A Study of [225Ac]-FPI-1966 in Participants With Advanced Solid Tumours

Key Inclusion Criteria: * Signed ICF prior to initiation of any study-specific procedures * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Histologically and/or cytologically documented diagnosis of locally advanced, inoperable, or metastatic solid tumours * Refractory to all standard treatments, or for whom standard treatment is not available, or tolerable, or is contraindicated, or the participant refuses standard therapy * Measurable disease per RECIST v. 1.1 * Available tumour tissue (archival or fresh biopsy) * Adequate bone marrow, heart, liver, and kidney function Key Exclusion Criteria: * Prior systemic radiopharmaceutical therapy within six months prior to the first dose of \[111In\]-FPI-1967 * Prior radiation therapy (RT) to bone marrow \> 20 Gy * RT within 30 days prior to the first dose of \[111In\]-FPI-1967 * Prior anti-cancer treatment (chemotherapy, immunotherapy, hormonal therapy, targeted therapy, or investigational agents) within a certain amount of time prior to administration of the first dose of \[111In\]-FPI-1967 * Concurrent serious co-morbidities that could limit participants' full participation and compliance