Core Insights - Several healthcare and biotech stocks saw significant price movements in after-hours trading on September 12, with notable gains in companies like Penumbra, Check-Cap, Adaptimmune Therapeutics, and NewAmsterdam Pharma, indicating a volatile session for the sector [1] Company Summaries Penumbra Inc. (PEN) - Penumbra's stock closed at $272.73 during regular trading, down by $3.67 or 1.33%, but rebounded to $289.86 in after-hours, gaining 6.28% [2] - The trading range for the day was $271.83 to $280.14, with a volume of 454,478 shares, slightly below its average of 472,087 [3] - The company has a market capitalization of approximately $10.64 billion and a trailing price-to-earnings ratio of 71.96 based on earnings per share of $3.79 [3] - Penumbra raised its full-year 2025 revenue guidance to $1.355 billion - $1.370 billion, reflecting a growth of 13% - 15% over 2024 revenue of $1.195 billion, and projects a 20% - 21% growth in its U.S. thrombectomy segment [5] - The company appointed Shruthi Narayan as its new president, indicating potential strategic shifts [6] Check-Cap Ltd. (CHEK) - Check-Cap's stock surged from $0.7459 to $2.1600 in after-hours trading, marking a gain of 191.22%, driven by a strategic merger announcement [6] - During regular trading, the stock gained 8.09%, closing at $0.7459, with a trading range of $0.6860 to $0.7602 and a volume of 67,178 shares [7] - The merger with MBody AI aims to enhance Check-Cap's colorectal cancer screening capabilities through AI integration [8] Adaptimmune Therapeutics plc (ADAP) - Adaptimmune's stock rose from $0.0560 to $0.0651 in after-hours trading, a gain of 16.25%, following a 10.89% increase during regular hours [8] - For Q2 2025, the company reported a net loss of $30.3 million, or $0.02 per share, with total revenue of $13.7 million, primarily from product sales of TECELRA [9] - Adaptimmune entered a definitive agreement to sell certain cell therapies for $55 million upfront, with potential future milestone payments of up to $30 million, allowing it to repay debt and restructure for value maximization [10] NewAmsterdam Pharma Company N.V. (NAMS) - NewAmsterdam's shares rose from $24.19 to $26.18 in after-hours trading, an 8.23% gain, following a 9.06% decline during the day [11] - The stock's recovery is attributed to optimism surrounding its lead candidate, obicetrapib, which has received regulatory review acceptance from the EMA [11] - The company reported Q2 2025 revenue of $16.45 million and a net loss of $14.92 million, improving from a $0.41 loss per share in the same quarter of 2024 [13]