Inhibition of human immunodeficiency virus type 1 replication by combination of transcription inhibitor K-12 and other antiretroviral agents in acutely and chronically infected cells.
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8-Difluoromethoxy-1-ethyl-6-fluoro-1,4-dihydro-7-[4-(2-methoxyp hen yl)-1- piperazinyl]-4-oxoquinoline-3-carboxylic acid (K-12) has recently been identified as a potent and selective inhibitor of human immunodeficiency virus type 1 (HIV-1) transcription. In this study, we examined several combinations of K-12 and other antiretroviral agents for their inhibitory effects on HIV-1 replication in acutely and chronically infected cell cultures. Combinations of K-12 and a reverse transcriptase (RT) inhibitor, either zidovudine, lamivudine, or nevirapine, synergistically inhibited HIV-1 replication in acutely infected MT-4 cells. The combination of K-12 and the protease inhibitor nelfinavir (NFV) also synergistically inhibited HIV-1, whereas the synergism of this combination was weaker than that of the combinations with the RT inhibitors. K-12 did not enhance the cytotoxicities of RT and protease inhibitors. Synergism of the combinations was also observed in acutely infected peripheral blood mononuclear cells. The combination of K-12 and cepharanthine, a nuclear factor kappa B inhibitor, synergistically inhibited HIV-1 production in tumor necrosis factor alpha-stimulated U1 cells, a promonocytic cell line chronically infected with the virus. In contrast, additive inhibition was observed for the combination of K-12 and NFV. These results indicate that the combinations of K-12 and clinically available antiretroviral agents may have potential as chemotherapeutic modalities for the treatment of HIV-1 infection. (+info)
Antiviral effect and pharmacokinetic interaction between nevirapine and indinavir in persons infected with human immunodeficiency virus type 1.
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Nevirapine and indinavir have the potential of affecting the pharmacokinetics of each other. In a prospective trial, 24 human immunodeficiency virus (HIV)-infected subjects on stable nucleoside or no therapy were treated with 800 mg of indinavir every 8 h. After 7 days, 200 mg of nevirapine a day was added for 14 days and then increased to 200 mg twice a day. At day 7 (before nevirapine), there was a sevenfold difference among the subjects in indinavir area under the curve (AUC), and there was a significant correlation between indinavir AUC (r2=0.378, P=.019), minimum plasma concentration (Cmin; r2=0.359, P=.023), maximum plasma concentration (Cmax; r2=0.340, P=.028), and plasma HIV RNA decline. Nevirapine significantly reduced median indinavir Cmin (47.5%) and AUC (27.4%) and, to a lesser extent, Cmax (11%). Plasma HIV RNA values were +info)
Clinical resistance patterns and responses to two sequential protease inhibitor regimens in saquinavir and reverse transcriptase inhibitor-experienced persons.
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The efficacy of sequential protease inhibitor therapy was studied in 16 human immunodeficiency virus (HIV) 1-infected persons in whom saquinavir with multiple nucleoside reverse transcriptase (RT) inhibitors (NRTI) had failed. Nelfinavir plus two NRTIs (new or continued) resulted in minimal (0.59 log RNA copies/mL) and transient (8 weeks) suppression of plasma HIV RNA levels. Rapid failure was surprisingly associated with baseline presence of protease gene mutation L90M (P=.04) in the absence of D30N and with RT mutations D67N (P<.01), K70R/S (P=.02), and K219Q/W/R/E (P<.01). Ten patients were subsequently switched to indinavir plus nevirapine and 2 NRTIs, resulting in a median 1.62 log reduction in plasma HIV RNA, with 3 patients maintaining 400 copies/mL for 24 weeks. These results suggest that nelfinavir may have limited utility after saquinavir failure, particularly without potent concomitant therapy. Combining an NRTI with a new protease inhibitor for rescue may improve response. (+info)
Novel four-drug salvage treatment regimens after failure of a human immunodeficiency virus type 1 protease inhibitor-containing regimen: antiviral activity and correlation of baseline phenotypic drug susceptibility with virologic outcome.
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Twenty human immunodeficiency virus-infected patients experiencing virologic failure of an indinavir- or ritonavir-containing treatment regimen were evaluated in a prospective, open-label study. Subjects received nelfinavir, saquinavir, abacavir, and either another nucleoside analog (n=10) or nevirapine (n=10). Patients treated with the nevirapine-containing regimen experienced significantly greater virologic suppression at week 24 than those not treated with nevirapine (P=.04). Baseline phenotypic drug susceptibility was strongly correlated with outcome in both treatment arms. Subjects with baseline virus phenotypically sensitive to 2 or 3 drugs in the salvage regimen experienced significantly greater virus load suppression than those with baseline virus sensitive to 0 or 1 drug (median week-24 change=-2.24 log and -0.35 log, respectively; P=.01). In conclusion, non-nucleoside reverse transcriptase inhibitors may represent a potent drug in salvage therapy regimens after failure of an indinavir or ritonavir regimen. Phenotypic resistance testing may provide a useful tool for selecting more effective salvage regimens. (+info)
Susceptibility of lamivudine-resistant hepatitis B virus to other reverse transcriptase inhibitors.
