Darunavir: a critical review of its properties, use and drug interactions

Harnessing nanotechnology in HIV therapy: Exploring molecular pathogenesis and treatment strategies with special reference to chemotherapy and immunotherapy

Human immunodeficiency virus (HIV) continues to be a global threat, contributing substantially to social and economic burdens worldwide. Synthetic ARV drugs are classified into six different classes viz NRTIs, NNRTIs, PIs, IIs, INSTIs, and FIs. Highly active anti-retroviral therapy (HAART) which is a combination of two or more ARV drugs from different classes is gaining immense popularity in the HIV therapy regimen due to its better therapeutic outcome. However, despite its successful endeavor in significant viral suppression, synthetic drugs are associated with numerous adverse effects. To mitigate this issue, scientists are exploring ARV agents derived from various natural sources like plants, and marine organisms that can exhibit potent anti-HIV activity with minimal side effects. Nevertheless, both synthetically and naturally derived ARV agents have failed to exhibit eradication of HIV from latent reservoirs. Henceforth, researchers are shifting their attention towards formulating a drug-encapsulated nano-delivery system to ensure a significant amount of drug delivery into these reservoirs. Additionally, the discovery of a novel HIV vaccine that can induce robust immune responses against multiple HIV strains and facilitate complete removal of the virus before the establishment of a latent reservoir is the need of an hour. Briefly, we discussed various synthetic and natural chemotherapeutic agents along with their specificity and limitations, different drug-delivery devices for ART, immunotherapy, vaccines, and lastly, challenges and strategies associated with vaccine development.

Overcoming Solubility Challenges: Self-emulsifying Systems for Enhancing the Delivery of Poorly Water-Soluble Antiviral Drugs

The primary goal of drug formulation is to improve a drug's bioavailability in the body. However, poorly water-soluble drugs present challenging issues related to their solubility and bioavailability factors. Emerging technologies, such as lipid-based drug delivery systems, including micro- or nanoemulsifying drug delivery systems, have become increasingly relevant to address the above challenges. This review presents a thorough overview of self-emulsifying drug delivery systems (SEDDS). It covers the properties, principles, self-emulsification mechanism, formulation strategies, and characterization methods of SEDDS. This review also addresses the delivery of antiviral agents through SEDDS. Moreover, it summarizes the marketed formulations of SEDDS consisting of antiviral agents. This review offers a comprehensive and valuable resource for future perspectives on SEDDS and their potential applications in antiviral drug delivery.

A toolbox for mimicking gastrointestinal conditions in children: Design and evaluation of biorelevant dissolution media for mimicking paediatric gastric- and small intestinal conditions

The goal of the present work was to develop an in vitro toolbox to evaluate the oral administration of dosage forms to children of different age groups and under different administration conditions (fasted/fed). Based on current data on the gastrointestinal physiology of children, a set of new biorelevant media was designed to mimic the composition and physicochemical properties of resting gastric and resting small intestinal fluid in children of different age groups. In addition, guidelines were developed on how to generate fasted and fed state gastric and small intestinal fluids by combining these media with age-specific drinking volumes or portions of already established simulated paediatric breakfast meals, respectively. These fluids can simulate the conditions in the paediatric stomach and small intestine after administration of a dosage form in the fasting state or after a breakfast. The in vitro toolbox was evaluated using the example of pre-school children with a total of five paediatric medicines. Results from the corresponding set of in vitro studies highlight the importance of addressing patient-specific characteristics rather than downscaling existing adult in vitro models.

Pharmacokinetic Drug-Drug Interactions Involving Antiretroviral Agents: An Update

Antiretroviral therapy is the recognized treatment for human immunodeficiency virus (HIV) infection involving several antiviral agents. Even though highly active antiretroviral therapy has been proven to be very effective in suppressing HIV replication, the antiretroviral drugs, belonging to different pharmacological classes, present quite complex pharmacokinetic properties such as extensive drug metabolism and transport by membrane-associated drug carriers. Moreover, due to uncomplications or complications in HIV-infected populations, an antiretroviralbased multiple-drug coadministration therapy strategy is usually applied for treatment effect, thus raising the possibility of drug-drug interactions between antiretroviral drugs and common drugs such as opioids, stains, and hormonal contraceptives. Herein, thirteen classical antiretroviral drugs approved by US Food and Drug Administration were summarized. Besides, relative drug metabolism enzymes and transporters known to interact with those antiretroviral drugs were detailed and described. Furthermore, one after the summarized antiretroviral drugs, the drug-drug interactions between two antiretroviral drugs or antiretroviral drug - conventional medical drugs of the past decade were discussed and summarized. This review is intended to deepen the pharmacological understanding of antiretroviral drugs and promote more secure clinical applications for antiretroviral drugs to treat HIV.

