Specific binding of lacosamide to collapsin response mediator protein 2 (CRMP2) and direct impairment of its canonical function: implications for the therapeutic potential of lacosamide

Inhibition of ERK1/2 or CRMP2 Disrupts Alcohol Memory Reconsolidation and Prevents Relapse in Rats

Relapse to alcohol abuse, often caused by cue-induced alcohol craving, is a major challenge in alcohol addiction treatment. Therefore, disrupting the cue-alcohol memories can suppress relapse. Upon retrieval, memories transiently destabilize before they reconsolidate in a process that requires protein synthesis. Evidence suggests that the mammalian target of rapamycin complex 1 (mTORC1), governing the translation of a subset of dendritic proteins, is crucial for memory reconsolidation. Here, we explored the involvement of two regulatory pathways of mTORC1, phosphoinositide 3-kinase (PI3K)-AKT and extracellular regulated kinase 1/2 (ERK1/2), in the reconsolidation process in a rat (Wistar) model of alcohol self-administration. We found that retrieval of alcohol memories using an odor-taste cue increased ERK1/2 activation in the amygdala, while the PI3K-AKT pathway remained unaffected. Importantly, ERK1/2 inhibition after alcohol memory retrieval impaired alcohol-memory reconsolidation and led to long-lasting relapse suppression. Attenuation of relapse was also induced by post-retrieval administration of lacosamide, an inhibitor of collapsin response mediator protein-2 (CRMP2)-a translational product of mTORC1. Together, our findings indicate the crucial role of ERK1/2 and CRMP2 in the reconsolidation of alcohol memories, with their inhibition as potential treatment targets for relapse prevention.

Efficacy, tolerability and safety of add-on third-generation antiseizure medications in treating focal seizures worldwide: a network meta-analysis of randomised, placebo-controlled trials

Background

Adjunctive newer antiseizure medications (ASMs) are being used in patients with treatment-resistant focal-onset seizures (FOS). An updated network meta-analysis (NMA) was necessary to compile evidence in this critical area.

Methods

We systematically searched PubMed, Embase, Cochrane Library, Web of Science, and Scopus from their inception until 17 January 2024, evaluating the efficacy, tolerability, and safety of rufinamide (RUF), brivaracetam (BRV), cenobamate (CNB), eslicarbazepine (ESL), lacosamide (LCM), retigabine (RTG), and perampanel (PER) as adjunctive treatments for FOS. Efficacy outcomes included seizure response and seizure freedom. Tolerability was assessed by discontinuation due to adverse events (AEs). Safety outcomes were evaluated based on the number of patients experiencing at least one AE and serious adverse events (SAEs). This review is registered with PROSPERO (CRD42023485130).

Findings

A total of 29 studies involving 11,750 participants were included. For seizure response, all ASMs were significantly superior to placebo, with RTG ranking highest, followed by CNB. Considering dosage, CNB 400 mg/d was top-ranked, followed by RTG 1200 mg/d. For seizure freedom, BRV was highest-ranked, followed by CNB, with BRV 100 mg/d leading, followed by CNB 400 mg/d. Regarding tolerability, LCM 600 mg/d had the lowest ranking, followed by CNB 400 mg/d. For the safety outcome of AEs, ESL 1200 mg/d was ranked lowest, followed by CNB 400 mg/d. Regarding SAEs, LCM 400 mg/d was ranked lowest, followed by RTG 1200 mg/d.

Interpretation

ASMs at different dosages have varying efficacy and tolerability profiles. We have provided hierarchical rankings of ASMs for efficacy and safety outcomes. Our findings offer the most comprehensive evidence available to inform patients, families, physicians, guideline developers, and policymakers about the choice of ASMs in patients with treatment-resistant FOS.

Funding

None.

Real-world safety of Lacosamide: A pharmacovigilance study based on spontaneous reports in the FDA adverse event reporting system

INTRODUCTION

Lacosamide is licensed for the treatment of focal seizures in both adults and children, however there is little information available on its adverse reactions. Using the FDA Adverse Event Reporting System (FAERS), we seek to assess adverse occurrences that may be related to Lacosamide.

METHODS

On the basis of the FAERS database from the fourth quarter of 2008 to the second quarter of 2022, disproportionality analysis was carried out using the reporting odds ratio (ROR) method, the United Kingdom Medicines and Healthcare Products Regulatory Agency omnbius standard (MHRA) method, and the bayesian confidence propagation neural network (BCPNN) method. We extracted valuable positive signals for designated medical event (DME) screening, focused on the evaluation and comparison of safety signals appearing in DME with system organ classification (SOC) analysis.

RESULTS

A total of 10,226 adverse reaction reports with Lacosamide as the primary suspect drug were obtained, with 30,960 reported cases, detecting 232 valuable positive signals, involving a total of 20 SOCs, of which the most frequently reported SOCs were nervous system disorders (6537 cases, 55.21%), psychiatric disorders (1530 cases, 12.92%), injury poisoning and procedural complications (1059 cases, 8.94%). According to 232 valuable positive signals with DME screening results, two signals of stevens-johnson syndrome and ventricular fibrillation were consistent with PT signals on the DME list, with the two SOCs focusing on skin and subcutaneous tissue disorders and cardiac disorders, respectively.

CONCLUSIONS

Our research demonstrates that the clinical use of Lacosamide should be noticed and avoided in relation to ADRs since it raises the risk of cardiac arrest, ventricular fibrillation, stevens-johnson syndrome, and rhabdomyolysis.

Efficacy and tolerability of lacosamide as adjunctive therapy in patients with focal-onset seizures: an observational, prospective study

PURPOSE

To evaluate the efficacy and tolerability of adjunctive lacosamide (LCM) in patients with focal-onset seizures, with or without combined secondarily generalized seizures.

METHODS

106 patients aged ≥ 16 years were recruited consecutively in this single-center prospective observational study. All patients received LCM as an add-on treatment on the basis of clinical judgement. Seizure frequency, adverse events (AEs) and retention rates were obtained at 3 and 6 months after LCM introduction.

RESULT

The overall response rates were 53.3 and 70.4% after 3 and 6 months, respectively, and the freedom of seizures at the same points was reached at 19 and 26.5%. The retention rates were 99.1% at the 3-month follow-up and 93.3% at the 6-month follow-up. The overall incidence of adverse events was 35.8%. The leading AEs were dizziness (16.98%) and sedation (6.6%).

CONCLUSIONS

Our study confirmed the efficacy and tolerability of adjunctive LCM in Chinese patients in real-life conditions. Based on our treatment experience, a universal maintenance dose of LCM would be needed in Chinese patients.

Response of focal refractory status epilepticus to lacosamide in an infant

Status epilepticus (SE) is a life-threatening medical emergency which is frequently encountered in the critical care setting and can be refractory to treatment. Refractory status epilepticus (RSE) is defined as SE that has failed to respond to adequately used first-line and second-line antiepileptic medications. Super refractory status epilepticus is defined as SE that persists for 24 hours or more after the use of an anaesthetic agent or recurs after its withdrawal.If SE persists beyond a period of 7 days it is referred to as prolonged, refractory status epilepticus (PRSE). There are limited data guiding treatment of RSE in the paediatric population.Lacosamide (LCM) is licensed as an adjunctive treatment for partial-onset seizures. Evidence for the efficacy of LCM in paediatric SE is scarce. This case report may suggest a synergistic effect of LCM on slow-activation sodium channels in conjunction with medications such as phenytoin that causes fast inactivation of sodium channels. The dual fast and slow inactivation of sodium channels may enhance the effectiveness in treatment of RSE. This is the first case report of PRSE in an infant, successfully treated with LCM. A brief review of literature is also a part of this report.

