In Vitro Activity and Mechanism of Action of Methylenecyclopropane Analogs of Nucleosides against Herpesvirus Replication

Abstract

We have reported previously that methylenecyclopropane analogs of nucleosides have excellent activity against certain members of the herpesvirus family. A second generation, the 2,2-bis-hydroxymethyl derivatives, were synthesized, and 18 compounds were tested for activity in vitro against herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), human and murine cytomegalovirus (HCMV and MCMV), varicella-zoster virus (VZV), and Epstein-Barr virus (EBV). Selected analogs were also evaluated against human herpesvirus type 6 (HHV-6) and HHV-8. None of the 18 compounds had activity against HSV-1 or HSV-2, but four were active against VZV by plaque reduction (PR) assay at 50% effective concentration (EC 50 ) levels of <50 M. Six of the 18 compounds were active against HCMV by cytopathic effect or PR assays with EC 50 s of 0.5 to 44 M, and all were active against MCMV by PR (0.3 to 54 M). Four of the compounds were active against EBV by enzyme-linked immunosorbent assay (<0.3 to 4.4 M). Four compounds with CMV activity were also active against HHV-6A and HHV-6B (0.7 to 28 M), and three compounds were active against HHV-8 (5.5 to 16 M). One of these, ZSM-I-62, had particularly good activity against CMV, HHV-6, and HHV-8, with EC 50 s of 0.7 to 8 M. Toxicity was evaluated in adherent and nonadherent cells, and minimal cytotoxicity was observed. Mechanism of action studies with HCMV suggested that these compounds are phosphorylated by the ppUL97 phosphotransferase and are potent inhibitors of viral DNA synthesis. These results indicate that at least one of these compounds may have potential for use in treating CMV and other herpesvirus infections in humans.Human cytomegalovirus (HCMV) infects approximately 40 to 80% of the population, and serious life-threatening manifestations are associated with congenital infection and immunosuppression (5). Currently, therapeutic agents such as ganciclovir (GCV), foscarnet (PFA), and cidofovir (CDV) are used to treat HCMV infections, and while GCV is highly effective in treating CMV retinitis, pneumonia, and gastrointestinal disease, long-term therapy is generally required because infection often recurs upon cessation of therapy. The development of drug resistance and severe side effects due to drug toxicity may also occur during long courses of treatment and may limit the clinical use of these drugs. The increased use of immunosuppression for cancer chemotherapy and organ transplantation presents an ever-increasing need for more effective and less toxic antiviral drugs.A relatively new series of nucleoside analogs, the methylenecyclopropanes were modeled after allene analogs, which have been shown to exhibit antiviral activity (23). The first generation can be regarded as bioisosteric analogs of acyclovir where the C-O-C moiety was replaced by the methylenecyclopropane moiety. In a similar fashion, the second generation of methylenecyclopropane analogs are related to ganciclovir (25). In both cases, the Z-and E-isomeric series of analogs were generated. We have reported previously that ...

Human herpesvirus 6 infections after liver transplantation

“…Recently, the clinical development of maribavir for the prevention of primary CMV disease after liver transplantation has been terminated since it was not demonstrated to be superior to placebo in stem cell transplant recipients. On the other hand, cyclopropavir, a recently developed guanine nucleoside analogue, has been shown to have activity against HHV-6 in vitro [89] . Hexadecyloxopropyl-cidofovir, a prodrug of cidofovir, has also been shown to be three times more potent than cidofovir against DNA viruses, including HHV6-A [90] .…”

“…Acyclovir [73,81] No No Ganciclovir [66][67][68][70][71][72] Yes Yes Mutation in U38 DNA polymerase Mutation in U69 phosphotransferase Foscarnet [65,[82][83][84][85] Yes Yes 2 Mutation in U38 DNA polymerase Cidofovir [76,86,95] Yes Yes Mutation in U38 DNA polymerase Maribavir [87,88] No Not available Cyclopropavir [89] Yes…”

Human herpesvirus type 6 reactivation after haematopoietic stem cell transplantation

“…Cyclopropavir is still in the preclinical stage. 58 For the present, all available evidence regarding antiviral therapy is based on therapies started at the onset of HHV6 disease. For instance, Ogata et al prospectively studied pre-emptive ganciclovir therapy in 6 of 29 HSCT patients.…”

“…61 Only cyclopropavir was tested in HHV-6 Z-29 infected cord blood lymphocytes. 58 compound available for the treatment of HHV6 reactivation. However, the clinical use of cidofovir for HSCT patients is restricted due to the risk of developing nephrotoxicity.…”

A Herpes Simplex Virus Scaffold Peptide That Binds the Portal Vertex Inhibits Early Steps in Viral Replication

“…Different compounds target the viral helicase/primase (6), a conserved viral protein kinase (7)(8)(9)(10)(11), and the viral terminase, which is a 3-component enzyme that endonucleolytically cleaves viral DNA from concatemers within the infected cell nucleus and pumps the cleaved genomes into a preformed capsid through a portal vertex (10,(12)(13)(14)(15)(16). Others, such as cidofovir, likely affect the viral DNA polymerase (17,18).…”