9e (Larotrectinib) is a highly selective TRK inhibitor developed by Loxo Oncology in collaboration with Bayer AG for the treatment of adult and pediatric patients with NTRK gene fusion-positive cancers, with IC50 of 1–20 nM for inhibition of TRKA, B, and C [159,163]. The gene discussed is NTRK1; the disease is cancer.