Aminopyridine compound

A compound represented by formula (I) or a pharmaceutically acceptable salt thereof,

• wherein,
• L is selected from —O— and —(CR4R5)n—;
• R1 is selected from —C1-6 alkyl- and —C3-5 cycloalkyl-, and the —C1-6 alkyl- and —C3-5 cycloalkyl- are optionally substituted by 1, 2 or 3 Ra;
• ring A is selected from phenyl, pyridyl and 5-membered heteroaryl, and the phenyl, pyridyl and 5-membered heteroaryl are optionally substituted by 1, 2 or 3 R3;
• and when ring A is selected from phenyl and pyridyl, R2 is selected from —C5-6 alkyl- and —C3-5 cycloalkyl-, and the —C5-6 alkyl- and —C3-5 cycloalkyl- are optionally substituted by 1, 2 or 3 Rb;
• when ring A is selected from 5-membered heteroaryl, R2 is selected from —C1-6 alkyl- and —C3-5 cycloalkyl-, and the —C1-6 alkyl- and —C3-5 cycloalkyl- are optionally substituted by 1, 2 or 3 Rc;
• R3 is selected from H, F, Cl, Br, I and CH3;
• R4 and R5 are each independently selected from H and CH3;
• n is selected from 0, 1 and 2;
• Ra, Rb and Rc are each independently selected from F, Cl, Br and I;
• the “5-membered heteroaryl” comprises 1, 2, 3 or 4 heteroatoms or heteroatom groups independently selected from —O—, —NH—, —S— and N, respectively.