NEPC Study: An Exploratory Safety and Efficacy Study With PSMA, SSTR2 and GRPR Targeted Radioligand Therapy in Metastatic Neuroendocrine Prostate Cancer.

Key Inclusion criteria:

* Participants must have metastatic prostate cancer with neuroendocrine differentiation as determined by at least one of the following:

1. Histologically small cell or neuroendocrine cancer from a primary prostate or metastatic biopsy confirmed by local laboratory.
2. Expression of NEPC markers (e.g., chromogranin or synaptophysin) in tumor tissue by IHC confirmed by local laboratory
3. Progression of visceral metastases in the absence of PSA progression
4. Serum chromogranin A \> 5x normal limit, or neuron-specific enolase \> 2x normal limit with control for proton-pump inhibitors (PPI) drugs among concomitant treatment
5. Prostate adenocarcinoma with molecular features of neuroendocrine differentiated cancer (e.g., 2 of the following 3: PTEN, TP53, or RB loss)
* PSMA and/or SSTR2 and/or GRPR PET-positive participants, with at least one measurable lesion per RECIST 1.1 with moderate target expression in at least one of the 3 PET/CT scans per BICR assessment
* Castrate level of serum/plasma testosterone (\< 50 ng/dl, or \< 1.7 nmol/L) for participants with adenocarcinoma component or stable testosterone level for participants with pure neuroendocrine carcinoma
* Recovered to ≤ Grade 2 from all clinically significant toxicities related to prior therapy
* Participant has adequate bone marrow and organ function (as assessed by central laboratory for eligibility)
* ECOG status =\< 2

Key Exclusion criteria:

* Previous treatment with any of the following within 6 months prior to Screening: Strontium-89, Samarium-153, Rhenium-186, Rhenium-188, Radium-223, hemi-body irradiation
* Previous PSMA, SSTR2, or GRPR targeted radioligand therapy
* Other concurrent cytotoxic chemotherapy, immunotherapy, radioligand therapy or investigational therapy
* History of CNS metastases that are neurologically unstable, symptomatic, or receiving corticosteroids for the purpose of maintaining neurologic integrity
* Symptomatic cord compression, or clinical or radiologic findings indicative of impending cord compression
* History or current diagnosis of ECG abnormalities indicating significant risk of safety for study participants

Other protocol-defined inclusion/exclusion criteria may apply.