What happens to orforglipron after two weeks at 37 °C in solution?

What I am working with: orforglipron · two weeks · 37 °C.

The empirical answer seems settled. The explanation does not.

If the honest answer is that nobody knows, I would rather hear that than a plausible story.

What is the causal chain, and where does it stop being established?

two weeks is 14 days, which at 37 °C is on the order of 129 refrigerated days. 37 °C is 32 kelvin above the 5 °C middle of a 2–8 °C refrigerator. The ten-degree rule of thumb — degradation rate roughly doubling per 10 K — makes that about 9.2 times the refrigerated rate, which is an order-of-magnitude statement and not a shelf life. In solution the routes that matter are hydrolysis of the backbone, deamidation at Asn, and physical association — the first two cost content, the third costs neither until it precipitates. Over 14 days at 37 °C you should expect all three to have moved, and a purity figure to have noticed only some of them. Reconstituted material has no certificate; the one in the box describes the powder.

Start with the sequence, because which pathways are available depends on which residues are present.

Aggregation is physical: peptides unfold at air-liquid interfaces and associate. Shaking maximises that interface, which is why swirling and shaking produce visibly different outcomes on the same vial.

Reported and extrapolated stability by condition

Windows for the solid state are chemical; windows for solution are microbiological and usually shorter than the chemical limit.

Put another way, light exposure matters for tryptophan-containing sequences and for anything with a chromophore. Amber vials and a closed box are free mitigations.

Metal-catalysed oxidation of methionine is documented across peptide and protein formulations and is why chelators appear in some formulations.

Nothing here is medical advice, and research-use compounds are not approved for human use.

Sequence decides which pathways are even available. Check the residues.

The honest answer is that most reported "degradation" is adsorption and dilution error rather than chemistry.

Oxidation targets methionine, cysteine and tryptophan, adding sixteen daltons per oxygen. It is catalysed by trace metals and promoted by dissolved oxygen and by light.

The relevant detail is that adsorption onto glass and plastic is significant at low concentrations — micrograms per millilitre — and negligible at milligrams per millilitre. It is the usual explanation for an apparent loss in a dilute preparation.

Adsorption losses at low concentrations are quantified in formulation studies and are the reason carrier proteins are used in dilute preparations.

The caveat is that none of these pathways can be seen by looking at a vial, and a clear solution can be substantially degraded.

At dilute concentrations, suspect adsorption before you suspect chemistry.

The relevant point is that a mass shift of plus one dalton is deamidation and plus sixteen is oxidation, so degradation is often visible in a mass spectrum if anyone looks.

A mass spectrum resolves most of this: minus eighteen is dehydration or succinimide, plus one is deamidation, plus sixteen is oxidation, and an unchanged mass with a shifted retention time is an isomer.

Deamidation converts asparagine or glutamine to the corresponding acid via a succinimide intermediate, adding one dalton. It is base-catalysed, accelerates above neutral pH and is the dominant aqueous pathway for many peptides.

Aggregation at air-liquid interfaces is established from surface-tension and particle-count studies and is the basis for anti-agitation handling guidance.

Apparent loss in a dilute preparation is usually adsorption rather than degradation and is worth ruling out first.

A mass spectrum names the pathway. Plus one, plus sixteen, minus eighteen.

Worth being precise here: this is answerable from the chemistry rather than from anecdote, which is unusual and welcome.

Freeze-thaw cycling drives aggregation through concentration at the ice interface and pH shifts as buffer components crystallise out at different rates. Each cycle costs something.

Deamidation via the succinimide intermediate is well characterised, with sequence-dependent rates highest for asparagine-glycine motifs.

Cold, dry, dark, still. Those four words cover most of the mitigation.

Answering this needs the physical state, since a dry powder is protected from most of these and a solution is protected from none.

Hydrolysis cleaves the backbone, most readily at aspartate-proline and aspartate-glycine sequences, and is acid-catalysed. In a dry solid it barely proceeds at all.

Deamidation kinetics for asparagine in peptides are well characterised and strongly sequence-dependent: the residue following the asparagine dominates the rate, with glycine and serine at the n+1 position accelerating it by an order of magnitude relative to bulkier residues. That is why two peptides in the same buffer at the same temperature can have quite different shelf lives.

Swirl, never shake. Aggregation is a handling problem more than a time problem.