Acyclic Phosphonomethylether Nucleoside Inhibitors of Respiratory Viruses

A series of acyclic phosphonomethylether nucleosides were synthesized and then evaluated for inhibitory activity against respiratory viruses of clinical significance using CPE inhibition, neutral red uptake and virus yield reduction assays. Of the 20 compounds synthesized, none significantly inhibited influenza A or B viruses or respiratory syncytial virus strains A2, Long or 18537; the selective indices (SI) were less than 10. A new compound, GS-2128 (2R, 5R-9-[2,5-dihydro-5-(phosphonomethoxy)-2-furanyl]adenine; D4API), selectively inhibited adenovirus 5 (SI>10) as did GS-0577 (9-(3-hydroxy-2-phosphonylmethoxypropyl)-adenine; HPMPA) and GS-0504 [(S)-1-[3-hydroxy-2-(phosphonylmethoxypropyl)]-cytosine; HPMPC]. The 50% effective concentrations (EC50) ranged from 8–100 μg mL−1 and 50% cell inhibitory concentrations (CC50) from 40–1000 μg mL−1. All three compounds were also found to be active against laboratory strains and clinical isolates of adenovirus types 1, 2, 8 and 41 with EC50 values ranging from 0.2 to 10 μg mL−1. Two compounds, GS-438 (9-(2-phosphonylmethoxyethyl)guanine, PMEG) and GS-2542 (9-[3-phosphonomethoxy)methoxymethyl]guanine) inhibited parainfluenza virus 3 strain C243, with SI of 52 and >333, respectively. PMEG also inhibited measles virus strains CC, Halonen and Chicago with EC50 values ranging from 0.03–9 μg mL−1. These data suggest that these compounds should be considered for possible development as therapeutic agents for respiratory virus infections.

Synthesis and Anti-HIV properties of new water-soluble bis-functionalized[60]fullerene derivatives

A new series of bis-functionalized fullerene C(60) derivatives bearing two or more solubilizing chains have been evaluated for their activity against HIV-1 and HIV-2 strains. Some of the compounds show activity against HIV-1 type in the low micromolar range. The effect of the positions of the addends on the C(60) nucleus has been investigated, indicating that only trans-2 isomers possess promising activity. The presence of a quaternary pyrrolidinium nitrogen is essential to increase solubility.

Synthesis and Cytostatic Activity of N-[2-(Phosphonomethoxy)alkyl] Derivatives of N6-Substituted Adenines, 2,6-Diaminopurines and Related Compounds

N6-Substituted adenine and 2,6-diaminopurine derivatives of 9-[2-(phosphonomethoxy)- ethyl] (PME), 9-[(R)-2-(phosphonomethoxy)propyl] [(R)-PMP] and enantiomeric (S)-PMP series were synthesized by reactions of primary or secondary amines with 6-chloro-9-{[2-(diisopropoxyphosphoryl)methoxy]alkyl}purines (26-28) or 2-amino-6-chloro-9-{[2-(diisopropoxy- phosphoryl)methoxy]alkyl}purines (29-31) followed by treatment of the diester intermediates32with bromo(trimethyl)silane and hydrolysis. Diesters32were also obtained by reaction ofN6-substituted purines with synthons23-25bearing diisopropoxyphosphoryl group. Alkylation of 2-amino-6-chloropurine (9) with diethyl [2-(2-chloroethoxy)ethyl]phosphonate (148) gave the diester149which was analogously converted toN6-substituted 2,6-diamino- 9-[2-(2-phosphonoethoxy)ethyl]purines151-153. Alkylation ofN6-substituted 2,6-diaminopurines with (R)-[(trityloxy)methyl]oxirane (155) followed by reaction of thus-obtained intermediates156with dimethylformamide dimethylacetal and condensation with diisopropyl [(tosyloxy)methyl]phosphonate (158) followed by deprotection of the intermediates159gaveN6-substituted 2,6-diamino-9-[(S)-3-hydroxy-2-(phosphonomethoxy)propyl]purines160-163. The highest cytostatic activityin vitrowas exhibited by the followingN6-derivatives of 2,6-diamino-9-[2-(phosphonomethoxy)ethyl]purine (PMEDAP): 2,2,2-trifluoroethyl (53), allyl (54), [(2-dimethylamino)ethyl] (68), cyclopropyl (75) and dimethyl (91). In CCRF-CEM cells, the cyclopropyl derivative75is deaminated to the guanine derivative PMEG (3) which is then converted to its diphosphate.

Structure-antiviral activity relationship in the series of pyrimidine and purine N-[2-(2-phosphonomethoxy)ethyl] nucleotide analogues. 1. Derivatives substituted at the carbon atoms of the base

