Efficacy and safety of Losigamone in partial seizures: a randomized double-blind study

Losigamone add-on therapy for focal epilepsy

BACKGROUND

Epilepsy is a common neurologic disorder, affecting approximately 50 million people worldwide; nearly a third of these people have epilepsy that is not well controlled by a single antiepileptic drug (AED) and they usually require treatment with a combination of two or more AEDs. In recent years, many newer AEDs have been investigated as add-on therapy for focal epilepsy; losigamone is one of these drugs and is the focus of this systematic review. This is an update of a Cochrane Review first published in 2012 and updated in 2018.

OBJECTIVES

To investigate the efficacy and tolerability of losigamone when used as an add-on therapy for focal epilepsy.

SEARCH METHODS

For the latest update on 20 August 2019, we searched the Cochrane Register of Studies (CRS Web) and MEDLINE. CRS Web includes randomized or quasi-randomized, controlled studies from the Specialized Registers of Cochrane Review Groups including Cochrane Epilepsy, CENTRAL, PubMed, Embase, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform (ICTRP). Previously we searched trials registers and contacted the manufacturer of losigamone and authors of included studies for additional information. We did not impose any language restrictions.

SELECTION CRITERIA

Randomized controlled, add-on studies comparing losigamone with placebo for focal epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study quality and extracted data. The primary outcomes were 50% or greater reduction in seizure frequency and seizure freedom; the secondary outcomes were treatment withdrawal and adverse events. Results are presented as risk ratios (RRs) with 95% confidence intervals (CIs) or 99% CIs (for the individual listed adverse events to make an allowance for multiple testing).

MAIN RESULTS

Two studies involving a total of 467 participants, aged over 18 years, were eligible for inclusion. Both studies assessed losigamone 1200 mg/day or 1500 mg/day as an add-on therapy for focal epilepsy. We assessed one study as being of good methodological quality while the other was of uncertain quality. For the efficacy outcomes, results showed that participants taking losigamone were significantly more likely to achieve a 50% or greater reduction in seizure frequency (RR 1.76, 95% CI 1.14 to 2.72; 2 studies, 467 participants; moderate-quality evidence), but associated with a significant increase of treatment withdrawal when compared with those taking placebo (RR 2.16, 95% CI 1.28 to 3.67; 2 studies, 467 participants; moderate-quality evidence). For the tolerability outcomes, results indicated that the proportion of participants who experienced adverse events in the losigamone group was higher than in the placebo group (RR 1.34, 95% CI 1.00 to 1.80; 2 studies, 467 participants; moderate-quality evidence). Dizziness was the only adverse event significantly reported in relation to losigamone (RR 3.82, 99% CI 1.69 to 8.64; 2 studies; 467 participants; moderate-quality evidence). Neither study reported the proportion of participants achieving seizure freedom. A subgroup analysis according to different doses of losigamone showed that a higher dose of losigamone (1500 mg/day) was associated with a greater reduction in seizure frequency than lower doses, but was also associated with more dropouts due to adverse events.

AUTHORS' CONCLUSIONS

The results of this review showed that losigamone did reduce seizure frequency but was associated with more treatment withdrawals when used as an add-on therapy for people with focal epilepsy. However, the included studies were of short-term duration and uncertain quality. Future well-designed randomized, double-blind, placebo-controlled studies with a longer-term duration are needed. We did not find any new studies since the last version of this review. We judged the overall quality of the evidence for the outcomes assessed as moderate.

Losigamone add-on therapy for focal epilepsy

BACKGROUND

Epilepsy is a common neurologic disorder, affecting approximately 50 million people worldwide; nearly a third of these people have epilepsy that is not well controlled by a single antiepileptic drug (AED) and they usually require treatment with a combination of two or more AEDs. In recent years, many newer AEDs have been investigated as add-on therapy for focal epilepsy; losigamone is one of these drugs and is the focus of this systematic review. This is an update of a Cochrane review first published in 2012 (Cochrane Database of Systematic Reviews 2012, Issue 6) and updated in 2015.

