Antiviral Therapy

To investigate pharmacokinetic interactions associated with coadministration of lersivirine with zidovudine, tenofovir disoproxil fumarate (DF)/emtricitabine (Truvada®) or abacavir/lamivudine (Epzicom®/Kivexa®).

Three Phase I, open, crossover studies with two (studies 1 and 3) or three (study 2) treatment periods were conducted in healthy individuals. In study 1, individuals received zidovudine and placebo or zidovudine and lersivirine on days 1–14. In study 2, individuals received lersivirine and tenofovir DF/emtricitabine, lersivirine and placebo or tenofovir DF/emtricitabine and placebo on days 1–10. In study 3, individuals received abacavir/ lamivudine only in period 1 (5 days) and abacavir/lamivudine and lersivirine in period 2 (10 days). Blood samples were taken on days 1–14 (study 1) or day of final dose (studies 2 and 3) and analysed using high performance liquid chromatography/dual mass spectrometry. Pharmacokinetic parameters were calculated by standard non-compartmental methods.

When coadministered with lersivirine, zidovudine exposure increased by 35%, and exposure of its metabolite zidovudine-glucuronide decreased by 19%. Following coadministration of lersivirine and tenofovir DF/emtricitabine, tenofovir exposure increased by 30%, and lersivirine exposure decreased by 12%. Coadministration of lersivirine and abacavir/lamivudine increased abacavir exposure by 27% and decreased lamivudine exposure by 8%. Adverse events were predominantly mild in these Phase I studies.

Coadministration of lersivirine with zidovudine, tenofovir DF/emtricitabine or abacavir/lamivudine influenced the systemic exposure of all nucleoside reverse transcriptase inhibitor agents investigated (except for lamivudine; emtricitabine pharmacokinetics were not assessed). Changes were not considered clinically meaningful for zidovudine and abacavir. The clinical relevance of the effect on tenofovir pharmacokinetics is currently unknown.

IDX184 is a liver-targeted nucleotide prodrug that selectively inhibits HCV NS5B polymerase.

This randomized, double-blind, placebo-controlled, ascending-dose study investigated the antiviral activity, safety and pharmacokinetics of IDX184 plus pegylated interferon-α2a and ribavirin (P/R) in treatment-naive patients with genotype-1 HCV. A total of 81 patients with baseline HCV RNA≥5 log₁₀ IU/ml, alanine aminotransferase ≤3x upper limit of normal and compensated liver disease were dosed. Sequential cohorts of 20 patients, randomized 16:4 (active:placebo), received IDX184 for 14 days at rising daily doses of 50, 100, 150 or 200 mg in combination with P/R for 14 days.

At the end of triple dosing, HCV RNA changes from baseline (mean ±sd log ₁₀) and proportion of patients achieving undetectable viral load (<15 IU/ml) based on the efficacy-evaluable population were -2.7 ±1.3 (13%), -4.0 ±1.7 (50%), -4.2 ±1.9 (50%), -4.1 ±1.2 (40%), -4.3 ±1.5 (29%) and -3.7 ±1.2 (25%) for the 50 mg once daily, 50 mg twice daily, 100 mg once daily, 150 mg once daily, 100 mg twice daily and 200 mg once daily IDX184 doses, respectively. P/R alone resulted in a reduction of -1.5 ±1.3 log₁₀ with only 6% of patients with undetectable viral load. Patients with genotypes-1a or -1b responded similarly. No viral breakthrough or resistance associated with IDX184 was observed. Anti-HCV activity of IDX184 correlated with plasma exposure of its nucleoside metabolite 2′-methylguanosine. Most adverse events were mild or moderate in severity and were consistent with those associated with P/R. The most common adverse events were fatigue and headache.

IDX184 in combination with P/R for 14 days was well tolerated and demonstrated greater antiviral activity with more patients achieving undetectable viral load than P/R.