Topical Therapeutic Options in Corneal Neuropathic Pain

Purpose of Review: Corneal neuropathic pain can be difficult to treat, particularly due to its lack of response to standard dry eye therapies. We describe a variety of topical therapeutic options that are available to treat corneal neuropathic pain with a significant or primary peripheral component. We also describe possible mechanisms of action for such topical therapies.

Recent Findings: Topical corticosteroids and blood-derived tear preparations can be helpful. Newer therapies, including topical lacosamide and low-dose naltrexone are emerging therapeutic options that may also be considered.

Summary: Corneal neuropathic pain with a significant peripheral component may be managed with a variety of topical therapeutic options.

Clinical Efficacy and Safety of Lacosamide as an Adjunctive Treatment in Adults With Refractory Epilepsy

Background: Lacosamide (LCM), a novel AED (antiepileptic drug), was used as an adjunctive treatment in patients with partial-onset seizures or without secondary generalization. However, no meta-analysis was performed to evaluate the efficacy of LCM as an adjunctive treatment in post-marketing clinical studies.

Aims: To assess the safety and efficacy of LCM as an adjunctive treatment in adults with refractory epilepsy, a systematic review and meta-analysis of randomized controlled trials (RCTs) and real-world studies were performed.

Methods: All studies were identified from electronic databases. Both RCTs and observational prospective studies were included. Primary outcomes included responder rate, adverse effects (AEs) and withdraw rate. The pooled rates (PR) with their corresponding 95% confidence intervals (CI) were calculated. Publication bias was assessed with Begg's or Egger's tests.

Results: Total 16 studies (3,191 patients) including 5 RCTs and 11 real-word studies were enrolled. The pooled 50% responder rate and seizure-free rate were 48% (95% CI: 0.42, 0.54) and 9% (95% CI: 0.06, 0.11) in all studies, respectively. Subgroup analysis showed that the pooled 50% responder rate were 53% (95% CI: 0.44, 0.62) from observational studies and 38% (95% CI: 0.35, 0.42) from RCTs, respectively; the pooled seizure-free rate were 13% (95% CI: 0.09, 0.18) from observational studies and 4% (95% CI: 0.06, 0.11) from RCTs, respectively. Similar incidence of AEs were reported in real-world studies (0.57, 95% CI: 0.43, 0.72) and RCTs (0.59, 95% CI: 0.42–0.76). Finally, a total of 13% (95%CI: 0.09, 0.16) and 13% (95% CI: 0.08, 0.16) of all patients prescribed with LCM was withdrawn in RCTs and real-world studies, respectively, due to the occurrence of AEs. Furthermore, similar to the 50% responder rate, seizure-free rate, incidence of AEs and withdraw rate were reported at 6-month or at least 12-month of LCM adjunction. Publication bias was not detected in these studies.

Conclusions: Our results revealed that LCM adjunctive therapy even with long-term treatment was efficacious and well tolerated in adults with refractory epilepsy.

Identification of New Compounds with Anticonvulsant and Antinociceptive Properties in a Group of 3-substituted (2,5-dioxo-pyrrolidin-1-yl)(phenyl)-Acetamides

We report herein a series of water-soluble analogues of previously described anticonvulsants and their detailed in vivo and in vitro characterization. The majority of these compounds demonstrated broad-spectrum anticonvulsant properties in animal seizure models, including the maximal electroshock (MES) test, the pentylenetetrazole-induced seizure model (scPTZ), and the psychomotor 6 Hz (32 mA) seizure model in mice. Compound 14 showed the most robust anticonvulsant activity (ED₅₀ MES = 49.6 mg/kg, ED₅₀ 6 Hz (32 mA) = 31.3 mg/kg, ED₅₀scPTZ = 67.4 mg/kg). Notably, it was also effective in the 6 Hz (44 mA) model of drug-resistant epilepsy (ED₅₀ = 63.2 mg/kg). Apart from favorable anticonvulsant properties, compound 14 revealed a high efficacy against pain responses in the formalin-induced tonic pain, the capsaicin-induced neurogenic pain, as well as in the oxaliplatin-induced neuropathic pain in mice. Moreover, compound 14 showed distinct anti-inflammatory activity in the model of carrageenan-induced aseptic inflammation. The mechanism of action of compound 14 is likely complex and may result from the inhibition of peripheral and central sodium and calcium currents, as well as the TRPV1 receptor antagonism as observed in the in vitro studies. This lead compound also revealed beneficial in vitro ADME-Tox properties and an in vivo pharmacokinetic profile, making it a potential candidate for future preclinical development. Interestingly, the in vitro studies also showed a favorable induction effect of compound 14 on the viability of neuroblastoma SH-SY5Y cells.

C-11, a New Antiepileptic Drug Candidate: Evaluation of the Physicochemical Properties and Impact on the Protective Action of Selected Antiepileptic Drugs in the Mouse Maximal Electroshock-Induced Seizure Model

C-11 is a hybrid compound derived from 2-(2,5-dioxopyrrolidin-1-yl) propanamide, with a wide spectrum of anticonvulsant activity and low neurotoxicity. The aim of this study was to determine the effects of C-11 on the protective action of various antiepileptic drugs (i.e., carbamazepine CBZ, lacosamide LCM, lamotrigine LTG, and valproate VPA) against maximal electroshock-induced seizures (MES) in mice, as well as its neuroprotective and physicochemical/pharmacokinetic properties. Results indicate that C-11 (30 mg/kg, i.p.) significantly enhanced the anticonvulsant action of LCM (p < 0.001) and VPA (p < 0.05) but not that of CBZ and LTG in the MES test. Neither C-11 (30 mg/kg) alone nor its combination with other anticonvulsant drugs (at their ED₅₀ values from the MES test) affected motor coordination; skeletal muscular strength and long-term memory, as determined in the chimney; grip strength and passive avoidance tests, respectively. Pharmacokinetic characterization revealed that C-11 had no impact on total brain concentrations of LCM or VPA in mice. Qualitative analysis of neuroprotective properties of C-11, after a single administration of pilocarpine, revealed no protective effect of this substance in the tested animals. Determination of physicochemical descriptors showed that C-11 meets the drug-likeness requirements resulting from Lipinski and Veber’s rules and prediction of gastrointestinal absorption and brain penetration, which is extremely important for the CNS-active compounds.

Pharmacology of lacosamide: From its molecular mechanisms and pharmacokinetics to future therapeutic applications

Epilepsy is one of the most common brain disorders, affecting more than 50 million people worldwide. Although its treatment is currently symptomatic, the last generation of anti-seizure drugs is characterized by better pharmacokinetic profiles, efficacy, tolerability and safety. Lacosamide is a third-generation anti-seizure drug that stands out due to its good efficacy and safety profile. It is used with effectiveness in the treatment of partial-onset seizures with or without secondary generalization, primary generalized tonic-clonic seizures and off-label in status epilepticus. Despite scarcely performed until today, therapeutic drug monitoring of lacosamide is proving to be advantageous by allowing the control of inter and intra-individual variability and promoting a successful personalized therapy, particularly in special populations. Herein, the pharmacology, pharmacokinetics, and clinical data of lacosamide were reviewed, giving special emphasis to the latest molecular investigations underlying its mechanism of action and therapeutic applications in pathologies besides epilepsy. In addition, the pharmacokinetic characteristics of lacosamide were updated, as well as current literature concerning the high pharmacokinetic variability observed in special patient populations and that must be considered during treatment individualization.

