Balancing hERG affinity and absorption in the discovery of AZD5672, an orally active CCR5 antagonist for the treatment of rheumatoid arthritis.

Modifications to a series of potent and selective substituted 1-(3,3-diphenylpropyl)-piperidine phenylacetamide CCR5 antagonists were explored with the aim of reducing affinity at the hERG cardiac ion channel. Replacement of one aromatic ring in the diphenylpropyl region with less lipophilic, saturated heterocyclic rings and subsequent optimisation of the other phenyl ring led to the identification of clinical compound AZD5672 which retained excellent potency while reducing hERG affinity. Modulating lipophilicity affected the interplay between potency, hERG affinity and absorption.