Pharmacokinetics of Darunavir (TMC114) and Atazanavir during Coadministration in HIV-Negative, Healthy Volunteers

Pharmacokinetics of Etravirine Combined with Atazanavir/Ritonavir and a Nucleoside Reverse Transcriptase Inhibitor in Antiretroviral Treatment-Experienced, HIV-1-Infected Patients

Objectives. TEACH (NCT00896051) was a randomized, open-label, two-arm Phase II trial to investigate the pharmacokinetic interaction between etravirine and atazanavir/ritonavir and safety and efficacy in treatment-experienced, HIV-1-infected patients. Methods. After a two-week lead-in of two nucleoside reverse transcriptase inhibitors (NRTIs) and atazanavir/ritonavir 300/100 mg, 44 patients received etravirine 200 mg bid with one NRTI, plus atazanavir/ritonavir 300/100 mg or 400/100 mg qd (n = 22 each group) over 48 weeks. Results. At steady-state etravirine with atazanavir/ritonavir 300/100 mg qd or 400/100 mg qd decreased atazanavir C min⁡ by 18% and 9%, respectively, with no change in AUC24 h or C max⁡ versus atazanavir/ritonavir 300/100 mg qd alone (Day -1). Etravirine AUC12 h was 24% higher and 16% lower with atazanavir/ritonavir 300/100 or 400/100 mg qd, respectively, versus historical controls. At Week 48, no significant differences were seen between the atazanavir/ritonavir groups in discontinuations due to adverse events (9.1% each group) and other safety parameters, the proportion of patients with viral load <50 copies/mL (intent-to-treat population, noncompleter = failure) (50.0%, atazanavir/ritonavir 300/100 mg qd versus 45.5%, 400/100 mg qd), and virologic failures (31.8% versus 27.3%, resp.). Conclusions. Etravirine 200 mg bid can be combined with atazanavir/ritonavir 300/100 mg qd and an NRTI in HIV-1-infected, treatment-experienced patients without dose adjustment.

Pharmacokinetics and pharmacodynamics of boosted once-daily darunavir

The ability to dose antiretroviral agents once daily simplifies the often complex therapeutic regimens required for the successful treatment of HIV infection. Thus, once-daily dosing can lead to improved patient adherence to medication and, consequently, sustained virological suppression and reduction in the risk of emergence of drug resistance. Several trials have evaluated once-daily darunavir/ritonavir in combination with other antiretrovirals (ARTEMIS and ODIN trials) or as monotherapy (MONET, MONOI and PROTEA trials) in HIV-1-infected adults. Data from ARTEMIS and ODIN demonstrate non-inferiority of once-daily darunavir/ritonavir against a comparator and, together with pharmacokinetic data, have established the suitability of once-daily darunavir/ritonavir for treatment-naive and treatment-experienced patients with no darunavir resistance-associated mutations. The findings of ARTEMIS and ODIN have led to recent updates to treatment guidelines, whereby once-daily darunavir/ritonavir, given with other antiretrovirals, is now a preferred treatment option for antiretroviral-naive adult patients and a simplified treatment option for antiretroviral-experienced adults who have no darunavir resistance-associated mutations. Once-daily dosing with darunavir/ritonavir is an option for treatment-naive and for treatment-experienced paediatric patients with no darunavir resistance-associated mutations based on the findings of the DIONE trial and ARIEL substudy. This article reviews the pharmacokinetics, efficacy, safety and tolerability of once-daily boosted darunavir. The feasibility of darunavir/ritonavir monotherapy as a treatment approach for some patients is also discussed. Finally, data on a fixed-dose combination of 800/150 mg of darunavir/cobicistat once daily are presented, showing comparable darunavir bioavailability to that obtained with 800/100 mg of darunavir/ritonavir once daily.

How individual can personalized antiretroviral treatment be? Deep salvage in an HIV-1-infected patient

We present an HIV-1-infected male (who is now 52 years old) with a multi-drug-resistant virus and discuss the considerations finally leading to an antiretroviral regimen resulting in long-term viral suppression and excellent immunological response in a deep salvage situation. Even in a desperate situation with high-level multi-class resistance, highly individual, personalized antiretroviral regimes can be tailor-made to achieve unexpected improvements in the health status of a patient.

Antiretroviral drug interactions: overview of interactions involving new and investigational agents and the role of therapeutic drug monitoring for management

Antiretrovirals are prone to drug-drug and drug-food interactions that can result in subtherapeutic or supratherapeutic concentrations. Interactions between antiretrovirals and medications for other diseases are common due to shared metabolism through cytochrome P450 (CYP450) and uridine diphosphate glucuronosyltransferase (UGT) enzymes and transport by membrane proteins (e.g., p-glycoprotein, organic anion-transporting polypeptide). The clinical significance of antiretroviral drug interactions is reviewed, with a focus on new and investigational agents. An overview of the mechanistic basis for drug interactions and the effect of individual antiretrovirals on CYP450 and UGT isoforms are provided. Interactions between antiretrovirals and medications for other co-morbidities are summarized. The role of therapeutic drug monitoring in the detection and management of antiretroviral drug interactions is also briefly discussed.

