Efficacy of once-daily extended-release topiramate (USL255): a subgroup analysis based on the level of treatment resistance

Topiramate add-on therapy for drug-resistant focal epilepsy

BACKGROUND

The majority of people with epilepsy have a good prognosis and their seizures are controlled by a single antiepileptic drug. However, up to 20% of patients from population-based studies, and up to 30% from clinical series (not population-based), develop drug-resistant epilepsy, especially those with focal-onset seizures. In this review, we summarise the current evidence regarding topiramate, an antiepileptic drug first marketed in 1996, when used as an add-on treatment for drug-resistant focal epilepsy.This is an update of a Cochrane Review first published in 1999, and last updated in 2014.

OBJECTIVES

To evaluate the efficacy and tolerability of topiramate when used as an add-on treatment for people with drug-resistant focal epilepsy.

SEARCH METHODS

For the latest update of this review we searched the following databases on 2 July 2018: Cochrane Register of Studies (CRS Web), which includes the Cochrane Epilepsy Group Specialized Register and the Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE (Ovid, 1946- ); ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP). We imposed no language restrictions. We also contacted the manufacturers of topiramate and researchers in the field to identify any ongoing or unpublished studies.

SELECTION CRITERIA

Randomised, placebo-controlled add-on trials of topiramate, recruiting people with drug-resistant focal epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion and extracted the relevant data. We assessed the following outcomes: (1) 50% or greater reduction in seizure frequency; (2) seizure freedom; (3) treatment withdrawal (any reason); (4) adverse effects. Primary analyses were intention-to-treat (ITT), and summary risk ratios (RRs) with 95% confidence intervals (95% CIs) are presented. We evaluated dose-response in regression models. We carried out a 'Risk of bias' assessment for each included study using the Cochrane 'Risk of bias' tool and assessed the overall certainty of evidence using the GRADE approach.

MAIN RESULTS

We included 12 trials, representing 1650 participants. Baseline phases ranged from four to 12 weeks and double-blind phases ranged from 11 to 19 weeks. The RR for a 50% or greater reduction in seizure frequency with add-on topiramate compared to placebo was 2.71 (95% CI 2.05 to 3.59; 12 studies; high-certainty evidence). Dose regression analysis showed increasing effect with increasing topiramate dose demonstrated by an odds ratio (OR) of 1.45 (95% CI 1.28 to 1.64; P < 0.001) per 200 mg/d increase in topiramate dosage. The proportion of participants achieving seizure freedom was also significantly increased with add-on topiramate compared to placebo (RR 3.67, 95% CI 1.79 to 7.54; 8 studies; moderate-certainty evidence). Treatment withdrawal was significantly higher for add-on topiramate compared to placebo (RR 2.37, 95% CI 1.66 to 3.37; 12 studies; high-certainty evidence). The RRs for the following adverse effects indicate that they are significantly more prevalent with topiramate, compared to placebo: ataxia 2.29 (99% CI 1.10 to 4.77; 4 studies); concentration difficulties 7.81 (99% CI 2.08 to 29.29; 6 studies; moderate-certainty evidence); dizziness 1.52 (99% CI 1.07 to 2.16; 8 studies); fatigue 2.08 (99% CI 1.37 to 3.15; 10 studies); paraesthesia 3.65 (99% CI 1.58 to 8.39; 7 studies; moderate-certainty evidence); somnolence 2.44 (99% CI 1.61 to 3.68; 9 studies); 'thinking abnormally' 5.70 (99% CI 2.26 to 14.38; 4 studies; high-certainty evidence); and weight loss 3.99 (99% CI 1.82 to 8.72; 9 studies; low-certainty evidence). Evidence of publication bias for the primary outcome was found (Egger test, P = 0.001). We rated all studies included in the review as having either low or unclear risk of bias. Overall, we assessed the evidence as moderate to high certainty due to the evidence of publication bias, statistical heterogeneity and imprecision, which was partially compensated for by large effect sizes.

AUTHORS' CONCLUSIONS

Topiramate has efficacy as an add-on treatment for drug-resistant focal epilepsy as it is almost three times more effective compared to a placebo in reducing seizures. The trials reviewed were of relatively short duration and provided no evidence for the long-term efficacy of topiramate. Short-term use of add-on topiramate was shown to be associated with several adverse events. The results of this review should only be applied to adult populations as only one study included children. Future research should consider further examining the effect of dose.

