G1T38, a CDK 4/6 Inhibitor, in Combination With Osimertinib in EGFR-Mutant Non-Small Cell Lung Cancer

Inclusion Criteria: * Confirmed EGFR mutation for non-small cell lung cancer associated with EGFR TKI sensitivity * For Part 2, EGFR T790M mutation-positive tumor status * Left ventricular ejection fraction (LVEF) ≥ institution's lower limit of the reference range * For Part 1, evaluable or measurable disease as defined by RECIST, Version 1.1 * For Part 2, measurable disease as defined by RECIST, Version 1.1 * ECOG performance status 0 to 1 * Adequate organ function Exclusion Criteria: * Prior treatment with EGFR TKI within 9 days of first study dose * For Part 1, prior treatment with more than 2 prior lines of chemotherapy for advanced NSCLC * For Part 2, prior treatment with osimertinib or other T790M active EGFR TKI * For Part 2, prior chemotherapy for advanced NSCLC * Active uncontrolled/symptomatic CNS metastases, carcinomatous meningitis, or leptomeningeal disease * Investigational drug within 3 months or 5 half-lives, whichever is longer, of first study dose * Concurrent radiotherapy, radiotherapy within 28 days of first study dose, previous radiotherapy to the target lesion sites, or prior radiotherapy to \> 25% of bone marrow * Prior hematopoietic stem cell or bone marrow transplantation