Study of Anti-CEACAM5 ADC M9140 in Participants With Advanced Solid Tumors (PROCEADE PanTumor)

The PROCEADE PanTumor study aims to investigate M9140 in multiple tumor types which express carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) and it is therefore designed as a matrix study. This study aims to assess the antitumor activity, tolerability, safety, and pharmacokinetics (PK) of M9140 as monotherapy or in combination treatments in adult participants with locally advanced/metastatic CEACAM5 expressing tumors. There will be 3 substudies under this Master Protocol that may be conducted in parallel. * PROCEADE PanTumor: A Phase 1b/2, Multicenter, Open-Label Study of Anti-CEACAM5 Antibody-Drug Conjugate M9140 in Participants with Advanced Gastric Cancer (Substudy GC); * PROCEADE PanTumor: A Phase 1b/2, Multicenter, Open-Label Study of Anti-CEACAM5 Antibody-Drug Conjugate M9140 in Participants with Advanced Non-Small Cell Lung Cancer (Substudy NSCLC); * PROCEADE PanTumor: A Phase 1b/2, Multicenter, Open Label Study of Anti-CEACAM5 Antibody-Drug Conjugate M9140 in Participants With Advanced Pancreatic Cancer (Substudy PDAC).

Inclusion Criteria: * 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 (\= II) or a coronary revascularization procedure within 180 days of study entry. Calculated QTc average (using the Fridericia correction calculation) of \> 470 milliseconds (ms) * Cerebrovascular accident/stroke (\< 6 months prior to enrollment) * Other protocol defined exclusion criteria could apply Substudy GC - Participants with prior therapy with irinotecan Substudy NSCLC: \- Participants with prior therapy with irinotecan Substudy PDAC: none