Actimed Therapeutics completes PROACT Phase 2a recruitment

The London biotech has enrolled over 100 patients in a trial testing S-pindolol benzoate to preserve lean mass during and after semaglutide therapy.

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A brightly lit optometry examination room features an ophthalmic testing machine, a beige patient chair, a computer monitor displaying diagnostic graphs, and a small table with magazines, all under natural light from a window.

Actimed Therapeutics has completed patient recruitment for the PROACT study, a two-part Phase 2a randomised, double-blind, placebo-controlled trial evaluating its candidate S-pindolol benzoate (ACM 001.1) in obese adults. More than 100 patients were enrolled, achieving the planned sample size on schedule.

The trial targets what Actimed describes as a clinically significant gap in GLP-1 receptor agonist (GLP-1RA) therapy: the loss of lean body mass (LBM) that accompanies weight loss on drugs such as semaglutide. Concern over muscle loss is particularly acute in older, frail, or comorbid patients, and weight regain after GLP-1RA discontinuation tends to favour fat mass over muscle, worsening the overall muscle-to-fat ratio.

Trial design

PROACT is structured across three arms. The first two use a crossover design in which patients receiving semaglutide are randomised to S-pindolol benzoate (10 mg or 15 mg twice daily) or placebo, to assess whether the compound can preserve LBM during active GLP-1RA-induced weight loss. The third arm uses a parallel-group design: patients complete a 20-week semaglutide course before being re-randomised to S-pindolol benzoate or placebo for a further 20 weeks, evaluating whether the drug can improve lean mass proportion during the weight-regain period after cessation.

Fabio Dorigotti, Actimed's chief medical officer, said the study is "the first to rigorously evaluate a targeted anabolic catabolic transforming agent both during semaglutide therapy and after its discontinuation," adding that the company looks forward to generating data to guide the next stage of development.

S-pindolol benzoate is a salt formulation of S-pindolol, which showed proof-of-concept signals in earlier Phase 2a work in cancer cachexia patients. Actimed has also completed a pharmacokinetic and pharmacodynamic study of the benzoate salt and has non-clinical data suggesting a role in preserving muscle mass when used alongside a GLP-1 agonist.

Market context

The obesity therapeutics market has expanded rapidly on the back of GLP-1RA approvals, with semaglutide and tirzepatide now commanding substantial commercial footprints. However, the lean mass loss issue has emerged as a meaningful clinical and commercial concern, drawing academic groups, large-cap pharmaceutical companies, and specialist biotechs into the body-composition space. A number of companies are exploring anabolic agents, myostatin inhibitors, and bimagrumab-class approaches as potential combination strategies to offset GLP-1RA-associated muscle loss. Actimed's crossover-plus-parallel design is notable for addressing both the on-therapy and post-therapy windows in a single study, which could generate differentiated evidence if the primary endpoints are met.

Beyond obesity, Actimed holds global rights to S-oxprenolol (ACM-002), a separate candidate in development for amyotrophic lateral sclerosis-related muscle wasting, which has received US Orphan Drug Designation. The company has not disclosed a timeline for PROACT data readout, but with recruitment now complete, topline results could be expected within the next 12 to 18 months depending on follow-up duration. Investors and potential partners will be watching closely, given the strategic value of a validated muscle-preservation adjunct in the increasingly crowded GLP-1RA ecosystem.

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