HIV-1 protease inhibitors

A Review of FDA-Approved Anti-HIV-1 Drugs, Anti-Gag Compounds, and Potential Strategies for HIV-1 Eradication

Acquired immunodeficiency syndrome (AIDS) is an enormous global health threat stemming from human immunodeficiency virus (HIV-1) infection. Up to now, the tremendous advances in combination antiretroviral therapy (cART) have shifted HIV-1 infection from a fatal illness into a manageable chronic disorder. However, the presence of latent reservoirs, the multifaceted nature of HIV-1, drug resistance, severe off-target effects, poor adherence, and high cost restrict the efficacy of current cART targeting the distinct stages of the virus life cycle. Therefore, there is an unmet need for the discovery of new therapeutics that not only bypass the limitations of the current therapy but also protect the body's health at the same time. The main goal for complete HIV-1 eradication is purging latently infected cells from patients' bodies. A potential strategy called "lock-in and apoptosis" targets the budding phase of the life cycle of the virus and leads to susceptibility to apoptosis of HIV-1 infected cells for the elimination of HIV-1 reservoirs and, ultimately, for complete eradication. The current work intends to present the main advantages and disadvantages of United States Food and Drug Administration (FDA)-approved anti-HIV-1 drugs as well as plausible strategies for the design and development of more anti-HIV-1 compounds with better potency, favorable pharmacokinetic profiles, and improved safety issues.

Genetic Diversity and Low Therapeutic Impact of Variant-Specific Markers in HIV-1 Pol Proteins

The emergence and spread of new HIV-1 variants pose a challenge for the effectiveness of antiretrovirals (ARV) targeting Pol proteins. During viral evolution, non-synonymous mutations have fixed along the viral genome, leading to amino acid (aa) changes that can be variant-specific (V-markers). Those V-markers fixed in positions associated with drug resistance mutations (DRM), or R-markers, can impact drug susceptibility and resistance pathways. All available HIV-1 Pol sequences from ARV-naïve subjects were downloaded from the United States Los Alamos HIV Sequence Database, selecting 59,733 protease (PR), 6,437 retrotranscriptase (RT), and 6,059 integrase (IN) complete sequences ascribed to the four HIV-1 groups and group M subtypes and circulating recombinant forms (CRFs). Using a bioinformatics tool developed in our laboratory (EpiMolBio), we inferred the consensus sequences for each Pol protein and HIV-1 variant to analyze the aa conservation in Pol. We analyzed the Wu–Kabat protein variability coefficient (WK) in PR, RT, and IN group M to study the susceptibility of each site to evolutionary replacements. We identified as V-markers the variant-specific aa changes present in >75% of the sequences in variants with >5 available sequences, considering R-markers those V-markers that corresponded to DRM according to the IAS-USA2019 and Stanford-Database 9.0. The mean aa conservation of HIV-1 and group M consensus was 82.60%/93.11% in PR, 88.81%/94.07% in RT, and 90.98%/96.02% in IN. The median group M WK was 10 in PR, 4 in RT, and 5 in IN. The residues involved in binding or catalytic sites showed a variability <0.5%. We identified 106 V-markers: 31 in PR, 28 in RT, and 47 in IN, present in 11, 12, and 13 variants, respectively. Among them, eight (7.5%) were R-markers, present in five variants, being minor DRM with little potential effect on ARV susceptibility. We present a thorough analysis of Pol variability among all HIV-1 variants circulating to date. The relatively high aa conservation observed in Pol proteins across HIV-1 variants highlights their critical role in the viral cycle. However, further studies are needed to understand the V-markers’ impact on the Pol proteins structure, viral cycle, or treatment strategies, and periodic variability surveillance studies are also required to understand PR, RT, and IN evolution.

Analysis of virological response to therapy and resistance profile in treatment-experienced and naive HIV-1 infected Romanian patients receiving regimens containing darunavir boosted with ritonavir or cobicistat

77% of Romanians infected with HIV receive antiretroviral therapy, with the challenge of maintaining long-term therapeutic success (the viral load becoming/remaining undetectable). The main purpose of this study was to provide comparative analysis of the long-term virological response to therapeutic regimens containing pharmacokinetically enhanced darunavir (DRV) with ritonavir (RTV) or cobicistat (COBI). The second aim was to evaluate the viral resistance profile to therapy, by number/type/frequency of viral mutations. This retrospective study was conducted on 462 patients infected with subtype F HIV-1, registered at the "Matei Bals" National Institute of Infectious Diseases, between 2018 and 2021: 384 patients received (among other ARV) DRV 600 mg, enhanced with RTV 100 mg (twice daily) and 78 patients received DRV 800 mg boosted with COBI 150 mg (once daily). The virological response was measured by determining the viral load (HIV-1 RNA copies/mL), while the incidence of viral resistance to therapy was assessed by genotyping tests. Comparing the patients with undetectable viremia, from the 1st visit to the 3rd one, the outcomes showed that at the last visit, 84.6% subjects in the DRV/c group achieved virological efficiency over those from DRV/r group (76.8%). The differences observed between this time points are statistically significant p < 0.05. DRV/c administered in combination with other ARV, in subtype F HIV-1 infected patients, proved to be more virologically effective, maintaining a favorable long-time result. When comparing the outcomes of the two groups, a statistically significant difference of p < 0.05 was obtained. 32 patients (27 from DRV/r group and 5 from DRV/c group) were evaluated with persistent HIV-1 ARN plasma load > 1000 copies/mL, during all 3 clinical visits. They formed a research sub-group evaluated in terms of resistance to therapy and were reported as virological failures. 28.12% of the sub-group with persistent HIV-1 RNA > 1000 copies/mL were from the DRV/r group and only 3.12% from the DRV/c group. Drug mutations (DRM) involved in antiretroviral resistance/sensitivity occurred both in the protease gene, and in the reverse transcriptase gene, with the involved ARV classes being protease inhibitors, nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors. 16 different types of mutations were evaluated in the PR gene and 20 mutations were evaluated in RT gene.

