Population pharmacokinetic and pharmacokinetic-pharmacodynamic modeling of bempedoic acid and low-density lipoprotein cholesterol in healthy subjects and patients with dyslipidemia

Population pharmacokinetics (popPK) of bempedoic acid and the popPK/pharmacodynamic (popPK/PD) relationship between bempedoic acid concentrations and serum low-density lipoprotein cholesterol (LDL-C) from baseline were characterized. A two-compartment disposition model with a transit absorption compartment and linear elimination best described bempedoic acid oral pharmacokinetics (PK). Multiple covariates, including renal function, sex, and weight, had statistically significant effects on the predicted steady-state area under the curve. Mild (estimated glomerular filtration rate (eGFR) 60 to < 90 mL/min vs. ≥ 90 mL/min) and moderate (eGFR 30 to < 60 mL/min vs. ≥ 90 mL/min) renal impairment, female sex, low (< 70 kg vs. 70-100 kg) and high (> 100 kg vs. 70-100 kg) body weight were predicted to have a 1.36-fold (90% confidence interval (CI) 1.32, 1.41), 1.85-fold (90% CI 1.74, 2.00), 1.39-fold (90% CI 1.34, 1.47), 1.35-fold (90% CI 1.30, 1.41), and 0.75-fold (90% CI 0.72, 0.79) exposure difference relative to their reference populations, respectively. An indirect response model described changes in serum LDL-C with a model-predicted 35% maximal reduction and bempedoic acid IC50 of 3.17 µg/mL. A 28% reduction from LDL-C baseline was predicted for a steady-state average concentration of 12.5 µg/mL after bempedoic acid (180 mg/day) dosing, accounting for approximately 80% of the predicted maximal LDL-C reduction. Concurrent statin therapy, regardless of intensity, reduced the maximal effect of bempedoic acid but resulted in similar steady-state LDL-C levels. While multiple covariates had statistically significant effects on PK and LDL-C lowering, none were predicted to warrant bempedoic acid dose adjustment.

Development of a Population Pharmacokinetic Model for the Diroximel Fumarate Metabolites Monomethyl Fumarate and 2-Hydroxyethyl Succinimide Following Oral Administration of Diroximel Fumarate in Healthy Participants and Patients with Multiple Sclerosis

Introduction

Diroximel fumarate (DRF) is a next-generation oral fumarate that is indicated in the USA for relapsing forms of multiple sclerosis (MS). A joint population pharmacokinetic model was developed for the major active metabolite (monomethyl fumarate, MMF) and the major inactive metabolite (2-hydroxyethyl succinimide, HES) of DRF.

Methods

MMF and HES data were included from 341 healthy volunteers and 48 patients with MS across 11 phase I and III studies in which DRF was administered as single or multiple doses. Population modeling was performed with NONMEM version 7.3 with the first-order conditional estimation method.

Results

Estimated MMF clearance (CL_MMF), volume of distribution, and absorption rate constant (Ka) were 13.5 L/h, 30.4 L, and 5.04 h⁻¹, respectively. CL_MMF and HES clearance (CL_HES) increased with increasing body weight. CL_HES decreased with decreasing renal function. CL_MMF and CL_HES were 28% and 12% lower in patients with MS than in healthy volunteers, respectively. Ka was reduced in the presence of low-, medium-, and high-fat meals by 37%, 51%, and 67%, respectively, for MMF; and by 34%, 49%, and 62%, respectively, for HES.

Conclusions

Age, sex, race, and baseline liver function parameters such as total bilirubin, albumin, and aspartate aminotransferase were not considered to be significant predictors of MMF or HES disposition.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40120-021-00316-6.

Population Pharmacokinetics of Vixotrigine in Healthy Volunteers and Subjects with Trigeminal Neuralgia, Painful Lumbosacral Radiculopathy and Erythromelalgia

BACKGROUND

Vixotrigine is a voltage and use dependent sodium channel blocker currently under development for treatment of various neuropathic pain indications.

OBJECTIVE

The objective of this work was to develop a population pharmacokinetic model and assess effects of various covariates on pharmacokinetic parameters of vixotrigine.

