• Biomarkers
• Trifluridine/tipiracil
• Regorafenib
• Metastatic colorectal cancer

The regulatory approval of regorafenib and trifluridin/tipiracil has been supported by the findings from randomized controlled trials for the treatment of patients with metastatic colorectal cancer (mCRC) who have progressed following at least two previous lines of standard chemotherapy.
Regorafenib, a multitarget tyrosine kinase inhibitor, targets several angiogenic and stromal kinase receptors, VEGFR-1 (Vascular Endothelial Growth Factor), VEGFR-2, VEGFR-3, Fibroblast Growth Factor Receptor-1 (FGFR-1), Platelet Derived Growth Factor-Beta Receptor (PDGFR-B) and Tie-2.
Trifluridin/tipiracil is an oral drug which consists of the combination of an active drug, with an inhibitor (tipiracil); its triphosphate form is incorporated into DNA, with such incorporation appearing to result in its antitumor effects.
The present thesis focuses on the evaluation of circulating candidate markers as predictors of benefit from regorafenib and trifluridine/tipiracil (FTD/TPI) in chemorefractory metastatic colorectal cancer (mCRC) patients.
The REGOLAND study is a multicohort trial aiming at identifying and validating markers able to predict the efficacy of regorafenib in mCRC patients. Three patients’ cohorts were included in REGOLAND: the "regorafenib exploratory cohort" made of mCRC patients treated with regorafenib at the University Hospital of Pisa; the “regorafenib validation cohort” including patients treated with regorafenib in two Italian institutions (University Hospital of Pisa, and National Cancer Institute, Milan), and the “FTD/TPI cohort”, including patients who received triflurdine/tipiracil at University Hospital of Pisa, serving as control group.
In the “regorafenib exploratory cohort”, we preliminarily explored whether baseline plasma levels of candidate biomarkers and their dynamic modulation were correlated with clinical outcome. Then, based on a pre-specified statistical hypothesis, we prospectively challenged main retrospective findings in the “regorafenib validation cohort”. Finally, to clarify the reliability of prospectively validated putative biomarkers as predictors of benefit from regorafenib, we evaluated them an independent cohort of patients treated with FTD/TPI as a control group.
Results of another translational study aiming at assessing candidate markers in microvesicules-derived mRNA at the beginning of FTD/TPI or regorafenib in mCRC patients treated at the University Hospital of Pisa, are reported. The overall population was split in two groups: the “trifluridine/tipiracil cohort”, including patients treated with FTD/TPI and the “regorafenib cohort”, including patients who received regorafenib.
The first chapter of the present thesis describes the current landscape of the later lines of treatment of mCRC patients. The aim of this chapter is to provide the reader with a frame to properly understand the background of the design of this project.
The second chapter focuses on the lack of the optimal predictive markers of benefit from regorafenib and FTD/TPI and the unmet needs that the study attempted to address.
The third chapter reports the results of REGOLAND study providing a significant role for a pharmacodynamic determinant, the early increase of Angiopoietin-2 plasma levels, in predicting benefit from regorafenib in chemorefractory mCRC patients.
Finally, the fourth chapter describes the results of the second translational work showing that baseline microvesicles-derived mRNA expression of specific candidate markers are not useful as prognostic factors or predictive markers of benefit for trifluridine/tipiracil and regorafenib.