PROACT Enrollment Complete: LBM Preservation Thesis Unproven, Regulatory Pathway Uncharted

Actimed Completes PROACT Phase 2a Recruitment for S-pindolol benzoate

Actimed Therapeutics has announced the successful completion of patient recruitment for its PROACT Study (NCT07101939), a Phase 2a, randomized, double-blind, placebo-controlled trial. The study, which enrolled over 100 obese adults, is evaluating S-pindolol benzoate (ACM 001.1) in two distinct contexts: during active semaglutide therapy to preserve lean body mass (LBM) and after semaglutide discontinuation to optimize body composition and prevent fat mass rebound. This trial aims to address a critical unmet need in obesity care by mitigating LBM loss associated with GLP-1 receptor agonist therapy and improving muscle-to-fat ratio post-treatment.

• The PROACT Study is designed to tackle the significant challenge of lean body mass (LBM) loss during GLP-1 receptor agonist (GLP-1RA) therapy like semaglutide, and the unfavorable body composition changes, including fat mass rebound, that can occur after GLP-1RA discontinuation. This is particularly crucial for vulnerable patient populations such as older or frail individuals or those with co-morbidities, highlighting a critical unmet need in current obesity care.
• The Phase 2a PROACT trial features an innovative two-part design to answer two independent questions. It evaluates S-pindolol benzoate (10 mg or 15 mg BID) in patients concurrently receiving semaglutide to assess LBM preservation, and in a separate cohort, after 20 weeks of semaglutide cessation, to determine its potential in improving the proportion of lean mass during weight regained post GLP-1RA therapy.
• S-pindolol benzoate (ACM 001.1) is being investigated as a targeted anabolic catabolic transforming agent. Previous studies have generated promising Phase 2a proof-of-concept data in cancer cachexia patients, and early non-clinical data confirms a potential role for S-pindolol benzoate in preserving muscle mass when used in combination with a GLP-1 agonist for weight loss, positioning it to potentially optimize body composition in obese patients.

Addressing Lean Body Mass Loss in GLP-1RA Obesity Therapy

Current obesity treatment approaches face a complex set of interrelated challenges spanning biological, pharmacological, economic, and systemic dimensions. While newer agents and surgical techniques have substantially advanced the field, durable long-term outcomes remain difficult to achieve across all modalities.

• Metabolic adaptation and weight regain: Diet-induced and intervention-induced weight loss triggers counter-regulatory physiological responses — including reductions in total daily energy expenditure that exceed predictions based on body composition changes, shifts in substrate metabolism, and compensatory alterations in gut hormone profiles (reduced anorectic hormones, increased orexigenic hormones) — that persist beyond the initial weight loss period and drive weight recidivism.

• Loss of lean body mass: Both bariatric surgery and GLP-1 receptor agonists are associated with unintended loss of fat-free mass, particularly skeletal muscle. This compromises physical functionality, quality of life, and long-term metabolic health, with heightened concern for individuals with sarcopenic obesity or those at risk of frailty. Current weight-loss strategies often fail to adequately address the need to maintain fat-free mass.

• Gastrointestinal adverse effects and treatment discontinuation: GI side effects — nausea, vomiting, diarrhea, and constipation — are the most frequently reported adverse events with GLP-1 receptor agonists such as semaglutide and tirzepatide, particularly during dose escalation. In a meta-analysis of semaglutide in nondiabetic adults, treatment discontinuation due to adverse events was significantly higher in the semaglutide group (RR 2.62, 95% CI: 1.70–4.03; P = .001), directly impacting adherence and long-term outcomes.

• Access barriers — cost, insurance, and age restrictions: High costs, supply shortages, and insurance coverage gaps limit widespread implementation, particularly in low-resource settings. For pediatric populations, access to FDA-approved anti-obesity medications is further constrained by age restrictions and inconsistent insurance coverage. Bariatric surgery, despite being cost-effective in select subgroups, is utilized by only 1% of the currently eligible population in the United States, with insurance benefit design identified as a significant structural barrier.

• Weight regain following medication discontinuation: Weight regain after stopping pharmacotherapy underscores the need for ongoing adherence and lifestyle support, reinforcing obesity's characterization as a chronic, relapsing disease rather than a condition amenable to finite treatment courses.

• Long-term safety data gaps: For both newer pharmacological agents (including oral GLP-1 agonists and triple-receptor agonists such as retatrutide) and off-label medications used in pediatric obesity, long-term efficacy and safety data remain insufficient. Further long-term randomized trials are needed to evaluate durability of weight loss and long-term safety profiles across emerging pharmacologic agents.

• Educational and perception gaps: Surveys of people with obesity and healthcare providers in the US identified concerns regarding long-term side effects, costs, and perceptions of anti-obesity medications that do not align with treatment of a chronic disease as persistent barriers, with educational gaps limiting shared decision-making in obesity care.

PROACT Study: A Novel Design for S-pindolol benzoate in Obesity

Recent evidence syntheses have evaluated the efficacy, safety, and comparative effectiveness of incretin-based agents — including tirzepatide, semaglutide, liraglutide, and danuglipron — across a range of trial designs in adults with overweight or obesity.

S-pindolol Benzoate: Redefining Body Composition in Obesity Management

The remarkable efficacy of GLP-1 receptor agonists has transformed the landscape of obesity treatment, offering unprecedented weight loss for millions. However, this success comes with a recognized challenge: a significant proportion of the weight lost is often lean body mass, not just fat. This lean mass loss can lead to sarcopenia, a condition characterized by decreased muscle mass and strength, which is associated with adverse outcomes such as physical disability and reduced quality of life. Addressing this critical unmet need is paramount for optimizing long-term patient health.

Actimed Therapeutics' PROACT Study, evaluating S-pindolol benzoate (ACM 001.1), represents a strategic move to tackle this issue head-on. S-pindolol benzoate, a beta-blocker, has previously shown promise in preclinical models of cancer cachexia, a severe wasting syndrome, by attenuating lean mass wasting and improving cardiac function. The PROACT trial is designed with a dual approach: first, to preserve lean body mass during active semaglutide therapy, and second, to optimize body composition and prevent the common challenge of fat mass rebound after semaglutide discontinuation.

If successful, this trial could usher in a new era for obesity management, moving beyond mere weight reduction to a more holistic focus on body composition and muscle health. This could significantly enhance the value proposition of GLP-1 receptor agonists by mitigating a key side effect and improving the sustainability of treatment benefits. However, several considerations remain. The translation of efficacy from a cancer cachexia model to GLP-1 receptor agonist-induced lean mass loss in obese adults requires careful validation, as the underlying mechanisms of muscle wasting may differ. Furthermore, while some newer generation beta-blockers exhibit a neutral metabolic profile, the specific impact of S-pindolol benzoate on glucose and lipid metabolism in this patient population, especially in combination with semaglutide, warrants thorough assessment. Finally, demonstrating the long-term sustainability of improved body composition and prevention of fat mass rebound will be crucial, given the complex metabolic factors that drive weight regain. The PROACT study's results are eagerly awaited, as they hold the potential to redefine comprehensive obesity care.