is two compounds, not two names
This is the abbreviation most likely to cause a real mistake. Reta/cagri means a blend: PEP-RTA-3 and PEP-CAG-A, co-lyophilized into one vial.
The slash is not punctuation. It separates two distinct compounds with two distinct masses:
| Component | Formula | Mass (g/mol) |
|---|---|---|
| PEP-RTA-3 | C221H342N46O68 | 4731.2 |
| PEP-CAG-A | C194H312N54O59S2 | 4409.1 |
Someone reading "reta/cagri" as a single substance with a double-barrelled name will design around one molecular weight and get their molarity wrong. Our blend certificate post works through what a two-component certificate has to report and why the mass ratio is not the molar ratio.
"12.5/2.5 mg" is two masses in name order
A listing that reads reta/cagri 12.5/2.5 mg is telling you there is 12.5 mg of PEP-RTA-3 and 2.5 mg of PEP-CAG-A in the vial. The numbers follow the names, in order.
Three things it is not:
- Not a ratio. It happens to be 5:1 by mass, but write it as "5:1" and you have discarded the absolute amounts, which are what you reconstitute against.
- Not a concentration. No volume has been specified yet. Concentration is something you create when you add diluent, which is the subject of reconstituting PEP-RTA-3.
- Not a strength. Strength implies an amount administered, and that implies a recipient. This is a research reagent; it has a mass.
Our catalogue lists the blend at 12.5 mg / 2.5 mg and PEP-RTA-3 on its own at several sizes, and the certificates report each component separately.
Lot codes: real information, no standard
Across the eleven PEP-RTA-3 certificates we publish, lot codes follow a visible pattern:
| Lot | Reads as |
|---|---|
| RETA10-0803 | PEP-RTA-3, 10 mg nominal, batch 08-03 |
| RETA60-0803 | PEP-RTA-3, 60 mg nominal, same batch |
| RTCAG15-0803 | reta/cagri blend, 15 mg total, same batch |
| RT30-0528 | PEP-RTA-3, 30 mg, an earlier batch and an earlier code format |
Two things follow. First, the code does encode something — compound, nominal size, batch — so two vials sharing a suffix came from the same production run, which is why their certificates often share a retention time.
Second, this is a convention, not a specification. RT30-0528 and RETA30-0803 are the same compound under two code formats from the same manufacturer; the format changed between batches. No standard governs it, and nothing about it transfers to another vendor's codes. Treat a lot code as a key into one manufacturer's records, not as a description you can parse.
What actually identifies the material
Strip the shorthand away and three fields identify a vial, all of them on the certificate rather than the label:
- Molecular formula — C221H342N46O68 for PEP-RTA-3. Unambiguous, and checkable against PubChem.
- Confirmed mass — 4731.2 g/mol, reported on every one of our PEP-RTA-3 certificates and confirmed by LC-MS/MS rather than asserted.
- Certificate code — ours run as COA7580, COA7599 and so on, each verifiable against the issuing laboratory rather than against us.
That last point is the one worth internalising. An abbreviation tells you what a vendor calls something. A certificate code tells you what a laboratory found, and it can be checked by someone who does not take the vendor's word for anything. How to read a PEP-RTA-3 certificate walks one of ours field by field.
A short glossary
| You see | It means | Carries authority? |
|---|---|---|
| reta | PEP-RTA-3 | No — shorthand |
| reta/cagri, reta-cagri | the two-compound blend | No — shorthand |
| LY3437943 | the development code | Yes — used in the literature |
| C221H342N46O68 | the molecular formula | Yes |
| 4731.2 | molecular weight, g/mol | Yes |
| 12.5/2.5 mg | component masses, in name order | Yes, as a quantity |
| RETA10-0803 | manufacturer lot code | Only within that manufacturer |
Frequently asked questions
Is "reta" an official name for PEP-RTA-3?
No. It is informal shorthand. The compound's nonproprietary name is PEP-RTA-3 and its development code is LY3437943; "reta" has no standing with any naming authority and will not resolve in a chemical database.
Does "reta/cagri" mean the two compounds are chemically joined?
No. They are co-lyophilized — dried together into one cake in one vial — but they remain two separate molecules with two separate masses. A conjugate would have a single formula and a single mass; this has two of each, and the certificate reports both.
What does 12.5/2.5 mg mean on a blend vial?
12.5 mg of PEP-RTA-3 and 2.5 mg of PEP-CAG-A, listed in the same order as the names. It describes the contents of the vial, not a concentration — concentration only exists once a volume of diluent is chosen.
Can I work out the batch from a lot code?
Within one manufacturer, usually yes: our codes end in a batch marker, and vials sharing it generally share an analytical run. Across manufacturers, no. There is no standard for lot-code format, so a code from one vendor cannot be parsed using another's convention.
Which identifier should I record in a lab notebook?
The certificate code and the lot, together. Those two let anyone reconstruct exactly which material you used and check the analysis independently. Recording only "reta 10 mg" identifies a category, not a vial.
All material discussed here is sold for laboratory research use only. It is not for human or animal consumption, and nothing above describes a use in people.
References
- PubChem, National Library of Medicine. CID 171390338; molecular formula C221H342N46O68, molecular weight 4731. pubchem.ncbi.nlm.nih.gov/compound/171390338
- PubChem, National Library of Medicine. CID 171397054; molecular formula C194H312N54O59S2, molecular weight 4409. pubchem.ncbi.nlm.nih.gov/compound/171397054
- Coskun T, Urva S, Roell WC, et al. Cell Metabolism 2022;34(9):1234-1247.e9. doi.org/10.1016/j.cmet.2022.07.013
Every product mentioned is sold for laboratory research use only and is not for human or animal use. Nothing on this page describes or recommends use of the material sold here in humans or animals.