Repurposing antiviral drugs against HTLV-1 protease by molecular docking and molecular dynamics simulation

Human T-cell leukemia virus type I (HTLV-1) belongs to the delta retrovirus family and the etiological agent of adult T-cell leukemia (ATL(. While the current HTLV-1 therapy, relies on using Zidovudine plus IFN-γ, there is no FDA approved drugs against it. In silico drug repurposing is a fast and accurate way for screening US-FDA approved drugs to find a therapeutic option for the HTLV-1 infection. So that, this research aims to analyze a dataset of approved antiviral drugs as a potential prospect for an anti-viral drug against HTLV-1 infection. Molecular docking simulation was performed to identify interactions of the antiviral drugs with the key residues in the HTLV-1 protease binding site. Then, molecular dynamics simulation was also performed for the potential protein-ligand complexes to confirm the stable behavior of the ligands inside the binding pocket. The best docking scores with the target was found to be Simeprevir, Atazanavir, and Saquinavir compounds which indicate that these drugs can firmly bind to the HTLV-1 protease. The MD simulation confirmed the stability of Simeprevir-protease, Atazanavir-Protease, and Saquinavir-Protease interactions. Clearly, these compounds should be further evaluated in experimental assays and clinical trials to confirm their actual activity against HTLV-1 infection.Communicated by Ramaswamy H. Sarma.

Comparative analysis of the unbinding pathways of antiviral drug Indinavir from HIV and HTLV1 proteases by supervised molecular dynamics simulation

Determining the unbinding pathways of potential small molecule compounds from their target proteins is of great significance for designing efficacious treatment solutions. One of these potential compounds is the approved HIV-1 protease inhibitor, Indinavir, which has a weak effect on the HTLV-1 protease. In this work, by employing the SuMD method, we reconstructed the unbinding pathways of Indinavir from HIV and HTLV-1 proteases to compare and understand the mechanism of the unbinding and to discover the reasons for the lack of inhibitory activity of Indinavir against the HTLV-1 protease. We achieved multiple unbinding events from both HIV and HTLV-1 proteases in which the RMSD values of Indinavir reached over 40 Å. Also, we found that the mobility and fluctuations of the flap region are higher in the HTLV-1 protease, making the drug less stable. We realized that critically positioned aromatic residues such as Trp98/Trp98' and Phe67/Phe67' in the HTLV-1 protease could make strong π-Stacking interactions with Indinavir in the unbinding pathway, which are unfavorable for the stability of Indinavir in the active site. The details found in this study can make a reasonable explanation for the lack of inhibitory activity of this drug against HTLV-1 protease. We believe the details discovered in this work can help design more effective and selective inhibitors for the HTLV-1 protease.

Biochemical Characterization, Specificity and Inhibition Studies of HTLV-1, HTLV-2, and HTLV-3 Proteases

The human T-lymphotropic viruses (HTLVs) are causative agents of severe diseases including adult T-cell leukemia. Similar to human immunodeficiency viruses (HIVs), the viral protease (PR) plays a crucial role in the viral life-cycle via the processing of the viral polyproteins. Thus, it is a potential target of anti-retroviral therapies. In this study, we performed in vitro comparative analysis of human T-cell leukemia virus type 1, 2, and 3 (HTLV-1, -2, and -3) proteases. Amino acid preferences of S4 to S1′ subsites were studied by using a series of synthetic oligopeptide substrates representing the natural and modified cleavage site sequences of the proteases. Biochemical characteristics of the different PRs were also determined, including catalytic efficiencies and dependence of activity on pH, temperature, and ionic strength. We investigated the effects of different HIV-1 PR inhibitors (atazanavir, darunavir, DMP-323, indinavir, ritonavir, and saquinavir) on enzyme activities, and inhibitory potentials of IB-268 and IB-269 inhibitors that were previously designed against HTLV-1 PR. Comparative biochemical analysis of HTLV-1, -2, and -3 PRs may help understand the characteristic similarities and differences between these enzymes in order to estimate the potential of the appearance of drug-resistance against specific HTLV-1 PR inhibitors.

Recent Advances in the Development of Integrase Inhibitors for HIV Treatment

PURPOSE OF THE REVIEW

The complex multistep life cycle of HIV allows it to proliferate within the host and integrate its genome in to the host chromosomal DNA. This provirus can remain dormant for an indefinite period. The process of integration, governed by integrase (IN), is highly conserved across the Retroviridae family. Hence, targeting integration is not only expected to block HIV replication but may also reveal new therapeutic strategies to treat HIV as well as other retrovirus infections.

RECENT FINDINGS

HIV integrase (IN) has gained attention as the most promising therapeutic target as there are no equivalent homologues of IN that has been discovered in humans. Although current nano-formulated long-acting IN inhibitors have demonstrated the phenomenal ability to block HIV integration and replication with extraordinary half-life, they also have certain limitations. In this review, we have summarized the current literature on clinically established IN inhibitors, their mechanism of action, the advantages and disadvantages associated with their therapeutic application, and finally current HIV cure strategies using these inhibitors.

N-p-Tosyl-L-phenylalanine chloromethyl ketone (TPCK) inhibits HIV-1 by suppressing the activity of viral protease

Human Immunodeficiency Virus (HIV), the etiological agent for Acquired Immunodeficiency Syndrome (AIDS), continues to kill humans despite stupendous advances in antiviral research. With the presently available combination antiretroviral therapeutic arsenal, AIDS is now a manageable disease but with no cure available till date. The development of novel antivirals consumes an extensive amount of time and resources. Hence, repurposing of the established gold standard molecules for their anti-HIV application is enormously advantageous. In this study, we report that N-p-Tosyl-L-phenylalanine chloromethyl ketone (TPCK) inhibits HIV-1 replication in a highly-conserved manner. Further, TPCK inhibits HIV-1 replication at the late stages of its life cycle by impeding viral protease (PR) enzyme activity. Additionally, our results demonstrate that the combination of TPCK with established HIV-1 PR inhibitors shows significant synergistic inhibitory potential, suggesting the potential use of TPCK in cART regimen. Collectively, we report the anti-HIV activity of TPCK, which should be further characterized for its translational applications.