Management of Antiretroviral Therapy with Boosted Protease Inhibitors-Darunavir/Ritonavir or Darunavir/Cobicistat

A major challenge in the management of antiretroviral therapy (ART) is to improve the patient's adherence, reducing the burden caused by the high number of drugs that compose the treatment regimens for human immunodeficiency virus positive (HIV+) patients. Selection of the most appropriate treatment regimen is responsible for therapeutic success and aims to reduce viremia, increase the immune system response capacity, and reduce the incidence rate and intensity of adverse reactions. In general, protease inhibitor (PI) is one of the pillars of regimens, and darunavir (DRV), in particular, is frequently recommended, along with low doses of enzyme inhibitors as cobicistat (COBI) or ritonavir (RTV), by the international guidelines. The potential of clinically significant drug interactions in patients taking COBI or RTV is high due to the potent inhibitory effect on cytochrome CYP 450, which attracts significant changes in the pharmacokinetics of PIs. Regardless of the patient or type of virus, the combined regimens of DRV/COBI or DRV/RTV are available to clinicians, proving their effectiveness, with a major impact on HIV mortality/morbidity. This study presents current information on the pharmacokinetics, pharmacology, drug interactions, and adverse reactions of DRV; it not only compares the bioavailability, pharmacokinetic parameters, immunological and virological responses, but also the efficacy, advantages, and therapeutic disadvantages of DRV/COBI or DRV/RTV combinations.

The situation of small molecules targeting key proteins to combat SARS-CoV-2: Synthesis, metabolic pathway, mechanism of action, and potential therapeutic applications

Due to the global epidemic and high mortality of 2019 coronavirus disease (COVID-19), there is an immediate need to discover drugs that can help before a vaccine becomes available. Given that the process of producing new drugs is so long, the strategy of repurposing existing drugs is one of the promising options for the urgent treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19 disease. Although FDA has approved Remdesivir for the use in hospitalized adults and pediatric patients suffering from COVID-19, no fully effective and reliable drug has been yet identified worldwide to treat COVID-19 specifically. Thus, scientists are still trying to find antivirals specific to COVID-19. This work reviews the chemical structure, metabolic pathway, mechanism of action of existing drugs with potential therapeutic applications for COVID-19. Further, we summarized the molecular docking stimulation of the medications related to key protein targets. These already drugs could be developed for further clinical trials to supply suitable therapeutic options for patients suffering from COVID-19.

Preparation and Characterization of Two Immunogens and Production of Polyclonal Antibody with High Affinity and Specificity for Darunavir

Darunavir (DRV) is a potent antiviral drug used for treatment of infections with human immunodeficiency virus (HIV). Effective and safe treatment with DRV requires its therapeutic drug monitoring (TDM) in patient's plasma during therapy. To support TDM of DRV, a specific antibody with high affinity is required in order to develop a sensitive immunoassay for the accurate determination of DRV in plasma. In this study, two new and different immunogens were prepared and characterized. These immunogens were the DRV conjugates with keyhole limpet hemocyanin (KLH) protein. The first immunogen (DRV-KLH) was prepared by zero-length direct linking of DRV via its aromatic amino group with the tyrosine amino acid residues of KLH by diazotization/coupling reaction. The second immunogen (G-DRV-KLH) was prepared by conjugation of the N-glutaryl derivative of DRV (G-DRV) with KLH. The 5-carbon atoms-spacing G-DRV hapten was synthesized by reaction of DRV via its aromatic amino group with glutaric anhydride. The reaction was monitored by HPLC and the chemical structure of G-DRV was confirmed by mass, ¹H-NMR, and ¹³C-NMR spectroscopic techniques. The hapten (G-DRV) was linked to the KLH protein by water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) coupling procedure. The pertinence of the coupling reactions of haptens to protein was confirmed, and the immunogens were characterized by ultraviolet (UV) spectrophotometry. Both DRV-KLH and G-DRV-KLH were used for the immunization of animals and the animal's antiserum that showed the highest affinity was selected. The collected antiserum (polyclonal antibody) had very high affinity to DRV (IC₅₀ value = 0.2 ng mL^-1; defining IC₅₀ as the DRV concentration that can inhibit antibody binding by 50% of its maximum binding) and high specificity to DRV among other drugs used in the combination therapy with DRV. Cumulative results from direct and competitive enzyme-linked immunosorbent assay (ELISA) using this polyclonal antibody proved that the immunogens were highly antigenic and elicited a specific polyclonal antibody. The produced polyclonal antibody is valuable for the development of highly sensitive and selective immunoassays for TDM of DRV.

