Pharmacokinetics and Safety of S/GSK1349572, a Next-Generation HIV Integrase Inhibitor,in Healthy Volunteers

S/GSK1349572 is a novel integrase inhibitor with potent in vitro anti-HIV activity, an in vitro resistance profile different from those of other integrase inhibitors, and favorable preclinical safety and pharmacokinetics (PK). Randomized, double-blind, placebo-controlled single-dose and multiple-dose, dose escalation studies evaluated the PK, safety, and tolerability of S/GSK1349572 for healthy subjects. In the single-dose study, two cohorts of 10 subjects each (8 active, 2 receiving placebo) received suspension doses of 2, 5, 10, 25, 50, and 100 mg in an alternating panel design. In the multiple-dose study, three cohorts of 10 subjects each (8 active, 2 receiving placebo) received suspension doses of 10, 25, and 50 mg once daily for 10 days. A cytochrome P450 3A (CYP3A) substudy with midazolam was conducted with the 25-mg dose. Laboratory testing, vital signs, electrocardiograms (ECGs), and PK sampling were performed at regular intervals. S/GSK1349572 was well tolerated. Most adverse events (AEs) were mild, with a few moderate AEs reported. Headache was the most common AE. No clinically significant laboratory trends or ECG changes were noted. PK was linear over the dosage range studied. The steady-state geometric mean area under the concentration-time curve over a dosing interval (AUC_0-τ) and maximum concentration of the drug in plasma (C_max) ranged from 16.7 μg·h/ml (coefficient of variation [CV], 15%) and 1.5 μg/ml (CV, 24%) at a 10-mg dose to 76.8 μg·h/ml (CV, 19%) and 6.2 μg/ml (CV, 15%) at a 50-mg dose, respectively. The geometric mean steady-state concentration at the end of the dosing interval (C_τ) with a 50-mg dose was 1.6 μg/ml, approximately 25-fold higher than the protein-adjusted 90% inhibitory concentration (0.064 μg/ml). The half-life was approximately 15 h. S/GSK1349572 had no impact on midazolam exposure, indicating that it does not modulate CYP3A activity. The PK profile suggests that once-daily, low milligram doses will achieve therapeutic concentrations.The introduction of human immunodeficiency virus (HIV) integrase inhibitors has ushered in a potent new class of drugs for HIV-infected individuals. These agents act upon a key viral target and demonstrate activity in treatment-experienced patients (4, 7, 9). Importantly, their adverse event (AE) profile does not appear to have many of the dose-limiting side effects of other classes, such as central nervous system disturbances, hyperlipidemia, and insulin resistance.S/GSK1349572 is an investigational HIV integrase inhibitor that preferentially blocks the strand transfer step of integration of the viral genome into the host cell''s DNA (6) and is designed to retain activity against raltegravir- and elvitegravir-resistant HIV. The proposed mechanism of inhibition involves the drug molecule chelating to two Mg²⁺ ions in the integrase DD(35)E catalytic active site. S/GSK1349572 was selected for clinical trials because nonclinical studies demonstrated a favorable safety profile, pharmacokinetics (PK) supporting once-daily dosing, and the potential for activity against raltegravir- and elvitegravir-resistant HIV. The primary route of metabolism is glucuronidation, and the compound does not demonstrate induction or inhibition of cytochrome P450 (CYP) isozymes in vitro. S/GSK1349572 demonstrates potent in vitro activity, with a 50% inhibitory concentration (IC₅₀) against HIV in peripheral blood mononuclear cells (PBMCs) of 0.51 nM and a protein-adjusted IC₉₀ of 0.064 μg/ml. The objective of these studies was to evaluate the safety and pharmacokinetics of S/GSK1349572 following single and repeat doses in healthy adult subjects.     

