STOCKHOLM, Sweden — October 1, 2026
Atrogi AB announced positive human data for ATR-258, an investigational first-in-class oral small-molecule GRK2-biased β2-adrenergic modulator designed to improve muscle function and body composition. In an 8-week investigator-initiated, open-label, single-arm study, 13 overweight or obese participants received ATR-258 across three ascending dose levels. Treatment was associated with an approximately 13% improvement in lower-extremity muscle power, a statistically significant mean reduction of 1.1 kg in fat mass and an increase of 0.8 kg in lean mass. ATR-258 was reported to be well tolerated across the evaluated dose levels, providing initial human proof-of-mechanism for Atrogi’s approach.
ATR-258 Shows Changes in Muscle Power and Body Composition
The Phase 1 study evaluated whether selective GRK2-biased β2-adrenergic signaling could produce changes in muscle function and body composition. Following eight weeks of treatment, participants demonstrated an approximately 13% improvement in lower-extremity muscle power from baseline. The study also showed reductions in fat mass together with increases in lean mass, a profile Atrogi is developing around the concept of muscle-sparing weight loss. The company said the findings could have relevance beyond obesity, including potential applications in sarcopenia and diseases associated with substantial muscle loss and weakness. The small, single-arm study is an early proof-of-mechanism evaluation, and larger controlled studies will be needed to establish the durability and clinical significance of these findings.
ATR-258 Uses GRK2-Biased β2-Adrenergic Signaling
ATR-258 is designed to selectively modulate β2-adrenergic receptor signaling through a GRK2-biased mechanism in skeletal muscle. Atrogi’s approach is intended to enhance muscle power while supporting changes in body composition without relying on the broader effects associated with classical β2-adrenergic agonists. The new clinical findings build on a June 2025 Cell publication describing the company’s GRK2-biased signaling approach and earlier first-in-human safety and tolerability data from a 69-subject Phase 1 study involving healthy volunteers and patients with type 2 diabetes. The company believes the new results provide initial clinical evidence that its mechanism can translate into measurable effects on human muscle physiology.
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Atrogi Plans Phase 2 Development in 2027
Atrogi plans to advance ATR-258 into a Phase 2 clinical trial in 2027 to evaluate clinical proof-of-concept in muscle-sparing weight loss and sarcopenia. The development strategy reflects growing interest in preserving muscle mass and function during weight reduction, particularly as incretin-based therapies have increased attention on body-composition changes associated with weight loss. Atrogi is also exploring the potential of ATR-258 in muscle-wasting conditions and rare diseases characterized by muscle weakness. Initial findings from the 8-week study are scheduled for presentation at the International Conference on Cachexia, Sarcopenia and Muscle Wasting in Washington, D.C., December 10–12, 2026.
Source: Atrogi press release
