Cardiac sodium channel inhibition by lamotrigine: in vitro characterization and clinical implications

Lamotrigine, approved for use as an antiseizure medication (ASM) as well as the treatment of bipolar disorder, inhibits sodium channels in the brain to reduce repetitive neuronal firing and pathological release of glutamate. The shared homology of sodium channels and lack of selectivity associated with channel blocking agents can cause slowing of cardiac conduction and increased proarrhythmic potential. The Vaughan-Williams classification system differentiates sodium channel blockers using biophysical properties of binding. As such, Class Ib inhibitors including mexiletine do not slow cardiac conduction as measured by the electrocardiogram (ECG), at therapeutically relevant exposure. Our goal was to characterize the biophysical properties of NaV 1.5 block and to support the observed clinical safety of lamotrigine. We used HEK-293 cells stably expressing the hNaV 1.5 channel and voltage clamp electrophysiology to quantify the potency (IC50 ) against peak and late channel current, on-/off-rate binding kinetics, voltage-dependence and tonic block of the cardiac sodium channel by lamotrigine; and compared to clinically relevant Class Ia (quinidine), Ib (mexiletine) and Ic (flecainide) inhibitors. Lamotrigine blocked peak and late NaV 1.5 current at therapeutically relevant exposure, with rapid kinetics and biophysical properties similar to the Class Ib inhibitor mexiletine. However, no clinically meaningful prolongation in QRS or PR interval was observed in healthy subjects in a new analysis of a previously reported thorough QT clinical trial (SCA104648). In conclusion, the weak NaV 1.5 block and rapid kinetics do not translate into clinically relevant conduction slowing at therapeutic exposure and support the clinical safety of lamotrigine in patients suffering from epilepsy and bipolar disorder

Albiglutide efficacy and safety in the Latino/Hispanic subpopulation for the integrated phase III program

<p><b>Objective</b>: to evaluate the efficacy and safety of albiglutide compared with placebo and active comparators from an integrated trial subpopulation of Latino/Hispanic patients whose type 2 diabetes mellitus (T2DM) was inadequately controlled on their current regimen of diet and exercise, with or without oral antidiabetic drugs (OADs) and/or insulin.</p> <p><b>Methods</b>: Latino/Hispanic patient subpopulations (N = 1204) across 7 phase III albiglutide studies (N = 4400) were evaluated post-hoc for efficacy and safety. Comparators were placebo, sulfonylureas, insulin, thiazolidinediones, and dipeptidyl peptidase-4 inhibitors. Glycatedhemoglobin (HbA_1c) change from baseline to the time of the primary endpoint assessment (from 26 to 104 weeks) was evaluated in patients on diet and exercise and/or OADs, with or without insulin. Patients were allowed to continue in the study if hyperglycemic rescue was required, according to a prespecified algorithm and at the discretion of the investigator.</p> <p><b>Results</b>: At baseline in the Latino/Hispanic subpopulation, the mean HbA_1c was 8.3%, mean age was 53 years, mean body mass index was 32 kg/m², and mean duration of T2DM was 8.0 years. The primary endpoint of mean HbA_1c difference (albiglutide – placebo) was −0.94% for the Latino/Hispanic subpopulation and −0.86% (<i>p </i>< 0.001) for the overall phase III population. Changes in fasting plasma glucose mirrored those of HbA_1c. Weight loss with albiglutide was numerically greater than with OADs and insulin in both populations, but it was smaller than with liraglutide. Within the Latino/Hispanic subpopulation, more injection-site reactions were reported with albiglutide vs all comparators, while gastrointestinal and hypoglycemic adverse events were comparable between the two groups, and the latter was uncommon when used without insulin and/or a sulfonylurea.</p> <p><b>Conclusions</b>: In the Latino/Hispanic population, albiglutide resulted in effective lowering of glucose and modest weight loss, and it was generally well tolerated.</p