Pharmacokinetics and Pharmacodynamics of Setrobuvir,an Orally Administered Hepatitis C Virus Non-Nucleoside Analogue Inhibitor

PurposeNew antiviral agents with activity against hepatitis C virus (HCV) are needed to optimize treatment for chronic hepatitis C (CHC). We evaluated the pharmacokinetics of setrobuvir (a non-nucleoside HCV polymerase inhibitor) in healthy volunteers (study 1 & 2) and its antiviral efficacy in patients with genotype 1, noncirrhotic treatment-naive CHC (study 3).MethodsThree studies investigated the pharmacokinetics and pharmacodynamics of setrobuvir. First, sequential cohorts of volunteers were randomly assigned to receive single oral doses of setrobuvir 400 to 3000 mg or placebo in a double-blind, ascending dose study. In the second study, volunteers were randomly assigned to receive multiple doses of setrobuvir (400 or 800 mg once daily [QD] or 600 mg twice a day [BID]). In the third study, patients with genotype 1 CHC received setrobuvir (200, 400, or 800 mg) or placebo BID for 3 days.FindingsAfter single doses of setrobuvir (400–3000 mg) to volunteers in a fasted state, peak C_max and AUC_0–∞ increased in a less than dose-proportional manner. The mean apparent t_½z ranged from 22.0 to 31.3 hours and was not dose related. C_max and AUC increased significantly (4.3- and 6.3-fold, respectively) in volunteers who received 2000 mg with a high-fat meal versus fasting. After multiple oral doses, steady state was achieved after 7 days of dosing (400 or 800 mg QD and 600 mg BID) and accumulation was dose-independent. Mean day 14 plasma exposure increased in a less than dose-proportional manner in volunteers who received 400 and 800 mg QD, but it was more than dose-proportional in volunteers receiving 600 mg BID. Dose did not affect the mean t_½z (range, 24.1–26.6 hours), apparent oral clearance (0.254–0.516 L/h), or apparent volume of distribution (9.60–18.1 L). In patients with CHC, dose-related reductions in HCV RNA concentration were apparent within 24 hours of the start of treatment. Reductions from baseline to the end of treatment (day 3) in patients treated with setrobuvir 200, 400, and 800 mg BID were –2.1, –2.2, and –2.9 log₁₀ IU/mL, respectively (vs ≤0.1 log₁₀ IU/mL with placebo). Reductions in HCV RNA were greater in patients with genotype 1b (range, –2.7 to –3.1 log₁₀ IU/mL) than in patients with genotype 1a (range, –1.3 to –2.7 log₁₀ IU/mL). Setrobuvir was well tolerated, with no serious adverse events.ImplicationsThe steady state pharmacokinetics of setrobuvir appear to be dose proportional, and setrobuvir produces a mean reduction of 2.9 log₁₀ IU/mL in HCV RNA over 3 days in patients with genotype 1 (a and b) treated with 800 mg BID. ClinicalTrials.gov identifier: NCT00782353     

Preclinical Profile of BI 224436, a Novel HIV-1 Non-Catalytic-Site Integrase Inhibitor

BI 224436 is an HIV-1 integrase inhibitor with effective antiviral activity that acts through a mechanism that is distinct from that of integrase strand transfer inhibitors (INSTIs). This 3-quinolineacetic acid derivative series was identified using an enzymatic integrase long terminal repeat (LTR) DNA 3′-processing assay. A combination of medicinal chemistry, parallel synthesis, and structure-guided drug design led to the identification of BI 224436 as a candidate for preclinical profiling. It has antiviral 50% effective concentrations (EC₅₀s) of <15 nM against different HIV-1 laboratory strains and cellular cytotoxicity of >90 μM. BI 224436 also has a low, ∼2.1-fold decrease in antiviral potency in the presence of 50% human serum and, by virtue of a steep dose-response curve slope, exhibits serum-shifted EC₉₅ values ranging between 22 and 75 nM. Passage of virus in the presence of inhibitor selected for either A128T, A128N, or L102F primary resistance substitutions, all mapping to a conserved allosteric pocket on the catalytic core of integrase. BI 224436 also retains full antiviral activity against recombinant viruses encoding INSTI resistance substitutions N155S, Q148H, and E92Q. In drug combination studies performed in cellular antiviral assays, BI 224436 displays an additive effect in combination with most approved antiretrovirals, including INSTIs. BI 224436 has drug-like in vitro absorption, distribution, metabolism, and excretion (ADME) properties, including Caco-2 cell permeability, solubility, and low cytochrome P450 inhibition. It exhibited excellent pharmacokinetic profiles in rat (clearance as a percentage of hepatic flow [CL], 0.7%; bioavailability [F], 54%), monkey (CL, 23%; F, 82%), and dog (CL, 8%; F, 81%). Based on the excellent biological and pharmacokinetic profile, BI 224436 was advanced into phase 1 clinical trials.     

