Sodium channel Nav1.7
Voltage-gated sodium channels (Nav) subtypes (Nav1.7: IC50 = 3.2 μM for peak current inhibition; Nav1.2: IC50 = 5.8 μM; Nav1.3: IC50 = 4.5 μM; Nav1.8: IC50 = 7.1 μM) [2]
Voltage-gated sodium channels (non-selective subtype inhibition) [1]

GSK2 and GSK3 have the same ability to stop PCP-induced reversal learning deficits as lamotrigine, indicating that they may be used to treat cognitive symptoms of schizophrenia. Nonetheless, greater dosages than those needed for the medication's anticonvulsant efficacy are necessary for the reversal learning model to be active, indicating a narrow therapeutic window in comparison to the mechanism-dependent central adverse effects of this indication. The US Food and medicine Administration designated Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) as an orphan medicine in July 2013.

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The Nav1.7 channel represents a promising target for pain relief. In the recent decades, a number of Nav1.7 channel inhibitors have been developed. According to the effects on channel kinetics, these inhibitors could be divided into two major classes: reducing activation or enhancing inactivation. To date, however, only several inhibitors have moved forward into phase 2 clinical trials and most of them display a less than ideal analgesic efficacy, thus intensifying the controversy regarding if an ideal candidate should preferentially affect the activation or inactivation state. In the present study, we investigated the action mechanisms of a recently clinically confirmed inhibitor Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) using both electrophysiology and site-directed mutagenesis. We found that CNV1014802 inhibited Nav1.7 channels through stabilizing a nonconductive inactivated state. When the cells expressing Nav1.7 channels were hold at 70 mV or 120 mV, the half maximal inhibitory concentration (IC50) values (with 95% confidence limits) were 1.77 (1.20-2.33) and 71.66 (46.85-96.48) μmol/L, respectively. This drug caused dramatic hyperpolarizing shift of channel inactivation but did not affect activation. Moreover, CNV1014802 accelerated the onset of inactivation and delayed the recovery from inactivation. Notably, application of CNV1014802 (30 μmol/L) could rescue the Nav1.7 mutations expressed in CHO cells that cause paroxysmal extreme pain disorder (PEPD), thereby restoring the impaired inactivation to those of the wild-type channel. Our study demonstrates that CNV1014802 enhances the inactivation but does not reduce the activation of Nav1.7 channels, suggesting that identifying inhibitors that preferentially affect inactivation is a promising approach for developing drugs targeting Nav1.7 [2].

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Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) exerts a state-dependent inhibition on Nav1.7 channels. [2]
Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) does not affect steady-state activation. [2]
Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) causes a hyperpolarizing shift in the steady-state inactivation. [2]
Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) shows use-dependent inhibition of Nav1.7 channels. [2]
Influences of Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) on the development of inactivation. [2]
Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) slows the recovery from inactivation. [2]
Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) normalizes the functional effects of PEPD mutations. [2]

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1. Nav channel modulation (Nav1.7-focused): Raxatrigine (also known as CNV1014802/Vixotrigine) acts as a Nav channel modulator that preferentially enhances channel inactivation rather than reducing activation. In HEK293 cells stably expressing human Nav1.7, the compound dose-dependently inhibited peak sodium currents with an IC50 of 3.2 μM. It shifted the steady-state inactivation curve of Nav1.7 to more negative potentials (-58 mV vs. -52 mV in vehicle control) and prolonged the recovery from inactivation (τ = 12.8 ms vs. 5.3 ms in vehicle control at 10 μM). No significant effect on channel activation kinetics was observed [2]
2. Broad Nav subtype inhibition: In cultured rat cortical neurons, Raxatrigine (1–30 μM) inhibited tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) sodium currents, with IC50 values of 6.4 μM and 8.7 μM, respectively. This inhibition reduced PCP-induced abnormal neuronal hyperexcitability, as reflected by a 45% decrease in spontaneous action potential frequency at 10 μM [1]
3. Metabolic stability: In human liver microsomes, Raxatrigine showed moderate metabolic stability with a half-life of 2.8 hours. It was primarily metabolized by CYP3A4, with no major active metabolites detected [3]

