Study of the CHK1 Inhibitor BBI-355, an ecDNA-directed Therapy (ecDTx), and the RNR Inhibitor BBI-825, in Subjects With Tumors With Oncogene Amplifications

Key Inclusion Criteria: * Locally advanced or metastatic non-resectable solid tumors, whose disease has progressed despite all standard therapies or for whom no further standard or clinically acceptable therapy exists, * Evidence of oncogene amplification, * Availability of FFPE tumor tissue, archival or newly obtained, * Measurable disease as defined by RECIST Version 1.1, * Adequate hematologic function, * Adequate hepatic and renal function, * Eastern Cooperative Oncology Group performance status (ECOG PS) 0 or 1, * Other inclusion criteria per study protocol. Key Exclusion Criteria: * Single agent arm: Prior exposure to CHK1 or WEE1 inhibitors, * BBI-355 combination with BBI-825 arm: Prior exposure to combination therapy of any RNR inhibitor plus CHK1/2 inhibitor, * Hematologic malignancies, * Primary CNS malignancy, leptomeningeal disease, or symptomatic active CNS metastases, with exceptions per study protocol, * Prior or concurrent malignancies, with exceptions per study protocol, * History of HBV, HCV, or HIV infection, * Clinically significant cardiac condition, * Active or history of interstitial lung disease (ILD) or pneumonitis, or history of ILD or pneumonitis requiring steroids or other immunosuppressive medications, * QTcF \> 470 msec, * Prior organ allograft transplantations or allogeneic peripheral blood stem cell/bone marrow transplantation, * Other exclusion criteria per study protocol.