Weight-centric endpoints, kilograms lost on the scale, no longer answer the question sponsors and regulators are asking about obesity therapies. A recent discussion brought together Professor Mark Petrie of the University of Glasgow, Professor Ildiko Lingvay of UT Southwestern Medical Center, Dr. Elias Ketiar, and Dr. Graham Ellis of Signant Health to examine health-centric endpoints, missing data, and multi-condition trial design in obesity and GLP-1 development.

What You’ll Learn

• Weight loss percentage alone no longer differentiates new obesity therapies. Tolerability and cost of access are now the primary points of differentiation between incretin-based treatments.
• The FDA requires only a five percent body weight reduction to support obesity medication approval. Trial design is shifting toward comorbidity outcomes rather than maximum weight loss.
• Basket trial designs are testing condition-specific sub-studies, such as sleep apnea and knee osteoarthritis, alongside chronic weight management endpoints within the same participant population.
• Rising commercial access to GLP-1 therapies is increasing dropout risk. Panelists discussed open-label extensions and predictive engagement scoring as retention strategies.
• Muscle mass reduction during weight loss is largely adaptive rather than functional, though participants with low baseline muscle mass may need closer monitoring.
• The full recording includes the panel's detailed discussion of six-minute walk test limitations, wearable-based endpoint alternatives, and Signant's participant risk-scoring approach in practice.

Why It Matters Now

When a participant enrolled in an obesity trial’s placebo arm watches someone close to them start an approved GLP-1 therapy outside the study, the incentive to stay enrolled disappears fast. Sponsors lose participants, sites lose visit data, and regulators lose the completeness they need to interpret a trial’s result.

That risk is compounding as commercial access to incretin therapies expands into markets that once served as reliable trial sites, including parts of Brazil and India. The FDA’s 2025 guidance on missing data from study dropouts is not a future consideration. It applies to obesity and metabolic trials enrolling participants today.

What the Discussion Showed

Sponsors have long avoided combining multiple clinical endpoints in a single obesity trial, and the caution is well-founded. Site coordinators already juggle demanding visit schedules. Sample size calculations grow more complex with each additional endpoint, and asking participants to complete extra assessments can undermine adherence.

Recent basket-design studies show that a shared participant population can still generate indication-specific data without materially increasing individual burden. One example, a chronic weight management trial with sleep apnea and knee osteoarthritis sub-studies, was presented at the American Diabetes Association.

Sponsors weighing a single-population, multi-sub-study design for their next obesity or cardiometabolic program can review the panel’s full discussion of trial design tradeoffs, retention data, and endpoint selection criteria in the complete webinar recording.

“The six-minute walk test has become too blunt an instrument for modern cardiometabolic trials. Wearable-based activity measures deserve serious consideration, provided they add no extra burden for participants or sites.”
Professor Mark Petrie, Cardiologist, Glasgow Royal Infirmary. Deputy Editor, European Journal of Heart Failure.