The Signaling Pathways, and Therapeutic Targets of Antiviral Agents: Focusing on the Antiviral Approaches and Clinical Perspectives of Anthocyanins in the Management of Viral Diseases

As the leading cause of death worldwide, viruses significantly affect global health. Despite the rapid progress in human healthcare, there are few viricidal and antiviral therapies that are efficient enough. The rapid emergence of resistance, and high costs, as well as the related side effects of synthetic antiviral drugs, raise the need to identify novel, effective, and safe alternatives against viral diseases. Nature has been of the most exceptional help and source of inspiration for developing novel multi-target antiviral compounds, affecting several steps of the viral life cycle and host proteins. For that matter and due to safety and efficacy limitations, as well as high resistance rate of conventional therapies, hundreds of natural molecules are preferred over the synthetic drugs. Besides, natural antiviral agents have shown acceptable antiviral value in both preclinical and clinical trials.This is the first review regarding molecular and cellular pathways of the virus life cycle, treatment strategies, and therapeutic targets of several viral diseases with a particular focus on anthocyanins as promising natural compounds for significant antiviral enhancements. Clinical applications and the need to develop nano-formulation of anthocyanins in drug delivery systems are also considered.

Fullerene Derivatives Strongly Inhibit HIV-1 Replication by Affecting Virus Maturation without Impairing Protease Activity

Three compounds (1, 2, and 3) previously reported to inhibit HIV-1 replication and/or in vitro activity of reverse transcriptase were studied, but only fullerene derivatives 1 and 2 showed strong antiviral activity on the replication of HIV-1 in human CD4(+) T cells. However, these compounds did not inhibit infection by single-round infection vesicular stomatitis virus glycoprotein G (VSV-G)-pseudotyped viruses, indicating no effect on the early steps of the viral life cycle. In contrast, analysis of single-round infection VSV-G-pseudotyped HIV-1 produced in the presence of compound 1 or 2 showed a complete lack of infectivity in human CD4(+) T cells, suggesting that the late stages of the HIV-1 life cycle were affected. Quantification of virion-associated viral RNA and p24 indicates that RNA packaging and viral production were unremarkable in these viruses. However, Gag and Gag-Pol processing was affected, as evidenced by immunoblot analysis with an anti-p24 antibody and the measurement of virion-associated reverse transcriptase activity, ratifying the effect of the fullerene derivatives on virion maturation of the HIV-1 life cycle. Surprisingly, fullerenes 1 and 2 did not inhibit HIV-1 protease in an in vitro assay at the doses that potently blocked viral infectivity, suggesting a protease-independent mechanism of action. Highlighting the potential therapeutic relevance of fullerene derivatives, these compounds block infection by HIV-1 resistant to protease and maturation inhibitors.

Infectomics Screening for Novel Antiviral Drug Targets

Preclinical Research

Copyright 2012 Wiley-Liss, Inc., A Wiley Company

Infectomics, a novel way to globally and comprehensively understand the interactions between microbial pathogens and their hosts, has significantly expanded understanding of the microbial infections. The infectomics view of viral–host interactions on the viral perspective principally focuses on gene acquisition, deletion, and point mutation, while traditional antiviral drug discovery concentrates on viral encoding proteins. Recently, high‐throughput technologies, such as mass spectrometry‐based proteomics, activity‐based protein profiling, microarray analysis, yeast two‐hybrid assay, small interfering RNA screening, and micro RNA profiling, have been gradually employed in the research of virus–host interactions. Besides, signaling pathways and cellular processes involved in viral–host interactions provide new insights of infectomics in antiviral drug discovery. In this review, we summarize related infectomics approaches in the studies of virus–host interactions, which shed light on the development of novel antiviral drug targets screening.

Brain specific delivery of pegylated indinavir submicron lipid emulsions

The aim of this study was to develop stable parenteral pegylated indinavir submicron lipid emulsions (SLEs) for improving brain specific delivery. The O/W SLEs were prepared by homogenization and ultra sonication process. The sizes of oil globules varied from 241.5 to 296.4nm and zeta potential from -26.6 to -42.4mV. During in vitro drug release studies the cumulative amount of drug released within 12h from SLE-5, DSP2-3 and DPP5-3 was 71.8±0.76, 66.09±1.45 and 68.33±1.29, respectively. The total drug content and entrapment efficiencies were determined. The optimized formulations were stable for the effect of centrifugal stress, thermal stress, dilution stress and storage. In vivo pharmacokinetic and tissue distribution studies were performed in Swiss albino mice, the therapeutic availability (TA) of DSP2-3 was 3.59 times and 2.36 times in comparison to drug solution and SLE-5 respectively, where as DPP5-3 showed TA 2.8 and 1.84 times the drug solution and SLE-5, respectively. The brain to serum ratio of indinavir from DSP2-3 and DPP5-3 varied between 0.4 and 0.7 at all time points indicated the preferential accumulation of drug in brain. In conclusion, pegylated SLEs improved brain specific delivery of indinavir and will be useful in treating chronic HIV infection.

