Carboplatin, Etoposide, and Atezolizumab With or Without Trilaciclib (G1T28), a CDK 4/6 Inhibitor, 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 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

- Prior immunotherapies including but not limited to CD137, anti-PD-1, anti-PD-L1, and
CTLA4.

- Presence of symptomatic brain metastases requiring immediate treatment with radiation
therapy or steroids.

- History of pulmonary fibrosis, organizing pneumonia or pneumonitis on screening chest
CT

- Active, known, suspected autoimmune disease requiring systemic treatment in the past 2
years

- 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

- Receipt of any investigational medication within 4 weeks prior to enrollment

- Administration of attenuated vaccine within 4 weeks before enrollment

- Systemic treatment with corticosteriods or other immunosuppressive medications within
14 days of study drug administration