Identification of Proteins Deregulated by Platinum-Based Chemotherapy as Novel Biomarkers and Therapeutic Targets in Non-Small Cell Lung Cancer

Platinum-based chemotherapy remains the cornerstone of treatment for most people with non-small cell lung cancer (NSCLC), either as adjuvant therapy in combination with a second cytotoxic agent or in combination with immunotherapy. Resistance to therapy, either in the form of primary refractory disease or evolutionary resistance, remains a significant issue in the treatment of NSCLC. Hence, predictive biomarkers and novel combinational strategies are required to improve the effectiveness and durability of treatment response 6for people with NSCLC. The aim of this study was to identify novel biomarkers and/or druggable proteins from deregulated protein networks within non-oncogene driven disease that are involved in the cellular response to cisplatin. Following exposure of NSCLC cells to cisplatin, in vitro quantitative mass spectrometry was applied to identify altered protein response networks. A total of 65 proteins were significantly deregulated following cisplatin exposure. These proteins were assessed to determine if they are druggable targets using novel machine learning approaches and to identify whether these proteins might serve as prognosticators of platinum therapy. Our data demonstrate novel candidates and drug-like molecules warranting further investigation to improve response to platinum agents in NSCLC.

Neuroproteomics in Epilepsy: What Do We Know so Far?

Epilepsies are chronic neurological diseases that affect approximately 2% of the world population. In addition to being one of the most frequent neurological disorders, treatment for patients with epilepsy remains a challenge, because a proportion of patients do not respond to the antiseizure medications that are currently available. This results in a severe economic and social burden for patients, families, and the healthcare system. A characteristic common to all forms of epilepsy is the occurrence of epileptic seizures that are caused by abnormal neuronal discharges, leading to a clinical manifestation that is dependent on the affected brain region. It is generally accepted that an imbalance between neuronal excitation and inhibition generates the synchronic electrical activity leading to seizures. However, it is still unclear how a normal neural circuit becomes susceptible to the generation of seizures or how epileptogenesis is induced. Herein, we review the results of recent proteomic studies applied to investigate the underlying mechanisms leading to epilepsies and how these findings may impact research and treatment for these disorders.

Advances toward precision medicine for bipolar disorder: mechanisms & molecules

Given its chronicity, contribution to disability and morbidity, and prevalence of more than 2%, the effective treatment, and prevention of bipolar disorder represents an area of significant unmet medical need. While more than half a century has passed since the introduction of lithium into widespread use at the birth of modern psychopharmacology, that medication remains a mainstay for the acute treatment and prevention of recurrent mania/hypomania and depression that characterize bipolar disorder. However, the continued limited understanding of how lithium modulates affective behavior and lack of validated cellular and animal models have resulted in obstacles to discovering more effective mood stabilizers with fewer adverse side effects. In particular, while there has been progress in developing new pharmacotherapy for mania, developing effective treatments for acute bipolar depression remain inadequate. Recent large-scale human genetic studies have confirmed the complex, polygenic nature of the risk architecture of bipolar disorder, and its overlap with other major neuropsychiatric disorders. Such discoveries have begun to shed light on the pathophysiology of bipolar disorder. Coupled with broader advances in human neurobiology, neuropharmacology, noninvasive neuromodulation, and clinical trial design, we can envision novel therapeutic strategies informed by defined molecular mechanisms and neural circuits and targeted to the root cause of the pathophysiology. Here, we review recent advances toward the goal of better treatments for bipolar disorder, and we outline major challenges for the field of translational neuroscience that necessitate continued focus on fundamental research and discovery.

The effects of lacosamide on cognitive function and psychiatric profiles in patients with epilepsy

BACKGROUND

Cognitive and psychiatric problems are common in people with epilepsy. They can have multiple causes, including structural brain lesions, the active epilepsy, and the effect of anti-epileptic therapy. Since patients' treatment compliance and quality of life are affected by cognitive and emotional status, it is crucial for clinicians to understand how anti-seizure medications (ASMs) affect cognition and mood, and to choose the proper ASM.

OBJECTIVE

To conduct a literature review of the impact on cognition and mood status of lacosamide (LCM) in people with epilepsy.

METHODS

Wesearched PubMed, the Cochrane Database of Systematic Reviews and reference lists of articles for all types of articles with no limitations on publication date.

RESULTS

A total of 251 records were obtained, including 247 articles in PubMed and 4 articles from reference lists. We included 2 meta-analyses, one randomized controlled trials and 14 observational studies after the screening process. Most studies agree LCM has low risk of treatment-emergent adverse events (TEAEs) on cognition. Comparisons with other ASMs, LCM may be preferable to carbamazepine, topiramate and perampanel, and not inferior to lamotrigine. In spite of low incident rate, depression is the most common psychiatric change of LCM. There are no consistent positive or negative psychiatric effects of LCM.

CONCLUSION

Lacosamide has limited impact on cognitive and mood status in this review. Several factors including mechanism of co-administration of ASMs and personal history of psychiatric disorder should be considered as important in the development of cognitive and psychiatric side effects. However, the heterogeneity between studies make the quality of evidence weaker and further trials are needed.

Effects of levetiracetam and lacosamide on therapeutic efficacy and neural function in patients with epilepsy

The present study aimed to investigate the effects of levetiracetam tablets and lacosamide (LCM) on therapeutic efficacy and neural function in patients with epilepsy. We assigned 252 patients with refractory partial seizures admitted to our hospital to receive either levetiracetam tablets [120 patients, the control group (CG)] or levetiracetam tablets combined with LCM [132 patients, the joint group (JG)]. The bone mineral density and neural function between the two groups at 6 months before and after treatment were compared. The total response rate was higher in the JG than in the CG (P<0.05). There was no significant difference in the comparison of the multiple indexes between the two groups before treatment (P>0.05). The frequency of seizures was reduced after treatment in the two groups, however, it was lower in the JG compared with the CG (P<0.05). The levels of neurological indicators were significantly reduced after treatment in the two groups (P<0.05), however, the reduction was more marked in the JG than in the CG. The bone mineral density (BMD) of the femoral neck decreased after treatment in the two groups (P<0.05), but there was no difference between the two groups after treatment (P>0.05). The calcium content decreased after treatment in the two groups (P<0.05), but there was no difference between the two groups after treatment (P>0.05). The comparison of other bone metabolism markers between the two groups exhibited no significant differences. The combination therapy greatly increased the quality of life score and the 1-year drug retention rate. To sum up, levetiracetam tablets combined with LCM significantly enhanced the therapeutic effect and improved the neural function in patients with refractory partial seizures, however this therapy may cause a slight adverse effect on BMD and bone metabolism in the short term.

Druggability of CRMP2 for Neurodegenerative Diseases

Collapsin response mediator proteins (CRMPs) are ubiquitously expressed phosphoproteins that coordinate cytoskeletal formation and regulate cellular division, migration, polarity, and synaptic connection. CRMP2, the most studied of the five family members, is best known for its affinity for tubulin heterodimers and function in regulating the microtubule network. Accumulating evidence has also demonstrated a key role for CRMP2 in trafficking of voltage- and ligand-gated ion channels. These functions are tightly regulated by post-translational modifications including phosphorylation and SUMOylation (addition of a small ubiquitin like modifier). Over the past decade, it has become increasingly clear that dysregulated post-translational modifications of CRMP2 contribute to the pathomechanisms of diverse diseases, including cancer, neurodegenerative diseases, chronic pain, and bipolar disorder. Here, we review the discovery, functions, and current putative preclinical and clinical therapeutics targeting CRMP2. These potential therapeutics include CRMP2-based peptides that inhibit protein-protein interactions and small-molecule compounds. Capitalizing on the availability of structural information, we identify druggable pockets on CRMP2 and predict binding modes for five known CRMP2-targeting compounds, setting the stage for optimization and de novo drug discovery targeting this multifunctional protein.

