epoxyfarnesyl-diazoacetate and HIV-Infections

To summarize recent updates on the potential role of islatravir for HIV treatment and prevention.. Islatravir is an investigational antiretroviral agent with unique pharmacologic properties that facilitate flexible dosing regimens. Islatravir has demonstrated potent antiviral activity and a high barrier to resistance when combined with doravirine and lamivudine. A simplified two-drug HIV treatment regimen of islatravir combined with doravirine has also demonstrated comparable efficacy to standard of care three-drug regimens. The long half-life and high potency of islatravir's active metabolite may support its use as a long-acting option for HIV preexposure prophylaxis (PrEP). A once monthly oral dose of islatravir maintains effective concentrations of its active metabolite over the entire dosing interval. Furthermore, an investigational implantable formulation has been projected to provide efficacious concentrations for at least a year and exhibits comparable distribution into vaginal and rectal tissues making it a promising PrEP option for male and female individuals. Islatravir has minimal risks of drug interactions as it is not a substrate, inducer, or inhibitor of major drug metabolizers and transporters. Finally, clinical trials demonstrate islatravir's favorable safety profile revealing only mild and transient adverse events.. Leveraging the unique pharmacological properties of islatravir offers opportunities for simplified HIV treatment regimens and long-acting PrEP making it a valuable addition to the antiretroviral arsenal.

Topics: Anti-HIV Agents; Deoxyadenosines; Female; HIV Infections; HIV-1; Humans; Male; Pre-Exposure Prophylaxis

Long-acting and extended-release formulations represent one of the most important approaches to improving the treatment and prevention of chronic HIV infection. Long-acting small molecules and monoclonal antibodies have demonstrated potent anti-HIV activity in early- and late-stage clinical trials. Strategies to manage toxicity and falling drug concentrations after missed doses, as well as primary and secondary resistance to current drugs and monoclonal antibodies are important considerations. Long-acting injectable nanoformulations of the integrase inhibitor cabotegravir and the non-nucleoside reverse transcriptase inhibitor rilpivirine were safe, well tolerated and efficacious in large randomised phase 3 studies. Regulatory approval for this two-drug combination for HIV maintenance therapy was granted in Canada in 2020 and is expected in the USA during 2021. 4'-Ethynyl-2-fluoro-2'-deoxyadenosine (islatravir) is a novel nucleoside reverse transcriptase inhibitor in clinical development as a long-acting oral drug and as a long-acting subcutaneous polymer implant. GS-6207 is a novel HIV capsid inhibitor that is injected subcutaneously every 3 months. Broadly-neutralising monoclonal antibodies have potent antiviral activity in early human trials, however there is substantial baseline resistance and rapid development of resistance to these antibodies if used as monotherapy. Limitations of these antiretroviral approaches include management of toxicities and prevention of drug resistance when these drugs are discontinued and drug concentrations are slowly reduced over time. These approaches appear to be especially attractive for patients complaining of pill fatigue and for those experiencing HIV-associated stigma. As these formulations are shown to be safe, well tolerated and economical, they are likely to gain broader appeal.

Topics: Anti-HIV Agents; Canada; Delayed-Action Preparations; Deoxyadenosines; Drug Combinations; Drug Delivery Systems; HIV Antibodies; HIV Infections; HIV-1; Humans; Pyridones; Rilpivirine

To discuss the potential role of islatravir (ISL), a novel reverse transcriptase translocation inhibitor, in the treatment and prevention of human immunodeficiency virus type 1 (HIV-1) infection.. Islatravir (4'-ethynyl-2-fluoro-2'-deoxyadenosine, MK-8591) is a long-acting first-in-class nucleoside reverse transcriptase translocation inhibitor with the potential for versatile dosing routes and dosing intervals. It demonstrated robust antiviral activity when dosed once daily and once weekly in HIV-1-infected individuals and SIV-infected rhesus macaques. In clinical trials of ISL in combination with doravirine and lamivudine, daily oral administration resulted in high levels of virologic suppression in HIV-infected individuals. In preclinical studies, ISL dosed orally once-weekly as preexposure prophylaxis (PrEP), protected rhesus macaques against SHIV infection via the mucosal route in the low-dose rectal challenge model. Most recently, data in healthy HIV-1-uninfected individuals demonstrated the feasibility of formulating of ISL as an implant. In these studies, levels of intracellular ISL-triphosphate were consistent with the potential for a once-yearly implantable administration of ISL as PrEP.. Islatravir is a promising new agent for both the treatment and prevention of HIV-1 infection.

Topics: Animals; Anti-HIV Agents; Deoxyadenosines; Drug Combinations; Drug Evaluation, Preclinical; HIV Infections; HIV-1; Humans; Lamivudine; Macaca mulatta; Pre-Exposure Prophylaxis; Pyridones; Reverse Transcriptase Inhibitors; Simian Acquired Immunodeficiency Syndrome; Simian Immunodeficiency Virus; Triazoles; Viral Load

Combination antiretroviral therapy (cART) has had dramatic effects on morbidity and mortality for persons living with HIV (PLWH). Despite significant progress in treatment efficacy, tolerability, and reducing pill burden, new agents are needed to address issues of resistance, drug-drug interactions, end organ disease, and adherence. This review covers novel ART agents recently approved or in development.. Capsid inhibitors (CAI) demonstrate high potency and potential for extended-duration dosing in pre-clinical trials. While previous maturation inhibitors (MI) were hampered by issues of drug resistance, a recent phase IIa trial for a second-generation MI demonstrated promising antiviral activity. A phase I trial to evaluate a transdermal implant of islatravir, a nucleoside reverse transcriptase translocation inhibitor (NRTTI), maintained concentrations above the target pharmacokinetic threshold at 12 weeks. The attachment inhibitor fostemsavir is available in the USA for compassionate use in multi-drug-resistant (MDR) HIV. New antiretroviral agents show promise for both extended-duration dosing and MDR HIV.

Topics: Anti-HIV Agents; Capsid; Capsid Proteins; Deoxyadenosines; Drug Discovery; Drug Therapy, Combination; HIV Fusion Inhibitors; HIV Infections; Humans; Organophosphates; Piperazines; Reverse Transcriptase Inhibitors

Pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate and emtricitabine was adopted by WHO as a strategy to reduce HIV incidence. Although shown to be highly effective in reducing HIV acquisition, the protective efficacy of oral tenofovir disoproxil fumarate and emtricitabine relies on optimal adherence, which poses a challenge for a key portion of the most at-risk populations (women, young individuals [15-24 years], racial and ethnic minority men who have sex with men, and transgender women). New PrEP agents in clinical development include novel oral agents (eg, tenofovir alafenamide and islatravir [also known as MK-8591]), long-acting injectables (eg, cabotegravir), vaginal rings, broadly neutralising monoclonal antibodies, topical products (including gels, films, and enemas), and multipurpose technologies. In addition, new drug delivery systems, such as implants and transdermal devices, are promising strategies that are being developed for HIV prevention. The ultimate goal of this new PrEP research agenda is to expand the available PrEP regimens and offer preventive technologies that will appeal to a wide variety of individuals with different needs over the course of their sexually active lifespan.