[AIDS Study Group/Spanish AIDS Plan consensus document on antiretroviral therapy in adults with human immunodeficiency virus infection (updated January 2010)]

OBJECTIVE

This consensus document is an update of antiretroviral therapy recommendations for adult patients with human immunodeficiency virus infection.

METHODS

To formulate these recommendations a panel made up of members of the Grupo de Estudio de Sida (Gesida, AIDS Study Group) and the Plan Nacional sobre el Sida (PNS, Spanish AIDS Plan) reviewed the advances in the current understanding of the pathophysiology of human immunodeficiency virus (HIV) infection, the efficacy and safety of clinical trials, and cohort and pharmacokinetic studies published in biomedical journals or presented at scientific meetings. Three levels of evidence were defined according to the data source: randomized studies (level A), cohort or case-control studies (level B), and expert opinion (level C). The decision to recommend, consider or not to recommend ART was established in each situation.

RESULTS

Currently, the treatment of choice for chronic HIV infection is the combination of three drugs of two different classes, including 2 nucleosides or nucleotide analogs (NRTI) plus 1 non-nucleoside (NNRTI) or 1 boosted protease inhibitor (PI/r), but other combinations are possible. Initiation of ART is recommended in patients with symptomatic HIV infection. In asymptomatic patients, initiation of ART is recommended on the basis of CD4 lymphocyte counts, plasma viral load and patient co-morbidities, as follows: 1) therapy should be started in patients with CD4 counts below 350 cells/microl; 2) When CD4 counts are between 350 and 500 cells/microl, therapy should be started in case of cirrhosis, chronic hepatitis C, high cardiovascular risk, HIV nephropathy, HIV viral load above 100,000 copies/ml, proportion of CD4 cells under 14%, and in people aged over 55; 3) Therapy should be deferred when CD4 are above 500 cells/microl, but could be considered if any of previous considerations concurs. Treatment should be initiated in case of hepatitis B requiring treatment and should be considered for reduce sexual transmission. The objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining antiviral response. Therapeutic options are limited after ART failures but undetectable viral loads maybe possible with the new drugs even in highly drug experienced patients. Genotype studies are useful in these situations. Drug toxicity of ART therapy is losing importance as benefits exceed adverse effects. Criteria for antiretroviral treatment in acute infection, pregnancy and post-exposure prophylaxis are mentioned as well as the management of HIV co-infection with hepatitis B or C.

CONCLUSIONS

CD4 cells counts, viral load and patient co-morbidities are the most important reference factors to consider when initiating ART in asymptomatic patients. The large number of available drugs, the increased sensitivity of tests to monitor viral load, and the ability to determine viral resistance is leading to a more individualized therapy approach in order to achieve undetectable viral load under any circumstances.

Darunavir: in treatment-experienced pediatric patients with HIV-1 infection

Darunavir is a nonpeptidic HIV type 1 (HIV-1) protease inhibitor (PI) that binds with high affinity to the HIV-1 protease, including multi-drug resistant proteases. This drug is highly potent against a range of laboratory strains and clinical isolates of wild-type and multidrug-resistant HIV and has limited potential to cause cytotoxicity. Darunavir did not display cross-resistance with other PIs in vitro. The coadministration of a low boosting dose of ritonavir with darunavir (boosted darunavir) increases the bioavailablity of darunavir. The drug is also administered together with other highly active antiretroviral agents. The efficacy of twice-daily boosted darunavir (11-19 mg/kg plus ritonavir 1.5-2.5 mg/kg) in treatment-experienced pediatric patients (aged 6-17 years and weighing > or =20 kg; n = 80) was demonstrated in the phase II DELPHI trial, where a virologic response (HIV-1 RNA reduction from baseline of > or =1 log(10) copies/mL) at week 24 (primary endpoint) was achieved in 74% of patients, and 88% of these patients sustained this level of response at week 48. Boosted darunavir was generally well tolerated in the DELPHI trial, with a similar profile to that observed in adults. The mean triglyceride level at week 48 was lower than that at baseline, and cholesterol levels increased slightly but remained within the normal range.

Pharmacologic characteristics of investigational and recently approved agents for the treatment of HIV

PURPOSE OF REVIEW

Two agents from antiretroviral classes with novel mechanisms of action against HIV received regulatory approval in 2007. Maraviroc is the first in the class of chemokine coreceptor 5 antagonists and raltegravir is the first in the class of integrase inhibitors. There are other compounds in these two new classes in later stages of clinical development, as well as several protease inhibitors and nonnucleoside reverse transcriptase inhibitors that have been recently approved or are under investigation for use in treatment-experienced patients. The purpose of this article is to review the pharmacologic characteristics of these newly approved and investigational antiretroviral drugs, with particular emphasis on data presented or published within the past year.

RECENT FINDINGS

Several pivotal studies describing the efficacy, safety, and pharmacologic properties of maraviroc, vicriviroc, etravirine, rilpivirine, raltegravir, elvitegravir, darunavir/ritonavir, and tipranavir/ritonavir have begun to emerge.

