Class Of Antiretroviral Agents Research Articles

Preclinical characterization of a non-peptidomimetic HIV protease inhibitor with improved metabolic stability.

Protease inhibitors (PIs) remain an important component of antiretroviral therapy for the treatment of HIV-1 infection due to their high genetic barrier to resistance development. Nevertheless, the two most commonly prescribed HIV PIs, atazanavir and darunavir, still require co-administration with a pharmacokinetic boosting agent to maintain sufficient drug plasma levels which can lead to undesirable drug-drug interactions. Herein, we describe GS-9770, a novel investigational non-peptidomimetic HIV PI with unboosted once-daily oral dosing potential due to improvements in its metabolic stability and its pharmacokinetic properties in preclinical animal species. This compound demonstrates potent inhibitory activity and high on-target selectivity for recombinant HIV-1 protease versus other aspartic proteases tested. In cell culture, GS-9770 inhibits Gag polyprotein cleavage and shows nanomolar anti-HIV-1 potency in primary human cells permissive to HIV-1 infection and against a broad range of HIV subtypes. GS-9770 demonstrates an improved resistance profile against a panel of patient-derived HIV-1 isolates with resistance to atazanavir and darunavir. In resistance selection experiments, GS-9770 prevented the emergence of breakthrough HIV-1 variants at all fixed drug concentrations tested and required multiple protease substitutions to enable outgrowth of virus exposed to escalating concentrations of GS-9770. This compound also remained fully active against viruses resistant to drugs from other antiviral classes and showed no in vitro antagonism when combined pairwise with drugs from other antiretroviral classes. Collectively, these preclinical data identify GS-9770 as a potent, non-peptidomimetic once-daily oral HIV PI with potential to overcome the persistent requirement for pharmacological boosting with this class of antiretroviral agents.

The discovery and design of novel HIV-1 capsid modulators and future perspectives

ABSTRACT Introduction Although combination antiretroviral therapy (cART) has achieved significant success in treating HIV, the emergence of multidrug-resistant viruses and cumulative medication toxicity make it necessary to find new classes of antiretroviral agents with novel mechanisms of action. With high sequence conservation, the HIV-1 capsid (CA) protein has attracted attention as a prospective therapeutic target due to its crucial structural and regulatory functions in the HIV-1 replication cycle. Area covered Herein, the authors provide a cutting-edge overview of current advances in the design and discovery of CA modulators, PF74, GS-6207 and their derivativeswhich targets a therapeutically attractive NTD-CTD interprotomer pocket within the hexameric configuration of HIV-1 CA. The discovery and development of these compounds, and derivatives thereof, have provided valuable information for the design of second-generation CA-targeting antivirals. Expert opinion Despite some successes in designing and discovering HIV-1 CA modulators, more studies are required to decipher which chemical groups confer specific desirable properties. The future of CA-modulating compounds may lie in covalent inhibition and the creation of proteolysis-targeting chimeras (PROTACs). Moreover, biological interrogation of the process of CA uncoating, virus–host interactions, and studies on the lattice-binding restriction factors may improve our knowledge of HIV-1 CA and support the design of new antiviral agents.

An Overview of Antiretroviral Agents for Treating HIV Infection in Paediatric Population.

Paediatric Acquired ImmunoDeficiency Syndrome (AIDS) is a life-threatening and infectious disease in which the Human Immunodeficiency Virus (HIV) is mainly transmitted through Mother-To- Child Transmission (MTCT) during pregnancy, labour and delivery, or breastfeeding. This review provides an overview of the distinct therapeutic alternatives to abolish the systemic viral replication in paediatric HIV-1 infection. Numerous classes of antiretroviral agents have emerged as therapeutic tools for downregulation of different steps in the HIV replication process. These classes encompass Non- Nucleoside Analogue Reverse Transcriptase Inhibitors (NNRTIs), Nucleoside/Nucleotide Analogue Reverse Transcriptase Inhibitors (NRTIs/NtRTIs), INtegrase Inhibitors (INIs), Protease Inhibitors (PIs), and Entry Inhibitors (EIs). Co-administration of certain antiretroviral drugs with Pharmacokinetic Enhancers (PEs) may boost the effectiveness of the primary therapeutic agent. The combination of multiple antiretroviral drug regimens (Highly Active AntiRetroviral Therapy - HAART) is currently the standard therapeutic approach for HIV infection. So far, the use of HAART offers the best opportunity for prolonged and maximal viral suppression, and preservation of the immune system upon HIV infection. Still, the frequent administration of high doses of multiple drugs, their inefficient ability to reach the viral reservoirs in adequate doses, the development of drug resistance, and the lack of patient compliance compromise the complete HIV elimination. The development of nanotechnology-based drug delivery systems may enable targeted delivery of antiretroviral agents to inaccessible viral reservoir sites at therapeutic concentrations. In addition, the application of Computer-Aided Drug Design (CADD) approaches has provided valuable tools for the development of anti-HIV drug candidates with favourable pharmacodynamics and pharmacokinetic properties.

