Inhibrx Biosciences has reported positive interim data from the Phase II segment of its HexAgon study assessing INBRX-106 in treatment-naïve, programmed death ligand 1 (PD-L1) positive metastatic or unresectable recurrent head and neck squamous cell carcinoma (HNSCC).
The study evaluated the combination of the hexavalent OX40 agonist and pembrolizumab versus pembrolizumab alone in this patient population.
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It follows a design modelled on KEYNOTE-048, focusing on patients with high PD-L1 expression (combined positive score ≥ 20).
The Phase II segment enrolled 68 patients, with 33 assigned to the combination arm and 35 to the pembrolizumab-only arm. The study involved more than 80 sites across Asia, Europe and the US.
Data from 53 evaluable patients included 25 in the combination and 28 in the control arm, with a cut-off date of 7 May 2026. The remaining 15 patients had not reached the criteria for response confirmation.
According to the findings, 11 out of 25 patients (44.0%) in the combination arm had a confirmed objective response, compared to six out of 28 (21.4%) in the control arm.
Three complete responses occurred in the combination arm, while there were none with pembrolizumab alone.
Pharmacodynamic data indicated up to a 15-fold increase in peripheral cluster of differentiation 8-positive (CD8+) and CD4+ T-cell proliferation in the INBRX-106 combination arm.
The safety profile for the INBRX-106 and pembrolizumab combination was generally manageable.
The most reported treatment-related adverse events were rash, diarrhoea, fatigue, and infusion reactions, predominantly low-grade. No treatment-related deaths occurred.
Inhibrx CEO Mark Lappe said: “We are greatly encouraged by these early clinical results.
“These data, coupled with the clear evidence of T-cell expansion and superior depth of response, give us confidence that INBRX-106 could be the first costimulatory agent to fundamentally shift the efficacy ceiling of immunotherapy, and open the door to combinations with new modalities that could be enhanced by OX40 agonism.”
Progression-free survival data from the HexAgon trial’s Phase II segment are anticipated in the fourth quarter of 2026, with the Phase III portion planned for the third quarter.