Safety,Tolerability, Pharmacokinetics,and Antiviral Activity of GSK2336805, an Inhibitor of Hepatitis C Virus (HCV) NS5A,in Healthy Subjects and Subjects Chronically Infected with HCV Genotype 1

GSK2336805 is an orally bioavailable hepatitis C virus (HCV) inhibitor working through an NS5A-mediated mechanism. This first-time-in-human study was conducted to assess the safety, tolerability, pharmacokinetics, metabolism, and efficacy of GSK2336805 in healthy subjects and subjects infected with HCV genotype 1. We performed a three-part, randomized, double-blind, placebo-controlled study in 46 healthy subjects and 23 HCV-infected subjects. After an overnight fast, healthy subjects received GSK2336805 as 10 mg, 30 mg, 30 mg plus food, and 60 mg in a single dose and 10 mg (7 days), 30 mg (7 days), and 75 mg (14 days) in a once-daily multiple dose. Subjects with HCV received GSK2336805 as a 1- to 120-mg single dose. In subjects with HCV, reductions in HCV RNA were observed within 4 h and a single dose of GSK2336805 of ≥10 mg resulted in a statistically significant ≥2-log reduction in HCV RNA compared with placebo at 24 h postdose. GSK2336805 was readily absorbed in all subjects, and the half-life (t_1/2) was suitable for once-daily dosing. Administration of GSK2336805 with food had no effect on plasma GSK2336805 exposure; however, absorption was delayed, with a median t_max (time to maximum concentration of drug in serum) of 4.5 versus 2.0 h. Twenty subjects who received GSK2336805 experienced mild to moderate adverse events; none were serious. GSK2336805 was well tolerated and exhibited rapid, significant antiviral activity after a single dose in HCV-infected subjects. These results support the conduct of further studies evaluating GSK2336805 administered once daily for longer durations in combination with peginterferon, ribavirin, and other direct-acting antivirals. (This study has been registered at ClinicalTrials.gov under registration no. {"type":"clinical-trial","attrs":{"text":"NCT01277692","term_id":"NCT01277692"}}NCT01277692.)     

Metabolism,Excretion, and Mass Balance of the HIV-1 Integrase Inhibitor Dolutegravir in Humans

The pharmacokinetics, metabolism, and excretion of dolutegravir, an unboosted, once-daily human immunodeficiency virus type 1 integrase inhibitor, were studied in healthy male subjects following single oral administration of [¹⁴C]dolutegravir at a dose of 20 mg (80 μCi). Dolutegravir was well tolerated, and absorption of dolutegravir from the suspension formulation was rapid (median time to peak concentration, 0.5 h), declining in a biphasic fashion. Dolutegravir and the radioactivity had similar terminal plasma half-lives (t_1/2) (15.6 versus 15.7 h), indicating metabolism was formation rate limited with no long-lived metabolites. Only minimal association with blood cellular components was noted with systemic radioactivity. Recovery was essentially complete (mean, 95.6%), with 64.0% and 31.6% of the dose recovered in feces and urine, respectively. Unchanged dolutegravir was the predominant circulating radioactive component in plasma and was consistent with minimal presystemic clearance. Dolutegravir was extensively metabolized. An inactive ether glucuronide, formed primarily via UGT1A1, was the principal biotransformation product at 18.9% of the dose excreted in urine and the principal metabolite in plasma. Two minor biotransformation pathways were oxidation by CYP3A4 (7.9% of the dose) and an oxidative defluorination and glutathione substitution (1.8% of the dose). No disproportionate human metabolites were observed.     

In Vitro Characterization of GSK2485852, a Novel Hepatitis C Virus Polymerase Inhibitor

