Neurotrophic tropomyosin receptor kinase (NTRK) gene fusion has been identified in various pediatric malignancies1. Larotrectinib is a highly selective small-molecule inhibitor targeting all three TRK proteins. Although some trials have demonstrated impressive responses to larotrectinib2,3, most cancers develop resistance to it over time. Herein, we report two rare cases of pediatric solid tumors that were resistant to larotrectinib via an off-target mechanism for the first time.