Population pharmacokinetics of naloxegol in a population of 1247 healthy subjects and patients

Aims

Naloxegol, a polyethylene glycol conjugated derivative of the opioid antagonist naloxone, is in clinical development for treatment of opioid‐induced constipation (OIC).The aim of the study was to develop a population pharmacokinetic model describing the concentration vs. time profile of orally administered naloxegol, and determine the impact of pre‐specified demographic and clinical factors and concomitant medication on population estimates of apparent clearance (CL/F) and apparent central compartment volume of distribution (V _c/F).

Methods

Analysis included 12 844 naloxegol plasma concentrations obtained from 1247 healthy subjects, patients with non‐OIC and patients with OIC in 14 phase 1, 2b and 3 clinical studies. Pharmacokinetic analysis used the non‐linear mixed effects modelling program. Goodness of fit plots and posterior predictive checks were conducted to confirm concordance with observed data.

Results

The final model was a two compartment disposition model with dual absorptions, comprising one first order absorption (k _a1 4.56 h⁻¹) and one more complex absorption with a transit compartment (k _tr 2.78 h⁻¹). Mean (SE) parameter estimates for CL/F and V _c/F, the parameters assessed for covariate effects, were 115 (3.41) l h^–1 and 160 (27.4) l, respectively. Inter‐individual variability was 48% and 51%, respectively. Phase of study, gender, race, concomitant strong or moderate CYP3A4 inhibitors, strong CYP3A4 inducers, P‐glycoprotein inhibitors or inducers, naloxegol formulation, baseline creatinine clearance and baseline opioid dose had a significant effect on at least one pharmacokinetic parameter. Simulations indicated concomitant strong CYP3A4 inhibitors or inducers had relevant effects on naloxegol exposure.

Conclusions

Administration of strong CYP3A4 inhibitors or inducers had a clinically relevant influence on naloxegol pharmacokinetics.     

A pharmacokinetic comparison of anrukinzumab,an anti- IL-13 monoclonal antibody,among healthy volunteers,asthma and ulcerative colitis patients

AimsAnrukinzumab is an anti-IL13 monoclonal antibody. The goals of this study are to characterize the pharmacokinetics of anrukinzumab in healthy volunteers and different disease states and to identify covariates.MethodsA population pharmacokinetic (PK) model was developed in NONMEM, using data from five clinical studies including healthy volunteers, asthma and ulcerative colitis (UC) patients. Different dosing regimens including different routes of administration were also included in the data.ResultsThe PK of anrukinzumab were described by a two compartment model with first order absorption and elimination. The population estimates (relative standard error) of the volumes of distribution in the central (V_c) and peripheral (V_p) compartments were 3.8 (4.6%) and 2.2 l (8.7%), respectively. In non-UC patients, the population estimate of the systemic clearance (CL) and inter-compartmental CL was 0.00732 l h^–1 (4.9%) and 0.0224 l h^–1 (15.4%). For subcutaneous administration, the absorption rate constant was 0.012 h^–1 (6.6%) and bioavailability was nearly 100% in healthy and mild to moderate asthma patients. Both V and CL increased with body weight. CL (but not V) decreased with increasing baseline albumin concentrations. UC patients had an increased CL of 72.3% (10.5%), after correction for differences in body weight and albumin. Moderate to severe asthma patients had decreased bioavailability compared with other populations.ConclusionsAnrukinzumab''s PK behave like a typical antibody. UC patients were identified to have a faster CL of anrukinzumab than healthy volunteers and asthma patients. This finding suggests a higher dose level may be required for this population.     

Antisense‐mediated reduction of proprotein convertase subtilisin/kexin type 9 (PCSK9): a first‐in‐human randomized,placebo‐controlled trial

