SURPASS-2 and the comparator dose question that will not go away posts 61–90

SURMOUNT-4's randomised withdrawal design is the strongest available evidence about what happens on stopping. It says nothing about a lower maintenance dose, because the comparison was continue versus placebo rather than continue versus less.

Worth separating two things that post #72 runs together.

An observation about SURPASS-2 that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful public than private.

SURPASS-2: I would want to see the raw numbers rather than the summary before agreeing. Summaries lose exactly the information that would settle this.

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.

I would put a moderate confidence on that and no more.

The 2.5 mg starting dose is a tolerance step and not a therapeutic one. Judging efficacy at that dose is the single commonest reasoning error in this subcategory.

If that is already documented somewhere, ignore me and link it.

Injection-site reactions were reported at a low but non-zero rate across the trials. The practical point is that a reaction at one site does not predict a reaction at the next, and rotating properly makes the question moot.

The documentation on SURPASS-2 is better than this thread and I say that as someone who has posted in the thread.

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.

Helpful, and easy to find again, which is half of what a good reply is.

Confirming post #81 from a second method, which matters more than confirming it from a second person.

SURPASS-2 has a well-known answer and a correct answer, and the interesting work is establishing that they are the same. Nobody has done that here yet.

Worth separating two things that post #81 runs together.

SURMOUNT-1 reported weight reduction of a magnitude that was the largest for a pharmacological intervention at that time of publication. It also reported a clear dose response across three doses. The categorical thresholds (people reaching 10%, 15%, 20% loss) got the most attention but read less informatively than the mean weight change.

I have left out the parts I could not verify.

On the mechanism question specifically: the honest position is that GIP agonism plausibly contributes and that the trial design cannot separate its contribution from simply achieving greater receptor engagement overall.

The reason SURPASS-2 is hard to answer is that the obvious measurement and the relevant quantity are not the same thing, and substituting one for the other is silent.

Categorical response thresholds — the proportion reaching ten, fifteen or twenty per cent reduction — are more persuasive and less informative than the mean. They depend entirely on where the threshold was drawn.

Second-hand, so weight it accordingly.

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.

This is where my knowledge stops and I would rather mark the edge than blur it.

Appreciated. The plain phrasing does more work here than a longer post would.