Tirzepatide molecular mass and the charge states you would expect on ESI — does this still hold?

Asking directly, because I could not find a straight answer: Tirzepatide molecular mass and the charge states you would expect on ESI — does this still hold?

The question about Tirzepatide molecular mass that I actually want answered is the second one below. The first is context and I have kept it short.

Both are stated with units, and I have said what I already checked so that nobody repeats it.

Storage and stability: published data on licensed tirzepatide formulations exists and is worth reading directly rather than through summarised claims. Reconstituted preparations in different diluents have not been studied and extrapolation from the licensed formulation is the best you can do.

On reflection I would soften that slightly.

On identity: the monoisotopic mass is close to 4813.5 Da and the electrospray series usually shows the 3+ and 4+ states most strongly at ordinary concentrations. A report that shows only a single charge state is worth a question.

The evidence for this is thinner than the way I have phrased it suggests.

Answering the question the opening post raises rather than the one it answers.

The five maintenance doses in the tirzepatide programme give a genuine dose-response curve, which is unusual. Most trials in this space compare one or two doses against placebo and cannot say anything about the shape of the relationship.

Titration schedules for tirzepatide have more dose steps than semaglutide partly because the compound is more potent and partly because the clinical programme used a finer gradation. That does not mean you cannot escalate on a coarser schedule if that suits you — the published schedule is not a lower bound.

That has been true for the cases I have seen and I have not seen many.

Mass and charge states: tirzepatide is about 4813.5 Da and on an electrospray instrument you would expect to see charge states mostly in the 2+ to 4+ range, the same as semaglutide. A doubly charged species would appear at about (4813.5 + 2 × 1.008) / 2 ≈ 2408.

I have changed my mind on this once already, so take it as current rather than settled.

Adding the measurement that post #6 says would settle it.

Nausea profile: some people report tirzepatide as less nausea-prone than semaglutide, others report it as more. The trial reported gastrointestinal effects broadly comparable in character. Individual variation is the largest factor.

This settles it for me, at least until somebody posts a reason it should not.

The published pharmacokinetics show dose proportionality across the studied range, which means dose arithmetic behaves the way you would naively expect. That is not true of every compound and it is worth knowing which ones it is true of.

That is what I would do. It may not be what is correct.

Post #9 and I disagree about the size of the effect, not about the direction.

Comparisons between the tirzepatide and semaglutide programmes across trials rather than within one are weak. Different populations, different durations, different baseline characteristics; the only fair comparison is a head-to-head one.

Same conclusion as the reply above, reached differently, which is mildly reassuring.

Reading back through, this was answered upthread and I missed it. My fault.

Content versus purity applies here as everywhere: a lyophilised vial can be highly pure and contain less peptide than the label states, because the balance of the mass is water, counter-ion and excipient.

The short version is the first sentence; the rest is why.