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