Extrapolation of Efficacy from Adults to Pediatric Patients of Drugs for Treatment of Partial Onset Seizures (POS): A Regulatory Perspective

A review on the role of extrapolation as basis for paediatric marketing authorization applications of medicines in the EU

AIMS

For new medicines, drug companies obtain regulatory approval on the strategy to generate evidence in the paediatric population, which can be supported by extrapolation of evidence obtained in a reference population. This study investigated whether paediatric marketing authorization applications (PMAAs) supported by extrapolation based on exposure-matching were more successful-i.e. approval of the targeted paediatric population-and efficient-i.e. duration of the drug development-compared to PMAAs not supported by extrapolation.

METHODS

Data was extracted from completed paediatric investigation plans (PIPs), associated drug labels and public assessment reports published on the European Medicines Agency website. Assessment reports were evaluated to assess whether PMAAs were supported by extrapolation based on exposure-matching. Wilcoxon rank-sum tests were used to compare PMAAs supported and not supported by extrapolation based on exposure-matching for outcomes of interest.

RESULTS

Exposure-matching supported the benefit/risk assessment of 39.6% of the PMAAs. Targeted and approved minimum age of the paediatric population were comparable for PMAAs where extrapolation based on exposure-matching supported the benefit/risk assessment (2.0 vs. 2.0 years, P-value = .72), but not for PMAAs not supported by extrapolation (0.2 years vs. 0.5 years, P-value = .05). Completion of drug development was 5.4 years vs. 4.3 years (P = .04) in PMAAs supported by extrapolation based on exposure-matching compared to those not supported by extrapolation, respectively.

CONCLUSIONS

PMAAs supported by extrapolation based on exposure-matching succeeded more often in obtaining marketing approval in the targeted paediatric population than PMAAs not supported by exposure-matching, but were also less efficient.

Long-term safety and efficacy of adjunctive perampanel in pediatric patients (ages 4 to <12 years) with inadequately controlled focal-onset seizures or generalized tonic-clonic seizures

OBJECTIVE

Study 311 (NCT02849626) Extension A assessed long-term outcomes of adjunctive perampanel treatment in children (ages 4 to <12 years) with uncontrolled focal-onset seizures (FOS), with/without focal to bilateral tonic-clonic seizures (FBTCS), or generalized tonic-clonic seizures (GTCS).

METHODS

Patients completing the 23-week Core Study could enter Extension A (29-week Maintenance and 4-week Follow-up Periods) to receive perampanel at the dose achieved during the Core Study. Dose adjustments were permitted per the investigator's discretion during Extension A. The maximum dose was 12 mg/day for patients enrolled in Japan and without enzyme-inducing anti-seizure medications (EIASMs), or 16 mg/day with EIASM(s). Safety and tolerability were monitored throughout Extension A. Efficacy assessments included median percent change in seizure frequency per 28 days from baseline and 50% responder rates. Outcomes were analyzed by seizure type, age (4 to <7 vs 7 to <12 years), and EIASM use.

RESULTS

Of 180 patients enrolling in the Core Study, 136 entered (FOS, n = 116 [including 43 with FBTCS]; GTCS, n = 20) and 122 completed Extension A. Treatment-emergent adverse events (TEAEs) were the most common reason for discontinuation (4%). The mean (standard deviation) dose during Extension A was 8.3 (3.2) mg/day. Incidences of TEAEs in Extension A were 69% overall and 62%-89% across subgroups; TEAEs led to dose adjustment in 10% of patients. No changes of clinical concern in cognition, growth, development, or quality of life were identified over 52 weeks. At Weeks 40-52, median percent reductions in seizure frequency per 28 days from baseline were 69% (FOS, n = 108), 74% (FBTCS, n = 41), and 100% (GTCS, n = 13); 50% responder rates were 62% (FOS and GTCS) and 81% (FBTCS). Efficacy outcomes were comparable across age and EIASM groups.

SIGNIFICANCE

These findings support long-term (≤52 weeks) use of adjunctive perampanel in children with epilepsy, irrespective of seizure type, age, or EIASM use.

Model-informed drug development in pediatric, pregnancy and geriatric drug development: States of the art and future

The challenges of drug development in pediatric, pregnant and geriatric populations are a worldwide concern shared by regulatory authorities, pharmaceutical companies, and healthcare professionals. Model-informed drug development (MIDD) can integrate and quantify real-world data of physiology, pharmacology, and disease processes by using modeling and simulation techniques to facilitate decision-making in drug development. In this article, we reviewed current MIDD policy updates, reflected on the integrity of physiological data used for MIDD and the effects of physiological changes on the drug PK, as well as summarized current MIDD strategies and applications, so as to present the state of the art of MIDD in pediatric, pregnant and geriatric populations. Some considerations are put forth for the future improvements of MIDD including refining regulatory considerations, improving the integrity of physiological data, applying the emerging technologies, and exploring the application of MIDD in new therapies like gene therapies for special populations.

Pediatric Extrapolation Approach for U.S. Food and Drug Administration Approval of Brexpiprazole in Patients Aged 13 to 17 Years with Schizophrenia

A pharmacokinetic (PK) bridging approach was successfully employed to support the dosing regimen and approval of brexpiprazole in pediatric patients aged 13-17 years with schizophrenia. Brexpiprazole was approved in 2015 for the treatment of schizophrenia and the adjunctive treatment of major depressive disorder in adults based on efficacy and safety data from clinical trials. On January 13, 2020, the US Food and Drug Administration issued a general advice letter to sponsors highlighting the acceptance of efficacy extrapolation of certain atypical antipsychotics from adult patients to pediatric patients considering the similarity in disease and exposure-response relationships. Brexpiprazole is the first atypical antipsychotic approved in pediatrics using this approach. The PK data available from pediatric patients aged 13-17 years have shown high variability due to the limited number of PK evaluable subjects, which limits a robust estimation of differences between adult and pediatric patients. The PK model-based approach was thus utilized to evaluate the appropriateness of the dosing regimen by comparing PK exposures in pediatric patients aged 13-17 years with exposures achieved in adults at the approved doses. In addition to exposure matching, safety data from a long-term open-label clinical study in pediatric patients informed the safety profile in pediatric patients. This report illustrates the potential of leveraging previously collected efficacy, safety, and PK data in adult patients to make a regulatory decision in pediatric patients for the indication of schizophrenia.

