Inhibrx reports Phase 2 HNSCC data showing INBRX-106 combo nearly doubles response rate

Inhibrx Biosciences announced on September 8, 2026 primary endpoint results from the randomized, controlled Phase 2 portion of its HexAgon study. The study is evaluating INBRX-106, a hexavalent OX40 agonist, in combination with pembrolizumab versus pembrolizumab monotherapy in first-line patients with treatment-naïve, PD-L1 positive (CPS ≥ 20) metastatic or unresectable recurrent head and neck squamous cell carcinoma.¹

The Phase 2 portion included 68 randomized patients, 63 evaluable for the primary endpoint, with 29 in the combination arm (10 HPV+) and 34 in the control arm (nine HPV+).¹

As of an August 19, 2026 data cutoff, confirmed objective response rate was 48.3% for the combination versus 26.5% for pembrolizumab alone.¹ Four patients (13.8%) in the combination arm achieved a complete response compared with none in the control arm.¹ Median progression-free survival was 9.6 months for the combination versus 4.9 months for pembrolizumab alone, with six-month PFS rates of 72.4% and 42.8%, respectively.¹

The effect was larger in HPV-positive patients. The combination arm showed an 80.0% cORR versus 33.3% for pembrolizumab alone, with 30.0% achieving complete response versus none, and 90.0% remaining progression-free at six months versus 33.0%.¹ Median PFS in HPV+ combination-arm patients had not yet been reached, compared with 4.6 months in the control arm.¹

The combination was generally manageable, with the most common treatment-related adverse events being rash, fatigue, and diarrhea, predominantly low grade.¹

Inhibrx plans to expand the Phase 2 portion by approximately 50 additional HPV+ oropharyngeal squamous cell carcinoma patients (CPS ≥ 1) to support a potential accelerated regulatory pathway, then align with the FDA and initiate a Phase 3 confirmatory trial.¹ The company is also running a Phase 1/2 study of INBRX-106 in perioperative non-small cell lung cancer, with initial results targeted by mid-2027.¹