Inhibrx’s OX40 data provide a rationale—not yet proof

Inhibrx Biosciences reported that its hexavalent OX40 agonist, INBRX-106, combined with Merck’s Keytruda (pembrolizumab), met the primary endpoint in a randomized Phase 2 study in first-line, PD-L1–high recurrent/metastatic head and neck squamous cell carcinoma.

At the Aug. 19, 2026 cutoff, confirmed objective response rate was 48.3% with INBRX-106 plus pembrolizumab, versus 26.5% with pembrolizumab alone. Median progression-free survival was 9.6 months versus 4.9 months, respectively; six-month PFS was 72.4% versus 42.8%.

The signal was particularly notable in HPV-positive disease:
reported response rates were 80% for the combination and 33.3% for Keytruda alone, though this was a small subgroup and needs confirmation.

Inhibrx says the observed T-cell expansion and activity in HPV-positive tumors support a rationale for pairing INBRX-106 with therapeutic cancer vaccines. The concept is that a vaccine supplies tumor-specific antigens while OX40 stimulation may expand and strengthen the resulting T-cell response.

This is a development rationale, not yet clinical proof for a vaccine combination:
Inhibrx has said it plans to explore such combinations, rather than reporting human efficacy data from an INBRX-106 vaccine trial.

The company intends to add roughly 50 patients with HPV-associated oropharyngeal cancer as it pursues a possible accelerated-approval path. The broader Phase 2/3 HexAgon program compares the Keytruda combination against Keytruda alone.