AimsLDL‐receptor expression is inhibited by the protease proprotein convertase subtilisin/kexin type 9 (PCSK9), which is considered a pharmacological target to reduce LDL‐C concentrations in hypercholesterolaemic patients. We performed a first‐in‐human trial with SPC5001, a locked nucleic acid antisense inhibitor of PCSK9.MethodsIn this randomized, placebo‐controlled trial, 24 healthy volunteers received three weekly subcutaneous administrations of SPC5001 (0.5, 1.5 or 5 mg kg^–1) or placebo (SPC5001 : placebo ratio 6 : 2). End points were safety/tolerability, pharmacokinetics and efficacy of SPC5001.ResultsSPC5001 plasma exposure (AUC(0,24 h)) increased more than dose‐proportionally. At 5 mg kg^–1, SPC5001 decreased target protein PCSK9 (day 15 to day 35: −49% vs. placebo, P < 0.0001), resulting in a reduction in LDL‐C concentrations (maximal estimated difference at day 28 compared with placebo −0.72 mmol l^–1, 95% confidence interval − 1.24, −0.16 mmol l^–1; P < 0.01). SPC5001 treatment (5 mg kg^–1) also decreased ApoB (P = 0.04) and increased ApoA1 (P = 0.05). SPC5001 administration dose‐dependently induced mild to moderate injection site reactions in 44% of the subjects, and transient increases in serum creatinine of ≥20 μmol l^–1 (15%) over baseline with signs of renal tubular toxicity in four out of six subjects at the highest dose level. One subject developed biopsy‐proven acute tubular necrosis.ConclusionsSPC5001 treatment dose‐dependently inhibited PCSK9 and decreased LDL‐C concentrations, demonstrating human proof‐of‐pharmacology. However, SPC5001 caused mild to moderate injection site reactions and renal tubular toxicity, and clinical development of SPC5001 was terminated. Our findings underline the need for better understanding of the molecular mechanisms behind the side effects of compounds such as SPC5001, and for sensitive and relevant renal toxicity monitoring in future oligonucleotide studies.     

Bevacizumab dosing strategy in paediatric cancer patients based on population pharmacokinetic analysis with external validation

Aim

The aim of the present study was to evaluate the pharmacokinetics of bevacizumab and various dosing strategies for this agent in paediatric patients.

Methods

Data were collected from 232 paediatric patients (1971 concentrations) in five studies, with a wide range of age (0.5 – 21 years), body weight (BWT; 5.9 – 125 kg), and regimens (5 – 15 mg kg^–1 biweekly or triweekly). Data from 152 patients (1427 concentrations) and 80 patients (544 concentrations) were used for model building and external validation, respectively. Steady‐state exposure was simulated under BWT‐based, body surface area (BSA)‐based, ideal body weight (IBW)‐based, and tier‐based doses. NONMEM and R were used for analyses.

Results

Typical estimates of clearance, central volume of distribution (V1), and median half‐life were 9.04 ml h^–1, 2851 ml, and 19.6 days, respectively. Clearance decreased with increasing albumin. Clearance and V1 increased with BWT and were higher in male patients. Clearance and V1 were lower in children with primary central nervous system (CNS) tumours than in children with sarcomas, resulting in 49% higher trough (Cmin) and 29% higher peak (Cmax) concentrations. BWT‐adjusted clearance and V1 remained unchanged across ages. Paediatric Cmin was similar to adult Cmin under all dosing strategies. Paediatric Cmax exceeded adult Cmax under tier‐based doses.

Conclusions

BWT‐adjusted pharmacokinetic parameter estimates in paediatric patients were similar to those in adults, and similar across ages. Bevacizumab exposure was higher in children with primary CNS tumours than in children with sarcomas. BSA‐based, IBW‐based, and tier‐based doses offered no substantial advantage over the BWT‐based dose currently used in adults for bevacizumab. Given the similarity in pharmacokinetics among many monoclonal antibodies, this may help to develop practical paediatric dosing guidelines for other therapeutic antibodies.     

Population pharmacokinetic study of gentamicin in a large cohort of premature and term neonates

AimThis study aims to investigate the clinical and demographic factors influencing gentamicin pharmacokinetics in a large cohort of unselected premature and term newborns and to evaluate optimal regimens in this population.MethodsAll gentamicin concentration data, along with clinical and demographic characteristics, were retrieved from medical charts in a Neonatal Intensive Care Unit over 5 years within the frame of a routine therapeutic drug monitoring programme. Data were described using non-linear mixed-effects regression analysis ( nonmem®).ResultsA total of 3039 gentamicin concentrations collected in 994 preterm and 455 term newborns were included in the analysis. A two compartment model best characterized gentamicin disposition. The average parameter estimates, for a median body weight of 2170 g, were clearance (CL) 0.089 l h⁻¹ (CV 28%), central volume of distribution (V_c) 0.908 l (CV 18%), intercompartmental clearance (Q) 0.157 l h⁻¹ and peripheral volume of distribution (V_p) 0.560 l. Body weight, gestational age and post-natal age positively influenced CL. Dopamine co-administration had a significant negative effect on CL, whereas the influence of indomethacin and furosemide was not significant. Both body weight and gestational age significantly influenced V_c. Model-based simulations confirmed that, compared with term neonates, preterm infants need higher doses, superior to 4 mg kg⁻¹, at extended intervals to achieve adequate concentrations.ConclusionsThis observational study conducted in a large cohort of newborns confirms the importance of body weight and gestational age for dosage adjustment. The model will serve to set up dosing recommendations and elaborate a Bayesian tool for dosage individualization based on concentration monitoring.     

