Overall Survival (OS)

mFOLFOX6 + Zolbetuximab

Participants received an IV infusion (as a minimum of 2-hour infusion) of zolbetuximab at a loading dose of 800 mg/m\^2 on C1D1 followed by subsequent doses of 600 mg/m\^2 every 3 weeks starting from C1D22 until participant meets study treatment discontinuation criteria. Participants also received up to 12 treatments of 5-fluorouracil, folinic acid and oxaliplatin (mFOLFOX6) (or components of mFOLFOX6 if some components were discontinued due to toxicity) over 4 or more cycles in which mFOLFOX6 was administered on Days 1, 15 and 29 of each cycle (5-fluorouracil administered by IV bolus 400 mg/m\^2 over 5 to 15 minutes followed by 2400mg/m\^2 over 46-48 hours continuous IV infusion every 2 weeks for 4 cycles. Folinic acid administered 400 mg/m\^2 IV infusion over 2 hours; oxaliplatin administered 85 mg/m\^2 IV infusion over 2 hours). A maximum of 12 doses of oxaliplatin was permitted. After mFOLFOX6 treatments, participants could continue to receive 5-FU and 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.

mFOLFOX6+ Placebo

Participants received an IV infusion (minimum 2-hour infusion) of placebo matched to zolbetuximab on C1D1, followed by subsequent doses every 3 weeks starting from C1D22 until study treatment discontinuation criteria were met. Participants also received up to 12 treatments of mFOLFOX6 (or components if some were discontinued due to toxicity) over 4 or more cycles. mFOLFOX6 was administered on Days 1, 15, and 29 of each cycle (5-fluorouracil: 400 mg/m\^2 IV bolus over 5-15 minutes followed by 2400mg/m\^2 over 46-48 hours continuous IV infusion every 2 weeks for 4 cycles. Folinic acid: 400 mg/m\^2 IV infusion over 2 hours; oxaliplatin: 85 mg/m\^2 IV infusion over 2 hours). A maximum of 12 doses of oxaliplatin was permitted. After mFOLFOX6 treatments, participants could continue to receive 5-FU and folinic acid on Days 1, 15, and 29 of each cycle at the investigator's discretion or until study treatment discontinuation criteria were met. Each cycle was approximately 42 days.

Analysis denominator · Participants

1. ci Lower Limit

   0.644

   ci Num Sides

   TWO_SIDED

   ci Pct Value

   95

   ci Upper Limit

   0.954

   group Ids

   1. OG000
   2. OG001

   non Inferiority Type

   SUPERIORITY

   p Value

   0.0075

   p Value Comment

   Log-rank test stratified by: * Region (Asia vs Non-Asia) * Number of organs with metastatic sites (0 to 2 vs ≥ 3) * Prior gastrectomy (Yes or No)

   param Type

   Hazard Ratio (HR)

   param Value

   0.784

   statistical Method

   Log Rank