LY3437943's molecular identity is fixed and published: registry number CAS 2381089-83-2, molecular formula C256H392N64O79, molecular weight 4731.2, a 39-amino-acid backbone carrying a fatty diacid chain. Every other property discussed in the literature, from receptor selectivity to how long the compound stays measurable in circulation, follows from that structure. This article walks through the structural features the published papers describe and the elimination half-life figures reported for the molecule, without repeating the receptor-pharmacology ground covered elsewhere on this site.
| Attribute | Reported value or description | Source |
|---|---|---|
| Backbone length | 39 amino acids | Coskun et al., 2022 |
| Molecular formula | C256H392N64O79 | Registry data cited in Coskun et al., 2022 |
| Molecular weight | 4731.2 | Registry data cited in Coskun et al., 2022 |
| Lipidation | Fatty diacid chain attached through a linker for albumin binding | Coskun et al., 2022 |
| Receptor engagement | GLP-1, GIP and glucagon receptors, unbalanced potency ratio | Coskun et al., 2022 |
| Reported elimination half-life | On the order of several days, supporting once-weekly study visits in the published trials | Coskun et al., 2022; Urva et al., 2022 |
What does the published sequence design actually change?
Native incretin hormones such as GLP-1, GIP and glucagon are short, linear peptides that are broken down by circulating enzymes and filtered by the kidney within minutes of release. LY3437943's 39-residue backbone is a synthetic sequence engineered to present binding surfaces recognized by all three of those hormones' receptors, which a native single-hormone sequence cannot do (see how LY3437943 engages the three receptors for the receptor side of that story). The backbone alone is not what keeps the molecule in circulation, though. That job falls to the second structural feature: the fatty diacid chain.
What does the fatty diacid chain do?
The chain is attached to the peptide backbone through a linker and gives the molecule a binding site for serum albumin. Once bound to albumin, a peptide is effectively shielded from the kidney's filtration threshold and from some proteolytic degradation, which is the mechanism responsible for stretching a native hormone's minutes-long presence in circulation out to a multi-day window for the engineered analog. This is not a mechanism unique to LY3437943. The same fatty-acid-acylation strategy for extending a peptide's presence in circulation through albumin binding has a longer history in engineered insulin analogs, where Jonassen and colleagues described the protraction mechanism in detail for insulin degludec, a different peptide hormone using a related acylation approach (Jonassen et al., 2012). Applying that same chemistry to an incretin backbone, rather than to insulin, is what distinguishes LY3437943's design lineage from that earlier work while borrowing its core logic.
How does LY3437943's chain compare with related fatty-acid-conjugated peptides?
NN9535 carries a C18 fatty diacid, while both LY3298176 and LY3437943 carry a C20 fatty diacid. Chain length affects how tightly the modified peptide binds albumin and how hydrophobic the finished molecule is, which is relevant at the bench because a longer, more hydrophobic chain can change solubility behavior during reconstitution and can shift retention time in reversed-phase HPLC purity testing. Coskun and colleagues' earlier discovery paper on LY3298176 (development code LY3298176) describes the same acylation logic applied to a dual GIP/GLP-1 backbone rather than the triple-receptor backbone used in LY3437943, which is a useful side-by-side reference for anyone comparing how chain chemistry interacts with backbone design across this peptide family (Coskun et al., 2018).
What elimination half-life do the published pharmacokinetic studies report?
Coskun and colleagues' discovery paper and Urva and colleagues' phase 1b multiple-ascending-dose trial both report an elimination half-life for LY3437943 on the order of several days, in the same general range as LY3298176's reported half-life and consistent with the albumin-binding mechanism described above (Coskun et al., 2022; Urva et al., 2022). That duration is long enough that the phase 1b trial's pharmacokinetic sampling and study visits were built around a weekly interval rather than daily sampling, a study-design detail reported in the trial's methods rather than a usage instruction. For general background on what elimination half-life measures and why it differs so much across the peptide family, see peptide half-life explained, which covers the NN9535 and LY3298176 figures from the same class of prescribing-information and pharmacokinetic literature.
Does the half-life reported in early trials match later trials?