Methnaridine is an orally bioavailable,fast‐killing and long‐acting antimalarial agent that cures Plasmodium infections in mice

Background and PurposeMalaria is one of the deadliest diseases in the world. Novel chemotherapeutic agents are urgently required to combat the widespread Plasmodium resistance to frontline drugs. Here, we report the discovery of a novel benzonaphthyridine antimalarial, methnaridine, which was identified using a structural optimization strategy.Experimental ApproachAn integrated pharmacological approach was used to evaluate the antimalarial profile of methnaridine. The pharmacokinetic properties of methnaridine were investigated along with the associated safety profile. Host immune response patterns were also analysed.Key ResultsMethnaridine exhibited potent antimalarial activity against P. falciparum (3D7: IC₅₀ = 0.0066 μM; Dd2: IC₅₀ = 0.0056 μM). In P. berghei‐infected mice, oral administration effectively suppressed parasitemia (ED₅₀ = 0.52 mg·kg⁻¹·day⁻¹) and cured the established infection (CD₅₀ = 10.13 mg·kg⁻¹·day⁻¹). These results are equivalent to or better than those of other antimalarial agents in clinical use. Notably, a four‐dose oral regimen at a dosage of 25 mg·kg⁻¹ achieved a complete cure of P. berghei infection in mice. Methnaridine exhibited a rapid parasiticidal profile (PCT₉₉ = 36.0 h) and showed no cross‐resistance to chloroquine. Pharmacokinetic studies revealed that methnaridine is readily absorbed, long‐lasting and slowly cleared. The safety profile of methnaridine is also satisfactory (maximum tolerated dose = 1,125 mg·kg⁻¹). In addition, following methnaridine treatment, infection‐induced Th1 immune response was almost fully alleviated in mice.Conclusion and ImplicationsMethnaridine is an orally bioavailable, fast‐acting and long‐lasting agent with excellent antimalarial properties. Our study highlights the potential of methnaridine for clinical development as a promising antimalarial candidate.     

Population pharmacokinetics of edoxaban in patients with symptomatic deep‐vein thrombosis and/or pulmonary embolism—the Hokusai‐VTE phase 3 study

AimsThis study characterized the population pharmacokinetics of edoxaban in patients with symptomatic deep‐vein thrombosis and/or pulmonary embolism in the Hokusai‐VTE phase 3 study. The impact of the protocol‐specified 50% dose reductions applied to patients with body weight ≤ 60 kg, creatinine clearance (CL_cr) of 30 to 50 ml min^–1 or concomitant P‐glycoprotein inhibitor on edoxaban exposure was assessed using simulations.MethodsThe sparse data from Hokusai‐VTE, 9531 concentrations collected from 3707 patients, were pooled with data from 13 phase 1 studies. In the analysis, the covariate relationships used for dose reductions were estimated and differences between healthy subjects and patients as well as additional covariate effects of age, race and gender were explored based on statistical and clinical significance.ResultsA linear two‐compartment model with first order absorption preceded by a lag time best described the data. Allometrically scaled body weight was included on disposition parameters. Apparent clearance was parameterized as non‐renal and renal. The latter increased non‐linearly with increasing CL_cr. Compared with healthy volunteers, inter‐compartmental clearance and the CL_cr covariate effect were different in patients (+64.6% and +274%). Asian patients had a 22.6% increased apparent central volume of distribution. The effect of co‐administration of P‐glycoprotein inhibitors seen in phase 1 could not be confirmed in the phase 3 data. Model‐based simulations revealed lower exposure in dose‐reduced compared with non‐dose‐reduced patients.ConclusionsThe adopted dose‐reduction strategy resulted in reduced exposure compared with non‐dose‐reduced, thereby overcompensating for covariate effects. The clinical impact of these differences on safety and efficacy remains to be evaluated.     

Evaluation of effect of impaired renal function on lamivudine pharmacokinetics

Aims

This study aimed to describe lamivudine pharmacokinetics in patients with impaired renal function and to evaluate the consistency of current dosing recommendations.

