TRLS-12. EFFICACY AND SAFETY OF ENTRECTINIB IN CHILDREN WITHNTRK ORROS1 FUSION-POSITIVE (FP) PRIMARY CENTRAL NERVOUS SYSTEM (CNS) TUMORS

Abstract

Abstract BACKGROUND Entrectinib (CNS-penetrant, TRK/ROS1 inhibitor) has shown efficacy and safety in children with NTRK/ROS1-fp CNS tumors. We present updated data from an integrated analysis of children with NTRK/ROS1-fp CNS tumors enrolled in three early-phase trials: STARTRK-NG (NCT02650401), TAPISTRY (NCT04589845) and STARTRK-2 (NCT02568267). METHODS TRK/ROS1 inhibitor-naïve patients <18 years old (YO) with NTRK/ROS1-fp CNS tumors with measurable/evaluable-only disease, who received ≥1 entrectinib dose before disease progression, unacceptable toxicity, or consent withdrawal, and with ≥6 months’ follow-up were efficacy evaluable. Any <18 YO on study who received ≥1 entrectinib dose, regardless of genetic alteration and follow-up duration, was evaluable for safety. Primary endpoint: blinded independent central review (BICR)-assessed confirmed objective response rate (ORR). Key secondary endpoints: BICR-assessed confirmed ORR in patients with measurable disease; duration of confirmed response (DoR); time to confirmed response (TtR); progression-free survival (PFS); safety. RESULTS On 16 July 2023 (cut-off for analysis), 27 patients were efficacy evaluable (NTRK-fp: n=20; ROS1-fp: n=7). Median age at enrolment: 4.0 Y (NTRK-fp) and 6.0 Y (ROS1-fp); 45.0% (NTRK-fp) and 42.9% (ROS1-fp) of patients received ≥2 prior therapy lines. Median survival follow-up: 26.2 months (NTRK-fp); 36.1 months (ROS1-fp). ORR: 50.0% (NTRK-fp) and 71.4% (ROS1-fp) in efficacy-evaluable patients, and 58.8% (n=10/17; NTRK-fp) and 83.3% (n=5/6; ROS1-fp) in patients with measurable disease. Median DoR: 25.4 months, TtR: 1.9 months, PFS: 23.1 months in NTRK-fp patients. DoR and PFS were not evaluable in ROS1-fp patients; median TtR was 1.9 months. In the safety-evaluable population (N=34), the most common adverse events were weight increase (50.0%), blood creatinine increase and anemia (each 41.2%). Bone fractures were reported in 26.5% of patients. Most fractures occurred in children 2–12 YO (n=7/9). CONCLUSIONS Our analysis confirms the rapid and durable activity of entrectinib in children with NTRK/ROS1-fp primary CNS tumors. The safety profile described was in line with previous reports.