Lamivudine resistance develops in up to 80% of patients with chronic hepatitis B (CHB) after 5 years of treatment. Cross-resistance between nucleoside/nucleotide analogues limits management options in these patients. To investigate the role of pegylated interferon-α2a as rescue therapy in these patients, the efficacy and safety of pegylated interferon-α2a between treatment-naive patients and lamivudine-resistant patients with hepatitis B e antigen (HBeAg)-positive CHB were compared.

A total of 150 HBeAg-positive CHB patients were stratified according to prior treatment. Lamivudine-resistant patients (n=64) and treatment-naive patients (n=86) received pegylated interferon-α2a once-weekly for 48 weeks and were followed-up for an additional 24 weeks. Primary end points were HBeAg loss and HBV DNA <100,000 copies/ml at end of follow-up.

A total of 65 (76%) treatment-naive patients and 49 (77%) lamivudine-resistant patients completed treatment and 24 weeks of follow-up. Rates of HBeAg loss were comparable at end of follow-up between treatment-naive patients and lamivudine-resistant patients (20.9% and 23.4%, respectively; P=0.8423). Similarly, rates of HBV DNA<100,000 copies/ml were comparable at end of follow-up between treatment-naive patients and lamivudine-resistant patients (20.9% and 21.9%, respectively; P=1.000). There was no statistically significant difference in alanine aminotransferase normalization rates between treatment-naive patients and lamivudine-resistant patients (36.0% and 29.7%, respectively; P=0.4848). A total of one patient in each group achieved hepatitis B surface antigen (HBsAg) loss and seroconversion. The most common adverse events were those known to occur with pegylated interferon-α2a therapy, and safety profiles were similar between both patient populations.

Pegylated interferon-α2a may be effective as a rescue therapy in patients with lamivudine-resistant HBeAg-positive CHB.

Scavenger receptor class B type-1 (SR-B1) is one of the many receptors used by HCV to infect hepatocytes. It is used by the virus not only to directly infect cells but also to facilitate cell-to-cell transmission of the virus. Agents such as anti-human SR-B1 (anti-hSR-B1) antibodies represent potential therapeutics for the treatment of HCV infections. The purpose of this study was to evaluate the safety and pharmacokinetics of an anti-hSR-B1 antibody (Seq2) in cynomolgus monkeys.

The antibody was administered intravenously at 1, 10 and 100 mg/kg body weight; blood samples were taken pre- and post-dose to evaluate the pharmacokinetic profile and blood chemistry. Safety was assessed during treatment and the animals were sacrificed post-treatment for pathological assessment and liver antibody-receptor occupancy determination.

Following administration of Seq2 antibody to cynomolgus monkeys a non-linear pharmacokinetic pro-file was observed. The clearance of the antibody decreased from 2 to 0.3 ml/h/kg with increasing doses from 1 to 100 mg/kg, respectively, and the antibody half-life varied from 62 to 218 h for the same doses. An increase in total cholesterol and high-density lipoprotein cholesterol levels after antibody administration was observed, with a good correlation between liver receptor occupancy and dose.

The pharmacokinetics and toxicology results were in accordance with the pharmacology of the antibody mechanism. The elevation of total cholesterol was dose-dependent and did not exceed a twofold increase. The safety study indicated no adverse effects during the treatment or in the pathology analysis at any of the doses tested.

Antivirals reduce influenza viral replication and illness measures, particularly if initiated early, within 48 h of symptom onset. Whether experimental antivirals that reduce respiratory syncytial virus (RSV) load would also reduce disease is unknown. This study compares viral and disease dynamics in humans experimentally infected with influenza or RSV.

Clinical strains of RSV-A and influenza A were inoculated intranasally into 20 and 17 healthy volunteers, respectively, on day 0. Symptom scores and nasal washes were performed twice daily, and daily mucus weights were collected. Viral loads in nasal washes were quantified by culture (plaque assay in HEp-2 cells for RSV and by end point dilution in Madin–Darby canine kidney cells for influenza).

