Total and Unbound Bictegravir Concentrations and Viral Suppression in Cerebrospinal Fluid of Human Immunodeficiency Virus-Infected Patients (Spanish HIV/AIDS Research Network, PreEC/RIS 56)

Clinical considerations when switching antiretroviral therapy

INTRODUCTION

Antiretroviral therapy (ART) can be personalized through simple formulations with high resistance barriers, favorable safety profiles, and novel administration routes. Switching treatments has become a key clinical strategy for addressing drug toxicity and interactions and enhancing adherence and convenience. This strategy aims to improve the quality of life and long-term efficacy, even in challenging cases like people living with HIV (PLWH) with multiple comorbidities, prior virological failure, and drug resistance.

AREAS COVERED

The authors reviewed clinical trials and cohort studies providing evidence of benefits and risks of current antiretroviral (ARV) drugs as switching options for PLWH in various scenarios. The literature search included clinical trials, meta-analyses, observational studies, and review articles in English published after 2000, and current HIV treatment guidelines in English and Spanish as of February 2024.

EXPERT OPINION

New ARV drugs offer advantages in efficacy and safety over previous options but may have also adverse effects. Second-generation integrase inhibitors and tenofovir alafenamide show benefits as switching options in various scenarios, though more research is needed on potential weight gain and metabolic issues. Injectable long-acting ART is promising for switching strategies, but finding the optimal combination of new drugs remains challenging.

CNS Viral Infections-What to Consider for Improving Drug Treatment: A Plea for Using Mathematical Modeling Approaches

Neurotropic viruses may cause meningitis, myelitis, encephalitis, or meningoencephalitis. These inflammatory conditions of the central nervous system (CNS) may have serious and devastating consequences if not treated adequately. In this review, we first summarize how neurotropic viruses can enter the CNS by (1) crossing the blood-brain barrier or blood-cerebrospinal fluid barrier; (2) invading the nose via the olfactory route; or (3) invading the peripheral nervous system. Neurotropic viruses may then enter the intracellular space of brain cells via endocytosis and/or membrane fusion. Antiviral drugs are currently used for different viral CNS infections, even though their use and dosing regimens within the CNS, with the exception of acyclovir, are minimally supported by clinical evidence. We therefore provide considerations to optimize drug treatment(s) for these neurotropic viruses. Antiviral drugs should cross the blood-brain barrier/blood cerebrospinal fluid barrier and pass the brain cellular membrane to inhibit these viruses inside the brain cells. Some antiviral drugs may also require intracellular conversion into their active metabolite(s). This illustrates the need to better understand these mechanisms because these processes dictate drug exposure within the CNS that ultimately determine the success of antiviral drugs for CNS infections. Finally, we discuss mathematical model-based approaches for optimizing antiviral treatments. Thereby emphasizing the potential of CNS physiologically based pharmacokinetic models because direct measurement of brain intracellular exposure in living humans faces ethical restrictions. Existing physiologically based pharmacokinetic models combined with in vitro pharmacokinetic/pharmacodynamic information can be used to predict drug exposure and evaluate efficacy of antiviral drugs within the CNS, to ultimately optimize the treatments of CNS viral infections.

Central nervous system disorders after use of dolutegravir: evidence from preclinical and clinical studies

The evaluation of dolutegravir based on available preclinical and clinical studies reveals a risk of central nervous system (CNS) disorders associated with long-term use of the drug. The available literature on the pharmacokinetics of the drug, including its penetration of the blood-brain barrier, was reviewed, as well as clinical trials assessing the incidence of adverse effects in the CNS and the frequency of its discontinuation. This paper also summarizes the impact of factors affecting the occurrence of CNS disorders and indicates the key role of pharmacovigilance in the process of supplementing knowledge on the safety of drugs, especially those that are newly registered.

Human and nonclinical disposition of [14C]bictegravir, a potent integrase strand-transfer inhibitor for the treatment of HIV-1 infection

Bictegravir (BIC) is a potent small-molecule integrase strand-transfer inhibitor (INSTI) and a component of Biktarvy®, a single-tablet combination regimen that is currently approved for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. The absorption, metabolism, distribution, and elimination (ADME) characteristics of BIC were determined through in vivo nonclinical and clinical studies (IND 121318).[¹⁴C]BIC was rapidly absorbed orally in mice, rats, monkeys and human. The cumulative dose recovery was high in nonclinical species (>80%) and humans (95.3%), with most of the excreted dose recovered in faeces. Quantifiable radioactivity with declining concentration was observed in rat tissues suggesting reversible binding. Unchanged BIC was the most abundant circulating component in all species along with two notable metabolites M20 (a sulphate conjugate of hydroxylated BIC) and M15 (a glucuronide conjugate of BIC). BIC was primarily eliminated by hepatic metabolism followed by excretion of the biotransformed products into faeces. In vitro drug-drug interaction (DDI) studies with M15 and M20 demonstrated that no clinically relevant interactions were expected.Overall, BIC is a novel and potent INSTI with a favourable resistance, PK, and ADME profile that provides important improvements over other currently available INSTIs for the treatment of HIV-1.

