Obesity continues to be one of the most serious public health challenges worldwide, driving increased risks of diabetes, heart disease, and reduced quality of life. As researchers search for more effective medical solutions, a new investigational therapy from Genentech is gaining significant attention. In January 2026, Genentech announced positive Phase II clinical trial results for CT-388, a dual GLP-1 and GIP receptor agonist developed for the treatment of obesity.
The findings suggest that CT-388 could become a powerful new option in the growing class of incretin-based weight loss therapies. With substantial weight reduction, improvements in blood sugar control, and a favorable safety profile, CT-388 represents a potentially important advancement in obesity medicine.
This article explores the Phase II results, how CT-388 works, its clinical significance, and what it could mean for the future of obesity treatment.
Obesity is widely recognized as the single greatest risk factor for chronic disease worldwide. According to global projections, more than four billion people are expected to be living with excess weight or obesity by 2035. This trend affects nearly every country and is driven by a complex combination of genetic, biological, behavioral, environmental, and socioeconomic factors.
The growing prevalence of obesity places immense pressure on healthcare systems due to the rising burden of associated conditions such as type 2 diabetes, cardiovascular disease, fatty liver disease, sleep apnea, and joint disorders. Effective and sustainable medical therapies are urgently needed to complement lifestyle changes and surgical interventions.
CT-388 is an investigational, once-weekly injectable medication developed by Genentech, a member of the Roche Group. It is classified as a dual GLP-1 and GIP receptor agonist, meaning it activates two key hormone receptors involved in appetite regulation, blood sugar control, and energy balance.
GLP-1 receptor agonists are already well known for their role in weight loss and diabetes management. GIP receptor activation adds another layer of metabolic control. CT-388 is designed to selectively activate both receptors while minimizing beta arrestin recruitment, a mechanism that can lead to receptor internalization and reduced drug effectiveness over time.
This biased signaling approach is intended to prolong the medication’s activity, potentially leading to sustained weight loss without an early plateau.
The CT388-103 study was a multi-center, randomized, double-blind, placebo-controlled Phase II clinical trial. It enrolled 469 adults living with obesity or overweight with at least one weight-related comorbidity, excluding type 2 diabetes.
Key eligibility criteria included:
Participants were assigned to one of five dosing cohorts, with different dose escalation schedules. The highest dose evaluated was 24 mg administered once weekly via subcutaneous injection.
The primary endpoint of the study was the percentage change in body weight from baseline to week 48.
The topline results from the trial demonstrated significant and clinically meaningful weight loss with CT-388.
Participants receiving the highest dose of 24 mg achieved a placebo-adjusted weight loss of 22.5 percent using the efficacy estimand. Importantly, the data showed no evidence of a weight loss plateau at 48 weeks, suggesting that continued treatment could lead to sustained or additional benefits.
Using the treatment-regimen estimand, placebo-adjusted weight loss was 18.3 percent, with a p-value of less than 0.001, indicating strong statistical significance.
A clear dose-response relationship was observed, meaning higher doses led to greater weight loss outcomes.
At week 48, participants treated with CT-388 at the 24 mg dose achieved the following milestones:
These results are particularly notable because even a 5 to 10 percent reduction in body weight is associated with meaningful improvements in metabolic health, cardiovascular risk factors, and overall quality of life.
Beyond weight loss, CT-388 demonstrated strong metabolic benefits. Among participants who were classified as prediabetic at baseline, 73 percent achieved normal blood glucose levels by week 48 when treated with the 24 mg dose.
In comparison, only 7.5 percent of participants in the placebo group reached normal glucose levels during the same timeframe. This finding highlights CT-388’s potential role in preventing progression to type 2 diabetes.
Genentech is currently evaluating CT-388 in an additional Phase II study involving individuals with obesity or overweight who also have type 2 diabetes.
Safety is a critical consideration for any long-term obesity treatment. CT-388 was generally well tolerated in the Phase II trial.
The most commonly reported adverse events were gastrointestinal in nature, including symptoms such as nausea and diarrhea. These events were mostly mild to moderate in severity and consistent with the known side effect profile of incretin-based therapies.
Treatment discontinuation due to adverse events was low:
These findings suggest that CT-388 may offer strong efficacy without compromising tolerability.
Levi Garraway, MD, PhD, Chief Medical Officer and Head of Global Product Development at Genentech, expressed confidence in the results.
He noted that the robust weight loss combined with a favorable safety profile reinforces confidence in the CT-388 clinical development program as it advances toward Phase III trials.
Genentech has designated CT-388 as a fast-track asset and has accelerated its development timeline with the goal of bringing the therapy to patients as quickly as possible.
The Phase III clinical trial program for CT-388 in obesity, known as Enith1 and Enith2, is expected to begin this quarter. These large-scale studies will further evaluate long-term efficacy, safety, and real-world applicability.
In addition to its potential as a standalone therapy, CT-388 is also being explored as a combination asset within Genentech’s broader obesity pipeline, including potential combination use with petrelintide.
If Phase III results confirm the Phase II findings, CT-388 could emerge as a next-generation obesity treatment with durable weight loss and metabolic benefits.
The obesity treatment landscape has evolved rapidly in recent years, particularly with the success of GLP-1 based medications. CT-388 builds on this foundation by targeting both GLP-1 and GIP receptors while addressing challenges such as receptor desensitization and weight loss plateaus.
Its ability to deliver sustained weight reduction, normalize blood glucose in prediabetic patients, and maintain tolerability positions it as a potentially transformative therapy.
As obesity continues to rise globally, innovations like CT-388 are critical to reducing the long-term health and economic burden associated with excess weight.
The positive Phase II results for CT-388 represent an important milestone in obesity drug development. With substantial weight loss, metabolic improvements, and a manageable safety profile, CT-388 has the potential to redefine standards of care for people living with obesity.
As Genentech advances this therapy into Phase III trials, the medical community will be watching closely. If future studies confirm these promising results, CT-388 could become a valuable tool in addressing one of the most pressing health challenges of our time.
Genentech Announces Positive Phase II Results for CT-388 in People Living With Obesity. Published January 26, 2026.
This article is for informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before starting or changing any medical therapy. Clinical trial data described here relate to investigational treatments that are not yet approved for general use.
Most Accurate Healthcare AI designed for everything from admin workflows to clinical decision support.