M7824 and Topotecan or Temozolomide in Relapsed Small Cell Lung Cancers

* INCLUSION CRITERIA: * Patients must have histologically or cytologically confirmed small cell lung cancer (SCLC) or extrapulmonary small cell cancers. * Subjects with relapsed SCLC (diagnosed with limited or extensive stage disease) with tumor progression on or after at least one prior chemotherapy. Patients with SCLC should in addition have received and have disease progression on or after prior immunotherapy. * Male and female subjects greater than or equal to 18 years of age. Because no dosing adverse event data are currently available on the use of topotecan, temozolomide and M7824 in subjects 18 years of age, children are excluded from this study. * Eastern Cooperative Oncology Group (ECOG) performance status greater than or equal to 2. * Subjects must have measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 * Subjects must not have received chemotherapy or undergone major surgery within 2 weeks and radiotherapy within 24 hours prior to enrollment. * Patients must have adequate organ and marrow function as defined below: * hemoglobin greater than or equal to 9.0 g/dL * absolute neutrophil count greater than or equal to 1.5x109/L * platelets greater than or equal to 100x10\^9/L * total bilirubin less than or equal to 2.0 mg/dL * Aspartate aminotransferase (AST) serum glutamic oxaloacetic transaminase (SGOT)/alanine aminotransferase (ALT) serum glutamic-pyruvic transaminase (SGPT) less than or equal to 2.5 x upper limit of normal (ULN) or if liver metastases were present, less than or equal to 5 x ULN * creatinine less than or equal to 1.5 mg/dL OR --creatinine clearance greater than or equal to 40 mL/min * Ability of subject to understand and the willingness to sign a written informed consent document. * The effects of the trial treatment on the developing human fetus are unknown; thus, women of childbearing potential and men must agree to use highly-effective contraception prior to study entry, for the duration of study participation and up to 6 months for women and 3 months for men after the last dose of study drug. Men should not donate sperm during participation in the study and for up to 3 months after the last dose of study drug. Should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately. EXCLUSION CRITERIA: * Subjects with tumor amenable to potentially curative therapy per principal investigator (PI). * Subjects who are receiving any other investigational agents. Prior immunotherapy, topotecan and temozolomide are allowed. * History of allergic reactions attributed to compounds of similar chemical or biologic composition to (study agent) or other agents used in study. * Subjects with symptomatic brain metastases will be excluded from trial secondary to poor prognosis. However, subjects who have asymptomatic brain metastases, and those had treatment for their brain metastasis and whose brain disease is stable without steroid therapy for 2 weeks may be enrolled (replacement doses less than or equal to 10 mg of prednisone or equivalent per day are allowed). * Subjects with evidence of severe or uncontrolled systemic disease, or any concurrent condition, which could compromise participation in the study, including, but not limited to, active or uncontrolled infection, immune deficiencies (human immunodeficiency virus (HIV)-positive subjects on combination antiretroviral therapy are eligible), Hepatitis B, Hepatitis C, uncontrolled diabetes, uncontrolled hypertension, symptomatic congestive heart failure, unstable angina pectoris, myocardial infarction within the past 3 months, uncontrolled cardiac arrhythmia, stroke/cerebrovascular accident within the past 3 months, bleeding diathesis or recent (within 3 months) clinically significant bleeding events or psychiatric illness/social situations which would jeopardize compliance with the protocol. * Pregnant women are excluded from this study because topotecan and temozolomide are Class D agents with the potential for teratogenic or abortifacient effects and because the effects of M7824 on the developing human fetus are currently unknown. In addition, because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with topotecan, temozolomide or M7824, breastfeeding should be discontinued if the mother is treated with these agents * Active autoimmune disease that might deteriorate when receiving an immunostimulatory agent with the exceptions: * Diabetes type I, vitiligo, alopecia, psoriasis, hypo- or hyperthyroid disease not requiring immunosuppressive treatment are eligible; * Subjects requiring hormone replacement with corticosteroids are eligible if the steroids are administered only for the purpose of hormonal replacement and at doses less than or equal to 10 mg of prednisone or equivalent per day; * Administration of steroids for other conditions through a route known to result in a minimal systemic exposure (topical, intranasal, intro-ocular, or inhalation) is acceptable. * Systemic therapy with immunosuppressive agents within 7 days before enrollment. * Administration of live vaccines within 30 days prior to the first administration of study intervention. Seasonal flu vaccines that do not contain a live virus are permitted. Locally approved Coronavirus Disease (COVID) vaccines are permitted. * Subjects unwilling to accept blood products as medically indicated. * Known contraindication for topotecan or temozolomide