Response Rates Across the Full Trial
In a randomized Phase 2 trial, adding the experimental OX40 activator INBRX-106 to Merck’s Keytruda yielded confirmed tumor responses in 48.3% of patients with advanced head and neck cancer, versus 26.5% with Keytruda monotherapy, Inhibrx Biosciences reported September 8. The difference was most pronounced among HPV-positive patients. These company-reported findings have not undergone peer review and are based on limited patient numbers.
INBRX-106 stimulates OX40, a T-cell protein that amplifies anti-tumor immune activity, while Keytruda releases an immune checkpoint brake. Inhibrx describes this pairing as simultaneously applying acceleration and removing suppression. The company states this is the first OX40-activating agent to demonstrate clinical benefit in a randomized trial.
For patients with recurrent or metastatic head and neck cancer, these results support inquiry into clinical trials rather than representing a new standard of care. HPV infection underlies most oropharyngeal cancers in the United States.
The HPV-Positive Subgroup Behind the Headlines
The HPV-positive subgroup showed the most dramatic differences: 10 patients in the combination arm and 9 on Keytruda alone. Confirmed responses occurred in 80% versus 33.3%, complete responses in 30% versus 0%, and six-month progression-free survival was 90% versus 33%. Median progression-free survival was not reached in the combination group versus 4.6 months for Keytruda.
CEO Mark Lappe stated the company was most encouraged by “the depth and durability of the responses we are seeing with INBRX-106.” Inhibrx plans to enroll approximately 50 additional HPV-positive oropharyngeal cancer patients, including those with lower PD-L1 expression, and believes this expansion could support an accelerated approval pathway.
These figures warrant caution, as small-trial subgroup results frequently attenuate with larger cohorts. With only 10 and 9 patients, each additional response shifts percentages by roughly 10 points. Response rates and progression-free survival are early endpoints; overall survival has not been reported. The combination appeared generally manageable, with rash, fatigue, and diarrhea as the most common adverse events, mostly grade 1-2, and no treatment-related deaths were reported in the earlier interim analysis. Full safety data remain unpublished in a peer-reviewed journal.
In summary, this is a company-reported randomized Phase 2 readout involving 68 patients, including 19 HPV-positive individuals. It demonstrated higher response rates with the combination but has not shown improved survival, has not been peer-reviewed, and does not alter current standard of care.
Patients Weighing Trials and Standard Care
The primary audience includes adults with recurrent or metastatic head and neck cancer and high PD-L1 expression. Keytruda, with or without chemotherapy, is a standard first-line option for many. Patients should request their PD-L1 score and HPV status—typically assessed via p16 immunohistochemistry—as both inform treatment decisions and trial eligibility.
The trial is registered at ClinicalTrials.gov as NCT06295731. Its listing currently shows active but not recruiting, though the planned HPV-positive expansion may alter enrollment status; interested patients should consult their oncologist. Federal law generally requires health plans to cover routine care costs for qualifying trial participants, but patients should verify coverage and travel expenses beforehand.
Persistent sore throat, dysphagia, hoarseness, or neck mass lasting several weeks warrants clinical evaluation. While these symptoms often stem from benign causes, persistence justifies medical assessment.
Prevention Still Outpaces Treatment
HPV vaccination prevents infection with the virus types responsible for most HPV-related cancers, yet vaccination rates have plateaued. MedicalDaily reported that teen HPV vaccination remained flat for a fourth consecutive year, with rural adolescents lagging behind urban peers.
Parents should discuss HPV vaccination with their child’s clinician. The vaccine is routinely recommended at ages 11-12 and can begin as early as age 9, with catch-up dosing available for adolescents and young adults who were previously unvaccinated.
Subsequent steps depend on enrollment of the expanded HPV-positive cohort and full data presentation at a medical meeting or journal, where independent experts can scrutinize methodology. Inhibrx also anticipates initial lung cancer results by mid-2027. MedicalDaily will report peer-reviewed data upon release.
Key Questions Answered
What is INBRX-106?
An experimental OX40 agonist antibody from Inhibrx Biosciences designed to enhance anti-tumor immune activity. It is being evaluated in combination with Keytruda.
What did the trial show?
Among evaluable patients, confirmed tumor responses occurred in 48.3% of combination patients versus 26.5% on Keytruda alone. Median progression-free survival was 9.6 months versus 4.9 months.
Why are the HPV-positive results getting attention?
Eight of 10 HPV-positive patients on the combination responded versus three of nine on Keytruda alone. Given the small sample size, these figures may shift as more patients are accrued.
Is INBRX-106 approved?
No. It remains investigational. The company plans to expand enrollment by approximately 50 HPV-positive patients, which could support an accelerated approval pathway.
Have the results been peer-reviewed?
No. The data were company-released and have not been published in a journal or presented in full at a medical conference.
Who can join the trial?
The Phase 2 study enrolled adults with untreated recurrent or metastatic head and neck squamous cell carcinoma and high PD-L1 expression. Patients should inquire with their oncologist regarding eligibility and current enrollment for NCT06295731.
Can head and neck cancer be prevented?
HPV vaccination prevents infections that cause most HPV-related oropharyngeal cancers. Tobacco avoidance and alcohol moderation also reduce head and neck cancer risk.
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