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.
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
Safety and pharmacokinetics of abacavir (1592U89) following oral administration of escalating single doses in human immunodeficiency virus type 1-infected adults.
Abacavir (1592U89) is a nucleoside analog reverse transcriptase inhibitor that has been demonstrated to have selective activity against human immunodeficiency virus (HIV) in vitro and favorable safety profiles in mice and monkeys. A phase I study was conducted to evaluate the safety and pharmacokinetics of abacavir following oral administration of single escalating doses (100, 300, 600, 900, and 1,200 mg) to HIV-infected adults. In this double-blind, placebo-controlled study, subjects with baseline CD4+ cell counts ranging from < 50 to 713 cells per mm3 (median, 315 cells per mm3) were randomly assigned to receive abacavir (n = 12) or placebo (n = 6). The bioavailability of the caplet formulation relative to that of the oral solution was also assessed with the 300-mg dose. Abacavir was well tolerated by all subjects; mild to moderate asthenia, abdominal pain, headache, diarrhea, and dyspepsia were the most frequently reported adverse events, and these were not dose related. No significant clinical or laboratory abnormalities were observed throughout the study. All doses resulted in mean abacavir concentrations in plasma that exceeded the mean 50% inhibitory concentration (IC50) for clinical HIV isolates in vitro (0.07 microgram/ml) for almost 3 h. Abacavir was rapidly absorbed following oral administration, with the time to the peak concentration in plasma occurring at 1.0 to 1.7 h postdosing. Mean maximum concentrations in plasma (Cmax) and the area under the plasma concentration-time curve from time zero to infinity (AUC0-infinity) increased slightly more than proportionally from 100 to 600 mg (from 0.6 to 4.7 micrograms/ml for Cmax; from 1.0 to 15.7 micrograms.h/ml for AUC0-infinity) but increased proportionally from 600 to 1,200 mg (from 4.7 to 9.6 micrograms/ml for Cmax; from 15.7 to 32.8 micrograms.h/ml for AUC0-infinity. The elimination of abacavir from plasma was rapid, with an apparent elimination half-life of 0.9 to 1.7 h. Abacavir was well absorbed, with a relative bioavailability of the caplet formulation of 96% versus that of an oral solution (drug substance in water). In conclusion, this study showed that abacavir is safe and is well tolerated by HIV-infected subjects and demonstrated predictable pharmacokinetic characteristics when it was administered as single oral doses ranging from 100 to 1,200 mg. (+info
Safety and single-dose pharmacokinetics of abacavir (1592U89) in human immunodeficiency virus type 1-infected children.
Abacavir (formerly 1592U89) is a potent 2'-deoxyguanosine analog reverse transcriptase inhibitor that has been demonstrated to have a favorable safety profile in initial clinical trials with adults with human immunodeficiency virus (HIV) type 1 infection. A phase I study was conducted to evaluate the pharmacokinetics and safety of abacavir following the administration of two single oral doses (4 and 8 mg/kg of body weight) to 22 HIV-infected children ages 3 months to 13 years. Plasma was collected for analysis at predose and at 0.5, 1, 1.5, 2, 2.5, 3, 5, and 8 h after the administration of each dose. Plasma abacavir concentrations were determined by high-performance liquid chromatography, and data were analyzed by noncompartmental methods. Abacavir was well tolerated by all subjects. The single abacavir-related adverse event was rash, which occurred in 2 of 22 subjects. After administration of the oral solution, abacavir was rapidly absorbed, with the time to the peak concentration in plasma occurring within 1.5 h postdosing. Pharmacokinetic parameter estimates were comparable among the different age groups for each dose level. The mean maximum concentration in plasma (Cmax) and the mean area under the curve from time zero to infinity (AUC0-infinity) increased by 16 and 45% more than predicted, respectively, as the abacavir dose was doubled from 4 to 8 mg/kg (Cmax increased from 1.69 to 3.94 micrograms/ml, and AUC0-infinity increased from 2.82 to 8.09 micrograms.h/ml). Abacavir was rapidly eliminated, with a mean elimination half-life of 0.98 to 1.13 h. The mean apparent clearance from plasma decreased from 27.35 to 18.88 ml/min/kg as the dose increased. Neither body surface area nor creatinine clearance were correlated with pharmacokinetic estimates at either dose. The extent of exposure to abacavir appears to be slightly lower in children than in adults, with the comparable unit doses being based on body weight. In conclusion, this study showed that abacavir is safe and well tolerated in children when it is administered as a single oral dose of 4 or 8 mg/kg. (+info
Suppression of replication of multidrug-resistant HIV type 1 variants by combinations of thymidylate synthase inhibitors with zidovudine or stavudine.
