How to read a phase 2 result without treating it as a phase 3 result

The question in the title: How to read a phase 2 result without treating it as a phase 3 result I will give what I have already checked below so nobody repeats it.

Session topic: FLOW (N Engl J Med, 2024). Please read it before posting; the discussion is much better when everyone has.

The question I would like us to start with is what the trial set out to estimate, rather than what it found. Once that is on the table we can talk about whether the design could have answered it, and only then about the numbers.

Specific things I would like covered: the population and how far it generalises, how discontinuation was handled, whether the comparator was a fair one, and what the absolute rather than relative effect looks like.

I will summarise at the end and the summary will feed the relevant digest page.

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

Why this subcategory is more cautious than elsewhere: retatrutide is investigational, phase 3 is ongoing, and the heart-rate signal in phase 2 is not negligible. Caution is proportionate to the evidence status.

Dose escalation in the published trials: the protocols started at lower doses and escalated by defined steps. The step sizes are documented and they may or may not match what someone self-prescribing would choose.

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.

Retatrutide is investigational. Anything obtained outside a trial is by definition research-use-only material with no human-use authorisation. This site will state that plainly rather than winking at it.

This follows post #3 rather than contradicting it.

Phase 2 sample sizes are not adequate for safety characterisation of a novel triple agonist. Phase 3 is where that question gets answered. Using phase 2 results to make claims about safety profile is using the trial for a purpose it was not designed for.

Worth separating two things that post #3 runs together.

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.

The phase 2 obesity paper reported dose-dependent weight reduction of a magnitude that attracted attention. It also reported dose-dependent heart-rate increases. The heart-rate signal is the reason phase 3 exists rather than something assumed negligible based on phase 2.

Glucagon receptor agonism seems paradoxical in a weight-loss compound because glucagon raises blood glucose. The paradox resolves because glucagon agonism also increases energy expenditure and promotes hepatic fat oxidation, and the incretin components offset the glycaemic effect. In diabetes trials, HbA1c improved rather than worsened.

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.

Triple agonism: is the effect additive, synergistic, or neither? A phase 2 comparison of tirzepatide (dual) to retatrutide (triple) would answer that question. The published data does not include such a direct comparison.

Hepatic effects: glucagon receptor agonism promotes hepatic fat oxidation, which is mechanistically plausible for benefit in metabolic liver disease. Whether that translates to improved clinical outcomes is being tested in phase 2 work.

post #12 answers the question as asked. The question underneath it is different.

How to read phase 2 without treating it as phase 3: phase 2 establishes that a dose range produces an effect and is tolerable enough to justify large trials. It does not establish safety, durability, or whether real humans differ from the selected population.

On post #10 — agreed on the reasoning, with one qualification.

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.