Twelve injections a year instead of fifty-two is the pitch, and two compounds are far enough along to test it. Neither can be bought. Maridebart cafraglutide and berobenatide are investigational, no product containing either appears in Drugs@FDA, and no seller ranked on the compounded tirzepatide board offers anything of the kind. What has been published is a phase 2 result, a phase 1 pharmacokinetic finding and a set of registered phase 3 protocols, and read together they say something more interesting than the pitch: the monthly interval is not what does the work, and it is not what the larger trials are testing.
What maridebart cafraglutide is, and why it lasts
The molecule is not a peptide in the usual sense. It is a bispecific construct made by conjugating a fully human monoclonal antibody that antagonizes the GIP receptor to two GLP-1 analog agonist peptides through amino acid linkers. In the phase 1 trial in participants with obesity, dose-dependent weight loss appeared with an acceptable safety profile, and in the multiple ascending dose cohorts weight loss was maintained for up to 150 days after the last dose.[1] That persistence is what makes a monthly schedule pharmacologically possible, and it is also the first thing a reader should weigh against it. A drug that is still working five months after the last injection is a drug that cannot be switched off quickly if it is doing something unwanted. The antibody scaffold is the source of the duration.[2]
The phase 2 result, including the half that is usually dropped
The phase 2 trial randomized 592 participants into eleven groups across two cohorts. In the obesity cohort — 465 participants, 63% female, mean age 47.9, mean body-mass index 37.9 — doses of 140, 280 or 420 mg every 4 weeks, 420 mg every 8 weeks, and 420 mg every 4 weeks with either 4-week or 12-week escalation were tested against placebo. Mean percent change in body weight at week 52 on the treatment policy estimand ranged from −12.3% (95% CI, −15.0 to −9.7) to −16.2% (95% CI, −18.9 to −13.5), against −2.5% (95% CI, −4.2 to −0.7) on placebo.[3]
The second cohort is where the number moves. In 127 participants who had obesity and type 2 diabetes, the same doses produced a range of −8.4% (95% CI, −11.0 to −5.7) to −12.3% (95% CI, −15.3 to −9.2), against −1.7% on placebo. Glycated hemoglobin fell by 1.2 to 1.6 percentage points against a 0.1 point rise on placebo.[3] Every point of the diabetes range sits below the corresponding point of the obesity range; the top of the diabetes cohort equals the bottom of the obesity cohort. Roughly a third of the weight effect is absent in the group with diabetes, which is the same direction, and a similar size, as the split described in the diabetes versus weight loss article. A summary quoting only “up to 16.2%” is quoting a real figure and describing half a trial.
The interval is not what made it tolerable
The intuitive case for monthly dosing is that fewer exposures mean fewer bad days. The trial does not report that. Gastrointestinal adverse events were common with maridebart cafraglutide, and the authors record that they were less frequent with dose escalation and a lower starting dose.[3] Two of the eleven groups existed precisely to test escalation — 420 mg every 4 weeks reached over 4 weeks, and the same dose reached over 12 weeks — and it is that variable, not the gap between injections, that the tolerability finding attaches to.
This matters for anyone reading a monthly schedule as a simplification. Titration is the part of GLP-1 treatment that generates the appointments, the dose decisions and most of the nausea, and it is described in the titration article. A monthly injection that still requires a graded climb has moved the needle count without removing the climb. The published data says the climb is what buys the tolerability.
The second candidate builds monthly out of weekly
Berobenatide, developed under the codes MET097 and PF-08653944, is described in its registered protocols as an ultra-long-acting GLP-1 receptor agonist. Its once-monthly phase 2b carries a registered title that states the design outright — once-weekly switching to once-monthly — and its summary describes testing multiple monthly doses after twelve weekly doses. The trial enrolled 268 participants, ran from April 2025 with primary completion in December 2025, and measured percent change in body weight at week 28.[4] No peer-reviewed report of it is indexed in PubMed, so nothing about its results is stated here.