GSK2485852 (referred to here as GSK5852) is a hepatitis C virus (HCV) NS5B polymerase inhibitor with 50% effective concentrations (EC₅₀s) in the low nanomolar range in the genotype 1 and 2 subgenomic replicon system as well as the infectious HCV cell culture system. We have characterized the antiviral activity of GSK5852 using chimeric replicon systems with NS5B genes from additional genotypes as well as NS5B sequences from clinical isolates of patients infected with HCV of genotypes 1a and 1b. The inhibitory activity of GSK5852 remained unchanged in these intergenotypic and intragenotypic replicon systems. GSK5852 furthermore displays an excellent resistance profile and shows a <5-fold potency loss across the clinically important NS5B resistance mutations P495L, M423T, C316Y, and Y448H. Testing of a diverse mutant panel also revealed a lack of cross-resistance against known resistance mutations in other viral proteins. Data from both the newer 454 sequencing method and traditional population sequencing showed a pattern of mutations arising in the NS5B RNA-dependent RNA polymerase in replicon cells exposed to GSK5852. GSK5852 was more potent than HCV-796, an earlier inhibitor in this class, and showed greater reductions in HCV RNA during long-term treatment of replicons. GSK5852 is similar to HCV-796 in its activity against multiple genotypes, but its superior resistance profile suggests that it could be an attractive component of an all-oral regimen for treating HCV.     

Identification of GS 4104 as an Orally Bioavailable Prodrug of the Influenza Virus Neuraminidase Inhibitor GS 4071

GS 4071 is a potent carbocyclic transition-state analog inhibitor of influenza virus neuraminidase with activity against both influenza A and B viruses in vitro. GS 4116, the guanidino analog of GS 4071, is a 10-fold more potent inhibitor of influenza virus replication in tissue culture than GS 4071. In this study we determined the oral bioavailabilities of GS 4071, GS 4116, and their respective ethyl ester prodrugs in rats. Both parent compounds and the prodrug of the guanidino analog exhibited poor oral bioavailability (2 to 4%) and low peak concentrations in plasma (C_maxs; C_max <0.06 μg/ml). In contrast, GS 4104, the ethyl ester prodrug of GS 4071, exhibited good oral bioavailability (35%) as GS 4071 and high C_maxs of GS 4071 (C_max = 0.47 μg/ml) which are 150 times the concentration necessary to inhibit influenza virus neuraminidase activity by 90%. The bioavailability of GS 4104 as GS 4071 was also determined in mice (30%), ferrets (11%), and dogs (73%). The plasma of all four species exhibited high, sustained concentrations of GS 4071 such that at 12 h postdosing the concentrations of GS 4071 in plasma exceeded those necessary to inhibit influenza virus neuraminidase activity by 90%. These results demonstrate that GS 4104 is an orally bioavailable prodrug of GS 4071 in animals and that it has the potential to be an oral agent for the prevention and treatment of influenza A and B virus infections in humans.     

Pharmacokinetics of Posaconazole Administered Orally or by Nasogastric Tube in Healthy Volunteers