Role of Lacosamide in Preventing Pentylenetetrazole Kindling-Induced Alterations in the Expression of the Gamma-2 Subunit of the GABAA Receptor in Rats

Background:

Epilepsy remains challenging to treat still no etiologic treatment has been identified, however, some antiepileptic drugs (AEDs) are able to modify the pathogenesis of the disease. Lacosamide (LCM) has been shown to possess complex anticonvulsant and neuroprotective actions, being an enhancer of the slow inactivation of voltage-gated sodium channels, and it has the potential to prevent epileptogenesis. Recent evidence has shown that LCM indirectly improves the function of GABAA receptors. Receptors at most GABAergic synapses involve the gamma-2 subunit, which contributes to both phasic and tonic inhibition, and its presence assures benzodiazepine sensitivity. Moreover, mutant gamma-2 subunits were associated with generalized epilepsy syndromes. In animal models, the expression of the gamma-2 subunit of the gamma-aminobutyric acid A receptor (GABAAg2) was shown to be increased in pentylenetetrazole (PTZ)-induced chemical kindling in Wistar rats.

Objective:

This study hypothesized that LCM might affect the kindling process by influencing the expression of GABAA receptors in the hippocampus.

Methods:

The gene and protein expression levels of the GABAAg2 were studied using RT-qPCR and immunofluorescent staining.

Results:

It was found that LCM treatment (10 mg/kg i.p. daily for 57 days) reduced the maximal intensity of the PTZ-induced seizures but did not prevent kindling. On the other hand, LCM treatment reverted the increase of mRNA expression of GABAAg2 in the hippocampus and prevented the decrease of GABAAg2 protein in the hippocampal CA1 region.

Conclusion:

LCM could exhibit modulatory effects on the GABAergic system of the hippocampus that may be independent of the anticonvulsant action.

Differential effect of lacosamide on Nav1.7 variants from responsive and non-responsive patients with small fibre neuropathy

Small fibre neuropathy is a common pain disorder, which in many cases fails to respond to treatment with existing medications. Gain-of-function mutations of voltage-gated sodium channel Na_v1.7 underlie dorsal root ganglion neuronal hyperexcitability and pain in a subset of patients with small fibre neuropathy. Recent clinical studies have demonstrated that lacosamide, which blocks sodium channels in a use-dependent manner, attenuates pain in some patients with Na_v1.7 mutations; however, only a subgroup of these patients responded to the drug. Here, we used voltage-clamp recordings to evaluate the effects of lacosamide on five Na_v1.7 variants from patients who were responsive or non-responsive to treatment. We show that, at the clinically achievable concentration of 30 μM, lacosamide acts as a potent sodium channel inhibitor of Na_v1.7 variants carried by responsive patients, via a hyperpolarizing shift of voltage-dependence of both fast and slow inactivation and enhancement of use-dependent inhibition. By contrast, the effects of lacosamide on slow inactivation and use-dependence in Na_v1.7 variants from non-responsive patients were less robust. Importantly, we found that lacosamide selectively enhances fast inactivation only in variants from responders. Taken together, these findings begin to unravel biophysical underpinnings that contribute to responsiveness to lacosamide in patients with small fibre neuropathy carrying select Na_v1.7 variants.

Effects of Carbamazepine, Lacosamide and Zonisamide on Gliotransmitter Release Associated with Activated Astroglial Hemichannels

Recent studies using the genetic partial epilepsy model have demonstrated that hyperfunction of astroglial hemichannels contributes to pathomechanism of epileptic seizure. Therefore, to explore the novel anticonvulsive mechanisms, the present study determined the effects of voltage-dependent Na⁺ channel (VDSC)-inhibiting anticonvulsants, carbamazepine (CBZ), lacosamide (LCM), and zonisamide (ZNS) on the astroglial release of l-glutamate and adenosine triphosphate (ATP). The effects of subchronic administration of therapeutic-relevant dose of three anticonvulsants on the release of l-glutamate and ATP in the orbitofrontal cortex (OFC) were determined using microdialysis. The concentration-dependent effects of acute and subchronic administrations of anticonvulsants on astroglial gliotransmitter release were determined using primary cultured astrocytes. The concentration-dependent effects of subchronic administrations of anticonvulsants on connexin43 (Cx43) expression in the plasma membrane of primary cultured astrocytes were determined using the Simple Western system. An increase in the levels of extracellular K⁺ resulted in a concentration-dependent increase in the astroglial release of l-glutamate and ATP. The depleted levels of extracellular Ca²⁺ alone did not affect astroglial gliotransmitter release but did accelerate K⁺-evoked gliotransmitter release via activation of astroglial hemichannels. Both non-selective hemichannel inhibitor carbenoxolone (CBX) and selective Cx43 inhibitor GAP19 prevented both gliotransmitter release through activated astroglial hemichannels and the hemichannel-activating process induced by elevation of the levels of extracellular K⁺ with depletion of the levels of extracellular Ca²⁺. ZNS subchronically decreased Cx43 expression and acutely/subchronically inhibited Cx43 hemichannel activity. LCM acutely inhibited hemichannel activity but did not subchronically affect Cx43 expression. Therapeutic-relevant concentration of CBZ did not affect hemichannel activity or Cx43 expression, but supratherapeutic concentration of CBZ decreased Cx43 expression and hemichannel activity. Therefore, the present study demonstrated the distinct effects of CBZ, LCM, and ZNS on gliotransmitter release via modulation of astroglial hemichannel function. The different features of the effects of three VDSC-inhibiting anticonvulsants on astroglial transmission associated with hemichannels, at least partially, possibly contributing to the formation of the properties of these three anticonvulsants, including the antiepileptic spectrum and adverse effects regarding mood and cognitive disturbance.

Evaluation of the impact of compound C11 a new anticonvulsant candidate on cognitive functions and hippocampal neurogenesis in mouse brain

Searching for the new and effective anticonvulsants in our previous study we developed a new hybrid compound C-11 derived from 2-(2,5-dioxopyrrolidin-1-yl) propanamide. C11 revealed high efficacy in acute animal seizure models such as the maximal electroshock model (MES), the pentylenetetrazole model (PTZ) and the 6 Hz (6 Hz, 32 mA) seizure model, as well as in the kindling model of epilepsy induced by repeated injection of PTZ in mice. In the aim of further in vivo C11 characterization, in the current studies we evaluated its influence on cognitive functions, neurodegeneration and neurogenesis process in mice after chronical treatment. All experiments were performed on 6 weeks old male C57/BL mice. The following drugs were used: C11, levetiracetam (LEV), ethosuximide (ETS) and lacosamide (LCM). We analyzed proliferation, migration and differentiation of newborn cells as well as neurodegenerative changes in a mouse brain after long-term treatment with aforementioned AEDs. Additionally, we evaluated changes in learning and memory functions in response to chronic C11, LEV, LCM and ETS treatment. C11 as well as LEV and ETS did not disturb the proliferation of newborn cells compared to the control mice, whereas LCM treatment significantly decreased it. Chronic AEDs therapy did not induce significant neurodegenerative changes. Behavioral studies with using Morris Water Maze test did not indicate any disturbances in the spatial learning and memory after C11 as well as LEV and ETS treatment in comparison to the control group except LCM mice where significant dysfunctions in time, distance and direct swim to the platform were observed. Interestingly, results obtained from in vivo MRI spectroscopy showed a statistically significant increase of one of the neurometabolites- N-acetyloaspartate (NAA) for LCM and LEV mice. A new hybrid compound C11 in contrast to LCM has no negative impact on the process of neurogenesis and neurodegeneration in the mouse hippocampus. Furthermore, chronic treatment with C11 turned out to have no negative impact on cognitive functions of treated mice, which, is certainly of great importance for further more advanced preclinical and especially clinical trials.

