PHARMACEUTICAL COMPOUNDS

The invention provides a composition of matter which:(i) consists of at least 90% by weight of an atropisomer (2A) and 0-10% by weight of an atropisomer of formula (2B); or(ii) consists of at least 90% by weight of an atropisomer (2B) and 0-10% by weight of an atropisomer of formula (2A);wherein the atropisomer of formula (2A) and the atropisomer of formula (2B) are represented by:or are pharmaceutically acceptable salts or tautomers thereof, wherein ring X is a benzene or pyridine ring; ring Y is selected from a benzene ring, a pyridine ring and a thiophene ring; R1 is trifluoromethyl; R2 is hydrogen; R3 is hydrogen; m is 0 or 1; n is 0, 1 or 2; Ar1 is a monocyclic aromatic ring selected from benzene and pyridine; each monocyclic aromatic ring being unsubstituted or substituted with 1 or 2 substituents R5 as defined herein; and R4; R5 when present, R6 and R7 independently selected from various substituents as defined herein.Also provided are individual atropisomers, pharmaceutical compositions and the uses of the atropisomers and compositions are inhibitors of PLK1- and PLK4 kinases, for example in the treatment of cancers.