Part 1- M0324 Monotherapy: • Participants with certain advanced/metastatic solid tumor types known to overexpress MUC-1 and who are intolerant or refractory to standard therapy or for which no standard therapy is judged appropriate by the Investigator Part 2- M0324 Combination with Pembrolizumab: • Participants with certain advanced/metastatic tumor types known to overexpress MUC-1 and the participants in the combination treatment involving M0324 and pembrolizumab must be intolerant or refractory to standard therapy and no other further standard therapy should be judged appropriate by the Investigator. In addition, the participants must have had prior treatment with immune checkpoint inhibitor(s) (ICIs) and must have experienced documented disease progression on or after ICIs. Part 3- M0324 Combination with mFOLFIRINOX: - Participants with previously untreated metastatic pancreatic ductal adenocarcinoma, who are judged by Investigator as eligible for treatment with mFOLFIRINOX. Participants with prior Whipple surgery and/or adjuvant chemotherapy are not permitted - Other protocol defined inclusion criteria could apply

• Has a history of chronic diarrhea greater than or equal to (>=) Grade 2, inflammatory disease of the colon or rectum, or unresolved partial or complete intestinal obstruction - Participant has a history of malignancy within 3 years before the date of enrollment - Uncontrolled or poorly controlled arterial hypertension, uncontrolled cardiac arrhythmia, unstable angina, myocardial infarction, congestive heart failure [New York Heart Association (NYHA) >= II] or a coronary revascularization procedure within 180 days of study entry - Life expectancy of less than 3 months - Other protocol defined exclusion criteria could apply