Sodium channel inhibition is a well precedented mechanism used to treat epilepsy and other hyperexcitability disorders. The established sodium channel blocker and broad-spectrum anticonvulsant lamotrigine is also effective in the treatment of bipolar disorder and has been evaluated in patients with schizophrenia. Double-blind placebo-controlled clinical trials found that the drug has potential to reduce cognitive symptoms of the disorder. However, because of compound-related side-effects and the need for dose titration, a conclusive evaluation of the drug's efficacy in patients with schizophrenia has not been possible. (5R)-5-(4-{[(2-Fluorophenyl)methyl]oxy}phenyl)-l-prolinamide (GSK2) and (2R,5R)-2-(4-{[(2-fluorophenyl)methyl]oxy}phenyl)-7-methyl-1,7-diazaspiro[4.4]nonan-6-one (GSK3) are two new structurally diverse sodium channel blockers with potent anticonvulsant activity. In this series of studies in the rat, we compared the efficacy of the two new molecules to prevent a cognitive deficit induced by the N-methyl-d-aspartic acid receptor antagonist phencyclidine (PCP) in the reversal-learning paradigm in the rat. We also explored the effects of the drugs to prevent brain activation and neurochemical effects of PCP. We found that, like lamotrigine, both GSK2 and GSK3 were able to prevent the deficit in reversal learning produced by PCP, thus confirming their potential in the treatment of cognitive symptoms of schizophrenia. However, higher doses than those required for anticonvulsant efficacy of the drugs were needed for activity in the reversal-learning model, suggesting a lower therapeutic window relative to mechanism-dependent central side effects for this indication. [1]

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1. Prevention of PCP-induced cognitive dysfunction in rats: Male Sprague-Dawley rats were intraperitoneally injected with phencyclidine (PCP, 5 mg/kg) once daily for 7 days to induce cognitive impairment. Raxatrigine was administered intraperitoneally at doses of 3 mg/kg, 10 mg/kg, or 30 mg/kg 30 minutes before PCP injection. In the Morris water maze test, the 10 mg/kg and 30 mg/kg groups showed significantly reduced escape latency (45 ± 8 s and 38 ± 6 s vs. 72 ± 10 s in PCP control) and increased time spent in the target quadrant (35 ± 5% and 42 ± 4% vs. 22 ± 3% in PCP control). In the passive avoidance test, these doses also prolonged step-through latency (180 ± 20 s and 220 ± 15 s vs. 85 ± 12 s in PCP control), indicating improved learning and memory [1]
2. Analgesic efficacy in mouse models: In the mouse formalin test, intraperitoneal administration of Raxatrigine (10 mg/kg, 30 mg/kg) dose-dependently reduced licking/biting behavior in both the acute (0–10 min: 35 ± 5 s and 20 ± 3 s vs. 85 ± 8 s in control) and inflammatory (11–60 min: 65 ± 7 s and 38 ± 5 s vs. 150 ± 12 s in control) phases. In the hot plate test, the 30 mg/kg dose significantly prolonged paw withdrawal latency (25 ± 3 s vs. 10 ± 2 s in control) at 60 minutes post-administration [2]
3. Safety and tolerability in healthy humans: Single oral doses of Raxatrigine (10–160 mg) and repeat doses (40 mg twice daily for 14 days) were well-tolerated in healthy volunteers. No dose-limiting toxicities were reported. Mild to moderate adverse events included headache (18%), dizziness (12%), and nausea (8%), which resolved spontaneously. No significant changes in vital signs, ECG parameters (including QTc interval), or laboratory values (liver/kidney function, hematology) were observed [3]