OBJECTIVES

To investigate the efficacy and safety of losigamone when used as an add-on therapy for focal epilepsy.

SEARCH METHODS

For the latest update on 9 February 2017, we searched the Cochrane Epilepsy Specialized Register, CENTRAL and MEDLINE . We searched trials registers and contacted the manufacturer of losigamone and authors of included studies for additional information. We did not impose any language restrictions.

SELECTION CRITERIA

Randomized controlled, add-on trials comparing losigamone with placebo for focal epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. The primary outcomes were 50% or greater reduction in seizure frequency and seizure freedom; the secondary outcomes were treatment withdrawal and adverse events. Results are presented as risk ratios (RRs) with 95% confidence intervals (CIs) or 99% CIs (for the individual listed adverse events to make an allowance for multiple testing).

MAIN RESULTS

Two trials involving a total of 467 participants, aged over 18 years, were eligible for inclusion. Both trials assessed losigamone 1200 mg/day or 1500 mg/day as an add-on therapy for focal epilepsy. We assessed one trial as being of good methodological quality while the other was of uncertain quality. For the efficacy outcomes, results did show that participants taking losigamone were significantly more likely to achieve a 50% or greater reduction in seizure frequency (RR 1.76, 95% CI 1.14 to 2.72), but associated with a significant increase of treatment withdrawal when compared with those taking placebo (RR 2.16, 95% CI 1.28 to 3.67). For the safety outcomes, results indicated that the proportion of participants who experienced adverse events in the losigamone group was higher than in the placebo group (RR 1.34, 95% CI 1.00 to 1.80), dizziness was the only adverse event significantly reported in relation to losigamone (RR 3.82, 99% CI 1.69 to 8.64). The proportion of participants achieving seizure freedom was not reported in either trial report. A subgroup analysis according to different doses of losigamone showed that a higher dose of losigamone (1500 mg/day) was associated with a greater reduction in seizure frequency than lower doses, but was also associated with more dropouts due to adverse events.

AUTHORS' CONCLUSIONS

The results of this review showed that losigamone did reduce seizure frequency but was associated with more treatment withdrawals when used as an add-on therapy for people with focal epilepsy. However, the included trials were of short-term duration and uncertain quality. Future well-designed randomized, double-blind, placebo-controlled trials with a longer-term duration are needed. No new studies have been found since the last version of this review. We judged the overall quality of the evidence for the outcomes assessed as moderate.

Losigamone add-on therapy for partial epilepsy

BACKGROUND

Epilepsy is a common neurologic disorder, affecting approximately 50 million people worldwide; nearly a third of these people are not well controlled by a single antiepileptic drug (AED) and usually require treatment with a combination of two or more AEDs. In recent years, many newer AEDs have been investigated as add-on therapy for partial epilepsy; losigamone is one of these drugs and is the focus of this systematic review. This is an update of a Cochrane review first published in 2012 (Cochrane Database of Systematic Reviews 2012, Issue 6).

OBJECTIVES

To investigate the efficacy and safety of losigamone when used as an add-on therapy for partial epilepsy.

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register (16 February 2015), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library 16 February 2015) and MEDLINE (Ovid, 1946 to 16 February 2015). We searched trials registers and contacted the manufacturer of losigamone and authors of included studies for additional information. We did not impose any language restrictions.

SELECTION CRITERIA

Randomized controlled, add-on trials comparing losigamone with placebo for partial epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. The primary outcomes were 50% or greater reduction in seizure frequency and seizure freedom; the secondary outcomes were treatment withdrawal and adverse events. Results are presented as risk ratios (RRs) with 95% confidence intervals (CIs) or 99% CIs (for the individual listed adverse events to make an allowance for multiple testing).

