ABSTRACT: Abstract The STARTRK-NG (Studies of Tumor Alterations Responsive to Targeting Receptor Kinases - Next Generation) trial is a Phase 1/1b study of entrectinib in pediatric patients with cancer, including primary brain tumors, neuroblastoma, and other non-neuroblastoma, extracranial solid tumors harboring NTRK, ROS1, or ALK gene fusions (NCT02650401). Entrectinib is a potent oral, CNS-penetrant, inhibitor of the tyrosine kinases TRKA/B/C (encoded by the genes NTRK1/2/3, respectively), ROS1, and ALK with IC50s < 2?nM (biochemical kinase assay). Overall, gene fusions are rare in the cancer population (<3%); however, they have been seen in over 40 solid tumor histologies, including non-small cell lung cancer, salivary gland cancers, soft tissue sarcomas and glioneuronal tumors. A survey of two pediatric cancer databases, St. Jude pediatric cancer database (PeCan; total n=1,604) and the University of Michigan database (Peds-MiOncoSeq; total n=91), identified malignancies with gene fusions in all three NTRK genes, including infantile fibrosarcoma, juvenile breast cancer, mesoblastic nephroma, intrinsic pontine gliomas, acute leukemias and anaplastic lymphoma. Previously, we reported an objective response rate of 79% was seen in 24 tyrosine kinase inhibitor-naïve patients with solid tumors harboring NTRK, ROS1, or ALK gene fusions, who were treated at doses consistent with the RP2D (Drilon et al, AACR 2016). The most common (>10% incidence) treatment-related adverse events have been fatigue/asthenia, dysgeusia, paresthesia, nausea, myalgia, diarrhea, dizziness, arthralgia, vomiting, and constipation; importantly, there has been no evidence of cumulative toxicity. In addition, we have treated a 20-month-old boy presenting with infantile fibrosarcoma metastatic to the brain, which harbored an ETV6-NTRK3 fusion. Tumor restaging following 1 month of therapy showed a significant tumor regression of CNS metastases accompanied by significant clinical improvement. Together, these data provide compelling evidence to identify pediatric patients harboring NTRK, ROS1, or ALK fusions for enrollment in the STARTRK-NG trial.
