Here’s a question that comes up in every serious peptide research discussion eventually: what happens when you stop? Most of the GLP-1 weight loss story so far has been about the losing phase. The maintenance phase, the part that stretches over years, has been the awkward gap in the whole incretin story. Viking Therapeutics just dropped data that might change how that conversation goes.
On September 22, Viking reported topline results from its VK2735-102 maintenance study, and the numbers were strong enough to send the stock up more than 25% in a single session. But the market move is the least interesting part. The interesting part is what the data says about dosing frequency.
What the Research Says
VK2735 is Viking’s dual GLP-1/GIP receptor agonist, the same mechanism class as tirzepatide. The maintenance study enrolled roughly 180 adults with obesity (BMI of 30 or above) who were otherwise healthy. Everyone started with a 21-week induction phase on weekly subcutaneous VK2735, with doses up to 22.5 mg. At week 21, participants were randomised to different maintenance regimens for another 12 weeks: continuing weekly dosing, dropping to every-other-week, going to monthly, or switching to placebo.
The headline results, from Viking’s September 22 press release:
- Participants transitioned to every-other-week dosing maintained up to 97% of their week-21 weight loss at week 33, versus 61% maintenance in the group switched to placebo (p<0.0001)
- Monthly dosing maintained up to 90% of weight loss against the same 61% placebo comparison (p=0.0002)
- Separation from placebo appeared as early as four weeks after the transition
- GI side effects during the maintenance phase were comparable to placebo - nausea, vomiting, diarrhoea and constipation rates dropped to background levels once the dose frequency came down
The induction phase numbers deserve a mention too. By week 21, 98% of participants on VK2735 had lost at least 5% of body weight, 90% had lost at least 10%, and 32% had lost 20% or more. The control group at those thresholds: 13%, 0%, 0%, and 0%. An exploratory cohort that stayed on 17.5 mg weekly through week 33 kept losing, reaching about 22% placebo-adjusted weight loss with no plateau in sight.
Why Maintenance Dosing Is the Actual Frontier
The standard incretin protocol is simple: inject weekly, indefinitely. Nobody has a great answer for what maintenance should look like, because most trials end before that question gets asked. Viking’s approach was to treat maintenance as a dosing problem rather than an on-or-off decision. Their CEO Brian Lian noted in the release that some maintenance regimens represented dose reductions of up to 85% while still preserving the weight loss effect.
That matters for a simple reason: adherence. If a maintenance regimen needs less frequent injections and produces fewer GI side effects, the calculus for staying on treatment over years changes completely. Viking reported that maintenance-phase GI adverse events were comparable to placebo, which is a very different tolerability picture from the induction phase.
There’s also an oral angle. Part 2 of the maintenance study will test oral VK2735 maintenance dosing, and Phase 3 trials of the oral formulation are planned to mirror the injectable VANQUISH program. The company says VANQUISH-1 (obesity) and VANQUISH-2 (type 2 diabetes) results are expected in 2027, with two additional oral Phase 3 studies to follow.
The Fine Print
This is a Phase 1-sized exploratory study - about 180 participants, 12-week maintenance window, healthy adults with obesity rather than the broader comorbidity populations the Phase 3 trials are targeting. The cohorts were small (the placebo maintenance group had 27 people; individual active cohorts were 12-13 per arm). Maintenance for 12 weeks is not maintenance for two years. Viking hasn’t selected doses for its planned extension studies yet and is awaiting FDA feedback on dose selection and frequency, per Zolmax’s trial coverage.
So treat this as a proof of concept, not a treatment protocol. But it’s a proof of concept for something genuinely new: the idea that the induction and maintenance phases of incretin therapy might be different things with different dosing logic. Nobody else in the pipeline is running maintenance studies structured this way. Viking’s VK2735-102 presentation slides are worth a read if you want the full breakdown - the topline data deck includes the PK rationale, which is essentially about VK2735’s long half-life making less-frequent dosing pharmacologically plausible.
For context on where this sits against the existing dual agonists, our tirzepatide overview covers the mechanism and trial landscape, and our retatrutide page covers the triple agonist side of the race.
If you want to dig into the cohort-level numbers with other people who actually read the tables, the Grey Highway Telegram group is where that happens.
Sources
- Viking Therapeutics press release, September 22, 2026: Positive Topline Results from Maintenance Study of VK2735
- VK2735-102 Maintenance Study topline presentation: Viking Therapeutics investor materials
- BioPharma Dive, September 22, 2026: Viking shares surge on updated obesity drug data
- Zolmax trial coverage: VK2735 Shows Strong Weight-Loss Retention With Monthly Dosing
Disclaimer: This article is for educational and informational purposes only. It does not constitute medical advice, therapeutic recommendations, or endorsements of any compound. Grey Highway is a research-education community. We do not sell, supply, or promote the use of research compounds. Always consult a qualified healthcare professional regarding health decisions. For Australian regulatory information, visit the TGA website.