Topics: Adenine; Administration, Cutaneous; Administration, Oral; Alanine; Contraceptive Devices, Female; Delayed-Action Preparations; Deoxyadenosines; Emtricitabine; Female; HIV Infections; Humans; Incidence; Male; Medication Adherence; Pre-Exposure Prophylaxis; Tenofovir

4'-Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) is a nucleoside reverse transcriptase inhibitor (NRTI) with a novel mechanism of action, unique structure, and amongst NRTIs, unparalleled anti-HIV-1 activity. We will summarize its structure and function, antiviral activity, resistance profile, and potential as an antiretroviral for use in the treatment and preexposure prophylaxis of HIV-1 infection.. EFdA is active against wild-type (EC50 as low as 50 pmol/l) and most highly NRTI-resistant viruses. The active metabolite, EFdA-triphosphate, has been shown to have a prolonged intracellular half-life in human and rhesus (Rh) blood cells. As a result, single drug doses tested in simian immunodeficiency virus mac251-infected Rh macaques and HIV-1-infected individuals exhibited robust antiviral activity of 7-10 days duration. Preclinical studies of EFdA as preexposure prophylaxis in the Rh macaque/simian/human immunodeficiency virus low-dose intrarectal challenge model have shown complete protection when given in clinically relevant doses.. EFdA is a novel antiretroviral with activity against both wild-type and NRTI-resistant viruses. As a result of the prolonged intracellular half-life of its active moiety, it is amenable to flexibility in dosing of at least daily to weekly and perhaps longer.

Topics: Animals; Anti-HIV Agents; Deoxyadenosines; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Reverse Transcriptase Inhibitors

Poor adherence to oral antiretroviral treatment in a subpopulation of persons with HIV-1 infection interferes with the potential success of the drug regimens in treating the infection. Here, we review long-acting antiretroviral strategies currently in clinical development that could prove useful for the treatment of HIV-1 infection in individuals not succeeding with short-acting oral regimens.. Pharmaceutical nanotechnology has succeeded in creating two novel long-acting injectable antiretroviral compounds, carbotegravir and rilpivirine, which have completed early clinical trials demonstrating the safety, tolerability and prolonged antiretroviral activity. 4'-Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA; MK8591) is a novel nucleoside reverse transcriptase inhibitor in early clinical development as a long-acting orally administered drug and in a long-acting polymer implant. Broadly neutralizing and cell-entry inhibitor monoclonal antibodies have demonstrated potent antiviral activity in early human trials; however, there is substantial baseline resistance. In addition, monotherapy leads to rapid resistance in those with baseline susceptibility.. Long-acting antiretroviral chemical compounds and monoclonal antibodies have demonstrated potent anti-HIV activity in the early-stage clinical investigations, and are actively being studied in advanced clinical trials for treatment and prevention. Strategies to manage toxicities and waning drug levels of chemical compounds, as well as primary and secondary resistance to current monoclonal antibodies are important considerations.

Topics: Anti-Retroviral Agents; Delayed-Action Preparations; Deoxyadenosines; HIV Infections; HIV-1; Humans; Injections; Nanoparticles; Reverse Transcriptase Inhibitors

Islatravir (MK-8591) is a deoxyadenosine analog in development for the treatment and prevention of HIV-1 infection. An islatravir-eluting implant could provide an additional option for pre-exposure prophylaxis (PrEP).. Previous data support a threshold islatravir triphosphate concentration for PrEP of 0.05 pmol/10 6 cells in peripheral blood mononuclear cells. Prototype islatravir-eluting implants were previously studied to establish general tolerability and pharmacokinetics (PKs) of islatravir relative to the threshold level.. In this randomized, double-blind, placebo-controlled, phase 1 trial, a next-generation radiopaque islatravir-eluting implant (48 mg, 52 mg, or 56 mg) or placebo implant was placed for a duration of 12 weeks in participants at low risk of HIV infection. Safety and tolerability, as well as PK for islatravir parent and islatravir triphosphate from plasma and peripheral blood mononuclear cells, were assessed throughout placement and 8 weeks after removal.. In total, 36 participants (8 active and 4 placebo per dose arm) were enrolled and completed this study. Implants were generally well tolerated, with no discontinuations due to an adverse event, and no clear dose-dependence in implant-related adverse events. No clinically meaningful relationships were observed for changes in laboratory values, vital signs, or electrocardiogram assessments. Mean islatravir triphosphate levels at day 85 (0.101-0.561 pmol/10 6  cells) were above the PK threshold for all dose levels.. Islatravir administered using a subdermal implant has the potential to be an effective and well-tolerated method for administering PrEP to individuals at risk of acquiring HIV-1.

Topics: Deoxyadenosines; Double-Blind Method; HIV Infections; HIV-1; Humans; Leukocytes, Mononuclear; Pre-Exposure Prophylaxis

Islatravir (MK-8591) is a nucleoside reverse transcriptase translocation inhibitor in development for treatment and prevention of HIV-1. We present efficacy and safety data for islatravir and doravirine (DOR) through 96 weeks of the phase 2b trial (NCT03272347).. In this randomized, double-blind, dose-ranging trial, participants initially received islatravir (0.25, 0.75, or 2.25 mg) with doravirine (100 mg) and lamivudine (3TC, 300 mg) or a fixed-dose combination of doravirine, 3TC, and tenofovir disoproxil fumarate (DOR/3TC/TDF) daily. Beginning at week 24, participants receiving islatravir stopped 3TC if HIV-1 RNA from the prior visit was <50 copies per milliliter and continued taking the assigned islatravir dose (still blinded) with doravirine. All islatravir groups transitioned to open-label use of 0.75 mg between weeks 60 and 84. Efficacy end points at week 96 included the proportion of participants maintaining HIV-1 RNA of <50 copies per milliliter (FDA Snapshot). Safety was assessed by adverse event (AE) reporting.. One hundred twenty-one treatment-naive participants received the study drugs and were included in the analyses. Through week 96, HIV-1 RNA<50 copies per milliliter was maintained in 86.2% (25/29), 90.0% (27/30), and 67.7% (21/31) of participants in the 0.25-, 0.75-, and 2.25-mg islatravir groups, respectively, 81.1% (73/90) of the combined islatravir group, and 80.6% (25/31) of the DOR/3TC/TDF group. One participant in the 2.25-mg islatravir group had Protocol-Defined Virologic Failure after week 48. Drug-related AE rates were higher for DOR/3TC/TDF participants (22.6%) compared with islatravir (combined 7.8%). Two participants (2.2%) receiving islatravir with doravirine and one (3.2%) receiving DOR/3TC/TDF discontinued because of an AE.. Treatment regimens containing islatravir and doravirine maintained viral suppression through week 96 and were well tolerated regardless of dose.

