Compounds were evaluated for
antiviral activity in
rhabdomyosarcoma (RD) cells against a recent 2014 clinical isolate of enterovirus D68 (EV-D68), a 1962 strain of EV-68D, rhinovirus 87 (RV-87, serologically the same as EV-D68), and enterovirus 71 (EV-71). Test substances included known-active antipicornavirus agents (
enviroxime,
guanidine HCl,
pirodavir,
pleconaril, and
rupintrivir), nucleobase/
nucleoside analogs (3-deazaguanine and
ribavirin), and three novel epidithiodiketopiperazines (KCN-2,2'-epi-19, KCN-19, and KCN-21). Of these,
rupintrivir was the most potent, with 50% inhibition of viral cytopathic effect (EC50) and 90% inhibition (EC90) of virus yield at 0.0022-0.0053 μM against EV-D68.
Enviroxime,
pleconaril and the KCN compounds showed efficacy at 0.01-0.3 μM;
3-deazaguanine and
pirodavir inhibited EV-D68 at 7-13 μM, and
guanidine HCl and
ribavirin were inhibitory at 80-135 μM.
Pirodavir was active against EV-71 (EC50 of 0.78 μM) but not against RV-87 or EV-D68, and all other compounds were less effective against EV-71 than against RV-87 and EV-D68. The most promising compound inhibiting both
virus infections at low concentrations was
rupintrivir.
Antiviral activity was confirmed for the ten compounds in virus yield reduction (VYR) assays in RD cells, and for
enviroxime,
guanidine HCl, and
pirodavir by cytopathic effect (CPE) assays in A549, HeLa-Ohio-1, and RD cells. These studies may serve as a basis for further pre-clinical discovery of anti-enterovirus inhibitors. Furthermore, the
antiviral profiles and growth characteristics observed herein support the assertion that EV-D68 should be classified together with RV-87.