HIV-1 integrase tetramers are the antiviral target of pyridine-based allosteric integrase inhibitors.

Allosteric HIV-1 integrase (IN) inhibitors (ALLINIs) are a promising new class of antiretroviral agents that disrupt proper viral maturation by inducing hyper-multimerization of IN. Here we show that lead pyridine-based ALLINI KF116 exhibits striking selectivity for IN tetramers versus lower order protein oligomers. IN structural features that are essential for its functional tetramerization and HIV-1 replication are also critically important for KF116 mediated higher-order IN multimerization. Live cell imaging of single viral particles revealed that KF116 treatment during virion production compromises the tight association of IN with capsid cores during subsequent infection of target cells. We have synthesized the highly active (-)-KF116 enantiomer, which displayed EC50 of ~7 nM against wild type HIV-1 and ~10 fold higher, sub-nM activity against a clinically relevant dolutegravir resistant mutant virus suggesting potential clinical benefits for complementing dolutegravir therapy with pyridine-based ALLINIs.

Recent Advances in Antiretroviral Agents: Potent Integrase Inhibitors.

Integrase strand transfer inhibitors (INSTIs) belong to a novel class of antiretroviral agents that have emerged as the new first-line treatments. Three such compounds are currently available, raltegravir, elvitegravir, dolutegravir and two more under development, bictegravir and cabotegravir. These compounds share the same mode of action but exhibit different pharmacokinetic/ pharmacodynamic properties, and drug-drug interactions. A series of studies in the past decade have established their efficacy compared to previous regimens, both in treatment- naïve and experienced patients. INSTIs have demonstrated a favorable safety profile with fewer adverse events and low rates of virological failure. Emergence of resistance to these agents, however, is a worrying concern, particularly for elvitegravir and raltegravir that display a lower genetic barrier than dolutegravir. On-going trials aim at establishing INSTIs as part of dual-drug HIV treatments or even monotherapy. New long-acting, injectable formulations are under investigation for treatment or prevention.

Clinical management of dyslipidaemia associated with combination antiretroviral therapy in HIV-infected patients.

The introduction of potent combination antiretroviral therapy (cART) has had a remarkable impact on the natural history of HIV infection, leading to a dramatic decline in the mortality rate and a considerable increase in the life expectancy of HIV-positive people. However, cART use is frequently associated with several metabolic complications, mostly represented by lipid metabolism alterations, which are reported very frequently among persons treated with antiretroviral agents. In particular, hyperlipidaemia occurs in up to 70%-80% of HIV-positive subjects receiving cART and is mainly associated with specific antiretroviral drugs belonging to three classes of antiretroviral agents: NRTIs, NNRTIs and PIs. The potential long-term consequences of cART-associated dyslipidaemia are not completely understood, but an increased risk of premature coronary heart disease has been reported in HIV-infected patients on cART, so prompt correction of lipid metabolism abnormalities is mandatory in this population. Dietary changes, regular aerobic exercise and switching to a different antiretroviral regimen associated with a more favourable metabolic profile are the first steps in clinical management, but lipid-lowering therapy with fibrates or statins is often required. In this case, the choice of hypolipidaemic drugs should take into account the potential pharmacokinetic interactions with many antiretroviral agents.

HIV pharmacotherapy: A review of integrase inhibitors.

Integrase strand transfer inhibitors (INSTIs) are a class of antiretroviral agents used to treat HIV. These drugs--raltegravir, elvitegravir, and dolutegravir--are preferred options for treatment-naïve patients when used in combination with two nucleoside reverse transcriptase inhibitors. Based on clinical trials, INSTIs have been proven to be effective with minimal safety concerns. This article reviews the pharmacologic profile, role in therapy, and safety and efficacy of each agent.