The use of a nasogastric tube is one means of administering antifungal therapy to critically ill patients unable to receive medication via the oral route. This was a phase 1, open-label, single-center, randomized, crossover study of posaconazole administered via nasogastric tube in healthy volunteers. Each subject received two 400-mg single doses of posaconazole, one administered orally and one administered by nasogastric tube, with a 7-day washout period between each dose. Posaconazole was administered 5 to 10 min after subjects received a nutritional supplement. Blood samples for pharmacokinetic analysis were obtained up to 120 h postdose. The analysis of variance estimate of the study population suggests that the posaconazole nasogastric tube administration least-square mean values of observed maximum concentration (C_max), area under the plasma concentration-time curve (AUC) to the last measurable concentration, and AUC to time infinity were 81%, 76%, and 77%, respectively, of the corresponding oral administration values. The reason for lower C_max and AUC values when posaconazole is administered via the nasogastric tube route is not known. Oral and nasogastric tube administration of a single 400-mg dose of posaconazole suspension was safe and well tolerated in healthy adult subjects. The incidence and nature of treatment-emergent adverse events were similar with both administration routes, and no serious adverse events or clinically significant laboratory test or vital sign abnormalities were reported. Obtaining plasma posaconazole concentrations may be warranted when posaconazole is given to patients via a nasogastric tube to ensure adequate posaconazole exposure. Strategies that have been shown to enhance posaconazole exposure (such as splitting the dose and minimizing the use of proton pump inhibitors) may also be used.Posaconazole is a triazole antifungal that has shown potent in vitro and in vivo activities against an extended spectrum of clinically important yeasts and molds (9). Posaconazole prevented invasive fungal infections (IFIs) more effectively than did either fluconazole or itraconazole and improved overall survival in patients undergoing chemotherapy for acute myelogenous leukemia or myelodysplastic syndrome (2). Posaconazole was as effective as fluconazole in preventing all IFIs and was superior to fluconazole in preventing invasive aspergillosis and reducing the rate of IFI-attributable death in hematopoietic stem cell transplant recipients with severe graft-versus-host disease (23). Salvage treatment with posaconazole has been shown to be effective in the treatment of invasive aspergillosis (25), fusariosis (18), and zygomycosis (8, 24).Critically ill patients who are unable to take oral nutrition are often administered alternative nutrition via nasogastric tube (5). Nasogastric feeding is most common in the intensive care unit (ICU) and is also used for cancer patients who are unable to eat (e.g., those with mucositis) or do not want to eat due to severe nausea (16). In these cases, alternates to oral drug administration, including intravenous or nasogastric tube administration, may be sought.Currently, posaconazole is available only as an oral suspension, and intravenous administration is not possible. Absorption data obtained in healthy volunteers support that posaconazole is well absorbed and extensively distributed to many tissue sites following oral administration (3). Exposure can be increased by administration with a high-fat meal (4) or a nutritional supplement (20) and by dividing the total daily dosage into multiple doses per day (6). Data from stem cell transplant patients with graft-versus-host disease have demonstrated that oral posaconazole administered prophylactically results in concentrations of posaconazole likely to be effective against pathogenic fungi in this patient population despite concurrent gastrointestinal disease (10). Little is known, however, about alternate routes of posaconazole administration.The present study was conducted with healthy volunteers to determine the effect, if any, of nasogastric tube administration on the pharmacokinetic profile of posaconazole. The primary objective was to compare the systemic exposure from a single 400-mg dose of posaconazole suspension administered orally with that of the same dose administered via nasogastric tube. The secondary objective was to monitor the safety and tolerability of two single doses of posaconazole, one administered orally and the other via nasogastric tube. Since a previous study had demonstrated the bioavailability of posaconazole when coadministered with Boost Plus (20), posaconazole was administered with the same nutritional supplement in this trial.     

Carbenicillin Indanyl Sodium, an Orally Active Derivative of Carbenicillin

Carbenicillin indanyl sodium, an orally active derivative of carbenicillin, is active against a broad spectrum of bacterial species. Although the ester has in vitro antimicrobial activity per se when evaluated in Brain Heart Infusion broth, the in vivo antibacterial activity seen in mice and rats reflects primarily the efficient hydrolysis of the ester to carbenicillin. With an acute systemic infection in mice as a test system, orally administered carbenicillin indanyl sodium protected mice against lethal infections produced by Escherichia coli, Salmonella choleraesuis, Pasteurella multocida, Proteus vulgaris, Staphylococcus aureus, and Streptococcus pyogenes. The dose that protected 50% of the animals against each of these infections was comparable to that of parenteral carbenicillin. Against experimental urinary-tract disease in rats produced by E. coli, P. vulgaris, and Pseudomonas aeruginosa, it was again observed that carbenicillin indanyl sodium provided activity comparable to that of parenterally administered carbenicillin.     

In Vitro antiretroviral properties of S/GSK1349572, a next-generation HIV integrase inhibitor

S/GSK1349572 is a next-generation HIV integrase (IN) inhibitor designed to deliver potent antiviral activity with a low-milligram once-daily dose requiring no pharmacokinetic (PK) booster. In addition, S/GSK1349572 demonstrates activity against clinically relevant IN mutant viruses and has potential for a high genetic barrier to resistance. S/GSK1349572 is a two-metal-binding HIV integrase strand transfer inhibitor whose mechanism of action was established through in vitro integrase enzyme assays, resistance passage experiments, activity against viral strains resistant to other classes of anti-HIV agents, and mechanistic cellular assays. In a variety of cellular antiviral assays, S/GSK1349572 inhibited HIV replication with low-nanomolar or subnanomolar potency and with a selectivity index of 9,400. The protein-adjusted half-maximal effective concentration (PA-EC(50)) extrapolated to 100% human serum was 38 nM. When virus was passaged in the presence of S/GSK1349572, highly resistant mutants were not selected, but mutations that effected a low fold change (FC) in the EC(50) (up to 4.1 fold) were identified in the vicinity of the integrase active site. S/GSK1349572 demonstrated activity against site-directed molecular clones containing the raltegravir-resistant signature mutations Y143R, Q148K, N155H, and G140S/Q148H (FCs, 1.4, 1.1, 1.2, and 2.6, respectively), while these mutants led to a high FC in the EC(50) of raltegravir (11- to >130-fold). Either additive or synergistic effects were observed when S/GSK1349572 was tested in combination with representative approved antiretroviral agents; no antagonistic effects were seen. These findings demonstrate that S/GSK1349572 would be classified as a next-generation drug in the integrase inhibitor class, with a resistance profile markedly different from that of first-generation integrase inhibitors.     

