2,4-Diaminoquinazolines as Dual Toll-like Receptor (TLR) 7/8 Modulators for the Treatment of Hepatitis B Virus

A novel series of 2,4-diaminoquinazolines was identified as potent dual Toll-like receptor (TLR) 7 and 8 agonists with reduced off-target activity. The stereochemistry of the amino alcohol was found to influence the TLR7/8 selectivity with the (R) isomer resulting in selective TLR8 agonism. Lead optimization toward a dual agonist afforded (S)-3-((2-amino-8-fluoroquinazolin4-yl)amino)hexanol 31 as a potent analog, being structurally different from previously described dual agonists (McGowan et al. J. Med. Chem. 2016, 59, 7936). Pharmacokinetic and pharmacodynamic (PK/PD) studies revealed the desired high first pass profile aimed at limiting systemic cytokine activation. In vivo pharmacodynamic studies with lead compound 31 demonstrated production of cytokines consistent with TLR7/8 activation in mice and cynomolgus monkeys and ex vivo inhibition of hepatitis B virus (HBV).