Recent Advances in the Development of Small-Molecular Inhibitors Target HIV Integrase-LEDGF/p75 Interaction.

Lens epithelium-derived growth factor (LEDGF/p75) plays an essential role in the HIV-1 replication. It acts by tethering integrase (IN) into the host cellular chromatin. Due to its significance of the IN-LEDGF/p75 interaction affords a novel therapeutic approach for the design of new classes of antiretroviral agents. To date, many small molecules have been found to be the inhibitors of INLEDGF/ p75 interaction. This review summarizes recent advances in the development of potential structure-based IN-LEDGF/p75 interaction inhibitors. The work will be helpful to shed light on the antiretroviral drug development pipeline in the next future.

Transmitted drug resistance of HIV-1 strains among individuals attending voluntary counselling and testing in Taiwan.

Genotypic drug resistance testing for HIV-1 has been integrated into voluntary counselling and testing (VCT) programmes to investigate the trends of transmitted drug resistance (TDR), including integrase mutations, among individuals with recent or chronic HIV infections in Taiwan. Between 2006 and 2014, 745 of 21 886 subjects (3.4%) tested HIV positive in the VCT service. The BED assay was used to identify recent HIV infections. Genotypic resistance mutations were interpreted using the WHO 2009 list. Integrase resistance mutations were analysed using the Stanford HIV Drug Resistance Database. Three-hundred-and-sixty (48.3%) patients were recently infected with HIV-1. Of 440 patients linked to HIV care with analysable reverse transcriptase and protease genes, 49 (11.1%) were infected with HIV-1 harbouring at least one resistance-associated mutation (RAM). The prevalence of TDR to NRTIs, NNRTIs and PIs was 4.1%, 6.4% and 2.3%, respectively. TDR prevalence did not change significantly during the study period. CD4 counts ≤500 cells/mm(3) and hepatitis B surface antigen positivity were independent factors associated with acquiring drug-resistant HIV. The prevalence of integrase mutations was 3.2%. Among the seven major integrase mutations (T66I, E92Q, G140S, Y143C/H/R, S147G, Q148H/K/R and N155H), only one strain harbouring the Q148R mutation was detected. We found no statistically significant difference between patients with chronic infection and those with recent infection in the prevalence of drug-resistant mutations to any of the four classes of antiretroviral agents. The prevalence of TDR of HIV-1 strains to available antiretroviral agents is moderately high, but transmission of HIV-1 with drug-resistant mutations remains stable in Taiwan.

Natural polymorphism S119R of HIV-1 integrase enhances primary INSTI resistance

Integrase strand transfer inhibitors (INSTIs), which block proviral DNA integration into the host chromosome, are clinically effective against HIV-1 isolates exhibiting resistance to other classes of antiretroviral agents. Although naturally occurring amino acid variation has been less frequently observed in the integrase region, the functional constraints of this variation on primary INSTI resistance-associated mutations are not fully understood.In the present study, we focused on the S119G/R/P/T (S119X) polymorphisms, which are frequently observed in HIV-1 sequences derived from clinical specimens (naïve, n=458, 26%). The frequency of the S119X polymorphism together with Q148H/R (n=8, 63%) or N155H (n=12, 83%) was relatively high compared with that of naïve group. Our in vitro assays revealed that S119G/P/T alone exerted no effect on the susceptibility to INSTIs, whereas S119R enhanced the level of INSTI resistance induced by well-known INSTI resistance-associated mutations (Y143C, Q148H or N155H). Notably, the S119R polymorphism contributed to a significant (5.9-fold) increase in dolutegravir resistance caused by G140S/Q148H. Analysis of two cases of virological failure during raltegravir-based therapy showed that the accumulation and the rapid evolution of primary INSTI resistance-associated mutations coincided with the S119R mutation. These data highlight the role of the S119X polymorphism in INSTI resistance, and this polymorphism might be linked to the potential treatment outcome with INSTI-based therapy.

Structure-activity relationships of a novel capsid targeted inhibitor of HIV-1 replication.

