INTRACOLOR is a genetic and epigenetic study of intratumoral heterogeneity dynamics in colorectal cancer (CRC). The research was run in parallel to Phase I/II MoTriColor trials (ID: 635342), which assessed a novel targeted strategy for mCRCm (MoTriColor study). This framework was a unique opportunity to evaluate paired samples to identify molecular differences in primary vs metastatic samples and the acquisition of resistant clones. The study has allowed us to generate highly valuable preclinical models in mice (PDX– patient-derived xenografts) based on samples from patients treated in the MoTriColor study, based in immunotherapy plus antiangiogenic clinical combo therapy. As a summary, 55 paired tissue samples were analysed and 13 PDX models were generated from samples directly obtained from these patients, which led us to the corresponding Clinical Trial Associated Xenograft (CTAX) models. After exhaustive analysis of evolutive disease outcomes, one of the main outputs was the discovery of new potentially targeted alterations for a molecular subpopulation of mCRC patients, including a fusion in NTRK oncogene, in addition to a hypermutant MSI genome profile.The model showed response to NTRK inhibitors with mice presenting complete responses. Furthermore, the generated PDX/ CTAX models will be further used to identify new mechanisms of resistance and sensitivity to the proposed therapy in other prospective projects.