Protease Inhibitor Drugs Research Articles

Kinetic and thermodynamic characterisation of HIV-protease inhibitors against E35D↑G↑S mutant in the South African HIV-1 subtype C protease

Herein, we report the effect of nine FDA approved protease inhibitor drugs against a new HIV-1 subtype C mutant protease, E35D↑G↑S. The mutant has five mutations, E35D, two insertions, position 36 (G and S), and D60E. Kinetics, inhibition constants, vitality, Gibbs free binding energies are reported. The variant showed a decreased affinity for substrate and low catalytic efficiency compared to the wild type. There was a significant decrease in the binding of seven FDA approved protease inhibitors against the mutant (p < .0001). Amprenavir and ritonavir showed the least decrease, but still significant reduced activity in comparison to the wildtype (4 and 5 folds, respectively, p = .0021 and .003, respectively). Nelfinavir and atazanavir were the worst inhibitors against the variant as seen from the IC50, with values of 1401 ± 3.0 and 685 ± 3.0 nM, respectively. Thermodynamics data showed less favourable Gibbs free binding energies for the protease inhibitors to the mutant.

HIV-1 Drug Resistance Mutations among Antiretroviral Drug-Experienced Patients in the South of Iran

Background: The therapeutic effect of antiretroviral therapy (ART) is adversely influenced by antiretroviral drug resistance, mainly due to mutations (DRMs) in the human immunodeficiency virus (HIV) genome. These mutations are commonly associated with HIV protease and reverse-transcriptase genes. We sought to determine the frequency of DRMs in a population of ART-experienced patients in the South of Iran. Method: A total of 44 HIV-1-positive participants under ART were selected from April 2016 to March 2017. Their DRMs, antiretroviral resistance status, and viral subtypes were determined. Results: At least one DRM was detected in 61.4% of the participants. The highest frequency was related to nucleotide reverse-transcriptase inhibitor (NRTI) mutations (45.45%). In contrast, major protease inhibitor (PI) mutations had the lowest frequency (6.81%). M184V (40.9%) and K103N (25%), respectively related to NRTI and nonnucleoside reverse-transcriptase inhibitor (NNRTI), were the mutations with the highest frequencies. Susceptibility to PI drugs was higher compared to NRTIs and NNRTIs, which was consistent with the results of genotypic DRMs. Conclusion: The highest frequency of antiretroviral DRMs was related to NRTIs and NNRTIs. In contrast, PI resistance mutations had the lowest frequency. Laboratory-guided ART to avoid the expansion of mutants as well as investigating DRMs in other viral regions, such as integrase, are recommended.

Molecular Mechanism of Resistance in a Clinically Significant Double-Mutant Variant of HCV NS3/4A Protease

Despite significant progress in hepatitis C virus (HCV) protease inhibitor (PI) drug design, resistance remains a problem causing treatment failure. Double-substitution variants, notably Y56H/D168A, have emerged in patients who fail therapy with a PI-containing regimen. The resistance conferred by Asp168 substitutions has been well characterized and avoided in newer inhibitors. However, an additional mutation at Tyr56 confers resistance to even the most robust inhibitors. Here, we elucidate the molecular mechanisms of resistance for the Y56H/D168A variant against grazoprevir (and four analogs), paritaprevir, and danoprevir through inhibition assays, co-crystal structures, and molecular dynamics simulations. The PIs' susceptibility to Y56H/D168A varies, with those stacking on the catalytic His57 losing the most potency. For such inhibitors, the Y56H substitution disrupts favorable stacking interactions with the neighboring catalytic His57. This indirect mechanism of resistance threatens to cause multi-PI failure as all HCV PIs in clinical development rely on interactions with the catalytic triad.

Applications of Click Chemistry in the Development of HIV Protease Inhibitors.

