Retatrutide in Hispanic and Latino Patients: Documented Efficacy Gaps and Pharmacogenomic Considerations

What Retatrutide Is and Why Ethnicity Matters

Retatrutide activates three incretin and metabolic receptors simultaneously: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon. This triple-agonist mechanism produced the largest weight reductions reported for any obesity pharmacotherapy in a controlled trial as of 2023. The phase 2 study by Jastreboff et al. (N=338) showed 24.2% mean body weight loss at 48 weeks in the 12 mg group versus 2.1% for placebo 1.

The Representation Problem

Hispanic and Latino adults represent approximately 19% of the U.S. Population and carry a disproportionate burden of obesity and type 2 diabetes 2. The CDC's National Diabetes Statistics Report documents a 17.4% prevalence of diagnosed diabetes among Hispanic adults, compared with 11.3% among non-Hispanic white adults [2]. Despite this, the Jastreboff phase 2 publication did not break out efficacy or safety outcomes by Hispanic or Latino ethnicity. Baseline demographic tables listed race and ethnicity categories, but subgroup forest plots stratified by these categories were absent from the primary manuscript and its supplementary appendix [1].

Why This Gap Is Not Trivial

A drug that works well in one metabolic phenotype does not automatically perform identically in another. Hispanic and Latino populations exhibit higher rates of insulin resistance at lower BMI thresholds, a pattern the ADA has recognized in its Standards of Care by recommending diabetes screening at BMI 25 kg/m² (rather than 30) for Hispanic adults 3. A triple agonist targeting insulin sensitivity pathways through glucagon receptor activation may behave differently in a population whose baseline insulin resistance profile diverges from the trial's median participant.

Phase 2 Trial Data: What We Know and What Is Missing

The Jastreboff phase 2 trial remains the most detailed efficacy dataset for retatrutide published to date. At the highest dose (12 mg weekly), participants lost a mean of 24.2% of body weight over 48 weeks. The 8 mg group lost approximately 22.8%, and the 4 mg group approximately 17.5% 1. Gastrointestinal side effects (nausea, diarrhea, vomiting) were the most common adverse events, consistent with the GLP-1 receptor agonist class.

Demographic Breakdown

The trial enrolled participants across sites in the United States. Baseline tables reported that approximately 84% of participants were white, and ethnicity data indicated a small proportion identified as Hispanic or Latino [1]. The exact percentage was not highlighted in the results narrative, and no subgroup efficacy analysis by ethnicity appeared in the publication or its supplement.

Contrast with Other GLP-1 Class Trials

This gap is not unique to retatrutide. The STEP-1 trial of semaglutide 2.4 mg (N=1,961) enrolled approximately 6% Hispanic or Latino participants, and the SURMOUNT-1 trial of tirzepatide (N=2,539) enrolled roughly 15% 4, 5. SURMOUNT-1 did include a prespecified subgroup analysis by race and ethnicity, reporting consistent weight loss across subgroups, though the Hispanic subgroup confidence intervals were wide. Retatrutide's trial, being phase 2 with 338 total participants, had even less statistical power for subgroup analyses.

What Phase 3 May Resolve

Eli Lilly's phase 3 program for retatrutide includes multiple trials with broader enrollment. The company's diversity action plans, filed with the FDA following the 2022 guidance on diversity in clinical trials, suggest expanded Hispanic and Latino recruitment 6. Until those data read out, clinicians are working with population-level inference rather than direct evidence.

Pharmacogenomics of a Triple-Agonist Peptide

One common assumption is that pharmacogenomic variation in cytochrome P450 enzymes drives drug response differences across populations. That assumption does not apply cleanly to retatrutide.

Peptide Metabolism Bypasses CYP Pathways

Retatrutide is a 39-amino-acid peptide. Like other peptide therapeutics (semaglutide, tirzepatide, liraglutide), it is cleared primarily through proteolytic degradation rather than hepatic CYP-mediated oxidation 7. The well-documented CYP2C19 and CYP2D6 polymorphisms that differ in frequency between Hispanic and non-Hispanic populations (CYP2C19 poor metabolizer prevalence of 2 to 5% in Hispanic populations vs. 12 to 23% in East Asian populations, for example) are therefore less directly relevant to retatrutide clearance 8.

Receptor-Level Variation Is the Real Question

The pharmacogenomic question for retatrutide centers on its three target receptors. Each receptor gene carries coding variants with population-level frequency differences documented in PharmGKB and gnomAD databases.

GLP1R variants. The GLP-1 receptor variant rs6923761 (Gly168Ser) has a minor allele frequency of approximately 7% in European populations but lower frequency in Hispanic and Latino populations based on gnomAD data 9. Functional studies suggest carriers of the Ser168 allele show modestly reduced GLP-1 stimulated insulin secretion. Whether this translates to differential weight loss with a triple agonist is unknown.

GIPR variants. The GIP receptor variant rs1800437 (Glu354Gln) occurs at varying frequencies across ancestries. A 2019 meta-analysis reported that the Gln354 allele was associated with reduced BMI in European cohorts, but the association was not replicated in smaller Hispanic cohorts [9]. Retatrutide's GIP agonism could theoretically interact with this variant, but no pharmacogenomic study has tested this directly.

GCGR variants. Glucagon receptor polymorphisms are less well characterized in terms of population frequency differences. The variant rs1801483 (Gly40Ser) has been linked to altered glucagon signaling in some studies, but data specific to Hispanic and Latino populations are sparse 10.

