Dose Optimization and Efficacy Assessment of a Fluoropyrimidine Antidote

Inclusion Criteria: Presence of at least one severe toxicity or intoxication resulting from fluoropyrimidine use, defined as: receiving an overdose of medication (total dose and/or infusion rate higher than recommended in the package insert) and/or Grade 3 or 4 serious adverse events after fluoropyrimidine exposure, according to CTCAE v5.0, which may include (but are not limited to): nausea, vomiting, diarrhea, anemia, neutropenia, febrile neutropenia, thrombocytopenia, and mucositis; Lack of access to uridine triacetate (UT) in the standard of care; Diagnosis of an invasive solid tumor under systemic treatment with a fluoropyrimidine (5-fluorouracil or capecitabine); Organ function considered adequate by the investigator prior to the current fluoropyrimidine intoxication episode; Ability to take oral medication; For men and women of reproductive potential, agreement to practice abstinence or use highly effective contraceptive methods during study participation and for at least 6 months after the last dose of IP; Men must agree not to donate sperm for at least 6 months after the last dose of IP; Body surface area between 1.4 and 2.4 m², calculated using the Du Bois method; AST/ALT within normal limits for participants without liver metastases; AST/ALT up to 3x the upper limit of normal in participants with liver metastases; Total and fractionated bilirubin up to 2x the upper limit of normal; Agreement to abstain from alcohol consumption during the treatment period…