Back-Pocket Optimization of 2‑Aminopyrimidine-Based Macrocycles Leads to Potent EPHA2/GAK Kinase Inhibitors

Macrocyclization of acyclic compounds is a powerful strategy for
improving inhibitor potency and selectivity. Here we have optimized
2-aminopyrimidine-based macrocycles to use these compounds as chemical
tools for the ephrin kinase family. Starting with a promiscuous macrocyclic
inhibitor, 6, we performed a structure-guided activity
relationship and selectivity study using a panel of over 100 kinases.
The crystal structure of EPHA2 in complex with the developed macrocycle 23 provided a basis for further optimization by specifically
targeting the back pocket, resulting in compound 55,
a potent inhibitor of EPHA2/A4 and GAK. Subsequent front-pocket derivatization
resulted in an interesting in cellulo selectivity
profile, favoring EPHA4 over the other ephrin receptor kinase family
members. The dual EPHA2/A4 and GAK inhibitor 55 prevented
dengue virus infection of Huh7 liver cells. However, further investigations
are needed to determine whether this was a compound-specific effect
or target-related.