Is cagrilintide at 4 mg/mL stable enough for eight weeks of multi-withdrawal use?

Accepted answer

eight weeks is 56 days and, on a weekly schedule, 8 stopper punctures out of one vial at 4 mg/mL. Set the chemical question aside for a moment, because the puncture count is the one with a convention attached: 56 days is 2 times the twenty-eight days conventionally allowed for a preserved multi-dose preparation once it has been entered. Chemically, 4 mg/mL is high enough that adsorption to the glass is a rounding error and low enough that it is not protecting you from anything. What 8 withdrawals do add is 8 opportunities to introduce air, 8 coring events on the same stopper, and a headspace that grows with every draw — none of which show up on a certificate and all of which are avoided by splitting into aliquots at reconstitution.

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.

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.

More usefully, 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.

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

Sequence determines which pathways apply, so general statements are general.

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

edited 28 Nov 2025 by eighty_six_hours — removed a claim I could not source