A Chinese medicine called Danggui Longhui may be a new clinically relevant clozapine inducer: Two case reports identified by therapeutic drug monitoring.

BACKGROUND: Danggui Longhui is a traditional Chinese medicine made from the dried root of Angelica sinensis. It is used in psychiatric patients in China to reduce associated constipation. In a population pharmacokinetic model in olanzapine patients from Beijing Anding Hospital, we demonstrate that dangguilonghui tablets doubled olanzapine clearance, indicating the induction of olanzapine metabolism. Olanzapine metabolism is similar to clozapine metabolism. METHODS: Two cases of possible clozapine induction using dangguilonghui tablets 4 g/day were identified in Beijing Anding Hospital. Dividing the minimum therapeutic concentration of 350 ng/mL by the concentration-to-dose (C/D) ratio provides the minimum therapeutic dose. RESULTS: Case 1 was a female smoker on clozapine for 415 days. The mean of 6 clozapine C/D ratios associated with smoking provided a minimum therapeutic dose of 267 mg/day. There were 6 steady-state concentrations on the combination of valproic acid and dangguilonghui tablets, which provided a much higher minimum therapeutic dose of 833 mg/day. Four steady-state clozapine C/D ratios based on smoking and valproate after 4 months of carbamazepine 200 mg/day provided a minimum therapeutic dose of 603 mg/day. Case 2 was a female non-smoker on clozapine for 58 days. She had 3 clozapine C/D ratios on dangguilonghui tablets with a mean of 0.30 ng/mL providing a minimum therapeutic dose of 1167 mg/day. CONCLUSION: Future clinical studies with repeated measures need to replicate the possibility that dangguilonghui tablets are a moderate-to-strong inducer of clozapine metabolism as suggested by these two limited cases.

Population pharmacokinetics of Amisulpride in Chinese patients with schizophrenia with external validation: the impact of renal function.

Introduction: Amisulpride is primarily eliminated via the kidneys. Given the clear influence of renal clearance on plasma concentration, we aimed to explicitly examine the impact of renal function on amisulpride pharmacokinetics (PK) via population PK modelling and Monte Carlo simulations. Method: Plasma concentrations from 921 patients (776 in development and 145 in validation) were utilized. Results: Amisulpride PK could be described by a one-compartment model with linear elimination where estimated glomerular filtration rate, eGFR, had a significant influence on clearance. All PK parameters (estimate, RSE%) were precisely estimated: apparent volume of distribution (645 L, 18%), apparent clearance (60.5 L/h, 2%), absorption rate constant (0.106 h-1, 12%) and coefficient of renal function on clearance (0.817, 10%). No other significant covariate was found. The predictive performance of the model was externally validated. Covariate analysis showed an inverse relationship between eGFR and exposure, where subjects with eGFR= 30 mL/min/1.73 m2 had more than 2-fold increase in AUC, trough and peak concentration. Simulation results further illustrated that, given a dose of 800 mg, plasma concentrations of all patients with renal impairment would exceed 640 ng/mL. Discussion: Our work demonstrated the importance of renal function in amisulpride dose adjustment and provided a quantitative framework to guide individualized dosing for Chinese patients with schizophrenia.

The Impact of Smoking, Sex, Infection, and Comedication Administration on Oral Olanzapine: A Population Pharmacokinetic Model in Chinese Psychiatric Patients.

BACKGROUND AND OBJECTIVE: Prior olanzapine population pharmacokinetic (PPK) models have focused on the effects of sex and smoking on olanzapine clearance. This PPK model in Chinese adult psychiatric patients also investigated the influence of comedications and co-occurrence of infections on olanzapine clearance, and explored how to personalize oral olanzapine dosage in the clinical setting. METHODS: A total of 1546 serum concentrations from 354 patients were collected in this study. A one-compartment model with first-order absorption was employed to develop the PPK model using a nonlinear mixed-effects modeling approach. Covariates included demographic parameters, co-occurrence of infection and concomitant medications (including dangguilonghui tablets, a Chinese herbal medicine for constipation). Bootstrap validation (1000 runs) and external validation of 50 patients were employed to evaluate the final model. Simulations were performed to explore the personalization of olanzapine dosing after stratification by sex, smoking, and comedication with valproate. RESULTS: Typical estimates for the absorption rate constant (Ka), apparent clearance (CL/F), and apparent distribution volume (V/F) were 0.30 h-1, 12.88 L/h, and 754.41 L, respectively. Olanzapine clearance was increased by the following variables: 1.23-fold by male sex, 1.23-fold by smoking, 1.23-fold by comedication with valproate, 1.16-fold by sertraline, and 2.01-fold by dangguilonghui tablets. Olanzapine clearance was decreased by the following variables: 0.75-fold by co-occurrence of infection, 0.70-fold by fluvoxamine, and 0.78-fold by perphenazine. The model evaluation indicated that the final model's performance was good, stable, and precise. CONCLUSION: This study contributes to the personalization of oral olanzapine dosing, but further studies should be performed to verify the effects of infection and comedications, including valproate and dangguilonghui.

