Effects of a novel sodium channel blocker, GSK2339345, in patients with refractory chronic cough
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OBJECTIVE: Voltage-gated sodium channels (VGSC) are important in the initiation and propagation of action potentials in afferent sensory nerve fibers responsible for evoking cough. This study investigated the efficacy of GSK2339345, a VGSC inhibitor, in the treatment of refractory chronic cough (RCC). METHODS: A three-part randomized, double-blind, placebo-controlled, cross-over study was conducted in the UK. In part A, patients with RCC received two inhaled doses of either GSK2339345 or placebo, 4 hours apart during three study periods. Patients were monitored for cough for 8 hours post-first dose using the VitaloJAK, ambulatory cough monitor. In parts B and C, patients underwent full dose-response cough challenges with capsaicin and citric acid respectively following single doses of randomly assigned GSK2339345 or placebo (4 study days). Part A was analyzed using a mixed effects model and parts B and C using population non-linear mixed effects models. RESULTS: Of 16 enrolled patients, 11 completed the study. 8-hour cough counts increased following GSK2339345 treatment compared with placebo (GSK2339345/placebo ratio of adjusted geometric means: 1.26 (90% credible interval 1.10, 1.44), associated with GSK2339345-evoked coughing, recorded during the 2 minutes post-dose. This was not observed with placebo. The effect of GSK2339345 on cough responses during cough challenges was inconclusive. GSK2339345 was well tolerated. CONCLUSIONS: While these data could not determine if GSK2339345 reached the target VGSC, they strongly suggest that GSK2339345 has no anti-tussive effect despite reaching airway sensory nerves as evidenced by the evoked transient cough.
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Quantifying the Effectiveness of Dose Individualization by Simulation for a Drug With Moderate Pharmacokinetic Variability.

BACKGROUND: Dose individualization can reduce variability in exposure. The objective of this work was to quantify, through pharmacokinetic (PK) simulation, the potential for reducing the variability in exposure by dose individualization for a drug with moderate PK variability between subjects and between occasions within a subject, and a narrow therapeutic window. METHODS: Using a population PK model that includes between-subject and between-occasion variability for apparent clearance, individual PK profiles in a trial of 300 subjects after a test dose were simulated. From the simulated data, datasets were created mimicking various sampling regimens (from single predose sample to full profile samples over 12 hours) on 1 or more occasions (1, 2, 3, 5, or 10 visits). Using these datasets, individual apparent clearance values were estimated, which were then used to calculate an individualized dose for a predefined target area under the concentration-time curve (AUC), based on the available formulation strengths. The proportion of people whose mean AUC was within a predefined therapeutic AUC range was calculated for the test (before) and the individualized dose (after), and compared between the different sampling scenarios. RESULTS: The maximum increase in proportion of subjects with an AUC within the range was 20%. To achieve this benefit, PK samples over 4 hours from 100 dosing occasions were required. As a result of the dose adjustment, the AUC of 7.3% of the subjects moved from inside the therapeutic range to outside of the range. CONCLUSIONS: This work shows how modeling and simulation can help assess the benefit and risk of dose individualization for a compound with variability between subjects and between occasions. The framework can be applied to similar situations with a defined set of conditions (eg, therapeutic window, tablet strengths, and PK and/or pharmacodynamic sampling scheme) to inform dose change and to assess the utility of dose individualization against certain success criteria.

A randomised, double-blind, placebo-controlled study of the LAG-3-depleting monoclonal antibody GSK2831781 in patients with active ulcerative colitis.

