A compound of Formula 1 or pharmaceutically acceptable salt thereof: wherein, Y is O or S, when Y is O, R 1 is hydrogen; or a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino, R 2 is a C 1 ~C 6 alkyl group, R 3 is hydrogen, and R 4 is a (4-(dimethylamino)tetrahydro-2H-pyran-4-yl)methyl group; a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino; a C 1 ~C 4 alkyl group substituted with a nitrogen-containing cyclic ring wherein the nitrogen-containing cyclic ring is morpholine, piperidine, or pyrrolidine which is optionally substituted with C 1 ~C 4 alkyl; or a piperidinyl group optionally substituted with C 1 ~C 4 alkyl, or R 3 and R 4 are jointed each other, with the nitrogen atom to which they are attached, to form a piperazine ring wherein the piperazine ring is optionally substituted with C 1 ~C 4 alkyl, when Y is S, R 1 and R 2 are, independently of each other, hydrogen; a C 1 ~C 6 alkyl group; or a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino, R 3 is hydrogen, and R 4 is a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino, or R 3 and R 4 are jointed each other, with the nitrogen atom to which they are attached, to form a piperazine ring wherein the piperazine ring is optionally substituted with C 1 ~C 4 alkyl. when Y is O, R 1 is hydrogen; or a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino, R 2 is a C 1 ~C 6 alkyl group, R 3 is hydrogen, and R 4 is a (4-(dimethylamino)tetrahydro-2H-pyran-4-yl)methyl group; a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino; a C 1 ~C 4 alkyl group substituted with a nitrogen-containing cyclic ring wherein the nitrogen-containing cyclic ring is morpholine, piperidine, or pyrrolidine which is optionally substituted with C 1 ~C 4 alkyl; or a piperidinyl group optionally substituted with C 1 ~C 4 alkyl, or R 3 and R 4 are jointed each other, with the nitrogen atom to which they are attached, to form a piperazine ring wherein the piperazine ring is optionally substituted with C 1 ~C 4 alkyl, R 1 is hydrogen; or a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino, R 2 is a C 1 ~C 6 alkyl group, R 3 is hydrogen, and R 4 is a (4-(dimethylamino)tetrahydro-2H-pyran-4-yl)methyl group; a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino; a C 1 ~C 4 alkyl group substituted with a nitrogen-containing cyclic ring wherein the nitrogen-containing cyclic ring is morpholine, piperidine, or pyrrolidine which is optionally substituted with C 1 ~C 4 alkyl; or a piperidinyl group optionally substituted with C 1 ~C 4 alkyl, or R 3 and R 4 are jointed each other, with the nitrogen atom to which they are attached, to form a piperazine ring wherein the piperazine ring is optionally substituted with C 1 ~C 4 alkyl, when Y is S, R 1 and R 2 are, independently of each other, hydrogen; a C 1 ~C 6 alkyl group; or a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino, R 3 is hydrogen, and R 4 is a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino, or R 3 and R 4 are jointed each other, with the nitrogen atom to which they are attached, to form a piperazine ring wherein the piperazine ring is optionally substituted with C 1 ~C 4 alkyl. R 1 and R 2 are, independently of each other, hydrogen; a C 1 ~C 6 alkyl group; or a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino, R 3 is hydrogen, and R 4 is a C 1 ~C 4 alkyl group substituted with a mono- or di-C 1 ~C 5 alkylamino, or R 3 and R 4 are jointed each other, with the nitrogen atom to which they are attached, to form a piperazine ring wherein the piperazine ring is optionally substituted with C 1 ~C 4 alkyl. <EOS>