Central nervous system distribution kinetics of indinavir in rats

The central nervous system (CNS) distribution kinetics of indinavir were extensively evaluated using a combinational in-vivo model comprising the integration plot method (a single-passage approach) and neuropharmacokinetic method (a multiple-passage approach). A 5 mg kg−1 dose of indinavir was administered intravenously to rats. Blood and cerebrospinal fluid (CSF) samples and whole brain were collected from the animals at specified time points and the drug concentration in each sample was determined using a high-performance liquid chromatography method. For the neuropharmacokinetic study, the simultaneous plasma, CSF and brain concentrations were fitted to an integrated model, which resulted in the estimation of the influx (Kin) and efflux (Kout) rate constants of the drug to/from CSF and brain parenchyma. The integration plot method involved plotting the brainplasma or CSF-plasma concentration ratios (Kp,app) against AUC0r&#x030a;t/Cp(t), and estimating the uptake clearance of the drug by brain/CSF from the slope of the initial linear portion of the plot. The Kin and Kout values of the drug to/from CSF were estimated to be 2.42 times 10−2 and 13.26 times 10−2min−1, respectively, and the corresponding values for brain parenchyma were 1.02 times 10−2 and 1.32 times 10−2 min−1, respectively. The uptake clearances of indinavir by CSF and brain parenchyma were 8.89 and 8.38 μLmin−1 g−1, respectively. The permeability surface area products of the drug for the blood-brain barrier and blood-CSF barrier were estimated as 1.05 times 10−2 and 2.45 times 10−2 mL min−1 g−1, respectively. The estimated kinetic parameters indicated limited CNS entry of the drug because of the limited blood-brain barrier permeability and the efficient drug efflux from CNS, particularly from CSF.

Baseline CD4 cell count and outcome of pegylated interferon plus ribavirin therapy in HIV/hepatitis C virus-coinfected patients

OBJECTIVE

When to start hepatitis C treatment in HIV/hepatitis C virus (HCV)-coinfected patients remains unresolved. Our objective was to determine if a baseline CD4 count >/=350 cells/mm predicts a sustained HCV response to pegylated interferon plus ribavirin.

METHODS

We conducted a multicenter cohort study of HIV/HCV-coinfected patients treated for HIV in hospitals in Nice, Tourcoing, and Marseille (France). Sustained viral response (SVR) was defined as undetectable HCV RNA 24 weeks after treatment. The relation between CD4 cell count and SVR was examined separately for patients with HCV genotype 1 or non-1.

RESULTS

One hundred seventy-five patients were included. In patients with HCV genotype 1, the rate of SVR was 13% and was not related to baseline CD4 cell count (odds ratio [OR] = 1.0, 95% confidence interval [CI]: 0.1 to 9.3). In patients with HCV genotype non-1, the rate of SVR was 46% and was not significantly increased by a baseline CD4 count >/=350 cells/mm (OR = 1.8, 95% CI: 0.6 to 5.9).

CONCLUSIONS

Higher CD4 cell count at treatment initiation with pegylated interferon plus ribavirin did not improve treatment success probability, regardless of HCV genotype.

Bioavailability and Pharmacokinetic Model for Ritonavir in the Rat

The aim of this study is to investigate in vivo the oral bioavailability of ritonavir and to evaluate the pharmacokinetic model that best describes the plasma concentration behavior after oral and intravenous administration. Male Wistar rats were intravenously administered at 3 mg dose of pure ritonavir and oral administered at 4.6 +/- 2.5 mg of diluted Norvir. Blood samples were taken by means of the jugular vein for a 24 h period of time. An analytical high-performance liquid chromatography (HPLC) technique was developed in order to quantify ritonavir plasma concentrations. A nonlinear modeling approach was used to estimate the pharmacokinetic parameters of interest. Results showed that a two-compartmental model with zero-order kinetic in the incorporation process of ritonavir into the body better fitted intravenous and oral data. The estimated oral bioavailability by means of noncompartmental and compartmental approaches resulted in 74% and 76.4%, respectively. These values confirm the ones obtained by other authors in the rat. In conclusion, a zero-order kinetic in the incorporation process at the administered doses suggests the saturation of the possible specialized transport mechanisms involved in the incorporation of ritonavir into the body. These results could justify the use of low doses of ritonavir when improving the bioavailability of other protease inhibitors (PIs) is required.

Differential protein binding of indinavir and saquinavir in matched maternal and umbilical cord plasma

AIMS

To determine whether lower umbilical cord than maternal binding of indinavir and saquinavir contributed to the low cord : maternal (C : M) total concentration ratios reported previously.

METHODS

Indinavir and saquinavir unbound fraction (fu) was determined using equilibrium dialysis. Buffer solutions of human serum albumin (HSA) (20.0, 30.0, 40.0 g l(-1)) and alpha(1)-acid glycoprotein (AAG) (0.20, 0.60, 2.00 g l(-1)) were spiked with indinavir (1.00 and 8.00 mg l(-1)) or saquinavir (0.15 and 1.50 mg l(-1)). Matched maternal and umbilical cord plasma was spiked with 1.00 mg l(-1) indinavir (n = 12) or 0.15 mg l(-1) saquinavir (n = 20). Spiked protein/plasma solutions were dialyzed against isotonic phosphate buffer, at 37 degrees C. At equilibrium, indinavir and saquinavir concentrations were quantified, and the f(u) determined.

RESULTS

Indinavir and saquinavir demonstrated protein concentration-dependent binding in buffer solutions of HSA and AAG. Indinavir f(u) was significantly higher in umbilical cord (0.53 +/- 0.12) compared with maternal (0.36 +/- 0.11) plasma (95% CI of the difference -0.26, -0.097). Similarly, saquinavir fu was different between umbilical cord (0.0090 +/- 0.0046) and maternal plasma (0.0066 +/- 0.0039) (95% CI of the difference -0.0032, -0.0016). The transplacental AAG concentration gradient contributed significantly to the binding differential of both drugs.

