Friday's Biotech Bounce: Clinical Momentum Fuels Late-Day Gains

(RTTNews) - Several small- and mid-cap biotech and medical technology stocks saw notable after-hours price action on Friday, September 26, following a mix of clinical updates, investor presentations, and strategic announcements.

Enanta Pharmaceuticals Inc. (ENTA) surged sharply in after-hours trading on Friday, September 26, following a modest gain during the regular session. The stock closed the day at $7.90, up 1.94%, before vaulting another 20% after hours to reach $9.48. This dramatic post-close rally was driven by investor reaction to the company's announcement regarding upcoming topline results from its Phase 2b study evaluating zelicapavir for the treatment of respiratory syncytial virus or RSV in high-risk adults.

The news, released late Friday, confirmed that Enanta will present data from the RSVHR trial during a webcast scheduled for Monday, September 29. The study focuses on zelicapavir, a small-molecule antiviral candidate, and its potential efficacy in a vulnerable patient population.

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Acumen Pharmaceuticals Inc. (ABOS) staged a strong rebound in after-hours trading on Friday, following a weak performance during the regular session. Shares closed at $1.42, down 4.05%, but reversed course after the bell, climbing 12.67% to $1.60 by 7:16 PM EDT.

The after-hours surge appears to be driven by renewed investor interest in Acumen's Alzheimer's pipeline, particularly its lead candidate Sabirnetug (ACU193), which is currently in Phase 2 trials. While no fresh news was issued on Friday, sentiment may have been buoyed by recent presentations at Citi's Biopharma Back to School Conference and the Alzheimer's Association International Conference (AAIC), where Acumen highlighted the oligomer-selectivity of Sabirnetug and the utility of its pTau217 screening assay.

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Delcath Systems Inc. (DCTH) reversed early losses with a strong after-hours rally on Friday. The stock closed the regular session at $10.74, down 1.06%, but rebounded sharply after hours, gaining 6.00% to reach $11.39 by 6:50 PM EDT.

The late-day momentum was likely fueled by renewed investor interest following Delcath's recent announcement regarding its CHOPIN Phase 2 trial. Earlier in the week, the company confirmed that data from the investigator-initiated study would be presented at the ESMO 2025 Congress. The trial evaluates the HEPZATO KIT, a hepatic delivery system for high-dose melphalan, in patients with liver-dominant metastatic colorectal cancer. The presentation is expected to shed light on response rates and safety outcomes, which could have implications for broader adoption and regulatory progress.

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Vivos Therapeutics Inc. (VVOS) reversed its intraday losses with a notable rebound in after-hours trading on Friday. The stock closed the regular session at $3.12, down 6.87%, before climbing 4.81% after hours to $3.27 by 7:59 PM EDT.

The late-day recovery appears to be driven by renewed investor interest following recent clinical trial results announced earlier this month. Vivos reported landmark data from its pediatric obstructive sleep apnea (OSA) study, highlighting the efficacy of its non-invasive Vivos Method in treating dentofacial abnormalities and sleep-disordered breathing in children. Although the news was not released on Friday itself, the after-hours move suggests that traders may be positioning ahead of further developments or anticipating analyst upgrades.

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Xilio Therapeutics (XLO) extended its gains into after-hours trading on Friday, following a strong close during the regular session. Shares finished the day at $0.7959, up 4.83%, and continued climbing after hours to $0.83, marking an additional 4.28% gain by 9:40 PM EDT.

The upward momentum appears to be driven by investor enthusiasm surrounding Xilio's recent pipeline developments. Earlier this month, the company announced the initiation of a Phase 2 trial for efarindodekin alfa (XTX301), its tumor-activated IL-12 candidate. The milestone also triggered a $17.5 million payment under its exclusive license agreement with Gilead, reinforcing confidence in the commercial viability of XTX301.

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Nyxoah SA (NYXH) posted a modest gain during Friday's regular trading session, closing at $4.51, up 0.45%. The momentum accelerated after hours, with shares rising another 3.77% to $4.68 by 7:59 PM EDT. This marks a reversal from earlier in the week, when the stock had been under pressure following a string of declines.

The after-hours strength appears to be driven by renewed investor optimism surrounding Nyxoah's international expansion and recent legal developments. Earlier this month, the company filed a patent infringement lawsuit against Inspire Medical Systems, Inc., signaling a more assertive stance in protecting its intellectual property. Additionally, Nyxoah announced an expanded presence in the Middle East, which could open new commercial pathways for its Genio system, a minimally invasive neurostimulation therapy for moderate to severe obstructive sleep apnea.