Described herein is an adeno-associated virus (AAV) complex platform including an asymmetrically modified inverted terminal repeat (ITR). The AAV complex has advantages of increased productivity and expression efficiency of a transgene, and decreased genotoxicity, by having an asymmetric ITR in which any one of two ITRs is modified. Also, described herein is a composition comprising the adeno-associated virus complex and a method of gene therapy.