MacroGenics Announces Phase 1 MGC026 Delivers 27% Response Rate In SCCHN, Showing Durable Tumor Activity And Advancing Toward Front-Line Pembrolizumab Combination Trial

• Durable responses observed across multiple tumor types during dose escalation
• MGC026 demonstrated 27% best overall response rate (6/22 patients; 4 confirmed and 2 unconfirmed PRs) in heavily pretreated SCCHN patients
• MGC026 demonstrated manageable safety and tolerability profile with no treatment-related discontinuations in SCCHN patients
• Plan to initiate front-line SCCHN cohort evaluating MGC026 in combination with pembrolizumab

ROCKVILLE, MD, Oct. 23, 2026 (GLOBE NEWSWIRE) -- MacroGenics, Inc. (NASDAQ:MGNX), a clinical-stage biopharmaceutical company focused on developing innovative antibody-based therapeutics for the treatment of cancer, today announced positive interim data from its Phase 1 study evaluating MGC026, a B7-H3-directed antibody-drug conjugate (ADC), in patients with advanced solid tumors. These Phase 1 data were presented today at the European Society for Medical Oncology (ESMO) 2026 Congress in Madrid, Spain. These results demonstrated durable activity across a broad range of solid tumors, which the Company believes supports expanded development of MGC026 in front-line metastatic squamous cell carcinoma of the head and neck (SCCHN) in combination with pembrolizumab.