Acquired Immunodeficiency Syndrome (AIDS) has been devastating for millions of people around the world. Inhibition of the human immunodeficiency virus (HIV) protease is among the most important approaches for the therapeutic intervention in HIV infection. Since the discovery of the HIV-1 protease, this enzyme has been considered as a key target for the inhibition of viral replication. A large body of research has been done to develop an effective HIV-1 protease inhibitor. There are to date 10 HIV-1 protease inhibitor drugs approved by the Food and Drug Administration (FDA) that have improved the survival and quality of life of HIV infected people. These drugs are prescribed in combination with the reverse transcriptase inhibitors, which is referred to as highly active antiretroviral therapy (HAART). The HIV-1 protease inhibitors play a vital role in HAART. The applications of click chemistry are dispersing in the field of drug discovery. Recently, click chemistry has captured a lot of attention and has become a powerful tool for the synthesis of medicinal skeletons in the discovery of anti-HIV drugs. Click reaction is a well-known method for making carbon−heteroatom−carbon bonds. Click reactions are popular because they are wide in scope, of high yielding, quick to perform, and easy to purify. In this review, we outlined current approaches towards the development of HIV-1 protease inhibitors employing click chemistry.

P-E1 A novel way to test and discover new inhibitors against drug resistant HIV-1 proteases

HIV-1 protease (PR) inhibitor (PI) is one of the most potent anti-HIV drugs. When it is used in combination with other drugs, if could suppress HIV to an undetectable level. However, successful treatment is often threaten by emergence of viral drug resistance of PRs (vdrPRs). Three vdrPRs were isolated from HIV-infected patients that carry 7 (M7PR), 10 (M10PR) and 11 (M11PR) PR gene mutations, respectively. They were expressed in a gene-inducible fission yeast system to allow the measurement of PR-specific activities. All 3 vdrPRs proteolyzed natural HIV viral substrates and conferred drug resistance to Indinavir in the fission yeast, suggesting they maintained the same proteolytic and drug resistant activities in the fission yeast as in mammalian cells. Moreover, the viral enzymatic activities of these vdrPRs coupled with the induction of growth inhibition and cell death, which could potentially be used as endpoints to test the efficacy of PI activities. In this study, 5 investigational PIs were used to test the utility of the PR-producing yeast system with Darunavir (DRV) as a control. All 6 compounds suppressed the wildtype PR and the M7PR-mediated activities. However, none of them suppressed activities conferred by M10PR or M11PR. The fact that M10PR and M11PR were resistant to all of the existing PI drugs including DRV, underscores the importance of continued searching for new PIs against vdrPRs. The described fission yeast cell-based system might be suitable for future testing or discovery of new PIs through high-throughput drug screening. Because this yeast cell-based method is function-driven. It has no presumption of what kind of PI will be found. It has the potential to uncover novel PIs.

Tenofovir alafenamide plus emtricitabine versus abacavir plus lamivudine for treatment of virologically suppressed HIV-1-infected adults: a randomised, double-blind, active-controlled, non-inferiority phase 3 trial

Abacavir and tenofovir alafenamide offer reduced bone toxicity compared with tenofovir disoproxil fumarate. We aimed to compare safety and efficacy of tenofovir alafenamide plus emtricitabine with that of abacavir plus lamivudine. In this randomised, double-blind, active-controlled, non-inferiority phase 3 trial, HIV-1-positive adults (≥18 years) were screened at 79 sites in 11 countries in North America and Europe. Eligible participants were virologically suppressed (HIV-1 RNA <50 copies per mL) and on a stable three-drug regimen containing abacavir plus lamivudine. Participants were randomly assigned (1:1) by a computer-generated allocation sequence (block size 4) to switch to fixed-dose tablets of tenofovir alafenamide (10 mg or 25 mg) plus emtricitabine (200 mg) or remain on abacavir (600 mg) plus lamivudine (300 mg), with matching placebo, while continuing to take the third drug. Randomisation was stratified by the third drug (boosted protease inhibitor vs other drug) at screening. Investigators, participants, and study staff giving treatment, assessing outcomes, and collecting data were masked to treatment group. The primary endpoint was the proportion of participants with virological suppression (HIV-1 RNA <50 copies per mL) at week 48 (assessed by snapshot algorithm), with a 10% non-inferiority margin. We analysed the primary endpoint in participants enrolled before May 23, 2016 (when target sample size was reached), and we analysed safety in all enrolled participants who received at least one dose of study drug (including patients enrolled after these dates). This study was registered with ClinicalTrials.gov, number NCT02469246. Study enrolment began on June 29, 2015, and the cutoff enrolment date for the week 48 primary endpoint analysis was May 23, 2016. 501 participants were randomly assigned and treated. At week 48, virological suppression was maintained in 227 (90%) of 253 participants receiving tenofovir alafenamide plus emtricitabine compared with 230 (93%) of 248 receiving abacavir plus lamivudine (difference -3·0%, 95% CI -8·2 to 2·0), showing non-inferiority. Few participants discontinued treatment because of adverse events: 12 (4%) of 280 participants in the tenofovir alafenimide plus emtricitabine group and nine (3%) of 276 in the abacavir plus lamivudine group. Three participants had serious, treatment-related adverse events: one each with renal colic and neutropenia in the tenofovir alafenamide plus emtricitabine group, and one myocardial infarction in the abacavir plus lamivudine group. There were no treatment-related deaths. Tenofovir alafenamide, in combination with emtricitabine and various third drugs, maintained high efficacy with a renal and bone safety profile similar to that of abacavir. In virologically suppressed patients, a regimen containing tenofovir alafenamide could be an alternative to those containing abacavir, without concern for new onset of renal or bone toxicities or hyperlipidaemia. Gilead Sciences Inc.

