Inhibrx Biosciences’ experimental INBRX-106 plus Keytruda produced a 48.3% confirmed response rate in a Phase 2 head-and-neck cancer study, versus 26.5% for Keytruda alone; Inhibrx shares fell 8.8% to $110.45 after the results, Reuters reported.
Of 68 patients enrolled, 63 were evaluable for the primary endpoint. In the small HPV-positive subgroup, confirmed responses were 80% among 10 evaluable patients receiving the combination and 33.3% among nine on Keytruda alone; complete response rates were 30% and 0%, respectively. Inhibrx plans to add about 50 HPV-positive oropharyngeal cancer patients to the study and discuss a potential accelerated regulatory pathway with the FDA after the expansion. Inhibrx estimates the U.S. could have about 30,000 HPV-positive head-and-neck cancer patients by 2029, including around 6,000 first-line recurrent patients; it estimates the opportunity at $1 billion in annual sales.
At the Aug. 19 cutoff, median progression-free survival was 9.6 months with the combination versus 4.9 months with Keytruda alone, and 72.4% versus 42.8% of patients remained progression-free at six months; Inhibrx said these data were still maturing. CEO Mark Lappe told Reuters the company could not explain the share decline and called the results “very de-risking.”