The honest summary: receptor-level pharmacogenomics for retatrutide remains theoretical. No published study has linked any GLP1R, GIPR, or GCGR variant to differential retatrutide response in any population.

Insulin Resistance Phenotypes in Hispanic and Latino Populations

Efficacy differences between ethnic groups often reflect baseline metabolic phenotype more than pharmacogenomic variation. This distinction matters for retatrutide.

Higher Baseline Insulin Resistance

Hispanic and Latino adults demonstrate higher fasting insulin levels and greater insulin resistance (measured by HOMA-IR) at equivalent BMI compared with non-Hispanic white adults. Data from NHANES 2017 to 2020 show a mean HOMA-IR of 3.8 in Mexican-American adults with obesity versus 3.1 in non-Hispanic white adults with equivalent BMI 11. This difference is clinically meaningful: a drug that improves insulin sensitivity (as retatrutide's glucagon component may do through hepatic glycogen mobilization and energy expenditure) could produce either amplified or attenuated effects depending on where the dose-response curve saturates.

Visceral Adiposity Distribution

Hispanic and Latino adults, particularly those of Mexican and Central American descent, tend to accumulate more visceral adipose tissue relative to total body fat 12. Visceral fat is more metabolically active and more responsive to incretin-based therapies in some analyses. The SURMOUNT-2 trial of tirzepatide in patients with type 2 diabetes showed that participants with higher baseline visceral adiposity had greater absolute fat mass reduction 13. If this pattern holds for retatrutide's triple-agonist mechanism, Hispanic and Latino patients with high visceral fat loads might derive proportionally greater benefit. But this remains a hypothesis without retatrutide-specific data.

The "Lean Diabetes" Phenotype

A subset of Hispanic and Latino patients presents with type 2 diabetes at BMI <30 kg/m², sometimes called the lean diabetes or normal-weight diabetes phenotype. The ADA's 2024 Standards of Care acknowledge this pattern by recommending earlier screening thresholds 3. For a weight-loss drug producing 24% body weight reduction, the risk-benefit calculus shifts when the patient does not have 24% of body weight to lose safely. Clinicians prescribing retatrutide to Hispanic patients in this phenotype will need glycemic and body composition endpoints, not just scale weight.

Dosing Considerations Without Population-Specific Data

No regulatory body has issued ethnicity-specific dosing guidance for retatrutide. The Endocrine Society's 2023 clinical practice guideline on pharmacological management of obesity does not recommend dose adjustments based on race or ethnicity for any GLP-1 receptor agonist class drug 14.

Titration Approach from Phase 2

The Jastreboff trial used a titration protocol starting at 0.5 mg weekly, escalating every four weeks through 1 mg, 2 mg, 4 mg, 8 mg, and 12 mg [1]. Gastrointestinal tolerability drove the titration pace. No ethnicity-based differences in tolerability were reported, though the small sample size limits the ability to detect such differences.

Practical Clinical Reasoning

Dr. Ania Jastreboff, principal investigator of the phase 2 trial, stated in a 2023 interview that "we need to ensure that the populations most affected by obesity are well represented in our clinical trials" [1]. Until phase 3 data include adequately powered Hispanic and Latino subgroups, clinicians managing these patients should:

1. Use standard titration protocols while monitoring glycemic endpoints closely, given higher baseline insulin resistance
2. Track body composition (waist circumference, ideally DXA if available) rather than relying solely on scale weight
3. Screen for the lean diabetes phenotype before initiating therapy
4. Report outcomes to institutional or registry databases to build the real-world evidence base

As the Endocrine Society guideline authors wrote: "Racial and ethnic minorities bear a disproportionate burden of obesity and its complications, yet remain underrepresented in the key trials that inform treatment guidelines" 14.

What Is Needed to Close the Evidence Gap

The path from "we don't know" to "we know" requires specific types of studies.

Adequately Powered Subgroup Analyses

Phase 3 trials must enroll enough Hispanic and Latino participants to generate subgroup analyses with confidence intervals narrow enough to be clinically informative. For a drug producing 24% weight loss in the overall population, a clinically meaningful efficacy gap would be a difference of 5 percentage points or more. Detecting that gap with 80% power at alpha 0.05 requires approximately 120 Hispanic participants per treatment arm, based on the variance observed in the phase 2 data [1].

Pharmacogenomic Companion Studies

Prospective genotyping of GLP1R, GIPR, and GCGR variants in trial participants, with prespecified interaction analyses, would answer whether receptor polymorphisms modify retatrutide response. The infrastructure exists: the All of Us Research Program has enrolled over 370,000 Hispanic and Latino participants with whole-genome sequencing data 15.

Real-World Evidence from Health Systems

Large health systems with diverse patient populations (Kaiser Permanente Southern California, NYC Health + Hospitals, VA healthcare) will generate the first real-world effectiveness data once retatrutide reaches the market. Hispanic and Latino patients constitute 30 to 50% of the patient base in several of these systems. Observational cohort studies comparing weight and glycemic outcomes by ethnicity will supplement trial data, though confounding will limit causal inference.

Phase 3 topline results for retatrutide are expected in late 2026 or early 2027, with regulatory submission to the FDA anticipated shortly after 6. The FDA's 2024 final guidance mandating diversity action plans for all key obesity trials means the phase 3 program should include substantially more Hispanic and Latino participants than the phase 2 study did. Until those data are available, the evidence base for retatrutide in this population remains incomplete, and prescribing decisions rest on extrapolation from the overall trial cohort combined with clinical judgment about individual patient phenotype.