two new peptides join the board this week, and they have almost nothing in common except the last four letters of their names. brenipatide is a fresh bet: a Lilly injectable aimed at addiction and mood, with not a single efficacy result published yet. larazotide is a closed case: a celiac pill that ran its make-or-break trial and did not clear the bar. this piece lays out the concrete version of each, what it is, what it is for, how it works in one plain sentence, and what results exist so far.
why two different -tides do two different jobs.
the shared -tide ending carries almost no information. it just signals that the drug is a peptide, a short chain of amino acids. the rest of the name is where the job hides. larazotide's -zotide is a specific naming stem that marks a zonulin antagonist, a class of gut-barrier drugs. brenipatide's -tide puts it among the incretins, gut hormones that tell the brain you are full and help tune blood sugar and metabolism. it shares its -patide ending with tirzepatide, a dual GIP/GLP-1 drug, and the broader -tide stem with the rest of the GLP-1 family, semaglutide included. so the names already sort these two into different worlds: one guards the gut lining, the other works on the reward system. same suffix, opposite errands.
lilly is pointing its incretin at addiction and mood.
brenipatide is Eli Lilly's subcutaneous injectable peptide, carried in the pipeline as LY3537031. its trial design places it in the incretin class, gut hormones that signal fullness and tune metabolism, the same family as the GLP-1 drugs. Lilly has not confirmed the exact receptor target in its own disclosures, though outside databases describe it as a dual GIP/GLP-1 agonist, the same receptor pair as tirzepatide. what makes it unusual is where Lilly is aiming it. the flagship program, called RENEW, targets addiction and mood rather than obesity. one quick note on the trial ladder those programs sit on: phase 2 asks whether a drug works at all in a few hundred people, and phase 3 is the large, make-or-break test regulators want to see. brenipatide has phase 3 studies in alcohol use disorder and major depressive disorder, plus phase 2 work in opioid use disorder, smoking, bipolar disorder, and schizophrenia.
the thesis, and this is about the incretin class rather than brenipatide specifically, is that GLP-1 drugs act on the brain's reward circuits, and reward circuits are where craving and relapse live. in practice the bet is that the same brain signal these drugs use to quiet appetite for food also quiets the urge for a drink, a cigarette, or an opioid. the class has already thrown off a craving-reduction signal: the proof-of-concept everyone points to is the Klausen 2026 Lancet RCT, where semaglutide cut heavy-drinking days by about 14 percentage points versus placebo, in people who had both alcohol use disorder and obesity and were getting therapy in both arms, covered in our piece on GLP-1 and alcohol. brenipatide is Lilly's purpose-built swing at that idea across several disorders at once.
results so far amount to none. eleven brenipatide trials are registered, three of them in phase 3, and every one is still enrolling. zero efficacy has been published, nothing appears in PubMed or ChEMBL, and the drug is not approved or available anywhere. the phase 3 anchors, two in alcohol use disorder (RENEW-ALC-1 and RENEW-ALC-2, about 1,100 each) and one in major depressive disorder (RENEW-MDD-1, about 1,000), are scheduled to read out around 2028. so the first real answer on whether this works is roughly two years away, and until then brenipatide is a clean thesis with zero human efficacy behind it.
the oral gut-barrier drug that got its shot.
larazotide acetate, coded AT-1001, is a first-in-class synthetic octapeptide, eight amino acids long, developed by 9 Meters Biopharma after originating at Alba Therapeutics, where Alessio Fasano's lab mapped the zonulin pathway it targets. it is a zonulin antagonist, taken by mouth, and it works locally in the gut lumen with minimal absorption into the bloodstream. its job is narrow and specific: celiac disease, given as an add-on to a gluten-free diet for patients who still have symptoms despite avoiding gluten.
the mechanism is unusually clean, which is what made it attractive. in celiac disease, gluten triggers the release of a protein called zonulin, and zonulin loosens the tight junctions, the seals between the cells lining the gut. once those seals loosen, gluten fragments slip through and provoke the immune reaction that damages the gut wall. larazotide blocks zonulin to hold the seals shut, keeping the fragments out. it works at the barrier itself, upstream of the immune response rather than on the immune system downstream.
here the two peptides part ways, because larazotide actually has results. a positive phase 2 (Leffler et al., Gastroenterology 2015) found that 0.5mg three times daily cut the abdominal pain, bloating, and diarrhea that celiac patients still get even on a strict gluten-free diet, with higher doses offering no added benefit. that earned it a phase 3, CeDLara (NCT03569007), which enrolled several hundred patients. in June 2022 a pre-planned interim analysis concluded the trial could not feasibly reach statistical significance, and it was terminated. in plain terms, the drug did seem to help, but not clearly more than a placebo pill, so the trial could not prove the benefit was real. the program has been discontinued with no development since. the sticking point was the size of the effect, and safety was never the issue.
the phase 3 readout is what separated them.
line them up and the science underneath is comparably serious for both. what differs is how far each reached down the trial path. brenipatide is promising and unproven: a plausible mechanism, a class that has already thrown off a craving signal, serious money, a bold target, and no efficacy data yet, so watch the 2028 readout and hold judgment. larazotide was promising too, a clean mechanism and a positive mid-stage trial, and then it got tested at full scale and the effect came out too small to clear the bar. the gap between a bet and a verdict is a phase 3 that reads out, and only one of these two has had it.