A Study of [225Ac]-FPI-2059 in Adult Participants With Solid Tumours

Key Inclusion Criteria: * Signed ICF prior to initiation of any study-specific procedures * Histologically and/or cytologically confirmed solid tumor that is metastatic or locally advanced, inoperable, or recurrent. Solid tumors indications may include PDAC, CRC, NED prostate cancer, gastric cancer, SCCHN, and Ewing sarcoma. * Disease that has progressed despite prior treatment, and for which additional effective standard therapy is not available or is contraindicated, not tolerable, or the patient refuses standard therapy * Measurable disease per RECIST v.1.1 * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Sufficient target expression in at least one measurable lesion as determined by imaging following injection of \[111In\]-FPI-2058 * Adequate organ function * Tumor tissue (either archival within the last 24 months or fresh biopsy) Key Exclusion Criteria: * Previous treatment with any radiopharmaceutical * Contraindications to or inability to perform the imaging procedures required in this study * Anti-cancer therapy, such as chemotherapy, immunotherapy, hormonal therapy, targeted therapy, or investigational agents within certain amount of time prior to administration of the first dose of \[111In\]-FPI-2058 * Radiation therapy (RT) within 28 days prior to the first dose of \[111In\]-FPI-2058 * Patients with known CNS metastatic disease * Concurrent severe and/or uncontrolled illness that would limit compliance with study requirements * Known or suspected allergies or contraindication to the investigational treatment * Received any type of vaccine within 30 days prior to the first dose of \[111In\]-FPI-2058