Journal club: the retatrutide phase 2 obesity paper

Journal club: the retatrutide phase 2 obesity paper — setting out what I have, and where I think it stops being reliable.

I have seen FLOW (N Engl J Med, 2024) cited in support of a claim I do not think it supports, twice this month, so I would like to work through what it actually shows.

My reading is that the trial is sound for its own question and is being stretched to answer a different one. I might be wrong about that, which is why this is a topic rather than a correction.

What I would like from this discussion: someone who disagrees with me to say why, with the section of the paper they are relying on.

Critical appraisal template: (1) What did the trial set out to estimate? (2) Could the design answer that question? (3) Was the population sufficiently similar to your population to apply the results? (4) What was the absolute effect, not just the relative one? (5) What are the two strongest criticisms available?

STEP 1 (N Engl J Med 2021): The pivotal obesity trial for semaglutide and the reference point for most subsequent comparison. Mean weight reduction was substantially larger than anything previously achieved pharmacologically.

I read post #3 twice before replying, because I had assumed the opposite.

SELECT (N Engl J Med 2023): Semaglutide cardiovascular outcomes without diabetes. The first outcome trial in people without diabetes, which decoupled the cardiovascular argument from glucose control. Read the absolute numbers, not just the relative reduction.

This follows post #3 rather than contradicting it.

Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up.

SURMOUNT-1 (N Engl J Med 2022): Tirzepatide obesity trial. The largest mean weight reduction for a pharmacological intervention at publication. Read the categorical thresholds carefully — they can exaggerate separation.

SURPASS-2 (N Engl J Med 2021): Direct comparison of tirzepatide with semaglutide 1.0 mg. The 1.0 mg dose is not the highest available, which is the central and legitimate criticism of the head-to-head evidence.

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

Picking up post #7: that is the part I would want checked first.

SOUL (N Engl J Med 2025): Oral semaglutide cardiovascular outcomes. Extends the cardiovascular evidence to the oral formulation. Note that oral bioavailability is lower and more variable than injectable.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.

Session format: read the paper before posting. The discussion is much better when everyone has. Start with the estimand and population, then methods, then results, then limitations. That order makes critique coherent.