Inhibrx Biosciences (INBX) Study update summary

Study Design and Patient Population

• Interim phase II HexAgon study evaluated INBRX-106 plus pembrolizumab versus pembrolizumab alone in first-line PD-L1-positive head and neck cancer patients with CPS ≥20.

• The study enrolled 68 patients (33 in combination, 35 in control), with preliminary data from 53 evaluable patients and balanced baseline prognostic factors.

• Conducted at over 80 sites globally, including the US, Europe, and Asia.

• The trial design closely mirrored KEYNOTE-048 to assess added benefit over checkpoint inhibition alone.

• OX40 agonism, targeted by INBRX-106, aims to enhance T-cell co-stimulation and improve checkpoint inhibitor efficacy.

Efficacy and Response Data

• Confirmed objective response rate was 44% in the INBRX-106 combination arm versus 21.4% in the pembrolizumab arm, a 22.6% absolute increase.

• Three complete responses were observed in the combination arm, none in the control arm; most responders in the combination arm had over 50% tumor shrinkage.

• Depth of response was notably greater in the combination arm, with stable disease patients also showing significant tumor reduction.

• Peripheral blood analysis showed up to a 15-fold increase in CD8+ and CD4+ T-cell proliferation and up to a four-fold increase in activation with the combination.

Safety and Tolerability

• The combination was generally manageable, with most adverse events being low grade, including rash, diarrhea, fatigue, and infusion reactions.

• No treatment-related deaths were reported in either arm.

• Safety profile was consistent with immune activation and similar to pembrolizumab monotherapy in KEYNOTE-048.

• Over 200 patients have been exposed to INBRX-106 across studies, supporting a robust safety understanding.