A Phase I Study of [225Ac]-AZD2284 in Patients With Metastatic Castration-Resistant Prostate Cancer

* Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.

* Histologically confirmed diagnosis of adenocarcinoma of the prostate or neuroendocrine differentiated prostate cancer.

* Must have had prior bilateral orchiectomy and/or ongoing androgen-deprivation therapy and a castrate level of serum/plasma testosterone (< 50 ng/dL or < 1.7 nmol/L).

* At least one metastatic lesion present on baseline Computed Tomography (CT), Magnetic Resonance Imaging (MRI), or bone scan obtained ≤ 28 days prior to the first dose of Investigational Medicinal Product (IMP). Participants may have non-measurable lesions including bone only metastases.

* Adequate organ function

* Treatment with any radiopharmaceutical within 6 weeks of the first dose of Investigational Medicinal Product (IMP).

* Radiation therapy (RT) within 28 days prior to the first dose and all RT-related events have not recovered to Grade ≤ 1.

* Administration of any systemic cytotoxic or investigational therapy ≤ 28 days of the first dose of IMP or 5 half-lives, whichever is shorter.

* All prior treatment-related adverse events must have resolved to Grade ≤ 1.

* Concurrent severe and/or uncontrolled illness not related to cancer and/or social situation that would limit compliance with study requirements.

* Known or suspected allergies or contraindications to any of the investigational drugs or any component of the investigational drug formulation.

* Clinically relevant proteinuria