Capillary zone electrophoresis method to assay tipranavir capsules and identification of oxidation product and organic impurity by quadrupole-time of flight mass spectrometry

Tipranavir (TPV) is one of the most recently developed protease inhibitors (PI) and it is specially recommended for treatment-experienced patients who are resistant to other PI drugs. In this work, a simple and friendly environmental CZE stability-indicating method to assay TPV capsules was developed and two TPV organic impurities were identified by high resolution mass spectrometry (HRMS). The optimized analytical conditions were: background electrolyte composed of sodium borate 50mM, pH 9.0 and 5% of methanol; voltage + 28kV; hydrodynamic injection of 5s (100mbar), detection wavelength 240nm, at 25°C. The separation was achieved in a fused silica capillary with 50µm × 40cm (inner diameter × effective length), using furosemide as internal standard. All the validation parameters were met and the method was specific, even in the presence of degradation products and impurities. Oxidation was indicated as the main degradation pathway among those evaluated in this study (acidic, alkaline, thermal, photolytic and oxidative) and it showed a second order degradation kinetic, under the conditions used in this study. The main oxidation product and an organic impurity detected in the standard were characterized by Q-TOF, and both of them correspond to oxidation products of TPV.

HIV drug resistance in HIV positive individuals under antiretroviral treatment in Shandong Province, China.

The efficacy of antiretroviral drugs is limited by the development of drug resistance. Therefore, it is important to examine HIV drug resistance following the nationwide implementation of drug resistance testing in China since 2009. We conducted drug resistance testing in patients who were already on or new to HIV antiretroviral therapy (ART) in Shandong Province, China, from 2011 to 2013, and grouped them based on the presence or absence of drug resistance to determine the effects of age, gender, ethnicity, marital status, educational level, route of transmission and treatment status on drug resistance. We then examined levels of drug resistance the following year. The drug resistance rates of HIV patients on ART in Shandong from 2011 to 2013 were 3.45% (21/608), 3.38% (31/916), and 4.29% (54/1259), per year, respectively. M184V was the most frequently found point mutation, conferring resistance to the nucleoside reverse transcriptase inhibitor, while Y181C, G190A, K103N and V179D/E/F were the most frequent point mutations conferring resistance to the non-nucleoside reverse transcriptase inhibitor. In addition, the protease inhibitor drug resistance mutations I54V and V82A were identified for the first time in Shandong Province. Primary resistance accounts for 20% of the impact factors for drug resistance. Furthermore, it was found that educational level and treatment regimen were high-risk factors for drug resistance in 2011 (P<0.05), while treatment regimen was a high risk factor for drug resistance in 2012 and 2013 (P<0.05). Among the 106 drug-resistant patients, 77 received immediate adjustment of treatment regimen following testing, and 69 (89.6%) showed a reduction in drug resistance the following year. HIV drug resistance has a low prevalence in Shandong Province. However, patients on second line ART regimens and those with low educational level need continuous monitoring. Active drug resistance testing can effectively prevent the development of drug resistance.

