Modeling high-risk pediatric cancers in zebrafish to inform precision therapy.

Despite advances in precision medicine, 30% of high-risk pediatric cancers lack an actionable molecular target, hindering effective treatment and impacting survival outcomes. While mouse patient-derived xenograft (PDX) models offer additional insights into clinical drug responses, delivering findings from these models within a clinically actionable timeframe remains challenging. This international collaboration between two national precision medicine programs demonstrates proof-of-principle that individualized larval zebrafish PDXs can robustly and rapidly assess clinical responses of high-risk child cancer patients. Retrospective zebrafish PDX testing was performed on tumor samples from ten pediatric patients with high-risk cancers. Drug responses in zebrafish models were correlated with clinical responses for each patient and directly compared with responses in cognate mouse PDX models. Responses to conventional and targeted therapies, administered as single agents or in combinations, were assessed. Zebrafish PDXs were successfully established from all ten patients and provided robust drug response data in every case, including from 3 patients whose tumor samples could not be engrafted in mice. Remarkably, zebrafish models accurately recapitulated patient responses for 11 of 12 treatment regimens. These findings highlight the potential of larval zebrafish PDX models to provide real-time, clinically relevant drug response data, supporting their potential use in prospective precision medicine studies.