CONCLUSIONS

The differential plasma binding of both drugs, which was largely the result of the transplacental AAG concentration gradient, would contribute to the low C : M total plasma concentration ratios observed previously. Unbound concentrations of indinavir and saquinavir are likely to be substantially lower in umbilical cord than maternal plasma.

Role of P-glycoprotein in tissue uptake of indinavir in rat

The effect of p-glycoprotein inhibition on tissue distribution of indinavir, an anti-HIV (human immunodeficiency virus) protease inhibitor drug, has been evaluated. Indinavir was co-administered intravenously in rats along with a p-glycoprotein inhibitor, PSC833, and the drug concentrations in plasma and various tissues were determined using a HPLC method. Additionally, initial uptake clearance of indinavir was evaluated in the brain and testes. The highest increasing effect of p-glycoprotein inhibition on the tissue uptake ratios of indinavir was found in central nervous system (CNS). The estimated tissue extraction the drug was indicative of (i) limited drug entry to brain parenchyma, which was increased significantly by p-glycoprotein inhibition, (ii) non-restricted drug entry to testes, heart and spleen, which was increased significantly in the case of heart and decreased in the case of testes and spleen as a result of p-glycoprotein inhibition, and (iii) drug accumulation in liver and small intestine and, to a lesser extent, kidney, which was not affected by p-glycoprotein inhibition. The uptake clearances of indinavir by brain parenchyma in PSC833-treated and control rats were 68.80+/-8.65 and 21.63+/-4.28 micro/min/g and the corresponding values for the testes were 39.84+/-4.90 and 36.65+/-2.54 microl/min/g. The difference was significant only in the case of brain parenchyma (P<0.001). These data showed that p-glycoprotein inhibition increases the CNS uptake of indinavir markedly and has some transient minor effects on drug uptake by some other tissues.

Simple and sensitive high-performance liquid chromatography method for the quantitation of indinavir in rat plasma and central nervous system

A simple and sensitive RP-HPLC method using UV detection (215 nm) was developed for the determination of indinavir concentrations in rat plasma, cerebrospinal fluid (CSF), and brain tissue homogenates. Biological samples were processed using a combination of acid pretreatment and liquid-liquid extraction with verapamil used as the internal standard. This method produced a linear response throughout the indinavir concentration range of 0.05-30 microM in plasma and 0.05-2.5 microM in CSF and brain with a LOD of 12.5 nM for plasma and CSF, and 6.25 nM for brain homogenate. Due to its high sensitivity, this assay is particularly useful for the quantitative determination of indinavir concentrations in brain and CSF.

Improved purification protocol for wild-type and mutant human foamy virus proteases

Wild-type and an active site mutant (S25T) human foamy virus (HFV) proteases were expressed in fusion with maltose binding protein in Escherichia coli. The mutant enzyme contained a Ser to Thr mutation in the -Asp-Ser-Gly- active site triplet of the enzyme, which forms the "fireman's grip" between the two subunits of the homodimeric enzyme. The fusion proteins were purified by affinity chromatography on amylose resin, cleaved with factor Xa, and the processed enzymes were purified by gel filtration under denaturing condition. Refolding after purification resulted in active enzymes with comparable yields. Furthermore, both enzymes showed similar catalytic activities in an oligopeptide substrate representing an HFV Gag cleavage site. However, the S25T mutant showed increased stability in urea unfolding experiment, in a good agreement with the suggested role of the Thr residue of fireman's grip.

Effects of the human immunodeficiency virus-protease inhibitor, ritonavir, on basal and catecholamine-stimulated lipolysis

Several of the aspartic acid protease inhibitors used to treat HIV infection increase basal lipolysis in adipocytes, but the cellular mechanisms leading to this augmentation are not well understood. We therefore studied the effects of chronic exposure to the HIV protease inhibitor, ritonavir, on the lipolytic cascade in 3T3-L1 adipocytes. Treatment of 3T3-L1 adipocytes with ritonavir for 14 d (during and after differentiation) enhanced basal, isoproterenol (Iso)-stimulated, and cAMP analog-stimulated lipolysis. Enhancement of lipolysis was observed after Iso at concentrations between 0.1 and 10 mum. Despite a significant decrease in cyclic nucleotide phosphodiesterase (PDE)3B activity and protein levels, there were no changes in Iso-stimulated intracellular cAMP, protein kinase A (PKA) expression, or PKA activity. Ritonavir-augmented lipolysis was also observed under conditions that reversed the effect on PDE3B activity via preincubation with 1 mum (-)-N(6)-(2-phenylisopropyl)adenosine. In ritonavir-treated cells, protein expression of the lipid droplet-protective protein, perilipin, was significantly decreased, whereas there was no change in hormone-sensitive lipase. Activation of ERK1/2 by Iso did not play a role in the augmentation. We conclude that ritonavir decreases PDE3B and perilipin protein expression and affects both basal and catecholamine-stimulated lipolysis in 3T3-L1 adipocytes primarily through actions at sites downstream of PKA.

Development of a capillary electrophoretic method for the separation of diastereoisomers of a new human immunodeficiency virus protease inhibitor

A capillary electrophoretic (CE) method was developed for the separation of diastereoisomers of a new human immunodeficiency virus (HIV) protease inhibitor TMC114. In total 16 isomers of this drug have been synthesized (eight pairs of enantiomers). We succeeded in the separation of the eight diastereoisomers, but no enantiomers could be separated. Because of the high similarity and water-insolubility of these isomers, the separation is a real challenge. Different CE modes were tried out: capillary zone electrophoresis (CZE), nonaqueous capillary electrophoresis (NACE), micellar electrokinetic capillary chromatography (MEKC), and microemulsion electrokinetic capillary chromatography (MEEKC). Only MEEKC offered resolution of these compounds.

