Therapeutic drug monitoring in human immunodeficiency virus/acquired immunodeficiency syndrome. Quo vadis?

The role of corticosterone in nevirapine-induced idiosyncratic drug-induced liver injury

Nevirapine, an antiretroviral used in the treatment of HIV, is associated with idiosyncratic drug-induced liver injury (IDILI), a potentially life-threatening adverse drug reaction. Its usage has decreased due to this concern, but it is still widely used in lower-resource settings. In general, the mechanisms underlying idiosyncratic drug reactions (IDRs) are poorly understood, but evidence indicates that most are immune-mediated. There is very limited understanding of the early immune response following administration of drugs associated with IDRs, which likely occurs due to reactive metabolite formation. In this work, we aimed to characterize the links between covalent binding of nevirapine, the development of an early immune response, and the subsequent liver injury using a mouse model. We describe initial attempts to characterize an early immune response to nevirapine followed by the discovery that nevirapine induced the release of corticosterone. Corticosterone release was partially associated with the degree of drug covalent binding in the liver but was also likely mediated by additional mechanisms at higher drug doses. Transcriptomic analysis confirmed metabolic activation, glucocorticoid signaling, and decreased immune activation; GDF-15 also warrants further investigation as part of the immune response to nevirapine. Finally, glucocorticoid blockade preceding the first dose of nevirapine attenuated nevirapine-induced liver injury at 3 weeks, suggesting that acute glucocorticoid signaling is harmful in the context of nevirapine-induced liver injury. This work demonstrates that nevirapine induces acute corticosterone release, which contributes to delayed-onset liver injury. It also has implications for screening drug candidates for IDILI risk and preventing nevirapine-induced IDILI.

Induction effect of antiretroviral bictegravir on the expression of Abcb1, Abcg2 and Abcc1 genes associated with P-gp, BCRP and MRP1 transporters present in rat peripheral blood mononuclear cells

BACKGROUND

Antiretrovirals have the potential to cause drug interactions leading to inefficacy or toxicity via induction of efflux transporters through nuclear receptors, altering drug concentrations at their target sites.

RESEARCH DESIGN AND METHODS

This study used molecular dynamic simulations and qRT-PCR to investigate bictegravir's interactions with nuclear receptors PXR and CAR, and its effects on efflux transporters (P-gp, BCRP, MRP1) in rat PBMCs. PBMC/plasma drug concentrations were measured using LC-MS/MS to assess the functional impact of transporter expression.

RESULTS

Bictegravir significantly increased the expression of ABC transporters, with Car identified as a key mediator. This suggests that bictegravir's influence on nuclear receptors could affect drug transport and efficacy at the cellular level.

CONCLUSIONS

Bictegravir activates nuclear receptors enhancing efflux transporter expression. Understanding these interactions is crucial for preventing drug-drug interactions and reducing toxicity in clinical use. Combining CAR antagonists with bictegravir may prevent drug resistance and toxicity. However, these findings are based on preclinical data and necessitate further clinical trials to confirm their applicability in clinical settings.

A Critical Review on Advancement in Analytical Strategies for the Quantification of Clinically Relevant Biological Transporters

Success of a drug discovery program is highly dependent on rapid scientific advancement and periodic inclusion of sensitive and specific analytical techniques. Biological membrane transporters can significantly alter the bioavailability of a molecule in its actual site of action. Expression of transporter proteins responsible for drug transport is extremely low in the biological system. Therefore, proper scientific planning in selection of their quantitative analytical technique is essential. This article discusses critical advancement in the analytical strategies for quantification of clinically relevant biological transporters for the drugs. Article cross-talked key planning and execution strategies concerning analytical quantification of the transporters during drug discovery programs.

The Structure-To-Function Relationships of Gammaherpesvirus-Encoded Long Non-Coding RNAs and Their Contributions to Viral Pathogenesis

Advances in next-generation sequencing have facilitated the discovery of a multitude of long non-coding RNAs (lncRNAs) with pleiotropic functions in cellular processes, disease, and viral pathogenesis. It came as no surprise when viruses were also revealed to transcribe their own lncRNAs. Among them, gammaherpesviruses, one of the three subfamilies of the Herpesviridae, code their largest number. These structurally and functionally intricate non-coding (nc) transcripts modulate cellular and viral gene expression to maintain viral latency or prompt lytic reactivation. These lncRNAs allow for the virus to escape cytosolic surveillance, sequester, and re-localize essential cellular factors and modulate the cell cycle and proliferation. Some viral lncRNAs act as “messenger molecules”, transferring information about viral infection to neighboring cells. This broad range of lncRNA functions is achieved through lncRNA structure-mediated interactions with effector molecules of viral and host origin, including other RNAs, proteins and DNAs. In this review, we discuss examples of gammaherpesvirus-encoded lncRNAs, emphasize their unique structural attributes, and link them to viral life cycle, pathogenesis, and disease progression. We will address their potential as novel targets for drug discovery and propose future directions to explore lncRNA structure and function relationship.