Methods

A total of 244 patients, ranging in age from 18 to 79 years (median 40 years) and in bodyweight from 38 to 117 kg (median 71 kg), with 344 lamivudine plasma concentrations, were analysed using a population pharmacokinetic analysis. Serum creatinine clearance (CLCR) was calculated using the Cockcroft–Gault formula; 177 patients had normal renal function (CLCR > 90 ml min⁻¹), 50 patients had mild renal impairment (CLCR = 60–90 ml min⁻¹), 20 patients had moderate renal impairment (CLCR = 30–60 ml min⁻¹), and five patients had severe renal impairment (CLCR < 30 ml min⁻¹).

Results

A two-compartment model adequately described the data. Typical population estimates (percentage interindividual variability) of the apparent clearance (CL/F), central (V_c/F) and peripheral volumes of distribution (V_p/F), intercompartmental clearance (Q/F) and absorption rate constant (K_a) were 29.7 l h⁻¹ (32%), 68.2 l, 114 l, 10.1 l h⁻¹ (85%) and 1 h⁻¹, respectively. Clearance increased significantly and gradually with CLCR. Our simulations showed that a dose of 300 mg day⁻¹ in patients with mild renal impairment could overexpose them. A dose of 200 mg day⁻¹ maintained an exposure close to that of adults with normal renal function. However, the current US Food and Drug Administration recommendations for lamivudine in other categories of patients (from severe to moderate renal impairment) provided optimal exposures.

Conclusions

Lamivudine elimination clearance is related to renal function. To provide optimal exposure, patients with mild renal impairment should receive 200 mg day⁻¹ instead of 300 mg day⁻¹.     

Alkali replacement raises urinary citrate excretion in patients with topiramate‐induced hypocitraturia

Aims

The aims of this study were to assess (1) the magnitude and temporality of decreased urinary citrate excretion in patients just starting topiramate and (2) the effect of alkali replacement on topiramate‐induced hypocitraturia.

Methods

Study 1 was a prospective, non‐intervention study in which patients starting topiramate for headache remediation provided pre‐ and post‐topiramate 24 h urine collections for measurement of urine citrate. Study 2 was a clinical comparative effectiveness study in which patients reporting to our stone clinic for kidney stones and who were treated with topiramate were prescribed alkali therapy. Pre‐ and post‐alkali 24 h urinary citrate excretion was compared.

Results

Data for 12 and 22 patients (studies 1 and 2 respectively) were evaluated. After starting topiramate, urinary citrate excretion dropped significantly by 30 days (P = 0.016) and 62% of patients had hypocitraturia (citrate <320 mg day^–1). At 60 days, urine citrate was even lower than at baseline (P = 0.0032) and 86% of patients had developed hypocitraturia. After starting alkali, urine citrate increased in stone‐forming patients on topiramate (198 ± 120 to 408 ± 274 mg day^–1; P = 0.042 for difference). 85% of patients were hypocitraturic on topiramate alone vs. 40% after adding alkali. The increase in urinary citrate was greater in patients provided ≥90 mEq potassium citrate.

Conclusions

Our study is the first to provide clinical evidence that alkali therapy can raise urinary citrate excretion in patients who form kidney stones while being treated with topiramate. Clinicians should consider alkali therapy for reducing the kidney stone risk of patients benefitting from topiramate treatment for migraine headaches or other conditions.     

Personalizing initial calcineurin inhibitor dosing by adjusting to donor CYP3A‐status in liver transplant patients

AimsInter‐individual variability in dose requirements of calcineurin inhibitors (CNI) has been linked to genetic polymorphisms of CYP3A enzymes. CYP3A5*3, CYP3A4*1B and CYP3A4*22 alleles of liver grafts may explain about one third of the inter‐individual differences in pharmacokinetics of ciclosporin and tacrolimus in recipients. However, non‐genetic factors, influencing CYP3A expression, can contribute to the variability of CYP3A function due to phenoconversion. The present study evaluated the association between CYP3A4 expression combined with CYP3A5 genotype of donor livers and recipients'' CNI therapy after transplantation.MethodsThe contribution of donors'' CYP3A5 genotype and CYP3A4 expression to the blood concentrations and dose requirements of CNIs was evaluated in 131 liver transplant recipients.ResultsThe recipients with grafts from normal CYP3A4 expresser donors carrying CYP3A5*3/*3 required CNI maintenance doses more or less similar to the bodyweight‐controlled starting doses (9.1 mg kg⁻¹ of ciclosporin and 0.1 mg kg⁻¹ of tacrolimus). The patients transplanted with grafts from low CYP3A4 expressers required substantial reduction (by about 50%, 4.2 mg kg⁻¹ of ciclosporin, 0.047 mg kg⁻¹ of tacrolimus, P < 0.001), while the recipients with grafts from high expressers or with grafts carrying at least one copy of the functional CYP3A5*1 allele required an increase (by about 50% [12.8–13.8 mg kg⁻¹] for ciclosporin and 100% [0.21 mg kg⁻¹] for tacrolimus, P < 0.001) of the initial CNI dose for achieving target blood concentrations.ConclusionsDonor livers'' CYP3A‐status, taking both CYP3A5 allelic variations and CYP3A4 expression into account, can better identify the risk of CNI over‐ or underexposure, and may contribute to the avoidance of misdosing‐induced graft injury in the early post‐operative period.     