Despite the considerable successes of highly active antiretroviral therapy (HAART) for the treatment of HIV/AIDS, cumulative drug toxicities and the development of multidrug-resistant virus necessitate the search for new classes of antiretroviral agents with novel modes of action. The HIV-1 capsid (CA) protein has been structurally and functionally characterized as a druggable target. We have recently designed a novel small molecule inhibitor I-XW-053 using the hybrid structure based method to block the interface between CA N-terminal domains (NTD–NTD interface) with micromolar affinity. In an effort to optimize and improve the efficacy of I-XW-053, we have developed the structure activity relationship of I-XW-053 compound series using ligand efficiency methods. Fifty-six analogues of I-XW-053 were designed that could be subclassified into four different core domains based on their ligand efficiency values computed as the ratio of binding efficiency (BEI) and surface efficiency (SEI) indices. Compound 34 belonging to subcore-3 showed an 11-fold improvement over I-XW-053 in blocking HIV-1 replication in primary human peripheral blood mononuclear cells (PBMCs). Surface plasmon resonance experiments confirmed the binding of compound 34 to purified HIV-1 CA protein. Molecular docking studies on compound 34 and I-XW-053 to HIV-1 CA protein suggested that they both bind to NTD–NTD interface region but with different binding modes, which was further validated using site-directed mutagenesis studies.

Coreceptor tropism determined by genotypic assay in HIV‐1 circulating in Thailand, where CRF01_AE predominates

Chemokine (C-C motif) receptor 5 (CCR5) inhibitors are a novel class of antiretroviral agents that are promising for treatment of patients who harbour the HIV-1 R5 strain. Data on coreceptor tropism in non-B HIV-1 subtypes are limited. We studied coreceptor tropism in HIV-1 circulating in Thailand, where CRF01_AE predominates, using a genotypic assay. We compiled V3 sequences of HIV-1 strains circulating in Thailand during 2010-2012. Coreceptor tropism was predicted based on V3 sequences using geno2pheno version 2.5 (http://coreceptor.bioinf.mpi-inf.mpg.de). One hundred and fifty-five HIV-1-infected patients were enrolled in this study. Ninety-nine patients (63.9%) were antiretroviral-naïve, and the remainder had virological failure. The median (interquartile range) CD4 cell count and HIV-1 RNA were 220 (74-379) cells/μL and 75,374 (14,127-226,686) HIV-1 RNA copies/mL, respectively. Of the sequences obtained from these patients, 119 (76.8%) were CRF01_AE and 22 (14.2%) were subtype B. At a false positive rate of < 5%, 61 (39.4%) HIV-1-infected individuals were predicted to harbour the X4 phenotype. X4 viruses were detected more frequently in the treatment-failure group compared with the treatment-naïve group (30.3 vs. 55.4%, respectively; P = 0.002). Those with CRF01_AE had a higher proportion of X4 viruses compared with non-AE subtypes (47.9 vs. 11.1%, respectively; P < 0.001). By multivariate logistic regression, CRF01_AE and treatment failure were independently associated with predicted X4 phenotype [odds ratio (OR) 7.93; 95% confidence interval (CI) 2.57-24.50; P < 0.001, and OR 3.10; 95% CI 1.50-6.42; P = 0.002, respectively]. CRF01_AE and treatment failure are associated with the predicted X4 phenotype. In regions where CRF01_AE predominates, use of CCR5 inhibitors must be considered with caution. The phenotypic assay and its correlation with genotypes should be further investigated in CRF01_AE.

A review of pharmacological interactions between HIV or hepatitis C virus medications and opioid agonist therapy: implications and management for clinical practice

Global access to opioid agonist therapy and HIV/hepatitis C virus (HCV) treatment is expanding but when used concurrently, problematic pharmacokinetic and pharmacodynamic interactions may occur. Articles published from 1966 to 2012 in Medline were reviewed using the following keywords: HIV, AIDS, HIV therapy, HCV, HCV therapy, antiretroviral therapy, highly active antiretroviral therapy, drug interactions, methadone and buprenorphine. In addition, a review of abstracts from national and international meetings and conference proceedings was conducted; selected reports were reviewed as well. The metabolism of both opioid and antiretroviral therapies, description of their known interactions and clinical implications and management of these interactions were reviewed. Important pharmacokinetic and pharmacodynamic drug interactions affecting either methadone or HIV medications have been demonstrated within each class of antiretroviral agents. Drug interactions between methadone, buprenorphine and HIV medications are known and may have important clinical consequences. Clinicians must be alert to these interactions and have a basic knowledge regarding their management.