BACKGROUND: Selective depletion of T cells expressing LAG-3, an immune checkpoint receptor that is upregulated on activated T cells, has been investigated in pre-clinical models as a potential therapeutic approach in inflammatory and autoimmune diseases where activated T cells are implicated. AIMS: GSK2831781, a depleting monoclonal antibody that specifically binds LAG-3 proteins, may deplete activated LAG-3+ cells in ulcerative colitis (UC). METHODS: Patients with moderate to severe UC were randomised to GSK2831781 or placebo. Safety, tolerability, efficacy, pharmacokinetics and pharmacodynamics of GSK2831781 were evaluated. RESULTS: One hundred four participants across all dose levels were randomised prior to an interim analysis indicating efficacy futility criteria had been met. Efficacy results focus on the double-blind induction phase of the study (GSK2831781 450 mg intravenously [IV], N = 48; placebo, N = 27). Median change from baseline (95% credible interval [CrI]) in complete Mayo score was similar between groups (GSK2831781 450 mg IV: -1.4 [-2.2, -0.7]; placebo: -1.4 [-2.4, -0.5]). Response rates for endoscopic improvement favoured placebo. Clinical remission rates were similar between groups. In the 450-mg IV group, 14 (29%) participants had an adverse event of UC versus 1 (4%) with placebo. LAG-3+ cells were depleted to 51% of baseline in blood; however, there was no reduction in LAG-3+ cells in the colonic mucosa. Transcriptomic analysis of colon biopsies showed no difference between groups. CONCLUSION: Despite evidence of target cell depletion in blood, GSK2831781 failed to reduce inflammation in the colonic mucosa suggesting no pharmacological effect. The study was terminated early (NCT03893565).

Randomized Trial of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of GSK2831781 in Healthy Japanese and White Participants.

This study investigated ethnic differences in the safety, tolerability, pharmacokinetics, and pharmacodynamics of GSK2831781, an anti-lymphocyte activation gene 3 (LAG3) monoclonal antibody, in healthy participants, and determined local tolerability and bioavailability following subcutaneous (SC) administration. A double-blind, randomized study of (A) single intravenous (IV) doses of GSK2831781 450 mg or placebo in Japanese and White participants; and (B) single SC doses of GSK2831781 150 or 450 mg, or placebo in White participants, was conducted. Blood samples for analyses were collected before dosing and over 112 days after dosing. GSK2831781 was well tolerated in Japanese and White participants after both IV and SC doses, with the adverse event profile in Japanese being consistent with other populations. There were no injection site adverse events. There was no evidence of differences in systemic exposure among Japanese and White participants. Systemic exposure did not vary with body weight. SC bioavailability was 76.5%, as estimated using population pharmacokinetic modeling. Full and sustained target engagement and evidence of LAG3+ cell depletion (≈53%-66%) were observed in both populations and after both administration routes. No evidence of reduced circulating regulatory T cells (CD4+ CD25+ CD127low FoxP3+ ) was observed. Following IV and SC administration, GSK2831781 depleted circulating LAG3+ T cells with no interethnic difference observed. There were no major impacts on circulating regulatory T cells.

Depletion of LAG-3+ T Cells Translated to Pharmacology and Improvement in Psoriasis Disease Activity: A Phase I Randomized Study of mAb GSK2831781.

Activated T cells drive a range of immune-mediated inflammatory diseases. LAG-3 is transiently expressed on recently activated CD4+ and CD8+ T cells. We describe the engineering and first-in-human clinical study (NCT02195349) of GSK2831781 (an afucosylated humanized IgG1 monoclonal antibody enhanced with high affinity for Fc receptors and LAG-3 and antibody-dependent cellular cytotoxicity capabilities), which depletes LAG-3 expressing cells. GSK2831781 was tested in a phase I/Ib, double-blind, placebo-controlled clinical study, which randomized 40 healthy participants (part A) and 27 patients with psoriasis (part B) to single doses of GSK2831781 (up to 0.15 and 5 mg/kg, respectively) or placebo. Adverse events were generally balanced across groups, with no safety or tolerability concern identified. LAG-3+ cell depletion in peripheral blood was observed at doses ≥ 0.15 mg/kg and was dose-dependent. In biopsies of psoriasis plaques, a reduction in mean group LAG-3+ and CD3+ T-cell counts was observed following treatment. Downregulation of proinflammatory genes (IL-17A, IL-17F, IFNγ, and S100A12) and upregulation of the epithelial barrier integrity gene, CDHR1, was observed with the 5 mg/kg dose of GSK2831781. Psoriasis disease activity improved up to day 43 at all GSK2831781 doses (0.5, 1.5, and 5 mg/kg) compared with placebo. Depletion of LAG-3-expressing activated T cells is a novel approach, and this first clinical study shows that GSK2831781 is pharmacologically active and provides encouraging early evidence of clinical effects in psoriasis, which warrants further investigation in T-cell-mediated inflammatory diseases.