Influence of the cytochrome P450 2B6 genotype on population pharmacokinetics of efavirenz in human immunodeficiency virus patients

A population pharmacokinetic model for efavirenz has been developed from therapeutic drug monitoring data in human immunodeficiency virus (HIV)-positive patients by using a nonlinear mixed-effect model. The efavirenz plasma concentrations (n = 375) of 131 patients were analyzed using high-performance liquid chromatography with UV detection. Pharmacokinetic parameters were estimated according to a one-compartment model. The effects of sex, age, total body weight, height, body mass index, and HIV treatment were analyzed. In a subgroup of 32 patients, genetic polymorphisms of the cytochrome P450 2B6 gene (CYP2B6), CYP3A4, and MDR1 were also investigated. Efavirenz oral clearance and the apparent volume of distribution were 9.50 liters/h and 311 liters, respectively. The model included only the effect of CYP2B6 polymorphisms on efavirenz clearance; this covariate reduced the intersubject variability of clearance by about 27%. Patients showing G/T and T/T CYP2B6 polymorphisms exhibited efavirenz clearances that were about 50% and 75% lower than those observed in the patients without these polymorphisms (G/G). Accordingly, to obtain EFV steady-state concentrations within the therapeutic range (1 to 4 mg/liter), it would be advisable to implement a gradual reduction in dose to 400 or 200 mg/day for patients that are intermediate or poor metabolizers, respectively. However, the remaining interindividual variability observed in the pharmacokinetic parameters of the model highlights the need for dose individualization to avoid inadequate exposure to efavirenz and suggests that these recommended doses be used with caution and confirmed by therapeutic drug monitoring and clinical efficacy. The population model can be implemented in pharmacokinetic clinical software for dosage optimization by using the Bayesian approach.

Application and impact of population pharmacokinetics in the assessment of antiretroviral pharmacotherapy

Population pharmacokinetics has been an important technique used to explore and define relevant sources of variation in drug exposure and response in patient populations. This has been especially true in the area of antiretroviral therapy where the assurance of adequate and sustained drug exposure of multiple agents is highly correlated with therapeutic success. Population pharmacokinetic analyses across the four drug classes and 20 US FDA-approved products used to treat HIV have been published to date. The published reports were predominantly based on actual clinical trials conducted in HIV-infected patients with one or more agents administered. Modelling and simulation approaches have been used in the evaluation of antiretroviral agent outcomes incorporating problematic design and analysis factors such as sparse plasma sampling, data imbalance and censored data. Additional benefits of population modelling approaches applied to the investigation of antiretroviral agents include the ability to assess dosing compliance, understanding and quantifying drug-drug interactions in order to select dosing regimens and the screening of new drug candidates. Pharmacokinetic/pharmacodynamic models have been used to characterise the relationship between drug exposure and virological and immunological response, and to predict clinical outcome. These models offer the best opportunity for individualising and optimising patient therapy, particularly when adjusted for adherence/compliance. The impact of population pharmacokinetics in the area of antiretroviral therapy can be directly assessed by its role in the validation of surrogate markers such as viral RNA load, therapeutic drug monitoring and the management of individual patient outcomes via exposure-toxicity relationships. Each of these population pharmacokinetic outcomes has contributed to the current regulatory environment, specifically in the area of accelerated approval of new antiretroviral agents.

Quantification of antiretroviral drugs in dried blood spot samples by means of liquid chromatography/tandem mass spectrometry

For the first time approved antiretroviral drugs, i.e. protease inhibitors (PI) and non-nucleoside reverse transcriptase inhibitors (NNRTI), were quantified in dried blood spots (DBS) from HIV/AIDS patient whole blood samples as the basis for therapeutic drug monitoring (TDM) by a robust simultaneous liquid chromatography/tandem mass spectrometry (LC/MS/MS) method. This study included seven PI (amprenavir, nelfinavir, indinavir, lopinavir, saquinavir, ritonavir, atazanavir) and two NNRTI (nevirapine, efavirenz). LC/MS/MS coupling was realized using a Phenomenex Synergy Max RP LC column (150 x 2 mm, 4 micro) in combination with a tandem mass spectrometer (API 2000, Applied Biosystems/MDS Sciex Concord) operating in positive and negative multiple reaction monitoring (MRM) mode with reserpine as internal standard. DBS samples were punched out and extracted with 50:50 MeOH/0.2 M ZnSO4 (v/v) as extraction reagent. The method performance data for the drugs in DBS like limits of detection (LOD, 8-70 ng/mL), lower limits of quantification (LLOQ, 41-102 ng/mL), linearity (R2, 0.9981-0.9999), linear concentration ranges (41-10.000 ng/mL), accuracies (92-113%), recoveries (62-94%), and ion suppression were investigated and are comparable to data obtained from human plasma, which is the current standard matrix for TDM of PI and NNRTI. In this case, off-line plasma sample preparation was performed by means of simple protein precipitation with 80:20 methanol/0.2 M ZnSO4 (v/v) as precipitation reagent. Significant correlations between real patient plasma and DBS were obtained for samples containing lopinavir, atazanavir, ritonavir, saquinavir, and efavirenz. DBS preparation as sampling alternative is well suited and practicable for TDM minimizing the high infection risk of HIV/AIDS samples and may facilitate sample mailing.

