Genentech's CT-388 Shows 22.5% Weight Loss in Latest Study, Marking Major Breakthrough in Obesity Treatment

The weight loss study landscape just got significantly more crowded. Genentech, part of the Roche Group, revealed impressive topline results from its Phase 2 study on CT-388, a once-weekly injectable dual GLP-1/GIP receptor agonist being developed for obesity and type 2 diabetes. The news signals that Roche’s acquisition of Carmot Therapeutics in January 2024 is already bearing fruit with this advanced asset.

CT-388 Study Delivers Robust Clinical Trial Data

In the CT388-103 study, patients receiving 24 mg doses demonstrated placebo-adjusted weight loss of 22.5% at 48 weeks—without hitting a plateau, suggesting potential for even greater outcomes. The study findings paint a compelling picture: 95.7% of participants achieved at least 5% weight loss, 87% dropped 10% or more, and 26.1% surpassed the 30% mark. Most impressively, 47.8% crossed the meaningful 20% weight loss threshold.

Beyond simple weight reduction, the trial showed dramatic metabolic improvements. Among the 24 mg cohort, 54% achieved obesity resolution (BMI below 30), compared to just 13% in the placebo group. For participants with pre-diabetes at baseline, 73% normalized their blood glucose—a striking contrast to the 7.5% improvement in controls.

Safety News from the Phase 2 Investigation Shows Well-Tolerated Profile

The study results come with reassuring safety data. Gastrointestinal side effects remained mild to moderate, consistent with GLP-1/GIP drugs as a class. Critically, discontinuation due to adverse events was minimal: 5.9% in the CT-388 arms versus 1.3% in placebo. This tolerability profile strengthens CT-388’s competitive positioning within the growing obesity treatment class.

Why This Study Matters: The Broader Context

As obesity becomes recognized as the leading single risk factor for chronic disease, the market urgently needs effective solutions. Projections suggest over 4 billion people—more than half of Earth’s population—will be living with excess weight or obesity by 2035. Current GLP-1 drugs have captured significant attention, but the dual GLP-1/GIP mechanism offers potentially superior outcomes, as this latest study demonstrates.

Phase 3 Expansion and Future Development Timeline

The weight loss study success accelerates Roche’s clinical roadmap. A separate Phase 2 investigation (CT388-104) is underway for overweight and obese patients with type 2 diabetes. Most significantly, the company plans to launch its Phase 3 program—codenamed Enith1 and Enith2—in early 2026, setting up a critical phase in confirming whether these study findings translate to larger populations.

“The robust weight loss combined with a well-tolerated safety profile reinforces our confidence in the clinical development program as we advance to Phase III trials,” said Levi Garraway, Roche’s chief medical officer and head of Global Product Development.

Roche’s stock (RHHBY) currently trades near $56.12 after gaining 1.61% on the latest trading session. The full trial data will be presented at an upcoming medical congress, giving the investment community additional context on this potentially transformative weight loss study and its implications for the obesity treatment market.