METHOD

Plasma concentration-time data from 12 Phase 1 or 2 studies were included in the analyses. The data were obtained following administration of single or multiple doses of vixotrigine in healthy volunteers and patients. One- and two-compartment pharmacokinetic models were evaluated as base structural pharmacokinetic models. The inclusion of selected covariates was assessed using a stepwise backward elimination approach (α = 0.001) once the base/full model was developed. The predictive ability of the model was evaluated using a visual predictive check (VPC). The final model was used to evaluate effect of covariates on exposure of vixotrigine.

RESULTS

A total of 10,263 pharmacokinetic samples collected from 465 subjects were included in the analyses. The pharmacokinetics of vixotrigine was adequately described by a two-compartment model with two transit absorption compartments and first-order elimination. Predictability of the model was also established by VPC. The final model included covariates of age, weight and carbamazepine co-administration on clearance, weight on central volume of distribution, food on absorption rate constant and formulation and Japanese race on bioavailability. None of the covariates identified had a clinically relevant effect, as impact on area under the plasma concentration-time curve (AUC) and maximum plasma concentration (C_max) was within ± 25%.

CONCLUSION

The model characterizes the pharmacokinetics of vixotrigine well, and the exposure of vixotrigine was comparable between healthy subjects and patients. None of the covariates evaluated have a clinically relevant impact on the pharmacokinetics of vixotrigine.

Asenapine pharmacokinetics in hepatic and renal impairment

BACKGROUND AND OBJECTIVE

The effects of hepatic or renal impairment on the pharmacokinetics of atypical antipsychotics are not well understood. Drug exposure may increase in patients with hepatic disease, owing to a reduction of certain metabolic enzymes. The objective of the present study was to study the effects of hepatic or renal impairment on the pharmacokinetics of asenapine and its N-desmethyl and N⁺-glucuronide metabolites.

METHODS

Two clinical studies were performed to assess exposure to asenapine, desmethylasenapine and asenapine N⁺-glucuronide in subjects with hepatic or renal impairment. Pharmacokinetic parameters were determined from plasma concentration-time data, using standard noncompartmental methods. The pharmacokinetic variables that were studied included the maximum plasma concentration (C(max)) and the time to reach the maximum plasma concentration (t(max)). Eligible subjects, from inpatient and outpatient clinics, were aged ≥18 years with a body mass index of ≥18 kg/m² and ≤32 kg/m². Sublingual asenapine (Saphris®) was administered as a single 5 mg dose.

RESULTS

Thirty subjects participated in the hepatic impairment study (normal hepatic function, n = 8; mild hepatic impairment [Child-Pugh class A], n = 8; moderate hepatic impairment [Child-Pugh class B], n = 8; severe hepatic impairment [Child-Pugh class C], n = 6). Thirty-three subjects were enrolled in the renal impairment study (normal renal function, n = 9; mild renal impairment, n = 8; moderate renal impairment, n = 8; severe renal impairment, n = 8). Asenapine and N-desmethylasenapine exposures were unaltered in subjects with mild or moderate hepatic impairment, compared with healthy controls. Severe hepatic impairment was associated with increased area under the plasma concentration-time curve from time zero to infinity (AUC(∞)) values for total asenapine, N-desmethylasenapine and asenapine N⁺-glucuronide (5-, 3-, and 2-fold, respectively), with slight increases in the C(max) of asenapine but 3- and 2-fold decreases in the C(max) values for N-desmethylasenapine and asenapine N⁺-glucuronide, respectively, compared with healthy controls. The mean AUC(∞) of unbound asenapine was more than 7-fold higher in subjects with severe hepatic impairment than in healthy controls. Mild renal impairment was associated with slight elevations in the AUC(∞) of asenapine compared with healthy controls; alterations observed with moderate and severe renal impairment were marginal. N-desmethylasenapine exposure was only slightly altered by renal impairment. No correlations were observed between exposure and creatinine clearance.