An enzyme immunoassay for the quantification of plasma and intracellular lopinavir in HIV-infected patients

The protease inhibitor lopinavir (LPV; [1S-[1R*(R*), 3R*,4R*]]-N-[4-[[(2,6-dimethylphenoxy)-acetyl]amino]-3-hydroxy-5-phenyl-1-(phenylmethyl) pentyl] tetrahydro-alpha-(1-methylethyl)-2-oxo-1(2H)-pyrimide acetamide) is widely used in anti-human immunodeficiency virus (HIV) therapy. Knowledge of the plasma and intracellular concentrations of the drug would be useful for a better understanding of LPV action and for therapeutic monitoring. The aim of this study was to develop a sensitive and specific immunoassay for LPV in plasma and cells. Anti-LPV polyclonal antibodies were raised in rabbits using a synthetic LPV derivative coupled to keyhole limpet hemocyanin (KLH) as immunogen. The enzyme tracer was prepared by chemically coupling the LPV derivative with acetylcholinesterase. These reagents were used to develop a competitive enzyme immunoassay (EIA) performed in microtitration plates. The assay was performed on a minimum of 50 microl of plasma or 2 x 10(6) cells. It showed good precision and efficiency in as much as recovery from human plasma and cell extracts spiked with LPV ranged between 87% and 104%, with coefficients of variation of less than 10%. The limit of detection (LOD) was 100 pg/ml, i.e., a value at least 10 times lower than those currently achieved using previously described techniques. Cross-validation with high-performance liquid chromatography (HPLC) revealed a good correlation between methods (r2=0.96). Intracellular concentrations of LPV were measured in cultured human T lymphoblastoid cells (CEM). A pharmacokinetic analysis of plasma and intracellular LPV was performed on a healthy volunteer, and measurements were done in patients infected with HIV. The results obtained indicated a high intracellular/extracellular concentration ratio in cultured cells (19.3) but not in cells from HIV patients (1.3). In contrast, in peripheral blood mononuclear cells (PBMC) the accumulation of ritonavir (RTV) was six times higher than LPV. To date, this is the first reported immunoassay for LPV, and this method is sensitive enough for monitoring plasma and intracellular LPV levels in HIV-infected patients and for intracellular studies.

Lysine sulfonamides as novel HIV-protease inhibitors: Nε-disubstituted ureas

A series of lysine sulfonamide analogues bearing a Nepsilon-benzylic ureas was synthesized using both solution-phase and solid-phase approaches. A novel synthetic route of Nalpha-(alkyl)-Nalpha-(sulfonamides)lysinol using alpha-amino-caprolactam was developed. Evaluation of these novel protease inhibitors revealed compounds with high potency against wild-type HIV virus.

Lysine sulfonamides as novel HIV-Protease inhibitors: optimization of the Nε -acyl-phenyl spacer

A series of Nalpha-isobutyl-Nalpha-arylsulfonamido-(Nepsilon acyl) lysine and lysinol derivatives were prepared and evaluated as inhibitors of HIV protease and wild type virus. A simple original synthesis was devised to form Nalpha-(arylsulfonamide)-Nalpha-isobutyl lysine, which could be easily acylated with carboxylic acids at the Nepsilon position. A two-atom spacer was found to be optimal between this acyl group and a phenyl yielding compounds of sub-nanomolar potency on purified enzyme.

Human immunodeficiency virus type 1 capsid protein is a substrate of the retroviral proteinase while integrase is resistant toward proteolysis

The capsid protein of human immunodeficiency virus type 1 was observed to undergo proteolytic cleavage in vitro when viral lysate was incubated in the presence of dithiothreitol at acidic pH. Purified HIV-1 capsid protein was also found to be a substrate of the viral proteinase in a pH-dependent manner; acidic pH (<7) was necessary for cleavage, and decreasing the pH toward 4 increased the degree of processing. Based on N-terminal sequencing of the cleavage products, the capsid protein was found to be cleaved at two sites, between residues 77 and 78 as well as between residues 189 and 190. Oligopeptides representing these cleavage sites were also cleaved at the expected peptide bonds. The presence of cyclophilin A decreased the degree of capsid protein processing. Unlike the capsid protein, integrase was found to be resistant toward proteolysis in good agreement with its presence in the preintegration complex.

Rapid quantification of HIV protease inhibitors in human plasma by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry

HIV protease inhibitors are important antiretroviral drugs which have substantially reduced the morbidity and mortality associated with HIV-1 infection. Recent data have shown relationships between plasma concentrations of the protease inhibitors and clinical response, which makes therapeutic drug monitoring valuable. We have developed and validated an assay, using liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS), for the routine quantification of the six licensed protease inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir) and the pharmacologically active nelfinavir metabolite M8 in plasma. The sample pretreatment consisted of protein precipitation with a mixture of methanol and acetronitrile using only 100 microl of plasma. Chromatographic separation was performed on an Inertsil ODS3 column (50 x 2.0 mm i.d., particle size 5 microm), with a quick stepwise gradient using an acetate buffer (pH 5) and methanol, at a flow rate of 0.5 ml min(-1). The analytical run time was 5.5 min. The use of a 96-well plate autosampler allowed batch sizes up to 150 patient samples. The triple-quadrupole mass spectrometer was operated in the positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges 0.01-10 microg ml(-1) for indinavir and saquinavir, 0.1-10 microg ml(-1) for amprenavir, 0.05-10 microg ml(-1) for nelfinavir and ritonavir, 0.1-20 microg ml(-1) for lopinavir and 0.01-5 microg ml(-1) for M8. Saquinavir-d(5) and indinavir-d(6) were used as internal standards. The coefficients of variation were always <10% for both intra-day and inter-day precisions for each compound. Mean accuracies were also between the designated limits (+/-15%). The validated concentration ranges proved to be adequate in daily practice. This robust and fast LC/MS/MS assay is now successfully applied for routine therapeutic drug monitoring and pharmacokinetic studies in our hospital.

