Development of a physiologically-based pharmacokinetic model to simulate the pharmacokinetics of intramuscular antiretroviral drugs

There is growing interest in the use of long-acting (LA) injectable drugs to improve treatment adherence. However, their long elimination half-life complicates the conduct of clinical trials. Physiologically-based pharmacokinetic (PBPK) modeling is a mathematical tool that allows to simulate unknown clinical scenarios for LA formulations. Thus, this work aimed to develop and verify a mechanistic intramuscular PBPK model. The framework describing the release of a LA drug from the depot was developed by including both the physiology of the injection site and the physicochemical properties of the drug. The framework was coded in Matlab® 2020a and implemented in our existing PBPK model for the verification step using clinical data for LA cabotegravir, rilpivirine, and paliperidone. The model was considered verified when the simulations were within twofold of observed data. Furthermore, a local sensitivity analysis was conducted to assess the impact of various factors relevant for the drug release from the depot on pharmacokinetics. The PBPK model was successfully verified since all predictions were within twofold of observed clinical data. Peak concentration, area under the concentration-time curve, and trough concentration were sensitive to media viscosity, drug solubility, drug density, and diffusion layer thickness. Additionally, inflammation was shown to impact the drug release from the depot. The developed framework correctly described the release and the drug disposition of LA formulations upon intramuscular administration. It can be implemented in PBPK models to address pharmacological questions related to the use of LA formulations.

Clinical Pharmacokinetics of a Lipid-Based Formulation of Risperidone, VAL401: Analysis of a Single Dose in an Open-Label Trial of Late-Stage Cancer Patients

BACKGROUND AND OBJECTIVES

A clinical trial was conducted to measure and analyse the pharmacokinetic parameters of a lipid formulation of risperidone, VAL401. The VAL401 formulation is designed to repurpose risperidone from an antipsychotic to an adenocarcinoma treatment, with the lipid formulation altering the cellular uptake of risperidone, thus enabling anticancer biology to be exhibited in preclinical testing.

METHODS

This first human trial of VAL401 measured the concentrations of risperidone and its primary metabolite, 9-hydroxyrisperidone, in the blood of patients after treatment with a single 2-mg dose of VAL401.

RESULTS

The trial provided information on differences in the pharmacokinetic profile of risperidone in VAL401 that may be caused by the formulation and/or the nature of the cancer patient population. VAL401 provided the following key pharmacokinetic parameters for the risperidone plasma concentration after a single 2-mg dose of VAL401, with results normalised to a dosage of 1 mg for comparison with literature values: Tmax, 2 h; Cmax, 8 ng/ml; half-life, 3.5 h; area under the plasma concentration-time curve from time zero to infinity (AUC0-∞), 58.2 ng h2/mL.

CONCLUSIONS

Further comparisons of the pharmacokinetic parameters of risperidone and 9-hydroxyrisperidone in plasma of patients administered VAL401 and the corresponding parameters obtained from published data for conventionally formulated risperidone provide evidence for altered biological processing of VAL401 as compared to risperidone. The absolute values obtained provide support for future studies of VAL401 as a cancer treatment, as the Cmax demonstrates sufficient exposure to reach the concentrations seen during preclinical anticancer testing, yet the overall exposure to the active moiety supports the use of the safety and tolerability data from conventional risperidone during future clinical trials.

Serum Concentration of Paliperidone Palmitate Administered Every 3 Weeks

Schizophrenia, a disabling yet relatively common mental illness, is often controlled by antipsychotic drugs. However, long-term treatments are subject to non-adherence and consequent treatment failure. Non-adherence can be reduced by administration of slow-release drugs such as intramuscularly injected (IM) paliperidone palmitate. Considerable inter- and intra-individual variation in serum drug concentration exists, whose effect on clinical efficacy remains unclear. We report two cases of off-label use resulting in serum paliperidone levels greatly exceeding the recommended therapeutic window. A 20- and 31-year-old male were treated with 150 mg IM paliperidone palmitate/21 days. After one and two years, blood drug concentrations were 240 nmol/l and 610 nmol/l, respectively. Neither patient exhibited major adverse effects. Thus paliperidone serum levels greatly in excess of recommended targets can be well tolerated, although we urge caution with off-label use of paliperidone palmitate as it is not always the most appropriate way to achieve the control of schizophrenia.

Maintenance dose conversion between oral risperidone and paliperidone palmitate 1 month: Practical guidance based on pharmacokinetic simulations

AIM

We assessed the dosage strengths of paliperidone palmitate 1-month (PP1M) long-acting injectable resulting in similar steady-state (SS) exposures to the dosage strengths of oral risperidone using pharmacokinetic (PK) simulations.