CONCLUSION

Severe hepatic impairment (Child-Pugh class C) was associated with pronounced increases in asenapine exposure, but significant increases were not seen with mild (Child-Pugh class A) or moderate (Child-Pugh class B) hepatic impairment, or with any degree of renal impairment. Asenapine is not recommended in patients with severe hepatic impairment; no dose adjustment is needed in patients with mild or moderate hepatic impairment, or in patients with renal impairment.

Relief of painful diabetic peripheral neuropathy with pregabalin: a randomized, placebo-controlled trial

This was a 6-week, randomized, double-blind, multicenter study evaluating the efficacy of pregabalin in the treatment of painful diabetic neuropathy. Two hundred forty-six men and women with painful diabetic neuropathy received pregabalin (150 or 600 mg/day by mouth) or placebo. The primary efficacy variable was mean pain score at the end of treatment. Efficacy results indicate that pregabalin 600 mg/day significantly decreased mean pain score to 4.3 (vs 5.6 for placebo, P = .0002) and increased the proportion of patients who had a > or =50% decrease from baseline pain (39% vs 15% for placebo, P = .002). Pregabalin also significantly reduced sleep interference, past week and present pain intensity, sensory and affective pain scores, and bodily pain and decreased by > or =50% the number of patients describing their pain as gnawing, sickening, fearful, and punishing-cruel. More patients receiving pregabalin 600 mg/day than placebo showed improvement, as rated on the Clinical and Patient Global Impression of Change scales, 73% vs 45% and 85% vs 47%, respectively. Pregabalin 150 mg/day was essentially no different from placebo. Dizziness was the most common side effect. These study results show pregabalin 600 mg/day to be safe and effective in reducing the pain and other associated symptoms of painful diabetic neuropathy.

PERSPECTIVE

Painful diabetic peripheral neuropathy is a challenging neuropathic pain syndrome. This randomized controlled trial demonstrates that pregabalin, a new drug that interacts with the alpha2-delta protein subunit of the voltage-gated calcium channel, is an efficacious and safe treatment for the pain of this condition.

Exposure-response analysis of pregabalin add-on treatment of patients with refractory partial seizures

OBJECTIVE

Our objectives were to describe the exposure-response relationship of pregabalin add-on treatment for refractory partial seizures after multiple dosing in patients and to identify the factors that influence this relationship.

METHODS

A mixed-effects model was used to characterize the relationship between monthly seizure frequency over a 3-month period and pregabalin daily dose (0, 50, 150, 300, and 600 mg) as add-on treatment in 3 double-blind, parallel-group studies in patients with refractory partial seizures (N = 1042). Seizure frequency was modeled as a Poisson process expressed as a function of baseline seizures, drug treatment, placebo effect, and subject-specific random effects. The model included a parameter that partitioned the population into subpopulations with respect to response.

RESULTS

Seventy-five percent of patients showed an asymptotic decrease in seizure frequency with increasing doses of pregabalin, whereas 25% did not demonstrate a significant decrease in seizure frequency from baseline. In patients who demonstrated a dose-related decrease in seizure frequency from baseline, the maximal percentage of seizure reduction from baseline was 100% for women and 80% for men, with a 186-mg daily dose decreasing seizures on average to 50% of maximum. Age, race, and menopausal status did not significantly affect seizure frequency.

CONCLUSION

Pregabalin add-on treatment demonstrates a dose-response relationship in 3 out of 4 patients with refractory partial seizures. A dose of 186 mg pregabalin daily is expected to decrease the seizure rate by 50% of maximum from baseline. Age, race, and menopausal status of women did not affect the dose-response relationship.

Pregabalin for the treatment of postherpetic neuralgia: a randomized, placebo-controlled trial

OBJECTIVE

To evaluate the efficacy and safety of pregabalin in the treatment of postherpetic neuralgia (PHN).

METHODS

The authors conducted a multicenter, parallel-group, double-blind, placebo-controlled, 8-week, randomized clinical trial in PHN, defined as pain for 3 or more months following herpes zoster rash healing. Patients (n = 173) were randomized to treatment with pregabalin or placebo. Patients randomized to pregabalin received either 600 mg/day (creatinine clearance > 60 mL/min) or 300 mg/day (creatinine clearance 30 to 60 mL/min). The primary efficacy measure was the mean of the last seven daily pain ratings. Secondary endpoints included additional pain ratings, sleep interference, quality of life, mood, and patient and clinician ratings of global improvement.