Cerebrospinal fluid exposure to bictegravir/emtricitabine/tenofovir in HIV-1-infected patients with CNS impairment

OBJECTIVES

The penetration of antiretroviral drugs into deep compartments, such as the CNS, is a crucial component of strategies towards an HIV cure. This study aimed to determine CSF concentrations of bictegravir, emtricitabine and tenofovir in patients with HIV-related CNS impairment (HCI) enrolled in a real-life observational study.

METHODS

Patients with HCI treated by optimized ART, including bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) for at least 1 month were enrolled. Plasma and CSF concentrations were measured by quality control-validated assays (LC-MS/MS). The inhibitory quotient (IQARV) was calculated as the ratio of unbound (bictegravir) or total (emtricitabine and tenofovir) concentration to half (or 90%) maximal inhibitory concentration for bictegravir (or emtricitabine and tenofovir). All numerical variables are expressed as median (range).

RESULTS

Twenty-four patients (nine women) were enrolled. The age was 45 (26-68) years. Unbound bictegravir and total emtricitabine and tenofovir CSF concentrations were 4.4 (1.6-9.6), 84.4 (28.6-337.4) and 1.6 (0.7-4.3) ng/mL, respectively. The unbound bictegravir CSF fraction was 34% (15%-82%) versus 0.33% (0.11%-0.92%) in plasma. Three patients had an IQARV above unity for the three antiretrovirals. Factors positively associated with the CSF concentration (unbound for bictegravir) were age and total plasma concentration for the three antiretrovirals. Patients aged over 51 years had higher CSF concentrations (unbound for bictegravir).

CONCLUSIONS

We observed low CSF exposure to bictegravir, emtricitabine and tenofovir. These results suggest that BIC/FTC/TAF should be used with caution as first-line treatment for people living with HIV with HCI under 51 years of age.

CNS Considerations in ART Simplification Strategies

PURPOSE OF THE REVIEW

This review summarizes current knowledge on central nervous system (CNS) considerations in ART simplification strategies.

RECENT FINDINGS

Antiretroviral therapies (ART) showing efficacy in plasma will usually show efficacy in the cerebrospinal fluid (CSF). ART simplification may virologically fail if the new regimen has less than two active drugs, the genetic barrier of drugs is not high, and the patient may harbour archived resistance. Dual therapies including a boosted protease inhibitor (PI) or dolutegravir (DTG) are generally effective from the CNS perspective. In cases of related neurotoxicity, switching from either efavirenz (EFV) or DTG to another equally effective drug with better CNS tolerability usually leads to complete resolution of CNS symptoms. However, improvement may be incomplete when factors other than ART that cannot be easily modified are involved.

Doravirine Achieves Adequate CSF Exposure and is Mostly Unbound to Proteins

We determined total and unbound concentrations of Doravirine (DOR) in cerebrospinal fluid (CSF) and blood plasma. Total and unbound DOR concentrations in CSF exceeded the EC50 value against wild-type virus (5.1 ng/mL) in all subjects suggesting that DOR may contribute to inhibit viral replication in this compartment.

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.

Characteristics of Dolutegravir and Bictegravir Plasma Protein Binding: a First Approach for the Study of Pharmacologic Sanctuaries

This study aimed to characterize in vitro dolutegravir (DTG) and bictegravir (BIC) binding. They had a preferential binding to human serum albumin (HSA) with two classes of albumin sites. Human alpha-1-acid glycoprotein (HAAG) binding of DTG and BIC showed an atypical nonlinear binding. The low-affinity site on HSA, the main plasma binding protein, suggests that the high protein binding rate should not impair passive diffusion.

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.

No Changes in Human Immunodeficiency Virus (HIV) Suppression and Inflammatory Markers in Cerebrospinal Fluid in Patients Randomly Switched to Dolutegravir Plus Lamivudine (Spanish HIV/AIDS Research Network, PreEC/RIS 62)

A major concern of human immunodeficiency virus (HIV) dual therapy is a potentially lower efficacy in viral reservoirs, especially in the central nervous system (CNS). We evaluated HIV RNA, neuronal injury, and inflammatory biomarkers and dolutegravir (DTG) exposure in cerebrospinal fluid (CSF) in patients switching to DTG plus lamivudine (3TC). All participants maintained viral suppression in plasma and CSF at week 48. We observed no increase in CSF markers of inflammation or neuronal injury. Median (interquartile range) total and unbound DTG in CSF were 7.3 (5.9-8.4) and 1.7 (1.2-1.9) ng/mL, respectively. DTG+3TC may maintain viral control without changes in inflammatory/injury markers within the CNS reservoir.