Pharmacokinetics of tralokinumab in adolescents with asthma: implications for future dosing

AimsTralokinumab, an investigational human immunoglobulin G4 monoclonal antibody, potently and specifically neutralizes interleukin‐13, a central mediator of asthma. Tralokinumab has shown improvements in clinical endpoints in adults with uncontrolled asthma. The present study explored the pharmacokinetics (PK) and safety of a single tralokinumab dose, and utilized a population PK modelling and simulation approach to evaluate the optimal dosing strategy for adolescents.MethodsAdolescent subjects with asthma, using daily controller medication, received a single subcutaneous dose of tralokinumab 300 mg. Safety, immunogenicity and PK data were collected during a 57‐day follow‐up. A population PK model was developed using data from the present study and prior studies in adults. Simulations were performed to evaluate dose adjustment requirements for adolescents.ResultsTwenty adolescents (12–17 years) were enrolled; all completed the study. No clinically relevant safety findings or antidrug antibodies were detected. PK parameters were similar to those observed in adults. PK modelling showed that body weight was a minor predictor of tralokinumab PK; after incorporating body weight into the PK model, a 15% (nonparametric 95% confidence interval 5%, 26%) lower clearance was found in adolescents compared with adults [173 (151, 209) vs. 204 (191, 229) ml day^–1]. Simulations showed no therapeutically relevant differences in exposures between adolescent and adult populations, and similar PK profiles for weight‐based (4 mg kg^–1) and fixed (300 mg) fortnightly subcutaneous doses of tralokinumab.ConclusionSingle‐dose administration of tralokinumab 300 mg in adolescents was well tolerated, with a PK profile similar to that in adults. Exposure predictions suggest that dose adjustment is not required for adolescents.     

P2Y12 receptor blockade synergizes strongly with nitric oxide and prostacyclin to inhibit platelet activation

Aims In vivo platelet function is a product of intrinsic platelet reactivity, modifiable by dual antiplatelet therapy (DAPT), and the extrinsic inhibitory endothelial mediators, nitric oxide (NO) and prostacyclin (PGI₂), that are powerfully potentiated by P2Y₁₂ receptor blockade. This implies that for individual patients endothelial mediator production is an important determinant of DAPT effectiveness. Here, we have investigated this idea using platelets taken from healthy volunteers treated with anti‐platelet drugs.MethodsThree groups of male volunteers (n = 8) received either prasugrel (10 mg), aspirin (75 mg) or DAPT (prasugrel + aspirin) once daily for 7 days. Platelet reactivity in the presence of diethylammonium (Z)‐1‐(N,N‐diethylamino)diazen‐1‐ium‐1,2‐diolate (DEA/NONOate) and PGI₂ was studied before and following treatment.Results Ex vivo, PGI₂ and/or DEA/NONOate had little inhibitory effect on TRAP‐6‐induced platelet reactivity in control conditions. However, in the presence of DAPT, combination of DEA/NONOate + PGI₂ reduced platelet aggregation (74 ± 3% to 19 ± 6%, P < 0.05). In vitro studies showed even partial (25%) P2Y₁₂ receptor blockade produced a significant (67 ± 2% to 39 ± 10%, P < 0.05) inhibition when DEA/NONOate + PGI₂ was present.ConclusionsWe have demonstrated that PGI₂ and NO synergize with P2Y₁₂ receptor antagonists to produce powerful platelet inhibition. Furthermore, even with submaximal P2Y₁₂ blockade the presence of PGI₂ and NO greatly enhances platelet inhibition. Our findings highlight the importance of endothelial mediator in vivo modulation of P2Y₁₂ inhibition and introduces the concept of refining ex vivo platelet function testing by incorporating an assessment of endothelial function to predict thrombotic outcomes better and adjust therapy to prevent adverse outcomes in individual patients.     