RESULTS

Pregabalin-treated patients had greater decreases in pain than patients treated with placebo (endpoint mean scores 3.60 vs 5.29, p = 0.0001). Pain was significantly reduced in the pregabalin-treated patients after the first full day of treatment and throughout the study, and significant improvement on the McGill Pain Questionnaire total, sensory, and affective pain scores was also found. The proportions of patients with >or=30% and >or=50% decreases in mean pain scores were greater in the pregabalin than in the placebo group (63% vs 25% and 50% vs 20%, p = 0.001). Sleep also improved in patients treated with pregabalin compared to placebo (p = 0.0001). Both patients and clinicians were more likely to report global improvement with pregabalin than placebo (p = 0.001). Given the maximal dosage studied, pregabalin had acceptable tolerability compared to placebo despite a greater incidence of side effects, which were generally mild to moderate in intensity.

CONCLUSIONS

Treatment of PHN with pregabalin is safe, efficacious in relieving pain and sleep interference, and associated with greater global improvement than treatment with placebo.

Mucosal uptake of gabapentin (neurontin) vs. pregabalin in the small intestine

PURPOSE

To compare the mucosal membrane transport of gabapentin and pregabalin in animal small intestine.

METHODS

Uptake of the two drugs by brush-border membrane vesicles (BBMV) from rat and rabbit small intestine was studied as a function of temperature, uptake-medium sodium content, and intestinal region. Amino acid inhibition studies were conducted with pregabalin.

RESULTS

Gabapentin uptake by rat and rabbit jejunal BBMV was sodium independent, whereas pregabalin uptake was sodium dependent. Uptake of both drugs in rabbit small intestinal vesicles was greater at 25 degrees C than at 4 degrees C in the absence of sodium and an additional increase in uptake was observed for pregabalin at 25 degrees C in the presence of sodium. Pregabalin uptake in rabbit duodenal, jejunal, and ileal BBMV was equivalent, whereas gabapentin uptake was greater in duodenal and ileal BBMV, compared with jejunal BBMV. Although inhibition is weak, a decrease in BBMV uptake of pregabalin is observed with coincubation of high concentrations of both neutral and basic amino acids.

CONCLUSIONS

Amino acid carriers mediate the apical uptake of both drugs in the small intestine. Although gabapentin and pregabalin are structurally similar, their small intestinal mucosal uptake differs in sodium dependence and region dependence. Gabapentin uptake is likely mediated by system b0,+, whereas pregabalin uptake is also mediated by B0 and/or B0,+.

Impact of population pharmacokinetic-pharmacodynamic analyses on the drug development process: experience at Parke-Davis

BACKGROUND

Continued scepticism about the benefits of population pharmacokinetics and/or population pharmacodynamics, here referred to collectively as the population approach, hampers its widespread application in drug development. At the same time the sources of this scepticism have not been clearly defined. In an attempt to capture and clearly define these concerns and to help communicate the value of the population approach in drug development at Parke-Davis we conducted a survey of customers within the company. The results of this survey are presented here.

METHODS

All drug development programmes conducted over the past 10 years that included a population approach in data analysis and interpretation were identified. A brief description of the population analysis was prepared together with a brief description of how the resulting information was used in each drug development programme. These synopses were forwarded to relevant members of each drug development team together with a survey designed to solicit opinions as to the relevance and impact of these analyses.

RESULTS

The most frequent use of information derived from population-based analysis was in labelling. In all cases of drugs making to New Drug Application (NDA) submission the analyses resulted in information that was included in approved or proposed labelling. In almost half of the cases summarised here (5 of 12), population-based analysis was perceived to have resulted in information that influenced the direction of individual development programmes. In many of these cases the information was serendipitous. It is also noted that most of these analyses were not the result of clearly defined objectives and prospective analysis plans.