This study included a total of 1546 serum olanzapine concentrations from 354 Chinese adult psychiatric patients that were analyzed by a complex mathematical model. The goal was to explore how oral olanzapine is eliminated from the body in Chinese psychiatric patients and how to personalize its dosing. Prior studies using similar complex mathematical models only studied the effects of sex and smoking on olanzapine elimination. This study also investigated the influence of co-occurrence of infection and comedications, including dangguilonghui tablets. This is a Chinese herbal medicine used to treat constipation, including constipation secondary to olanzapine treatment. Olanzapine elimination was increased by the following variables: 1.23-fold by male sex, 1.23-fold by smoking, 1.23-fold by comedication with valproate, 1.16-fold by sertraline, and 2.01-fold by dangguilonghui tablets. Olanzapine elimination was decreased by the following variables: 0.75-fold by co-occurrence of infection, 0.70-fold by fluvoxamine, and 0.78-fold by perphenazine. This study contributes to the improvement of oral olanzapine dosing personalization, but further studies are needed to verify the effects of infection and comedications, including valproate and dangguilonghui.

Safety and tolerability of a single dose T0001 in Chinese healthy adult volunteers: a first-in-human ascending dose study

T0001 is the first mutant of etanercept with a higher affinity to tumor necrosis factor α (TNF-α) than etanercept. In order to investigate the safety and tolerability of T0001, a study was carried out in healthy Chinese subjects. A first-in-human, dose escalation study was conducted in healthy Chinese subjects. Fifty-six subjects were divided into six dose cohorts (10 mg, 20 mg, 35 mg, 50 mg, 65 mg and 75 mg) to receive a single subcutaneous injection of T0001. Safety and tolerability assessment were based on the records of vital signs, physical examinations, clinical laboratory tests, 12-lead electrocardiograms and adverse events (AEs). All subjects were in good compliance and none withdraw due to AEs. No serious AEs occurred. A total of twenty-three AEs in sixteen subjects were recorded, and eighteen of these AEs were believed to be related to T0001. The most frequently reported AEs were injection site reactions and white blood cell count increase. All these AEs were of mild to moderate intensity and most of them recovered spontaneously within 14 days. In this study, no dose-limiting toxicity was observed, and the maximum tolerated dose was identified as 75 mg. T0001 was considered safe and generally well tolerated at doses up to 75 mg in healthy Chinese volunteers

Population pharmacokinetic study of delayed methotrexate excretion in children with acute lymphoblastic leukemia
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OBJECTIVE: To investigate the population pharmacokinetics of delayed methotrexate (MTX) excretion in children with acute lymphoblastic leukemia (ALL). MATERIALS AND METHODS: A total of 1,659 plasma concentration samples of MTX from 190 patients with 1 - 4 courses (plasma concentrations > 0.1 µmol/L) were collected in this study. The data analysis was performed using Phoenix NLME 1.3 software. The covariates included age, body surface area (BSA), body weight, alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine transaminase (ALT), total bilirubin (TBIL), and serum creatinine (SCr). The final model was validated by bootstrap resampling procedures (1,000 runs) and visual predictive check (VPC) method. RESULTS: The data were best described by a two-compartment linear pharmacokinetic model. The mean values of clearance (CL) and distribution volume (Vd) of MTX were 6.53 L/h and 67.88 L, respectively. Analysis of covariates showed that BSA influenced the CL of MTX. CONCLUSION: The final model was demonstrated as appropriate and effective for assessing the pharmacokinetic parameters of delayed MTX excretion in children with ALL.