Design and construction of a synthetic E. coli protease inhibitor detecting biomachine.

Protease inhibitors (PIs) have been used to treat various types of symptoms or diseases. However, current PIs block the protease activity by targeting the protease active site which has been shown to be sensitive to the off-target effect due to crossreactivity with protease homologues. An alternative approach to inhibiting protease activity is to target the substrate, specifically by blocking the substrate cleavage site. We propose to employ synthetic biology approach to create a synthetic E. coli to be used as a protease inhibitor detecting biomachine that can effectively isolate intrabodies, a new generation of protease inhibitor drug. The in vivo selection system, comprised of three biological devices, i.e., protease activity detector, protease generator and protease blocking devices, is based on the ability to transport folded protein of the E. coli twin-arginine translocation (Tat) pathway and antibiotic resistance of TEM-1 β-lactamase (Bla) using as reporter protein. By linking protease degradation to antibiotic resistance, we can isolate the suitable intrabodies simply by plating cells containing appropriate devices on solid agar containing β-lactam ring antibiotics. As a proof of concept, we applied a previously isolated HIV-1 p17 intrabody (scFvp17) that binds to the C-terminus of HIV-1 matrix protein (p17) to our synthetic E. coli. This work demonstrated that binding of scFvp17 to its epitope on p17 can physically interfere with HIV-1 protease activity and inhibit proteolytic cleavage at the p17Δp24 cleavage site when expressed in the designed format. The device was optimized by varying plating conditions such as incubation temperatures, induction levels, and Carbenicillin concentrations which was used as selection pressure. The feasibility of this assay has opened the door to protease inhibitor selection which can be used for various applications such as optimization of the current protease inhibitors and selection of new ones.

Prevalence of HIV-1 transmitted drug resistance in the incarcerated population.

The aim of the study was to determine the prevalence of transmitted drug resistance (TDR)-associated mutations among treatment-naïve, incarcerated individuals with HIV-1 infection in the USA as well as the class TDR and antiretroviral (ARV) mutations present at baseline. Patients over the age of 18 years were included in the study if they had been diagnosed with HIV infection, if their HIV infection was managed through telemedicine and if they were incarcerated in the State of Illinois Department of Corrections between 10 July 2010 and 29 April 2016. Additionally, the patients were required to have a documented genotype and be ARV-naïve. A medical chart review was conducted to assess demographic information, disease burden, and risk factors for acquiring the virus. The inclusion criteria were met for 105 patients. A total of 24 patients (23%) had a clinically significant mutation associated with resistance to any drug class. The prevalence of mutations conferring clinically significant resistance was 19% for nonnucleoside reverse transcriptase inhibitors (NNRTIs), 18% for nucleoside reverse transcriptase inhibitors (NRTIs), and 4% for protease inhibitors (PIs). Five per cent of patients had dual-class TDR to both NRTI and NNRTI drug classes and 2% of patients had mutations to both NNRTI and PI drug classes. There was no significant increase in the prevalence of clinically relevant drug resistance mutations based on demographics, burden of disease, or risk factors for acquiring the virus. A high prevalence of TDR was identified in the ARV-naïve incarcerated population. The results of this study indicate an increased prevalence of TDR in a largely unstudied incarcerated population, demonstrating the need for increased monitoring of resistance in HIV-infected patients world-wide.

Determination of drug resistance mutations of NS3 inhibitors in chronic hepatitis C patients infected with genotype 1