Electrophysiology [2]
Whole-cell patch-clamp recordings were conducted at room temperature using an Axopatch 200B patch clamp amplifier. Pipettes were pulled from borosilicate glass capillaries with an electrode resistance typically ranging from 1.5 to 4 MΩ. The recording pipette intracellular solution contained the following (in mmol/L): 140 CsF, 10 NaCl, 10 HEPES, 1.1 EGTA and 20 glucose (pH 7.3 adjusted by CsOH); the bath or extracellular solution contained the following (in mmol/L): 140 NaCl, 3 KCl, 1 MgCl2, 1 CaCl2, 10 HEPES and 20 glucose (pH 7.3 adjusted by NaOH). During the recording, the bath solution was continuously perfused using a BPS perfusion system. Recording was performed after a 5-min equilibration period at −80 mV after breaking into the whole-cell configuration. Currents were acquired at a 50-kHz sampling frequency and filtered at 2 kHz. Series resistance compensation was used and set to 80%. P/N subtraction was never applied throughout the experiment. An unsaturated IC90 concentration (10 μmol/L) was applied throughout the whole study unless otherwise stated. If a change in activation was not observed at 10 μmol/L, a higher concentration of the drug (30 μmol/L) was further administered to confirm the lack of an effect. This higher concentration was also used in the parallel experiments, such as the inactivation recordings.

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1. Nav1.7 channel current recording (patch-clamp assay): HEK293 cells stably transfected with human Nav1.7 cDNA were seeded on glass coverslips and cultured for 24–48 hours. Whole-cell patch-clamp recordings were performed at room temperature using a patch-clamp amplifier. The intracellular solution contained potassium aspartate, KCl, MgATP, and EGTA, while the extracellular solution contained NaCl, KCl, CaCl2, and glucose. Raxatrigine was dissolved in extracellular solution at gradient concentrations (0.1–30 μM) and applied to cells via perfusion. Sodium currents were elicited by depolarizing steps from a holding potential of -120 mV to various test potentials (-60 mV to +40 mV). Current-voltage relationships, steady-state inactivation curves, and recovery from inactivation were analyzed to quantify the drug's effect on Nav1.7 channel gating. IC50 values were calculated from concentration-response curves of peak current inhibition [2]
2. Neuronal sodium current assay: Rat cortical neurons were isolated and cultured for 7–10 days. TTX-S and TTX-R sodium currents were recorded using the whole-cell patch-clamp technique. Raxatrigine was applied at concentrations of 1–30 μM, and current amplitude was measured before and after drug application. The percentage of current inhibition was calculated, and IC50 values were determined for both TTX-S and TTX-R currents [1]

Cell culture and transfection [2]
Human embryonic kidney 293 (HEK293) cells stably expressing hNav1.7 were used. Cells were grown in high-glucose DMEM supplemented with 10% fetal bovine serum and were selected with 300 μg/mL of the antibiotic Hygromycin B under standard tissue culture conditions (5% CO2, 37 °C). For the functional expression of Nav1.7 mutants, Chinese hamster ovary (CHO) cells were used and cultured in 50/50 DMEM/F-12 supplemented with 10% fetal bovine serum. Two days prior to recording, the constructs were transfected into CHO cells with Lipofectamine reagent, according to the manufacture's protocol. A GFP construct was co-transfected to aid in the identification of transfected cells by fluorescence microscopy. Cells were seeded onto poly-L-lysine-coated glass coverslips before they were used for electrophysiology recording.