HIV DRUG resistance genotyping – an Australian perspective of its role and utilisation in contemporary HIV practice

Resistance to individual drugs within combination antiretroviral therapies (cART) regimens has been a growing international problem. HIV drug-resistance genotyping has been widely, but not universally, available in Australia for over a decade, initially through state funded reference laboratories, and more recently since 2011 by Medicare through the Pathology Services Table. An assessment by the Medical Services Advisory Committee (MSAC) found both in-house and commercial kit testing to be cost effective in a complex modelling of outcomes. Currently standard resistance genotyping provides a predicted resistance profile for three classes of antiretroviral agents. Individual state-based service data show moderate prevalence of primary resistance to at least one antiretroviral agent from the three main classes of NRTI, NNRTI and PI. Non RTI and non-PI therapies are increasingly being used with little evidence of primary resistance. Laboratories will need to develop a broader repertoire of gene sequencing capability to accommodate the clinical need in those exposed to these newer drugs. CCR5 blockers require pre-use tropism testing of an individual’s virus. The early reported experience of laboratories performing tropism genotyping from integrated proviral DNA sequences in virally suppressed patients highlights the need for caution in interpreting tropism in the setting of viral suppression.

Three Main Mutational Pathways in HIV-2 Lead to High-Level Raltegravir and Elvitegravir Resistance: Implications for Emerging HIV-2 Treatment Regimens

Human immunodeficiency virus type 2 (HIV-2) is intrinsically resistant to non-nucleoside reverse transcriptase inhibitors and exhibits reduced susceptibility to several of the protease inhibitors used for antiretroviral therapy of HIV-1. Thus, there is a pressing need to identify new classes of antiretroviral agents that are active against HIV-2. Although recent data suggest that the integrase strand transfer inhibitors raltegravir and elvitegravir may be beneficial, mutations that are known to confer resistance to these drugs in HIV-1 have been reported in HIV-2 sequences from patients receiving raltegravir-containing regimens. To examine the phenotypic effects of mutations that emerge during raltegravir treatment, we constructed a panel of HIV-2 integrase variants using site-directed mutagenesis and measured the susceptibilities of the mutant strains to raltegravir and elvitegravir in culture. The effects of single and multiple amino acid changes on HIV-2 replication capacity were also evaluated. Our results demonstrate that secondary replacements in the integrase protein play key roles in the development of integrase inhibitor resistance in HIV-2. Collectively, our data define three major mutational pathways to high-level raltegravir and elvitegravir resistance: i) E92Q+Y143C or T97A+Y143C, ii) G140S+Q148R, and iii) E92Q+N155H. These findings preclude the sequential use of raltegravir and elvitegravir (or vice versa) for HIV-2 treatment and provide important information for clinical monitoring of integrase inhibitor resistance in HIV-2–infected individuals.

Short-Course Raltegravir Intensification Does Not Increase 2 Long Terminal Repeat Episomal HIV-1 DNA in Patients on Effective Antiretroviral Therapy