Identification, preclinical profile, and clinical proof of concept of an orally bioavailable pro-drug of miridesap.

BACKGROUND AND PURPOSE: Miridesap, a depleter of serum amyloid P component (SAP), forms an essential component of a novel approach to remove systemic amyloid deposits; low oral bioavailability necessitates that it is given parenterally. We sought to identify and clinically characterise a pro-drug that preserves the pharmacological properties of miridesap while having adequate oral bioavailability and physical stability. EXPERIMENTAL APPROACH: We utilised a preclinical screening cascade focused on appropriate physicochemical properties, physical and gut stability, and conversion to miridesap in liver microsomes and blood. GSK3039294 (GSK294) had the desired in vitro profile and progressed to preclinical in vivo pharmacokinetic and safety assessments. Based on a favourable profile, it was tested in healthy participants after single and repeat dosing. KEY RESULTS: GSK294 was highly soluble and stable in simulated gastric and intestinal fluids, stable in intestinal microsomes, and permeable in Madine Darby Canine Kidney type II cells. GSK294 was rapidly hydrolysed to miridesap and its mono pro-drug ester in blood and liver microsomes. GSK294 showed good oral bioavailability of miridesap in rats and dogs. Following administration of GSK294 600 mg QD for 7 days in humans, pharmacodynamically active concentrations of miridesap were achieved with substantial and sustained depletion of plasma SAP. The study was terminated due to observations of arrhythmia, the relation of which to GSK294 remains unclear. CONCLUSION AND IMPLICATIONS: Using a preclinical screening cascade, we identified a pro-drug for a palindromic molecule with unique pharmacology (miridesap). The pro-drug depleted circulating SAP with a time course and extent similar to that of parenterally administered miridesap.

Changes in GABAA receptor properties in amygdala kindled animals: in vivo studies using [11C]flumazenil and positron emission tomography.

PURPOSE: The purpose of the present investigation was to quantify alterations in GABA(A) receptor density in vivo in rats subjected to amygdala kindling. METHODS: The GABA(A) receptor density was quantified by conducting a [(11)C]flumazenil (FMZ) positron emission tomography (PET) study according to the full saturation method, in which each animal received a single injection of FMZ to fully saturate the GABA(A) receptors. Subsequently, the concentration-time curves of FMZ in blood [using high-pressure liquid chromatography with UV detector (HPLC-UV) or high-performance liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS)] and brain (with PET-scanning) were analyzed by population modeling using a pharmacokinetic model, containing expressions to describe the time course of FMZ in blood and brain. RESULTS: The GABA(A) receptor density (B(max)) in kindled rats was decreased by 36% compared with controls. This is consistent with a reduction of 28% in electroencephalography (EEG) effect of midazolam in the same animal model, suggesting that a reduced number of GABA(A) receptors underlies the decreased efficacy of midazolam. Furthermore, receptor affinity (K(D)) was not changed, but the total volume of distribution in the brain (V(Br)), is increased to 178% of control after kindling, which might indicate an alteration in the transport of FMZ across the blood-brain barrier. CONCLUSIONS: Both the GABA(A) receptor density (B(max)), and possibly also the blood-brain barrier transport of FMZ (V(Br)) are altered after kindling. Furthermore, this study indicates the feasibility of conducting PET studies for quantifying moderate changes in GABA(A) receptor density in a rat model of epilepsy in vivo.

Evaluation of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of a Single Intravenous Dose of Miridesap in Healthy Japanese Subjects.

This phase 1 study characterized the safety, tolerability, pharmacokinetics, and pharmacodynamics of miridesap (GSK2315698) following an intravenous (IV) infusion in healthy Japanese men. Subjects in Cohort 1 received 1-hour IV infusions of 10, 20, and 40 mg of miridesap or placebo, and subjects in Cohort 2 received a 15-hour IV infusion of 20 mg/h of miridesap or placebo. No treatment-related adverse events were reported. No new safety signals were identified for either vital signs or clinical laboratory parameters. A dose-dependent increase was observed in miridesap exposure (area under the concentration-time curve and maximum observed drug concentration) in the 10 to 40 mg/h dose range after a 1-hour IV infusion of miridesap. Rapid depletion of circulating serum amyloid P component was observed after the initiation of miridesap infusion. Serum amyloid P component concentrations fell in a dose-dependent manner following administration of miridesap.

