This study is open to adults with advanced extrapulmonary neuroendocrine cancer. The purpose of this study is to find out if a study medicine called obrixtamig plus standard chemotherapy (carboplatin and etoposide) improves survival when compared to standard chemotherapy (carboplatin and etoposide) alone. Obrixtamig is an antibody-like molecule that may help the immune system fight cancer. Another purpose of the study is to test a medical device being developed to measure levels of the tumour marker delta-like ligand 3 (DLL3).
Participants are put into 2 groups randomly, which means by chance. One group (treatment arm) receives obrixtamig and standard chemotherapy followed by obrixtamig alone for up to 3 years. The other group (control arm) receives standard chemotherapy without obrixtamig for about 4 months. All treatments are given as infusions into a vein.
During the study, participants in both groups visit the study site regularly. Participants in the treatment arm stay overnight at the study site following the first 2 obrixtamig treatments. The doctors regularly check participants' health and take note of any unwanted effects. At some of the visits, doctors check the size of the tumour(s). The results are compared between the 2 groups to see whether the treatment works.
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)
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
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
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
Presence of leptomeningeal disease and/or carcinomatous meningitis
Patients with diagnosis of Merkel cell carcinoma or medullary thyroid carcinoma
Patients with neuroendocrine prostate cancer
Patients with well-differentiated neuroendocrine tumours of any grade according to the world health organization (WHO) classification, 5th edition