Population pharmacokinetics of levamisole in children with steroid-sensitive nephrotic syndrome

Aim

The aim was to investigate the population pharmacokinetics of levamisole in children with steroid-sensitive nephrotic syndrome.

Methods

Non-linear mixed effects modelling was performed on samples collected during a randomized controlled trial. Samples were collected from children who were receiving 2.5 mg kg^–1 levamisole (or placebo) orally once every other day. One hundred and thirty-six plasma samples were collected from 38 children from India and Europe and included in the analysis. A one compartment model described the data well.

Results

The apparent clearance rate (CL/F) and distribution volume (V/F) were 44 l h^–1 70 kg^–1 and 236 l 70 kg^–1, respectively; estimated interindividual variability was 32–42%. In addition to allometric scaling of CL/F and V/F to body weight, we identified a significant proportional effect of age on CL/F (–10.1% per year). The pharmacokinetics parameters were not affected by gender, tablet strength or study centre. The median (interquartile range) maximum plasma concentration of levamisole was 438.3 (316.5–621.8) ng ml^–1, and the median area under the concentration–time curve was 2847 (2267–3761) ng ml^–1 h. Median t_max and t_½ values were 1.65 (1.32–2.0) h and 2.60 (2.06–3.65) h, respectively.

Conclusions

Here, we present the first pharmacokinetic data regarding levamisole in children with steroid-sensitive nephrotic syndrome. The pharmacokinetic profile of levamisole in children was similar to findings reported in adults, although the elimination rate was slightly higher in children.     

Pharmacokinetics and concentration–effect relationship of adalimumab in rheumatoid arthritis

Aims

This study aimed at describing adalimumab pharmacokinetics (PK) and the concentration–effect relationship of adalimumab using pharmacokinetic–pharmacodynamic (PK–PD) modelling in patients with rheumatoid arthritis (RA).

Methods

Adalimumab PK and PK–PD data were obtained from a multicentric observational study. Adalimumab (40 mg) was administered subcutaneously every other week, and its pharmacokinetics was described using a one-compartment model. The relationship between adalimumab concentration and C-reactive protein (CRP) concentration was described using an indirect response model with inhibition of CRP input, whereas the relationship between adalimumab concentration and disease activity score in 28 joints (DAS28) was described using a direct inhibition model. Dose regimens that included a loading dose of adalimumab were simulated.

Results

Thirty patients treated for RA were analysed. The following pharmacokinetic and PK–PD parameters were estimated (interidividual coefficient of variation): apparent volume of distribution (V_d/F) = 10.8 l (92%); apparent clearance (CL/F) = 0.32 l day⁻¹ (17%); first-order absorption rate (k_a) = 0.28 day⁻¹; CRP input (k_in) = 22.0 mg l⁻¹ day⁻¹ (65%); adalimumab concentration leading to a 50% decrease in k_in (C₅₀) = 3.6 mg l⁻¹ (88%); baseline DAS28 (DAS₀) = 5.5 mg l⁻¹ (11%); and adalimumab concentration leading to 50% decrease of DAS₀ (IC₅₀) = 11.0 mg l⁻¹ (71%). Simulations showed that a 160 mg loading dose should reduce the time to reach efficacy in terms of both CRP and DAS28 after the first injection.

Conclusions

This is the first study to describe adalimumab pharmacokinetics and the concentration–effect relationship in RA. A 160 mg loading dose may lead to an increased benefit from treatment in RA patients.     

Beating the odds: efficacy and toxicity of dihydropyrimidine dehydrogenase‐driven adaptive dosing of 5‐FU in patients with digestive cancer

Aims

5‐FU is the backbone of most regimens in digestive oncology. Administration of standard 5‐FU leads to 15–30% of severe side effects, and lethal toxicities are regularly reported with fluoropyrimidine drugs. Dihydropyrimidine dehydrogenase (DPD) deficiency is a pharmacogenetic syndrome responsible for most cases of life‐threatening toxicities upon 5‐FU intake, and pre‐treatment checking for DPD status should help to reduce both incidence and severity of side effects through adaptive dosing strategies.

Methods

We have used a simple method for rapidly establishing the DPD phenotype of patients with cancer and used it prospectively in 59 routine patients treated with 5‐FU‐based therapy for digestive cancers. No patient with total DPD deficiency was found but 23% of patients exhibited poor metabolizer phenotype, and one patient was phenotyped as profoundly deficient. Consequently, 5‐FU doses in poor metabolizer patients were cut by an average 35% as compared with non deficient patients (2390 ± 1225 mg vs. 3653 ± 1371 mg, P < 0.003, t‐test).