Topics: Adult; Anti-HIV Agents; Deoxyadenosines; Drug Combinations; HIV Infections; HIV-1; Humans; Lamivudine; Pyridones; Reverse Transcriptase Inhibitors; RNA; Tenofovir; Triazoles

Islatravir (MK-8591) is a highly potent type 1 human immunodeficiency virus (HIV-1) nucleoside reverse transcriptase translocation inhibitor with a long intracellular half-life that is in development for the prevention and treatment of HIV-1. We conducted a randomized, double-blind, placebo-controlled, phase 1 trial in adults without HIV-1 infection. Participants received islatravir or placebo subdermal implants for 12 weeks and were monitored throughout this period and after implant removal. The co-primary end points were safety and tolerability of the islatravir implant and pharmacokinetics, including concentration at day 85, of islatravir triphosphate in peripheral blood mononuclear cells (PBMCs). Secondary end points included additional pharmacokinetic parameters for islatravir triphosphate in PBMCs and the plasma pharmacokinetic profile of islatravir. Based on preclinical data, two doses were assessed: 54 mg (n = 8, two placebo) and 62 mg (n = 8, two placebo). The most frequently reported adverse events were mild-to-moderate implant-site reactions (induration, hematoma, pain). Throughout the 12-week trial, geometric mean islatravir triphosphate concentrations were above a pharmacokinetic threshold of 0.05 pmol per 10

Topics: Adult; Anti-HIV Agents; Deoxyadenosines; Double-Blind Method; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Leukocytes, Mononuclear; Male; Middle Aged; Placebos; Reverse Transcriptase Inhibitors; Virus Replication

Hormonal contraceptives are among the most effective forms of reversible contraception, but many other compounds, including some antiretrovirals, have clinically meaningful drug-drug interactions (DDIs) with hormonal contraceptives. Islatravir is a novel human immunodeficiency virus nucleoside reverse transcriptase translocation inhibitor currently in clinical development for treatment and prevention of HIV infection. A phase 1 clinical trial was conducted to evaluate the DDI of islatravir and the combination of oral contraceptive levonorgestrel (LNG)/ethinyl estradiol (EE).. This was an open-label, two-period, fixed-sequence, DDI clinical trial in healthy, postmenopausal or bilaterally oophorectomized females aged 18 through 65 years in the United States between October 2016 and January 2017. A single dose of LNG 0.15 mg/EE 0.03 mg was given followed by a 7-day washout. Islatravir, 20 mg, was then dosed once weekly for 3 weeks; a single dose of LNG 0.15 mg/EE 0.03 mg was given concomitantly with the third dose of islatravir. Pharmacokinetic samples for plasma LNG and EE concentrations were collected pre-dose and up to 120 hours post-dose in each period. Safety and tolerability were assessed throughout the trial by clinical assessments, laboratory evaluations and examination of adverse events.. Fourteen participants were enrolled. The pharmacokinetics of LNG and EE were not meaningfully altered by co-administration with islatravir. For the comparison of (islatravir + LNG/EE)/(LNG/EE alone), the geometric mean ratios (GMRs) (90% confidence intervals [CIs]) for LNG AUC. The results of this trial support the use of LNG/EE contraceptives in combination with islatravir without dose adjustment.

Topics: Adult; Contraception; Contraceptives, Oral, Combined; Deoxyadenosines; Drug Interactions; Ethinyl Estradiol; Female; HIV Infections; Humans; Levonorgestrel

Islatravir is a nucleoside reverse transcriptase translocation inhibitor in development for the treatment and prevention of HIV-1 infection. We aimed to assess the efficacy and safety of islatravir-based regimens for the treatment of HIV-1.. We did a phase 2b, randomised, double-blind, comparator-controlled, dose-ranging trial at 24 clinics or hospitals in four countries (Chile, France, the UK, and the USA). Treatment-naive adults (≥18 years) with plasma HIV-1 RNA concentrations of at least 1000 copies per mL, CD4 T-cell counts of at least 200 cells per mL, and a calculated creatinine clearance of at least 50 mL/min (all within 60 days before study treatment) were eligible for inclusion. Participants were randomly assigned (1:1:1:1) with a block size of four via an interactive voice and web response system to receive oral treatment with one of three doses of islatravir (0·25 mg, 0·75 mg, or 2·25 mg) plus doravirine (100 mg) and lamivudine (300 mg) or to doravirine (100 mg) plus lamivudine (300 mg) plus tenofovir disoproxil fumarate (TDF; 300 mg) once daily with placebo (part 1). Treatment groups were stratified according to screening HIV-1 RNA concentration (≤100 000 copies per mL or >100 000 copies per mL). After at least 24 weeks of treatment, participants taking islatravir who achieved an HIV-1 RNA concentration lower than 50 copies per mL switched to a two-drug regimen of islatravir and doravirine (part 2). All participants and study investigators were masked to treatment in part 1; in part 2, the islatravir dose was masked to all participants and investigators, but the other drugs were given open label. The primary efficacy outcomes were the proportions of participants with an HIV-1 RNA concentration lower than 50 copies per mL at weeks 24 and 48 (US Food and Drug Administration snapshot approach). The primary safety outcomes were the number of participants experiencing adverse events and the number of participants discontinuing study drug owing to adverse events. All participants who received at least one dose of any study drug were included in the analyses. This trial is ongoing, but closed to enrolment of new participants; herein, we report study findings through 48 weeks of treatment. This trial is registered with ClinicalTrials.gov, NCT03272347.. Between Nov 27, 2017, and April 25, 2019, 121 participants (mean age 31 years [SD 10·9], 112 [93%] male, 92 [76%] white, 27 [22%] with HIV-1 RNA concentration >100 000 copies per mL) were randomly assigned: 29 to the 0·25 mg, 30 to the 0·75 mg, and 31 to the 2·25 mg islatravir groups, and 31 to the doravirine, lamivudine, and TDF group. At week 24, 26 (90%) of 29 participants in the 0·25 mg islatravir group, 30 (100%) of 30 in the 0·75 mg islatravir group, and 27 (87%) of 31 in the 2·25 mg islatravir group achieved HIV-1 RNA concentrations lower than 50 copies per mL compared with 27 (87%) of 31 in the doravirine plus lamivudine plus TDF group (difference 2·8%, 95% CI -14·9 to 20·4, for the 0·25 mg islatravir group; 12·9%, -1·6 to 27·5, for the 0·75 mg islatravir group; and 0·3%, -17·9 to 18·5, for the 2·25 mg islatravir group). At week 48, these data were 26 (90%) of 29 in the 0·25 mg islatravir group, 27 (90%) of 30 in the 0·75 mg islatravir group, and 24 (77%) of 31 in the 2·25 mg islatravir group compared with 26 (84%) of 31 in the doravirine plus lamivudine plus TDF group (difference 6·1%, 95% CI -12·4 to 24·4, for the 0·25 mg islatravir group; 6·2%, -12·2 to 24·6, for the 0·75 mg islatravir group; and -6·1%, -27·1 to 14·8, for the 2·75 mg islatravir group). 66 (73%) of participants in the islatravir groups combined and 24 (77%) of those in the doravirine plus lamivudine plus TDF group reported at least one adverse event. Two participants in the 2·25 mg islatravir group and one participant in the doravirine plus lamivudine plus TDF group discontinued owing to an adverse event. No deaths were reported up to week 48.. Treatment regimens containing islatravir and doravirine showed antiviral efficacy and were well tolerated regardless of dose. Doravirine in combination with islatravir has the potential to be a potent two-drug regimen that warrants further clinical development.. Merck, Sharp, & Dohme Corp, a subsidiary of Merck & Co., Inc.

