Phase 1b/2 Study of Carfilzomib, Carboplatin, and Etoposide in Patients With Previously Untreated Extensive Stage Small-cell Lung Cancer

Key Inclusion Criteria: 1. Histologically or cytologically confirmed diagnosis of extensive-stage small-cell lung cancer (ES-SCLC) with measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1; ES-SCLC is defined as: small-cell lung cancer (SCLC) that has spread beyond one hemithorax and regional lymph nodes on the same side (e.g., supraclavicular) to the contralateral hemithorax, lymph nodes, or more distant locations in the body 2. Subjects with asymptomatic brain metastases or other central nervous system (CNS) disease at screening/diagnosis are eligible 3. Males and females ≥ 18 years of age 4. Eastern Cooperative Oncology Group (ECOG) performance status 0-1 Key Exclusion Criteria: 1. Previous systemic therapy to treat small-cell lung cancer (SCLC). Subjects with recurrent or progressive limited-stage SCLC after previous systemic treatment are not eligible for study participation. 2. Whole brain or focal radiation therapy within 14 days prior to Cycle 1 Day 1 (C1D1) for Phase 1b or prior to randomization for Phase 2 3. Congestive heart failure (New York Heart Association \[NYHA\] class III to IV), symptomatic ischemia, conduction abnormalities uncontrolled by conventional intervention, or myocardial infarction within 6 months prior to prior to C1D1 for Phase 1b or prior to randomization for Phase 2