Targeting Visceral Fat with RNA Therapeutics

Episode Summary

Executive Summary: This episode examines a next-generation obesity strategy from Wave Life Sciences that aims to selectively reduce harmful visceral fat while preserving muscle. Eric Inglson argues that weight-loss success should be measured by body composition and cardiometabolic risk reduction, not scale weight alone. He explains the Activin E biology, supporting genetic and early clinical data, and outlines potential roles in monotherapy, combination with GLP-1s, and maintenance after GLP-1 treatment.

Main Topics: Rethinking obesity endpoints beyond scale weight (Priority: 5/5): Inglson argues that total weight loss is an incomplete and sometimes misleading endpoint because effective treatment should prioritize reducing excess fat—especially visceral fat—while preserving muscle. Visceral fat versus subcutaneous fat (Priority: 5/5): The discussion distinguishes harmful visceral fat around internal organs from the largely benign subcutaneous fat under the skin, emphasizing visceral fat as the key driver of cardiometabolic disease. Limitations of GLP-1/incretin therapies (Priority: 4/5): GLP-1 drugs are transformative but can cause muscle loss, GI side effects, and discontinuation, motivating interest in alternative or complementary mechanisms. Activin E biology and RNA-based targeting (Priority: 5/5): Wave’s approach lowers liver-produced Activin E using RNA therapeutics, removing a natural brake on lipolysis to promote direct fat breakdown in fat cells. Clinical evidence and phase one results (Priority: 5/5): Early human data showed durable suppression of Activin E and meaningful visceral fat reduction after a single dose, supporting the program’s translational rationale. Future development: monotherapy, combination, maintenance (Priority: 4/5): The company sees use cases for older or sarcopenia-prone patients, combination with GLP-1s, and an off-ramp/maintenance strategy after incretin treatment. Regulatory and commercial positioning (Priority: 3/5): Wave plans to pursue traditional weight-loss endpoints while also exploring metabolic endpoints such as HbA1c, lipid levels, and liver fat for broader value demonstration.

Key Arguments: Obesity treatment should be judged by reduction in harmful visceral fat, not only by total scale weight, because muscle loss worsens function, metabolism, and weight-regain risk. GLP-1 therapies reduce appetite and body weight, but up to 40% of weight loss may come from muscle, and GI side effects plus weekly dosing contribute to high discontinuation. Visceral fat is the metabolically dangerous fat linked to type 2 diabetes, cardiovascular disease, and MASH; even 5-10% reductions can meaningfully improve risk. Loss-of-function human genetics for Activin E provides strong validation that lowering this pathway can improve waist-to-hip ratio, lipids, glucose, liver markers, and disease risk. RNA therapeutics are well suited here because they can precisely target the mechanism, potentially improving specificity, tolerability, and dosing convenience. Preclinical data and first-in-human results suggest the mechanism can reduce visceral fat, preserve muscle, and potentially complement or maintain gains after GLP-1 therapy. A differentiated, orthogonal mechanism may stand out in a crowded obesity market dominated by incretin-based approaches.

Data Points: Muscle contribution to incretin-associated weight loss: Up to 40% - Inglson said a substantial share of GLP-1/incretin weight loss can come from muscle, which is undesirable. Share of body fat that is subcutaneous: More than 95% - He contrasted mostly subcutaneous body fat with the smaller but riskier visceral fat fraction. Visceral fat reduction threshold for benefit: 5-10% - He said relatively modest visceral fat reductions can meaningfully improve cardiometabolic risk. Patients who stop incretins within one year: 70% - He cited high discontinuation, driven by GI tolerability and other limitations. Genetic evidence scale: ~500,000 individuals - The Activin E target emerged from a large UK biobank-style genetics study. Weight circumference reduction in phase one: 3% - Single-dose early clinical result after six months. Total fat reduction in phase one: 5% - Observed after a single dose in the lowest-dose cohort. Visceral fat reduction in phase one: 14% - Reported after a single dose in the low-dose cohort at about six months. Activin E suppression durability: Almost 75% suppressed at 7.5 months - Phase one follow-up suggested long-lasting target knockdown supporting infrequent dosing. Potential dosing frequency: Once or at most twice a year - Based on durability of RNA-mediated knockdown. Average BMI in phase one: Around 32 - Participants were relatively modestly obese compared with later planned studies. Visceral fat volume in phase one participants: One liter or less - He noted these subjects had much less visceral fat than typical obesity-trial populations. Typical visceral fat in obesity trials: Around 5 liters - Used as a comparison to contextualize the phase-one result. Phase two target BMI: Over 35, likely 37-38 average - Upcoming study population will be heavier and include comorbidities. Potential market size for sarcopenic obesity: More than 30 million - Estimate for US and Europe combined.

Pivotal Quotes: "We shouldn't focus on scale weight and absolute weight loss. We should really think about decreasing your excess fat, and in particular, the visceral fat that surrounds your organs." — Eric Inglson: Core thesis on redefining obesity-treatment success. "It removes a break on the fat breakdown, or in other words, it increases the fat breakdown directly in fat cells." — Eric Inglson: Explanation of how inhibiting Activin E is intended to work biologically. "Obesity treatment should really be about reducing excess fat, in particular the visceral fat that's the dangerous fat, while retaining your muscle." — Eric Inglson: Closing summary of the desired treatment paradigm.

Implications: If validated, this approach could shift obesity care toward body-composition goals, create a new class of combination or maintenance therapies alongside GLP-1s, and broaden metabolic benefit measurement beyond weight loss alone.