This non-randomized, open-label clinical trial is designed to determine safety and clinical activity of a new chemotherapeutic agent, MAC-321, when given intravenously to patients with non-small cell lung cancer. Clinical activity will be evaluated by determining the percentage of patients with an objective tumor response after treatment with MAC-321. Patients must have been previously treated with a platinum-containing chemotherapy regimen.

A total of 96 patients will be enrolled in this trial. Eligible patients will receive MAC-321 intravenously every 3 weeks for up to a total of 6 courses of treatment. All patients will receive MAC-321 at the same dose. MAC-321 is an experimental drug, and is not offered outside of this research trial.

Inclusion Criteria:

• Recurrence of non-small cell lung cancer after at least 1 prior chemotherapy regimen containing a platinum agent
• Recovery from all acute side effects of prior therapies (with the exception of hair loss)
• Adequate bone marrow, liver, and kidney function

Exclusion Criteria:

• More than 2 prior chemotherapy regimens for treatment of advanced or metastatic non-small cell lung cancer. (Treatment given in conjunction with surgery will not be included in the maximum of 2 prior regimens)
• Radiation therapy, chemotherapy or any other anticancer therapy within 28 days of beginning study
• Symptomatic brain metastases