Dynamics of the decay of HIV RNA and distribution of bictegravir in the genital tract and rectum in antiretroviral-naïve HIV-1-infected adults treated with bictegravir/emtricitabine/tenofovir alafenamide (Spanish HIV/AIDS Research Network, PreEC/RIS 58)

BACKGROUND

The pharmacokinetics of bictegravir and its association with decay of HIV-1 RNA in genital fluids and the rectum have not yet been addressed.

METHODS

Prospective multicenter study of HIV-1-infected, antiretroviral-naive individuals initiating BIC/FTC/TAF. HIV-1 RNA was measured (LOQ 40 copies/mL) in blood plasma (BP), seminal plasma (SP), rectal fluid (RF), and cervicovaginal fluid (CVF) at baseline, at days 3, 7, 14, and 28, and at weeks 12 and 24. Total and protein-unbound bictegravir concentrations were quantified in BP, SP, CVF and rectal tissue (RT) at 24 hours postdose (C24h) on day 28 and week 12 using a validated LC-MS/MS assay.

RESULTS

The study population comprised 15 males and 8 females. In SP, RF, and CVF, baseline HIV-1 RNA was >40 copies/mL in 12/15, 13/15, and 4/8 individuals, with a median of 3.54 (2.41-3.79), 4.19 (2.98-4.70), and 2.56 (1.61-3.56) log10 copies/mL, respectively. The initial decay slope was significantly lower in SP than in RF and BP. Time to undetectable HIV-1 RNA was significantly shorter in SP and RF than in BP. All women achieved undetectable HIV-1 RNA in CVF at day 14.The median total bictegravir concentrations in SP, RT, and CVF were 65.5 (20.1-923) ng/mL, 74.1 (6.0-478.5) ng/g, and 61.6 (14.4-1760.2) ng/mL, representing 2.7%, 2.6%, and 28% of the BP concentration, while protein-unbound fractions were 51.1%, 44.6%, and 42.6%, respectively.

CONCLUSIONS

BIC/FTC/TAF led to rapid decay of HIV-1 RNA in genital and rectal fluids. Protein-unbound bictegravir concentrations in SP, RT, and CVF highly exceeded the EC50 value (1.1 ng/mL).

Measurement of total and unbound bictegravir concentrations in plasma and cerebrospinal fluid by UHPLC-MS/MS

Bictegravir is a novel integrase strand transfer inhibitor, administrated in co-formulation with tenofovir alafenamide and emtricitabine (Biktarvy®), indicated in the management of HIV-1 infection in patients not previously treated with antiretroviral therapy. Bictegravir is highly bound to plasma proteins, and this significantly determines its clearance, solubility, and activity. These characteristics are crucial determinants of bictegravir penetration into human body compartments, as the central nervous system. We developed and validated UHPLC-MS/MS procedures to measure total and unbound bictegravir concentrations in plasma and cerebrospinal fluid. Simple protein precipitation with acetonitrile was implemented to prepare plasma and cerebrospinal fluid samples. Sample preparation was preceded by ultrafiltration for measuring unbound bictegravir concentrations. Chromatographic separations were achieved on an Acquity® UHPLC® BEH^TM (2.1 × 100 mm id, 1.7 μm) reverse-phase C₁₈ column using an isocratic mobile phase 20:80 (v/v) water/acetonitrile with 0.1% formic. Bictegravir and its internal standard (bictegravir-¹⁵N d₂) were detected by electrospray ionization mass spectrometry in positive and multiple reaction monitoring modes, using transitions of 450.2→289.2/145.4 and 453.2→289.2, respectively. Ultrafiltration procedures presented non-specific bindings of (8.6 ± 1.2) % for bictegravir in plasma and (26.6 ± 3.1) % for bictegravir in cerebrospinal fluid. Linearity was observed between (10.70-8560) μg/L, (1.07-856.0) μg/L for total and unbound bictegravir in plasma, and 0.107-26.75 μg/L for total and unbound bictegravir in cerebrospinal fluid. Imprecisions, absolute relative biases, normalized-matrix factors, and normalized-recoveries were ≤14.4%, ≤13.8%, (97.4-102.5) %, and (99.8-105.1) %, respectively. No significant interferences and carry-over were observed. The validated UHPLC-MS/MS procedures could be useful for pharmacokinetic and pharmacodynamic studies.