METHODS

Population PK simulations of SS PK were performed using the PK models of oral risperidone and PP1M. The concentrations of active moiety (risperidone + paliperidone) from risperidone were compared to paliperidone concentrations resulting from PP1M administration. Similarity was assessed via graphical evaluation of median and 90% prediction intervals of SS PK profiles over 28 days.

RESULTS

Oral risperidone doses of 1, 2, 3, 4, and 6 mg/d are expected to result in similar SS PK as PP1M doses of 25, 50, 75, 100, and 150 mg eq. (which correspond to 39, 78, 117, 156, and 234 mg of paliperidone palmitate) respectively (ie 25-fold dose conversion factor from oral risperidone to PP1M).

CONCLUSIONS

This study provides clinicians with a practical guidance to establish suitable maintenance dose levels of PP1M and oral risperidone when transitioning patients from one formulation to another.

Response Surface Analysis and Nonlinear Optimization Algorithm for Maximization of Clinical Drug Performance: Application to Extended-Release and Long-Acting Injectable Paliperidone

Model-based approach is recognized as a tool to make drug development more productive and to better support regulatory and therapeutic decisions. The objective of this study was to develop a novel model-based methodology based on the response surface analysis and a nonlinear optimizer algorithm to maximize the clinical performances of drug treatments. The treatment response was described using a drug-disease model accounting for multiple components such as the dosage regimen, the pharmacokinetic characteristics of a drug (including the mechanism and the rate of drug delivery), and the exposure-response relationship. Then, the clinical benefit of a treatment was defined as a function of the diseases and the clinical endpoints and was estimated as a function of the target pharmacodynamic endpoints used to evaluate the treatment effect. A case study is presented to illustrate how the treatment performances of paliperidone extended release (ER) and paliperidone long-acting injectable (LAI) can be improved. A convolution-based approach was used to characterize the pharmacokinetics of ER and LAI paliperidone. The drug delivery properties and the dosage regimen maximizing the clinical benefit (defined as the target level of D2 receptor occupancy) were estimated using a nonlinear optimizer. The results of the analysis indicated that a substantial improvement in clinical benefit (from 15% to 27% for the optimization of the in vivo release and from ∼30% to ∼70% for the optimization of dosage regimen) was obtained when optimal strategies were deployed either for optimizing the in vivo drug delivery properties of ER formulations or for optimizing the dosage regimen of LAI formulations.

Efficacy and Safety of Paliperidone Palmitate 3-Month Formulation for Patients with Schizophrenia: A Randomized, Multicenter, Double-Blind, Noninferiority Study

BACKGROUND

This double-blind, parallel-group, multicenter, phase-3 study was designed to test the noninferiority of paliperidone palmitate 3-month formulation (PP3M) to the currently marketed 1-month formulation (PP1M) in patients (age 18-70 years) with schizophrenia, previously stabilized on PP1M.

METHODS

After screening (≤3 weeks) and a 17-week, flexible-dosed, open-label phase (PP1M: day 1 [150mg eq. deltoid], day 8 [100mg eq. deltoid.], weeks 5, 9, and 13 [50, 75, 100, or 150mg eq., deltoid/gluteal]), clinically stable patients were randomized (1:1) to PP3M (fixed-dose, 175, 263, 350, or 525mg eq. deltoid/gluteal) or PP1M (fixed-dose, 50, 75, 100, or 150mg eq. deltoid/gluteal) for a 48-week double-blind phase.

RESULTS

Overall, 1016/1429 open-label patients entered the double-blind phase (PP3M: n=504; PP1M: n=512) and 842 completed it (including patients with relapse). PP3M was noninferior to PP1M: relapse rates were similar in both groups (PP3M: n=37, 8%; PP1M: n=45, 9%; difference in relapse-free rate: 1.2% [95% CI:-2.7%; 5.1%]) based on Kaplan-Meier estimates (primary efficacy). Secondary endpoint results (changes from double-blind baseline in positive and negative symptom score total and subscale scores, Clinical Global Impression-Severity, and Personal and Social Performance scores) were consistent with primary endpoint results. No clinically relevant differences were observed in pharmacokinetic exposures between PP3M and PP1M. Both groups had similar tolerability profiles; increased weight was the most common treatment-emergent adverse event (double-blind phase; 21% each). No new safety signals were detected.

CONCLUSION

Taken together, PP3M with its 3-month dosing interval is a unique option for relapse prevention in schizophrenia.