The TRIUMPH Phase 3 Program: Everything We Know

What Is the TRIUMPH Program?

TRIUMPH is Eli Lilly’s comprehensive Phase 3 clinical development program for retatrutide (LY3437943). Named as an acronym reflecting its therapeutic ambitions, the program comprises multiple pivotal trials designed to evaluate retatrutide across several metabolic indications. The program was initiated following the striking Phase 2 results published in the New England Journal of Medicine, which demonstrated up to 24.2% mean body weight reduction at 48 weeks and significant liver fat reduction.

The TRIUMPH program represents one of the largest Phase 3 efforts in metabolic medicine, with trials spanning obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD). Collectively, the program is expected to enroll thousands of participants across global sites.

Individual Trials Within TRIUMPH

The program includes several distinct trials, each targeting a specific patient population and indication:

TRIUMPH-1 focuses on adults with obesity or overweight with at least one weight-related comorbidity, without type 2 diabetes. This is the core obesity trial and is expected to be the primary basis for a weight management indication. The trial duration extends to 72 weeks of treatment, addressing one of the Phase 2 limitations where weight loss had not plateaued at 48 weeks.

TRIUMPH-2 enrolls adults with type 2 diabetes and obesity. This trial evaluates both glycemic control (HbA1c reduction) and weight loss, positioning retatrutide as a potential treatment for the large population with co-existing obesity and diabetes.

TRIUMPH-3 is designed to assess the long-term maintenance of weight loss, examining what happens when patients continue or discontinue treatment after an initial weight loss phase. This addresses a critical clinical question: how durable are the effects?

TRIUMPH-4 targets MASLD (formerly NAFLD), leveraging the remarkable liver fat reduction observed in Phase 2. This trial could support what would be among the first approved pharmacotherapies specifically for metabolic liver disease.

Additional trials within the program may address cardiovascular outcomes and other metabolic endpoints, though details on some components remain limited in the public domain.

Enrollment and Study Design

Across the TRIUMPH program, Eli Lilly is enrolling participants at sites in North America, Europe, Asia, and other regions. This global scope addresses a key limitation of the Phase 2 trial, which was conducted exclusively at U.S. sites. Total enrollment across all TRIUMPH trials is expected to exceed 10,000 participants.

The pivotal obesity and diabetes trials use randomized, double-blind, placebo-controlled designs with dose escalation protocols informed by Phase 2 tolerability data. The escalation approach — starting at lower doses and gradually increasing — was shown in Phase 2 to improve tolerability and reduce gastrointestinal adverse events compared to fixed-dose initiation.

Primary Endpoints

Each trial has endpoints aligned with its target indication:

• Obesity trials: Percent change in body weight from baseline and the proportion of participants achieving ≥5%, ≥10%, and ≥15% weight loss thresholds at 72 weeks
• Diabetes trials: Change in HbA1c from baseline, with weight loss and other glycemic parameters as key secondary endpoints
• MASLD trial: Change in hepatic fat content measured by MRI-PDFF, with histological endpoints (liver biopsy) in a subset of participants

Expected Timelines

Phase 3 trials of this scale typically take 2-3 years from first patient enrollment to primary data readout. Based on publicly available information from Eli Lilly and clinical trial registries, the earliest primary data readouts from TRIUMPH are anticipated in late 2025 to mid-2026. The staggered initiation of different trials means data will likely emerge sequentially rather than all at once.

If Phase 3 results are positive, Eli Lilly would then compile a New Drug Application (NDA) for FDA submission, with parallel regulatory filings expected in the EU, Japan, and other markets. The interval between Phase 3 data readout and NDA submission is typically 6-12 months, followed by a 10-12 month FDA review period.

What This Means for Approval

The TRIUMPH program is designed to support multiple regulatory submissions. The obesity indication is likely to be the first pursued, given the robust Phase 2 weight loss signal and the commercial precedent set by semaglutide and tirzepatide in this space. A diabetes indication could follow closely behind or be submitted concurrently.

The MASLD indication represents a potentially transformative opportunity. With very few approved therapies for metabolic liver disease and a global prevalence exceeding 25% of adults, a successful TRIUMPH-4 trial could establish retatrutide in a largely unaddressed therapeutic area.

Perspective

The TRIUMPH program is ambitious in scope and carries the high expectations set by Phase 2 data. However, it is important to note that Phase 3 confirmation is never guaranteed. Effect sizes can attenuate in larger, more diverse populations, and safety signals may emerge with longer exposure and greater enrollment. The metabolic medicine field has seen promising Phase 2 candidates fail to confirm in Phase 3.

That said, the magnitude of the Phase 2 signal — particularly the weight loss and liver fat data — provides a substantial margin. Even if Phase 3 results show some attenuation relative to Phase 2, the clinical effect could still be highly meaningful. The coming years will determine whether TRIUMPH fulfills its name.