Results

Despite this marked reduction in 5‐FU dosing, similar efficacy was achieved in the two subsets (clinical benefit: 40 vs. 43%, stable disease: 40 vs. 37%, progressive disease: 20% in both subsets, P = 0.893, Pearson''s chi‐square). No difference in toxicities was observed (P = 0.104, Fisher''s exact test). Overall, only 3% of early severe toxicities were recorded, a value markedly lower than the 15‐30% ones usually reported with 5‐FU.

Conclusions

This feasibility study shows how simplified DPD‐based adaptive dosing of 5‐FU can reduce sharply the incidence of treatment‐related severe toxicities while maintaining efficacy as part of routine clinical practice in digestive oncology.     

Dried blood spots and sparse sampling: a practical approach to estimating pharmacokinetic parameters of caffeine in preterm infants

Aims

Dried blood spots (DBS) alongside micro‐analytical techniques are a potential solution to the challenges of performing pharmacokinetic (PK) studies in children. However, DBS methods have received little formal evaluation in clinical settings relevant to children. The aim of the present study was to determine a PK model for caffeine using a ‘DBS/microvolume platform’ in preterm infants.

Methods

DBS samples were collected prospectively from premature babies receiving caffeine for treatment of apnoea of prematurity. A non‐linear mixed effects approach was used to develop a population PK model from measured DBS caffeine concentrations. Caffeine PK parameter estimates based on DBS data were then compared with plasma estimates for agreement.

Results

Three hundred and thirty‐eight DBS cards for caffeine measurement were collected from 67 preterm infants (birth weight 0.6–2.11 kg). 88% of cards obtained were of acceptable quality and no child had more than 10 DBS samples or more than 0.5 ml of blood taken over the study period. There was good agreement between PK parameters estimated using caffeine concentrations from DBS samples (CL = 7.3 ml h⁻¹ kg⁻¹; V = 593 ml kg⁻¹; t_1/2 = 57 h) and historical caffeine PK parameter estimates based on plasma samples (CL = 4.9–7.9 ml h⁻¹ kg⁻¹; V = 640–970 ml kg⁻¹; t_1/2 = 101–144 h). We also found that changes in blood haematocrit may significantly confound estimates of caffeine PK parameters based on DBS data.

Conclusions

This study demonstrates that DBS methods can be applied to PK studies in a vulnerable population group and are a practical alternative to wet matrix sampling techniques.     

Pharmacokinetics of the Melanocortin Type 1 Receptor Agonist PL8177 After Subcutaneous Administration

Background and ObjectivePL8177 is a selective melanocortin 1 receptor agonist in development for the treatment of various immunologic and inflammatory conditions. Here we describe the pharmacokinetics of PL8177 after subcutaneous (sc) delivery in animals and humans.MethodsMice, rats, and dogs were administered sc PL8177 at single doses of 1.0 and 3.0 mg/kg (mice); 1.0, 5.0, and 25.0 mg/kg/day (rats); or 1.5, 8.0, and 40.0 mg/day (dogs). Blood was collected over 24 h (mice) or 28 days (rats and dogs). Safety and pharmacokinetics of single and multiple sc doses were also examined in human volunteers. Two dose levels were tested in two dosing cohorts of 1.0 and 3.0 mg/day for 7 days. Blood samples were collected through Day 1 and on Days 2 to 6 at peak and trough times based on analysis of the first two single-dose cohorts.ResultsIn mice, 3 mg/kg PL8177 resulted in an area under the plasma concentration–time curve from 0 to infinity (AUC_∞) of 1727 ng·h/mL, a maximum plasma concentration (C_max) of 2440 ng/mL, an elimination half-life (t_½) of 0.5 h, and a time to maximum concentration (t_max) of 0.25 h. Results for the 1-mg/kg dose were generally proportional. In rats, mean t_max values were independent of dose and ranged from 0.25 to 1.0 h for single and multiple dosing. C_max values ranged from 516 to 695 ng/mL (1-mg/kg dose) and from 666 to 1180 ng/mL (25-mg/kg dose). In dogs, mean t_max values ranged from 0.4 to 1.3 h for single and multiple dosing. Values for t_max decreased with increasing dose and mean plasma C_max increased less than dose proportionally (96–129 ng·h/mL [1.5 mg], 275–615 ng·h/mL [8.0 mg], and 633–1280 ng·h/mL [40.0 mg]). In humans, PL8177 was observed in the plasma within 15 min after a single dose and persisted for up to 48 h at higher doses. The t_max was 30–45 min (single dose) and 15–45 min (multiple doses). In multiple-dose studies, maximum steady-state plasma concentration (C_max,ss) and AUC_∞ increased with dose. Geometric mean C_max,ss values were 20.1 ng/mL (1.0 mg) and 57.2 ng/mL (3.0 mg). AUC_∞ values were 54.3 ng·h/mL (1.0 mg) and 199 ng·h/mL (3.0 mg). Unchanged PL8177 excreted in the urine was ≤ 1%, and accumulation was minimal.ConclusionPL8177 administration resulted in a consistent pharmacokinetic profile. The measured exposure levels resulted in pharmacologically active PL8177 concentrations at the targeted MC1R. Rapid absorption was seen in healthy volunteers, and multiple-dose administration over 7 days resulted in pharmacokinetic characteristics similar to those observed after single-dose administration. Results support the continued development of PL8177 to treat immunologic and inflammatory conditions.     

