Synthesis and structure-activity relationships of the (alkylamino)piperidine-containing BHAP class of non-nucleoside reverse transcriptase inhibitors: effect of 3-alkylpyridine ring substitution

Development of resistance to currently approved HIV therapies has continued to fuel research efforts to improve the metabolic stability and spectrum of activity of the (alkylamino)piperidine-containing bis(heteroaryl)piperazine (AAP-BHAP) class of non-nucleoside Reverse Transcriptase inhibitors (NNRTIs). The synthesis of analogues in which the usual 3-alkylamino substituent on the pyridine ring is replaced by a 3-alkyl substituent led to compounds which retained activity against recombinant P236L and wild-type (WT) Reverse Transcriptase (RT), while inhibition of the Y181C mutant RT was reduced relative to the activity of the 3-alkylamino-substituted congeners. Testing of representative analogues in an in vitro liver microsome assay indicated that the alkyl substituent would not appreciably improve the metabolic stability of the AAP-BHAP template. In vivo pharmacokinetic evaluation of three compounds confirmed these results in that high systemic clearances were observed. Nevertheless, one compound (13), PNU-103657, possessed oral bioavailability in rats approaching that of the structurally related NNRTI drug delavirdine which is currently on the market for the treatment of HIV Infection.