Substituted Bis-THF Protease Inhibitors with Improved Potency against Highly Resistant Mature HIV‑1 Protease PR20

An extremely drug resistant mutant
of HIV-1 protease (PR) bearing
20 mutations (PR20) has been studied with two potent antiviral investigational
inhibitors. GRL-5010A and GRL-4410A were designed to introduce hydrogen
bond interactions with the flexible flaps of the PR by incorporating gem-difluorines and alkoxy, respectively, at the C4 position
of the bis-THF of darunavir. PR20 provides an excellent model for
high level resistance, since clinical inhibitors are >1000-fold
less
active on PR20 than on wild-type enzyme. GRL-5010A and GRL-4410A show
inhibition constants of 4.3 ± 7.0 and 1.7 ± 1.8 nM, respectively,
for PR20, compared to the binding affinity of 41 ± 1 nM measured
for darunavir. Crystal structures of PR20 in complexes with the two
inhibitors confirmed the new hydrogen bond interactions with Gly 48
in the flap of the enzyme. The two new compounds are more effective
than darunavir in inhibiting mature PR20 and show promise for further
development of antiviral agents targeting highly resistant PR mutants.