Larotrectinib, a highly selective TRK kinase inhibitor, shows rapid, potent, and durable efficacy in both adult and pediatric patients with solid tumors that harbor TRK fusions, regardless of tumor type or patient age, according to results from three clinical trials published in the New England Journal of Medicine. The landmark data support the foundation of precision oncology by creating a treatment option for a genetically defined cancer while continuing to validate the concept that comprehensive molecular profiling should be strongly considered in people of all ages with advanced solid tumors.