Research

VK2735: Monthly Shots Held Most Weight Off, So Far

Creator: Priya Raman, Health Writer
Published: 2026-09-23

Viking says people kept most of their weight loss after moving from weekly VK2735 shots to monthly ones. What the 12-week study shows, what it can't tell you yet, and what it means for tirzepatide.

Priya Raman, Health Writer September 23, 2026 6 min read

Two friends sit together on a window seat

The short version

On September 22, 2026, Viking reported that after 21 weekly VK2735 shots (16.3% to 18.7% average weight loss), people switched to every-other-week shots kept about 90% of their loss over 12 weeks and those switched to monthly shots about 85%, versus 61% on placebo.
Those are topline company figures, not peer-reviewed results; weight change was an exploratory endpoint, and each maintenance group had 10 to 16 people.
VK2735 is a GLP-1/GIP dual agonist, the same class as tirzepatide. It is investigational, approved nowhere, and not available by prescription.
Its phase 3 VANQUISH trials (about 5,500 adults, 78 weeks of weekly shots) are fully enrolled, with estimated primary completion listed as July 2027.
For tirzepatide, SURMOUNT-MAINTAIN found that dropping to 5 mg weekly kept more weight off than stopping (−16.6% vs −9.9% at 112 weeks) but less than staying at the full dose (−21.9%). Nothing in the VK2735 study supports stretching tirzepatide or semaglutide beyond weekly.

Viking Therapeutics reported on September 22, 2026, that people who lost weight on weekly VK2735 shots held on to most of it after switching to a shot every other week or once a month. The catch: the switch was followed for only 12 weeks, in groups of 10 to 16 people, and the figures come from a company press release rather than a peer-reviewed paper. VK2735 is an experimental drug that no regulator has approved. If you're on tirzepatide or semaglutide, nothing about your treatment changes today.

What VK2735 is

VK2735 is an injectable weight-loss drug from Viking Therapeutics. It's a dual GLP-1/GIP agonist: one molecule that switches on the receptors for two gut hormones, GLP-1 and GIP, which help steer appetite and blood sugar after a meal. That puts it in the same class as tirzepatide, the drug in Zepbound and Mounjaro. Our how tirzepatide works explainer covers both signals.

Because it is still investigational, it isn't available by prescription, and anything sold online under that name is an unapproved product of unknown origin.

Its phase 2 trial, VENTURE, was published in the journal Obesity in January 2026. Among 176 adults with obesity or overweight and no diabetes, average weight loss after 13 weekly shots was 9.1% at the lowest dose and 14.7% at the highest, against 1.7% on placebo (Bays et al., Obesity 2026). Nausea was the most common side effect: 63% of people at the top dose reported it, versus 20% on placebo, and one in five at that dose stopped because of side effects.

What Viking's VK2735 maintenance study found

As of September 23, 2026, the day this article was written, the newest VK2735 data is Viking's topline release of September 22. "Topline" means the first headline numbers a company chooses to share; outside reviewers haven't checked the full results yet.

The study enrolled about 180 otherwise healthy adults with a BMI (body mass index) of 30 or more, the usual cutoff for obesity, in two stages:

Weeks 1 to 21: weekly VK2735 or placebo, with the dose raised every two weeks up to 15, 17.5, 20 or 22.5 mg.
Weeks 21 to 33: people who had lost weight on VK2735 moved to a shot every other week or every four weeks, often at a lower dose, or to placebo. One small group stayed on its weekly shot for comparison.

Stage and group	What Viking reported
21 weeks of weekly VK2735	16.3% to 18.7% average weight loss, by dose
21 weeks of placebo	0.1% average weight loss
Switched to every other week for 12 weeks	Kept 90% of their loss on average (83% to 97% by dose)
Switched to once a month for 12 weeks	Kept 85% on average (82% to 90% by dose)
Switched to placebo for 12 weeks	Kept 61%
Stayed on weekly 17.5 mg (13 people)	21.7% loss by week 33

In round numbers: for every 40 pounds lost by week 21, the monthly groups still held about 34 three months later, on average, and the placebo group about 24.

The headline "22% placebo-adjusted" figure (the placebo group's change subtracted) comes from that last 13-person group, which was down 21.7% while the placebo group had gained 0.3%.

Viking also reported that nausea, vomiting, diarrhea and constipation were about as common after the switch as on placebo. That fits the drug class, where stomach side effects cluster while the dose is being raised, as in tirzepatide's SURMOUNT-1 trial (Jastreboff et al., NEJM 2022).

What it means if you're on tirzepatide or semaglutide

The real question behind this news is personal: will I have to inject every week forever? Approved-drug trials already point to an answer. Weight tends to come back when treatment stops, and some ongoing treatment holds more of it.

In SURMOUNT-4, 670 people who had lost an average of 20.9% on tirzepatide were split in two. Over the next year, those switched to placebo regained weight equal to 14.0% of their body weight; those who stayed on tirzepatide lost another 5.5% (Aronne et al., JAMA 2024). Our walkthrough of SURMOUNT-4 explains who was in it.

SURMOUNT-MAINTAIN, published in The Lancet in May 2026, tested a lower dose instead. After 60 weeks at their top tolerated weekly dose, 378 people were randomly assigned to stay on it, drop to 5 mg weekly, or switch to placebo for a year. From the very start, average weight change at week 112 was −21.9%, −16.6% and −9.9% (Horn et al., Lancet 2026). The lower dose kept more weight off than stopping, and less than staying put.

