MEK inhibitors and therapeutic uses thereof

A compound of Formula (IIb):

• or a pharmaceutically acceptable salt thereof, wherein:
• Z is C or N;
• R2 is L;
• L is —Z1—Z2;
• Z1 is —CH2—;
• Z2 is optionally substituted
• and n is 1, 2, 3 or 4;
• and
• R6 is H, deuterium, halogen, or C1 to C6 alkyl.

A compound of Formula (IIb):

• or a pharmaceutically acceptable salt thereof, wherein
• Z is C or N;
• R2 is L;
• L is —Z1—Z2;
• Z1 is —CH2—;
• Z2 is optionally substituted
• and
• R6 is H, deuterium, halogen, or C1 to C6 alkyl.

A compound having the structure depicted in Formula (IIa):

• or a pharmaceutically acceptable salt thereof, wherein:
• R2 is L;
• R3 is the fluoro;
• R6 is H, deuterium, halogen, or C1 to C6 alkyl;
• R8 is C1 to C6 alkyl;
• L is —Z1—Z2;
• Z1 is —CH2;
• Z2 is selected from the group consisting of —NR5R5′, or C3 to C8 heterocyclyl;
• each R5 and R5 are each independently H, deuterium, or C1 to C6 alkyl;
• X is O;
• Y is O;
• and
• Z is C or N.