NTRK1 and cancer: The recent development of anti-programmed cell death-1 (PD-1) antibodies, pembrolizumab (Keytruda) and nivolumab (Opdivo), and a pan-tropomyosin receptor kinase (TRK) inhibitor, larotrectinib (LOXO-101), has established a new paradigm in anti-cancer drug development.