CONCLUSIONS

Use of the population approach, even when applied retrospectively, may have value in complementing or supporting interpretation of other data collected during the course of a trial. Atypical systemic exposure is quickly and easily assessed for correlation with adverse events or exceptional efficacy in retrospective or ad hoc evaluation. Although we know of no direct evidence, it is possible that such use of population pharmacokinetic data has facilitated NDA review and approval by providing insight into the role of atypical systemic drug exposure in otherwise spurious events.

Preclinical and phase 1 clinical characterization of CI-979/RU35926, a novel muscarinic agonist for the treatment of Alzheimer's disease

In vitro and in vivo characterization in rodents and monkeys shows that CI-979/RU35926 is a partial muscarinic agonist with equal affinity for the five subtypes of muscarinic receptors. It activates central cholinergic receptors as shown by its ability to decrease body temperature, enhance local cortical blood flow and increase cortical arousal measured by QEEG. Further, it reverses spatial memory deficits in rats with ibotenic acid-induced lesions of forebrain cholinergic neurons. Signs of peripheral cholinergic stimulation appear at doses higher or equal to those necessary to produce central activity. In a single-dose tolerance study in young, healthy human volunteers, CI-979/RU35926 was well tolerated at doses of 0.002-1.0 mg with cholinergic symptoms such as hypersalivation and sweating, observed at 2-4 mg. It demonstrated linear pharmacokinetic behavior over a dose range of 0.1 to 4 mg and elimination half-life varied from 2-5 hours. Measurement of unchanged drug in urine suggests that the drug was extensively metabolized. Thus, the safety profile supported further clinical evaluation and CI-979/RU35926 is currently in Phase II clinical trials.

Tandem-in-time mass spectrometry as a quantitative bioanalytical tool

Tandem-in-time mass spectrometry, as implemented on an ion-trap detector (ITD), is the process whereby precursor ions are created, stored in a radio frequency (rf) trapping field, and then sequentially fragmented to form product ions by application of additional rf waveforms. As with any form of tandem mass spectrometry (MS/MS), tandem-in-time MS is highly selective, by virtue of both mass discrimination and specific gas-phase chemistry. Beyond this, however, tandem-in-time MS offers ion throughput efficiency and cost advantages over either quadrupole or sector instruments. This paper will describe the use of capillary gas chromatography combined with tandem-in-time mass spectrometry to quantify a novel therapeutic agent extracted from human plasma. For an example compound, a quantitation limit of 25 pg/mL (S/N approximately 10, 15 fmol on-column) was attained out of plasma. The interday imprecision was < or = 12.2% over a dynamic range extending to 10 ng/mL. Due to favorable ionization conditions for the test analytes, electron ionization resulted in formation of M+ ions, with very little fragmentation, allowing for maximum assay sensitivity. Although method characterization and validation demonstrated adequate instrumental performance, some lack of ruggedness was encountered during routine application.

Safety and tolerability of CI-979 in patients with Alzheimer's disease

CI-979 ((E)-1,2,5,6-tetrahydro-1-methyl-3-pyridinecarboxaldehyde, O-methyloxime monohydrochloride), a novel muscarinic agonist, is being investigated as a potential treatment for Alzheimer's disease (AD). The objective of the present study was to determine the safety and tolerance of multiple, rising, oral doses of CI-979 in patients with AD. Ten male patients aged 59 to 74 years (mean 65 years) who met NINCDS criteria for AD were randomized to receive either CI-979 (eight patients) or placebo (two patients) according to a double-blind, parallel-group, rising-dose design. Doses were 0.5-mg q6h, 1-mg q12h, 1-mg q6h, 2-mg q12h, 2-mg q6h, 2.5-mg q6h, and 3-mg q6h. All doses were to be administered sequentially for 3 days each with the exception of the 2.5-mg q6h dose, which was to be administered for 1.5 days. Five patients receiving CI-979 discontinued study medication because of adverse events; two after receiving 2-mg q6h (10 doses), two after 2.5-mg q6h (5 doses), and one after 3-mg q6h (4 doses). The study was terminated following administration of the fourth 3-mg dose due to the nature and intensity of adverse events. Cholinergic symptoms including diaphoresis, hypersalivation, nausea, diarrhea, hypotension, chills, headache, flatulence, and urinary frequency and signs suggestive of parkinsonism (cogwheeling, tremor, pillrolling, posturing, and shuffling gait) were dose-limiting. The frequency and intensity of adverse events increased with increasing CI-979 dose. No other clinically significant CI-979-related changes occurred in physical examinations, clinical laboratory measurements, electrocardiograms, or ophthalmologic examinations. Steady-state trough plasma CI-979 concentrations increased in proportion to dose. In summary, CI-979 doses of 1-mg q6h were well tolerated by all patients; 2-mg q6h was tolerated by most patients, and 2.5-mg and 3-mg doses were poorly tolerated, Dose titration to a maximum of 2-mg q6h will therefore be used in initial efficacy trials of CI-979 in patients with AD.