Time-to-Event Modeling of Left- or Right-Censored Toxicity Data in Nonclinical Drug Toxicology.

A time-to-event (TTE) model has been developed to characterize a histopathology toxicity that can only be detected at the time of animal sacrifice. The model of choice was a hazard model with a Weibull distribution and dose was a significant covariate. The diagnostic plots showed a satisfactory fit of the data, despite the high degree of left and right censoring. Comparison to a probabilistic logit model shows similar performance in describing the data with a slight underestimation of survival by the Logit model. However, the TTE model was found to be more predictive in extrapolating toxicity risk beyond the observation range of a truncated dataset. The diagnostic and comparison outcomes would suggest using the TTE approach as a first choice for characterizing short and long-term risk from nonclinical toxicity studies. However, further investigations are needed to explore the domain of application of this kind of approach in drug safety assessment.

Repeat doses of antibody to serum amyloid P component clear amyloid deposits in patients with systemic amyloidosis.

Systemic amyloidosis is a fatal disorder caused by pathological extracellular deposits of amyloid fibrils that are always coated with the normal plasma protein, serum amyloid P component (SAP). The small-molecule drug, miridesap, [(R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC)] depletes circulating SAP but leaves some SAP in amyloid deposits. This residual SAP is a specific target for dezamizumab, a fully humanized monoclonal IgG1 anti-SAP antibody that triggers immunotherapeutic clearance of amyloid. We report the safety, pharmacokinetics, and dose-response effects of up to three cycles of miridesap followed by dezamizumab in 23 adult subjects with systemic amyloidosis (ClinicalTrials.gov identifier: NCT01777243). Amyloid load was measured scintigraphically by amyloid-specific radioligand binding of 123I-labeled SAP or of 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid. Organ extracellular volume was measured by equilibrium magnetic resonance imaging and liver stiffness by transient elastography. The treatment was well tolerated with the main adverse event being self-limiting early onset rashes after higher antibody doses related to whole body amyloid load. Progressive dose-related clearance of hepatic amyloid was associated with improved liver function tests. 123I-SAP scintigraphy confirmed amyloid removal from the spleen and kidneys. No adverse cardiac events attributable to the intervention occurred in the six subjects with cardiac amyloidosis. Amyloid load reduction by miridesap treatment followed by dezamizumab has the potential to improve management and outcome in systemic amyloidosis.

Population Pharmacokinetic Modeling of Tapentadol Extended Release (ER) in Healthy Subjects and Patients with Moderate or Severe Chronic Pain.

BACKGROUND AND OBJECTIVE: Tapentadol is a centrally acting analgesic with two mechanisms of action, µ-opioid receptor agonism and noradrenaline reuptake inhibition. The objectives were to describe the pharmacokinetic behavior of tapentadol after oral administration of an extended-release (ER) formulation in healthy subjects and patients with chronic pain and to evaluate covariate effects. METHODS: Data were obtained from 2276 subjects enrolled in five phase I and nine phase II and III studies. Nonlinear mixed-effects modeling was conducted using NONMEM. RESULTS: The population estimates of apparent oral clearance and apparent central volume of distribution were 257 L/h and 1870 L, respectively. The complex absorption was described with a transit compartment for the first input. The second input function embraces saturable "binding" in the "absorption compartment", and a time-varying rate constant. Covariate evaluation demonstrated that age, aspartate aminotransferase, and health (painful diabetic neuropathy or not) had a statistically significant effect on apparent clearance, and bioavailability appeared to be dependent on body weight. The pcVPC indicted that the model provided a robust and unbiased fit to the data. CONCLUSIONS: A one-compartment disposition model with two input functions and first-order elimination adequately described the pharmacokinetics of tapentadol ER. The dose-dependency in the pharmacokinetics of tapentadol ER is adequately described by the absorption model. None of the covariates were considered as clinically relevant factors that warrant dose adjustments.