Clozapine Metabolism in East Asians and Caucasians: A Pilot Exploration of the Prevalence of Poor Metabolizers and a Systematic Review.

PURPOSE/BACKGROUND: In clozapine therapeutic drug monitoring (TDM) studies, Chinese reached the same concentrations using half the dosage Caucasians use. Defining clozapine poor metabolizers (PMs) requires stratification by ethnicity, smoking, and sex. METHODS/PROCEDURES: After sex and smoking stratification in 129 Chinese inpatients (mean, 8.8 TDM samples per patient), we explored the association between the total concentration-dose (C/D) ratio and CYP1A2 (*1C, *1F, and *7) and CYP2C19 alleles (*2 and *3). A systematic literature review identified 22 clozapine TDM prior studies (13 in Caucasians and 7 in East Asians). FINDINGS/RESULTS: In our Chinese sample, the mean total clozapine C/D ratio (ng/mL per mg/d) was 1.96 for 22 male smokers, 2.07 for 5 female smokers, 2.47 for 36 male nonsmokers, and 2.95 for 66 female nonsmokers. CYP1A2 *1C had no significant effects, and CYP1A2 *1F had small effects. Five clozapine PMs (4%) needed low clozapine doses of 75 to 115 mg/d to get therapeutic concentrations. Using the same methodology in a published Italian sample, we found 5 PMs (3.3% of 152). In the systematic review, the clozapine C/D ratio (ng/mL per mg/d) was higher when comparing: (1) weighted mean values of 1.57 in 876 East Asians versus 1.07 in 1147 Caucasians and (2) ranks of 8 East Asians versus 13 Caucasian samples (P < 0.001). IMPLICATIONS/CONCLUSIONS: Future TDM studies need to further explore the frequency of clozapine PMs after sex and smoking stratification in East Asian and Caucasian patients. Compared with Caucasians, East Asians appear to have a clinically relevant decrease in clozapine clearance.

Pharmacokinetics and immunogenicity of T0001, a newly developed anti-TNFα fusion protein, in healthy volunteers.

PURPOSE: T0001 was the first mutant of recombinant fusion protein of human tumor necrosis factor receptor and Fc fragment (rhTNFR:Fc) based on etanercept on a global scale. This study was carried out to investigate the pharmacokinetics (PK) and immunogenicity of T0001 in healthy Chinese volunteers. METHODS: This study was randomized, with a single ascending dose, and the first-in-human clinical trial of T0001. Healthy Chinese volunteers (n = 56; male: female = 1:1) were randomly assigned to receive a single subcutaneous (sc) injection of 10, 20, 35, 50, 65 or 75 mg of T0001. Blood samples were collected at designated time points after sc injection to assess immunogenicity and pharmacokinetics of T0001. RESULTS: During the study, no serious adverse events were observed. T0001 was slowly absorbed with a median Tmax of 84 h and slowly eliminated with a T1/2Z of 42.1-58.2 h. In the dose-exposure proportionality analysis, the estimated points for AUC0-∞ and Cmax were 0.87 with a 90% CI of 0.76-0.98 and 0.86 with a 90% CI of 0.74-0.97 respectively. The plasma concentration of free (unbound T0001) plasma TNFα and total (bound and unbound T0001) TNFα both increased significantly after the injection of T0001. Ten out of 56 volunteers (17.9%) tested positive for anti-drug antibodies (ADAs) at a low level. CONCLUSIONS: T0001 was safe and well-tolerated at doses up to 75 mg. Cmax and AUC0-∞ had an increasing tendency with dose levels, but we could not conclude that T0001 has linear PK properties in this study.

