Faculty Bibliography

Purpose: To assess the efficacy and safety of once-daily doses of perampanel 8 and 12 mg when added to 1-3 concomitantly administered, approved antiepileptic drugs (AEDs) in patients with uncontrolled partial-onset seizures. Methods: Study 305 was a multicenter, double-blind, placebo-controlled trial in patients aged 12 years and older with ongoing seizures despite prior therapy with at least two AEDs, and currently receiving 1-3 AEDs. Equal randomization to once-daily oral perampanel 8 or 12 mg, or placebo was performed. Patients entered a 19-week double-blind treatment phase comprising a 6-week titration period, with weekly 2-mg dose increments, followed by a 13-week maintenance period. Primary efficacy end points were the responder rate (proportion of patients who had a >/=50% reduction in seizure frequency during treatment per 28 days relative to baseline), and the percent change in seizure frequency per 28 days relative to pre-perampanel baseline. A secondary end point was percent change in the frequency of complex partial plus secondarily generalized seizures. Adverse events (AEs) were monitored throughout the study. Key Findings: Three hundred eighty-six patients were randomized and treated with study medication. Of these, 321 patients completed the study. The 50% responder rates (intent-to-treat analysis) were 14.7%, 33.3%, and 33.9%, respectively, for placebo, perampanel 8 mg, and perampanel 12 mg, with significant improvements over placebo for both perampanel 8 mg (p = 0.002) and 12 mg (p < 0.001). The median percent change from baseline in seizure frequency per 28 days (intent-to-treat analysis) was -9.7%, -30.5%, and -17.6% for placebo, 8 mg, and 12 mg, respectively, with significant reductions compared with placebo for both 8 mg (p < 0.001) and 12 mg (p = 0.011). For complex partial seizures plus partial seizures that secondarily generalized, the median percent change in frequency was -32.7% (8 mg), -21.9 (12 mg), and -8.1% (placebo), with significant reductions for both 8 mg (p < 0.001) and 12 mg (p = 0.005). The most frequent (occurring in >/=10% of patients in any treatment group) treatment-emergent AEs were dizziness, somnolence, fatigue, and headache, with an apparent dose effect suggested for all except headache. Significance: This phase III trial demonstrated that adjunctive treatment with once-daily perampanel at 8 mg and 12 mg was effective in improving seizure control in patients 12 years and older with refractory partial-onset seizures. These study results also demonstrated that once-daily doses of 8 mg and 12 mg were safe and acceptably tolerated in this study. Perampanel demonstrated a favorable risk/benefit ratio in this population.

Clinical trials as part of antiepileptic drug development are increasingly expensive and complex, with many pitfalls that can derail even promising drugs and devices. Although a third of patients remain resistant to treatment, the availability of more than 20 approved antiepileptic drugs can reduce the incentive to enrol in trials of unproven agents, for which safety is not assured. The challenge of recruiting patients drives investigators to regions of the world where treatment options are more limited. This increases complexity and has potential implications for quality of the trial data. Furthermore, the availability of so many approved treatments raises questions about the ethics and safety of placebo-controlled trials in patients with epilepsy. Novel trial designs, such as time-to-event adjunctive therapy and historical-control monotherapy, might be more acceptable to patients and their doctors because they restrict exposure to placebo or ineffective treatments.

OBJECTIVE: To assess efficacy and safety of once-daily 8 or 12 mg perampanel, a noncompetitive alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor antagonist, when added to concomitant antiepileptic drugs (AEDs) in the treatment of drug-resistant partial-onset seizures. METHODS: This was a multicenter, double-blind, placebo-controlled trial (ClinicalTrials.gov identifier: NCT00699972). Patients (>/=12 years, with ongoing seizures despite 1-3 AEDs) were randomized (1:1:1) to once-daily perampanel 8 mg, 12 mg, or placebo. Following baseline (6 weeks), patients entered a 19-week double-blind phase: 6-week titration (2 mg/week increments to target dose) followed by a 13-week maintenance period. Percent change in seizure frequency was the primary endpoint; 50% responder rate was the primary endpoint for EU registration. RESULTS: Of 388 patients randomized and treated, 387 provided seizure frequency data. Using this intent-to-treat population over the double-blind phase, the median percent change in seizure frequency was -21.0%, -26.3%, and -34.5% for placebo and perampanel 8 and 12 mg, respectively (p = 0.0261 and p = 0.0158 for 8 and 12 mg vs placebo, respectively). Fifty percent responder rates during the maintenance period were 26.4%, 37.6%, and 36.1%, respectively, for placebo, perampanel 8 mg, and perampanel 12 mg; these differences were not statistically significant for 8 mg (p = 0.0760) or 12 mg (p = 0.0914). Sixty-eight (17.5%) patients discontinued, including 40 (10.3%) for adverse events. Most frequent treatment-emergent adverse events were dizziness, somnolence, irritability, headache, fall, and ataxia. CONCLUSIONS: This trial demonstrated that once-daily, adjunctive perampanel at doses of 8 or 12 mg improved seizure control in patients with uncontrolled partial-onset seizures. Doses of perampanel 8 and 12 mg were safe, and tolerability was acceptable. Classification of evidence: This study provides Class I evidence that once-daily 8 and 12 mg doses of adjunctive perampanel are effective in patients with uncontrolled partial-onset seizures.

Early withdrawal of patients from a clinical trial can compromise the robustness of the data by introducing bias into the analysis. This is most commonly addressed by using the "intent to treat" (ITT) population and "last observation carried forward" (LOCF) methodology, where a patient's last assessment is carried forward. This can lead to overstatement of treatment efficacy especially if events indicative of treatment failure are infrequent. An alternative methodology, labeled "pragmatic ITT" (P-ITT), requires patients to have a positive outcome and to complete the trial in order to be considered a treatment success by that outcome measure. Data from 3 randomized multicenter lamotrigine extended-release (LTG XR) trials were analyzed and response (proportions seizure-free and with 50% response) were compared using LOCF and P-ITT methodologies. In 2 of the 3 trials, a lower response for both seizure freedom and 50% response was seen during the Maintenance phase using the P-ITT methodology. In the trial that did not show a difference, only a small number of patients withdrew early, thus negating the benefit brought by the P-ITT method. Differences between methodologies were not noted when evaluation was applied to the entire treatment period, most likely a reflection of the fact that a therapeutic dose of lamotrigine is not rapidly achieved. We propose that the P-ITT may be a simpler, more informative method for evaluating the effectiveness of a drug, especially in comparison to another active drug(s).