Core Insights - Several small- and mid-cap biotech and medical stocks experienced significant after-hours trading activity on September 26, driven by clinical updates, investor presentations, and strategic announcements. Company Summaries - **Enanta Pharmaceuticals Inc. (ENTA)**: The stock surged 20% in after-hours trading to $9.48 after closing at $7.90, following the announcement of upcoming topline results from its Phase 2b study on zelicapavir for RSV treatment in high-risk adults [2][3]. - **Acumen Pharmaceuticals Inc. (ABOS)**: Shares rebounded 12.67% to $1.60 after closing at $1.42, driven by renewed interest in its Alzheimer's pipeline, particularly the Phase 2 candidate Sabirnetug (ACU193) [4]. - **Delcath Systems Inc. (DCTH)**: The stock gained 6.00% in after-hours trading to $11.39 after closing at $10.74, following renewed investor interest in its CHOPIN Phase 2 trial data presentation scheduled for ESMO 2025 Congress [5][6]. - **Vivos Therapeutics Inc. (VVOS)**: The stock climbed 4.81% to $3.27 after closing at $3.12, likely due to renewed interest following recent positive clinical trial results for its pediatric OSA treatment [7][8]. - **Xilio Therapeutics (XLO)**: Shares rose 4.28% to $0.83 after closing at $0.7959, driven by enthusiasm surrounding the initiation of a Phase 2 trial for its tumor-activated IL-12 candidate, which also triggered a $17.5 million payment from Gilead [9][10]. - **Nyxoah SA (NYXH)**: The stock increased 3.77% to $4.68 after closing at $4.51, supported by optimism regarding its international expansion and a recent patent infringement lawsuit against Inspire Medical Systems [11].

Core Insights - Acumen Pharmaceuticals is set to present new findings at the Alzheimer's Association International Conference (AAIC®) 2025, focusing on cost savings from using pTau217 as a screening tool in its Phase 2 ALTITUDE-AD trial of sabirnetug for Alzheimer's disease [1][2] - The company emphasizes the significance of combining biomarker-driven screening with targeted therapeutics to enhance clinical trial designs and drug development for Alzheimer's disease [2] Company Overview - Acumen Pharmaceuticals is a clinical-stage biopharmaceutical company developing sabirnetug (ACU193), a humanized monoclonal antibody targeting soluble amyloid beta oligomers (AβOs), which are linked to Alzheimer's disease [3][5] - Sabirnetug has received Fast Track designation from the U.S. FDA for treating early Alzheimer's disease and is currently in a Phase 2 study [3][7] ALTITUDE-AD Trial - The ALTITUDE-AD trial, initiated in 2024, is a Phase 2, multi-center, randomized, double-blind, placebo-controlled study assessing the efficacy and safety of sabirnetug in slowing cognitive decline in early Alzheimer's disease patients [4] - The trial has enrolled 542 participants across multiple sites in the U.S., Canada, the EU, and the UK [4] Presentation Details - Acumen's presentations at AAIC will cover the cost savings analysis of pTau217 in the ALTITUDE-AD trial and the selectivity of sabirnetug for Aβ oligomers compared to other treatments like lecanemab and aducanumab [2][6]

Sabirnetug (ACU193) Overview - Sabirnetug (ACU193) is a monoclonal antibody (mAb) highly selective for toxic Amyloid Beta Oligomers (AβOs) for early Alzheimer's Disease (AD)[4, 9] - Phase 2 (IV) topline results expected in late 2026[5] - Acumen believes it has the expertise and resources to advance sabirnetug into early 2027[99] Alzheimer's Disease Market and Sabirnetug's Potential - Early AD patient population represents a significant and growing market, with approximately 5 million early Alzheimer's Disease cases in the U S[6, 7] - Sabirnetug has the opportunity to be a treatment of choice in the large early AD population due to potential clinical and safety benefits conferred by AO selectivity[37] - Sabirnetug is well-positioned to emerge as a potential next-generation treatment of choice, with recent approvals paving a new path for the treatment of AD[36] Clinical Trial Results and Development - INTERCEPT-AD Phase 1 data support the potential for Sabirnetug to offer next-generation efficacy and safety[73] - Phase 2 ALTITUDE-AD study enrollment completed in March 2025, with topline results expected in late 2026[19, 101] - Topline results announced in March 2025 show systemic exposure supports further clinical development of the subcutaneous formulation[85, 101] Sabirnetug's Selectivity and Target Engagement - Sabirnetug demonstrates high selectivity for AβOs versus monomeric Aβ, with 8750x higher binding affinity for Aβ oligomers compared to Aβ1-40 monomer[20, 25] - Nearly all Sabirnetug-treated patients in high-dose MAD cohorts showed reductions in plaque load after three doses at 63 or 70 days[49] - Mean reduction in amyloid plaque was 137 centiloids (206%) in the 25 mg/kg Q2W MAD cohort and 181 centiloids (256%) in the 60 mg/kg Q4W MAD cohort[50] Safety Profile - The Phase 1 trial showed a compelling overall safety profile, with a low incidence of ARIA-E, approximately 10% of total ARIA-E cases[72]