Topics: Adult; Anti-HIV Agents; Deoxyadenosines; Drug Dosage Calculations; Drug Therapy, Combination; Female; HIV Infections; HIV-1; Humans; Lamivudine; Male; Pyridones; Triazoles; Young Adult

Islatravir (also known as ISL and MK-8591) is a unique nucleoside reverse transcriptase translocation inhibitor in clinical development for treatment of people with HIV-1 infection. In preclinical studies, intracellular islatravir-triphosphate exhibits a long half-life and prolonged virological effects. In this study, we aimed to assess islatravir safety, pharmacokinetics, and antiretroviral activity in treatment-naive adults with HIV-1 infection.. This open-label, consecutive-panel, phase 1b trial was done at Charité Research Organisation (Berlin, Germany) and included men and women (aged 18-60 years, inclusive) with HIV-1 infection who were ART naive. Participants were required to have plasma HIV-1 RNA counts of at least 10 000 copies per mL within 30 days before the trial treatment phase, without evidence of resistance to nucleoside reverse transcriptase inhibitors. Participants were enrolled in one of five consecutive dosing panels, receiving a single oral dose of islatravir (0·5-30 mg). The primary outcomes were safety and tolerability of islatravir and change from baseline in HIV-1 plasma RNA; secondary outcomes were islatravir plasma and islatravir-triphosphate intracellular pharmacokinetics. We obtained descriptive safety and pharmacokinetics statistics, and estimated efficacy results from a longitudinal data analysis model. This study is registered with ClinicalTrials.gov, NCT02217904, and EudraCT, 2014-002192-28.. Between Sept 17, 2015, and May 11, 2017, we enrolled 30 participants (six per panel). Islatravir was generally well tolerated. 27 (90%) participants had 60 adverse events after receipt of drug, of which 21 (35%) were deemed to be drug related. The most common (n>1) drug-related adverse events were headache (in nine [30%] participants) and diarrhoea (in two [7%]). No serious adverse events were reported, and no participants discontinued due to an adverse event. Plasma islatravir pharmacokinetics and intracellular islatravir-triphosphate pharmacokinetics were approximately dose proportional. The islatravir-triphosphate intracellular half-life was 78·5-128·0 h. Least-squares mean HIV-1 RNA at 7 days after dose decreased from 1·67 log. Single doses of islatravir as low as 0·5 mg significantly suppressed HIV-1 RNA by more than 1·0 log at day 7 in treatment-naive adults with HIV-1 infection and were generally well tolerated, supporting the further development of islatravir as a flexible-dose treatment for individuals with HIV-1 infection.. Merck Sharp & Dohme Corp, a subsidiary of Merck & Co Inc, Kenilworth, NJ, USA.

Topics: Adult; Anti-HIV Agents; Deoxyadenosines; Female; HIV Infections; HIV-1; Humans; Male; Middle Aged; Reverse Transcriptase Inhibitors; Young Adult

Tenofovir disoproxil fumarate (TDF) and islatravir (ISL, 4'-ethynyl-2-fluoro-2'-deoxyadensine, or MK-8591) are highly potent nucleoside reverse transcriptase inhibitors. Resistance to TDF and ISL is conferred by K65R and M184V, respectively. Furthermore, K65R and M184V increase sensitivity to ISL and TDF, respectively. Therefore, these two nucleoside analogs have opposing resistance profiles and could present a high genetic barrier to resistance. To explore resistance to TDF and ISL in combination, we performed passaging experiments with HIV-1 WT, K65R, or M184V in the presence of ISL and TDF. We identified K65R, M184V, and S68G/N mutations. The mutant most resistant to ISL was S68N/M184V, yet it remained susceptible to TDF. To further confirm our cellular findings, we implemented an endogenous reverse transcriptase assay to verify in vitro potency. To better understand the impact of these resistance mutations in the context of global infection, we determined potency of ISL and TDF against HIV subtypes A, B, C, D, and circulating recombinant forms (CRF) 01_AE and 02_AG with and without resistance mutations. In all isolates studied, we found K65R imparted hypersensitivity to ISL whereas M184V conferred resistance. We demonstrated that the S68G polymorphism can enhance fitness of drug-resistant mutants in some genetic backgrounds. Collectively, the data suggest that the opposing resistance profiles of ISL and TDF suggest that a combination of the two drugs could be a promising drug regimen for the treatment of patients infected with any HIV-1 subtype, including those who have failed 3TC/FTC-based therapies.

Topics: Anti-HIV Agents; Drug Resistance, Viral; HIV Infections; HIV-1; Humans; Mutation; Reverse Transcriptase Inhibitors; Tenofovir

Islatravir (4'-ethynyl-2-fluoro-2'-deoxyadenosine; EFdA) is a first-in-class nucleoside reverse transcriptase translocation inhibitor (NRTTI) being investigated for HIV treatment and prevention. EFdA is intracellularly phosphorylated to EFdA-triphosphate (EFdA-tp), a competitive substrate of deoxyadenosine-triphosphate (dATP). Thus, translating safety and efficacy findings from preclinical studies relies on the assumption that EFdA's intracellular pharmacology can be extrapolated across species.. We investigated how EFdA is phosphorylated across animal species commonly used for preclinical models in drug development to identify those that most closely matched humans.. PBMCs were isolated from whole blood of six species (human, rhesus macaque non-human primate (rmNHP), rat, minipig, dog, and rabbit) using Ficoll separation and counted on a haemocytometer by Trypan blue staining. One million live cells were cultured in media supplemented with 10 U/mL human IL-2, 10% FBS and 1% antibiotics and treated with 0, 17, 170, and 1700 nM EFdA (n = 3 replicates per concentration). After 24 h, representative cell counts were derived from untreated control wells (as above), cells were washed in PBS, and lysed with 70:30 methanol:water. EFdA-tp and dATP concentrations were quantified by HPLC-MS/MS and normalized to the representative live cell counts for each species.. When compared to human values, EFdA-tp concentrations for each EFdA treatment concentration were lower in all species (rmNHP 1.5-2.1-fold, rat 4.5-15-fold, minipig 37-71-fold, dog and rabbit >100-fold). Additionally, rmNHP and dog PBMCs exhibited significantly higher (7-10-fold; P < 0.001) dATP when compared with human PBMCs.. Given intracellular pharmacology differences, these preclinical models may be a conservative estimate of EFdA's intracellular pharmacokinetics and efficacy in humans.