TO THE EDITOR—Controversy exists about whether human immunodeficiency virus type 1 (HIV-1) replication persists in patients receiving effective antiretroviral therapy. Residual viremia can often be detected in such patients by sensitive quantitative polymerase chain reaction assays, but the source of this viremia is unknown [1]. Possibilities include ongoing cycles of HIV-1 replication, long-lived HIV-1–infected cells that continuously or intermittently produce virus, or both. If residual plasma viremia is derived from ongoing HIV-1 replication, intensification of an effective regimen with another potent antiretroviral drug should lower viremia. Such treatment intensification studies have been conducted with different classes of antiretroviral agents (nucleoside reverse-transcriptase inhibitors, nonnucleoside reverse-transcriptase inhibitors, protease inhibitors, and the integrase inhibitor raltegravir), and none has shown reduction in residual viremia [2–6]. However, Buzon et al [7] showed transient increases in episomal (2-Long Terminal Repeat [2-LTR] circle) HIV-1 DNA levels in 13 of 45 patients after raltegravir intensification, suggesting raltegravir blocked ongoing HIV-1 replication without affecting plasma viremia. Moreover, Yukl et al [5] showed reductions in unspliced HIV-1 RNA levels in CD4+ T cells from the terminal ileum in 5 of 7 patients after raltegravir intensification. To provide additional insight into the effects of raltegravir intensification, we analyzed total HIV-1 DNA and 2-LTR circle levels in peripheral blood mononuclear cells (PBMCs) obtained before and after 28 days of raltegravir intensification from a study of 10 patients, published by McMahon et al [4] in Clinical Infectious Diseases, that showed no effect of raltegravir on residual viremia. Total cellular DNA was extracted (Dynabeads) from 5 × 106 PBMCs and assayed for total HIV-1 DNA and 2-LTR HIV-1 DNA circle levels by quantitative, real-time polymerase chain reaction (limit of detection, 15 copies per 106 PBMCs for both assays). HIV-1 DNA was detected in all subjects, ranging from 154 to 6,879 copies per 106 PBMCs and showing no consistent change between baseline (before intensification) and 28 days after intensification (Table 1). Levels of 2-LTR circles were detected in 3 of 10 patients at baseline, but only 2 still tested positive after intensification (range, 19–638 copies per 106 PBMCs). There was no increase in 2-LTR circles in these 2 patients after raltegravir intensification. There was also no change in the ratio of 2-LTR circles to total HIV-1 DNA level after intensification. Finally, none of the 7 patients who were negative for 2-LTR circles at baseline become positive after intensification. Table 1. Quantification of HIV-1 DNA and 2 Long Terminal Repeat Circles in Peripheral Blood Mononuclear Cells These results do not support an effect of raltegravir intensification on 2-LTR HIV-1 DNA circles, which is contrary to the report by Buzon et al [7] that showed an increase in 2-LTR circles in 29% of patients 2–4 weeks after raltegravir intensification. Differences in patient characteristics, sampling time, antiretroviral regimens, duration of HIV-1 RNA suppression, and sample size may be responsible for the discrepancies between the 2 studies. Nevertheless, most evidence reported to date, including the results presented here, refute ongoing HIV-1 replication in patients receiving effective antiretroviral therapy as the source of residual viremia [2, 5, 6]. Additional studies are needed, however, to assess the impact of treatment intensification on HIV-1 replication in tissue compartments.

Development of Cell-type specific anti-HIV gp120 aptamers for siRNA delivery

The global epidemic of infection by HIV has created an urgent need for new classes of antiretroviral agents. The potent ability of small interfering (si)RNAs to inhibit the expression of complementary RNA transcripts is being exploited as a new class of therapeutics for a variety of diseases including HIV. Many previous reports have shown that novel RNAi-based anti-HIV/AIDS therapeutic strategies have considerable promise; however, a key obstacle to the successful therapeutic application and clinical translation of siRNAs is efficient delivery. Particularly, considering the safety and efficacy of RNAi-based therapeutics, it is highly desirable to develop a targeted intracellular siRNA delivery approach to specific cell populations or tissues. The HIV-1 gp120 protein, a glycoprotein envelope on the surface of HIV-1, plays an important role in viral entry into CD4 cells. The interaction of gp120 and CD4 that triggers HIV-1 entry and initiates cell fusion has been validated as a clinically relevant anti-viral strategy for drug discovery. Herein, we firstly discuss the selection and identification of 2'-F modified anti-HIV gp120 RNA aptamers. Using a conventional nitrocellulose filter SELEX method, several new aptamers with nanomolar affinity were isolated from a 50 random nt RNA library. In order to successfully obtain bound species with higher affinity, the selection stringency is carefully controlled by adjusting the conditions. The selected aptamers can specifically bind and be rapidly internalized into cells expressing the HIV-1 envelope protein. Additionally, the aptamers alone can neutralize HIV-1 infectivity. Based upon the best aptamer A-1, we also create a novel dual inhibitory function anti-gp120 aptamer-siRNA chimera in which both the aptamer and the siRNA portions have potent anti-HIV activities. Further, we utilize the gp120 aptamer-siRNA chimeras for cell-type specific delivery of the siRNA into HIV-1 infected cells. This dual function chimera shows considerable potential for combining various nucleic acid therapeutic agents (aptamer and siRNA) in suppressing HIV-1 infection, making the aptamer-siRNA chimeras attractive therapeutic candidates for patients failing highly active antiretroviral therapy (HAART).

