INBRX-106 Doubles Response Rate in Phase 2 HNSCC

San Diego, California, U.S., September 8, 2026

INBRX-106 Nearly Doubles Response Rate

The randomized Phase 2 portion of the HexAgon study enrolled 68 patients, with 63 patients evaluable for the primary endpoint analysis. Patients received either INBRX-106 plus pembrolizumab or pembrolizumab monotherapy. The combination demonstrated a 48.3% cORR, nearly doubling the 26.5% response rate observed with pembrolizumab alone. The combination also generated complete responses in 13.8% of patients, compared with no complete responses in the control group. The PFS findings further supported the clinical activity of the combination. At the August 19, 2026 data cutoff, interim median PFS was 9.6 months for INBRX-106 plus pembrolizumab, compared with 4.9 months for pembrolizumab alone. The proportion of patients remaining progression-free at six months was 72.4% with the combination versus 42.8% with pembrolizumab monotherapy. The company noted that median PFS remained immature in the combination arm, meaning additional follow-up could provide further information about the durability of the observed benefit.

Stronger Activity Reported in HPV-Positive Disease

The clinical signal was particularly pronounced among patients with HPV-positive disease, an important subgroup in HNSCC. In these patients, INBRX-106 combined with pembrolizumab produced an 80.0% cORR, compared with 33.3% for pembrolizumab alone. The combination also generated a 30.0% complete response rate, while no complete responses were reported in the pembrolizumab-only group. The durability of treatment benefit was also notable in the HPV-positive population. At six months, 90.0% of patients receiving the combination remained progression-free, compared with 33.0% of patients receiving pembrolizumab alone. Median PFS for HPV-positive patients receiving INBRX-106 plus pembrolizumab had not yet been reached, compared with 4.6 months for pembrolizumab monotherapy. Treatment with the combination was generally manageable, with rash, fatigue and diarrhea reported as the most common treatment-related adverse events, predominantly at low grades.

Phase 2 Expansion Planned for HPV-Positive HNSCC

INBRX-106 is a hexavalent agonist targeting OX40 (CD134), a costimulatory receptor expressed on T cells. The molecule is engineered to promote high-order OX40 receptor clustering, with the goal of enhancing T-cell activation and survival and strengthening antitumor immune responses. The positive randomized results provide clinical support for this mechanism and potentially differentiate INBRX-106 from conventional approaches to OX40 activation. Based on the results, Inhibrx plans to expand the randomized Phase 2 portion of HexAgon by approximately 50 additional HPV-positive oropharyngeal squamous cell carcinoma (OPSCC) patients with CPS ≥1. The company intends to discuss the development framework with the U.S. FDA and potentially proceed toward a Phase 3 confirmatory study. Inhibrx is also evaluating INBRX-106 in a Phase 1/2 study in the perioperative setting for non-small cell lung cancer (NSCLC) and plans to investigate combinations with therapeutic cancer vaccines. The results position INBRX-106 as a promising investigational immunotherapy, but the current findings remain based on a relatively small Phase 2 population and interim analyses. Further follow-up and confirmatory clinical studies will be required to establish the therapy’s long-term efficacy, safety and potential regulatory role in HNSCC.

Source: Inhibrx Biosciences press release