LY3437943 is the most structurally ambitious of the incretin-class compounds in this catalogue, engaging three receptors where its class-mates engage one or two. For a buyer that changes almost nothing about the purchasing process and quite a lot about why the certificate's identity line matters.
This guide covers what the documentation should establish, how to choose between the five strengths, and the handling consequences of the modification that all three of these compounds share.
The three compounds meant are NN9535, LY3298176 and LY3437943, and the modification they share is a fatty diacid attached to a lysine side chain, which the section on dissolution below returns to.
The identifiers on the catalogue record
Every document about this compound should reconcile to the same handful of identifiers, and the catalogue record for RS-RTA-3 lists them: the development code LY3437943, under which the compound was described in the literature; CAS registry number 2381089-83-2; molecular formula C256H392N64O79; molecular weight 4731.2 g/mol as an average mass; and a 39-residue backbone carrying Aib residues, an alpha-methyl-leucine, a lysine bearing an (AEEA)-gamma-Glu-C20 diacid side chain, and a C-terminal serinamide. The class description on the record is GIP/GLP-1/glucagon triple receptor agonist.
| Identifier | Value on the record | Where it should appear |
|---|---|---|
| Development code | LY3437943 | Certificate header, quote, literature |
| CAS number | 2381089-83-2 | Certificate, safety data sheet, quote |
| Molecular formula | C256H392N64O79 | Certificate identity section |
| Molecular weight | 4731.2 g/mol (average) | Certificate identity section, mass spectrometry result |
| Residues | 39 | Sequence line, where the certificate prints one |
| Catalogue code | RS-RTA-3 | Vial label, order, certificate product line |
What to match, and on which document.
A certificate or quote that carries a different CAS number, a formula that does not match, or a mass that reconciles to neither the average nor the monoisotopic value for this formula is describing a different molecule, whatever name is printed at the top. The sections below say how to read each of those lines.
Why the third receptor is a structural claim
Engaging an additional receptor is not an incremental refinement of a two-receptor molecule. It is a different sequence with different substitutions, and the compound is not a later version of the others despite being discussed as though it were.
The three receptors are the glucagon receptor, the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor. The 2022 paper that describes the compound under the designation LY3437943, which the catalogue record lists as a synonym, calls it a triple agonist peptide at those three (Coskun and colleagues). Set against the catalogue descriptions of the two class-mates, the glucagon receptor is the one neither of them is described as engaging, which makes it the third.
| Compound | Described as | Residues | Fatty diacid |
|---|---|---|---|
| RS-SEM-1 | GLP-1 receptor agonist | 31 | C18 |
| RS-TRZ-2 | GIP/GLP-1 dual agonist | 39 | C20 |
| RS-RTA-3 | GIP/GLP-1/glucagon triple agonist | 39 | C20 |
Descriptions as the catalogue records give them.
LY3298176 and LY3437943 share a residue count and a diacid length in those records, so neither figure tells the two apart on a document; the next section gives the identifier that does.
The practical consequence is that published work on one of these compounds does not transfer to another, and neither does a certificate. NN9535, LY3298176 and LY3437943 compared sets out what separates them structurally.
What the certificate has to establish
For a long modified peptide, identity carries more weight than it does for a short sequence, because there are more ways for a synthesis to go slightly wrong and still produce something of approximately the right mass.
A method that fragments the molecule and reads a sequence ladder establishes considerably more than one that weighs the intact molecule. Both appear on certificates in this category and they are not equivalent, which is covered in mass spectrometry and peptide identity.
| Read | What it settles | If it is wrong |
|---|---|---|
| Lot number | Whether this document describes your vial | Nothing else on the page applies |
| Both dates | That testing took time | A single date removes the check |
| Identity and method | What the compound is | Purity describes an unknown substance |
| Content | How much peptide is in the vial | Your calculations inherit the error |
| Purity and method | What share of peptide material is the target | A bare percentage means little |
Read in this order. The first two take seconds and decide whether the rest of the document applies to you.
For LY3437943 specifically, the identifier to match is CAS 2381089-83-2, the number in the catalogue record. A quote or certificate that carries it is about this compound and not about LY3298176 or NN9535, whose records carry different numbers (2023788-19-2 and 910463-68-2); whether the document describes your vial is still settled by the lot number.
Choosing between five strengths
The same logic as any multi-strength compound, with one addition specific to this class. Larger vials are cheaper per milligram and only cheaper in practice if used before they degrade, so size against consumption rather than against unit price.
The addition is that this compound dissolves slowly, so a larger vial takes proportionally more patience at reconstitution and is more likely to be rushed. That is a small argument toward the strength that matches a single piece of work.
Why this class is slow to dissolve
All three of these compounds carry a fatty-acid chain attached to the backbone, included to bind albumin and extend circulation. That modification pulls the whole molecule toward the hydrophobic side despite a residue composition that would otherwise favour water.
On LY3437943 the chain is a C20 diacid: the catalogue record describes a lysine-conjugated (AEEA)-γGlu-C20 diacid, that is a twenty-carbon fatty diacid joined to a lysine side chain through a short linker. The records give LY3298176 a C20 diacid as well and NN9535 a C18 diacid.