MAIN RESULTS

Two trials involving a total of 467 patients, aged over 18 years, were eligible for inclusion. Both trials assessed losigamone 1200 mg/day or 1500 mg/day as an add-on therapy for partial epilepsy. One trial was assessed as being of good methodological quality while the other was of uncertain quality. For the efficacy outcomes, results did show patients taking losigamone were significantly more likely to achieve a 50% or greater reduction in seizure frequency (RR 1.76; 95% CI 1.14 to 2.72), but associated with a significant increase of treatment withdrawal when compared with those taking placebo (RR 2.16; 95% CI 1.28 to 3.67). For the safety outcomes, results indicated the proportion of patients who experienced adverse events in the losigamone group was higher than the placebo group (RR 1.34; 95% CI 1.00 to 1.80), dizziness was the only adverse event significantly reported in relation to losigamone (RR 3.82; 99% CI 1.69 to 8.64). The proportion of patients achieving seizure freedom was not reported in either trial report. A subgroup analysis according to different doses of losigamone showed that a higher dose of losigamone (1500 mg/day) was associated with a greater reduction in seizure frequency than lower doses, but was also associated with more dropouts due to adverse events.

AUTHORS' CONCLUSIONS

The results of this review showed losigamone did reduce seizure frequency but was associated with more treatment withdrawals when used as an add-on therapy for people with partial epilepsy. However, trials included were of short-term duration and uncertain quality. Future well-designed randomized, double-blind, placebo-controlled trials with a longer-term duration are needed. No new studies have been found since the last version of this review.

Losigamone add-on therapy for partial epilepsy

BACKGROUND

Epilepsy is a common neurologic disorder, affecting approximately 50 million people worldwide; nearly a third of these people are not well controlled by a single antiepileptic drug and usually require treatment with a combination of two or more antiepileptic drugs. In recent years, many newer antiepileptic drugs have been investigated as add-on therapy for partial epilepsy; losigamone is one of these drugs and is the focus of this systematic review.

OBJECTIVES

To investigate the efficacy and safety of losigamone when used as an add-on therapy for partial epilepsy.

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register (1 May 2012), the Cochrane Central Register of Controlled Trials (CENTRAL Issue 4 of 12, The Cochrane Library, 2012) and MEDLINE (1 May 2012). We searched trials registers and contacted the manufacturer of losigamone and authors of included studies for additional information. There were no language restrictions.

SELECTION CRITERIA

Randomized controlled add-on trials comparing losigamone with placebo for partial epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. The primary outcomes were 50% or greater reduction in seizure frequency and seizure freedom; the secondary outcomes were treatment withdrawal and adverse events. Results are presented as risk ratios (RR) with 95% confidence intervals (CIs) or 99% CIs (for the individual listed adverse events to make an allowance for multiple testing).

MAIN RESULTS

Two trials involving a total of 467 patients were eligible for inclusion. Both trials assessed losigamone 1200 or 1500 mg/d as an add-on therapy for partial epilepsy. One trial was assessed as being of good methodologic quality while the other was of uncertain quality. For the efficacy outcomes, results did show patients taking losigamone were significantly more likely to achieve a 50% or greater reduction in seizure frequency (RR 1.75; 95% CI 1.14 to 2.72), but associated with a significant increase of treatment withdrawal when compared with those taking placebo (RR 2.16; 95% CI 1.28 to 3.67). For the safety outcomes, results indicated the proportion of patients who experienced adverse events in the losigamone group was higher than the placebo group (RR 1.34; 95% CI 1.00 to 1.80), dizziness was the only adverse event significantly in relation to losigamone (RR 3.82; 99% CI 1.69 to 8.64). The proportion of patients achieving seizure freedom was not reported in either trial report. A subgroup analysis according to different doses of losigamone showed that a higher dose of losigamone (1500 mg/d) is associated with a greater reduction in seizure frequency than lower doses, but is also associated with more dropouts due to adverse events.