Darunavir: A comprehensive profile

Darunavir: (3R,3aS,6aR)-hexahydrofuro[2,3-b]furan-3-yl [(2S,3R)-4-{[(4-aminophenyl)sulfonyl] (isobutyl)amino}-3-hydroxy-1-phenyl-2-butanyl]carbamate is a synthetic non-peptide protease inhibitor. On June 2006, it was first approved by the Food and Drug administration (FDA) for treatment of resistant type-1 of the human immunodeficiency virus (HIV). In July 2016, the FDA expanded the approval for use of darunavir in pregnant women with HIV infection. Darunavir prevents the replication of HIV virus by inhibiting the catalytic activity of the HIV-1 protease enzyme, and selectively inhibits the cleavage of HIV encoded Gag-Pol polyproteins in virus-infected cells, which prevents the formation of mature infectious virus particles. Darunavir is unique among currently available protease inhibitors because it maintains antiretroviral activity against a variety of multidrug-resistant HIV strains. This article discusses, by a critical extensive review of the literature, the description of darunavir in terms of its names, formulae, elemental composition, appearance, and use in the treatment of HIV-infected patients. The article also discusses the methods for preparation of darunavir, its physical-chemical properties, analytical methods for its determination, pharmacological properties, and dosing information.

Targeting eukaryotic proteases for natural products-based drug development

Covering: up to April 2020 Proteases are involved in the regulation of many physiological processes. Their overexpression and dysregulated activity are linked to diseases such as hypertension, diabetes, viral infections, blood clotting disorders, respiratory diseases, and cancer. Therefore, they represent an important class of therapeutic targets. Several protease inhibitors have reached the market and >60% of them are directly related to natural products, even when excluding synthetic natural product mimics. Historically, natural products have been a valuable and validated source of therapeutic agents, as over half of the marketed drugs across targets and diseases are inspired by natural product structures. In the past two decades the number of new protease inhibitors discovered from nature has sharply increased. Additionally, the availability of 3D structural information for proteases has permitted structure-based design and accelerated the synthesis of optimized lead structures with improved potency and selectivity profiles, resulting in some of the most-potent-in-class inhibitors. These discoveries were oftentimes maximized by in-depth biological assessments of lead inhibitors, linking them to a relevant disease state. This review will discuss some of the current and emerging drug targets and their involvement in various disease processes, highlighting selected success stories behind several FDA-approved protease inhibitors that have natural products scaffolds as well as recent selected pharmacologically well-characterized inhibitors derived from marine or terrestrial sources.

Development of a highly sensitive ELISA for determination of darunavir in plasma samples using a polyclonal antibody with high affinity and specificity

Aim: To support pharmacokinetic studies and therapeutic monitoring of darunavir (DRV), a highly sensitive ELISA was developed for the determination of DRV in plasma samples at picogram levels. Results: The assay LOD and LOQ were 15 and 30 pg ml-1, respectively. The working range of the assay was 20–2000 pg ml-1. Analytical recoveries of DRV from spiked plasma were in the ranges of 98.4–113.0 and 86.0–99.1% for intra-assay and inter-assay runs, respectively. The precision of the assay was satisfactory. Conclusion: The ELISA is characterized by high throughput and it is expected to significantly contribute to routine analysis of DRV in its pharmacokinetic studies and therapeutic monitoring.

Protease Inhibitors for the Treatment of HIV/AIDS: Recent Advances and Future Challenges

Acquired Immunodeficiency Syndrome (AIDS) is a chronic disease characterized by multiple life-threatening illnesses caused by a retro-virus, Human Immunodeficiency Virus (HIV). HIV infection slowly destroys the immune system and increases the risk of various other infections and diseases. Although, there is no immediate cure for HIV infection/AIDS, several drugs targeting various cruxes of HIV infection are used to slow down the progress of the disease and to boost the immune system. One of the key therapeutic strategies is Highly Active Antiretroviral Therapy (HAART) or ' AIDS cocktail' in a general sense, which is a customized combination of anti-retroviral drugs designed to combat the HIV infection. Since HAART's inception in 1995, this treatment was found to be effective in improving the life expectancy of HIV patients over two decades. Among various classes of HAART treatment regimen, Protease Inhibitors (PIs) are known to be widely used as a major component and found to be effective in treating HIV infection/AIDS. For the past several years, a variety of protease inhibitors have been reported. This review outlines the drug design strategies of PIs, chemical and pharmacological characteristics of some mechanism-based inhibitors, summarizes the recent developments in small molecule based drug discovery with HIV protease as a drug target. Further discussed are the pharmacology, PI drug resistance on HIV PR, adverse effects of HIV PIs and challenges/impediments in the successful application of HIV PIs as an important class of drugs in HAART regimen for the effective treatment of AIDS.

