 This is a randomized discontinuation study of ridaforolimus in patients with advanced NSCLC who have failed at least 1 but no more than 3 prior treatment regimens and who have KRAS mutant lung cancer. Following 8 weeks of open-label ridaforolimus lead-in there will be an assessment of disease status. Patients assessed by the investigator to have stable disease after 8 weeks will be randomized to double-blind treatment with ridaforolimus or placebo. Patients assessed to have partial or complete response will continue on open-label ridaforolimus. Patients assessed to have disease progression will be discontinued from study. 