Haa-Na Song 1 , Ki Sun Jung 2 , Kwai Han Yoo 2 , Jinhyun Cho 2 , Ji Yun Lee 2 , Sung Hee Lim 2 , Hae Su Kim 2 , Jong-Mu Sun 2 , Se-Hoon Lee 2 , Jin Seok Ahn 2 , Keunchil Park 2 , Yoon-La Choi 3 , Woongyang Park 4 , Myung-Ju Ahn 5
T790M mutation is most common resistant mechanism to epidermal growth factor receptor gene (EGFR) tyrosin kinase inhibitor (TKI). Several third-generation EGFR-mutant selective TKI, such as AZD9291 (AstraZeneca), Rociletinib (Clovis), or HM61713 (Hanmi) have been developed. Acquired resistant C797S mutation was known to be one of the resistance mechanisms of AZD9291, which has not been reported for HM61713 yet. This is the first case report of C797S mutation as resistance mechanism of HM61713.