Monthly, in that design, is a maintenance regimen arrived at through three months of weekly injections. It is not a starting schedule, and a reader picturing twelve appointments a year from day one is picturing something the protocol does not describe.
What the sponsors are actually betting on
The enrollment numbers are the clearest statement of confidence available while the results are embargoed. The largest registered phase 3 of berobenatide is VESPER-4, which enrolled 3,578 participants to an once-weekly regimen, began in December 2025 and reports its primary endpoint after 64 weeks. The once-monthly phase 3 trials are smaller: VESPER-6, with an estimated 954 participants, which began recruiting in June 2026 with primary completion estimated for May 2028, and a 197-participant Japanese trial not yet recruiting, with primary completion estimated for February 2029.[4] Roughly three participants are enrolled on the weekly program for every one targeted on the monthly one.
Amgen’s program is larger and runs on the four-week interval throughout. Its registered phase 3 studies include a 3,853-participant weight trial in adults without type 2 diabetes reporting at week 72, a 5,056-participant trial in heart failure with preserved or mildly reduced ejection fraction, and a cardiovascular outcomes trial with an estimated enrollment of 12,800 that began in July 2025 with primary completion estimated for June 2028, measuring time to first cardiovascular death, myocardial infarction or ischemic stroke.[4] Nothing about cardiovascular outcomes for either compound is known until those report, which is the same caution that applies to the approved drugs in the cardiovascular article.
A census with its blind spot named
A search of ClinicalTrials.gov for studies whose official title contains the phrase “once-monthly” in obesity or overweight returns exactly three, and all three are Pfizer’s berobenatide trials.[4] That is not a complete list of monthly programs and should not be read as one: Amgen registers its interval in the protocol rather than the title, so a phrase search cannot see the MariTide program at all. What the search does establish is that the phrase is rare in the registry, and that the field of compounds with published or registered monthly dosing in obesity is small enough to name in a sentence.
Why a dose range is not a dose
Both cohort figures above are ranges rather than single numbers, and the reason is worth stating. The obesity cohort was split across seven groups at three dose levels, two intervals and two escalation schedules, so “−12.3% to −16.2%” spans very different regimens rather than describing one. The trial reports on the treatment policy estimand, which counts what happened to participants including those who stopped early, so the figures are not a best case among completers. A phase 2 dose-ranging trial exists to find the regimen worth testing, which means at least one of the numbers inside that range belongs to a regimen nobody intends to market, and none of them is a prediction of what phase 3 will report.
Nothing else in the pipeline is monthly
The interval is the exception, not the direction of travel. Every FDA-approved incretin product is dosed weekly or daily, the approved oral small molecule is a daily tablet covered in the orforglipron article, and the trade-offs between a daily and a weekly schedule in the products that already exist are set out in the weekly versus daily article. Two companies are testing a monthly schedule; one of them is running its largest trial on a weekly one. That is the state of the field, and it is a narrower thing than a shift toward monthly dosing.
What monthly dosing would change, and what it would not
It would change the number of injections, and for anyone whose obstacle is the injection itself that is not trivial. It would not change the titration, on the published evidence. It would not change the class adverse-effect profile, which is gastrointestinal in both compounds. It would not shorten the time to a decision about whether the drug is working, since both phase 3 programs read out at 64 to 72 weeks.
And it would lengthen the tail. A molecule whose effect persists up to 150 days after the last dose[1] cannot be stopped the way a weekly injection can, which changes the arithmetic around pregnancy planning, scheduled surgery and any adverse event that calls for withdrawal — the considerations set out in the tapering article. What neither compound has is a marketing authorization: neither can be lawfully purchased in the United States, neither has an approved label, dose ladder or contraindication list, and a compounded preparation claiming to be either would have no approved reference product behind it. Compounded drugs are not FDA-approved and are not reviewed by the FDA for safety, efficacy or quality before dispensing. How every figure here was established is described in the methodology.