This study will clinically assess for the first time the combination of EC145+docetaxel (Arm B) in participants with NSCLC (Stage IIIB or IV). This is an international, multicenter, centrally randomized, open-label, phase 2 study comparing single-agent EC145, EC145+docetaxel combination therapy, and single-agent docetaxel in participants with NSCLC who have failed one prior chemotherapy and who have all target lesions expressing the folate receptor [FR(++)]. Eligible participants will be randomized in a 1:1:1 ratio into either Arm A (single-agent EC145), Arm B (EC145+docetaxel combination therapy), or Arm C (single-agent docetaxel) and will receive treatment until either disease progression or intolerable toxicity.