Topics: Animals; Anti-HIV Agents; Deoxyadenosines; Dogs; HIV Infections; Macaca mulatta; Models, Biological; Rabbits; Rats; Research Design; Reverse Transcriptase Inhibitors; Species Specificity; Swine; Swine, Miniature; Tandem Mass Spectrometry

Islatravir (ISL) is a nucleoside reverse transcriptase translocation inhibitor (NRTTI) that inhibits human immunodeficiency virus (HIV) reverse transcription by blocking reverse transcriptase (RT) translocation on the primer:template. ISL is being developed for the treatment of HIV-1 infection. To expand our knowledge of viral variants that may confer reduced susceptibility to ISL, resistance selection studies were conducted with wild-type (WT) subtype A, B, and C viruses. RT mutations encoding M184I and M184V were the most frequently observed changes. Selection studies were also initiated with virus containing a single known resistance-associated mutation in RT (K65R, L74I, V90I, M184I, or M184V), and no additional mutations were observed. Antiviral activity assays were performed on variants that emerged in selection studies to determine their impact. M184I and M184V were the only single-codon substitutions that reduced susceptibility >2-fold compared to WT. A114S was an emergent substitution that when combined with other substitutions further reduced susceptibility >2-fold. Viruses containing A114S in combination with M184V did not replicate in primary blood mononuclear cells (PBMCs), consistent with the rare occurrence of the combination in clinical samples. While A114S conferred reduced susceptibility to ISL, it increased susceptibility to approved nucleoside reverse transcriptase inhibitors (NRTIs). This differential impact of A114S on ISL, an NRTTI, compared to NRTIs likely results from the different mechanisms of action. Altogether, the results demonstrate that ISL has a high barrier to resistance and a differentiated mechanism compared to approved NRTIs.

Topics: Anti-HIV Agents; Deoxyadenosines; Drug Resistance, Viral; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Mutation; Nucleosides; Reverse Transcriptase Inhibitors

Topics: Deoxyadenosines; HIV Infections; HIV-1; Humans

The newer generation NNRTIs, including doravirine and rilpivirine, were designed to show high potency and overcome K103N, Y181C and G190A resistance.. To assess emergent resistance to doravirine and rilpivirine, alone and paired with lamivudine or islatravir through in vitro drug selections.. Subtype B (n = 3), non-B subtype (n = 3), and pNL4.3 viral isolates were passaged in cord blood mononuclear cells with progressively increasing concentrations of drug(s). Genotypic analysis compared the acquisition and accumulation of drug resistance mutations at weeks 8 and 24 following drug pressure. Cell-based phenotypic assays assessed cross-resistance patterns to NNRTIs by acquired resistance mutations.. Doravirine pressure resulted in the acquisition of V108I (6/7) and V106A/I/M (5/7) mutations at weeks 8, followed by F227L (4/7), Y318F (4/7), M230L (2/7) or L234I (2/7) by weeks 24. In contrast, rilpivirine resulted in E138K (5/7) followed by L100I (3/7), K101E (1/7), or M230L (1/7). Doravirine resistance pathways retained susceptibility to rilpivirine, whereas rilpivirine resistance conferred intermediate resistance (12-152-fold) to doravirine. Dual selections with islatravir or lamivudine delayed and diminished emergent resistance to doravirine, resulting in V108I (9/15) with fewer or no other changes at weeks 24. There was a lesser delay in emergent resistance to rilpivirine when combined with islatravir or lamivudine. The M184V mutation did not arise in dual selections with islatravir or lamivudine.. Doravirine showed a more robust resistance profile compared with other NNRTIs. The long intracellular half-life of islatravir and delayed acquisition of resistance in dual selections provide an opportunity for long-acting treatment options.

Topics: Anti-HIV Agents; Cell Culture Techniques; Deoxyadenosines; Drug Resistance, Viral; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Mutation; Pyridones; Reverse Transcriptase Inhibitors; Triazoles

Islatravir (MK-8591) is a nucleoside reverse transcriptase translocation inhibitor in development for the treatment and prevention of HIV-1. The potential for islatravir to interact with commonly co-prescribed medications was studied in vitro. Elimination of islatravir is expected to be balanced between adenosine deaminase-mediated metabolism and renal excretion. Islatravir did not inhibit uridine diphosphate glucuronosyltransferase 1A1 or cytochrome p450 (CYP) enzymes CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, or 3A4, nor did it induce CYP1A2, 2B6, or 3A4. Islatravir did not inhibit hepatic transporters organic anion transporting polypeptide (OATP) 1B1, OATP1B3, organic cation transporter (OCT) 1, bile salt export pump (BSEP), multidrug resistance-associated protein (MRP) 2, MRP3, or MRP4. Islatravir was neither a substrate nor a significant inhibitor of renal transporters organic anion transporter (OAT) 1, OAT3, OCT2, multidrug and toxin extrusion protein (MATE) 1, or MATE2K. Islatravir did not significantly inhibit P-glycoprotein and breast cancer resistance protein (BCRP); however, it was a substrate of BCRP, which is not expected to be of clinical significance. These findings suggest islatravir is unlikely to be the victim or perpetrator of drug-drug interactions with commonly co-prescribed medications, including statins, diuretics, anti-diabetic drugs, proton pump inhibitors, anticoagulants, benzodiazepines, and selective serotonin reuptake inhibitors.

Topics: Animals; Biological Transport; Cytochrome P-450 Enzyme System; Deoxyadenosines; Dogs; Drug Interactions; HIV Infections; Humans; In Vitro Techniques; Madin Darby Canine Kidney Cells; Membrane Transport Proteins; Mice; Organic Anion Transporters; Pharmaceutical Preparations; Rabbits; Reverse Transcriptase Inhibitors

Topics: Adult; Anti-Retroviral Agents; Deoxyadenosines; HIV Infections; HIV-1; Humans; RNA-Directed DNA Polymerase

Topics: Animals; Anti-HIV Agents; Deoxyadenosines; Family Characteristics; HIV Infections; Macaca mulatta; Male; Pre-Exposure Prophylaxis

Topics: Adult; Deoxyadenosines; Female; Heterocyclic Compounds, 3-Ring; HIV Infections; HIV Integrase Inhibitors; Humans; Male; Oxazines; Piperazines; Pyridones; Vaccine-Preventable Diseases

Although antiretroviral therapy (ART) greatly suppresses HIV replication, lymphoid tissues remain a sanctuary site where the virus may replicate. Tracking the earliest steps of HIV spread from these cellular reservoirs after drug cessation is pivotal for elucidating how infection can be prevented. In this study, we developed an in vivo model of HIV persistence in which viral replication in the lymphoid compartments of humanized mice was inhibited by the HIV reverse transcriptase inhibitor 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) to very low levels, which recapitulated ART-suppression in HIV-infected individuals. Using a combination of RNAscope in situ hybridization (ISH) and immunohistochemistry (IHC), we quantitatively investigated the distribution of HIV in the lymphoid tissues of humanized mice during active infection, EFdA suppression, and after drug cessation. The lymphoid compartments of EFdA-suppressed humanized mice harbored very rare transcription/translation-competent HIV reservoirs that enable viral rebound. Our data provided the visualization and direct measurement of the early steps of HIV reservoir expansion within anatomically intact lymphoid tissues soon after EFdA cessation and suggest a strategy to enhance therapeutic approaches aimed at eliminating the HIV reservoir.