Dysregulation of CRMP2 Post-Translational Modifications Drive Its Pathological Functions

Collapsin response mediator proteins (CRMPs) are a family of ubiquitously expressed, homologous phosphoproteins best known for coordinating cytoskeletal formation and regulating cellular division, migration, polarity, and synaptic connection. CRMP2, the most studied of the five family members, is best known for its affinity for tubulin heterodimers and function in regulating the microtubule network. These functions are tightly regulated by post-translational modifications including phosphorylation, SUMOylation, oxidation, and O-GlcNAcylation. While CRMP2's physiological functions rely mostly on its non-phosphorylated state, dysregulation of CRMP2 phosphorylation and SUMOylation has been reported to be involved in the pathophysiology of multiple diseases including cancer, chronic pain, spinal cord injury, neurofibromatosis type 1, and others. Here, we provide a consolidated update on what is known about CRMP2 signaling and function, first focusing on axonal growth and neuronal polarity, then illustrating the link between dysregulated CRMP2 post-translational modifications and diseases. We additionally discuss the roles of CRMP2 in non-neuronal cells, both in the CNS and regions of the periphery. Finally, we offer thoughts on the therapeutic implications of modulating CRMP2 function in a variety of diseases.

Mammalian target of rapamycin complex 1 and its downstream effector collapsin response mediator protein-2 drive reinstatement of alcohol reward seeking

Alcohol use disorder is a chronic relapsing disease. Maintaining abstinence represents a major challenge for alcohol-dependent patients. Yet the molecular underpinnings of alcohol relapse remain poorly understood. In the present study, we investigated the potential role of the mammalian target of rapamycin complex 1 (mTORC1) in relapse to alcohol-seeking behavior by using the reinstatement of a previously extinguished alcohol conditioned place preference (CPP) response as a surrogate relapse paradigm. We found that mTORC1 is activated in the nucleus accumbens shell following alcohol priming-induced reinstatement of alcohol place preference. We further report that the selective mTORC1 inhibitor, rapamycin, abolishes reinstatement of alcohol place preference. Activation of mTORC1 initiates the translation of synaptic proteins, and we observed that reinstatement of alcohol CPP is associated with increased protein levels of one of mTORC1's downstream targets, collapsin response mediator protein-2 (CRMP2), in the nucleus accumbens. Importantly, the level of mTORC1 activation and CRMP2 expression positively correlate with the CPP score during reinstatement. Finally, we found that systemic administration of the CRMP2 inhibitor, lacosamide, attenuates alcohol priming-induced reinstatement of CPP. Together, our results reveal that mTORC1 and its downstream target, CRMP2, contribute to mechanisms underlying reinstatement of alcohol reward seeking. Our results could have important implications for the treatment of relapse to alcohol use and position the Food and Drug Administration approved drugs, rapamycin and lacosamide, for the treatment of alcohol use disorder.

Α Simple Method for the Determination of Lacosamide in Blood by GC-MS

Lacosamide is a functionalized amino acid with antiepileptic function. Therapeutic drug monitoring (TDM) in patients for lacosamide is critical as it allows clinicians to control epileptic seizures. A single liquid-liquid extraction step was applied for the extraction of lacosamide from whole blood samples which were thereafter analyzed by GC-MS. Optimum extraction conditions were selected on the basis of experiments with various solvents at different pHs, indicating ethyl acetate at pH 12 as the most efficient parameters for the extraction of lacosamide. Method exhibited linearity from 2 to 100 μg/mL with R²  = 0.998. Accuracy and precision were evaluated at three concentrations and found to be within acceptable limits. LOD and LOQ were determined at 0.1 and 0.5 μg/mL, respectively. Lacosamide was found to be stable at storage conditions. The developed method was applied successfully in clinical samples and postmortem blood sample from an overdose case.

Lacosamide modulates collapsin response mediator protein 2 and inhibits mossy fiber sprouting after kainic acid-induced status epilepticus

Mossy fiber sprouting (MFS) and neuronal loss are important pathological features of chronic epilepsy closely related to the development of spontaneous recurrent seizures. However, the pathological mechanism of MFS remains unclear. Collapsin response mediator protein 2 (CRMP2) is a cytoplasmic protein highly expressed in the nervous system and is involved in axon/dendrite specification and axonal growth. It is possibly associated with the development of MFS. Lacosamide (LCM), a novel antiepileptic drug, was recently found to inhibit the CRMP2-mediated neurite outgrowth. Therefore, we studied the relationships between LCM, CRMP2, and MFS, seeking potential therapeutic targets for epileptogenesis and a better understanding of the mechanism of action of LCM. We used kainic acid to induce status epilepticus in an animal model and examined the resultant changes in protein expression by Western blot and changes in histology by specific staining for cell death and MFS. Our results showed that the expression level of CRMP2 was elevated and the expression level of phosphorylated CRMP2 (p-CRMP2) was reduced following status epilepticus. Administration of LCM not only reversed this effect but also suppressed spontaneous recurrent seizures and reduced MFS and loss of hippocampal neurons. This study reveals that, in addition to its antiseizure efficacy, LCM has a neuroprotective effect and inhibits the development of epilepsy. CRMP2 is possibly involved in the mechanism by which LCM suppresses MFS and is expected to be a new therapeutic target for treating epileptogenesis.

Modulation of CRMP2 via (S)-Lacosamide shows therapeutic promise but is ultimately ineffective in a mouse model of CLN6-Batten disease

CLN6-Batten disease is a rare neurodegenerative disorder with no cure, characterized by accumulation of lipofuscin in the lysosome, glial activation, and neuronal death. Here we test the therapeutic efficacy of modulating collapsin response mediator protein 2 (CRMP2) activity via S-N-benzy-2-acetamido-3-methoxypropionamide ((S)-Lacosamide) in a mouse model of CLN6-Batten disease. Promisingly, mouse neuronal cultures as well as Cln6 patient fibroblasts treated with varying concentrations of (S)-Lacosamide showed positive restoration of lysosomal associated deficits. However, while acute in vivo treatment enhanced glial activation in 3-month-old Cln6 mutant mice, chronic treatment over several months did not improve behavioral or long-term survival outcomes. Therefore, modulation of CRMP2 activity via (S)-Lacosamide alone is unlikely to be a viable therapeutic target for CLN6-Batten disease.

Lacosamide Overdose: A Case of QRS Prolongation and Seizure

BACKGROUND

Lacosamide is a third-generation antiepileptic drug. Its likely mechanism of action is via neuronal sodium channel blockade, via a unique manner compared with other antiepileptic drugs that block sodium channels. A paucity of information exists regarding lacosamide overdosage. Lacosamide overdosage is thought to cause QRS prolongation and seizures, due to its effect of sodium channel blockade. The potential efficacy of sodium bicarbonate to reverse the effects of lacosamide has not been well studied. Furthermore, prior reports of lacosamide toxicity have occurred in the setting of concomitant polypharmacy. Thus, the isolated toxic effects of the drug have not been well elucidated.

