CDK9 Inhibitors and Polymorphs Thereof For Use As Agents For Treatment of Cancer

A pharmaceutical composition comprising crystalline Form B of a compound having the following structure (I):

• or a zwitterionic form thereof, and a pharmaceutically acceptable carrier or excipient, wherein the pharmaceutically acceptable carrier or excipient is a filler, disintegrant, lubricant or fluidizer.

A method for treating a cancer in a mammal in need thereof, comprising administering to the mammal crystalline Form B of a compound having the following structure (I):

• or a zwitterionic form thereof, in an amount of from about 1 mg to about 30 mg per day.