Discovery of Nanomolar Dengue and West Nile Virus Protease Inhibitors Containing a 4‑Benzyloxyphenylglycine Residue

The dengue virus (DENV) and West
Nile Virus (WNV) NS2B-NS3 proteases
are attractive targets for the development of dual-acting therapeutics
against these arboviral pathogens. We present the synthesis and extensive
biological evaluation of inhibitors that contain benzyl ethers of
4-hydroxyphenylglycine as non-natural peptidic building blocks synthesized
via a copper-complex intermediate. A three-step optimization strategy,
beginning with fragment growth of the C-terminal 4-hydroxyphenylglycine
to the benzyloxy ether, followed by C- and N-terminal optimization,
and finally fragment merging generated compounds with in vitro affinities
in the low nanomolar range. The most promising derivative reached Ki values of 12 nM at the DENV-2 and 39 nM at
the WNV proteases. Several of the newly discovered protease inhibitors
yielded a significant reduction of dengue and West Nile virus titers
in cell-based assays of virus replication, with an EC50 value of 3.4 μM at DENV-2 and 15.5 μM at WNV for the
most active analogue.