CASE REPORT

We report a case of a suspected, single-ingestion overdose on lacosamide. The patient developed signs of cardiotoxicity and seizure. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: After lacosamide overdosage, the emergency physician must be capable of acute management of subsequent lacosamide toxicity. Understanding the mechanisms of action causing toxicity due to this drug can help the clinician to anticipate the interventions that may be needed or useful to treat this potentially toxic ingestion.

Lacosamide in bipolar disorder: A 30-day comparison to a retrospective control group treated with other antiepileptics

AIM

Bipolar disorder (BD) is often treated with anticonvulsants. Lacosamide has not been tested in BD. We assessed its effects in a hospital setting in patients with BD without epilepsy.

METHODS

We treated 102 consecutive hospitalized patients with acute BD with lacosamide 50-300 mg/day. We compared this sample with a retrospective sample treated with other antiepileptics (OAE). We rated patients after 3, 7, 15, and 30 days of treatment with the Brief Psychiatric Rating Scale, Young Mania Rating Scale, Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale, Clinical Global Impressions - Severity, and Global Assessment of Functioning.

RESULTS

Patients receiving lacosamide were significantly younger and had fewer mixed episodes at intake, and less substance use disorder comorbidity than those receiving OAE. Both groups showed positive effects on all measures. The two groups did not differ on any clinical measure at baseline, but from the 3rd day on, lacosamide patients fared better than OAE patients on the Young Mania Rating Scale and Clinical Global Impressions - Severity and worse on the Hamilton Anxiety Rating Scale. From the 15th day, OAE patients scored better on the Brief Psychiatric Rating Scale. Global Assessment of Functioning scores were significantly more improved in the lacosamide patients. Age, substance use disorder comorbidity, episode type, and educational level significantly affected results. No interactions were found amongst these parameters.

CONCLUSION

Lacosamide was effective in reducing psychopathology, mania, depression, and anxiety and in improving global functioning in patients with BD-I/II disorder in the short term, with few side-effects. Lacosamide improved mania, clinical severity, and global functioning better than OAE at doses lower than those used in epilepsy.

Disruption of the psychiatric risk gene Ankyrin 3 enhances microtubule dynamics through GSK3/CRMP2 signaling

The ankyrin 3 gene (ANK3) is a well-established risk gene for psychiatric illness, but the mechanisms underlying its pathophysiology remain elusive. We examined the molecular effects of disrupting brain-specific Ank3 isoforms in mouse and neuronal model systems. RNA sequencing of hippocampus from Ank3+/- and Ank3+/+ mice identified altered expression of 282 genes that were enriched for microtubule-related functions. Results were supported by increased expression of microtubule end-binding protein 3 (EB3), an indicator of microtubule dynamics, in Ank3+/- mouse hippocampus. Live-cell imaging of EB3 movement in primary neurons from Ank3+/- mice revealed impaired elongation of microtubules. Using a CRISPR-dCas9-KRAB transcriptional repressor in mouse neuro-2a cells, we determined that repression of brain-specific Ank3 increased EB3 expression, decreased tubulin acetylation, and increased the soluble:polymerized tubulin ratio, indicating enhanced microtubule dynamics. These changes were rescued by inhibition of glycogen synthase kinase 3 (GSK3) with lithium or CHIR99021, a highly selective GSK3 inhibitor. Brain-specific Ank3 repression in neuro-2a cells increased GSK3 activity (reduced inhibitory phosphorylation) and elevated collapsin response mediator protein 2 (CRMP2) phosphorylation, a known GSK3 substrate and microtubule-binding protein. Pharmacological inhibition of CRMP2 activity attenuated the rescue of EB3 expression and tubulin polymerization in Ank3-repressed cells by lithium or CHIR99021, suggesting microtubule instability induced by Ank3 repression is dependent on CRMP2 activity. Taken together, our data indicate that ANK3 functions in neuronal microtubule dynamics through GSK3 and its downstream substrate CRMP2. These findings reveal cellular and molecular mechanisms underlying brain-specific ANK3 disruption that may be related to its role in psychiatric illness.

Effectiveness and Adverse Effect of Intravenous Lacosamide in Nonconvulsive Status Epilepticus and Acute Repetitive Seizures in Children

Nonconvulsive status epilepticus (NCSE) and acute repetitive seizures (ARS) are associated with significant morbidity and mortality. Due to the lack of randomized-controlled trials of intravenous antiepileptic drugs (AEDs) in these conditions, trials of a new generation of AEDs in this aspect are needed. A prospective interventional study was conducted in children under 18 years of age with NCSE or ARS who either had contraindication to or were refractory to first-line AEDs and received intravenous lacosamide. Demographic data, the efficacy of treatment, and adverse effects were recorded. Eleven patients with a median age of 11 years, predominantly female (72.7%), were enrolled. Average loading dose was 227 mg (8.3 mg/kg/dose) and average daily maintenance dose was 249 mg (4.6 mg/kg/dose). All patients (100%) experienced a reduction in seizure frequency within 24 hours. Eight of eleven patients (72.7%) experienced a reduction in seizure frequency of more than 50% by the end of the study, and one patient became seizure-free. In terms of adverse events, one patient had a bradycardia without prolongation of the PR interval. Interestingly, there was a case of neuronal ceroid lipofuscinosis in which a significant improvement in seizure control was achieved. The results indicate that intravenous lacosamide may be an alternative treatment for NCSE or ARS in children. To our knowledge, this is the first study on the use of intravenous lacosamide in Asian children. This study is registered to Thai Clinical Trials Registry (TCTR) and the trial registration number is TCTR20180508004.

Across the blood-brain barrier: Neurotherapeutic screening and characterization of naringenin as a novel CRMP-2 inhibitor in the treatment of Alzheimer's disease using bioinformatics and computational tools

The discovery and developmental processes of CNS drugs have been limited by the inability of potential drug molecules to pass through the blood-brain barrier (BBB). This presents a significant setback in the treatment of neurodegenerative disorders such as Alzheimer's disease (AD), hence the need for compounds that can adhere strictly to the selective criteria of suitable CNS drugs. Collapsin response mediator protein-2 (CRMP-2) has been recently identified as a viable target in neurotherapeutics due to its involvement in the etiology of AD. As shown in previous studies, Naringenin (NAR), a small molecule derivative of Drynaria rhizome (DR) extract, specifically binds CRMP-2 and reduces its phosphorylation. This was shown to facilitate axonal regrowth, with improvement in cognition and learning. Herein, we report the first account of the use of cheminformatics techniques to define the CNS drug-suitability of NAR using selective criteria, coupled with the prediction of possible biological activities and toxicities. Also, we evaluated the mechanistic activity of NAR by modeling its molecular interaction with human CRMP-2 (hCRMP-2). Physicochemical analyses revealed the suitability of NAR as a CNS drug and its ability to transverse the BBB. Possible neurogenic, anti-carcinogenic and cardioprotective activities were also predicted. NAR exhibited favorable binding to CRMP-2 and formed strong bonds with active site residues, which accounts for its stabilization and affinity. Moreover, NAR induced notable conformational changes in CRMP-2, an occurrence that could possibly disrupt kinase-mediated phosphorylation. These findings will aid in the optimization of NAR and improve its neurotherapeutic activities in the treatment of AD.

