Trilaciclib (G1T28), a CDK 4/6 Inhibitor, in Combination With Etoposide and Carboplatin in Extensive Stage Small Cell Lung Cancer (SCLC)

Inclusion Criteria: * Male or female subjects aged ≥18 years * Unequivocally confirmed diagnosis of SCLC by histology or cytology, preferably including the presence of neuroendocrine features by immunohistochemistry * At least 1 target lesion that is unirradiated and measurable by RECIST, Version 1.1 * Eastern Cooperative Oncology Group (ECOG) performance status of 0 - 2 * Adequate organ function Exclusion Criteria: * Prior chemotherapy for extensive-stage SCLC * Presence of symptomatic brain metastases requiring immediate treatment with radiation therapy or steroids. * Uncontrolled ischemic heart disease or uncontrolled symptomatic congestive heart failure * Known history of stroke or cerebrovascular accident within 6 months prior to enrollment * Other uncontrolled serious chronic disease or conditions that in the investigator's opinion could affect compliance or follow-up in the protocol * Concurrent radiotherapy to any site or radiotherapy within 2 weeks prior to enrollment or previous radiotherapy to the target lesion sites (the sites that are to be followed for determination of a response) * Receipt of any investigational medication within 4 weeks prior to enrollment