Semaglutide shows the same pattern. In an extension of the STEP 1 trial, people who had lost an average of 17.3% on semaglutide regained about two-thirds of that loss in the year after stopping (Wilding et al., Diabetes Obes Metab 2022).

Viking is asking the same question, whether staying the course needs the full starting regimen, but pulling a different lever: how often, not only how much. The practical side of that decision lives in what happens when you stop taking tirzepatide.

What the VK2735 results do not mean

It doesn't mean tirzepatide or semaglutide can be stretched to monthly. Viking credits VK2735's long half-life, the time it takes the level in the blood to fall by half. Its phase 1 data put that at roughly 170 to 250 hours after a single shot, about 7 to 10 days, according to Viking's VK2735 program page. Tirzepatide's is about 5 to 6 days and semaglutide's about a week, and the Zepbound and Wegovy labels set their injections at once weekly. How often a dose is taken is the prescriber's decision.

It doesn't show VK2735 beats tirzepatide. The 21-week figures look strong, but comparing across trials misleads. SURMOUNT-1 followed 2,539 adults for 72 weeks and reported 15.0% to 20.9% average loss by dose, against 3.1% on placebo. Only a trial that gives both drugs to comparable people could settle it.

It doesn't prove maintenance holds long term. Twelve weeks is short. The weight results were exploratory: the study's stated goals were safety, tolerability and how the drug moves through the body. "Up to 97%" and "up to 90%" each describe a single group of 11 or 12 people. And the outside obesity specialist quoted in the release is, by its own footnote, a paid Viking consultant.

Where VK2735 stands, and what to watch next

Phase 3. VANQUISH-1 (about 4,500 adults with obesity) and VANQUISH-2 (about 1,000 with obesity and type 2 diabetes) compare weekly VK2735 with placebo over 78 weeks. Viking said on July 29 that both are fully enrolled (second-quarter update). ClinicalTrials.gov lists an estimated primary completion date of July 2027 for both (NCT07104500, NCT07104383), an estimate, not a results date.
The tablet. In phase 2, a daily VK2735 tablet was followed by up to 12.2% average loss over 13 weeks. Viking said in July it expects the tablet's phase 3 to start in the fourth quarter of 2026, and it now plans a tablet maintenance test.
Money. On September 23, Viking announced plans to raise about $400 million in stock and convertible notes for VK2735 and its other programs (announcement).

What a prescriber can consider today

The brand-name versions of today's weekly shots are Zepbound and Mounjaro for tirzepatide, and Wegovy and Ozempic for semaglutide. Through Promise, tirzepatide and semaglutide are dispensed as compounded medications, which is different from an FDA-approved product: the formulations offered here are not FDA-approved. A licensed provider may still prescribe a compounded formulation where they judge it appropriate; that decision is between you and your doctor.

At Promise, a licensed provider reviews every request, and not everyone qualifies. If a stall rather than stopping is the worry, why tirzepatide weight loss slows is a better place to start.

Common questions

What is VK2735?

VK2735 is an experimental weight-loss drug from Viking Therapeutics. It activates the GLP-1 and GIP receptors, the same two targets as tirzepatide, and is being tested both as a weekly injection and as a daily tablet. It is in phase 3 trials, no regulator has approved it, and it is not available by prescription.

Is VK2735 FDA-approved?

No. VK2735 is an investigational drug, and no regulator anywhere has approved it. Its two phase 3 injection trials, VANQUISH-1 and VANQUISH-2, are fully enrolled, and ClinicalTrials.gov lists an estimated primary completion date of July 2027. Anything sold online under the VK2735 name is an unapproved product from an unknown source, not a medicine with a label behind it.

How much weight did people lose on VK2735?

In Viking's September 2026 maintenance study, average loss after 21 weekly shots ranged from 16.3% to 18.7% by dose, against 0.1% on placebo, and a small group that stayed on weekly 17.5 mg reached 21.7% at 33 weeks. The earlier 13-week VENTURE trial reported up to 14.7%. These are trial averages, and the newest figures have not been peer-reviewed.

Can VK2735 be taken once a month?

Only as an experimental maintenance schedule so far. In Viking's study, people who had already lost weight on weekly shots and then switched to a shot every four weeks kept about 85% of their loss over 12 weeks, versus 61% for those switched to placebo. The phase 3 trials test weekly dosing, and VK2735 has no approved schedule of any kind.

Is VK2735 better than tirzepatide?

Nobody can say yet. No published trial has compared the two directly, and VK2735's studies have been shorter and smaller than tirzepatide's. In the 72-week SURMOUNT-1 trial, tirzepatide produced 15.0% to 20.9% average weight loss by dose, while VK2735's newest figures cover 21 to 33 weeks in about 180 people. Only a trial that gives both drugs to comparable people could answer the question.

Can tirzepatide be taken every other week or monthly?

Not on the evidence available. The Zepbound label lists once-weekly dosing only, and tirzepatide's half-life is about 5 to 6 days, shorter than the 7 to 10 days Viking reports for VK2735. Tirzepatide's own maintenance trial, SURMOUNT-MAINTAIN, tested a lower weekly dose, not longer gaps between shots. Any change to the schedule is a decision for the prescriber.

When might VK2735 be available?

There is no date. ClinicalTrials.gov lists July 2027 as the estimated primary completion for the two phase 3 injection trials, which is when the main 78-week measurements are expected to finish, not an approval date. After results, Viking would still need to file an application and wait for the FDA's decision. Viking said in July it expects to begin phase 3 of the tablet in the fourth quarter of 2026.