Why plausible mechanism is not evidence of effect

Asking directly, because I could not find a straight answer: Why plausible mechanism is not evidence of effect

Session topic: STEP 2 (Lancet, 2021). 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.

Publication patterns in the BPC-157 literature: a large proportion of the evidence comes from one research group. That is not necessarily wrong — one group can do excellent work — but it is worth noting when evaluating the breadth of support for a claim.

On post #3 — 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.

I disagree with the reply above, and I think the disagreement is substantive rather than terminological.

The distinction being drawn does not survive when you look at the published data for this specific question. I would be glad to be shown wrong on this, because the version I am arguing against is more convenient.

TB-500 is usually the 7-residue actin-binding fragment of thymosin beta-4, not the full 43-residue protein. The two are routinely conflated in supplier documentation and in the literature. Evidence about the full protein does not automatically apply to the fragment.

post #6 is right about the mechanism and I think understates the practical bit.

Oral versus injected administration claims for BPC-157: the preclinical work studied injection. Oral claims are common in supplier marketing and poorly supported by published evidence. If you are comparing orality between compounds, that is a distinction worth noting.

Reading a preclinical wound-healing model: the model shows whether a mechanism is plausible in a specific context. It does not show magnitude of effect in humans, does not show safety profile in humans, and does not show whether the effect survives in a more complex biological system. That is not a criticism of preclinical work — it is what preclinical work is for.

Picking up post #6: that is the part I would want checked first.

What would change the position on repair peptides: adequately powered, published, peer-reviewed randomised controlled human trials with pre-specified outcomes. That is the standard applied to every other therapeutic claim on this site and it is the standard applied here.

Coming back to post #8, because the follow-up matters more than the original answer.

For anyone arriving from search engines: this subcategory discusses published preclinical work and the absence of published clinical work. It does not endorse or recommend these compounds.

The distinction between "no evidence it works" and "evidence it does not work": we have the first for these compounds. That is genuinely different from the second and the distinction matters, but it also means treatment plans based on these compounds are being built on theoretical grounds, not empirical ones.

BPC-157: the preclinical literature is extensive, mostly from a small number of research groups, and reports effects across a wide range of injury models. The breadth of reported effects is itself worth noting — a compound that improves outcomes in tendon, muscle, gut, nerve and bone through a single mechanism would be remarkable, and remarkable claims deserve proportionate scrutiny.

Coming back to post #11, because the follow-up matters more than the original answer.

Two things before anyone answers the substance.

First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound.

Picking up post #11: that is the part I would want checked first.

The absence of adequately powered published randomised human trials is the central fact about BPC-157. This site states that plainly rather than hedging. Mechanistic plausibility does not substitute for it.