Three acyclic
nucleoside phosphonates (ANPs) have been formally approved for clinical use in the treatment of 1)
cytomegalovirus retinitis in
AIDS patients (
cidofovir, by the intravenous route), 2)
chronic hepatitis B virus (HBV)
infections (
adefovir dipivoxil, by the oral route), and 3) human immunodeficiency virus (
HIV) infections (
tenofovir disoproxil fumarate, by the oral route). The activity spectrum of
cidofovir {(S)- 1-[3-hydroxy-2-(phosphonomethoxy)propyl]
cytosine [(S)-
HPMPC)]}, like that of (
S)-HPMPA [(S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]
adenine) and (S)-
HPMPDAP [(S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]-2, 6-diaminopurine), encompasses a broad spectrum of DNA viruses, including polyoma-,
papilloma-, adeno-, herpes-, and poxviruses.
Adefovir {9-[2-(phosphonomethoxy)ethyl]
adenine (PMEA)} and
tenofovir [(R)-9-[2-(phosphonomethoxy) propyl]
adenine [(R)-PMPA)]} are particularly active against retroviruses (ie., HIV) and hepadnaviruses (ie., HBV); additionally, PMEA also shows activity against herpes- and poxviruses. We have recently identified a new class of ANPs, namely 6-[2-(phosphonomethoxy)
alkoxy]-2,4-diaminopyrimidines, named, in analogy with their alkylpurine counterparts, HPMPO-DAPy, PMEO-DAPy, and (R)-PMPO-DAPy. These compounds exhibit an
antiviral activity spectrum and potency that is similar to that of (S)-
HPMPDAP, PMEA, and (R)-PMPA, respectively. Thus, PMEO-DAPy and (R)-PMPO-DAPy, akin to PMEA and (R)-PMPA, proved particularly active against HIV- 1, HIV-2, and the murine retrovirus Moloney sarcoma virus (MSV). PMEO-DAPy and (R)-PMPO-DAPy also showed potent activity against both wild-type and
lamivudine-resistant strains of HBV. HPMPO-DAPy was found to inhibit different poxviruses (ie.,
vaccinia,
cowpox, and orf) at a similar potency as
cidofovir. HPMPO-DAPy also proved active against adenoviruses. In vivo, HPMPO-DAPy proved equipotent to
cidofovir in suppressing vaccinia virus
infection (tail lesion formation) in immunocompetent mice and promoting healing of disseminated
vaccinia lesions in athymic-nude mice. The 6-[2-(phosphonomethoxy)
alkoxy]-2,4-diaminopyrimidines offer substantial potential for the treatment of a broad range of retro-, hepadna-, herpes-, adeno-, and
poxvirus infections.