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The emergence of resistant hepatitis B virus (HBV), with mutations in the YMDD motif of the polymerase gene after treatment with lamivudine, is becoming an important clinical problem. In this study, susceptibility of wild-type and lamivudine-resistant HBV M552I, M552V, and L528M/M552V mutants to other reverse transcriptase inhibitors was investigated by transient transfection of full-length HBV DNA into human hepatoma cells. HBV DNA replication was monitored by Southern blot hybridization, which showed the presence of a single-stranded band (representative of the HBV replicative intermediates) in the drug-free, wild-type HBV-transfected cells. This band was diminished in the samples of wild-type HBV DNA treated with either lamivudine, adefovir, or lobucavir. The band intensities from the lamivudine-resistant mutants were not decreased by treatment with lamivudine, but were decreased by the treatments with adefovir or lobucavir. In contrast, penciclovir and nevirapine did not diminish the intensity of the single-stranded band of wild-type HBV or the lamivudine-resistant mutants. These results demonstrate that lamivudine-resistant HBV is susceptible to adefovir and lobucavir. Lamivudine-resistant HBV should be treated with adefovir or lobucavir, and combination therapy with lamivudine and adefovir/lobucavir may prevent the emergence of lamivudine-resistant HBV. (+info)
Reverse transcriptase inhibitors can selectively block the synthesis of differently sized viral DNA transcripts in cells acutely infected with human immunodeficiency virus type 1.
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We have recently reported that the in vitro inhibition of human immunodeficiency virus type 1 (HIV-1) reverse transcription by inhibitors of reverse transcriptase (RT) occurred most efficiently when the expected DNA products of RT reactions were long (Quan et al. , Nucleic Acids Res. 26:5692-5698, 1998). Here, we have used a quantitative PCR to analyze HIV-1 reverse transcription within acutely infected cells treated with RT inhibitors. We found that levels of minus-strand strong-stop DNA [(-)ssDNA] formed in acutely infected MT2 cells were only slightly reduced if cells were infected with viruses that had been generated in the presence of either azidothymidine or nevirapine (5 microM) and maintained in the presence of this drug throughout the viral adsorption period and thereafter. Control experiments in which virus inoculation of cells was performed at 4 degrees C, followed directly by cell extraction, showed that less than 1% of total (-)ssDNA within acutely infected cells was attributable to its presence within adsorbed virions. In contrast, synthesis of intermediate-length reverse-transcribed DNA products decreased gradually as viral DNA strand elongation took place in the presence of either of these inhibitors. This establishes that nucleoside and nonnucleoside RT inhibitors can exert similar temporal impacts in regard to inhibition of viral DNA synthesis. Generation of full-length viral DNA, as expected, was almost completely blocked in the presence of these antiviral drugs. These results provide insight into the fact that high concentrations of drugs are often needed to yield inhibitory effects in cell-free RT assays performed with short templates, whereas relatively low drug concentrations are often strongly inhibitory in cellular systems. (+info)
Disposition and biotransformation of the antiretroviral drug nevirapine in humans.
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The pharmacokinetics and biotransformation of the antiretroviral agent nevirapine (NVP) after autoinduction were characterized in eight healthy male volunteers. Subjects received 200-mg NVP tablets once daily for 2 weeks, followed by 200 mg twice daily for 2 weeks. Then they received a single oral dose (solution) of 50 mg containing 100 microCi of [(14)C]NVP. Biological fluids were analyzed for total radioactivity, parent compound (HPLC/UV), and metabolites (electrospray liquid chromatography/mass spectroscopy and liquid chromatography/tandem mass spectroscopy). Mean recovery of radioactivity was 91.4%, with 81.3% excreted in urine and 10.1% recovered in the feces over a period of 10 days. Circulating radioactivity was evenly distributed between whole blood and plasma. At maximum plasma concentration, parent compound accounted for approximately 75% of the circulating radioactivity. Mean plasma elimination half-lives for total radioactivity and NVP were 21.3 and 20.0 h, respectively. Several metabolites were identified in urine including 2-hydroxynevirapine glucuronide (18.6%), 3-hydroxynevirapine glucuronide (25.7%), 12-hydroxynevirapine glucuronide (23.7%), 8-hydroxynevirapine glucuronide (1.3%), 3-hydroxynevirapine (1.2%), 12-hydroxynevirapine (0.6%), and 4-carboxynevirapine (2.4%). Greater than 80% of the radioactivity in urine was made up of glucuronidated conjugates of hydroxylated metabolites of NVP. Thus, cytochrome P-450 metabolism, glucuronide conjugation, and urinary excretion of glucuronidated metabolites represent the primary route of NVP biotransformation and elimination in humans. Only a small fraction of the dose (2.7%) was excreted in urine as parent compound. (+info)
Sequence clusters in human immunodeficiency virus type 1 reverse transcriptase are associated with subsequent virological response to antiretroviral therapy.
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Many amino acid (aa) sites in reverse transcriptase (RT) have been implicated in resistance to nucleoside (NRTI) and nonnucleoside antiretrovirals. Interactions between these in response to combination therapy remain poorly understood. In a trial (ACTG 241) of zidovudine/didanosine (ddI) versus zidovudine/ddI/nevirapine in nucleoside-experienced patients, baseline sequence data from the RT coding region was analyzed from 55 individuals. Sequences were clustered by use of a parsimony method and the virological responses (ratio of baseline viral load to viral load after of therapy) for each cluster were analyzed at week 8 and week 48. Both clusters and genotype at aa 215 were significantly associated with virological response at both time points, whereas viral load showed a stronger association with sequence clusters. Sequence clusters identified one group of patients who never developed high-level resistance to NRTIs despite prior nucleoside exposure and poor suppression of viral replication. (+info)