Lopinavir cerebrospinal fluid steady-state trough concentrations in HIV-infected adults

Pharmacology of HIV Cure: Site of Action

Despite significant advances in HIV treatment over the past 30 years, critical barriers to an HIV cure persist. The HIV reservoir, defined at both the cellular and anatomical level, constitutes the main barrier to cure. While the mechanisms underlying the reservoir are not yet well understood, one theory to explain persistence at the anatomical level is that subtherapeutic exposure to antiretroviral therapy (ART) within certain tissue compartments permits ongoing replication. Characterizing ART pharmacology throughout the body is important in the context of these potential pharmacologic sanctuaries and for maximizing the probability of success with forthcoming cure strategies that rely on latency reversal and require ART to prevent reseeding the reservoir. In this review, we provide a comprehensive overview of ART and latency reversal agent distribution at the site of action for HIV cure (i.e., anatomical sites commonly associated with HIV persistence, such as lymphoid organs and the central nervous system). We also discuss methodologic approaches that provide insight into HIV cure pharmacology, including experimental design and advances within the computational, pharmaceutical, and analytical chemistry fields. The information discussed in this review will assist in streamlining the development of investigational cure strategies by providing a roadmap to ensure therapeutic exposure within the site of action for HIV cure.

Pharmacologic approaches to HIV-associated neurocognitive disorders

Antiretroviral therapy in people living with HIV can achieve potent, long-term suppression of HIV plasma viremia and has increased life expectancy. The central nervous system is infected early after virus acquisition and remains a reservoir for HIV. HIV-associated neurocognitive disorders (HAND) are an end-organ manifestation of HIV infection. The need to address neurological complications caused by HAND is significant as approximately 50% of people living with HIV on suppressive antiretroviral therapy are estimated to have some form of HAND. This review discusses the pathophysiology of HAND, CSF/CNS penetration and clinical pharmacology of antiretrovirals including pharmacokinetic/pharmacodynamic relationships, the persistence of HIV in the brain, and future therapeutic approaches to preserve and improve sustained viral suppression in the brain.

CNS penetration of ART in HIV-infected children

Background

Paediatric data on CNS penetration of antiretroviral drugs are scarce.

Objectives

To evaluate CNS penetration of antiretroviral drugs in HIV-infected children and explore associations with neurocognitive function.

Patients and methods

Antiretroviral drug levels were measured in paired CSF and blood samples of clinically stable HIV-infected children between 8 and 18 years old on long-term combined ART. Plasma drug concentrations were corrected for protein binding. We evaluated CNS penetration using CSF/plasma ratios and compared CSF concentrations with the IC50 as a surrogate marker for effectiveness. Blood-brain barrier permeability was assessed for possible confounding. Associations with neurocognitive function were explored using linear regression analysis.

Results

Median CSF/plasma ratios (IQR) were: lopinavir 0.059 (0.024-0.157, n = 7), efavirenz 0.681 (0.555-0.819, n = 12), tenofovir 0.021 (0.020-0.024, n = 4), lamivudine 0.464 (0.331-0.607, n = 17), emtricitabine 0.365 (0.343-0.435, n = 3), nevirapine 1.203 (n = 1), zidovudine 0.718 (0.711-1.227, n = 5) and abacavir 1.344 (0.670-2.450, n = 10). CSF concentrations were below the IC50 for tenofovir (100%), emtricitabine (100%), abacavir (50%) and zidovudine (17%). Lamivudine, lopinavir, efavirenz and nevirapine concentrations were all above the IC50. All participants were virologically suppressed in blood and CSF. CSF drug concentrations were not associated with blood-brain barrier permeability or neurocognitive function.

Conclusions

We showed adequate CSF concentrations of lamivudine, lopinavir, efavirenz and nevirapine, and potential suboptimal CSF concentrations of tenofovir, abacavir and emtricitabine in long-term treated HIV-infected children. None the less, the use of combined antiretroviral drugs led to adequate viral suppression.

