Decision was made to halt the study based on overall clinical experience and market considerations. This decision was not driven by any safety signal.

BBI-355 is an oral, potent, selective checkpoint kinase 1 (or CHK1) small molecule inhibitor in development as an ecDNA (extrachromosomal DNA) directed therapy (ecDTx). BBI-825 is an oral, potent, selective ribonucleotide reductase (or RNR) small molecule inhibitor. This is a first-in-human, open-label, 2-part, Phase 1/2 study to determine the safety profile and identify the maximum tolerated dose and recommended Phase 2 dose of BBI-355 administered as a single agent or in combination with BBI-825 or other select therapies.

BBI-355 and BBI-825 are administered orally in various dosing schedules to subjects with locally advanced or metastatic non-resectable solid tumors harboring oncogene amplifications, whose disease has progressed despite all standard therapies or for whom no further standard or clinically acceptable therapy exists.

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.