Pharmacokinetics of gabapentin in subjects with various degrees of renal function

The pharmacokinetics of oral gabapentin (400 mg) was studied in normal subjects and in subjects with various degrees of renal function. Sixty subjects participated in this three-center study. None of the subjects were receiving hemodialysis. Plasma and urine samples were collected for up to 264 hours after dosing, and concentrations of gabapentin were determined by high performance liquid chromatography. Apparent oral plasma clearance (CL/F) and renal clearance (CLR) of gabapentin decreased and maximum plasma concentration, time to reach maximum concentration, and half-life values increased as renal function diminished. Gabapentin CL/F and CLR were linearly correlated with creatinine clearance. Total urinary recovery of unchanged drug was comparable in all subjects, indicating that the extent of drug absorption was unaffected by renal function. There was no evidence of gabapentin metabolism even in subjects with severe renal impairment. In summary, impaired renal function results in higher plasma gabapentin concentrations, longer elimination half-lives, and reduced CL/F and CLR values. Based on pharmacokinetic considerations, it appears that the dosing regimen of gabapentin in subjects with renal impairment may be adjusted on the basis of creatinine clearance.

Identification of a pyridinium metabolite in human urine following a single oral dose of 1-[2-[bis[4-(trifluoromethyl)phenyl]methoxy]ethyl]- 1,2,5,6-tetrahydro-3-pyridinecarboxylic acid monohydrochloride, a gamma-aminobutyric acid uptake inhibitor

Single-dose administration of 50 mg of 1-[2-[bis[4- (trifluoromethyl)phenyl]methoxy]ethyl]-1,2,5,6-tetrahydro-3- pyridinecarboxylic acid monohydrochloride resulted in temporary neurological and psychological symptoms in two subjects. Because of the nature of adverse effects, urine from a subject who received CI-966 orally was extracted to investigate the metabolism of CI-966 in man. An unknown urinary component was identified as a pyridinium metabolite of CI-966 based on HPLC-MS and 1H and 19F NMR. Structural confirmation was achieved by chromatographic and spectroscopic comparisons to a reference standard. In several in vitro screens and preclinical studies, the pyridinium metabolite appears to possess minimal pharmacological activity.

Quantitative whole-body autoradiographic determination of tacrine tissue distribution in rats following intravenous or oral dose

Tacrine (1,2,3,4-tetrahydro-9-acridinamine) has been employed in diverse clinical situations but has recently been of considerable interest for the treatment of cognitive deficits associated with senile dementia (Alzheimer's disease). The present studies examined tissue distribution of radiolabeled tacrine by quantitative whole-body autoradiography. Tacrine radioequivalents were widely distributed to tissue following iv or peroral dose, with an apparently prolonged absorption phase following po dose. The presence of high levels of activity in kidneys and ureters indicates a major role for urinary excretion, but there is also evidence for biliary excretion and direct secretion of compound or metabolites into the intestinal lumen. Tacrine was rapidly taken up into the brain and demonstrated regional localization to cortex, hippocampus, thalamus, and striatum. Although the inhibition of acetylcholinesterase by tacrine is well documented, regional uptake in brain did not correlate consistently with distribution of the enzyme, supporting suggestions by others that the alleged action of tacrine in treatment of senile dementia may be by mechanisms other than cholinesterase inhibition.