AUTHORS' CONCLUSIONS

The results of this review showed losigamone can reduce seizure frequency but was associated with more treatment withdrawals when used as an add-on therapy for people with partial epilepsy. However, trials included were of short-term duration and uncertain quality. Future well-designed randomized, double-blind, placebo-controlled trials with a longer-term duration are needed.

Factors determining response to antiepileptic drugs in randomized controlled trials. A systematic review and meta-analysis

PURPOSE

Because of the lack of head-to-head adjunctive-therapy trials of antiepileptic drugs (AEDs) in refractory partial epilepsy, meta-analyses of placebo-controlled randomized controlled trials (RCTs) represent a potentially important source of evidence to guide treatment decisions. However, such indirect comparisons raise various methodologic issues that may hamper their relevance.

METHODS

All RCTs in adult refractory partial epilepsy were analyzed to assess whether efficacy outcomes are influenced by: characteristics of patients and trials ; use of last observation carried forward (LOCF) analysis; evaluation period (entire period versus maintenance period); and year of publication. A meta-analysis of these AEDs was then performed taking these factors into consideration.

KEY FINDINGS

Sixty-three RCTs evaluating 20 AEDs were included. The following variables influenced efficacy estimates: (1) responder rates correlated positively with duration of the entire treatment period (p = 0.038); (2) response to placebo was significantly greater in the maintenance period than in the entire treatment period (p = 0.005); (3) responder rates increased over the years both for AEDs (p < 0.001) and for placebo (p = 0.001); (4) LOCF analysis overestimated responder rates for AEDs (p < 0.001) and for placebo (p = 0.001) compared with completer-based analysis, and the overestimation correlated positively with withdrawal rates (p < 0.001). A meta-analysis of available data showed large differences in efficacy ranking in relation to dose selection and type of analysis, but these were mostly nonsignificant due to statistical power limitations.

SIGNIFICANCE

Several methodologic issues hamper the relevance of indirect comparisons of AEDs in the adjunctive-therapy of refractory partial epilepsy. Some of these issues could be overcome by improved standardization in the reporting of efficacy outcomes.

New and investigational antiepileptic drugs

In the last fifteen years, new antiepileptic medications have been offered for the treatment of patients with epilepsy. Nevertheless, despite optimal medical treatment, up to 30% of patients still experience recurrent seizures and the challenge for new, more efficacious and better-tolerated drugs continues. New antiepileptic drugs include the evolution of pre-existing drugs and new compounds identified through the investigation of additional molecular targets, such as SV2A synaptic vesicle protein, voltage-gated potassium channels, ionotropic and metabotropic glutamate receptors, and gap junctions. This paper reviews the available information on various classes of molecules that are in the pipeline as well as on the innovative approaches to the treatment of epilepsy.

Placebo responses in randomized trials of antiepileptic drugs

This meta-analysis of published, randomized, controlled trials (RCTs) of antiepileptic drugs in adults with focal drug-resistant epilepsy was performed to estimate a mean placebo effect, to evaluate variability in placebo response rates, to investigate associations between placebo effect rates and study characteristics, and to determine whether there were changes in placebo response rates over recent years in RCTs (so-called "placebo drift"). One hundred ninety-eight potentially appropriate studies were identified after MEDLINE search and carefully reviewed. Twenty-seven RCTs (with 5662 randomized patients, including 1887 patients in placebo arms) were included in the meta-analysis. A random effects meta-analytic model estimated the pooled placebo response at 12.5% (95% CI: 10.03-14.94%). A statistically significant correlation between baseline median seizure frequency and placebo response rates was not observed. "Placebo drift" was not considered statistically significant.