The replication of recombinant multidrug-resistant HIV-1 clones modeled on clinically derived resistant HIV-1 strains from patients receiving long-term combination therapy with zidovudine (AZT) plus 2',3'-dideoxycytidine was found to regain sensitivity to AZT and stavudine (D4T) as a consequence of a pharmacologically induced decrease in de novo dTMP synthesis. The host-cell system used was phytohemagglutinin-stimulated peripheral blood mononuclear cells; dTMP and dTTP depletion were induced by single exposures to a low level of the thymidylate synthase inhibitor 5-fluorouracil (5-FU) or its deoxynucleoside, 2'-deoxy-5-fluorouridine. The host-cell response to the latter was biphasic: a very rapid decrease in the rate of de novo dTMP formation and, consequently, in intracellular dTTP pools, followed by slower recovery in both indices over 3 to 24 h. With the additional presence of AZT or D4T, however, replication of the multidrug-resistant HIV-1 strains remained inhibited, indicating dependence of HIV DNA chain termination by AZT-5'-monophosphate or 2',3'-didehydro-2', 3'-dideoxythymidine-5'-monophosphate in these resistant strains on simultaneous inhibition of host-cell de novo synthesis of thymidine nucleotides. No effect on viability of control (uninfected) phytohemagglutinin-stimulated/peripheral blood mononuclear cells was noted on 6-day exposures to 5-FU or 2'-deoxy-5-fluorouridine alone or in combination with AZT or D4T, even at drug levels severalfold higher than those used in the viral inhibition studies. These studies may provide useful information for the potential clinical use of AZT/5-FU or D4T/5-FU combinations for the prevention or reversal of multidrug resistance associated with long-term dideoxynucleoside combination therapy. (+info
Functional analysis of mutations conferring lamivudine resistance on hepatitis B virus.
Two patterns of mutation are commonly observed in the polymerase gene of lamivudine [(-)2'-deoxy-3'-thiacytidine]-resistant hepatitis B virus (HBV). The M539I substitution in the conserved YMDD motif occurs independently of other changes, whereas the M539V substitution is associated with an additional upstream change (L515M). These mutations were introduced into a common background and their effects on HBV DNA replication and lamivudine resistance studied. The L515M and M539V mutations provided only partial resistance while the M539I mutation conferred a high degree of lamivudine resistance. The combination of the L515M and M539V mutations gave an intermediate level of replication competence, compared with either mutation alone, and increased resistance to lamivudine. This probably accounts for these two mutations always being observed together. The M539I mutation reduced replication competence. (+info
The cost-effectiveness of treatment with lamivudine and zidovudine compared with zidovudine alone: a comparison of Markov model and trial data estimates.
In this paper, we present a Markov model for estimating the cost-effectiveness of combination therapy with lamivudine (LMV) and zidovudine (ZDV) compared with ZDV alone. We also compare the predictions of the Markov model for the impact of combination therapy on trial period costs with the actual impact of combination therapy on selected trial period costs estimated from data collected during the clinical trials. In the Markov model, disease stages were defined by CD4 cell count. Based on clinical trial data for patients with CD4 counts higher than 100 cells/mm3, the model assumed that the CD4 cell count level could be maintained above the level at the initiation of therapy for 6.5 months with monotherapy and for 18 months with combination therapy. After this period, transition rates for natural disease progression were used. Incremental lifetime costs and quality-adjusted life years gained with LMV/ZDV compared with ZDV alone were estimated for cohorts of patients initiating antiretroviral therapy at four different CD4 cell count stages. Cost per life year gained varied from $10,000 to $18,000, and cost per quality-adjusted life year gained varied from $14,000 to $27,000. In both cases, the combination therapy was more cost-effective when started earlier in disease progression. These estimates were not sensitive to changes in key parameter values. In addition, the model was used to estimate the impact of combination therapy on healthcare costs during the trial period; these estimated costs were compared with data on the cost of resource use collected during the clinical trial for hospital stays, unscheduled visits, medications, and outpatient procedures. Both the Markov model estimates and the trial data estimates for the trial period showed cost savings in other medical costs, though these were not large enough to completely offset the increased cost for antiretroviral therapy. The model estimates were more conservative than the estimates based on the trial data. (+info
Antiviral effect and pharmacokinetic interaction between nevirapine and indinavir in persons infected with human immunodeficiency virus type 1.
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)
Genotypic resistance and the treatment of HIV-1 infection in Espirito Santo, Brazil.
Before December 1997, in Espirito Santo, Brazil, combination antiretroviral therapy was used without routine virologic or immunologic monitoring. To examine consequences of therapy in this setting, clinical information, human immunodeficiency virus type 1 (HIV-1) RNA levels, CD4 cell counts, and protease and reverse transcriptase sequences were determined for consecutive HIV-1-infected outpatients. Of 48 treatment-naive individuals, 11 were started on therapy for HIV-related symptoms; however, 44 (92%) had an RNA level >20,000 copies/mL, a CD4 cell count <500/mm3, or symptoms. Eighteen (51%) of 35 patients on therapy had an RNA level >20,000 copies/mL. Nucleoside-resistance mutations were observed in 21 (68%) of 31 nucleoside-experienced subjects. Protease mutations necessary for high-level protease inhibitor (PI) resistance were present together with permissive mutations in 3 of 10 PI-experienced patients. Inability to identify high-risk individuals and to detect virologic failure may limit the effectiveness of antiretroviral drug programs and may promote the spread of drug resistance where virologic and immunologic monitoring are not available. (+info