Interim INBRX-106 Phase 2 data show a near doubling of confirmed response rates over pembrolizumab alone in a high-PD-L1 head and neck cancer population, offering early evidence that hexavalent OX40 agonism may augment checkpoint inhibitor activity in a setting where monotherapy responses remain limited.
Inhibrx Biosciences (Nasdaq: INBX), based in San Diego, reported interim Phase II results for INBRX-106 in combination with pembrolizumab (Keytruda) versus pembrolizumab alone in treatment-naïve, PD-L1-positive (CPS ≥20) metastatic or unresectable recurrent head and neck squamous cell carcinoma (HNSCC), with a confirmed objective response rate of 44.0% in the combination arm compared with 21.4% in the monotherapy control arm, the company said on May 11, 2026.
In the confirmed response-evaluable population of 53 patients — 25 in the combination arm and 28 in the control arm — 11 patients receiving INBRX-106 plus pembrolizumab achieved a confirmed objective response versus 6 patients on pembrolizumab alone, an absolute difference of 22.6 percentage points. Three complete radiographic responses were observed in the combination arm and none in the control arm. Pharmacodynamic data from peripheral blood analysis showed up to a 15-fold increase in CD8+ and CD4+ T-cell proliferation and up to a 4-fold increase in T-cell activation in combination-treated patients, compared with up to 2.5-fold proliferation and 1.5-fold activation in the pembrolizumab monotherapy group. The combination arm's safety profile was described as manageable, with the most common treatment-related adverse events being rash, diarrhea, fatigue, and infusion-related reactions, predominantly low-grade. No treatment-related deaths were reported in either arm. The data cutoff was May 7, 2026.
The HexAgon-HN trial (NCT06295731) is a randomized Phase II/III study enrolling patients with recurrent or metastatic HNSCC expressing PD-L1 at CPS ≥20, with a planned total enrollment of 410 across more than 80 sites in the US, Europe, and Asia. The Phase II portion enrolled 68 patients, 33 randomized to the INBRX-106 combination and 35 to pembrolizumab monotherapy, with baseline prognostic factors reported as largely balanced between arms. The interim efficacy analysis was restricted to 53 patients who had either experienced confirmed disease progression or death, or completed at least two on-study tumor assessments; the remaining 15 patients had not yet reached the maturity threshold for response confirmation at the time of the data cut. Progression-free survival data from the Phase 2 portion are expected in Q4 2026, and the company said it plans to initiate the Phase III portion in Q3 2026. The data remain interim and are based on a subset of the enrolled Phase II population; final results may differ.