Summary of results
Shares of Inhibrx Biosciences, Inc. (NASDAQ:INBX) rose 6% on Tuesday after the company reported encouraging outcomes from a Phase 2 segment of the HexAgon trial testing INBRX-106 administered with pembrolizumab for head and neck cancer.
The combination therapy produced a confirmed objective response rate (ORR) of 48.3%, compared with 26.5% for pembrolizumab alone in the trial. HexAgon enrolled first-line, treatment-naive patients with PD-L1 positive metastatic or unresectable recurrent head and neck squamous cell carcinoma.
Study population and key efficacy findings
The analysis included 63 evaluable patients overall, with 29 in the arm receiving INBRX-106 plus pembrolizumab and 34 in the pembrolizumab-only control arm. In the combination arm, four patients achieved a complete response while the control arm recorded no complete responses. At the six-month mark, the progression-free survival (PFS) rate was 72.4% for patients on the combination regimen versus 42.8% for those receiving pembrolizumab alone.
Subgroup results in HPV-positive patients
Results were notably stronger among HPV-positive patients. In that subgroup, the confirmed ORR for the combination therapy reached 80.0%, compared with 33.3% for pembrolizumab alone. Complete responses occurred in 30.0% of HPV-positive patients receiving the combination and in 0% of those in the control arm. Six-month PFS in the HPV-positive cohort was 90.0% with the combination versus 33.0% with pembrolizumab monotherapy.
Safety and tolerability
The combination was described as generally manageable. The most frequently reported treatment-related adverse events were rash, fatigue, and diarrhea, and these events were predominantly low grade according to the company report.
Next steps from Inhibrx
On the basis of these Phase 2 findings, Inhibrx intends to expand the Phase 2 portion of the HexAgon study by approximately 50 additional HPV-positive patients to support a potential accelerated regulatory pathway. The company also plans to align with the U.S. Food and Drug Administration on that framework prior to initiating a Phase 3 confirmatory study.
Context for markets and stakeholders
The data and the planned trial expansion are material to investors tracking Inhibrx and to stakeholders in oncology drug development, particularly those focused on head and neck squamous cell carcinoma and HPV-associated disease. The safety profile reported will be relevant to clinicians and trial designers considering combination regimens that include immune checkpoint inhibitors.