What did SURPASS-2 do with participants who could not tolerate a step?

I am asking about the protocol logic rather than about my own case specifically.

I can parse the result. I am less sure what it licenses me to conclude.

I have deliberately not looked at anyone else’s interpretation yet.

Which parts of this are informative and which are decoration?

SURPASS-2 would have written it into the protocol, and the wording is the part that matters. Escalation protocols in this class generally permit a delay at the current level, sometimes a single step down with a later re-attempt, and count a participant as remaining in the arm throughout. That is analytically important: an intention-to-treat analysis keeps them at their randomised assignment regardless of the dose they were actually taking, so the "top dose" arm contains people who never reached the top dose. Find the protocol amendment history as well as the paper, because tolerability rules are among the things most often revised mid-programme, and dose-escalation decisions are made under supervision — nothing here is medical advice.

The relevant arithmetic is that steady state takes four to five half-lives, so a one-week half-life means a four-week step interval and nothing shorter is informative.

Holding a step for eight weeks instead of four is a legitimate approach with no efficacy cost at the destination, and it is what the trials effectively did for anyone who tolerated poorly.

Weekly dosing accumulation, 7-day half-life

This is why a four-week step interval is approximately, but not exactly, steady state.

Titrating downward is available too. Stepping back and holding is a normal adjustment rather than a failure.

Faster titration does not reach the destination sooner in any way that matters; it reaches the symptoms sooner.

Four half-lives between steps, minimum. Work it out for your agent.

The honest answer is that going slower costs time and nothing else, since the exposure ceiling is unchanged.

For an agent with a one-week half-life, steady state after a dose change is reached in about four to five weeks. Escalating at two weeks means escalating from a position you have not yet reached, and the resulting exposure is higher than the schedule intends.

The published semaglutide weight-management schedule steps 0.25, 0.5, 1.0, 1.7 and 2.4 mg at four-week intervals, with 0.25 mg as an initiation step rather than a therapeutic one.

Hold rather than escalate while symptoms are active. Always.

Start with the half-life, because the interval between steps should be at least four half-lives or you are escalating before the previous step has expressed itself.

The published tirzepatide schedule steps 2.5, 5, 7.5, 10, 12.5 and 15 mg at four-week intervals, with 2.5 mg as the initiation step rather than a therapeutic one.

Stated carefully, the dose that produces an acceptable result with acceptable tolerability is the endpoint, not the top of the schedule. A substantial fraction of trial participants did well below the maximum.

Titration schedules in the licensed products were designed specifically to manage gastrointestinal tolerability, and that intent is stated in the clinical development literature.

A schedule described here is a published schedule for a licensed product and is not a recommendation.

Slower costs time and nothing else. The ceiling is the same.

The relevant detail is that escalating while symptomatic resets the tolerance process and is the mechanism behind most miserable titrations.

Liraglutide titrates weekly rather than four-weekly because its half-life is about thirteen hours, so steady state is reached within days. The interval follows the pharmacokinetics in both cases.

Four to five half-lives to steady state is standard first-order pharmacokinetics and gives the four-week interval directly from the one-week half-life.

The top of the schedule is not the target. The working dose is.

Answer first: the titration schedule exists to let tolerance to the gastrointestinal effects develop between steps, and every step in it is a tolerability decision rather than an efficacy one.

Escalating while gastrointestinal symptoms are still active is the commonest avoidable error. Tolerance to the previous step has not developed, and the new step lands on top of it.

Trial data show gastrointestinal adverse events concentrated in the escalation phase and declining at stable doses.

The caveat is that titration decisions belong with a clinician who knows what else is on board.

Stepping back is a normal adjustment, not a failure.

edited 5 Oct 2024 by esther_vandeVelde — added the placebo-arm figures