SUMMARY

To date, these agents have demonstrated promising virologic activity with primarily excellent tolerability, but there is still much to learn about their pharmacology. Future studies should evaluate their potential for drug-drug interactions and elucidate their concentration-effect relationships. An appreciation for the pharmacology of these drugs is critical to their optimal use.

Atazanavir: a review of its use in the management of HIV-1 infection

Atazanavir (Reyataz), a protease inhibitor (PI), is approved in many countries for use as a component of antiretroviral therapy (ART) regimens for the treatment of adult, and in some countries in paediatric, patients with HIV-1 infection. ART regimens containing ritonavir-boosted atazanavir improved virological and immunological markers in adult patients with HIV-1 infection, and had similar efficacy to regimens containing lopinavir/ritonavir in treatment-naive and treatment-experienced patients. In addition, unboosted atazanavir was noninferior to ritonavir-boosted atazanavir in treatment-naive patients. Atazanavir is administered once daily and has a low capsule burden. Atazanavir, whether unboosted or boosted, was generally well tolerated and appeared to be associated with less marked metabolic effects, including less alteration of lipid levels, than other PIs. These properties mean that boosted atazanavir, and unboosted atazanavir in patients unable to tolerate ritonavir, continues to have a role as a component of ART regimens in patients with HIV-1 infection.

Managing treatment-experienced pediatric and adolescent HIV patients: role of darunavir

Darunavir is currently the most recently approved HIV-1 protease inhibitor. It is approved for twice-daily dosing with ritonavir in treatment-experienced patients as young as 6 years of age and is available in numerous pill strengths. Emergence of darunavir-specific mutations is generally slow; therefore it can retain activity against viral strains that are resistant to other protease inhibitors, including tipranavir. Darunavir pharmacokinetics, clinical efficacy, resistance mutations and pharmacodynamics, and adverse effects are reviewed here. Substantial data support its use as a potent, well-tolerated option for salvage therapy in highly treatment-experienced children and adolescents.

Ritonavir-boosted darunavir: a powerful option for treatment-experienced HIV-1-infected patients

Darunavir is a HIV protease inhibitor with potent activity in vitro against a broad range of HIV-1 strains and isolates containing multiple protease inhibitor resistance-associated mutations. Its bioavailability increases when co-administered with low-dose ritonavir, or if taken with a meal. Darunavir (in combination with ritonavir) has been approved for treatment of antiretroviral drug-experienced patients with limited therapeutic options. Clinical trials demonstrated significant efficacy with darunavir/ritonavir 600/100 mg twice daily plus optimized background regimens, with sustained response after 48 weeks and no major safety and tolerability concerns. Clinical trials assessing its efficacy in earlier treatment failure have been favorable, however, its role in the treatment of naive patients has not yet been defined.

Decrease of atazanavir and lopinavir plasma concentrations in a boosted double human immunodeficiency virus protease inhibitor salvage regimen

The human immunodeficiency virus protease inhibitor combination of atazanavir (ATV)-lopinavir-ritonavir was reported to exhibit a mutual pharmacoenhancement of plasma lopinavir and ATV concentrations which may be beneficial for salvage patients. We identified 17 patients in our pharmacokinetic database taking this combination and found conflicting results. Plasma concentrations of both ATV and lopinavir were modestly, although not significantly, decreased when the drugs were coadministered. Therefore, patients should be selected carefully for this regimen and frequent clinical and therapeutic drug monitoring is strongly advised.

New therapeutic agents in the management of HIV: an overview of darunavir for clinicians

This overview will provide the reader with summarised information about darunavir, a new protease inhibitor licenced for the treatment of drug resistant HIV-infection. Darunavir is a promising new drug with good clinical efficacy data and safety profile. In this overview clinicians will be updated on clinical efficacy data, side-effects, resistance profile and drug interactions. The overview should give clinicians a sound understanding of when and how to use this new protease inhibitor in the treatment of HIV-infection.

Darunavir: Pharmacokinetics and Drug Interactions

Darunavir (TMC114) is a new HIV protease inhibitor that has demonstrated substantial antiretroviral activity against wild-type HIV-1 virus and multidrug-resistant strains. Darunavir inhibits and is primarily metabolized by cytochrome P450 3A (CYP3A) isoenzymes and is coadministered with low-dose ritonavir (darunavir/r); ritonavir is an inhibitor of CYP3A isoenzymes and pharmacologically enhances darunavir, resulting in increased plasma concentrations and allowing for a lower daily dose. The t1/2 (terminal elimination half-life) of darunavir is 15 h in the presence of ritonavir. An extensive darunavir/r drug-drug interaction programme has been undertaken, covering a wide range of therapeutic areas. Studies conducted in HIV-negative healthy volunteers and in HIV-infected patients show that the potential for interactions is well characterized and the interactions are manageable. For most drugs investigated, no dose adjustments of darunavir/r or the co-administered drug are required. This article reviews all the pharmacokinetic and drug-drug interaction studies conducted to date for darunavir/r, providing guidance on how to co-administer darunavir/r with many other antiretroviral or non-antiretroviral medications commonly used in HIV-infected individuals.