Population pharmacokinetics of lyophilized recombinant glucagon-like peptide-1 receptor agonist (recombinant exendin-4, rE-4) in Chinese patients with type 2 diabetes mellitus
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OBJECTIVE: To investigate the population pharmacokinetics of lyophilized recombinant glucagon-like peptide-1 receptor agonist (rE-4) in Chinese patients with type 2 diabetes mellitus (T2DM) for plasma concentration estimation and individualized treatment. METHODS: Twelve patients with T2DM were enrolled to receive subcutaneous injections of rE-4 at 5 µg twice daily for 84 days. Administration dosage was adjusted from 5 µg to 10 µg twice daily at day 29 in case of glycated albumin (GA) ≥ 17%. The population pharmacokinetic model was developed in the nonlinear mixed-effects modeling software NONMEM. RESULTS: The data were best described by a two-compartment model with first-order absorption and elimination. The outcome parameters were as follows: apparent clearance (CL/F) 6.67 L/h, apparent distribution volume of central compartment (Vc/F) 19.4 L, absorption rate constant (Ka) 1.39 h-1, apparent distribution volume of peripheral compartment (Vp/F) 22.6 L, intercompartmental clearance (Q/F) 1.28 L/h. The interindividual variabilities for CL/F, Vc/F, Ka, and Q/F were 64.4%, 57.7%, 45.5%, and 153.3%, respectively. The intra-individual variability of proportional error model was 41.7%. No covariate was screened out that showed significant influence on the model parameters. CONCLUSIONS: The established two-compartment model with first-order absorption and elimination successfully described the pharmacokinetic characteristics of rE-4 in Chinese patients with T2DM.
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Pharmacokinetic properties and safety profile of histamine dihydrochloride injection in Chinese healthy volunteers: a phase I, single-center, open-label, randomized study.

PURPOSE: Histamine dihydrochloride (HDC) injection has been approved in Europe for the treatment of adults with acute myeloid leukemia, used in combination therapy with the T-cell-derived cytokine interleukin-2. Despite years of clinical applications of HDC in Europe, no data are available on its tolerability and pharmacokinetic properties in Chinese patients. The objective of this study was to determine the safety profile and pharmacokinetic properties of HDC in Chinese healthy volunteers (HVs). METHODS: In this Phase I, single-center, open-label, randomized study, 20 Chinese HVs were randomized to receive a single dose of 0.5 or 1.0 mg HDC via a 10-minute subcutaneous injection. Whole-blood and urine samples were collected at designated time points after dosing. Plasma and urine concentrations of histamine and metabolite N-methyl histamine were measured using a validated HPLC-MS/MS method. Pharmacokinetic parameters were estimated through noncompartmental procedures based on concentration-time data. Adverse events and evaluation of clinical laboratory tests were used to assess the safety profile. The pharmacokinetic profile for a single-dose of 1.0 mg HDC in Chinese HVs was compared with that in Western HVs. FINDINGS: No severe adverse events occurred in this study, and the severity of all adverse events was grade I according to the Common Terminology Criteria for Adverse Events, version 4.0. For the pharmacokinetic parameters of histamine at the 0.5-mg and 1.0-mg dose levels, t½ was 0.50 and 1.02 hours; Tmax was 0.15 and 0.14 hours; mean Cmax was 26.59 and 71.01 nmol/L; AUC0-t was 8.35 and 20.43 nmol/h/L; AUC0-∞ was 9.61 and 22.69 nmol/h/L; accumulated amount excreted in urine within 24 hours was 125.93 and 145.52 nmol; and maximum urine excretion rates were 21.85 and 38.94 nmol/h, respectively. For N-methyl histamine at the 0.5-mg and 1.0-mg dose levels, t½ was 0.58 and 0.66 hours; Tmax was 0.28 and 0.26 hours; mean Cmax was 17.01 and 23.54 nmol/L; AUC0-t was 7.72 and 17.08 nmol/h/L; AUC0-∞ was 9.01 and 19.62 nmol/h/L; accumulated amount excreted in urine within 24 hours was 331.7 and 583.21 nmol; and maximum urine excretion rates were 53.29 and 133.53 nmol/h, respectively. IMPLICATIONS: Both single-dose 0.5 mg and 1.0 mg HDC were well tolerated in Chinese HVs, and the pharmacokinetic profile of HDC in Chinese HVs was characterized in this study. A single dose of 1.0 mg HDC had a more rapid but similar extent of absorption, a wider distribution, and a little more rapid elimination in Chinese HVs compared with Western HVs. Findings from this study support additional clinical trials for HDC using in Chinese patients. Chinese Clinical Trial Registry identifier: ChiCTR-ONC-13003954.