Topics: Animals; Deoxyadenosines; Disease Models, Animal; Disease Reservoirs; Female; HIV Infections; HIV-1; Humans; Lymphoid Tissue; Mice; Mice, Transgenic; Reverse Transcriptase Inhibitors; Virus Replication

Over the past 30 years, antiretroviral drug regimens for treating HIV infection have become more effective, safer, and more convenient. Despite 31 currently approved drugs, the pipeline of investigational HIV drugs remains full. Investigational antiretroviral drugs include the nucleoside analogue reverse transcriptase translocation inhibitor (NRTTI) MK-8591, a long-acting compound that could be dosed once weekly. Investigational nonnucleoside analogue reverse transcriptase inhibitors (NNRTIs) include doravirine, which is active in vitro against NNRTI-resistant HIV and was potent and well-tolerated when used in combination with a dual-nucleoside analogue RTI (nRTI) backbone in treatment-naive individuals.New integrase strand transfer inhibitors (InSTIs) include recently approved bictegravir, which is active against InSTI-resistant viral strains in vitro and was potent and well-tolerated in combination regimens in treatment-naive individuals, and investigational cabotegravir, which is being studied with monthly parenteral dosing for HIV maintenance treatment and with bimonthly dosing for HIV preexposure prophylaxis (PrEP). Investigational HIV entry inhibitors include the new CD4 attachment inhibitor fostemsavir, which targets HIV envelope glycoprotein 120, and recently approved ibalizumab, which binds the CD4 receptor. This article summarizes presentations by Roy M. Gulick, MD, MPH, at the IAS-USA continuing education program, Improving the Management of HIV Disease, held in Los Angeles, California, in April 2017, and at the 2017 Ryan White HIV/AIDS Program Clinical Conference, held in San Antonio, Texas, in August 2017.

Topics: Anti-HIV Agents; Antiretroviral Therapy, Highly Active; Deoxyadenosines; Drug Discovery; Drugs, Investigational; HIV Infections; Humans; Pre-Exposure Prophylaxis; Reverse Transcriptase Inhibitors

The 2018 Conference on Retroviruses and Opportunistic Infections (CROI) showcased exciting data on new investigational agents including MK-8591 and tri-specific antibody targeting 3 highly conserved epitopes on HIV-1 in a single antibody. Clinical trials of initial antiretroviral therapy (ART) and switch studies involving bictegravir/emtricitabine/tenofovir alafenamide were presented. Intensification of initial ART with integrase strand transfer inhibitors did not increase the risk of immune reconstitution inflammatory syndrome. Pharmacokinetic issues were discussed, including the substantial drug-drug interactions between efavirenz-based ART and hormonal contraception delivered via a vaginal ring. Studies on pre-ART drug resistance and emergence of drug resistance after initial and second-line ART in different settings and populations were highlighted. Novel technologies to identify drug resistance included a free, cloud-based web service for HIV genotyping analysis and a promising technology for point-of-care drug resistance mutations testing. New strategies to improve the HIV care continuum included home-based testing with initiation of same-day ART and stratified care with specialized clinics to serve those disengaged in care, but the data on financial incentives were not encouraging. Several studies provided insights into the impact of early ART on decreasing the size of the HIV reservoir in HIV-infected infants. Pertinent conference findings relating to women's health issues included similar clinical outcomes between breastfeeding and formula feeding HIV-infected women, the problem of viral rebound and ART nonadherence in pregnancy and postpartum.

Topics: Adenine; Amides; Anti-Retroviral Agents; Antiretroviral Therapy, Highly Active; Congresses as Topic; Deoxyadenosines; Drug Therapy, Combination; Emtricitabine; Heterocyclic Compounds, 3-Ring; Heterocyclic Compounds, 4 or More Rings; HIV Infections; HIV-1; Humans; Piperazines; Pyridones; Tenofovir; Viral Load

Regimen adherence remains a major hurdle to the success of daily oral drug regimens for the treatment and prevention of human immunodeficiency virus (HIV) infection. Long-acting drug formulations requiring less-frequent dosing offer an opportunity to improve adherence and allow for more forgiving options with regard to missed doses. The administration of long-acting formulations in a clinical setting enables health care providers to directly track adherence. MK-8591 (4'-ethynyl-2-fluoro-2'-deoxyadenosine [EFdA]) is an investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI) drug candidate under investigation as part of a regimen for HIV treatment, with potential utility as a single agent for preexposure prophylaxis (PrEP). The active triphosphate of MK-8591 (MK-8591-TP) exhibits protracted intracellular persistence and, together with the potency of MK-8591, supports its consideration for extended-duration dosing. Toward this end, drug-eluting implant devices were designed to provide prolonged MK-8591 release

Topics: Animals; Anti-HIV Agents; Deoxyadenosines; Drug Carriers; HIV Infections; HIV-1; Macaca mulatta; Male; Polymers; Rats; Rats, Wistar; Reverse Transcriptase Inhibitors

4'-Ethnyl-2'-fluoro-2'-deoxyadenosine (EFdA) is a novel translocation-defective reverse transcriptase inhibitor. We investigated the virological and biochemical inhibitory potentials of EFdA against a broad spectrum of subtype-specific chimeric viruses and compared it with tenofovir alafenamide, nevirapine, efavirenz, rilpivirine and etravirine.. pNL4.3 chimeric viruses encoding gag-pol from treatment-naive patients (n = 24) and therapy-failure patients (n = 3) and a panel of reverse transcriptase inhibitor-resistant strains (n = 7) were used to compare the potency of reverse transcriptase inhibitor drugs. The phenotypic drug susceptibility assay was performed using TZM-bl cells. In vitro inhibition assays were done using patient-derived reverse transcriptase. IC50 values of NNRTIs were calculated using a PicoGreen-based spectrophotometric assay. Steady-state kinetics were used to determine the apparent binding affinity (Km.dNTP) of triphosphate form of EFdA (EFdA-TP) and dATP.. Among the chimeric treatment-naive viruses, EFdA had an ex vivo antiretroviral activity [median (IQR) EC50 = 1.4 nM (0.6-2.1 nM)] comparable to that of tenofovir alafenamide [1.6 nM (0.5-3.6 nM)]. Subtype-specific differences were found for etravirine (P = 0.004) and rilpivirine (P = 0.017), where HIV-1C had the highest EC50 values. EFdA had a greater comparative efficiency [calculated by dividing the efficiency of monophosphate form of EFdA (EFdA-MP) incorporation (kcat.EFdA-TP/Km.EFdA-TP) over the efficiency of dATP incorporation (kcat.dATP/Km.dATP)] compared with the natural substrate dATP, with a fold change of between 1.6 and 3.2. Ex vivo analysis on reverse transcriptase inhibitor-resistant strains showed EFdA to have a higher potency. Despite the presence of rilpivirine DRMs, some non-B strains showed hypersusceptibility to rilpivirine.. Our combined virological and biochemical data suggest that EFdA inhibits both WT and reverse transcriptase inhibitor-resistant viruses efficiently in a subtype-independent manner. In contrast, HIV-1C is least susceptible to etravirine and rilpivirine.

Topics: Adenine; Alanine; Anti-Retroviral Agents; Deoxyadenosines; Drug Resistance, Viral; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Mutation; Recombination, Genetic; Reverse Transcriptase Inhibitors; Tenofovir; Treatment Failure

4'-Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA/MK-8591), a nucleoside reverse transcriptase inhibitor (NRTI) under clinical trials, is a potent and promising long-acting anti-HIV type 1 (HIV-1) agent. EFdA and its derivatives possess a modified 4'-moiety and potently inhibit the replication of a wide spectrum of HIV-1 strains resistant to existing NRTIs. Here, we report that EFdA and NRTIs with a 4'-ethynyl- or 4'-cyano-moiety exerted activity against HIV-1 with an M184V mutation and multiple NRTI-resistant HIV-1s, whereas NRTIs with other moieties (e.g., 4'-methyl) did not show this activity. Structural analysis indicated that EFdA and 4'-ethynyl-NRTIs (but not other 4'-modified NRTIs), formed strong van der Waals interactions with critical amino acid residues of reverse transcriptase. Such interactions were maintained even in the presence of a broad resistance-endowing M184V substitution, thus potently inhibiting drug-resistant HIV-1 strains. These findings also explain the mechanism for the potency of EFdA and provide insights for further design of anti-HIV-1 therapeutics.