Antiviral Drugs

Viruses are major pathogenic agents causing a variety of serious diseases in humans, other animals, and plants.

Drugs that combat viral infections are called antiviral drugs. There are no effective antiviral drugs for many viral infections. However, there are several drugs for influenza, a couple of drugs for herpesviruses, and some new antiviral drugs for treatment of HIV and hepatitis C infections.

The arsenal of antivirals is complex. As of March 2014, it consists of approximately 50 drugs approved by the FDA, approximately half of which are directed against HIV. Antiviral drug creation strategies are focused on two different approaches: targeting the viruses themselves or targeting host cell factors.

Direct virus-targeting antiviral drugs include attachment inhibitors, entry inhibitors, uncoating inhibitors, protease inhibitors, polymerase inhibitors, nucleoside and nucleotide reverse transcriptase inhibitors, nonnucleoside reverse-transcriptase inhibitors, and integrase inhibitors.

Protease inhibitors (darunavir, atazanavir, and ritonavir), viral DNA polymerase inhibitors (acyclovir, valacyclovir, valganciclovir, and tenofovir), and an integrase inhibitor (raltegravir) are included in the list of Top 200 Drugs by sales for the 2010s.

Darunavir/cobicistat for the treatment of HIV-1: a new era for compact drugs with high genetic barrier to resistance

INTRODUCTION

Cobicistat-boosted darunavir is a boosted protease inhibitor in a fixed-dose combination to be approved for the treatment of human immunodeficiency virus type1 infection. It contains darunavir, a well-known protease inhibitor with a good efficacy and safety profile, and the new pharmacokinetic enhancer cobicistat. The convenience of this combination in a single pill makes this compound easier to take, thus improving adherence.

AREAS COVERED

PubMed and www.clinicaltrials.gov were searched with the term "darunavir/cobicistat" for all clinical trials conducted up to date, as well as for those ongoing and to be opened in the near future as well as for pharmacology data. A review of abstracts from major infectious diseases (particularly those dedicated to human immunodeficiency disease) and pharmacology conferences from 2010 to 2015 was also conducted.

EXPERT OPINION

improving adherence, particularly by minimizing pill burden with convenient formulations (i.e., fixed-dose combination), is one of the major objectives of modern antiretroviral treatment of patients with human immunodeficiency virus disease. Cobicistat is an alternative agent to ritonavir for boosting plasma drug levels for several antiretrovirals. Darunavir co-administered with low-dose ritonavir, in combination with other antiretrovirals, is recommended in several guidelines for treatment of patients with human immunodeficiency disease. Darunavir/cobicistat fixed-dose combination allows for a once-daily treatment regimen with a reduced pill burden. This new co formulation makes this compound easier to take, thus improving adherence.

Pharmacokinetics of Once Versus Twice Daily Darunavir in Pregnant HIV-Infected Women

OBJECTIVE

To describe darunavir (DRV) pharmacokinetics with once-and twice-daily dosing during pregnancy and postpartum in HIV-infected women.

DESIGN

Women were enrolled in International Maternal Pediatric Adolescent AIDS Clinical Trials Network Protocol P1026s, a prospective nonblinded study of antiretroviral pharmacokinetics in HIV-infected pregnant women that included separate cohorts receiving DRV/ritonavir dosed at either 800 mg/100 mg once daily or 600 mg/100 mg twice daily.

METHODS

Intensive steady-state 12- or 24-hour pharmacokinetic profiles were performed during the second trimester, third trimester, and postpartum. DRV was measured using high-performance liquid chromatography (detection limit: 0.09 μg/mL).

RESULTS

Pharmacokinetic data were available for 64 women (30 once daily and 34 twice daily dosing). Median DRV area under the concentration-time curve (AUC) and maximum concentration were significantly reduced during pregnancy with both dosing regimens compared with postpartum, whereas the last measurable concentration (Clast) was also reduced during pregnancy with once daily DRV. DRV AUC with once daily dosing was reduced by 38% during the second trimester and by 39% during the third trimester. With twice daily dosing, DRV AUC was reduced by 26% in both trimesters. The median (range) ratio of cord blood/maternal delivery DRV concentration in 32 paired samples was 0.18 (range: 0-0.82).

CONCLUSIONS

DRV exposure is reduced by pregnancy. To achieve DRV plasma concentrations during pregnancy equivalent to those seen in nonpregnant adults, an increased twice daily dose may be necessary. This may be especially important for treatment-experienced women who may have developed antiretroviral resistance mutations.

