Atrogi announces positive human data for ATR-258, its first-in-class, oral therapy designed to improve muscle function and body composition

• In the 8-week study, ATR-258 was well-tolerated and associated with an approximately 13% mean improvement in lower extremity muscle power in combination with a beneficial effect on body composition, with an increase in lean muscle mass and a reduction in fat mass
• Data provide first human proof-of-mechanism and support Atrogi’s planned Phase 2 trial expected to initiate in 2027

STOCKHOLM, Sweden, Oct. 01, 2026 (GLOBE NEWSWIRE) -- Atrogi AB, a clinical-stage biotech company pioneering novel GPCR pathway-signalling modulators to transform metabolic and muscle health, today announces positive data from a human trial for its lead candidate ATR-258, a first-in-class small molecule oral GRK2-biased β2-adrenergic modulator.

ATR-258 is designed to target skeletal muscle through a novel GRK2-biased signalling mechanism, with the goal of improving body composition by reducing fat mass while increasing muscle mass and, most importantly, muscle function. The 8-week, investigator-initiated, open-label, single-arm study (NCT07421024), led by Professor Morten Hostrup, a leading authority on β2-adrenergic receptor pharmacology and physiology in humans, examined the effects of ATR-258 in 13 overweight or obese subjects.

ATR-258 was well tolerated across three ascending dose levels. Treatment was associated with an approximately 13% improvement in lower-extremity muscle power from baseline, as well as statistically significant mean reductions of 1.1 kg in fat mass and increases of 0.8 kg in lean mass. This unique profile offers the potential to address metabolic and muscle-related diseases with high unmet need and a lack of effective treatments.

The rise of incretin-based weight-loss medicines has sharpened the focus on preserving muscle, with studies suggesting that 25–45% of weight lost may be lean mass. Alongside ageing populations and muscle-wasting diseases, this highlights the need for new approaches that support both muscle mass and function, which are critical to mobility, metabolic health and physical resilience. ATR-258 is designed to address this challenge by selectively engaging a pathway in skeletal muscle that drives an enhancement in power, initially in muscle-sparing weight loss.

Professor Tore Bengtsson, Chief Scientific Officer and Founder of Atrogi, said: “These first clinical data give us important confidence that our approach is translating. To see fat loss alongside an increase in lean muscle mass and improvement in muscle function represents a truly differentiated profile, and is highly encouraging. We are immensely proud and thankful to the investigators of this trial, which represents an important milestone in Atrogi's journey. Beyond muscle-sparing weight loss, we believe this mechanism also warrants investigation in sarcopenia and rare diseases marked by substantial muscle loss and weakness.”

The findings build on the landmark study published in Cell in June 2025, which established Atrogi’s GRK2-biased signaling approach and detailed first-in-human data from a 69-subject Phase 1 trial evaluating the safety and tolerability of ATR-258 in healthy volunteers and patients with type 2 diabetes.

The new results provide first human proof-of-mechanism and support Atrogi’s plans to initiate a Phase 2 trial in 2027, designed to demonstrate clinical proof-of-concept in muscle-sparing weight loss and sarcopenia.

Morten Hostrup, Professor and Principal Investigator of the study, commented: “As a researcher who has long studied β2-adrenergic receptor signalling in skeletal muscle, I was curious whether a biased, highly selective GRK2 modulator could harness this pathway differently – driving beneficial changes in muscle mass and function without the trade-offs seen with classical β2-agonists. What struck me most was the magnitude of the signal in lower-extremity power. Having worked extensively with classical β2-agonists, I know they can enhance power, but not to the extent we observed here. These findings give us a genuinely intriguing signal about the role of GRK2-biased signalling in muscle physiology, and a strong rationale for taking ATR-258 forward into larger clinical trials.”

Paul Little, Chief Executive Officer at Atrogi, added: “These results are a major step forward for Atrogi and we thank everyone involved. We are a Phase 2-ready biotech with a first-in-class, next-generation oral GRK2-biased β2-adrenergic modulator. We now have human data pointing to a unique profile in metabolic health in a broad context where muscle becomes medicine, and look forward to evaluating that profile in a Phase 2 trial, which we anticipate initiating in 2027.”

Morten Hostrup has been invited to present initial findings from the study at the International Conference on Cachexia, Sarcopenia and Muscle Wasting in Washington, DC, USA, on 10–12 December 2026.

For further information, please contact:

Atrogi AB
Paul Little, CEO
info@atrogi.com

Optimum Strategic Communications
Mary Clark, Isabelle Abdou, Joshua Evans, Katherine Bliss
+44 20 3357 0618
atrogi@optimumcomms.com

Notes to Editors

About Atrogi

Atrogi AB is a Stockholm-based, clinical-stage biotech pioneering novel GPCR pathway-signaling modulators to transform metabolic and muscle health. Its lead candidate, ATR-258, is a first-in-class oral GRK2-biased β2-agonist designed to safely stimulate muscle metabolism and preserve lean mass, offering a unique profile in muscle sparing weight loss, sarcopenia and diseases characterised by muscle loss. Atrogi’s proprietary compound library, developed under the scientific leadership of Professor Tore Bengtsson, serves as the foundation for a broader platform aimed at discovering selective GPCR modulators across multiple disease areas. Learn more at www.atrogi.com and on LinkedIn.