Pharmacokinetics and pharmacodynamics of antiretrovirals in the central nervous system

HIV-positive patients may be effectively treated with highly active antiretroviral therapy and such a strategy is associated with striking immune recovery and viral load reduction to very low levels. Despite undeniable results, the central nervous system (CNS) is commonly affected during the course of HIV infection, with neurocognitive disorders being as prevalent as 20-50 % of treated subjects. This review discusses the pathophysiology of CNS infection by HIV and the barriers to efficacious control of such a mechanism, including the available data on compartmental drug penetration and on pharmacokinetic/pharmacodynamic relationships. In the reviewed articles, a high variability in drug transfer to the CNS is highlighted with several mechanisms as well as methodological issues potentially influencing the observed results. Nevirapine and zidovudine showed the highest cerebrospinal fluid (CSF) to plasma ratios, although target concentrations are currently unknown for the CNS. The use of the composite CSF concentration effectiveness score has been associated with better virological outcomes (lower HIV RNA) but has been inconsistently associated with neurocognitive outcomes. These findings support the CNS effectiveness of commonly used highly antiretroviral therapies. The use of antiretroviral drugs with increased CSF penetration and/or effectiveness in treating or preventing neurocognitive disorders however needs to be assessed in well-designed prospective studies.

HIV-associated neurocognitive disorders: perspective on management strategies

Potent combination antiretroviral therapy (ART) has resulted in dramatic improvements in AIDS-associated morbidity and mortality. Although combination ART has resulted in a significant reduction in HIV-associated dementia, the most severe of the HIV-associated neurocognitive disorders (HAND), the overall prevalence of HAND among this population is estimated at 40%. It has been recognized that the central nervous system (CNS) serves as a reservoir for HIV, and neuronal damage begins at the time of acute infection and persists due to chronic infection of microglial and perivascular macrophages. Although combination ART has resulted in virologic control in the plasma compartment, virologic breakthrough can potentially ensue within the CNS compartment due to limited ART drug exposure. The purpose of this review is to discuss the definition, clinical spectrum, and risk factors associated with HAND, review the pathogenesis of HAND, and address the pharmacologic challenges associated with ART drug exposure in the CNS compartment.

Antiretroviral bioanalysis methods of tissues and body biofluids

Research in the many areas of HIV treatment, eradication and prevention has necessitated measurement of antiretroviral (ARV) concentrations in nontraditional specimen types. To determine the knowledgebase of critical details for accurate bioanalysis, a review of the literature was performed and summarized. Bioanalytical assays for 31 ARVs, including metabolites, were identified in 205 publications measuring various tissues and biofluids. 18 and 30% of tissue or biofluid methods, respectively, analyzed more than one specimen type; 35-37% of the tissue or biofluid methods quantitated more than one ARV. 20 and 76% of tissue or biofluid methods, respectively, were used for the analysis of human specimens. HPLC methods with UV detection predominated, but chronologically MS detection began to surpass. 40% of the assays provided complete intra- and inter-assay validation data, but only 9% of publications provided any stability data with even less for the prevalent ARV in treatments.

CSF penetration by antiretroviral drugs

Severe HIV-associated neurocognitive disorders (HAND), such as HIV-associated dementia, and opportunistic CNS infections are now rare complications of HIV infection due to comprehensive highly active antiretroviral therapy (HAART). By contrast, mild to moderate neurocognitive disorders remain prevalent, despite good viral control in peripheral compartments. HIV infection seems to provoke chronic CNS injury that may evade systemic HAART. Penetration of antiretroviral drugs across the blood-brain barrier might be crucial for the treatment of HAND. This review identifies and evaluates the available clinical evidence on CSF penetration properties of antiretroviral drugs, addressing methodological issues and discussing the clinical relevance of drug concentration assessment. Although a substantial number of studies examined CSF concentrations of antiretroviral drugs, there is a need for adequate, well designed trials to provide more valid drug distribution profiles. Neuropsychological benefits and neurotoxicity of potentially CNS-active drugs require further investigation before penetration characteristics will regularly influence therapeutic strategies and outcome.

[Evidence-based therapeutic drug monitoring of lopinavir]

The HIV protease inhibitor lopinavir presents a wide inter-individual variability related to liver and intestinal metabolism involving CYP3A. Published studies were analyzed to establish whether there is evidence that therapeutic drug monitoring of lopinavir could improve patient care. In naïve or pretreated HIV-infected patients, no relationship could be evidenced between virological efficacy and trough lopinavir concentration, most likely because concentrations are above inhibitory concentrations. Although data are limited, patients with elevated triglycerides and cholesterol had trough lopinavir concentrations >8 000 ng/mL. These data suggest that the level of evidence of interest of lopinavir therapeutic drug monitoring is may be recommended in some situations such as children, pregnant women, pretreated patients if the number of mutations is <5, when coadministration with drug with metabolizing enzyme inducing properties is warranted and toxicity.