Development of Cell-type specific anti-HIV gp120 aptamers for siRNA delivery

The global epidemic of infection by HIV has created an urgent need for new classes of antiretroviral agents. The potent ability of small interfering (si)RNAs to inhibit the expression of complementary RNA transcripts is being exploited as a new class of therapeutics for a variety of diseases including HIV. Many previous reports have shown that novel RNAi-based anti-HIV/AIDS therapeutic strategies have considerable promise; however, a key obstacle to the successful therapeutic application and clinical translation of siRNAs is efficient delivery. Particularly, considering the safety and efficacy of RNAi-based therapeutics, it is highly desirable to develop a targeted intracellular siRNA delivery approach to specific cell populations or tissues. The HIV-1 gp120 protein, a glycoprotein envelope on the surface of HIV-1, plays an important role in viral entry into CD4 cells. The interaction of gp120 and CD4 that triggers HIV-1 entry and initiates cell fusion has been validated as a clinically relevant anti-viral strategy for drug discovery. Herein, we firstly discuss the selection and identification of 2'-F modified anti-HIV gp120 RNA aptamers. Using a conventional nitrocellulose filter SELEX method, several new aptamers with nanomolar affinity were isolated from a 50 random nt RNA library. In order to successfully obtain bound species with higher affinity, the selection stringency is carefully controlled by adjusting the conditions. The selected aptamers can specifically bind and be rapidly internalized into cells expressing the HIV-1 envelope protein. Additionally, the aptamers alone can neutralize HIV-1 infectivity. Based upon the best aptamer A-1, we also create a novel dual inhibitory function anti-gp120 aptamer-siRNA chimera in which both the aptamer and the siRNA portions have potent anti-HIV activities. Further, we utilize the gp120 aptamer-siRNA chimeras for cell-type specific delivery of the siRNA into HIV-1 infected cells. This dual function chimera shows considerable potential for combining various nucleic acid therapeutic agents (aptamer and siRNA) in suppressing HIV-1 infection, making the aptamer-siRNA chimeras attractive therapeutic candidates for patients failing highly active antiretroviral therapy (HAART).

The "Connection" Between HIV Drug Resistance and RNase H.

Currently, nucleoside reverse transcriptase inhibitors (NRTIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs) are two classes of antiretroviral agents that are approved for treatment of HIV-1 infection. Since both NRTIs and NNRTIs target the polymerase (pol) domain of reverse transcriptase (RT), most genotypic analysis for drug resistance is limited to the first ∼300 amino acids of RT. However, recent studies have demonstrated that mutations in the C-terminal domain of RT, specifically the connection subdomain and RNase H domain, can also increase resistance to both NRTIs and NNRTIs. In this review we will present the potential mechanisms by which mutations in the C-terminal domain of RT influence NRTI and NNRTI susceptibility, summarize the prevalence of the mutations in these regions of RT identified to date, and discuss their importance to clinical drug resistance.

Pharmacokinetics of Rifampicin during Antiretroviral Treatment with Non-Nucleoside Reverse Transcriptase Inhibitors

Introduction: Co-management of tuberculosis (TB) and HIV is complicated by pharmacologic drug interactions between rifampicin (RMP) and certain classes of antiretroviral agents. The NNRTIs Nevirapine (NVP) or Efavirenz (EFV), used to HIV infection, are known to induce the CYP 450 enzyme system. Thus when RMP is co-administered along with NVP or EFV, the bioavailability of RMP could be lowered leading to drug resistance and treatment failure. Objectives: To study the steady state pharmacokinetics of RMP in HIV and HIV-TB patients receiving antiretroviral regimens containing NVP or EFV respectively. Methods: The study population comprised of HIV and HIV-TB patients undergoing antiretroviral treatment with NVP and EFV containing regimens respectively. These patients were also receiving concomitant RMP. Rifampicin was estimated by HPLC in blood collected at different time points after drug administration. The pharmacokinetic variables of RMP were calculated using WinNonlin software. Results &amp; Conclusions: Co-administration of NVP or EFV did not alter the pharmacokinetics of RMP in HIV and HIV-TB patients, suggesting that the dose of RMP need not be altered during antiretroviral treatment with NVP or EFV. Key words: Rifampicin; nevirapine; efavirenz; drug-drug interactions; HIV-TB DOI: 10.3126/saarctb.v5i2.3068 SAARC J. Tuber. Lung Dis. HIV/AIDS 2008 Vol.5(2) 1-5