Quaratusugene Ozeplasmid (Reqorsa) and Atezolizumab Maintenance Therapy in ES-SCLC Patients

This clinical trial will evaluate the combination of quaratusugene ozeplasmid with atezolizumab as maintenance therapy for patients with Extensive Stage Small Cell Lung Cancer (ES-SCLC). The study is comprised of 2 phases, a dose selection phase (Phase 1) and a safety and efficacy evaluation phase (Phase 2).

Inclusion Criteria: * Male or female aged ≥18 years. * Documented history of histologically or cytologically confirmed ES-SCLC, prior to starting treatment with the combination of atezolizumab, carboplatin, and etoposide * Complete Response (CR), Partial Response (PR), or Stable Disease (SD) after receiving at least three cycles, and no more than four cycles, of atezolizumab, carboplatin, and etoposide. * Eastern Cooperative Oncology Group performance status (ECOG PS) score from 0 to 1. * Must be ≥28 days beyond major surgical procedures such as thoracotomy, laparotomy, or joint replacement, and must not have evidence of wound dehiscence, active wound infection, or comparable major residual complications of the surgery per Investigator assessment. * Asymptomatic brain metastases must meet ALL criteria of the following (a-d): 1. No history of seizures in the preceding six months. 2. Definitive treatment must be completed ≥21 days prior to enrollment. 3. Must be off steroids administered because of brain metastases or related symptoms for ≥7 days. 4. If had previous brain irradiation, post-treatment imaging must demonstrate stability or regression of the brain metastases. * Absolute neutrophil count (ANC) \>1500/mm3, platelet count \>100,000/mm3 within ≤28 days. * Adequate renal function documented by serum creatinine of ≤1.5 mg/dL or calculated creatinine clearance \>50 ml/min within ≤28 days. * Adequate hepatic function as documented by serum bilirubin \