Direct-acting antiviral agents (DAA) such as NS3 protease inhibitors is the first class of drugs used for chronic hepatitis C (CHC) treatment. NS3 inhibitors (PI) with low genetic barrier have been approved to be used in the CHC genotype 1 infections, and in the treatment of compensated liver disease including cirrhosis together with pegile interferon and ribavirin. Consequently, the development of drug resistance during DAA treatment of CHC is a major problem. NS3 resistant variants can be detected before treatment as they can occurnaturally. The aim of this study was to investigate new and old generation NS3 inhibitors resistance mutations before DAA treatment in hepatitis C virus (HCV) that were isolated from CHC. The present study was conducted in 2015 and included 97 naive DAA patients infected with HCV genotype 1, who were diagnosed in Manisa and Kocaeli cities of Turkey. Magnetic particle based HCV RNA extraction and than RNA detection and quantification were performed using commercial real-time PCR assay QIASypmhony + Rotorgene Q/ArtusHCV QS-RGQ and COBAS Ampliprep/COBAS TaqMan HCV Tests. HCV NS3 viral protease genome region was amplified with PCR and mutation analysis was performed by Sanger dideoxy sequencing technique of NS3 protease codons (codon 32-185). HCV NS3 protease inhibitors; asunaprevir, boceprevir, faldaprevir, grazoprevir, pariteprevir, simeprevir and telaprevir were analysed for resistant mutations by Geno2pheno-HCV resistance tool. HCV was genotyped in all patients and 88 patients (n= 88/97, 91%) had genotype 1. Eight (n= 8/97, 8.2%) and 80 (n= 80/97, 82.4%) HCC patients were subgenotyped as 1a and 1b, respectively. Many aminoacid substitutions and resistance mutations were determined in 39/88 (44%) patients in the study group. Q80L, S122C/N, S138W were defined as potential substitutions (6/88 patients; 7%); R109K, R117C, S122G, I132V, I170V, N174S were described as potential resistance (34/88 patients; 39%); V36L, T54S, V55A, Q80H were characterized as resistance (7/88 patients; 8%) and Q80K, A156S were defined as high resistance (3/88 patients; 3%) mutations. Based on resistance and high resistance mutations, clinically significant mutations were defined in 10/88 (11%) of the patients. Our study shows that it is essential to analyse HCV NS3 protease inhibitors drug resistance before DAA treatment of CHC patients. On the other hand, our results pointed out that analysis of NS5A and NS5B genome region mutations may also be required in the near future.

A19 Genetic markers for protease inhibitor drug resistance in regions outside of the protease gene.

A19 Genetic markers for protease inhibitor drug resistance in regions outside of the protease gene.

A fission yeast cell-based system for multidrug resistant HIV-1 proteases

BackgroundHIV-1 protease (PR) is an essential enzyme for viral production. Thus, PR inhibitors (PIs) are the most effective class of anti-HIV drugs. However, the main challenge to the successful use of PI drugs in patient treatment is the emergence of multidrug resistant PRs (mdrPRs). This study aimed to develop a fission yeast cell-based system for rapid testing of new PIs that combat mdrPRs.ResultsThree mdrPRs were isolated from HIV-infected patients that carried seven (M7PR), ten (M10PR) and eleven (M11PR) PR gene mutations, respectively. They were cloned and expressed in fission yeast under an inducible promoter to allow the measurement of PR-specific proteolysis and drug resistance. The results showed that all three mdrPRs maintained their abilities to proteolyze HIV viral substrates (MA↓CA and p6) and to confer drug resistance. Production of these proteins in the fission yeast caused cell growth inhibition, oxidative stress and altered mitochondrial morphologies that led to cell death. Five investigational PIs were used to test the utility of the established yeast system with an FDA-approved PI drug Darunavir (DRV) as control. All six compounds suppressed the wildtype PR (wtPR) and the M7PR-mediated activities. However, none of them were able to suppress the M10PR or the M11PR.ConclusionsThe three clinically isolated mdrPRs maintained their viral proteolytic activities and drug resistance in the fission yeast. Furthermore, those viral mdrPR activities were coupled with the induction of growth inhibition and cell death, which could be used to test the PI activities. Indeed, the five investigational PIs and DRV suppressed the wtPR in fission yeast as they did in mammalian cells. Significantly, two of the high level mdrPRs (M10PR and M11PR) were resistant to all of the existing PI drugs including DRV. This observation underscores the importance of continued searching for new PIs against mdrPRs.

THU-198 - Cross-sectional assessment of >20,000 clinical samples submitted for HCV NS3/4A protease inhibitor drug resistance testing in the US

THU-198 - Cross-sectional assessment of >20,000 clinical samples submitted for HCV NS3/4A protease inhibitor drug resistance testing in the US

Mass spectrometry captures off-target drug binding and provides mechanistic insights into the human metalloprotease ZMPSTE24.

