Inhibrx Reports Phase 2 HNSCC Data: INBRX-106 + Pembrolizumab Shows 48.3% Response Rate

Inhibrx Biosciences, Inc. announced the primary endpoint results from the randomized Phase 2 portion of its HexAgon study on September 8, 2026. The study evaluated 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 (HNSCC).

The analysis included 63 evaluable patients, with 29 in the combination arm and 34 in the control arm. The data cutoff date was August 19, 2026. The study was conducted at more than 80 sites across the United States, Europe, and Asia.

The primary endpoint of confirmed objective response rate (cORR) showed a 48.3% rate for the combination of INBRX-106 and pembrolizumab, compared to 26.5% for pembrolizumab alone. Four patients (13.8%) in the combination arm achieved a complete response, while no complete responses were observed in the control arm.

Progression-free survival (PFS) data indicated a median PFS of 9.6 months for the combination arm versus 4.9 months for the control arm. At six months, 72.4% of patients in the combination arm remained progression-free, compared to 42.8% in the control arm.

The efficacy signal was particularly pronounced in patients with HPV-positive disease. The combination arm demonstrated a 80.0% cORR compared to 33.3% for pembrolizumab alone. Notably, 30.0% of HPV+ patients in the combination arm achieved a complete response, and 90.0% remained progression-free at six months compared to 33.0% in the control arm.

The combination of INBRX-106 and pembrolizumab was generally manageable, with the most common treatment-related adverse events being rash, fatigue, and diarrhea, which were predominantly low grade.

In response to these results, Inhibrx plans to expand the randomized Phase 2 portion of the HexAgon trial by approximately 50 additional HPV+ Oropharyngeal Squamous Cell Carcinoma (OPSCC) patients (CPS ≥1) to support a potential accelerated regulatory pathway. The company intends to align with the U.S. Food and Drug Administration on this framework and initiate the Phase 3 portion of the HexAgon trial following the expansion.

Beyond HNSCC, Inhibrx is evaluating INBRX-106 in a Phase 1/2 study for non-small cell lung cancer (NSCLC) in the perioperative setting, with initial results targeted by mid-2027. The company also plans to explore the potential of INBRX-106 in combination with therapeutic cancer vaccines.