Topics: Catalytic Domain; Cell Line; Deoxyadenosines; Drug Resistance, Viral; HEK293 Cells; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Molecular Docking Simulation; Point Mutation; Reverse Transcriptase Inhibitors

There is a pressing need to identify more effective antiretroviral drugs for HIV-2 treatment. Here, we show that the investigational compound MK-8591 (4'-ethynyl-2-fluoro-2'-deoxyadenosine [EFdA]) is highly active against group A and B isolates of HIV-2; 50% effective concentrations [EC

Topics: Anti-HIV Agents; Deoxyadenosines; Drug Resistance, Viral; HIV Infections; HIV Reverse Transcriptase; HIV-1; HIV-2; Humans; Microbial Sensitivity Tests; Reverse Transcriptase Inhibitors

4'-Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) is a potent nucleoside analogue inhibitor of HIV that has an unusually long half-life. Cell culture selections with either EFdA or lamivudine using both subtype B and non-B clinical isolates selected the M184I/V substitutions in reverse transcriptase (RT). Unlike lamivudine, however, EFdA retained significant activity against viruses containing the M184I/V substitutions. In other clinical trials that evaluated rilpivirine together with emtricitabine in first-line therapy, the emergence of both the M184I/V and E138K mutations in RT was demonstrated. Moreover, the M184I/V and E138K substitutions were shown to be compensatory for each other with regard to both efficiency of RT activity and viral replicative capacity. This creates concern that E138K might emerge as a compensatory mutation for M184I/V in the aftermath of the use of EFdA.. We wished to determine whether the E138K mutation in HIV RT together with M184I/V would compromise the activity of EFdA.. Recombinant viruses containing the M184I/V and/or E138K substitutions were generated by site-directed mutagenesis and evaluated in tissue culture for susceptibility to various nucleoside compounds, including EFdA.. Susceptibility to EFdA was retained in M184I/V viruses that also contained the E138K substitution. Moreover, the E138K substitution was not generated in these studies under selection pressure with EFdA.. These findings help to alleviate concern that EFdA may not be active against viruses that contain both the M184I/V and E138K substitutions in RT.

Topics: Amino Acid Substitution; Anti-HIV Agents; Clinical Trials as Topic; Deoxyadenosines; Drug Resistance, Viral; Emtricitabine; HEK293 Cells; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Lamivudine; Mutagenesis, Site-Directed; Mutation; Reverse Transcriptase Inhibitors; Rilpivirine; Virus Replication

The nucleoside reverse transcriptase inhibitor (NRTI) 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) in preclinical development exhibits improved safety and antiviral activity profiles with minimal drug resistance compared to approved NRTIs. However, the systemic antiviral efficacy of EFdA has not been fully evaluated. In this study, we utilized bone marrow/liver/thymus (BLT) humanized mice to investigate the systemic effect of EFdA treatment on HIV replication and CD4+ T cell depletion in the peripheral blood (PB) and tissues. In particular, we performed a comprehensive analysis of the female reproductive tract (FRT) and gastrointestinal (GI) tract, major sites of transmission, viral replication, and CD4+ T cell depletion and where some current antiretroviral drugs have a sub-optimal effect.. EFdA treatment resulted in reduction of HIV-RNA in PB to undetectable levels in the majority of treated mice by 3 weeks post-treatment. HIV-RNA levels in cervicovaginal lavage of EFdA-treated BLT mice also declined to undetectable levels demonstrating strong penetration of EFdA into the FRT. Our results also demonstrate a strong systemic suppression of HIV replication in all tissues analyzed. In particular, we observed more than a 2-log difference in HIV-RNA levels in the GI tract and FRT of EFdA-treated BLT mice compared to untreated HIV-infected control mice. In addition, HIV-RNA was also significantly lower in the lymph nodes, liver, lung, spleen of EFdA-treated BLT mice compared to untreated HIV-infected control mice. Furthermore, EFdA treatment prevented the depletion of CD4+ T cells in the PB, mucosal tissues and lymphoid tissues.. Our findings indicate that EFdA is highly effective in controlling viral replication and preserving CD4+ T cells in particular with high efficiency in the GI and FRT tract. Thus, EFdA represents a strong potential candidate for further development as a part of antiretroviral therapy regimens.

Topics: Animals; Anti-HIV Agents; Bone Marrow; CD4-Positive T-Lymphocytes; Deoxyadenosines; Disease Models, Animal; Female; Gastrointestinal Tract; Genes, Transgenic, Suicide; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Liver; Male; Mice; Reproductive Tract Infections; Reverse Transcriptase Inhibitors; Thymus Gland; Virus Replication

Approximately 1.5 million HIV-positive women become pregnant annually. Without treatment, up to 45% will transmit HIV to their infants, primarily through breastfeeding. These numbers highlight that HIV acquisition is a major health concern for women and children globally. They also emphasize the urgent need for novel approaches to prevent HIV acquisition that are safe, effective and convenient to use by women and children in places where they are most needed.. Strong HIV inhibitory activity in serum, cervicovaginal secretions and saliva obtained from animals after a single oral dose of 4'-ethynyl-2-fluoro-2'-deoxyadenosine (10 mg/kg) demonstrated efficient drug penetration into relevant mucosal sites. A single daily oral dose of 4'-ethynyl-2-fluoro-2'-deoxyadenosine resulted in efficient prevention of vaginal and oral HIV transmission after multiple high-dose exposures to transmitted/founder viruses in BLT humanized mice.. Our data demonstrated that 4'-ethynyl-2-fluoro-2'-deoxyadenosine efficiently prevents both vaginal and oral HIV transmission. Together with 4'-ethynyl-2-fluoro-2'-deoxyadenosine's relatively low toxicity and high potency against drug-resistant HIV strains, these data support further clinical development of 4'-ethynyl-2-fluoro-2'-deoxyadenosine as a potential pre-exposure prophylaxis agent to prevent HIV transmission in women and their infants.

