Phase 2 Etirinotecan Pegol in Refractory Brain Metastases & Advanced Lung Cancer / Metastatic Breast Cancer

Inclusion Criteria: * At least 18 years of age. * Life expectancy of 3 months or longer. * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2. Advanced or refractory cancer, consisting of * Metastatic breast cancer (mBC) for which single-agent cytotoxic chemotherapy is indicated. OR * Histologically-proven metastatic lung cancer: * Non-small cell lung cancer (NSCLC) as Stage IV disease or recurrent metastatic disease \[per lung cancer tumor, node and metastasis (TNM) classification system, 7th ed\] (Cohort A) OR * Small cell lung cancer (SCLC) as extensive stage or recurrent metastatic disease (cohort B), including tumors with mixed small cell and non-small cell elements. Prior chemotherapy (at least one of the following): * At least one line of prior systemic chemotherapy * At least one line of prior targeted treatment for metastatic disease Adjuvant systemic chemotherapy within prior 6 months Prior treatment for metastatic breast cancer (mBC) must have included taxane-based regimen Prior chemotherapy, including other investigational therapy, has been completed prior to initiation of study treatment, according to the following: * ≥ 2 weeks if immediately preceding treatment was chemotherapy/targeted therapy administered on a daily or weekly schedule * ≥ 3 weeks if immediately preceding treatment was chemotherapy/targeted therapy administered every 2 weeks * ≥ 4 weeks if immediately preceding treatment was chemotherapy/targeted therapy admi…