A Phase III, Open-Label Study of Maintenance Lurbinectedin in Combination With Atezolizumab Compared With Atezolizumab in Participants With Extensive-Stage Small-Cell Lung Cancer

Inclusion Criteria for the Induction Phase:

* ECOG PS of 0 or 1
* No prior systemic therapy for ES-SCLC
* Treatment-free for at least 6 months since last chemo/radiotherapy, among those treated (with curative intent) with prior chemo/radiotherapy for limited-stage SCLC
* Histologically or cytologically confirmed ES-SCLC
* Adequate hematologic and end-organ function to receive 4 cycles of induction treatment with carboplatin, etoposide and atezolizumab
* Measurable disease, as defined by RECIST v1.1
* Negative HIV test and no evidence of active Hepatitis B or Hepatitis C at screening

Exclusion Criteria for the Induction Phase:

* Presence or history of CNS metastases
* Active or history of autoimmune disease or deficiency
* History of malignancies other than SCLC within 5 years prior to enrollment
* Prior treatment with CD137 agonists or immune checkpoint blockade therapies, including anti-CTLA-4, anti-PD-1, and anti-PD-L1 therapeutic antibodies, or lurbinectedin or trabectedin
* History of idiopathic pulmonary fibrosis, organizing pneumonia, drug induced pneumonitis, or idiopathic pneumonitis, or evidence of active pneumonitis on screening chest computed tomography (CT) scan
* Treatment with investigational therapy within 28 days prior to enrollment

Inclusion Criteria for the Maintenance Phase:

* ECOG PS of 0 or 1
* Ongoing response or stable disease per RECIST 1.1 after 4 cycles of induction therapy
* Toxicities attributed to prior induction anti-cancer therapy or PCI resolved to Grade \<=1
* Adequate hematologic and end-organ function

Exclusion Criteria for the Maintenance Phase:

* Presence or history of CNS metastases
* Receiving consolidative chest radiation
* Severe infection within 2 weeks prior to randomization into the maintenance
* Treatment with therapeutic oral or IV antibiotics at the time of randomization