Predicting Response to Treatment of Epileptic Seizures: How Much Time and How Many AEDs Do We Need to Try?

Identification of Patients Who Will Not Achieve Seizure Remission Within 5 Years on AEDs

Hughes DM, Bonnett LJ, Czanner G, Komárek A, Marson AG, García Fiñana M. Neurology. 2018;91(22):e2035-e2044. doi:10.1212/WNL.0000000000006564. Epub 2018 Nov 2. PMID: 30389894.

Objective:

To identify people with epilepsy who will not achieve a 12-month seizure remission within 5 years of starting treatment.

Methods:

The Standard and New Antiepileptic Drug (SANAD) study is the largest prospective study in patients with epilepsy to date. We applied a recently developed multivariable approach to the SANAD data set that takes into account not only baseline covariates describing a patient’s history before diagnosis but also follow-up data as predictor variables.

Results:

Changes in number of seizures and treatment history were the most informative time-dependent predictors and were associated with history of neurologic insult, epilepsy type, age at start of treatment, sex, and having a first-degree relative with epilepsy. Our model classified 95% of patients. Of those classified, 95% of patients observed not to achieve remission at 5 years were correctly classified (95% confidence interval [CI]: 89.5%-100%), with 51% identified by 3 years and 90% within 4 years of follow-up. Ninety-seven percent (95% CI: 93.3%-98.8%) of patients observed to achieve a remission within 5 years were correctly classified. Of those predicted not to achieve remission, 76% (95% CI: 58.5%-88.2%) truly did not achieve remission (positive predictive value). The predictive model achieved similar accuracy levels via external validation in 2 independent United Kingdom-based data sets.

Conclusion:

Our approach generates up-to-date predictions of the patient’s risk of not achieving seizure remission whenever new clinical information becomes available that could influence patient counseling and management decisions.

Extended-release drug formulations for the treatment of epilepsy

INTRODUCTION

Extended-release (ER) preparations are either available or have been tested for several antiepileptic drugs (AEDs). Indeed, they may be helpful in improving efficacy, tolerability, adherence, compared to the corresponding immediate release (IR) preparations available. The use of ER preparations has been advocated in women of childbearing age and is - depending on the drug - especially helpful in patients who are treated in combination with enzyme inducing AEDs as well as in children.

AREAS COVERED

Clinical and pharmacokinetic studies on ER formulations of AEDs were identified by a PubMed literature research. Further references were added from the authors' personal knowledge and from the reference lists of the identified studies. Reviews and expert commentaries were included, where necessary.

EXPERT OPINION

Unfortunately, studies providing direct comparisons of ER and IR formulations of a given drug are only available for a handful of drugs. ER preparations are especially helpful in drugs with a short elimination half-life and concentration-depending efficacy and tolerability.

Long-term safety and sustained efficacy of USL255 (topiramate extended-release capsules) in patients with refractory partial-onset seizures

OBJECTIVE

The aim of this study was to evaluate long-term safety, efficacy, and quality of life (QOL) of ≤400-mg/day USL255, Qudexy® XR (topiramate) extended-release capsules, as adjunctive therapy for partial-onset seizures (POS) in adults.

METHODS

Patients who completed the 11-week double-blind treatment phase of the phase 3 PREVAIL study were eligible to enroll in this 1-year open-label extension (OLE) study (PREVAIL OLE). The primary objective was to evaluate the safety and tolerability of USL255 (including treatment-emergent adverse events [TEAEs]). The secondary objective was to assess seizure frequency in patients (e.g., median percent reduction from baseline in weekly POS frequency, responder rate [proportion of patients with ≥25%, ≥50%, ≥75%, or 100% reduction from baseline in POS frequency], and seizure-free intervals [proportion of patients who were seizure-free for 4, 12, 24, 36, or 48weeks]). Exploratory clinical-status endpoints included the Global Impression of Change (CGI-C) and Quality of Life in Epilepsy-Problems (QOLIE-31-P) questionnaires. Post hoc analyses evaluated neurocognitive TEAE incidences during the first 11 and entire 55weeks of treatment and efficacy by patient age and drug-resistant status.

RESULTS

Of the 217 patients who completed PREVAIL (USL255, n=103; placebo, n=114), 210 (97%) enrolled in PREVAIL OLE and were included in the ITT population. Across the entire 55-week treatment period, USL255 was generally safe and well tolerated, with low individual neurocognitive TEAE incidences. Seizure reduction was sustained across the year-long study and observed in patient subgroups, including those with highly drug-resistant seizures and those ≥50years of age. Improvements in CGI-C and QOLIE-31-P were also observed.

