Inhibrx, Inc. announced initial results from Part 3 (combination dose escalation) of the 4-part Phase 1 trial of INBRX-106, a novel hexavalent OX40 agonist, in combination with Keytruda in development for the treatment of patients with solid tumors. Additionally, an update on single agent data from Part 1 (single agent dose escalation) and Part 2 (single agent dose expansion) of the trial was provided. In the all-comer Part 3 of this Phase 1 trial, the dose of INBRX-106 was escalated in combination with Keytruda® in 21 patients with locally advanced or metastatic solid tumors. INBRX-106 in combination with Keytruda® was observed to be well tolerated, with predominantly mild or moderate immune-related toxicities noted. The maximum administered dose of INBRX-106 was 0.3 mg/kg, at which dose-limiting, immune-related toxicities such as dermatitis were observed. Accordingly, 0.1 mg/kg dosed every three weeks was determined to be the maximum tolerated dose (MTD) of INBRX-106 in combination with Keytruda Out of five response evaluable patients with tumor types responsive to immunotherapy in the active dose range of INBRX-106 in combination with Keytruda, two durable partial responses were achieved in checkpoint inhibitor naïve nasopharyngeal carcinoma and uveal melanoma patients with duration greater than six months with treatment ongoing. Additionally, a third checkpoint inhibitor exposed cutaneous melanoma patient has a double-digit reduction in tumor volume and duration greater than four months with treatment ongoing. Part 2, which was run in parallel with Part 3, is ongoing and aimed at investigating single agent INBRX-106 dosed at 0.03 mg/kg in two different dosing schedules in patients with tumor types responsive to checkpoint inhibitors. Four of ten response evaluable non-small cell lung cancer (NSCLC) and melanoma patients receiving INBRX-106 in either Part 1 or 2 of the trial have been on treatment with INBRX-106 for at least six months. Of those four patients, three had previous exposure to checkpoint inhibitors and the fourth, a uveal melanoma patient, was checkpoint inhibitor naïve. To date, the longest duration on treatment with single agent
INBRX-106 is 90 weeks (approximately 21 months) and ongoing in a NSCLC patient refractory to Keytruda.