Chronic treatment with the new anticonvulsant drug lacosamide impairs learning and memory processes in rats: A possible role of BDNF/TrkB ligand receptor system

Cognitive impairment is considered a frequent side effect in the drug treatment of epilepsy. The objective of the present study was to investigate the effects of lacosamide (LCM) on learning and memory processes in rats, on the serum level of brain-derived neurotrophic factor (BDNF) and BDNF/TrkB ligand receptor system expression in the hippocampal formation. Male Wistar rats underwent long-term treatment with three different doses of lacosamide - 3 mg/kg (LCM 3), 10 mg/kg (LCM 10) and 30 mg/kg (LCM 30). All rats were subjected to one active and one passive avoidance tests. The BDNF/TrkB immunohistochemical expression in the hippocampus was measured and serum BDNF was determined. The LCM-treated rats made fewer avoidance responses than controls during acquisition training and in the memory retention test. The number of escapes in the LCM 10 and LCM 30 groups decreased throughout the test, while the rats in the LCM 3 group showed fewer escapes only in the memory test in the active avoidance task. In the step-down test, the latency time of the LCM-30 treated rats was reduced as compared with the controls during the learning session and the short- and long-term memory retention tests. Lacosamide induced a dose-dependent reduction of the hippocampal expression of BDNF and its receptor TrkB. We found no significant difference between BDNF serum levels in the test animals and controls. The results of the study suggest that LCM suppresses the learning and memory processes in rats, with the inhibition of hippocampal BDNF/TrkB ligand receptor system being one of the possible mechanisms causing this effect.

Mapping protein interactions of sodium channel NaV1.7 using epitope-tagged gene-targeted mice

The voltage-gated sodium channel NaV1.7 plays a critical role in pain pathways. We generated an epitope-tagged NaV1.7 mouse that showed normal pain behaviours to identify channel-interacting proteins. Analysis of NaV1.7 complexes affinity-purified under native conditions by mass spectrometry revealed 267 proteins associated with Nav1.7 in vivo The sodium channel β3 (Scn3b), rather than the β1 subunit, complexes with Nav1.7, and we demonstrate an interaction between collapsing-response mediator protein (Crmp2) and Nav1.7, through which the analgesic drug lacosamide regulates Nav1.7 current density. Novel NaV1.7 protein interactors including membrane-trafficking protein synaptotagmin-2 (Syt2), L-type amino acid transporter 1 (Lat1) and transmembrane P24-trafficking protein 10 (Tmed10) together with Scn3b and Crmp2 were validated by co-immunoprecipitation (Co-IP) from sensory neuron extract. Nav1.7, known to regulate opioid receptor efficacy, interacts with the G protein-regulated inducer of neurite outgrowth (Gprin1), an opioid receptor-binding protein, demonstrating a physical and functional link between Nav1.7 and opioid signalling. Further information on physiological interactions provided with this normal epitope-tagged mouse should provide useful insights into the many functions now associated with the NaV1.7 channel.

Targeting the intracellular signaling "STOP" and "GO" pathways for the treatment of alcohol use disorders

In recent years, research has identified the molecular and neural substrates underlying the transition of moderate "social" consumption of alcohol to the characteristic alcohol use disorder (AUD) phenotypes including excessive and compulsive alcohol use which we define in the review as the GO signaling pathways. In addition, growing evidence points to the existence of molecular mechanisms that keep alcohol consumption in check and that confer resilience for the development of AUD which we define herein as the STOP signaling pathways. In this review, we focus on examples of the GO and the STOP intracellular signaling pathways and discuss our current knowledge of how manipulations of these pathways may be used for the treatment of AUD.

Lacosamide Reduces Seizure Severity but Increases Seizure Frequency in PTZ-Kindled Rats

Objective: This study evaluated the anticonvulsant action of lacosamide (LCS), a novel drug that was recently approved for the treatment of partial or secondarily generalized seizures, using an animal model of generalized epilepsy induced by repetitive pentylenetetrazole (PTZ) administration in rats. The main goal was to evaluate the behavioral pattern of lacosamide action by classifying seizures according to a modi Racine-scale. Furthermore, the reproducibility of the win-PTZ kindling model of epilepsy, a recently described variant of the standard PTZ-kindling model, was also assessed.

Methods: Adult male Wistar rats (n=16) were divided into two groups and underwent the win-PTZ-kindling protocol in two independent trials. After finishing the kindling procedure, all animals, which presented stage 5 seizures were tested for the anticonvulsant action of lacosamide at three different doses (3, 10, and 30 mg/kg).

Results: The maximal severity of seizures decreased and the latency to stage 3-5 seizures increased when the animals were treated with lacosamide at a single dose of 10 mg/kg compared to saline pretreatment (p < 0.05), both parameter reflecting an anticonvulsant action of the drug. Unfortunately, the number of stage 3-5 seizures also increased, but not significantly. The win-PTZ kindling model showed an adequate reproducibility between different trials, however, the number of fully kindled rats was lower than previously reported.

Conclusions: Lacosamide showed a convincing anticonvulsant action in the win-PTZ kindling model of epilepsy by preventing the generalization of seizures. The win-PTZ kindling model was proved to be useful for studying epileptogenesis and the anticonvulsant action of drugs.

(S)-lacosamide inhibition of CRMP2 phosphorylation reduces postoperative and neuropathic pain behaviors through distinct classes of sensory neurons identified by constellation pharmacology

Chronic pain affects the life of millions of people. Current treatments have deleterious side effects. We have advanced a strategy for targeting protein interactions which regulate the N-type voltage-gated calcium (CaV2.2) channel as an alternative to direct channel block. Peptides uncoupling CaV2.2 interactions with the axonal collapsin response mediator protein 2 (CRMP2) were antinociceptive without effects on memory, depression, and reward/addiction. A search for small molecules that could recapitulate uncoupling of the CaV2.2-CRMP2 interaction identified (S)-lacosamide [(S)-LCM], the inactive enantiomer of the Food and Drug Administration-approved antiepileptic drug (R)-lacosamide [(R)-LCM, Vimpat]. We show that (S)-LCM, but not (R)-LCM, inhibits CRMP2 phosphorylation by cyclin dependent kinase 5, a step necessary for driving CaV2.2 activity, in sensory neurons. (S)-lacosamide inhibited depolarization-induced Ca influx with a low micromolar IC50. Voltage-clamp electrophysiology experiments demonstrated a commensurate reduction in Ca currents in sensory neurons after an acute application of (S)-LCM. Using constellation pharmacology, a recently described high content phenotypic screening platform for functional fingerprinting of neurons that uses subtype-selective pharmacological agents to elucidate cell-specific combinations (constellations) of key signaling proteins that define specific cell types, we investigated if (S)-LCM preferentially acts on certain types of neurons. (S)-lacosamide decreased the dorsal root ganglion neurons responding to mustard oil, and increased the number of cells responding to menthol. Finally, (S)-LCM reversed thermal hypersensitivity and mechanical allodynia in a model of postoperative pain, and 2 models of neuropathic pain. Thus, using (S)-LCM to inhibit CRMP2 phosphorylation is a novel and efficient strategy to treat pain, which works by targeting specific sensory neuron populations.