SIGNIFICANCE

The results of PREVAIL OLE are consistent with those from PREVAIL and demonstrate that adjunctive treatment with up to 400mg/day of USL255 may be a safe and effective treatment option for a variety of adult patients with refractory POS.

Topiramate Extended Release: A Review in Epilepsy

Once-daily oral topiramate extended release (USL255; hereafter referred to as topiramate XR) [QUDEXY(®) XR] is approved in the USA for use as initial monotherapy and adjunctive therapy in patients aged ≥2 years with partial-onset seizures (POS) or primary generalized tonic-clonic seizures and as adjunctive therapy in patients aged ≥2 years with seizures associated with Lennox-Gastaut syndrome. Compared with twice-daily topiramate immediate release at the same total daily dose, topiramate XR provided bioequivalent exposure, an extended absorption rate (permitting convenient once-daily dosing) and more constant therapeutic plasma concentrations (potentially minimizing topiramate-associated adverse events). Switching between the two formulations did not affect the maintenance of topiramate concentrations. Moreover, the contents of a topiramate XR capsule may be sprinkled on to soft food for patients who have difficulty swallowing. In a multinational phase III study in adults with refractory POS, adjunctive topiramate XR was associated with significantly greater improvements from baseline in weekly median seizure frequency and the proportion of patients achieving a ≥50 % reduction in seizure frequency compared with placebo. These benefits were sustained during a 55-week open-label extension study. Adjunctive topiramate XR was generally well tolerated in these studies, with the majority of treatment-emergent adverse events being mild or moderate in intensity. In conclusion, current evidence suggests once-daily topiramate XR extends the treatment options currently available for patients aged ≥2 years with epilepsy, with its dosing regimen potentially delivering tolerability and adherence advantages over AEDs that require more frequent administration.

Clinical utility of topiramate extended-release capsules (USL255): Bioequivalence of USL255 sprinkled and intact capsule in healthy adults and an in vitro evaluation of sprinkle delivery via enteral feeding tubes

OBJECTIVE

The objectives of these two studies were to determine if beads from extended-release topiramate capsules sprinkled onto soft food are bioequivalent to the intact capsule and if beads from the capsule can be passed through enteral gastrostomy (G-) and jejunostomy (J-) feeding tubes.

METHODS

Bioequivalence of 200-mg USL255 (Qudexy XR [topiramate] extended-release capsules) sprinkled onto soft food (applesauce) versus the intact capsule was evaluated in a phase 1, randomized, single-dose, crossover study (N=36). Pharmacokinetic evaluations included area under the curve (AUC), maximum plasma concentration (Cmax), time to Cmax (Tmax), and terminal elimination half-life (t1/2). If 90% confidence intervals (CI) of the ratio of geometric least-squares means were between 0.80 and 1.25, AUC and Cmax were considered bioequivalent. In separate in vitro experiments, 100-mg USL255 beads were passed through feeding tubes using gentle syringe pressure to develop a clog-free bead-delivery method. Multiple tube sizes (14- to 18-French [Fr] tubes), dilutions (5 mg/15 mL-25 mg/15 mL), and diluents (deionized water, apple juice, Ketocal, sparkling water) were tested.

RESULTS

Area under the curve and Cmax for USL255 beads sprinkled onto applesauce were bioequivalent to the intact capsule (GLSM [90% CI]: AUC0-t 1.01 [0.97-1.04], AUC0-∞ 1.02 [0.98-1.05]; Cmax 1.09 [1.03-1.14]). Median Tmax was 4h earlier for USL255 sprinkled versus the intact capsule (10 vs 14 h; p=0.0018), and t1/2 was similar (84 vs 82 h, respectively). In 14-Fr G-tubes, USL255 beads diluted in Ketocal minimized bead clogging versus deionized water. Recovery of USL255 beads diluted in deionized water was nearly 100% in 16-Fr G-, 18-Fr G-, and 18-Fr J-tubes.

SIGNIFICANCE

For patients with difficulty swallowing pills, USL255 sprinkled onto applesauce offers a useful once-daily option for taking topiramate. USL255 beads were also successfully delivered in vitro through ≥14-Fr G- or J-tubes, with tube clogging minimized by portioning the dose and using glidant diluents for smaller tubes.