A Study of ASP8273 vs. Erlotinib or Gefitinib in First-line Treatment of Patients With Stage IIIB/IV Non-small Cell Lung Cancer Tumors With EGFR Activating Mutations

Inclusion Criteria: * Subject agrees not to participate in another interventional study while on treatment. * Female subject must either: * Be of nonchildbearing potential: postmenopausal (defined as at least 1 year without any menses) prior to Screening, or documented surgically sterile * Or, if of childbearing potential: Agree not to try to become pregnant during the study and for 28 days after the final study drug administration; And have a negative serum pregnancy test at Screening; And, if heterosexually active, agree to consistently use 2 forms of highly effective birth control (at least 1 of which must be a highly effective method and one must be a barrier method) starting at Screening and throughout the study period and for 28 days after the final study drug administration. * Female subject must not be breastfeeding at Screening or during the study period, and for 28 days after the final study drug administration. * Female subject must not donate ova starting at Screening and throughout the study period, and for 28 days after the final study drug administration. * Male subject and their female spouse/partners who are of childbearing potential must be using highly effective contraception consisting of 2 forms of birth control (1 of which must be a barrier method) starting at Screening and continue throughout the study period and for 90 days after the final study drug administration. * Male subject must not donate sperm starting at Screening and throughout the stu…