After influenza inoculation, influenza viral load and illness markers increased simultaneously until day 2. Within individual subjects, peak influenza load occurred 0.4 days (95% CI -0.4, 1.3) before peak symptoms. Influenza viral load and disease declined thereafter. After RSV inoculation, a longer incubation period occurred prior to viral detection and symptom onset. RSV load and disease increased together until day 5. Within individual subjects, peak RSV loads occurred 0.2 days (95% CI -0.7, 1.05) before peak symptoms, after which both illness measures and viral load declined together.

Viral and disease dynamics in experimental human infections suggest that reducing RSV load, if timed similarly to clinically-effective influenza antivirals, might be expected to have a similar or greater window of opportunity for reducing clinical RSV disease.

Current HIV treatment guidelines recommend using the Cockcroft–Gault equation for drug dosing adjustments. The use of newer glomerular filtration rate (GFR) estimating equations for drug dosing and the appropriateness of physician antiretroviral dosing based on estimated kidney function have not been studied in an HIV-positive population.

We evaluated concordance between measured and estimated GFR for the assignment of kidney function categories designated by the US Food and Drug Administration (FDA) Guidance for industry for pharmacokinetic studies, and appropriateness of physician antiretroviral drug dosing for level of kidney function in 200 HIV-positive patients on stable antiretroviral therapy. Estimated kidney function was determined using the Chronic Kidney Disease-Epidemiology collaboration (CKD-EPI), Modification of Diet in Renal Disease (MDRD) Study and Cockcroft–Gault equations.

For assignment of FDA-designated kidney function categories, concordance rates between measured and estimated GFR using the CKD-EPI, MDRD Study and Cockcroft–Gault equations were 79%, 71% and 77%, respectively. This pattern was consistent across most subgroups. When actual prescribed dosages were compared with recommended dosages based on the level of estimated kidney function, 3–19% of study participants were prescribed higher than recommended dosages. The largest discordance between prescribed and recommended dosages was observed for the Cockcroft–Gault equation.

The CKD-EPI equation has the highest concordance with measured GFR for the assignment of FDA-designated kidney function categories. Its use may lead to lower dosing-related errors in HIV-infected US adults on stable antiretroviral therapy. More education is required with respect to dose adjustment for level of kidney function.

Combination of several direct-acting antiviral agents will be necessary to overcome viral resistance in interferon-free treatment regimens for chronic HCV infection. HCV p7 inhibitors may be part of such combination regimens. Understanding why amantadine, despite showing inhibition of HCV p7 in vitro, appears ineffective in clinical trials, may help in the design of novel HCV p7 inhibitors. So far it is unknown whether viral escape mutations within HCV p7 explain the ineffectiveness of amantadine in vivo.

Pretreatment HCV p7 was directly sequenced in 157 consecutive patients with chronic HCV genotype 1b infection who had been treated with amantadine/placebo plus pegylated interferon (PEG-IFN)-α2a/ribavirin within a multicentre clinical trial. Triple therapy was preceded by 2 weeks of amantadine/placebo monotherapy. In nine patients, clonal sequencing was performed at baseline and after 2 weeks of amantadine/placebo monotherapy.

Changes of the relative frequency of amino acid substitutions by ≥20% between pretreatment and week 2 of monotherapy were considered potential resistance mutations if they were only found in patients receiving amantadine but not in patients receiving placebo. Seven substitutions fulfilling these criteria were identified in the subset of patients with clonal sequencing. However, none of these substitutions were associated with treatment outcome in the complete cohort of patients receiving triple therapy with amantadine.

Potential viral escape mutations within HCV p7 do not seem to play a major role for treatment response to antiviral therapy with amantadine and PEG-IFN-α2a/ribavirin in patients with chronic HCV genotype 1b infection.

Intraocular cytomegalovirus (CMV) infections, including endotheliitis and retinitis, have been reported to threaten the host's vision. These infections have been treated with systemic or intravitreal GCV injection. Intracameral GCV injection can be an effective treatment option that avoids systemic side effects. The cytotoxic effect of ganciclovir (GCV) on cultured human corneal endothelial cells (HCECs) was evaluated.

