Figure 4.

(A,C,D) 2D interaction diagram of the three approved CDK4/6 selective inhibitors as observed in their X-ray complexes into CDK6: (A) palbociclib (PDB ID: 5L2I); (C) ribociclib (PDB ID: 5L2T); (D) abemaciclib (PDB ID: 5L2S). (B) 3D representation of the X-ray binding geometry of palbociclib (stick, yellow C atoms) into the CDK6 binding site (dark green solid surface). Protein residues involved in key H-bond interactions are represented as stick; H-bonds are depicted as magenta dashed lines.