A Study to Evaluate the Safety and Efficacy of Two Dose Levels of ONO-4578 With Opdivo®, in Combination With mFOLFOX6 and Bevacizumab Versus Standard of Care in Participants With Non-MSI-H/dMMR, PD-L1 Positive Advanced Colorectal Cancer

Overall Response Rate (ORR) per Investigator assessment

ORR (assessed by site Investigator per RECIST v1.1) is defined as the proportion of participants with a BOR of confirmed CR or PR. The ORR will be estimated as the number of participants achieving BOR of CR or PR assessed by site Investigator per RECIST v1.1 divided by the total number of participants.

Time frame: From randomization to the end of treatment (Up to 39 months)

Overall Survival (OS)

OS is defined as the time between the date of randomization and the date of death due to any cause.

Time frame: From randomization to the end of treatment (Up to 39 months)

Progression-Free Survival (PFS) by BICR

PFS by BICR is defined as the time from date of randomization to the date of the first documented progressive disease (PD) as determined by BICR per RECIST version 1.1, or the date of death due to any cause, whichever occurs first.

Time frame: From randomization to the end of treatment (Up to 39 months)

Progression-Free Survival (PFS) by Investigator assessment

PFS by Investigator assessment is defined as the time from date of randomization to the date of the first documented progressive disease (PD) as determined by site Investigator per RECIST version 1.1, or the date of death due to any cause, whichever occurs first.

Time frame: From randomization to the end of treatment (Up to 39 months)

Best overall response (BOR) by BICR

BOR is defined as the best response designation, recorded between the start of the study intervention and the date of the initial objectively documented PD per RECIST v1.1 or the date of subsequent anti-cancer therapy, whichever occurs first.

Time frame: From randomization to the end of treatment (Up to 39 months)

Best overall response (BOR) by Investigator assessment

BOR is defined as the best response designation, recorded between the start of the study intervention and the date of the initial objectively documented PD per RECIST v1.1 or the date of subsequent anti-cancer therapy, whichever occurs first.

Time frame: From randomization to the end of treatment (Up to 39 months)

Duration of response (DOR) by BICR

DOR is defined as the time between the date of first confirmed CR or PR to the date of the first documented PD per RECIST v1.1 or death due to any cause, whichever occurs first.

Time frame: From randomization to the end of treatment (Up to 39 months)

Duration of response (DOR) by Investigator assessment

DOR is defined as the time between the date of first confirmed CR or PR to the date of the first documented PD per RECIST v1.1 or death due to any cause, whichever occurs first.

Time frame: From randomization to the end of treatment (Up to 39 months)

Disease Control Rate (DCR) by BICR

DCR is defined as the percentage of participants whose BOR is determined to be CR, PR, or stable disease (SD).

Time frame: From randomization to the end of treatment (Up to 39 months)

Disease Control Rate (DCR) by Investigator assessment

DCR is defined as the percentage of participants whose BOR is determined to be CR, PR, or stable disease (SD).

Time frame: From randomization to the end of treatment (Up to 39 months)

Time to Response (TTR) by BICR

TTR is defined as the time from the date of randomization to the date of first confirmed CR or PR.

Time frame: From randomization to the end of treatment (Up to 39 months)

Time to Response (TTR) by Investigator assessment

TTR is defined as the time from the date of randomization to the date of first confirmed CR or PR.

Time frame: From randomization to the end of treatment (Up to 39 months)

Maximum percent change in the sum of the diameters of the target lesions by BICR

In participants who have target lesions at baseline and at least 1 post-baseline imaging evaluation, the maximum percent change in the sum of diameters of target lesions is the percent change at the point of the minimum sum of diameters of the target lesions.

Time frame: From randomization to the end of treatment (Up to 39 months)

Maximum percent change in the sum of the diameters of the target lesions by Investigator assessment

In participants who have target lesions at baseline and at least 1 post-baseline imaging evaluation, the maximum percent change in the sum of diameters of target lesions is the percent change at the point of the minimum sum of diameters of the target lesions.

Time frame: From randomization to the end of treatment (Up to 39 months)

Progression-Free Survival of second line therapy (PFS2) by Investigator assessment

PFS2 is defined as the time from date of randomization to the date of an overall response of PD after subsequent anti-cancer therapy, initiating date of a second subsequent anti-cancer therapy, or date of death from any cause, whichever occurs first.

Time frame: From randomization to the end of treatment (Up to 39 months)