Slow is therefore the expected behaviour rather than a fault. Agitation creates an air-water interface at which peptides can unfold, which is why foaming is read as a sign of stress on the material. Why some peptides resist dissolving covers why composition alone does not predict this.
Content, and the number that belongs in a calculation
The certificate's measured content, not the label. Fills are set to meet or exceed the nominal strength, so the measured figure is usually a few percent higher, and using the label builds that difference into everything downstream.
The powder in the vial weighs more than either figure, because a lyophilised peptide is a salt, and the counter-ion is part of the solid. There is also residual water bound in the cake after drying, which is invisible and never nil. TFA and acetate salt forms covers the counter-ion, and residual moisture covers the water.
That is not a discrepancy, and neither inflates the content figure, because the content assay measures peptide rather than powder. The two numbers are consistent with each other and the powder on the stopper is simply heavier than either.
Storage
As a sealed dry solid, comparatively robust. Water is the medium most degradation routes need and lyophilisation has removed it, which is why these ship at ambient temperature across the industry without that being a corner cut.
Once reconstituted the position changes and both clocks start: elapsed time and the number of entries into the vial. Freeze-thaw cycles and aliquoting covers the first and vial closures the second.
What varies legitimately between lots
Content within the fill tolerance, purity within a narrow band, and retention time within a small range characteristic of the compound rather than the batch. Those three moving slightly is ordinary and is what lot-to-lot consistency describes.
What should not move is the identity result or the mass. A mass that differs between lots of the same compound, with the method unchanged, is a question rather than variation.
Before placing a first order
- Ask for the certificate matching a specific lot you would receive, which separates lot-level traceability from product-line documentation immediately.
- Ask which laboratory issued it and whether its accreditation covers the methods used.
- Ask which salt form is supplied, since it is rarely on the document.
- Ask what the lead time is for in-stock versus made-to-order, because those are different numbers.
Auditing a peptide supplier is the longer version of that checklist.
Scope
LY3437943 is supplied for laboratory research only. Nothing here describes effects in any organism, and nothing on a certificate speaks to them. What documentation settles is what the material is, how pure it is and how much of it there is.
What to do if a lot does not reconcile
Stop using it, photograph the vial and label, keep the packaging, and put the question to the supplier in writing. A discrepancy that is explained is a documented anomaly; one that is not is an open question attached to material already in use.
Where the work depends on it, independent identity testing answers the question directly, and an accredited laboratory will accept a single sealed vial. Counterfeit and mislabelled material covers the checks that catch most of this at receiving.
Records worth keeping for this compound
- The lot and the certificate, stored as your own copy.
- The measured content, which differs from the label and is the figure calculations use.
- The identity method named on the certificate, since it determines what the identity line established.
- The salt form, obtained by asking.
- Reconstitution date, solvent, measured volume and resulting concentration.
Records to keep covers how those tie together into something that answers a question months later.
Comparing suppliers for this compound
Price differences on a widely available compound usually reflect differences in what was tested rather than differences in efficiency. The useful comparison is therefore documentation first and price second, among suppliers who clear a documentation threshold you set in advance.
That threshold should be explicit: a lot-matched certificate, a named testing laboratory, a method stated for every result, and an identity method you consider adequate for a modified peptide of this length. Anyone below it is excluded rather than scored.
Lead time, and why it is two numbers
An item held in stock ships in days. An item made to order waits for a synthesis slot, purification and release testing, which is weeks. Suppliers quote one figure and deliver two, and planning against a blended number guarantees being wrong in both directions.
Ask for both explicitly and record which applies. It also changes what a stockout costs, because a stocked item can be recovered quickly and a made-to-order one cannot be recovered inside a month.
In short
A triple agonist across five strengths. Identity carries more weight here than for a short sequence, the certificate content figure is the number to calculate with, slow dissolution is expected, and the paperwork is where suppliers actually differ.
A note on blends containing this compound
Where LY3437943 appears in a combination product (this catalogue lists LY3437943 / AM833 at 12.5 mg / 2.5 mg), the certificate usually reports content for one component rather than the vial total, so a figure that looks low is often correct. Reading it as the total is the commonest misreading of a blend certificate.
A thorough blend certificate confirms identity for each component independently rather than inferring the second from the recipe, and reports a measured ratio rather than an intended one. Blends and single vials covers the reading.
Where this sits
For how LY3437943 compares structurally with the other incretin-class compounds, NN9535, LY3298176 and LY3437943 compared sets the three side by side. For the class as a whole, GLP-1 and incretin peptides covers what the category actually is. For the two-receptor compound as a purchase, buying LY3298176 covers its vial sizes and certificates.
One closing practical point. Record the strength alongside the lot in your usage log, because a compound supplied across five strengths (10, 20, 30, 48 and 60 mg) produces records where the lot alone does not tell a later reader how much peptide was in the vial.
A last word on documentation
Keep your own copy of every certificate rather than a link to the supplier archive. Links move, documents are superseded when a lot is replaced, and a reference that no longer resolves looks like a record right up until someone follows it.
This is one part of buying wholesale. The wholesale buying guide covers the whole process from evaluating a supplier to placing a first order.