Study of AT-101 in Combination With Topotecan in Relapsed/Refractory Small Cell Lung Cancer

Inclusion Criteria: * Histologically or cytologically confirmed small cell lung cancer (SCLC). Mixed histology will not be eligible. * Progression of disease after only one prior platinum containing chemotherapy regimen. Prior Regimen must not have contained irinotecan * All patients must have measurable disease. * Patients may have received prior radiation therapy but they must have recovered from all treatment-related toxicities. * ECOG performance status 0-1 * Adequate hematologic function * Adequate liver and renal function * Ability to swallow oral medication Exclusion Criteria: * Patients with more than one prior regimen of chemotherapy or prior regimen that did not contain a platinum agent. Note: Patient who stopped prior therapy due to toxicity or had less than 2 cycles of platinum based therapy would not be eligible for the phase II portion of this study. * Prior chemotherapy regimen containing irinotecan. * Active secondary malignancy. * Unstable or progressive brain metastases. * Prior history of radiation therapy to \> 25% of the bone marrow. * Uncontrolled concurrent illness including, but not limited to: serious uncontrolled infection, symptomatic congestive heart failure (CHF), unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with the study requirements. * Failure to recover from toxicities related to prior therapy (e.g., surgery, radiation, chemotherapy).