GT Biopharma shares surge 39.08% after-hours on progress in GTB-3650 trial and upcoming GTB-5550 IND submission.

GT Biopharma (NASDAQ: GTBP) surged 39.08% in after-hours trading following the release of its third-quarter 2025 financial results and clinical updates. The stock’s sharp rise aligned with positive developments in its pipeline, including advancement of GTB-3650’s Phase 1 trial for hematologic malignancies to Cohort 4 at 10 µg/kg/day, with an update expected in Q1 2026. The company also announced plans to submit an IND application for GTB-5550, targeting B7H3-expressing solid tumors, by late December 2025 or January 2026. Management highlighted the safety profile of GTB-3650 and its potential competitive edge over other modalities, while reduced R&D expenses ($0.6 million vs. $1.3 million in Q3 2024) and a $2.6 million cash balance—sufficient to fund operations into Q1 2026—reinforced operational efficiency. These catalysts, emphasizing clinical progress and regulatory milestones, drove investor optimism in the after-hours session.