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INBRX-106 plus pembrolizumab delivers a 48.3% cORR and 72.4% of patients remain progression free at 6 months, compared with 26.5% and 42.8% for pembrolizumab alone
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Results are most pronounced in HPV+ patients, with cORR (80.0% vs 33.3%), CR rate (30.0% vs 0%), and PFS6 improvement (90.0% vs 33.0%) vs pembrolizumab alone
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Inhibrx will expand the Phase 2 study by approximately 50 HPV+ patients and may serve as a potential pathway to accelerated approval
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Positive results support large expansion opportunities into highly immunogenic tumors and combination with cancer vaccines
SAN DIEGO, Sept. 8, 2026 /PRNewswire/ -- Inhibrx Biosciences, Inc. (Nasdaq: INBX) ("Inhibrx" or the "Company"), a clinical-stage biopharmaceutical company focused on developing a broad pipeline of novel biologic therapeutic candidates, today announced the primary endpoint results from the randomized and controlled Phase 2 portion of the HexAgon study, which is evaluating the safety and efficacy of INBRX-106, a hexavalent OX40 agonist, in combination with pembrolizumab (the combination arm) versus pembrolizumab monotherapy (the control arm) in first-line patients with treatment-naïve, PD-L1 positive (CPS ≥ 20) metastatic or unresectable recurrent head and neck squamous cell carcinoma (HNSCC). Baseline prognostic factors were largely balanced between the two arms, and the study is being conducted at more than 80 sites in the United States, Europe and Asia. The Phase 2 portion of the HexAgon study included a total of 68 randomized patients, 63 of whom were evaluable for the primary endpoint analysis, including 29 patients in the combination arm (10 of which were HPV+) and 34 patients in the control arm (nine of which were HPV+).
The primary endpoint analysis, which had a data cutoff of August 19, 2026, demonstrated a confirmed objective response rate (cORR) of 48.3% for INBRX-106 plus pembrolizumab compared with 26.5% for pembrolizumab alone. Four patients (13.8%) in the combination arm achieved a complete response compared with no complete responses in the control arm. Median progression-free survival (PFS) continues to mature. As of the data cutoff, median PFS was 9.6 months for INBRX-106 plus pembrolizumab compared with 4.9 months for pembrolizumab alone, with six-month PFS rates of 72.4% and 42.8%, respectively.
The efficacy signal was particularly pronounced in patients with HPV+ disease, where the combination arm demonstrated an 80.0% cORR compared with 33.3% for pembrolizumab alone. Notably, 30.0% of the HPV+ patients treated in the combination arm achieved a complete response, compared with no complete responses in the control arm. The durability of the benefit was also particularly striking, with 90.0% of patients receiving INBRX-106 plus pembrolizumab remaining progression-free at six months compared with 33.0% who were receiving pembrolizumab alone. As of the data cutoff, median PFS in the combination arm in patients with HPV+ disease had not yet been reached compared with 4.6 months for pembrolizumab alone.
The combination of INBRX-106 and pembrolizumab was generally manageable. The most common treatment-related adverse events were rash, fatigue, and diarrhea, which were predominantly low grade.
"What is most exciting to us is the depth and durability of the responses we are seeing with INBRX-106, particularly in HPV+ disease," said Mark Lappe, co-founder and Chief Executive Officer of Inhibrx. "These results strengthen our conviction in OX40-mediated T-cell costimulation and give us a strong rationale to expand the program, not only into HPV+ disease, but also to explore the potential of INBRX-106 in other highly immunogenic tumors and in combination with cancer vaccines."
Based on these results, Inhibrx plans to expand the randomized Phase 2 portion of the HexAgon trial by approximately 50 additional HPV+ Oropharyngeal Squamous Cell Carcinoma (OPSCC) patients (CPS ≥ 1), to support a potential accelerated regulatory pathway. Following the Phase 2 expansion, the Company plans to align with the FDA on this framework and initiate the Phase 3 portion of the HexAgon trial, which is intended to serve as the confirmatory study. These results also position OX40 agonism as a promising treatment approach beyond recurrent/metastatic disease, with potential to extend durable, T-cell driven antitumor activity into earlier-stage HPV+ OPSCC.
Beyond HNSCC, Inhibrx is evaluating the potential of INBRX-106 in other highly immunogenic tumor types. The Company is currently conducting a Phase 1/2 study of INBRX-106 in the perioperative setting of non-small cell lung cancer (NSCLC), with initial results targeted by mid-2027. This readout is expected to provide important clinical insights to inform future development, demonstrating the potential for INBRX-106 to extend well beyond head and neck cancer into not only perioperative lung cancer, but broader solid tumor indications.
The Company also plans to explore the potential of INBRX-106 in combination with therapeutic cancer vaccines. The clinical activity and T-cell responses observed with INBRX-106 in HPV+ disease demonstrate its ability to amplify antigen-driven T-cell responses, providing strong scientific justification for cancer vaccine combination strategies.
The Company will host a live webcast presentation today, September 8, 2026, at 5:00 a.m. Pacific Time to further discuss the results. The webcast will also include a slide presentation of the data, which is also incorporated into the Company's investor deck accessible at https://inhibrx.com/inhibrx-biosciences-inc-investors/.
About the Conference Call
Investors may join via the web: https://app.webinar.net/4712m15mpwW or may listen to the call by dialing (1-888-880-3330). Please refer to Inhibrx Biosciences, Inc. or the conference ID 6981384 when calling in. The webcast will also include a slide presentation of the data, which is also incorporated into the Company's investor deck accessible at https://inhibrx.com/inhibrx-biosciences-inc-investors/. Following the webcast, the presentation may be accessed through a link on the "Events and Presentations" section of Inhibrx's website. The webcast will be available for 60 days following the event. Inhibrx will also update its corporate presentation within the "Investors" section of its website at www.inhibrx.com.
About INBRX-106
INBRX-106 is a hexavalent agonist targeting OX40 (CD134), a costimulatory receptor on T-cells. Utilizing Inhibrx's proprietary single-domain antibody (sdAb) platform, INBRX-106 is designed to achieve the high-order receptor clustering necessary for robust T-cell activation and survival, a feat that has eluded traditional bivalent antibody approaches.
About Inhibrx Biosciences, Inc.
Inhibrx Biosciences is a clinical-stage biopharmaceutical company focused on developing a broad pipeline of novel biologic therapeutic candidates. Inhibrx Biosciences utilizes diverse methods of protein engineering to address the specific requirements of complex target and disease biology, including its proprietary protein engineering platforms. Inhibrx Biosciences was incorporated in January 2024 as a direct, wholly-owned subsidiary of Inhibrx, Inc. Prior to the sale of Inhibrx, Inc. and the INBRX-101 program to Sanofi S.A., Inhibrx Biosciences acquired certain corporate infrastructure and other assets and liabilities through a series of internal restructuring transactions effected by Inhibrx, Inc. Inhibrx, Inc. also completed a distribution to holders of its shares of common stock of 92% of the issued and outstanding shares of Inhibrx Biosciences. Following such transactions, Inhibrx Biosciences' current clinical pipeline of therapeutic candidates includes ozekibart (INBRX-109) and INBRX-106, both of which utilize multivalent formats where the precise valency can be optimized in a target-centric way to mediate what we believe to be the most appropriate agonist function.