Sonesitatug Vedotin in Combination With Capecitabine With or Without Rilvegostomig in Participants With Advanced or Metastatic Gastric, Gastroesophageal Junction, or Esophageal Adenocarcinoma Expressing Claudin18.2

Inclusion Criteria

• •Capable of giving signed informed consent
• •Participant must be 18 years or the legal age of consent in the jurisdiction in which the study is taking place, at the time of signing the informed consent.
• •Previously untreated histologically documented unresectable, locally advanced, or metastatic gastric, GEJ, or distal esophagus (distal third of the esophagus) adenocarcinoma
• •Positive CLDN18.2 expression, as determined prospectively by central IHC testing
• •Confirmed PD-L1 CPS status by central IHC testing and ICI eligibility per investigator judgement is required to determine cohort eligibility as described below:
• •1. Cohort 1: PD-L1 positive as determined by central IHC testing and the participant is deemed ICI eligible per investigator judgement.
• •2. Cohort 2: PD-L1 negative as determined by central IHC testing OR the participant is ICI ineligible
• •ECOG performance status of 0 or 1 with no deterioration to \> 1 over the previous 2 weeks prior to baseline at screening and prior to randomisation.
• •Minimum life expectancy of ≥ 12 weeks.
• •At least one lesion (measurable and/or non-measurable) that can be accurately assessed by the investigator based on RECIST 1.1.
• •Adequate organ and bone marrow function as specified in the protocol
• •Body weight ≥ 35 kg.
• •Sex and contraceptive requirements