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The case in front of me: semaglutide · 2–8 °C.
The claim is plausible, which is exactly why I want to check it.
I am able to read a paper if someone points me at one.
Has anyone verified this independently?
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Is there any published stability data for semaglutide at 2–8 °C?
5 Answers
Accepted answer first, then by votes114
Probably not at 2–8 °C specifically, because that is not where stability programmes take their readings. Accelerated work is conventionally run at 25 °C and 40 °C, with the refrigerated condition as the control, so 2–8 °C sits between or beyond the published points and what you will find is bracketing rather than a measurement. 2–8 °C is the condition the rule of thumb is anchored to, so it is the baseline rather than a multiplier: everything else in this thread is quoted relative to it. Whatever you find, check what was measured before you use it: a paper reporting purity at 2–8 °C has not measured content, and the two fail at different rates for different reasons.
Start with the sequence, because which pathways are available depends on which residues are present.
Light exposure matters for tryptophan-containing sequences and for anything with a chromophore. Amber vials and a closed box are free mitigations.
Reported and extrapolated stability by condition
| State | Condition | Usable window | Basis |
|---|---|---|---|
| Lyophilised solid | −20 °C, sealed, dry | 24–36 months | Supplier guidance |
| Lyophilised solid | 2–8 °C, sealed | 12–24 months | Supplier guidance |
| Lyophilised solid | 25 °C, sealed | 4–8 weeks | Extrapolated (Arrhenius) |
| Lyophilised solid | 40 °C, sealed | 1–2 weeks | Extrapolated |
| Solution, preserved | 2–8 °C | 28 days | USP microbiological convention |
| Solution, preserved | 25 °C | 3–7 days | Extrapolated |
| Solution, unpreserved | 2–8 °C | 24 hours | USP microbiological convention |
Windows for the solid state are chemical; windows for solution are microbiological and usually shorter than the chemical limit.
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.
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.
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3Adding for future readers: the domestic leg after delivery is the part you control. – mz_4113 5 months ago
4Small correction: it is the number of cycles rather than the freezer temperature that does the damage. – tri_gly_ala 6 months ago
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Shop standards43
This is answerable from the chemistry rather than from anecdote, which is unusual and welcome.
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.
Stated carefully, 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.
Sequence determines which pathways apply, so general statements are general.
A mass spectrum names the pathway. Plus one, plus sixteen, minus eighteen.
edited 29 Nov 2024 by Dr_Ingrid_Baumgartner — added the placebo-arm figures
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8I would add a sentence about light, since tryptophan-containing sequences care. – b_delacroix 2 months ago
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Answering this needs the physical state, since a dry powder is protected from most of these and a solution is protected from none.
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.
Put another way, 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.
Deamidation via the succinimide intermediate is well characterised, with sequence-dependent rates highest for asparagine-glycine motifs.
Apparent loss in a dilute preparation is usually adsorption rather than degradation and is worth ruling out first.
Cold, dry, dark, still. Those four words cover most of the mitigation.
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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.
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.
Adsorption losses at low concentrations are quantified in formulation studies and are the reason carrier proteins are used in dilute preparations.
At dilute concentrations, suspect adsorption before you suspect chemistry.
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Is there a reason to prefer minus eighty here, or is minus twenty genuinely enough? – rania_haddad 6 months ago
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The short version: water enables most of it, oxygen enables oxidation, surfaces enable adsorption, and agitation enables aggregation.
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.
Aggregation at air-liquid interfaces is established from surface-tension and particle-count studies and is the basis for anti-agitation handling guidance.
Swirl, never shake. Aggregation is a handling problem more than a time problem.
edited 30 Aug 2024 by deamidation_watch — added the method parameters
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Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.
Not medical advice. Research-use-only compounds are not approved for human use.