A critical review of properties of darunavir and analytical methods for its determination

Darunavir is a synthetic non-peptidic protease inhibitor that has been shown to be extremely potent against wild-type HIV, and it is an important component of highly active antiretroviral treatment (HAART), which is considered as one of the most significant advances in the field of HIV therapy. However, there are some concerns about darunavir quality control. Darunavir shows pseudo-polymorphism: in different ambient conditions one pseudo-polymorphic form can change to another. This behavior of darunavir is problematic because the dosage form is exposed to different ambient conditions around the world, since HIV/AIDS is prevalent globally. Issues around differences in the solubility and effects that different forms of darunavir can cause are of concern, and a more stable form is preferable. Important investigations of darunavir such as dissolution behavior, polymorphism, stability and degradation studies, and the impact of that on the quality of the product are being conducted by our working group. A cure for HIV/AIDS remains a long-term commitment, and there is much yet to achieve. This article discusses, by a critical review of the literature, the impact of the use of darunavir in the treatment of HIV-infected patients, its physical-chemical properties, the analytical methods to determine it, and challenges that remain in order to ensure the quality and stability of darunavir.

Plasma concentrations of efavirenz, darunavir/ritonavir and raltegravir in HIV-HCV-coinfected patients without liver cirrhosis in comparison with HIV-monoinfected patients

BACKGROUND

The objective of the study was to assess plasma concentrations of efavirenz, darunavir/ritonavir and raltegravir in patients with human immunodeficiency virus-hepatitis C virus (HIV-HCV)-coinfection without liver cirrhosis.

METHODS

In this observational, open-label study, adult HIV-infected outpatients treated with tenofovir/emtricitabine plus efavirenz (600 mg daily), darunavir/ritonavir (800/100 mg daily) or raltegravir (400 mg twice daily) for at least 4 weeks were asked to participate. Subjects with liver cirrhosis were excluded. The trough concentration (C trough) of darunavir/ritonavir and raltegravir and the mid-dose concentration (C12h) of efavirenz were assessed at steady state by a validated high-performance liquid chromatography (HPLC)-tandem mass spectrometry method.

RESULTS

A total of 96 HIV-positive patients were enrolled into the study. Thirty-four patients were treated with efavirenz, 33 with darunavir/ritonavir and 29 with raltegravir. The geometric mean plasma C trough [coefficient of variation (%)] of darunavir was comparable between HIV+/HCV+ and HIV+/HCV- subjects: 2644 ng/ml (155%) and 2491 ng/ml (139%), respectively (geometric mean ratio (GMR) = 0.81; 95% confidence interval (CI) = 0.79-1.56; p = 0.69). These values were comparable for raltegravir: 108 ng/ml (149%) in the HIV+/HCV+ group and 96 ng/ml (161%) in the HIV+/HCV- group (GMR = 0.84; 95% CI = 0.61-1.44; p = 0.72). On the contrary, the geometric mean plasma C12h of efavirenz was significantly higher among the 15 HIV+/HCV+ patients (1915 ng/ml, 159%) than among the 19 HIV+/HCV- patients (1505 ng/ml, 167%; GMR = 1.41; 95% CI = 1.19-1.71; p = 0.009).

CONCLUSIONS

The mean plasma concentration of efavirenz was significantly higher in HCV-positive than in HCV-negative patients without liver cirrhosis, while the mean plasma levels of darunavir/ritonavir and raltegravir were comparable in both groups.

Stability Study of Darunavir Ethanolate Tablets Applying a New Stability-Indicating HPLC Method

Chemical and physical degradation of drugs may result in altered therapeutic efficacy and even toxic effects. Therefore, the aim of this work was to study the stability of darunavir and to develop and validate a liquid chromatography (LC) method to determine darunavir in raw material and tablets in the presence of degradation products. The novel method showed to be linear from 6.0 to 21.0 μg/mL, with high precision (CV < 2%) and accuracy (recuperation of 99.64%). It is simple and reliable, free of placebo interferences. The robustness of the method was evaluated by a factorial design using seven different parameters. Forced degradation study was done under alkaline, acidic, and oxidative stress at ambient temperature and by heating. The LC method was able to quantify and separate darunavir and its degradation products. Darunavir showed to be unstable under alkaline, acid, and oxidative conditions. The novelty of this study is understanding the factors that affect darunavir ethanolate stability in tablets, which is the first step to unravel the path to know the degradation products. The novel stability-indicating method can be used to monitor the drug and the main degradation products in low concentrations in which there is linearity.