However, resistant HSV occurs frequently in clinical therapy
when using nucleoside analogs, including ACV and penciclovir
(PCV) together with their respective prodrugs valacyclovir and
famciclovir.10 Duan et al. revealed that ACV-resistant HSV-1
isolates in immunocompetent patients with herpes keratitis had a
relatively high prevalence (6.4%, 11 out of 173 patients), and 9
out of the 11 patients with resistant isolates were refractory to
ACV therapy.11 Another report showed that the occurrence
frequencies of resistant HSV-1 isolates reached up to 14–30% in
allogeneic bone marrow transplant patients.12 Thus, the development of anti-HSV drugs with different mechanisms of action is
a matter of great urgency. At present, most investigational drugs
target viral and cellular enzymes.