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A new series of lactam-derived EZH2 inhibitors was designed via ligand-based and physicochemical-property-based strategies to address metabolic stability and thermodynamic solubility issues associated with previous lead compound 1. The new inhibitors incorporated an sp 3 hybridized carbon atom at the 7-position of the lactam moiety present in lead compound 1 as a replacement for a dimethylisoxazole group. This transformation enabled optimization of the physicochemical properties and potency compared to compound 1. Analysis of relationships between calculated log D (clogD) values and in vitro metabolic stability and permeability parameters identified a clogD range that afforded an increased probability of achieving favorable ADME data in a single molecule. Compound 23a exhibited the best overlap of potency and pharmaceutical properties as well as robust tumor growth inhibition in vivo and was therefore advanced as a development candidate (PF-06821497). A crystal structure of 23a in complex with the three-protein PRC2 complex enabled understanding of the key structural features required for optimal binding.

The structure of the title compound, C(12)H(9)BrN(4), prepared by the reaction of 2-bromo-1-(6-bromo-3-pyrid-yl)ethanone with 2-amino-3-methyl-pyrazine indicates that the compound with the bromo-pyridyl substituent at position 2 of the imidazopyrazine fused-ring system represents the major product of this reaction. The plane of the pyridine ring forms a dihedral angle of 16.2 (2)° with the essentially planar (r.m.s. deviation = 0.006 Å) imidazopyrazine system. In the crystal, mol-ecules are linked by weak C-H⋯N inter-actions.