Off-target binding of hydrophobic drugs can lead to unwanted side effects, either through specific or nonspecific binding to unintended membrane protein targets; however, distinguishing the binding of drugs to membrane proteins from that of detergents, lipids and cofactors is challenging. Here we use high-resolution mass spectrometry to study the effects of HIV protease inhibitors on the human zinc metalloprotease ZMPSTE24. This intramembrane protease plays a major role in converting prelamin A to mature lamin A. We monitored proteolysis of farnesylated prelamin A peptide by ZMPSTE24 and unexpectedly found retention of the C-terminal peptide product with the enzyme. We also resolved binding of zinc, lipids, and HIV protease inhibitors and showed that drug binding blocked prelamin A peptide cleavage and conferred stability to ZMPSTE24. Our results not only have relevance for the progeria-like side effects of certain HIV protease inhibitor drugs but also highlight new approaches for documenting off-target drug binding.

Protease Inhibitors Drug Resistance Mutations in Turkish Patients with Chronic Hepatitis C.

Drug resistance development is an expected problem during treatment with protease inhibitors (PIs), this is largely due to the fact that Pls are low-genetic barrier drugs. Resistance-associated variants (RAVs) however may also occur naturally, and prior to treatment with Pls, the clinical impact of this basal resistance remains unknown. In Turkey, there is yet to be an investigation into the hepatitis C (HCV) drug associated resistance to oral antivirals. 178 antiviral-naïve patients infected with HCV genotype 1 were selected from 27 clinical centers of various geographical regions in Turkey and included in the current study. The basal NS3 Pls resistance mutations of these patients were analyzed. In 33 (18.5%) of the patients included in the study, at least one mutation pattern that can cause drug resistance was identified. The most frequently detected mutation pattern was T54S while R109K was the second most frequently detected. Following a more general examination of the patients studied, telaprevir (TVR) resistance in 27 patients (15.2%), boceprevir (BOC) resistance in 26 (14.6%) patients, simeprevir (SMV) resistance in 11 (6.2%) patients and faldaprevir resistance in 13 (7.3%) patients were detected. Our investigation also revealed that rebound developed in the presence of a Q80K mutation and amongst two V55A mutations following treatment with TVR, while no response to treatment was detected in a patient with a R55K mutation. We are of the opinion that drug resistance analyses can be beneficial and necessary in revealing which variants are responsible for pre-treatment natural resistance and which mutations are responsible for the viral breakthrough that may develop during the treatment.

Detecting primary drug-resistant mutations in Korean HIV patients using ultradeep pyrosequencing

HIV primary resistance, drug resistance in treatment-naïve patients, is an emerging public health issue. The prevalence of HIV primary resistance mutations down to the level of 1% minor variants was investigated using ultradeep pyrosequencing (UDPS) in HIV-positive Korean blood donors and in treatment naïve chronic patients for the comparison. The entire pol region was sequenced from 25 HIV-positive blood donors, and 18 treatment-naïve chronic HIV patients. UDPS was successful in 19 blood donors and 18 chronic patients. In total, 1,011,338 sequence reads were aligned, and 28,093 sequence reads were aligned on average per sample. The prevalence of HIV primary resistance mutations in the HIV-positive blood donors and chronic HIV patients were 63.2% and 44.4% according to UDPS, respectively. Protease inhibitor (PI) drugs demonstrated different patterns in HIV-positive blood donors and chronic HIV patients, whereas non-nucleoside reverse transcriptase inhibitors (NNRTI), nucleoside reverse transcriptase inhibitors (NRTI), and integrase inhibitor (INI) drugs showed similar patterns between the two groups. Higher level of primary resistance prevalence was observed mainly because UDPS method could detect mutations in minor variants with 1–10% frequency. The higher resistance prevalence was observed in HIV-positive blood donors than in chronic patients. Considering that treatments for HIV-infected patients were recently amended to start at an earlier stage, information about degree of drug resistance to each drug between the two groups would help to establish future policies, design additional clinical trials, assess HIV patient care in Korea.

