Phase 1 Study in Japanese Subjects (NCT06003465)

Study Overview

This Phase 1 study was designed to evaluate the safety, tolerability, and pharmacokinetics of retatrutide in Japanese adults with overweight or obesity. Bridging studies in Japanese populations are a regulatory requirement for the Pharmaceuticals and Medical Devices Agency (PMDA) in Japan, as pharmacokinetic parameters and tolerability can differ across ethnic groups.

Study Design

Design

Randomized, double-blind, placebo-controlled, single and multiple ascending dose trial.

Population

Japanese adults aged 18-65 years with BMI ≥25 kg/m² (using the Japanese obesity threshold, which is lower than the Western threshold of 30 kg/m²).

Objectives

1. Characterize the pharmacokinetic profile of retatrutide in Japanese subjects
2. Assess safety and tolerability at escalating doses
3. Compare PK parameters with data from Western populations
4. Support the regulatory pathway for approval in Japan

Significance

This study is part of Eli Lilly’s global development strategy for retatrutide. Japan represents one of the largest pharmaceutical markets globally, and the PMDA requires ethnic bridging data before approving drugs that were primarily developed in Western populations. The study results will determine whether dose adjustments are necessary for Japanese patients.

Regulatory Context

Japan has its own obesity treatment guidelines and lower BMI thresholds for defining obesity (BMI ≥25 vs. ≥30 in Western guidelines). The results of this study, combined with the global Phase 3 program data, will be included in the Japanese regulatory submission package.