In an effort to overcome hERG affinity with a lead compound, several S-oxide and N-oxide analogues were synthesised with a much improved hERG profile but low in vivo absorption. This led to the implementation of an in situ oxidation strategy wherein a sulfide was dosed orally and systemic levels of the corresponding sulfoxide and sulfone were monitored. SAR and pharmacokinetic data to support this as a possible strategy are presented, although ultimately the approach was shown not to be suitable due to very low levels of active circulating metabolites.
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