Emtricitabine + tenofovir alafenamide for the treatment of HIV

Study Design Characteristics and Pharmacological Mechanisms in International Clinical Trials Registry Platform: Registered Clinical Trials on Antiviral Drugs for COVID-19

OBJECTIVE

This study aimed to evaluate the pharmacological mechanisms of antiviral drugs against the novel coronavirus disease (COVID-19) and the study designs in clinical trials registered with the International Clinical Trials Registry Platform (ICTRP).

METHODS

Clinical trials involving antiviral drugs for treating COVID-19 were retrieved from the ICTRP database. For each trial, the study design, number of participants, primary endpoints, source register, antiviral mechanism, and results were evaluated.

RESULTS

On June 10, 2020, 145 eligible clinical trials were retrieved from the ICTRP, of which 99 (68.3%) were randomized trials, 109 (75.2%) were parallel assignment trials, 38 (26.2%) were double or single blinded, 130 (89.7%) involved two groups, and 75 (51.6%) included more than 100 participants; and clinical improvement or recovery and virus-negative conversion were the two most common endpoints, accounting for 40.7% and 18.6%, respectively. The drugs were divided according to the antiviral mechanism into HIV reverse transcriptase inhibitors, RNA-dependent RNA polymerase inhibitors, HIV protease inhibitors (PIs), hepatitis C virus NS3 PIs, and anti-influenza drugs.

CONCLUSION

The design characteristics of clinical trials of antiviral drugs for treating COVID-19 as well as the mechanism of action and antiviral efficacy of the drugs were evaluated in this study. The results of these trials could constitute a reference for future clinical trials to be executed on COVID-19 treatment and prevention.

Co-crystals, Salts or Mixtures of Both? The Case of Tenofovir Alafenamide Fumarates

Tenofovir alafenamide fumarate (TAF) is the newest prodrug of tenofovir that constitutes several drug products used for the treatment of HIV/AIDS. Although the solid-state properties of its predecessor tenofovir disoproxil fumarate have been investigated and described in the literature, there are no data in the scientific literature on the solid state properties of TAF. In our report, we describe the preparation of two novel polymorphs II and III of tenofovir alafenamide monofumarate (TA MF2 and TA MF3). The solid-state structure of these compounds was investigated in parallel to the previously known tenofovir alafenamide monofumarate form I (TA MF1) and tenofovir alafenamide hemifumarate (TA HF). Interestingly, the single-crystal X-ray diffraction of TA HF revealed that this derivative exists as a co-crystal form. In addition, we prepared a crystalline tenofovir alafenamide free base (TA) and its hydrochloride salt (TA HCl), which enabled us to determine the structure of TA MF derivatives using ¹⁵N-ssNMR (¹⁵N-solid state nuclear magnetic resonance). Surprisingly, we observed that TA MF1 exists as a mixed ionization state complex or pure salt, while TA MF2 and TA MF3 can be obtained as pure co-crystal forms.

Symtuza® (DRV/c/FTC/TAF) in the management of treatment-naive HIV-patients

The management of HIV infection is based on the administration of lifelong antiretroviral therapy (ART). Single-tablet regimens (STR) reduce pill burden and maximise long-term adherence. Cobicistat-boosted darunavir with emtricitabine and tenofovir alafenamide co-formulation (DRV/c/FTC/TAF), with trade name Symtuza^®, is the first STR based on a protease inhibitor (PI). Symtuza^® exhibits the efficacy, potency and high genetic barrier of DRV/c, positioning it as the drug of choice even in patients at risk of developing resistance mutations, in addition to the good safety profile of TAF and the advantages of an STR. Early ART initiation is also possible as baseline genotype and HLA-B5701 are not needed. It therefore represents a very good regimen for naive patients, in particular those at risk of poor adherence, and those with low potential risk for drug-drug interactions. Supplement information: This article is part of a supplement entitled "Co-formulated cobicistat-boosted darunavir, emtricitabine, and tenofovir alafenamide for the treatment of HIV infection", which is sponsored by Janssen.

Two-drug regimens for treatment of naïve HIV-1 infection and as maintenance therapy

As people live longer with HIV infection, there has been a resurgence of interest in challenging the use of three-drug therapy, including two nucleoside reverse transcriptase inhibitors plus a third drug, as initial treatment of HIV infection or for maintenance therapy in virologically suppressed individuals. Although initial studies showed poor efficacy and/or substantial toxicity, more recent regimens have held greater promise. The SWORD-1 and -2 studies were pivotal trials of dolutegravir plus rilpivirine as maintenance therapy in virologically suppressed patients with no history of drug resistance, leading to the US Food and Drug Administration’s approval of the regimen as a small, single tablet. More recently, the GEMINI-1 and -2 studies demonstrated that dolutegravir plus lamivudine is as safe and effective as the same regimen when combined with tenofovir disoproxil fumarate in treatment-naïve individuals. Together, these and other studies of novel two-drug regimens offer the potential for improved tolerability and simplicity, as well as a reduction in cost. We will review historical and recent trials of two-drug therapy for the treatment of HIV-1 infection.