Reported pharmacokinetic parameters can shift somewhat between a first-in-human single/multiple ascending dose study and a larger phase 2 population, because population pharmacokinetic models pool data across more participants and dose levels. Urva and colleagues' phase 1b paper is the more granular pharmacokinetic dataset, since it was designed specifically to characterize exposure and clearance across a dose range, while the later phase 2 efficacy trials report pharmacokinetics as a secondary rather than primary endpoint (Urva et al., 2022). Researchers comparing figures across papers should check which type of trial a given half-life estimate came from before treating two numbers as directly comparable.
Does every LY3437943 lot match the published structural data exactly?
The molecular formula, molecular weight and sequence design described in the discovery literature describe the compound as designed and characterized in that research program, and a research-grade lot should match those figures on its own certificate of analysis. That is a separate question from whether a given vial's mass spectrometry result matches the target value within the testing lab's stated tolerance, which is a lot-specific quality control question rather than a property of the molecule's published structure. Homegrown posts lot-specific specifications, including the mass spectrometry identity result, on the LY3437943 product page, alongside the current certificate of analysis for that lot. Researchers who want to see how identity, purity and net peptide content are reported and what each figure actually means for a structurally complex, lipidated peptide like this one can also read the site's dedicated guide to reading a LY3437943 certificate of analysis.
Why does any of this matter for study design rather than just background reading?
A researcher planning a study around LY3437943's pharmacokinetics, rather than its receptor pharmacology, needs to know roughly how long the compound persists in a system before picking sampling timepoints for an in vitro clearance assay or before interpreting a rodent pharmacokinetic dataset against the published human figures. The structural features described above, the backbone length, the fatty diacid chain and the resulting half-life, are the mechanistic explanation for why those sampling intervals look the way they do in the published trials, rather than an arbitrary study-design choice. Understanding the structure first makes the pharmacokinetic literature easier to read critically instead of taking a single reported half-life figure at face value.
Frequently asked questions
Is LY3437943's sequence a modified version of native GLP-1?
No single native hormone sequence. Published descriptions place the backbone in the broader engineered-incretin lineage that also produced LY3298176, built to present binding surfaces for three receptors at once rather than derived by minor substitution from any one native peptide (Coskun et al., 2022).
Why does chain length (C18 vs C20) matter for a fatty-diacid-conjugated peptide?
Chain length changes albumin-binding affinity and overall hydrophobicity. NN9535's C18 chain and LY3298176's or LY3437943's C20 chain are reported as functionally similar in purpose, extending circulating presence through albumin binding, but the exact affinity and pharmacokinetic profile differ by molecule and are reported separately in each compound's own pharmacokinetic literature.
Does a longer reported half-life mean a more potent receptor agonist?
No. Half-life describes how long a compound persists in circulation, which is a clearance property. Potency at a given receptor is a separate parameter, reported as an EC50 or similar value from binding and signaling assays. A molecule can have a long half-life and modest per-molecule potency, or the reverse.
What did the phase 1b trial's pharmacokinetic sampling actually look for?
Urva and colleagues' multiple-ascending-dose trial tracked plasma concentration over time across a range of dose levels in people with type 2 diabetes, generating the concentration-time curves used to calculate half-life, peak concentration and other standard pharmacokinetic parameters (Urva et al., 2022).
Is the C256H392N64O79 formula specific to LY3437943 alone?
Yes, that formula and the associated 4731.2 molecular weight are specific to LY3437943's exact sequence and chain structure as reported in the discovery literature; a related molecule such as LY3298176 has its own distinct formula and molecular weight, described in its own discovery paper (Coskun et al., 2018).
References
- Coskun T, Urva S, Roell WC, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept. Cell Metab. 2022;34(9):1234-1247.e9. PubMed 35985340.
- Urva S, Coskun T, Loh MT, et al. LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial. Lancet. 2022;400(10366):1869-1881. PubMed 36354040.
- Jonassen I, Havelund S, Hoeg-Jensen T, et al. Design of the novel protraction mechanism of insulin degludec, an ultra-long-acting basal insulin. Pharm Res. 2012;29(8):2104-2114. PubMed 22485010.
- Coskun T, Sloop KW, Loghin C, et al. LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: From discovery to clinical proof of concept. Mol Metab. 2018;18:3-14. PubMed 30473097.
Research use only. Homegrown Peptides products are for laboratory research and are not for human or animal use. Nothing in this article is medical advice.
