Actimed's PROACT Trial Fully Enrolled: S-Pindolol Tested as a Muscle Shield for Semaglutide Users

Actimed Therapeutics has completed patient recruitment for PROACT, a Phase 2a trial testing whether S-pindolol benzoate (ACM 001.1) can do something no approved weight-loss drug currently does: protect muscle while semaglutide strips away fat, and keep that protection in place after the injections stop. The London-based company announced on September 23, 2026 that the trial enrolled more than 100 adults with obesity, hitting its planned sample size on schedule.

What Happened

PROACT (NCT07101939) is a two-part, randomised, double-blind, placebo-controlled Phase 2a study of S-pindolol benzoate in obese adults. It is the first trial designed to rigorously test a targeted anabolic-catabolic transforming agent — a compound intended to shift weight loss away from muscle and toward fat — both during active semaglutide therapy and after patients discontinue it.

• Part 1: patients receive one of two dose levels of the investigational agent alongside ongoing semaglutide treatment.
• Part 2: patients who have already stopped semaglutide are followed to see what happens to their lean and fat mass.

Primary endpoints track changes in lean and fat mass; secondary endpoints examine muscle mass, heart, and bone composition.

Who Is Affected

• Patients on GLP-1 therapy. Semaglutide drives substantial weight loss, but a meaningful share of the weight lost is lean mass, not fat.
• Patients who stop treatment. Discontinuation often reverses the benefit, and no approved agent currently addresses post-cessation body composition.
• Clinicians. Body composition is becoming a central question in obesity care, not just kilograms on a scale.

Timeline

• June 2025: First patients enrolled in the PROACT programme.
• September 23, 2026: Recruitment completed, with more than 100 patients enrolled on time.
• Second half of 2026: Initial proof-of-concept data expected.

What This Means for Researchers

The trial targets the most persistent criticism of GLP-1 receptor agonists: impressive total weight loss that comes partly at the expense of muscle. S-pindolol previously produced promising Phase 2a proof-of-concept data in cancer cachexia, and PROACT moves the molecule into the obesity setting. A positive readout would validate a combination pattern — a GLP-1 for fat loss paired with a muscle-protective agent — while a flat result would deepen skepticism about beta-adrenergic approaches to muscle preservation. Either way, these will be among the first controlled data to cover both the during-treatment and post-cessation windows.

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Sources

• Regulatory announcements; industry reports.