Heterocycle derivative

A compound represented by Formula 1, or a salt thereof:

• wherein:
• X1 is nitrogen (N) or carbon (C), and X2 is carbon (C);
• is a single bond or a double bond;
• L is —NH—;
• R1 is a hydrogen atom or C1-C6 alkyl;
• R2 is NH2;
• R3 is absent, a hydrogen atom or C1-C6 alkyl;
• R4 is halogen, or C1-C6 alkyl;
• and
• R5 is a monovalent radical selected from the group consisting of Formula 3 and Formula 4:
• wherein X3, X4, X5 and X6 are carbon (C),
• X3 is connected to a linker (L),
• R26 to R31 are each independently a hydrogen atom, or C1-C6 alkyl,
• between X5 and X6 is a single bond or a double bond;
• wherein X7 is carbon (C), R33 to R39 are a hydrogen atom or C1-C6 alkyl,
• R32 is connected to a linker (L),
• between R38 and R39 and between R37 and R36 are single bond or a double bond.