Adverse events

Participants received an IV infusion (as a minimum of 2-hourinfusion) ofzolbetuximab at a loading dose of 800mg/m\^2 on C1D1followed by subsequent doses of 600 mg/m\^2every 3 weeks starting from C1D22 until participant meets study treatment discontinuation criteria .Each cycle wasapproximately 42 days.

Participants received up to 12 treatments of5-fluorouracil over 4 or more cycles administered by IV bolus 400 mg/m\^2 over5 to 15 minutes followed by 2400mg/m\^2 over46-48 hours continuous IV infusion every 2weeks for 4 cycles. Participants could continue to receive 5-fluorouracil on Days 1,15 and 29 of each cycle at the investigator's discretion or until the participant met the study treatment discontinuation criteria. Each cycle was approximately 42 days.

Participants received up to 12 treatments of folinic acid administered 400mg/m\^2 IV infusion over 2 hours 4 or more cycles on Days 1, 15 and29 of each cycle. Participants could continue to receive folinic acid on Days 1,15 and 29 of each cycle at the investigator's discretion or until the participant met the study treatment discontinuation criteria. Each cycle was approximately 42 days.

Participants received up to 12 treatments of oxaliplatin administered 85 mg/m\^2 IV infusion over 2 hours) on Days 1,15 and 29 of each cycle.. A maximum of 12 doses of oxaliplatin was permitted. Each cycle was approximately 42days.

Participants received anIV infusion (as a minimum of 2-hourinfusion) of placebo matched to zolbetuximab on C1D1followed by subsequent doses every 3 weeks starting from C1D22until participant met study treatment discontinuation criteria. Each cycle was approximately 42 days.