Results of a phase 2 clinical trial at 48 weeks (AI424-007): a dose-ranging, safety, and efficacy comparative trial of atazanavir at three doses in combination with didanosine and stavudine in antiretroviral-naive subjects

Three dose levels of the protease inhibitor (PI) atazanavir (200, 400, and 500 mg once daily) were compared with nelfinavir (750 mg three times daily) when given both as monotherapy and in combination with didanosine and stavudine in 420 antiretroviral-naive subjects infected with HIV-1. Subjects received monotherapy for 2 weeks, followed by combination therapy for 46 weeks. After 48 weeks, mean change from baseline in HIV RNA (-2.57 to -2.33 log 10 copies/mL), the proportion of subjects with HIV RNA <400 copies/mL (56%-64%) and <50 copies/mL (28%-42%), and mean increases in CD4 cell count (185-221 cells/mm 3) were comparable across treatment groups. Diarrhea was two to three times more common in the nelfinavir group (61% of subjects) than in the atazanavir groups (23%-30% of subjects, <.0001 versus nelfinavir), and jaundice occurred only in atazanavir-treated subjects (6%, 6%, and 12% in the 200-, 400-, and 500-mg groups, respectively) ( <.03 for all atazanavir regimens vs. nelfinavir). Mean percent change from baseline in fasting low-density lipoprotein (LDL) cholesterol was significantly less in the atazanavir groups (-7% to 4%) than in the nelfinavir group (31%) ( <.0001). In conclusion, once-daily atazanavir is a potent, safe, and well tolerated PI that rapidly and durably suppresses HIV RNA and durably increases CD4 cell count in antiretroviral-naive subjects. Through 48 weeks, atazanavir was not associated with clinically relevant increases in total cholesterol, fasting LDL cholesterol, or fasting triglycerides. In comparison, nelfinavir was associated with prompt, marked, and sustained elevations in these parameters of a magnitude that suggests they are clinically relevant.

The Changing Clinical Spectrum of Human Immunodeficiency Virus (HIV)-Related Oral Lesions in 1,000 Consecutive Patients: A 12-Year Study in a Referral Center in Mexico

In developing countries, the variations in the clinical spectrum of human immunodeficiency virus (HIV)-related oral lesions over time, and the possible effects of antiretroviral therapy, have not been described. In this study we evaluate the clinical spectrum of oral lesions in a series of HIV-infected patients when first examined at the acquired immunodeficiency syndrome (AIDS) clinic of a tertiary care institution in Mexico City, Mexico, and the changes observed over 12 years. All HIV-infected adult patients had an oral examination performed by specialists in oral pathology and medicine who used established clinical diagnostic criteria for oral lesions. Four periods were defined according to the evolving pattern of antiretroviral use: the first 2 were before the introduction of highly active antiretroviral therapy (HAART) and the last 2 were during more established use of HAART. For the statistical analysis the chi-square test for contingency tables and the chi-square test for trend were utilized. For dimensional variables, except age, the Kruskal-Wallis or Mann-Whitney rank sum tests were used when applicable and trend was tested with the Spearman correlation coefficient. Age was tested through analysis of variance (ANOVA) and linear regression analysis. Alpha value was set at p = 0.05 for each test. In the 12-year study, 1,000 HIV-infected patients were included (87.9% male). At the baseline examination, oral lesions strongly associated with HIV were present in 47.1% of HIV-infected patients. Oral candidosis (31.6%), hairy leukoplakia (22.6%), erythematous candidosis (21.0%), and pseudomembranous candidosis (15.8%) were the most frequent lesions. Oral Kaposi sarcoma (2.3%), HIV-associated periodontal disease (1.7%), and oral non-Hodgkin lymphoma (0.1%) were less frequent. HIV-related oral lesions decreased systematically-by half during the course of the 4 study periods (p < 0.001). Except for Kaposi sarcoma, all oral lesions strongly associated with HIV showed a trend to decrease significantly during the study period. No apparent variation in the occurrence of salivary gland disease or human papillomavirus-associated oral lesions was found. A significant trend to a lower prevalence was observed in the group of patients who were already taking antiretroviral therapy, non-HAART and HAART (p < 0.001 and p = 0.004, respectively). Only a discrete reduction, barely significant, was noted among untreated patients (p = 0.060). By Period IV (1999-2001), those who received HAART showed the lowest prevalence of oral lesions strongly associated with HIV (p < 0.001). Patients with oral lesions strongly associated with HIV had significantly lower median CD4+ counts and higher viral loads than those without oral lesions strongly associated with HIV (p < 0.001 and p = 0.005, respectively). When CD4+ counts were correlated with prevalence of oral candidosis, a consistently negative association was found; this association prevailed even after the study group was partitioned according to period. In this selected cohort of 1,000 patients with HIV infection, the clinical spectrum of HIV-related oral lesions has changed over the 12-year study, with a decreased prevalence of most oral lesions. Our findings probably represent improvements in medical care of HIV-infected persons, earlier detection of HIV-infected patients at the AIDS clinic, the increasing use of prophylactic drugs to prevent secondary AIDS-related opportunistic infections, and, perhaps most important, the availability of potent antiretroviral therapy in recent years, since the introduction of HAART.

