What is CT-388 (enicepatide)?

A late entrant with a $2.7 billion head start

Roche was not building an obesity drug of its own in 2023. It bought one. In December of that year, Roche agreed to acquire Carmot Therapeutics for $2.7 billion upfront, plus up to $400 million more in milestone payments, specifically for a small pipeline of incretin drugs already in clinical testing. The lead asset was a molecule called CT-388. The deal closed in July 2024, and by January 2026, Roche and its Genentech subsidiary had Phase 2 data strong enough to justify the price tag.

CT-388 has since picked up a permanent name, enicepatide, the international nonproprietary name assigned once a drug candidate is far enough along to need one. Most of the coverage from 2025 and early 2026 still calls it CT-388. Both names refer to the same once-weekly, subcutaneously injected drug.

Two receptors, engaged differently than tirzepatide

Enicepatide is a dual GLP-1/GIP receptor agonist, the same broad class as tirzepatide, the active ingredient in Zepbound and Mounjaro. Hitting both receptors is not new. How enicepatide hits them is the part Roche is emphasizing.

Tirzepatide is biased toward the GIP receptor and drives that receptor to internalize, meaning the receptor gets pulled inside the cell after the drug binds it, which changes how long and how strongly the signal lasts. Enicepatide was engineered differently: it produces a cAMP-biased signal at both the GLP-1 and GIP receptors, with minimal internalization at either one. Roche's own preclinical work found enicepatide's potency at the GLP-1 receptor outweighs its GIP activity, rather than the GIP-heavy skew tirzepatide has. The company's argument is that this signaling profile extends the drug's duration of action and limits the receptor desensitization that can blunt a drug's effect over time. Whether that translates into a real clinical advantage over years of use, rather than just a mechanistic footnote, is not something a single 48-week trial can settle.

What CT-388's Phase 2 trial found

The trial, CT388-103, enrolled 469 adults with obesity or overweight, none of them diabetic, and ran 48 weeks as a randomized, double-blind, placebo-controlled study across five dose cohorts. At the top 24mg dose, enicepatide produced 22.5% placebo-adjusted weight loss on the efficacy estimand, the measure of what the drug does when actually taken as prescribed. On the more conservative treatment-regimen estimand, which counts everyone as randomized regardless of adherence, the figure was 18.3%. Both are statistically significant against placebo.

The detail Roche highlighted hardest was that the weight-loss curve had not leveled off by week 48. Every major obesity drug eventually plateaus, the question is only when and at what percentage. A trial that ends before the plateau shows up leaves open the possibility that a longer study, which is exactly what Phase 3 is for, produces an even larger number. Among the subset of participants who entered the trial prediabetic, 73% had normal blood glucose by week 48, against 7.5% on placebo, a secondary result that matters for enicepatide's parallel development in type 2 diabetes.

Safety and tolerability

The adverse event profile lines up with what every incretin drug on the market already produces: nausea, vomiting, diarrhea, and constipation, concentrated in the dose-escalation period. Roche described the events as mostly mild to moderate. The number worth remembering is the discontinuation rate, since that is what actually predicts how many real-world patients stay on a drug long enough to get results. 5.9% of people on enicepatide stopped because of side effects, compared with 1.3% on placebo. That gap is real but not unusual for this drug class, and Roche reported no new or unexpected safety signals through 48 weeks.

What's next: Phase 3, and a possible combination with petrelintide

Roche started two pivotal Phase 3 trials, ENITH1 and ENITH2, in the first quarter of 2026. A separate study is testing enicepatide in adults who are overweight or obese with type 2 diabetes (NCT06628362). None of that is fast: a full Phase 3 obesity program typically runs two to three years, and industry estimates put a realistic launch around 2030, assuming the Phase 2 results hold up at larger scale.

Enicepatide is not Roche's only obesity bet. The company also licensed petrelintide, an amylin-only drug, from Zealand Pharma for $1.65 billion upfront, and the collaboration agreement explicitly covers combining the two into a single fixed-dose product down the line. That is the same playbook Novo Nordisk used to build CagriSema, pairing a GLP-1-class drug with an amylin drug on the bet that two mechanisms beat one. If Roche gets both molecules through Phase 3 on their own first, the combination becomes the more ambitious second act.

Where it stands now

Enicepatide will not reach a pharmacy for years, and a strong Phase 2 result is not a guarantee that Phase 3 repeats it at a larger scale. But it puts Roche, a company that spent 2023 and 2024 watching Novo Nordisk and Eli Lilly split the obesity market between them, into the conversation with a molecule that beat placebo by a wider margin than tirzepatide did at a comparable dose. For where the rest of the field stands right now, see retatrutide vs tirzepatide, the current leader by weight-loss percentage, or how CagriSema built the combination strategy Roche is now trying to copy.