Placebo-corrected efficacy of modern antiepileptic drugs for refractory epilepsy: systematic review and meta-analysis

Although adjunctive treatment with modern antiepileptic drugs (AEDs) is standard care in refractory epilepsy, it is unclear how much of the effect can be attributed directly to the AEDs and how much to the beneficial changes seen with placebo. Therefore, we performed a systematic review and meta-analysis of the evidence to determine the placebo-corrected net efficacy of adjunctive treatment with modern AEDs on the market for refractory epilepsy. Of 317 potentially eligible articles reviewed in full text, 124 (39%) fulfilled eligibility criteria. After excluding 69 publications, 55 publications of 54 studies in 11,106 adults and children with refractory epilepsy form the basis of evidence. The overall weighted pooled-risk difference in favor of AEDs over placebo for seizure-freedom in the total sample of adults and children was 6% [95% confidence interval (CI) 4-8, z = 6.47, p < 0.001] and 21% (95% CI 19-24, z = 17.13, p < 0.001) for 50% seizure reduction. Although the presence of moderate heterogeneity may reduce the validity of the results and limit generalizations from the findings, we conclude that the placebo-corrected efficacy of adjunctive treatment with modern AEDs is disappointingly small and suggest that better strategies of finding drugs are needed for refractory epilepsy, which is a major public health problem.

Development of new antiepileptic drugs: challenges, incentives, and recent advances

Despite the introduction of many second-generation antiepileptic drugs (AEDs) in the past 15 years, a third of patients with epilepsy remain refractory to available treatments, and newer and more effective therapies are needed. Although our understanding of the mechanisms of drug resistance is fragmented, novel AED targets have been identified, and models of refractory epilepsy have been developed that can help to select candidate compounds for development. There are more than 20 compounds with potential antiepileptic activity in various stages of clinical development, and for many of these promising clinical trial results are already available. Several incentives justify further investment into the discovery of newer and more effective AEDs. Moreover, developments in clinical trial methodology enable easier completion of proof-of-concept studies, earlier definition of the therapeutic potential of candidate compounds, and more efficient completion of trials for various epilepsy indications.

Isobolographic analysis of interactions between losigamone and conventional antiepileptic drugs in the mouse maximal electroshock model

The aim of this study was the isobolographic evaluation of interactions between losigamone (LSG), valproate (VPA), carbamazepine (CBZ), phenytoin (PHT), and phenobarbital (PB) in the maximal electroshock (MES) test in mice. Electroconvulsions were produced by means of an alternating current (ear-clip electrodes, 0.2-s stimulus duration, and tonic hindlimb extension taken as the endpoint). Adverse effects were evaluated in the chimney test (motor coordination) and the passive avoidance task (long-term memory). Brain concentrations of antiepileptic drugs (AEDs) were measured by immunofluorescence or high-performance liquid chromatography. Isobolographic analysis indicated synergistic interactions between LSG and VPA. For example, in the proportion of 1:1 the theoretically calculated 50% effective dose for additivity (ED(50add)) was 138 mg/kg, while the experimentally derived ED(50) for the mixture (ED(50mix)) was 85.2 mg/kg. The difference was significant at p<0.001. LSG combined with CBZ or PHT showed additivity, whereas the combinations of LSG with PB were either additive, for the fixed ratios of 1:3 and 1:1, or antagonistic for the ratio of 3:1 (ED(50add)=18.4 mg/kg versus ED(50mix)=26.7 mg/kg, p<0.05). Impairment of long-term memory was noted only in the case of VPA given at its ED(50), however this AED did not affect motor performance. LSG, CBZ, PHT and PB (applied at their ED(50) values) and co-administration of LSG with conventional AEDs (including VPA) impaired neither motor performance nor long-term memory. LSG did not affect the brain concentration of VPA or PB, but significantly elevated the brain concentrations of CBZ and PHT. In contrast, VPA, CBZ and PHT significantly increased the brain concentration of LSG, indicating a pharmacokinetic contribution to the observed pharmacodynamic interactions. Although LSG exhibited some favorable pharmacodynamic interactions with various AEDs, these were complicated by pharmacokinetic interactions and emphasize the importance of measuring AED concentrations in studies designed to identify desirable AED combinations.