Efficacy of single-tablet darunavir, cobicistat, emtricitabine, and tenofovir alafenamide in the treatment of HIV-1

INTRODUCTION

HIV eradication is not feasible and lifelong treatment is warranted to manage HIV infection. In this scenario, the advent of single-tablet, once-daily, fixed-dose co-formulations is important for reducing pill burden and maximize long-term drug adherence. Cobicistat-boosted darunavir along with emtricitabine and tenofovir alafenamide co-formulation (DRV/c/FTC/TAF or the trade name Symtuza®) is the first marketed protease inhibitor-based fixed-dose combination regimen for the treatment of HIV infection. It was approved in late 2017 by the European Medical Agency both for naïve patients and treatment-experienced patients with viral suppression. Areas covered: PubMed, ClinicalTrials.gov and presentations at scientific meetings were searched with the terms 'darunavir/cobicistat' and 'tenofovir alafenamide and emtricitabine' for clinical trials either conducted to date or ongoing as well as a review of abstracts from major HIV/AIDS and infectious diseases conferences from 2015 to up to date. Expert opinion: DRV/c/FTC/TAF is a novel unique antiretroviral drug co-formulation that exhibits a convenient dosing, satisfactory safety profile, and high antiviral efficacy, even in patients harboring viruses with resistance to antivirals other than darunavir in the short-midterm. It represents the first fixed-dose combination therapy including a protease inhibitor given as one single pill once daily for drug-naïve patients and as second-line antiretroviral therapy.

Next generation fixed dose combination pharmacotherapies for treating HIV

INTRODUCTION

Treatment options for patients with HIV-1 infection have grown over the past two decades to include multiple fixed-dose combination pharmacotherapies that have greatly simplified administration of antiretroviral therapy (ART) for both patients and providers. Effective virologic control can often be achieved with once-daily use of a single-tablet regimen. Over the past three years, ART drug development has focused on the next generation of fixed-dose combinations for initial and maintenance therapy with improved efficacy, safety and tolerability.

AREAS COVERED

This review covers pre-clinical and clinical data searched through PubMed and presented at major conferences through November 2017.

EXPERT OPINION

Currently available single-tablet regimens have clinical limitations related to adverse event profiles, drug-drug and drug-food interactions and variable barriers to resistance. Anticipated advances in ART fixed-dose combinations promise combinations of current multiple tablet regimens into single tablets, as well as combinations with novel drugs with improved safety and tolerability. The traditional dogma of effective ART containing at least three active antiretroviral drugs is being challenged by promising data to support efficacy of certain regimens containing two drugs. Implementation of next generation ART will bring to light issues of clinical preference and cost-effectiveness as patents of existing drugs expire and more generic formulations become available.

Role of tenofovir alafenamide (TAF) in the treatment and prophylaxis of HIV and HBV infections

Tenofovir (TFV) is the cornerstone of the treatment and prophylaxis of HIV infections. It has been routinely used in its prodrug form TDF (tenofovir disoproxil fumarate) combined with emtricitabine ((-)FTC) and other antiretroviral agents. TDF has now been replaced by TAF (tenofovir alafenamide) which allows better uptake by the lymphoid tissue. In combination with elvitegravir (E), cobicistat (C), emtricitabine (F), TAF can be advocated as an STR (single tablet regimen, Genvoya®) for the treatment of HIV infections. In this combination, E and C may in the future be replaced by bictegravir. The prophylaxis of HIV infection is momentarily based upon Truvada®, the combination of F with TDF, which in the future may also be replaced by TAF. TAF (Vemlidy®) has also replaced TDF (Viread®) for the treatment of hepatitis B virus (HBV) infections. Both TDF and TAF offer little or no risk for virus-drug resistance. As compared to TDF, TAF limits the risk for nephrotoxicity and loss of bone mineral density. What remains to be settled, however, before the universal use of TAF could be recommended, is its safety during pregnancy and its applicability in the treatment of tuberculosis, in combination with rifampicin.

Novel approaches to HIV therapy

There are approximately 35 million people infected by human immunodeficiency virus (HIV), with an estimated 2 million incident infections annually across the globe. While HIV infection was initially associated with high rates of morbidity and mortality, advances in therapy have transformed it into a chronic and manageable disease. In addition, there is very strong evidence that those on antiretroviral therapy are much less likely to transmit infection to their partners. The success rates for maintaining viral suppression in treated patients has dramatically increased owing to the development of agents that are potent and well tolerated and can often be co-formulated into single pills for simplification. This review will outline advances in treatment over the last several years as well as new strategies that may shift the existing treatment paradigm in the near future.