Photophobia in a patient with high indinavir plasma concentrations

An HIV-infected male patient experienced photophobia after a change in dosing regimen that resulted in substantially higher indinavir plasma levels as compared with a reference population. High indinavir levels were suspected to be the cause of photophobia in this patient.

Therapeutic drug monitoring of antiretroviral therapy

The concept of managing pharmacotherapy based on plasma drug concentrations has been used for decades in a variety of clinical settings. The interest in therapeutic drug monitoring (TDM) of antiretroviral drugs has grown significantly since highly active antiretroviral therapy (HAART) became a standard of care in clinical practice. A primary characteristic of TDM of antiretroviral drugs is that multiple agents are concomitantly used in HAART regimens. Inadequate drug concentrations may lead to evolution of drug resistance mutations and endanger present and future treatment options. A number of clinical trials have demonstrated that drug serum concentrations are an important factor in response to therapy for HIV, but whether TDM will become a tool for the routine management of HIV infection remains to be determined. This review includes an illustrative case report of measuring concentrations of antiretroviral drugs in a pediatric patient.

Clinical use of a simultaneous HPLC assay for indinavir, saquinavir, ritonavir and nelfinavir in children and adults

PROTEASE INHIBITOR TDM: This study examines the importance of therapeutic drug monitoring (TDM) of protease inhibitors (PI) in adults and children infected with the human immunodeficiency virus (HIV). Pediatric patients were included because information in this population is limited. A high performance liquid chromatographic (HPLC) assay measured indinavir, saquinavir, ritonavir and nelfinavir simultaneously in 0.2 mL of plasma. Initially, the reliability, sensitivity and specificity of the assay were verified in stored samples of plasma from adult patients who had been receiving PIs. Non-detectable concentrations (ND) were <25-50 ng/mL. In 96 out of 293 stored samples from adult patients, selected randomly, concentrations of PIs were ND. In a second prospective study of 10 adults (9 mothers and one father, aged 24-42 years) and 15 children (2.9-18 years) ND levels of PI were observed frequently (27% or 4 out of 15 pediatric subjects). In the latter study, drug-drug interactions, dosing errors, noncompliance and other important problems were identified and corrected. Routine monitoring and interpretation of PI concentrations (TDM) may improve the management of adult and pediatric patients infected with HIV, especially in those who fail to respond, develop adverse effects or viral resistance, or lack compliance.

Improved Method for Concurrent Quantification of Antiretrovirals by Liquid Chromatography-Tandem Mass Spectrometry

Therapeutic drug monitoring (TDM) is becoming more widespread to optimize the treatment of patients with HIV/AIDS. The analytic component of TDM requires a drug assay with high specificity, small sample volume requirements, reasonable cost, and rapid turnaround time. This study modified a procedure for the concurrent measurement of 15 antiretrovirals by tandem mass spectrometry. The upper limit of the calibration curves was extended to 10,000 ng/mL, and the matrix for standards was changed from methanol to serum. Also, an additional drug, tenofovir, a nucleotide reverse transcription inhibitor, was included in the revised/improved method. Calibration curves showed good linearity between a concentration range of 100 and 10,000 ng/mL (r > 0.997 for all drugs). Accuracy was assessed by correlation of the calibrators with proficiency testing samples spiked with known drug concentrations and yielded results within 8% of the target values.

Clinical Use of a Simultaneous HPLC Assay for Indinavir, Saquinavir, Ritonavir, and Nelfinavir in Children and Adults

Protease inhibitor (PI) monitoring may improve the care of human immunodeficiency virus (HIV)-infected patients; however, pediatric data are limited. A high-performance liquid chromatographic (HPLC) assay developed for the simultaneous determination of indinavir, ritonavir, saquinavir, and nelfinavir in 0.2 mL of plasma was used to quantify PI concentrations in HIV patients. The reliability, sensitivity, and specificity of the assay were first verified in stored adult samples. Later, blood collected prospectively from patients aged 2.9 to 42 years of age (10 adults aged 24 to 42 and 15 children aged 2.9 to 18 years) was tested. Nondetectable (below 25-50 ng/mL) concentrations (ND) were found in 33% of adult samples and 24% of pediatric samples. Four patients taking from 13.7 to 28 mg/kg/d of ritonavir (mean of 21.3) had concentrations ranging from ND to 11.4 microg/mL, quite different from predicted values. Correctable, important clinical problems including drug-drug interactions, drug administration problems, and confirmed noncompliance were identified and corrected using modern therapeutic drug monitoring (TDM) techniques. Routine PI monitoring and interpretation (TDM) could improve the care of adult and pediatric HIV patients; especially in patients who do not respond as expected to treatment, develop viral resistance or toxicity, and have questionable compliance.