The purpose of this study is to determine the Objective Response Rate of KOS-1584, as a single agent in patients with stage IIIB/IV NSCLC whose disease has progressed following initial chemotherapy.

Inclusion Criteria:

• Histologically or cytologically proven NSCLC, Stage IIIB or Stage IV.
• Eligible patients must have received only one prior chemotherapy regime for Stage IIIB/IV NSCLC.
• Good performance status.

Exclusion Criteria:

• Prior treatment with an epothilone.
• Known central nervous system (CNS) metastases.
• Any chemotherapy, radiation therapy or immunotherapy or any investigational agent (therapeutic or diagnostic) within 3 weeks prior to first study drug administration.