Changes in human immunodeficiency virus type 1 Gag at positions L449 and P453 are linked to I50V protease mutants in vivo and cause reduction of sensitivity to amprenavir and improved viral fitness in vitro

Human immunodeficiency virus type 1 (HIV-1) Gag protease cleavage sites (CS) undergo sequence changes during the development of resistance to several protease inhibitors (PIs). We have analyzed the association of sequence variation at the p7/p1 and p1/p6 CS in conjunction with amprenavir (APV)-specific protease mutations following PI combination therapy with APV. Querying a central resistance data repository resulted in the detection of significant associations (P < 0.001) between the presence of APV protease signature mutations and Gag L449F (p1/p6 LP1'F) and P453L (p1/p6 PP5'L) CS changes. In population-based sequence analyses the I50V mutant was invariably linked to either L449F or P453L. Clonal analysis revealed that both CS mutations were never present in the same genome. Sequential plasma samples from one patient revealed a transition from I50V M46L P453L viruses at early time points to I50V M46I L449F viruses in later samples. Various combinations of the protease and Gag mutations were introduced into the HXB2 laboratory strain of HIV-1. In both single- and multiple-cycle assay systems and in the context of I50V, the L449F and P453L changes consistently increased the 50% inhibitory concentration of APV, while the CS changes alone had no measurable effect on inhibitor sensitivity. The decreased in vitro fitness of the I50V mutant was only partially improved by addition of either CS change (I50V M46I L449F mutant replicative capacity approximately 16% of that of wild-type virus). Western blot analysis of Pr55 Gag precursor cleavage products from infected-cell cultures indicated accumulation of uncleaved Gag p1-p6 in all I50V viruses without coexisting CS changes. Purified I50V protease catalyzed cleavage of decapeptides incorporating the L449F or P453L change 10-fold and 22-fold more efficiently than cleavage of the wild-type substrate, respectively. HIV-1 protease CS changes are selected during PI therapy and can have effects on both viral fitness and phenotypic resistance to PIs.

"In vitro" antifungal activity of protease inhibitors

In the last five years, as HAART has become standard therapy in HIV seropositive or AIDS patients, changes have been noted in the numbers and types of opportunistic fungal infections in these cohorts of patients. Particularly, oropharyngeal candidiasis have become rare in HIV infected patients since the introduction of new anti-HIV drugs of the protease inhibitors type. At the Immunology Institute of the Universidad Central de Venezuela the most frequent protease inhibitors (PIs) used for the treatment of these patients have been: Nelfinavir (Viracept, Roche), Indinavir (Crixivan Merck), Ritonavir (Norvir, Abbott), Saquinavir (Fortovase, Roche). Recently, we observed that recurrent candidiasis was less frequent and no Candida could be isolated in our patients. A direct relation to the PIs was suspected. In order to assess the "in vitro" antifungal activity of the afore mentioned protease inhibitors on Candida sp., we used both the well diffusion test and the NCCLS broth microdilution test to assay 100 Candida sp. isolates from HIV seropositive or AIDS patients with syntomatic oropharyngeal Candida infection. In general, the data obtained with the well diffusion test were in agreement with those obtained by the broth microdilution test. All 100 isolates were susceptible to Saquinavir and 32 were susceptible to Indinavir using the NCCLS microdilution test, while 97 were susceptible to Saquinavir and 52 to Indinavir by the well diffusion test. From 17 C. albicans resistant to fluconazole, all were susceptible to Saquinavir by the NCCLS micromethod and 16 by the well diffusion test. Our results showed anticandidal activity "in vitro" of PIs, mainly Saquinavir.

High-performance liquid chromatography of HIV protease inhibitors in human biological matrices

Methods for HPLC analysis of protease inhibitors (PIs) in human biological matrices were reviewed. Assays have been developed for analysis of single PIs or for simultaneous measurement of multiple PIs in plasma-serum, saliva, cerebrospinal fluid and semen. Liquid-liquid extraction was most often applied for sample pretreatment, but solid-phase extraction and protein precipitation were used as well. Reversed-phase or ion-pair chromatography have been used to separate PIs. Detection of PIs should be sensitive enough for quantitation of plasma concentrations below trough levels of single PIs, or below proposed therapeutic thresholds for PIs. The large majority of assays employs UV detection. As the potential for interferences is large, the selectivity of every method should be evaluated properly. The available high-performance liquid chromatography (HPLC) methods have been applied in clinical pharmacokinetic studies and for therapeutic drug monitoring of PIs. Participation in an interlaboratory quality control program is recommended for every laboratory engaged in the bioanalysis of PIs.

P-Glycoprotein and transporter MRP1 reduce HIV protease inhibitor uptake in CD4 cells: potential for accelerated viral drug resistance?

BACKGROUND

The multidrug transporters P-glycoprotein (P-gp) and MRP1 are functionally expressed in several subclasses of lymphocytes. HIV-1 protease inhibitors interact with both; consequently the transporters could reduce the local concentration of HIV-1 protease inhibitors and, thus, influence the selection of viral mutants.

OBJECTIVES

To study the effect of the expression of P-gp and MRP1 on the transport and accumulation of HIV-1 protease inhibitors in human lymphocytes and to study the effects of specific P-gp and MRP1 inhibitors.

METHODS

The initial rate and the steady-state intracellular accumulation of radiolabelled ritonavir, indinavir, saquinavir and nelfinavir was measured in three human lymphocyte cell lines: control CEM cells, CEM-MDR cells, which express 30-fold more P-gp than CEM cells, and CEM-MRP cells, which express fivefold more MRP1 protein than CEM cells. The effect of specific inhibitors of P-gp (GF 120918) and MRP1 (MK 571) was also examined.

RESULTS

Compared with CEM cells, the initial rates of uptake and the steady-state intracellular concentrations of all protease inhibitors are significantly reduced in CEM-MDR cells. The intracellular concentrations of the protease inhibitors are increased upon co-administration with GF 120918, in some cases to levels approaching those in CEM cells. The intracellular concentrations of the protease inhibitors are also significantly reduced in CEM-MRP cells. Co-administration with MK -571 can partially overcome these effects.

CONCLUSIONS

The overexpression of multidrug transporters significantly reduces the accumulation of protease inhibitors at this major site of virus replication, which, potentially, could accelerate the acquisition of viral resistance. Targeted inhibition of P-gp may represent an important strategy by which this problem can be overcome.