Hong DS, DuBois SG, Kummar S, et al. - Given larotrectinib (a selective TRK inhibitor) got approval as a treatment option for advanced TRK fusion-positive solid tumours in paediatric and adult patients, based on a primary analysis set of 55 patients, researchers tested its efficacy as well as long-term safety in a larger population of patients having TRK fusion-positive solid tumours. Eligibility criteria for this pooled analysis were: age 1 month or older, a locally advanced or metastatic non-CNS primary, TRK fusion-positive solid tumour, had received standard therapy previously if available. The 55 patients on which approval of larotrectinib was based were also a part of this study. Larotrectinib was delivered orally (capsule or liquid formulation), on a continuous 28-day schedule, mostly at a dose of 100 mg twice daily to adult patients, and mostly at a dose of 100 mg/m² (maximum of 100 mg) twice daily to paediatric patients. There were 153 evaluable patients, of those, the proportion exhibiting an objective response as per investigator evaluation was 121. Complete responses were seen in 24 (16%). Raised alanine aminotransferase, anaemia, and reduced neutrophil count were the grade 3 or 4 larotrectinib-related adverse events that occurred most commonly, as revealed in a safety population including 260 patients treated irrespective of TRK fusion status. A unique molecular subgroup of advanced solid tumours for which a high activity of larotrectinib was evident, was defined by TRK fusions, as corroborated by the findings. According to the safety data, it is feasible to administer larotrectinib for long-term.