NTRK1 and neoplasm: Finally, experiments combining agonistic activation of Trk with amitriptyline (binding at the extracellular domain) and Trk inhibition with entrectinib (binding the intracellular kinase domain) revealed that there was a small but also systematic blocking effect detectable at 60 min post-injection of radiotracer [18F]TRACK in both KM12 tumor tissue (Δ8%) and BAT (Δ14%).