A Study in People With Advanced Extrapulmonary Neuroendocrine Cancer to Compare Obrixtamig Plus Carboplatin and Etoposide Treatment With Standard Chemotherapy

Inclusion Criteria

• •1. Patients with poorly differentiated unresectable locally advanced or metastatic extrapulmonary neuroendocrine carcinoma (epNEC) with Ki-67 \>20% or mitotic rate mitotic rate with number of mitoses \>20 per 2 mm2, regardless of primary site (including site of unknown origin)
• •2. Patients with tumours with mixed histologies are eligible only if neuroendocrine carcinoma component is predominant and represents more than 70% of the overall tumour tissue
• •3. No prior systemic treatment for unresectable locally advanced or metastatic epNEC (except for the completed one cycle of standard platinum + etoposide). Prior peri-operative chemotherapy or -radiation for curative intention is allowed if at least 6 months have elapsed between completion of this therapy and diagnosis of unresectable locally advanced or metastatic disease
• •4. Patients who have finished one cycle of standard platinum + etoposide regimen as first-line treatment (Cycle 0: etoposide with carboplatin or cisplatin, administered at a minimum dose of cisplatin 75 mg/m2 or carboplatin area under the curve (AUC) 5 and etoposide 80 mg/m2) prior to randomisation
• •5. Patients must comply with criteria for receiving further chemotherapy treatment as first-line standard of care (SoC) treatment within 28 days after the start of the initial chemotherapy (Cycle 0)
• •6. Adequate archival Formalin-Fixed Paraffin-Embedded (FFPE) tumour tissue, as specified in the Laboratory Manual, must be available for central laboratory analysis of Delta-like ligand 3 (DLL3) expression status. Tumours must be positive (as defined in the diagnostic study protocol) for DLL3 expression status assessed by investigational VENTANA DLL3 (SP347) RxDx Assay
• •7. Eastern Cooperative Oncology Group (ECOG) score of 0 or 1