Randomized Study of Maintenance Therapy With MGN1703 in Patients With SCLC

1. Male and female patients with extensive disease SCLC ≥ 18 years of age receiving first line treatment; 2. Histology of SCLC or mixed histology of SCLC if SCLC histology is at least 80%; 3. Completion of 4 cycles of first-line therapy with a platinum-based regimen and no other prior chemotherapy; 4. Documented evidence of tumor response as assessed by investigators after the first 2 cycles of platinum-based chemotherapy followed by a confirmed PR or CR at the end of fourth cycle by CT or MRI scan; 5. Brain metastases are allowed only after cranial irradiation, if not requiring continuous treatment with steroids or anticonvulsants; 6. ECOG performance status 0 or 1; 7. Adequate organ function with total bilirubin, lactate dehydrogenase \[LDH\], alkaline phosphatase \[AP\], gamma glutamyltransferase \[GGT\], albumin, creatinine, urea, electrolytes, and coagulation parameters ≤ 1.5 × upper limit of normal (ULN), and with aspartate aminotransferase \[AST\] and ALT ≤ 2.5 × ULN in the absence of liver metastases or ≤ 5.0 × ULN in the presence of liver metastases; 8. Adequate hematological parameters: absolute neutrophil count ≥ 1.5 × 109/L; platelet count ≥ 100 × 109/L; leukocyte count ≥ 3.0 × 109/L; lymphocytes ≥ 1.0 × 109/L; hemoglobin ≥ 9.0 g/dL or 5.59 mmol/L; 9. Patients with reproductive potential agree to use effective contraceptive measures throughout the study; 10. Negative pregnancy test in women of childbearing potential; 11. Signed informed consent form (ICF).