Population pharmacokinetic analysis for simultaneous determination of B (max) and K (D) in vivo by positron emission tomography.

PURPOSE: Changes in GABA(A)-receptor density and affinity play an important role in many forms of epilepsy. A novel approach, using positron emission tomography (PET) and [C-11]flumazenil ([C-11]FMZ), was developed for simultaneous estimation of GABA(A)-receptor properties, characterized by B (max) and K (D). PROCEDURES: Following an injection of [C-11]FMZ (dose range: 1-2,000 mug) to 21 rats, concentration time curves of FMZ in brain (using PET) and blood (using HPLC-UV) were analyzed simultaneously using a population pharmacokinetic (PK) model, containing expressions to describe the time course of the plasma concentration (including distribution to the body), the brain distribution, and the specific binding within the brain. RESULTS: Application of this method in control rats resulted in estimates of B (max) and K (D) (14.5 +/- 3.7 ng/ml and 4.68 +/- 1.5 ng/ml, respectively). CONCLUSIONS: The proposed population PK model allowed for simultaneous estimation of B (max) and K (D) for a group of animals using single injection PET experiments per animal.

Pharmacokinetics and safety of single doses of drisapersen in non-ambulant subjects with Duchenne muscular dystrophy: results of a double-blind randomized clinical trial.

Duchenne muscular dystrophy (DMD) is a progressive, lethal neuromuscular disorder caused by the absence of dystrophin protein due to mutations of the dystrophin gene. Drisapersen is a 2'-O-methyl-phosphorothioate oligonucleotide designed to skip exon 51 in dystrophin pre-mRNA to restore the reading frame of the mRNA. This study assessed safety, tolerability, and pharmacokinetics of drisapersen after a single subcutaneous administration in non-ambulatory subjects. Eligible subjects were non-ambulant boys aged ⩾9years, in wheelchairs for ⩾1 to ⩽4years, with a diagnosis of DMD resulting from a mutation correctable by drisapersen treatment. Four dose cohorts were planned (3, 6, 9 and 12mg/kg), but study objectives were met with the 9mg/kg dose. Less than proportional increase in exposure was demonstrated over the 3-9mg/kg dose range, though post hoc analysis showed dose proportionality was more feasible over the 3-6mg/kg range. Single doses of drisapersen at 3 and 6mg/kg did not result in significant safety or tolerability concerns; however, at the 9mg/kg dose, pyrexia and transient elevations in inflammatory parameters were seen. The maximum tolerated dose of 6mg/kg drisapersen was identified for further characterization in multiple dose studies in the non-ambulant DMD population.

The Dynamics of Compound, Transcript, and Protein Effects After Treatment With 2OMePS Antisense Oligonucleotides in mdx Mice.

Antisense-mediated exon skipping is currently in clinical development for Duchenne muscular dystrophy (DMD) to amend the consequences of the underlying genetic defect and restore dystrophin expression. Due to turnover of compound, transcript, and protein, chronic treatment with effector molecules (antisense oligonucleotides) will be required. To investigate the dynamics and persistence of antisense 2'-O-methyl phosphorothioate oligonucleotides, exon skipping, and dystrophin expression after dosing was concluded, mdx mice were treated subcutaneously for 8 weeks with 100 mg/kg oligonucleotides twice weekly. Thereafter, mice were sacrificed at different time points after the final injection (36 hours-24 weeks). Oligonucleotide half-life was longer in heart (~65 days) compared with that in skeletal muscle, liver, and kidney (~35 days). Exon skipping half-lives varied between 33 and 53 days, whereas dystrophin protein showed a long half-life (>100 days). Oligonucleotide and exon-skipping levels peaked in the first week and declined thereafter. By contrast, dystrophin expression peaked after 3-8 weeks and then slowly declined, remaining detectable after 24 weeks. Concordance between levels of oligonucleotides, exon skipping, and proteins was observed, except in heart, wherein high oligonucleotide levels but low exon skipping and dystrophin expression were seen. Overall, these results enhance our understanding of the pharmacokinetics and pharmacodynamics of 2'-O-methyl phosphorothioate oligos used for the treatment of DMD.Molecular Therapy-Nucleic Acids (2014) 3, e148; doi:10.1038/mtna.2014.1; published online 18 February 2014.

