A Study to Evaluate Safety and Efficacy of HS-10296 as First-Line Treatment in Patients

Drug: HS-10296 110 mg/55 mg + placebo The initial dose of HS-10296 110 mg once daily can be reduced to 55 mg once daily under specific circumstances. A cycle of treatment is defined as 21 days of once daily treatment. Number of Cycles: as long as patients are continuing to show clinical benefit, as judged by the Investigator, and in the absence of discontinuation criteria.

Drug: Gefitinib 250 mg + placebo The initial dose of Gefitinib 250 mg once daily cannot be reduced. A cycle of treatment is defined as 21 days of once daily treatment. Number of cycles: as long as patients are continuing to show clinical benefit, as judged by the Investigator, and in the absence of discontinuation criteria.