In Vitro and In Vivo Antiviral Activity and Resistance Profile of Ombitasvir,an Inhibitor of Hepatitis C Virus NS5A

Ombitasvir (ABT-267) is a hepatitis C virus (HCV) NS5A inhibitor with picomolar potency, pan-genotypic activity, and 50% effective concentrations (EC₅₀s) of 0.82 to 19.3 pM against HCV genotypes 1 to 5 and 366 pM against genotype 6a. Ombitasvir retained these levels of potency against a panel of 69 genotype 1 to 6 chimeric replicons containing the NS5A gene derived from HCV-infected patients, despite the existence of natural sequence diversity within NS5A. In vitro resistance selection identified variants that conferred resistance to ombitasvir in the HCV NS5A gene at amino acid positions 28, 30, 31, 58, and 93 in genotypes 1 to 6. Ombitasvir was evaluated in vivo in a 3-day monotherapy study in 12 HCV genotype 1-infected patients at 5, 25, 50, or 200 mg dosed once daily. All patients in the study were HCV genotype 1a infected and were without preexisting resistant variants at baseline as determined by clonal sequencing. Decreases in HCV RNA up to 3.1 log₁₀ IU/ml were observed. Resistance-associated variants at position 28, 30, or 93 in NS5A were detected in patient samples 48 hours after the first dose. Clonal sequencing analysis indicated that wild-type virus was largely suppressed by ombitasvir during 3-day monotherapy, and at doses higher than 5 mg, resistant variant M28V was also suppressed. Ombitasvir was well tolerated at all doses, and there were no serious or severe adverse events. These data support clinical development of ombitasvir in combination with inhibitors targeting HCV NS3/4A protease (ABT-450 with ritonavir) and HCV NS5B polymerase (ABT-333, dasabuvir) for the treatment of chronic HCV genotype 1 infection. (Study M12-116 is registered at ClinicalTrials.gov under registration no. {"type":"clinical-trial","attrs":{"text":"NCT01181427","term_id":"NCT01181427"}}NCT01181427.)     

Preclinical Activity of VX-787, a First-in-Class,Orally Bioavailable Inhibitor of the Influenza Virus Polymerase PB2 Subunit

VX-787 is a novel inhibitor of influenza virus replication that blocks the PB2 cap-snatching activity of the influenza viral polymerase complex. Viral genetics and X-ray crystallography studies provide support for the idea that VX-787 occupies the 7-methyl GTP (m⁷GTP) cap-binding site of PB2. VX-787 binds the cap-binding domain of the PB2 subunit with a K_D (dissociation constant) of 24 nM as determined by isothermal titration calorimetry (ITC). The cell-based EC₅₀ (the concentration of compound that ensures 50% cell viability of an uninfected control) for VX-787 is 1.6 nM in a cytopathic effect (CPE) assay, with a similar EC₅₀ in a viral RNA replication assay. VX-787 is active against a diverse panel of influenza A virus strains, including H1N1pdm09 and H5N1 strains, as well as strains with reduced susceptibility to neuraminidase inhibitors (NAIs). VX-787 was highly efficacious in both prophylaxis and treatment models of mouse influenza and was superior to the neuraminidase inhibitor, oseltamivir, including in delayed-start-to-treat experiments, with 100% survival at up to 96 h postinfection and partial survival in groups where the initiation of therapy was delayed up to 120 h postinfection. At different doses, VX-787 showed a 1-log to >5-log reduction in viral load (relative to vehicle controls) in mouse lungs. Overall, these favorable findings validate the PB2 subunit of the viral polymerase as a drug target for influenza therapy and support the continued development of VX-787 as a novel antiviral agent for the treatment of influenza infection.