Brivaracetam exposure-response predictions in pediatric patients from age 1 month: Extrapolation of levetiracetam adult-pediatric scaling to brivaracetam

BACKGROUND

An adult population pharmacokinetic/pharmacodynamic (PK/PD) model for the antiseizure medication (ASM) brivaracetam (BRV) was previously extended to children aged 4-16 years by using a pediatric BRV population PK model. Effects were scaled using information from a combined adult-pediatric PK/PD model of a related ASM, levetiracetam (LEV).

OBJECTIVE

To scale an existing adult population PK/PD model for BRV to children aged 1 month to < 4 years using information from a combined adult-pediatric PK/PD model for LEV, and to predict the effective dose of BRV in children aged 1 month to < 4 years using the adult BRV PK/PD model modified for the basal seizure rate in children.

MATERIAL AND METHODS

An existing adult population PK/PD model for BRV was scaled to children aged from 1 month to < 4 years using information from a combined adult-pediatric PK/PD model for LEV, an ASM binding to the same target protein as BRV. An existing adult-pediatric PK/PD model for LEV was extended using data from UCB study N01009 (NCT00175890) to include children as young as 1 month of age. The BRV population PK model was updated with data up to 180 days after first administration from BRV pediatric studies N01263 (NCT00422422) and N01266 (NCT01364597). PK and PD simulations for BRV were performed for a range of mg/kg doses to predict BRV effect in pediatric participants, and to provide dosing recommendations.

RESULTS

The extended adult-pediatric LEV PK/PD model was able to describe the adult and pediatric data using the same PD model parameters in adults and children and supported the extension of the adult BRV PK/PD model to pediatric patients aged 1 month to < 4 years. Simulations predicted exposures similar to adults receiving BRV 100 mg twice daily (b.i.d.), when using 3 mg/kg b.i.d. for weight < 10 kg, 2.5 mg/kg b.i.d. for weight ≥ 10 kg and < 20 kg, and 2 mg/kg b.i.d. for weight ≥ 20 kg in children aged 1 month to < 4 years. PK/PD simulations show that maximum BRV response is expected to occur with 2-3 mg/kg b.i.d. dosing of BRV in children aged 1 month to < 4 years, with an effective dose of 1 mg/kg b.i.d. for some participants.

CONCLUSION

Development of an adult-pediatric BRV PK/PD model allowed characterization of the exposure-response relationship of BRV in children aged 1 to < 4 years, providing a maximal dose allowance based on weight.

Sources of pharmacokinetic and pharmacodynamic variability and clinical pharmacology studies of antiseizure medications in the pediatric population

Multiple treatment options exist for children with epilepsy, including surgery, dietary therapies, neurostimulation, and antiseizure medications (ASMs). ASMs are the first line of therapy, and more than 30 ASMs have U.S. Food and Drug Administration (FDA) approval for the treatment of various epilepsy and seizure types in children. Given the extensive FDA approval of ASMs in children, it is crucial to consider how the physiological and developmental changes throughout childhood may impact drug disposition. Various sources of pharmacokinetic (PK) variability from different extrinsic and intrinsic factors such as patients' size, age, drug-drug interactions, and drug formulation could result in suboptimal dosing of ASMs. Barriers exist to conducting clinical pharmacological studies in neonates, infants, and children due to ethical and practical reasons, limiting available data to fully characterize these drugs' disposition and better elucidate sources of PK variability. Modeling and simulation offer ways to circumvent traditional and intensive clinical pharmacology methods to address gaps in epilepsy and seizure management in children. This review discusses various physiological and developmental changes that influence the PK and pharmacodynamic (PD) variability of ASMs in children, and several key ASMs will be discussed in detail. We will also review novel trial designs in younger pediatric populations, highlight the role of extrapolation of efficacy in epilepsy, and the use of physiologically based PK modeling as a tool to investigate sources of PK/PD variability in children. Finally, we will conclude with current challenges and future directions for optimizing the efficacy and safety of these drugs across the pediatric age spectrum.

Development and Validation of Physiologically Based Pharmacokinetic Model of Levetiracetam to Predict Exposure and Dose Optimization in Pediatrics

Levetiracetam (Lev) is an antiepileptic drug that has been increasingly used in the epilepsy pediatric population in recent years, but its pharmacokinetic behavior in pediatric population needs to be characterized clearly. Clinical trials for the pediatric drug remain difficult to conduct due to ethical and practical factors. The purpose of this study was to use the physiologically based pharmacokinetic (PBPK) model to predict changes in plasma exposure of Lev in pediatric patients and to provide recommendations for dose adjustment. A PBPK model of Lev in adults was developed using PK-Sim® software and extrapolated to the entire age range of the pediatric population. The model was evaluated using clinical pharmacokinetic data. The results showed the good fit between predictions and observations of the adult and pediatric models. The recommended doses for neonates, infants and children are 0.78, 1.67 and 1.22 times that of adults, respectively. Moreover, at the same dose, plasma exposure in adolescents was similar to that of adults. The PBPK models of Lev for adults and pediatrics were successfully developed and validated to provide a reference for the rational administration of drugs in the pediatric population.