Biopharmaceutical company Inhibrx Biosciences Inc (Nasdaq: INBX) on Monday reported positive interim results from the Phase 2 portion of its HexAgon study evaluating INBRX-106 in combination with pembrolizumab for first-line treatment of PD-L1 positive metastatic or unresectable recurrent head and neck squamous cell carcinoma (HNSCC).

This combination achieved a confirmed objective response rate of 44.0%, compared with 21.4% for pembrolizumab monotherapy, representing a 22.6% absolute improvement. The company also reported deeper tumour responses overall, including three complete radiographic responses in the combination arm, while no complete responses were observed in the control arm.

Pharmacodynamic data showed up to a 15-fold increase in CD8+ and CD4+ T-cell expansion in patients receiving INBRX-106 alongside pembrolizumab, compared with lower increases in the monotherapy arm, supporting the drug's proposed T-cell costimulatory mechanism.

Inhibrx said the safety profile was described as manageable and consistent with immunotherapy combinations, with no treatment-related deaths reported. Common adverse events included rash, diarrhoea, fatigue and infusion-related reactions, mostly low grade.

The Phase 2 study enrolled 68 patients across sites in the US, Europe and Asia. Progression-free survival data are expected in the fourth quarter of 2026, with the Phase 3 portion of the HexAgon study planned to begin in the third quarter of 2026.