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.

Allocation and Arms Additional Information: All Patients will receive an 8-week

open-label lead-in treatment of ridaforolimus. After this 8 week period patients will be re-assessed for disease status. Patients who are stable after 8 weeks are randomized in a double-blind fashion to continue treatment with ridaforolimus or to a placebo until disease progression. (Those patients who have stable disease but are randomized to placebo may cross-over to open-label ridaforolimus at the time of disease progression.)

Those patients with tumor shrinkage during the open-label lead-in treatment will continue on open-label ridaforolimus, while those patients who have disease progression at 8-weeks are taken off-study.

Inclusion Criteria:

• Patient has histologically confirmed stage IIIB/IV non-small cell lung cancer
• Patient has a documented mutation of the KRAS gene
• Patient has evidence of disease progression following 1 but no more than 3 prior chemotherapy regimens
• A minimum of 4 weeks has passed since the most recent anti-cancer treatment
• Women of childbearing potential must have a negative pregnancy test prior to start of therapy and must use an approved contraceptive method for the duration of the study
• Patient has adequate organ function
• Patient has performance status of <=2 on Eastern Cooperative Oncology Group (ECOG) performance scale
• Patient is >=18 years of age

Exclusion Criteria:

• Patient has received more than 2 prior chemotherapy regimens for the treatment lung cancer
• Patient is known to have active brain metastases
• Patient is currently participating or has participated in an investigational drug study within 30 days
• Patient is known to be Human Immunodeficiency Virus (HIV) positive or has a known history of Hepatitis B or C
• Patient has an active infection requiring prescribed intervention
• Patient has newly diagnosed or un-controlled Type 1 or 2 diabetes