This is a Phase 2, randomized, double-blind placebo-controlled study of ompenaclid or matching placebo (Study Drug) in combination with standard-of-care FOLFIRI plus bevacizumab as background therapy in patients with previously treated RAS mutant advanced or metastatic CRC. Randomization will be stratified by whether or not the patient received prior treatment with bevacizumab or an EMA-approved biosimilar. Written informed consent must be obtained prior to initiating any screening activities, except where patients have agreed to the use of previously available tests completed within 28 days of the planned first dose of Study Drug, e.g., computed tomography (CT)/magnetic resonance imaging (MRI) scans. Screening for study eligibility must be completed within 28 days prior to first dose of Study Drug. Patients who are determined to be eligible, based on Screening assessments, will be randomized in the study, and receive their first dose of Study Drug on Cycle 1, Day 1. A treatment cycle is 28 days in duration. Patients will be randomized in a 1:1 ratio to receive oral administration of the five 600-mg tablets BID of ompenaclid or matching placebo (Study Drug). The intravenous FOLFIRI dose and schedule for all patients will be irinotecan 180 mg/m2 over 90 minutes concurrently with folinic acid 400 mg/m2 over 2 hours,followed by 5-FU 2400 mg/m2 over 46 hours, on Days 1 and 15 of each 28-day cycle. The bevacizumab dose of 5 mg/kg will be administered intravenously on Days 1 and 15 of each 28-day cycle. During treatment, patients will attend study center visits and have study evaluations performed as detailed in the Schedule of Events (Table 1-1). All routine study visits are to be conducted on an outpatient basis. Patients may continue to receive Study Drug until the development of PD, or another discontinuation criterion is met, including unacceptable toxicity, voluntary withdrawal from treatment, or closure of the study by the Sponsor; no maximum duration of therapy has been set. After discontinuation of the Study Drug, patients will complete an End of Treatment (EOT) visit within 21 days after their last dose of Study Drug. Safety follow-up is to be conducted by telephone 30 days (+/- 3 days) after their last dose of Study Drug and longer if drug-related AEs have not resolved at that time. Patients and/or their health care providers will also be contacted by telephone approximately every 90 days for information on evidence of PD in settings in which discontinuation of Study Drug was for reasons other than PD, such as an adverse event (AE) or investigator discretion, and/or for assessment of survival status (tumor measurements as specified in the protocol are not required after the EOT visit). This extended follow-up for disease status and survival after discontinuation of the Study Drug may continue until the target number of disease progression events have been observed or for 12 months after the patient's EOT visit, whichever is later. The End of Study for a given patient is defined as the date of the last extended follow-up disease/survival status, or until death, withdrawal of consent, loss to follow-up, or study closure, whichever occurs first.