High-dose short-term osimertinib treatment is effective in patient-derived metastatic colorectal cancer organoids

Abstract Background Despite major interest in tyrosine kinase inhibitors (TKIs) as a treatment option for metastatic colorectal cancer (mCRC), almost all TKIs tested for mCRC fail in early-phase clinical trials. Although showing specific target inhibition at low concentrations, TKIs have a much broader kinase inhibitory potency at higher concentrations. In an attempt to leverage these many additional, low-affinity targets, high-dose regimens that may trigger efficacy are explored. Here, we studied unprecedented drug exposure–response relationships in vitro using mCRC patient-derived tumour organoids (PDTOs). Methods We established patient-derived tumor organoids (PDTOs) from mCRC biopsies and, based on favorable physicochemical and pharmacokinetic properties, selected 3 TKIs (sunitinib, cediranib and osimertinib). Following standard IC50 assessment using continuous dosing with a concentration range, we investigated the cytotoxic antitumor effect of high-dose, short-term (HDST) treatment. Five PDTOs were exposed to 20 µM TKI for 1–24h, washed and given normal medium, and PDTO-outgrowth was determined 1 week later. At exposures of 1, 3 and 6 h, we measured intra-tumoroid TKI concentrations using a clinically validated LC/MS-MS method. PDTO cell death was observed using live-cell microscopy, and quantified by both caspase 3/7 enzyme activity assay and cleaved caspase-3 immunofluorescent staining. Results We show that most PDTOs tested are sensitive to multikinase TKIs sunitinib and cediranib, and all to osimertinib. Furthermore, we demonstrate that high-dose, short-term(HDST) TKI treatment effectively blocks organoid growth. In line with recent clinical data of high-dose sunitinib tumour accumulation, HDST treatment led to markedly elevated intra-tumoroid TKI concentrations, which correlated with PDTO sensitivity. This suggests exposure-dependent cytotoxicity and supports the concept that efficacy is induced by a broad kinase inhibitory spectrum. Mechanistically, HDST osimertinib treatment for just 3 hours induced regulated cell death in treated organoids. Conclusion Our work provides a better understanding of TKI exposure vs response and can be used to determine patient-specific sensitivity. In addition, these results may guide both mechanistic elucidation in organotypic translational models and the translation of target drug exposure to clinical dosing strategies. Moreover, HDST osimertinib treatment warrants clinical exploration for mCRC.