Liver Toxicity in HIV – Infected Patients Receiving Antiretroviral Therapy That Includes HIV – I Protease Inhibitors.

The present paper describes possible connections between antiretroviral therapies (ARTs) - Protease Inhibitor Drugs, used to treat human immunodeficiency virus (HIV) infection and adverse drug reactions (ADRs) encountered predominantly in the liver. Similarly, hepatitis B and /or C virus confection has been associated with a greater risk of Drug - Induced liver Injury, compared with those with no Hepatitis. The study includes prescriptions of 50 HIV seropositive patients (aged between 10 and 50 years) who reported for treatment at the outpatient ward of Santosh Medical College Hospital & Research Centre, Ghaziabad. Since After initiation to therapy, serum AST and ALT levels increased significantly to 32% and 18% and Serum HBs Ag and HCV levels increased significantly to 36% and 20%.The study affirms the potential risk of hepatotoxicity for HIV seropositive patients on an Antiretroviral Protease Inhibitor drugs and calls for continuous monitoring of ARV administration so as to prevent fatal effects of hepatotoxicity.

Global stability and persistence of HIV models with switching parameters and pulse control

This paper studies some HIV (Human Immunodeficiency Virus) models with switching parameters and pulse control. By taking into account of the effects of reverse transcriptase inhibitor (RTI) drugs, protease inhibitor (PI) drugs and the variable transmission rate, we propose a new HIV model with switching parameters and derive a general threshold value that measures the persistence of the disease. Furthermore, pulse vaccination is applied to the HIV model and some novel threshold conditions are established to ensure the existence and stability of the periodic infection-free solution. In contrast to the standard HIV models, it is shown that our proposed models are more practical and useful. Moreover, pulse vaccination strategies are proven to be more effective in determining whether or not the disease is eradicated. Numerical simulations are carried out to illustrate the effectiveness of the obtained results, and future research directions are suggested.

In Process Citation

Approximately 70.000 people are infected with hepatitis C virus in Hungary, more than half of whom are not aware of their infection. From the point of infected individuals early recognition and effective treatment of related liver injury may prevent consequent advanced liver diseases and complications (liver cirrhosis, liver failure and liver cancer) and can increase work productivity and life expectancy on one hand. From socioeconomic aspect, this could also prevent further spread of the virus as well as reduce substantially long term financial burden of related morbidity. Available since 2003 in Hungary, pegylated interferon + ribavirin dual therapy can clear the virus in 40-45% of previously not treated (naïve), and in 5-21% of previous treatment-failure patients. Addition of a direct acting first generation protease inhibitor drug (boceprevir or telaprevir) to the dual therapy increases the chance of sustained virologic response to 63-75% and 59-66%, respectively. These two protease inhibitors are available and financed for a segment of Hungarian patients since May 2013. Between 2013 and February 2015, other direct acting antiviral interferon-free combination therapies have been registered for the treatment of chronic hepatitis C, with a potential efficacy over 90% and typical short duration of 8-12 weeks. Indication of therapy includes exclusion of contraindications to the drugs and demonstration of viral replication with consequent liver injury, i.e., inflammation and or fibrosis in the liver. Non-invasive methods (eleastography and biochemical methods) are accepted and preferred for staging liver damage (fibrosis). For initiation of treatment accurate and timely molecular biology tests are mandatory. Eligibility for treatment is a subject of individual central medical review. Due to budget limitations tharpy is covered only for a proportion of patients by the National Health Insurance Fund. Priority is given to those with urgent need based on a Hungarian Priority Index system reflecting primarily the stage of liver disease, and considering also additional factors, i.e., activity and progression of liver disease, predictive factors of treatment and other special issues. Approved treatments are restricted to the most cost-effective combinations based on the cost per sustained virologic response value in different patient categories with consensus between professional organizations, National Health Insurance Fund and patient organizations. More expensive therapies might be available upon co-financing by the patient or a third party. Interferon-free treatments and shorter therapy durations preferred as much as financially feasible. A separate budget is allocated to cover interferon-free treatments for the most-in-need interferon ineligible/intolerant patients, and for those who have no more interferon-based therapy option. Orv. Hetil., 2015, 156(Suppl. 2), 3-24.