SNAC and the mechanism of oral peptide absorption

On the subject in the title: SNAC and the mechanism of oral peptide absorption Working notes rather than a conclusion.

Comparing SELECT (N Engl J Med, 2023) with SURPASS-4 (Lancet, 2021) and finding the comparison harder than it looks.

Different populations, different durations, different endpoints defined slightly differently, and in one case a different estimand. People compare the headline percentages anyway, including me until recently.

Is there a defensible way to put these side by side, or is the honest answer that there is not and we should stop?

PIONEER 6 was a cardiovascular safety trial for oral semaglutide, not an efficacy trial. Non-inferiority for safety was demonstrated. The point estimates favoured the drug but the trial was not designed to establish benefit.

post #2 is right about the mechanism and I think understates the practical bit.

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.

Fasting instructions are not optional advice. Taking the tablet with food or with more than a sip of water measurably reduces absorption. This is the one compound in the class where the instructions genuinely determine the exposure.

Orforglipron is a small molecule, not a peptide. That changes almost everything: no absorption enhancer required, no fasting window, chemical synthesis instead of peptide synthesis, different analytical methods entirely. Data from peptide agonists does not transfer.

Oral versus injectable exposure: comparing a 14 mg oral dose with a 0.5 mg injectable dose is comparing apples to a different fruit. The oral bioavailability is low enough that dose numbers are an order of magnitude different and not directly comparable.

post #6 answers the question as asked. The question underneath it is different.

The SOUL trial: cardiovascular outcomes trial for oral semaglutide in people with type 2 diabetes and cardiovascular disease or chronic kidney disease. It demonstrates that benefit appears to be a property of the molecule and exposure, not specific to the route.

On post #4 — agreed on the reasoning, with one qualification.

Dose numbers for oral formulations are not comparable to injectable ones. The 14 mg oral dose is not equivalent to any injectable dose in the traditional comparison sense. They are different formulations with different pharmacokinetics and cannot be put on the same scale.

This follows post #6 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.

I read post #8 twice before replying, because I had assumed the opposite.

Why administration conditions matter for oral semaglutide and not for injectables: the oral formulation depends on a transient pH effect in the stomach. Anything that changes gastric pH or transit time changes absorption. Food does both.

Worth separating two things that post #7 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.

post #11 is right about the mechanism and I think understates the practical bit.

Oral bioavailability is variable between people. Some people absorb well; others absorb poorly. That inter-individual variation is larger than with injectables and is one reason the trial data for oral formulations receives different treatment.

PIONEER programme is phase 3 for oral semaglutide. The trials cover multiple indications and durations. Reading them requires attention to which trial is which because they are not all the same question.

Trial adherence in an oral trial with strict administration requirements is genuinely worse than trial-published data often suggests. That is why the exposure variability in oral formulations is mentioned repeatedly in the discussions here.