A Phase 2 Clinical Trial Evaluating the Efficacy and Safety of Dual Immune Checkpoint Inhibition With Anti-PD-L1 (Atezolizumab) and Anti-TIGIT (Tiragolumab) in Cancer of Unknown Primary

Inclusion Criteria: ● Patients must have histopathological confirmed unresected, locally advanced, recurrent, or metastatic CUP. Patients must have undergone standard work-up to attempt to find the primary tumor prior to enrollment. Patients must be refractory or intolerant to at least one line of systemic chemotherapy or ineligible for cytotoxic chemotherapy. * Patients must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded for nonnodal lesions and short axis for nodal lesions) as ≥20 mm (≥2 cm) by chest x-ray or as ≥10 mm (≥1 cm) with CT scan, MRI, or calipers by clinical exam. * Age ≥18 years. Because no dosing or adverse event data are currently available on the use of tiragolumab in combination with atezolizumab in patients \<18 years of age, children are excluded from this study. * ECOG performance status of 0-1. * Patients must have adequate organ and marrow function as defined below: * ANC \> 1.5 x 109 /L (1500/L) without granulocyte colony-stimulating factor support. * Lymphocyte count \> 0.5 x 109 /L (500/L). * Platelet count \> 100 x 109 /L (100,000/L) without transfusion. * Hemoglobin \> 90 g/L (9 g/dL). * Patients may be transfused to meet this criterion. * AST, ALT, and ALP \< 2.5 x upper limit of normal (ULN). * Total bilirubin \< 1.5 x ULN with the following exception: * Patients with known Gilbert disease: total bilirubin \< 3 x ULN. * Creati…