Time frame: DLTs will be collected from C1D1 to C1D21 of NT219 plus pembrolizumab
DLT is defined as any of the following occuring during Cycle 1 of NT219 administered in combination with pembrolizumab: Grade >=3 non-hematologic toxicity, Grade >=4 neutropenia >7 days, Grade >=3 thrombocytopenia with clinically significant bleeding, neutropenic fever, any Hy's law case (AST or ALT >3 x ULN AND total bilirubin >2x ULN AND alk phos <2x ULN AND no other reason for liver injury), and any death not clearly due to underlying disease or extraneous causes. The following Grade >=3 non-hematologic toxicities are NOT considered DLTs: Grade 3 nausea, vomiting, or diarrhea <72 hours with adequate antiemetic and other supportive care; Grade 3 fatigue lasting <7 days; Grade >=3 or higher electrolyte abnormalities lasting up to 72 hours which are not clinically complicated and resolve spontaneously or respond to conventional medical interventions; Grade 3 amylase or lipase elevation not associated with symptoms or clinical manifestations of pancreatitis.