Population pharmacokinetics modeling of levetiracetam in Chinese children with epilepsy

Aim:

To establish a population pharmacokinetics (PPK) model of levetiracetam in Chinese children with epilepsy.

Methods:

A total of 418 samples from 361 epileptic children in Peking University First Hospital were analyzed. These patients were divided into two groups: the PPK model group (n=311) and the PPK validation group (n=50). Levetiracetam concentrations were determined by HPLC. The PPK model of levetiracetam was established using NONMEM, according to a one-compartment model with first-order absorption and elimination. To validate the model, the mean prediction error (MPE), mean squared prediction error (MSPE), root mean-squared prediction error (RMSPE), weight residues (WRES), and the 95% confidence intervals (95% CI) were calculated.

Results:

A regression equation of the basic model of levetiracetam was obtained, with clearance (CL/F)=0.988 L/h, volume of distribution (V/F)=12.3 L, and K_a=1.95 h⁻¹. The final model was as follows: K_a=1.56 h⁻¹, V/F=12.1 (L), CL/F=1.04×(WEIG/25)^0.583 (L/h). For the basic model, the MPE, MSPE, RMSPE, WRES, and the 95%CI were 9.834 (−0.587–197.720), 50.919 (0.012–1286.429), 1.680 (0.021–34.184), and 0.0621 (−1.100–1.980). For the final model, the MPE, MSPE, RMSPE, WRES, and the 95% CI were 0.199 (−0.369–0.563), 0.002082 (0.00001–0.01054), 0.0293 (0.001−0.110), and 0.153 (−0.030–1.950).

Conclusion:

A one-compartment model with first-order absorption adequately described the levetiracetam concentrations. Body weight was identified as a significant covariate for levetiracetam clearance in this study. This model will be valuable to facilitate individualized dosage regimens.     

A phase I study on pharmacokinetics and pharmacodynamics of higenamine in healthy Chinese subjects

Aim:

To investigate the pharmacokinetics, pharmacodynamics, and safety of higenamine, an active ingredient of Aconite root, in healthy Chinese volunteers.

Methods:

Ten subjects received continuous, intravenous infusion of higenamine at gradually escalating doses from 0.5 to 4.0 μg·kg⁻¹·min⁻¹, each dose was given for 3 min. Blood and urine samples were collected at designated time points to measure the concentrations of higenamine. Pharmacodynamics was assessed by measuring the subject''s heart rate. A nonlinear mixed-effect modeling approach, using the software Phoenix NLME, was used to model the plasma concentration-time profiles and heart rate.

Results:

Peak concentrations (C_max) of higenamine ranged from 15.1 to 44.0 ng/mL. The half-life of higenamine was 0.133 h (range, 0.107–0.166 h), while the area under concentration-time curve (AUC), extrapolated to infinity, was 5.39 ng·h·mL⁻¹ (range, 3.2-6.8 ng·h·mL⁻¹). The volume of distribution (V) was 48 L (range, 30.8–80.6 L). The total clearance (CL) was 249 L/h (range, 199-336 L/h). Within 8 h, 9.3% (range, 4.6%–12.4%) of higenamine was recovered in the urine. The pharmacokinetics of higenamine was successfully described using a two-compartment model with nonlinear clearance. In the pharmacodynamic model, heart rates were related to the plasma drug concentrations using a simple direct effect model with baseline. The E₀, E_max, and EC₅₀ were 68 bpm, 73 bpm and 8.1 μg/L, respectively.

Conclusion:

Higenamine has desirable pharmacokinetic and pharmacodynamic characteristics. The results provide important information for future clinical studies on higenamine.