MacroGenics, Inc. (NASDAQ:MGNX), a clinical-stage biopharmaceutical company focused on developing innovative antibody-based therapeutics for the treatment of cancer, today provided an update on the ongoing Phase 1 study evaluating MGC026, a novel B7-H3-directed antibody-drug conjugate (ADC), incorporating a topoisomerase I inhibitor-based linker-payload, in patients with advanced solid tumors.

The dose escalation portion of the study evaluated MGC026 at doses ranging from 1 mg/kg to 9 mg/kg administered every three weeks (q3W) and was completed in the fourth quarter of 2025. A dose of 7.5 mg/kg q3W is being further evaluated in four tumor-specific cohorts: recurrent or metastatic SCCHN, endometrial cancer, melanoma, and soft tissue sarcoma. The study is active at clinical sites in the United States, Australia and the United Kingdom.

The SCCHN cohort employs a Simon’s two-stage design, with a planned enrollment target of 40 patients. MacroGenics is currently enrolling SCCHN patients in Stage 2 after meeting the pre-specified response threshold in Stage 1. Enrollment in the other three cohorts continues as planned. As of July 8, 2026, a total of 74 patients had been enrolled across the dose escalation and ongoing cohort expansion portions of the study. As of this date, there were no cases of interstitial lung disease or ocular toxicity reported, and evidence of anti-tumor activity was observed across several indications.