Topics: Animals; Anti-HIV Agents; Bodily Secretions; Deoxyadenosines; Disease Models, Animal; Disease Transmission, Infectious; Female; HIV Infections; Longitudinal Studies; Mice; Mice, SCID; Mouth; Pre-Exposure Prophylaxis; Vagina

4'-Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) contains an ethynyl moiety and the 3'-hydroxyl and exerts highly potent activity against various HIV type-1 (HIV-1) strains including multi-drug-resistant variants.. Comparative selection passages against EFdA, lamivudine (3TC), tenofovir disoproxil fumarate (TDF), emtricitabine (FTC) or BMS-986001 (Ed4T) were conducted using a mixture of 11 highly multi-drug-resistant clinical HIV-1 isolates (HIV11MIX) as a starting virus population.. Before selection, HIV11MIX was sensitive to EFdA with a 50% inhibitory concentration (IC50) of 0.032 μM, less susceptible to TDF and Ed4T with IC50s of 0.57 and 2.6 μM, respectively, and highly resistant to 3TC and FTC with IC50s>10 μM. IC50s of TDF against HIV11MIX exposed to EFdA and TDF for 17 (HIV11MIX(EFdA-P17)) and 14 (HIV11MIX(TDF-P14)) passages were 8 and >10 μM, respectively, while EFdA remained active against HIV11MIX(EFdA-P17) and HIV11MIX(TDF-P14) with IC50s of 0.15 and 0.1 μM, respectively. Both selected variants were highly resistant against zidovudine, 3TC, Ed4T and FTC (IC50 values >10 μM).. The present data demonstrate that HIV11MIX developed resistance more rapidly against 3TC, FTC, TDF and Ed4T than against EFdA and that EFdA remained substantially active against TDF- and EFdA-selected variants. Thus, EFdA has a favourable resistance profile and represents a potentially promising new-generation nucleoside reverse transcriptase inhibitor.

Topics: Adenine; Amino Acid Sequence; Anti-HIV Agents; Deoxyadenosines; Deoxycytidine; Drug Resistance, Multiple, Viral; Emtricitabine; HIV Infections; HIV-1; Human Immunodeficiency Virus Proteins; Humans; Lamivudine; Molecular Sequence Data; Molecular Structure; Organophosphonates; Tenofovir; Thymidine

The aim of this work was to develop a fast-dissolving film formulation containing EFdA for potential use as a topical vaginal microbicide for prevention of HIV sexual transmission. Solid state compatibility approaches were used to screen commonly used polymers for formulation development. Factorial design and desirability function were used to investigate the effect of two variables, the ratio of the polymers and the concentration of selected plasticizer on four mechanical responses including tensile strength, elongation at break, toughness and elastic modulus for optimization of the film formulation. Assessments of EFdA-loaded films included physicochemical characteristics, in vitro cytotoxicity, epithelia integrity, ex vivo permeability and bioactivity test. The optimal placebo film was composed of PVA, HPMC E5 and propylene glycol (7:3:3, w/w), and its mechanical characteristics were comparable to those of VCF(®) film (a commercial vaginal film product). Permeability studies using human ectocervical explants showed that there was no significant difference in cumulative permeated amount of EFdA between EFdA film and free EFdA. The results of in vitro cytotoxicity and bioactivity testing showed that 50% cytotoxic concentration (CC50) was several orders of magnitude higher than 50% effective concentration (EC50) of EFdA. Furthermore, epithelial integrity study showed that EFdA-loaded film had a much lower toxicity to HEC-1A cell monolayers as compared to VCF(®). Therefore, EFdA-loaded vaginal film may be considered as a promising vaginal microbicide for HIV prevention.

Topics: Administration, Intravaginal; Anti-HIV Agents; Cell Line; Chemistry, Pharmaceutical; Deoxyadenosines; Dose-Response Relationship, Drug; Drug Compounding; Excipients; Female; HIV Infections; Humans; Middle Aged; Permeability; Plasticizers; Polymers; Reverse Transcriptase Inhibitors; Solubility; Time Factors

4' Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) is the most potent inhibitor of HIV reverse transcriptase (RT). We have recently named EFdA a Translocation Defective RT Inhibitor (TDRTI) because after its incorporation in the nucleic acid it blocks DNA polymerization, primarily by preventing translocation of RT on the template/primer that has EFdA at the 3'-primer end (T/PEFdA). The sugar ring conformation of EFdA may also influence RT inhibition by a) affecting the binding of EFdA triphosphate (EFdATP) at the RT active site and/or b) by preventing proper positioning of the 3'-OH of EFdA in T/PEFdA that is required for efficient DNA synthesis. Specifically, the North (C2'-exo/C3'-endo), but not the South (C2'-endo/C3'-exo) nucleotide sugar ring conformation is required for efficient binding at the primer-binding and polymerase active sites of RT. In this study we use nuclear magnetic resonance (NMR) spectroscopy experiments to determine the sugar ring conformation of EFdA. We find that unlike adenosine nucleosides unsubstituted at the 4'-position, the sugar ring of EFdA is primarily in the North conformation. This difference in sugar ring puckering likely contributes to the more efficient incorporation of EFdATP by RT than dATP. In addition, it suggests that the 3'-OH of EFdA in T/PEFdA is not likely to prevent incorporation of additional nucleotides and thus it does not contribute to the mechanism of RT inhibition. This study provides the first insights into how structural attributes of EFdA affect its antiviral potency through interactions with its RT target.

Topics: Anti-HIV Agents; Catalytic Domain; Deoxyadenosines; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Models, Molecular; Molecular Conformation; Nuclear Magnetic Resonance, Biomolecular

One of the formidable challenges in therapy of infections by human immunodeficiency virus (HIV) is the emergence of drug-resistant variants that attenuate the efficacy of highly active antiretroviral therapy (HAART). We have recently introduced 4'-ethynyl-nucleoside analogs as nucleoside reverse transcriptase inhibitors (NRTIs) that could be developed as therapeutics for treatment of HIV infections. In this study, we present 2'-deoxy-4'-C-ethynyl-2-fluoroadenosine (EFdA), a second generation 4'-ethynyl inhibitor that exerted highly potent activity against wild-type HIV-1 (EC50 approximately 0.07 nM). EFdA retains potency toward many HIV-1 resistant strains, including the multi-drug resistant clone HIV-1A62V/V75I/F77L/F116Y/Q151M. The selectivity index of EFdA (cytotoxicity/inhibitory activity) is more favorable than all approved NRTIs used in HIV therapy. Furthermore, EFdA efficiently inhibited clinical isolates from patients heavily treated with multiple anti-HIV-1 drugs. EFdA appears to be primarily phosphorylated by the cellular 2'-deoxycytidine kinase (dCK) because: (a) the antiviral activity of EFdA was reduced by the addition of dC, which competes nucleosides phosphorylated by the dCK pathway, (b) the antiviral activity of EFdA was significantly reduced in dCK-deficient HT-1080/Ara-Cr cells, but restored after dCK transduction. Further, unlike other dA analogs, EFdA is completely resistant to degradation by adenosine deaminase. Moderate decrease in susceptibility to EFdA is conferred by a combination of three RT mutations (I142V, T165R, and M184V) that result in a significant decrease of viral fitness. Molecular modeling analysis suggests that the M184V/I substitutions may reduce anti-HIV activity of EFdA through steric hindrance between its 4'-ethynyl moiety and the V/I184 beta-branched side chains. The present data suggest that EFdA, is a promising candidate for developing as a therapeutic agent for the treatment of individuals harboring multi-drug resistant HIV variants.

Topics: Animals; Antiretroviral Therapy, Highly Active; Cell Line; Deoxyadenosines; Drug Evaluation, Preclinical; Drug Resistance, Multiple, Viral; HIV Infections; HIV Reverse Transcriptase; HIV-1; Humans; Models, Molecular; Molecular Structure; Virus Replication