A Study of SGN-MesoC2 in Advanced Solid Tumors

Inclusion Criteria: * Aged 18 years or older. * Histologically- or cytologically-confirmed metastatic or locally advanced unresectable platinum-resistant ovarian cancer, NSCLC, pancreatic ductal adenocarcinoma, endometrial cancer, colorectal cancer, or mesothelioma, who have relapsed or progressed following standard therapies, or for which no standard therapies are available. * An Eastern Cooperative Oncology Group performance status score of 0 or 1. * At least 1 measurable lesion at baseline based on Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST v1.1). * Archival tumor tissue or a fresh tumor biopsy during the screening period. * Adequate hepatic, renal and bone marrow function. * Participants must not have received more than 2 lines of cytotoxic systemic therapy in the metastatic setting (Parts B and C only). Exclusion Criteria: * Previously received or currently receiving any systemic anticancer therapy or focal radiotherapy within 4 weeks prior to the first dose of MesoC2 or within 2 weeks prior to the first dose of MesoC2 if the underlying disease had progressed on treatment. * Prior anti-MSLN antibody or MSLN-directed ADC (Part C only). * Unresolved toxicities from prior therapy greater than NCI CTCAE v5.0 grade 1 at the time of study treatment (except alopecia). * Inadequate hepatic dysfunction, renal function, or hematologic abnormalities. * Previously untreated brain metastases. Participants who received radiation or surgery for brain metastases are eligible if therapy was completed at least 4 weeks prior to study treatment initiation, and there was no evidence of central nervous system progression nor requirements for chronic corticosteroid therapy