The purpose of this study is to evaluate the objective tumor response rate to SNS-595 in patients with small cell lung cancer (SCLC).

Other objectives of this study are to assess the safety, survival rate, best response, time to disease progression, duration of tumor response, and to explore several potential biomarkers to see how these levels change after administration of SNS-595.

Inclusion Criteria:

• Able to understand and willing to sign a written informed consent document
• Patients who have recurrent or refractory SCLC requiring second-line chemotherapy who previously received first-line chemotherapy
• Measurable disease
• Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0, 1, or 2
• Brain metastasis may be included if the patient is neurologically stable and has been off steroids and anticonvulsants for at least 4 weeks prior to Cycle 1 Day 0
• Laboratory values within the normal or reasonable reference range as specified by the protocol

Exclusion Criteria:

• Prior exposure to SNS-595
• Pregnant or breastfeeding
• Women of childbearing potential, or male partners of women of childbearing potential, unwilling to use an approved, effective means of contraception according to the institution's standards
• Other active malignancies or other malignancies within the past 12 months, other than non-melanoma skin cancer, cervical intraepithelial neoplasia, or prostatic intraepithelial neoplasia
• Q-wave myocardial infarction or cerebrovascular accident/transient ischemic attack (TIA) within 6 months before the first SNS-595 dose
• Thromboembolic event (deep vein thrombosis or pulmonary embolus) within 28 days before the first SNS-595 dose
• Requires kidney dialysis (hemodialysis or peritoneal)
• Prior chemotherapy, investigational agents, or radiation therapy within 28 days before Cycle 1 Day 0; however, nitrosoureas, mitomycin C, and therapeutic monoclonal antibodies are not permitted for at least 42 days before Cycle 1 Day 0
• In patients with toxicities caused by prior cancer therapy, those toxicities must have returned to less than or equal to Grade 1, with the exception of alopecia.
• Prior pelvic radiation therapy or radiation to greater than 25% of bone marrow reserve; radiation to the brain is permitted up to 28 days before the first SNS-595 dose, as long as the patient does not require treatment with corticosteroids for symptom control related to brain metastases.
• Any other medical, psychological, or social condition that, in the opinion of the Principal Investigator, would contraindicate the patient's participation in the clinical trial due to safety or compliance with study procedures