Positive Phase II results for Genentech’s dual GLP-1/GIP CT-388 for obesity

Genentech announced positive topline results from CT388-103, a Phase II clinical trial of CT-388, an investigational dual GLP-1/GIP receptor agonist being developed for the treatment of obesity. The study found that once-weekly subcutaneous injections of CT-388 (titrated up to 24 mg) resulted in significant and clinically meaningful placebo-adjusted weight loss of 22.5% (efficacy estimand) without reaching a weight loss plateau at 48 weeks.

CT-388 aims to reduce appetite and regulate blood sugar by selectively targeting and activating both receptors which integrate nutrient-derived signals to control energy homeostasis. CT-388 was designed to have potent activation of both GLP-1 and GIP receptors, but with minimal to no ß-arrestin recruitment on either receptor. This biased signalling significantly minimises receptor internalization and consequent desensitisation, which is expected to lead to prolonged pharmacological activity.

The multi-centre, randomised, double-blind, placebo-controlled, parallel group dose-finding Phase II trial was designed to evaluate the efficacy and safety of CT-388 at low, middle, and high doses in 469 people with obesity. It includes adults with obesity (BMI≥30.0 kg/m2) or overweight (BMI ≥27.0 and <30.0 kg/m2) with at least one weight-related comorbidity without type 2 diabetes and evaluated five dosing cohorts with different up-titration schemes with 24 mg being the highest dose tested. The primary endpoint was percent change in body weight from baseline to week 48.

The outcomes from the trial demonstrated a clear dose-response relationship on the weight loss was observed. For the treatment-regimen estimand, the placebo-adjusted weight loss achieved with CT-388 was 18.3% (p<0.001). At week 48 for the 24 mg dose, 95.7% of CT-388 treated participants achieved a weight loss of ≥5%, 87% achieved ≥10%, 47.8% achieved ≥20%, and 26.1% achieved ≥30%. 73% of participants who were pre-diabetic at baseline and treated with CT-388 at 24 mg achieved normal blood glucose levels at week 48 compared to 7.5% in the placebo group.

The treatment was well-tolerated, with the majority of gastrointestinal-related adverse events being mild-to-moderate, generally consistent with the incretin class of medicines. In addition, the treatment discontinuation rate due to adverse events was low (5.9% in CT-388 arms; 1.3% in placebo arm). The full results of the study will be presented at an upcoming medical congress.

CT-388 is currently being investigated in an additional Phase II study (CT388-104) to evaluate the efficacy, safety and tolerability of CT-388 in participants who are living with obesity or are overweight and have type 2 diabetes. The Phase III clinical trial programme of CT-388 in obesity (Enith1 and Enith2) is expected to start in this quarter. In addition to offering robust efficacy as a standalone therapy, CT-388 also plays a key role in unlocking the promise of our obesity pipeline and is considered as a combination asset for petrelintide.