Collapsin Response Mediator Protein-2 (CRMP2) is a Plausible Etiological Factor and Potential Therapeutic Target in Alzheimer's Disease: Comparison and Contrast with Microtubule-Associated Protein Tau

Alzheimer’s disease (AD) has long been viewed as a pathology that must be caused either by aberrant amyloid-β protein precursor (AβPP) processing, dysfunctional tau protein processing, or a combination of these two factors. This is a reasonable assumption because amyloid-β peptide (Aβ) accumulation and tau hyperphosphorylation are the defining histological features in AD, and because AβPP and tau mutations can cause AD in humans or AD-like features in animal models. Nonetheless, other protein players are emerging that one can argue are significant etiological players in subsets of AD and potentially novel, druggable targets. In particular, the microtubule-associated protein CRMP2 (collapsin response mediator protein-2) bears striking analogies to tau and is similarly relevant to AD. Like tau, CRMP2 dynamically regulates microtubule stability; it is acted upon by the same kinases; collects similarly in neurofibrillary tangles (NFTs); and when sequestered in NFTs, complexes with critical synapse-stabilizing factors. Additionally, CRMP2 is becoming recognized as an important adaptor protein involved in vesicle trafficking, amyloidogenesis and autophagy, in ways that tau is not. This review systematically compares the biology of CRMP2 to that of tau in the context of AD and explores the hypothesis that CRMP2 is an etiologically significant protein in AD and participates in pathways that can be rationally engaged for therapeutic benefit.

mTORC1-dependent translation of collapsin response mediator protein-2 drives neuroadaptations underlying excessive alcohol-drinking behaviors

Mammalian target of rapamycin complex 1 (mTORC1) has an essential role in dendritic mRNA translation and participates in mechanisms underlying alcohol-drinking and reconsolidation of alcohol-related memories. Here, we report that excessive alcohol consumption increases the translation of downstream targets of mTORC1, including collapsin response mediator protein-2 (CRMP-2), in the nucleus accumbens (NAc) of rodents. We show that alcohol-mediated induction of CRMP-2 translation is mTORC1-dependent, leading to increased CRMP-2 protein levels. Furthermore, we demonstrate that alcohol intake also blocks glycogen synthase kinase-3β (GSK-3β)-phosphorylation of CRMP-2, which results in elevated binding of CRMP-2 to microtubules and a concomitant increase in microtubule content. Finally, we show that systemic administration of the CRMP-2 inhibitor lacosamide, or knockdown of CRMP-2 in the NAc decreases excessive alcohol intake. These results suggest that CRMP-2 in the NAc is a convergent point that receives inputs from two signaling pathways, mTORC1 and GSK-3β, that in turn drives excessive alcohol-drinking behaviors.

The New Antiepileptic Drugs: Their Neuropharmacology and Clinical Indications

The administration of antiepileptic drugs (AEDs) is the first treatment of epilepsy, one of the most common neurological diseases. Therapeutic guidelines include newer AEDs as front-line drugs; monotherapy with new AEDs is delivered in Japan. While about 70% of patients obtain good seizure control by taking one to three AEDs, about 60% experience adverse effects and 33% have to change drugs. Compared to traditional AEDs, the prolonged administration of new AEDs elicits fewer adverse effects and fewer drug interactions and their teratogenicity may be lower. These characteristics increase drug compliance and allow combination therapy for drug-resistant epilepsy, although the antiepileptic effects of the new AEDs are not greater than of traditional AEDs. Comorbidities are not rare in epileptics; many adult patients present with stroke and brain tumors. In stroke patients requiring risk control and in chemotherapy-treated brain tumor patients, their fewer drug interactions render the new AEDs advantageous. Also, new AEDs offer favorable side benefits for concurrent diseases and conditions. Patients with stroke and traumatic brain injury often present with psychiatric/behavioral symptoms and cognitive impairment and some new AEDs alleviate such symptoms. This review presents an outline of the new AEDs used to treat adult patients based on the pharmacological activity of the drugs and discusses possible clinical indications from the perspective of underlying causative diseases and comorbidities.

(S)-Lacosamide Binding to Collapsin Response Mediator Protein 2 (CRMP2) Regulates CaV2.2 Activity by Subverting Its Phosphorylation by Cdk5

The neuronal circuit remodels during development as well as in human neuropathologies such as epilepsy. Neurite outgrowth is an obligatory step in these events. We recently reported that alterations in the phosphorylation state of an axon specification/guidance protein, the collapsin response mediator protein 2 (CRMP2), play a major role in the activity-dependent regulation of neurite outgrowth. We also identified (S)-LCM, an inactive stereoisomer of the clinically used antiepileptic drug (R)-LCM (Vimpat®), as a novel tool for preferentially targeting CRMP2-mediated neurite outgrowth. Here, we investigated the mechanism by which (S)-LCM affects CRMP2 phosphorylation by two key kinases, cyclin-dependent kinase 5 (Cdk5) and glycogen synthase kinase 3β (GSK-3β). (S)-LCM application to embryonic cortical neurons resulted in reduced levels of Cdk5- and GSK-3β-phosphorylated CRMP2. Mechanistically, (S)-LCM increased CRMP2 binding to both Cdk5- and GSK-3β without affecting binding of CRMP2 to its canonical partner tubulin. Saturation transfer difference nuclear magnetic resonance (STD NMR) and differential scanning fluorimetry (DSF) experiments demonstrated direct binding of (S)-LCM to CRMP2. Using an in vitro luminescent kinase assay, we observed that (S)-LCM specifically inhibited Cdk5-mediated phosphorylation of CRMP2. Cross-linking experiments and analytical ultracentrifugation showed no effect of (S)-LCM on the oligomerization state of CRMP2. The increased association between Cdk5-phosphorylated CRMP2 and CaV2.2 was reduced by (S)-LCM in vitro and in vivo. This reduction translated into a decrease of calcium influx via CaV2.2 in (S)-LCM-treated neurons compared to controls. (S)-LCM, to our knowledge, is the first molecule described to directly inhibit CRMP2 phosphorylation and may be useful for delineating CRMP2-facilitated functions.

The functionalized amino acid (S)-Lacosamide subverts CRMP2-mediated tubulin polymerization to prevent constitutive and activity-dependent increase in neurite outgrowth

Activity-dependent neurite outgrowth is a highly complex, regulated process with important implications for neuronal circuit remodeling in development as well as in seizure-induced sprouting in epilepsy. Recent work has linked outgrowth to collapsin response mediator protein 2 (CRMP2), an intracellular phosphoprotein originally identified as axon guidance and growth cone collapse protein. The neurite outgrowth promoting function of CRMP2 is regulated by its phosphorylation state. In this study, depolarization (potassium chloride)-driven activity increased the level of active CRMP2 by decreasing its phosphorylation by GSK3β via a reduction in priming by Cdk5. To determine the contribution of CRMP2 in activity-driven neurite outgrowth, we screened a limited set of compounds for their ability to reduce neurite outgrowth but not modify voltage-gated sodium channel (VGSC) biophysical properties. This led to the identification of (S)-lacosamide ((S)-LCM), a stereoisomer of the clinically used antiepileptic drug (R)-LCM (Vimpat®), as a novel tool for preferentially targeting CRMP2-mediated neurite outgrowth. Whereas (S)-LCM was ineffective in targeting VGSCs, the presumptive pharmacological targets of (R)-LCM, (S)-LCM was more efficient than (R)-LCM in subverting neurite outgrowth. Biomolecular interaction analyses revealed that (S)-LCM bound to wildtype CRMP2 with low micromolar affinity, similar to (R)-LCM. Through the use of this novel tool, the activity-dependent increase in neurite outgrowth observed following depolarization was characterized to be reliant on CRMP2 function. Knockdown of CRMP2 by siRNA in cortical neurons resulted in reduced CRMP2-dependent neurite outgrowth; incubation with (S)-LCM phenocopied this effect. Other CRMP2-mediated processes were unaffected. (S)-LCM subverted neurite outgrowth not by affecting the canonical CRMP2-tubulin association but rather by impairing the ability of CRMP2 to promote tubulin polymerization, events that are perfunctory for neurite outgrowth. Taken together, these results suggest that changes in the phosphorylation state of CRMP2 are a major contributing factor in activity-dependent regulation of neurite outgrowth.