• Participants are capable of signing informed consent as defined in protocol

• Eastern Cooperative Oncology Group Performance Status (ECOG PS) below or equal to 1

• Participants with adequate hematologic, hepatic and renal function as defined in protocol

• Participant must have at least 1 lesion that is measurable using RECIST v1.1.

• Other protocol defined inclusion criteria could apply

⁃ Substudy GC:

• Participants in Part A and Part B with documented histopathological diagnosis of advanced or metastatic, HER2 negative, gastric or GEJ (with an epicenter 2 centimeter (cm) proximal or distal to the GEJ) adenocarcinoma, who were intolerant/refractory to or progressed after systemic therapies for the advanced/metastatic stage that must have included (provided there is no medical contraindication and these agents are locally approved and available) a fluoropyrimidine and a platinum agent and an Immune checkpoint inhibitors (ICI) for participants with a known microsatellite instability-high (MSI-H) status or participants whose tumor express PD-L1 with a CPS greater than or equal (\>=) 1

• Participants must have received and progressed (according to RECIST 1.1) on at least 1 line of therapy for the treatment of advanced/metastatic disease but no more than 2

• Participants in Part A with CEACAM5high GC/GEJC (defined as IHC \>= 2+ staining in \>= 50% of tumor cells)

• Participants in Part B with CEACAM5low GC/GEJC (defined as IHC \>= 2+ staining in less than (\<) 50% of tumor cells)

• Other protocol defined inclusion criteria could apply

⁃ Substudy NSCLC:

• Participants in Part A and Part B with histologically or cytologically documented advanced (Stage III not eligible for resection or curative radiation) or metastatic NSCLC with or without driver genomic alterations

• Participants must have been intolerant/refractory to or progressed after systemic therapies for the advanced/metastatic stage

• Participants must have received and progressed (according to RECIST 1.1) on at least 1 line of therapy for the treatment of advanced/metastatic disease but no more than 3

• Participants who received a platinum-containing regimen or a targeted therapy as (neo)-adjuvant therapy for early-stage disease, if relapse or metastases occurred during or within 3 months after regimen completion, are considered to have received a line of treatment in the advanced setting

• Participants in Part A with CEACAM5 high-expressing EGFR tumors (including participants with any driver genomic alterations other than EGFR mutations

• Participants in Part B with CEACAM5 high known EGFR mutated tumors as assessed according to local clinical practice

• Other protocol defined inclusion criteria could apply

⁃ Substudy PDAC:

• Participants with histologically or cytologically confirmed advanced or metastatic PDAC, who were intolerant/refractory to or progressed after systemic therapies for the advanced metastatic stage that must have included (provided there is no medical contraindications, and these agents are locally approved and available; FOLFIRINOX regimen or NALIRIFNOX regimen or Nab-paclitaxel/gemcitabine regimen

• Participants must have received and progressed (according to RECIST 1.1) on at least one 1 line of therapy for the treatment of advanced/metastatic disease but no more than 2

• All participants will be screened using an IHC test to define CEACAM5 expression. Only participants with CEACAM5high expressing tumors will be eligible

• Other protocol defined inclusion criteria could apply