Safety and efficacy of drisapersen for the treatment of Duchenne muscular dystrophy (DEMAND II): an exploratory, randomised, placebo-controlled phase 2 study.

BACKGROUND: Duchenne muscular dystrophy is caused by dystrophin deficiency and muscle deterioration and preferentially affects boys. Antisense-oligonucleotide-induced exon skipping allows synthesis of partially functional dystrophin. We investigated the efficacy and safety of drisapersen, a 2'-O-methyl-phosphorothioate antisense oligonucleotide, given for 48 weeks. METHODS: In this exploratory, double-blind, placebo-controlled study we recruited male patients (≥5 years of age; time to rise from floor ≤7 s) with Duchenne muscular dystrophy from 13 specialist centres in nine countries between Sept 1, 2010, and Sept 12, 2012. By use of a computer-generated randomisation sequence, we randomly allocated patients (2:2:1:1; block size of six; no stratification) to drisapersen 6 mg/kg or placebo, each given subcutaneously and either continuously (once weekly) or intermittently (nine doses over 10 weeks). The primary endpoint was change in 6-min walk distance (6MWD) at week 25 in patients in the intention-to-treat population for whom data were available. Safety assessments included renal, hepatic, and haematological monitoring and recording of adverse events. This trial is registered with ClinicalTrials.gov, number NCT01153932. FINDINGS: We recruited 53 patients: 18 were given continuous drisapersen, 17 were given intermittent drisapersen, and 18 were given placebo (continuous and intermittent groups combined). At week 25, mean 6MWD had increased by 31·5 m (SE 9·8) from baseline for continuous drisapersen, with a mean difference in change from baseline of 35·09 m (95% CI 7·59 to 62·60; p=0·014) versus placebo. We recorded no difference in 6MWD changes from baseline between intermittent drisapersen (mean change -0·1 [SE 10·3]) and placebo (mean difference 3·51 m [-24·34 to 31·35]) at week 25. The most common adverse events in drisapersen-treated patients were injection-site reactions (14 patients given continuous drisapersen, 15 patients given intermittent drisapersen, and six given placebo) and renal events (13 for continuous drisapersen, 12 for intermittent drisapersen, and seven for placebo), most of which were subclinical proteinuria. None of the serious adverse events reported (one for continuous, two for intermittent, and two for placebo) resulted in withdrawal from the study. INTERPRETATION: Continuous drisapersen resulted in some benefit in 6MWD versus placebo at week 25. The safety findings are similar to those from previous studies. Ambulation improvements in this young population with early-stage Duchenne muscular dystrophy are encouraging but need to be confirmed in larger studies. FUNDING: GlaxoSmithKline, Prosensa Therapeutics BV (a subsidiary of Prosensa Holding NV).

Decreased Efficacy of GABAA-receptor modulation by midazolam in the kainate model of temporal lobe epilepsy.

PURPOSE: The objective of this investigation was to characterize quantitatively the time-dependent changes in midazolam (MDL) efficacy in the silent period after induction of status epilepticus (SE) in rats. The changes in MDL efficacy were correlated to changes in ex vivo GABA(A)-receptor expression. METHODS: MDL efficacy was quantified by pharmacokinetic-pharmacodynamic (PK-PD) modeling by using the beta-frequency of the EEG as PD end point. Two PK-PD experiments were performed in each animal: the first experiment before and the second experiment at either day 4 or day 14 after SE. SE was induced by repetitive intraperitoneal injections with kainate. GABA(A)-receptor expression was determined by ex vivo autoradiography with [(3)H]flumazenil. RESULTS: The concentration versus EEG effect relation of midazolam was successfully described by the sigmoidal E(max) model. The maximal effect on the beta-frequency of the EEG (E(max)) was reduced to 51.6 +/- 35.6% and 25.8 +/- 33.7% of the original value at 4 and 14 days after induction of SE. The ex vivo study with [(3)H]flumazenil showed that the observed reductions in E(max) were paralleled by a reduction in GABA(A)-receptor density. CONCLUSIONS: The efficacy of MDL is decreased in the silent period after SE, which can be partly accounted for by a reduction in GABA(A)-receptor density.