A series of dialkyl esters of purine and pyrimidine N-[2-(phosphonomethoxy)ethyl] derivatives substituted at position 2, 6, or 8 of the purine base or position 2, 4, or 5 of the pyrimidine base were prepared by alkylation of the appropriate heterocyclic base with 2-chloroethoxymethylphosphonate diester in the presence of sodium hydride, cesium carbonate, or 1,8-diazabicyclo[5,4, 0]undec-7-ene (DBU) in dimethylformamide. Additional derivatives were obtained by the transformations of the bases in the suitably modified intermediates bearing reactive functions at the base moiety. The diesters were converted to the corresponding monoesters by sodium azide treatment, while the free acids were obtained from the diester by successive treatment with bromotrimethylsilane and hydrolysis. None of the PME derivatives in the pyrimidine series, their 6-aza or 3-deaza analogues, exhibited any activity against DNA viruses or retroviruses tested, except for the 5-bromocytosine derivative. Substitution of the adenine ring in PMEA at position 2 by Cl, F, or OH group decreased the activity against all DNA viruses tested. PMEDAP was highly active against HSV-1, HSV-2, and VZV in the concentration range (EC50) of 0.07-2 microg/mL. Also the 2-amino-6-chloropurine derivative was strongly active (EC50 = 0.1-0. 4 microg/mL) against herpes simplex viruses and (EC50 = 0.006-0.3 microg/mL) against CMV and VZV. PMEG was the most active compound of the whole series against DNA viruses (EC50 approximately 0.01-0.02 microg/mL), though it exhibited significant toxicity against the host cells. The base-modified compounds did not show any appreciable activity against DNA viruses except for 7-deazaPMEA (IC50 approximately 7.5 microg/mL) against HIV-1 and MSV. The neutral (diisopropyl, diisooctyl) diesters of PMEA were active against CMV and VZV, while the corresponding monoesters were inactive. The diisopropyl ester of the 2-chloroadenine analogue of PMEA showed substantially (10-100x) higher activity against CMV and VZV than the parent phosphonate. Also, the diisopropyl and diisooctyl ester of PMEDAP inhibited CMV and VZV, but esterification of the phosphonate residue did not improve the activity against either MSV or HIV.

Toxicity associated with high dosage 9-[(2R,5R-2,5-dihydro-5-phosphonomethoxy)-2-furanyl]adenine therapy off attempts to abort early FIV infection

9-[(2R,5R-2,5-dihydro-5-phosphonomethoxy)-2-furanyl]adenine, or D4API, was tested in the feline immunodeficiency virus (FIV) infection model and found to be significantly more inhibitory in vitro than its parent compound 9-phosphonylmethoxethyl adenine (PMEA). Cytotoxicity was less than for PMEA or azidothymidine (AZT) for culture periods of 7 days, but more toxic after 10 days. D4API was rapidly absorbed by cats following subcutaneous inoculation, with a plasma half-life of less than 1 h after intravenous inoculation and between 2 and 3 h after subcutaneous injection. Peripheral blood mononuclear cells collected from cats given a single dose of D4API were refractory, however, to FIV infection in vitro for up to 24 h. Given its prolonged intracellular phase and high selectivity index, high dose D4API therapy was tested for its ability to abort an acute (i.e. 2 week) FIV infection. A divided daily dose of D4API, which was one-fourth the toxic dose and 125 times the concentration that would totally inhibit virus replication in vitro, completely abrogated the anticipated viremia and antibody responses. Unfortunately, a majority of treated/uninfected and treated/infected test cats died acutely of drug toxicity after 47 days of treatment. Toxicity in vivo mirrored what was observed in vitro, being precipitous and cumulative in nature. Toxic signs included widespread hepatic and lymphoid necrosis. A surviving treated/FIV infected cat remained healthy to day 175 when the study was terminated; antibodies appeared 2 months later than in untreated/infected cats and virus was only detectable at low levels on day 175. In contrast, untreated/infected cats were viremic and antibody positive from 3 to 4 weeks post-infection onwards. Therefore, it was possible to alter, but not abort, an early FIV infection with prolonged, high-dose D4API treatment.

Acyclic nucleotide analogs derived from 8-azapurines: synthesis and antiviral activity

Reaction of phosphoroorganic synthons with 8-azaadenine, 8-aza-2, 6-diaminopurine, and 8-azaguanine using cesium carbonate yielded regioisomeric 8-azapurine N7-, N8-, and N9-(2-(phosphonomethoxy)alkyl) derivatives. This reaction followed by deprotection afforded isomeric 2-(phosphonomethoxy)ethyl (PME), (S)-(3-hydroxy-2-(phosphonomethoxy)propyl) [(S)-HPMP], (S)-(3-flouro-2-(phosphonomethoxy)propyl) [(S)-FPMP], (S)-(2-(phosphonomethoxy)propyl) [(S)-PMP], and (R)-(2-(phosphonomethoxy)propyl) [(R)-PMP] derivatives. 13C NMR spectra were used for structural assignment of the regioisomers. None of the 8-isomers exhibited any antiviral activity against herpesviruses, Moloney murine sarcoma virus (MSV), and/or HIV. 9-(S)-HPMP-8-azaadenine (23) and PME-8-azaguanine (65) were active against HSV-1, HSV-2, and CMV at 0.2-7 micrograms/mL, VZV at 0.04-0.4 microgram/mL, and MSV (at 0.3-0.6 microgram/mL). PME-8-azaguanine (65) and (R)-PMP-8-azaguanine (71a) protected MT-4 and CEM cells against HIV-1- and HIV-2-induced cytopathicity at a concentration of approximately 2 micrograms/mL.

Chemotherapy of human immunodeficiency virus (HIV) infection: anti-HIV agents targeted at early stages in the virus replicative cycle

Several compounds have been identified that inhibit an early stage in the replicative cycle of the human immunodeficiency virus (HIV): i) virus adsorption: polysulfates, polysulfonates, polycarboxylates, polyphosphates, and polyoxometalates; or ii) virus-cell fusion: plant lectins, negatively charged albumins and betulinic acid derivatives; iii) virus fusion/uncoating: bicyclam derivatives; iv) reverse transcription: dideoxynucleoside analogues, acyclic nucleoside phosphonates and non-nucleoside reverse transcriptase inhibitors. In principle, HIV may develop resistance to any of these specific anti-HIV agents. However, virus breakthrough can be completely prevented if these agents, alone or in combination, are added to the HIV-infected cells from the beginning at sufficiently high ('knock-out') concentrations.