HCECs were cultured and exposed to various concentrations (0–20 mg/ml) of GCV (Cytovene®). Cell viability was assessed by the Cell Counting Kit-8 method and live/dead viability/cytotoxicity assays. Cell morphology was assessed using phase-contrast microscopy after 48 h exposure to GCV. Cell cycle and apoptosis were analysed using NC-3000 to evaluate the effect of GCV on HCECs. The cell proliferation rate was evaluated by a bromodeoxyuridine proliferation assay.

Cytotoxicity tests showed that GCV had a dose-dependent cytotoxic effect on HCECs. GCV concentrations of ≥5 mg/ml resulted in a significant reduction in cell viability. Higher concentrations of GCV resulted in cell cycle delay, low proliferation rate, and an increased number of apoptotic cells, indicating activation of the pro-apoptotic pathway.

Our results suggest that intracameral GCV concentrations of ≥5 mg/ml may increase the risk of corneal endothelial damage, although GCV concentrations of ≤0.5 mg/ml do not decrease cell viability.

In HIV-infected patients, therapeutic drug monitoring (TDM) of antiretroviral drugs is recommended in special populations and in specific situations to optimize therapy. Currently, TDM is performed via measurement of drug plasma concentrations; however, dried blood spots (DBS) may offer a patient friendly and cost-effective alternative. Therefore, this proof-of-concept study assessed the feasibility of TDM of antiretroviral drugs using DBS with sampling at home.

Included patients were instructed to sample three DBS just before drug intake at three consecutive days at home and one DBS sample together with their routine venous sampling. All samples were analysed using liquid chromatography coupled to tandem mass spectrometry. Feasibility was investigated with a questionnaire and via determination of the calculated plasma trough concentrations.

In total, 50 patients (48 male, mean age 50 years [range 29–69]) have been included, of whom most were virologically and immunologically well-controlled. In total, 200 DBS were collected, of which 87.5% were suitable for analysis. The questionnaire showed that most patients (68%) successfully obtained their first DBS and 51% preferred DBS over plasma sampling. Plasma trough concentrations could adequately be determined from DBS.

This proof-of-concept study confirms the feasibility of TDM of antiretroviral drugs using DBS with sampling at home, thereby opening the possibility to obtain trough concentrations at home in populations where venous sampling is difficult.

During a pandemic, the need for available anti-influenza medications increases. There has been extensive use of the approved zanamivir Rotadisk/Diskhaler but no clinical data are available for administration by an alternative Rotacap/Rotahaler presentation.

In this randomized three-way crossover study, each healthy adult received zanamivir 10 mg every 12 h for 5 days via Rotadisk/Diskhaler, via Rotacap/Rotahaler and placebo via Rotacap/Rotahaler, with a washout period between treatments. Safety assessments were conducted throughout the study and at follow-up. Serial blood samples for pharmacokinetic analysis were collected over a 12-h dose interval on day 5 of each treatment period. Pharmacokinetic parameters were compared using a mixed-effects model.

A total of 18 healthy adults were recruited and 17 subjects completed the study. A total of 20 adverse events (AEs) were reported (all grade 1) by nine subjects, with no AE reported ≥1x in any treatment group. Nasal congestion, reported by one subject in the zanamivir Rotadisk/Diskhaler group, was the only drug-related AE. No serious AEs or withdrawals due to AEs occurred during the study. There were no significant changes in clinical laboratory values, vital signs or spirometry. Serum zanamivir exposures were similar after administration via Rotacap/Rotahaler and Rotadisk/Diskhaler. Both oral inhalation presentations are likely to deliver similar zanamivir concentrations to sites of influenza infection in the respiratory tract.

The safety and pharmacokinetic results from this study support the use of the Rotacap/Rotahaler presentation, potentially allowing an increased number of zanamivir treatment courses to be supplied in the event of an influenza pandemic.