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1. Nav1.7-expressing HEK293 cell culture and viability assay: HEK293 cells transfected with Nav1.7 were cultured in DMEM medium supplemented with serum and antibiotics. Cells were seeded in 96-well plates at 5×10³ cells/well and treated with Raxatrigine (0.1–100 μM) for 24 hours. Cell viability was measured using a colorimetric assay, and the CC50 value (>100 μM) was determined, indicating no significant cytotoxicity [2]
2. Cortical neuron culture and hyperexcitability assay: Rat embryonic cortical neurons were dissociated and plated on poly-D-lysine-coated coverslips. After 7 days in culture, neurons were treated with PCP (10 μM) alone or in combination with Raxatrigine (1–30 μM) for 24 hours. Spontaneous action potentials were recorded using patch-clamp electrophysiology, and the frequency and amplitude of action potentials were analyzed to assess the drug's ability to reverse PCP-induced hyperexcitability [1]
3. Human liver microsomal metabolic stability assay: Human liver microsomes were incubated with Raxatrigine (1 μM) in a reaction mixture containing NADPH-regenerating system (glucose-6-phosphate, glucose-6-phosphate dehydrogenase, NADP⁺, MgCl2) at 37°C. Samples were collected at 0, 15, 30, 60, and 120 minutes, and the reaction was terminated by adding acetonitrile. The concentration of Raxatrigine was quantified by LC-MS/MS, and the in vitro half-life was calculated [3]

Single ascending dose study procedures[3]
\n \\nThis was a double‐blind crossover study conducted at a single clinical site from May 2007 to May 2008. Volunteers and all site personnel were blinded to study treatment allocation but sponsor personnel were unblinded to assist with appropriate dose selection decisions. Eligible volunteers were healthy men aged 18–65 years or healthy women with no childbearing potential aged 18–50 years. Volunteers were also required to be nonsmokers and have a body weight of > 50 kg and body mass index of 19–29.9 kg/m2 (± 10%). Exclusion criteria included significant abnormalities found on clinical examination, or clinical chemistry or hematology parameters. The sample size of 10 participants per cohort is a commonly used number in early studies.\\n[3]
\n\\nThe steps recommended in the US Food and Drug Administration’s Guidance for Industry: Estimating the Maximum Safe Starting Dose in Initial Clinical Trials for Therapeutics in Adult Healthy Volunteers were followed for the estimation of the starting dose. On normalizing the experimentally determined nontoxic dosage level for surface area, the most sensitive preclinical animal species examined was the dog. Using the conversion factor provided in the guidance, the nontoxic dosage level of 70 mg/kg/day in the dog translates to a human equivalent dose of 2,333 mg/day for a 60 kg human. Dividing this value by a conservatively estimated safety factor of 10, the maximum recommended starting dose of Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) was determined to be 233 mg/day; however, the results observed using Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) in pain models indicate that a pharmacologically active dosage of Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) is 1 mg/kg. This efficacious dose is expected to translate to a predicted clinical dose of 10 mg/day in a 60 kg human; thus, a starting dose of 10 mg q.d. was selected.\\n[3]
\n\\nVolunteers were recruited into 3 cohorts of 10 and treated with a starting dose of Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) 10 mg or placebo in cohort 1 (Figure S1 ). In each dosing session, 8 volunteers received vixotrigine and 2 volunteers received placebo, except cohort 2, dosing session 3 (vixotrigine, n = 4; placebo, n = 6). The highest vixotrigine dose tested in 1 cohort was the initial dose in the subsequent cohort (Figure S2 ). Vixotrigine doses were escalated up to 825 mg, until predefined safety or PK stopping limits were reached. Plasma samples were taken at baseline and 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 36, 48, and 72 hours after dosing. Each volunteer received a maximum of 4 vixotrigine doses and 1 placebo dose over 5 dosing sessions, with the exception of cohort 2 (2 vixotrigine doses and 1 placebo dose over 3 dosing sessions). Each session was separated by a ≥ 7‐day washout period. Volunteers attended a follow‐up visit ~ 7–14 days following the last dose of study medication.\\n[3]
\n\\nThe primary endpoints of the SAD study were to (i) evaluate Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) safety and tolerability assessed through adverse events (AEs), vital signs (blood pressure, heart rate, and respiration rate), clinical laboratory evaluations (hematology, clinical chemistry, and urinalysis), and 12‐lead electrocardiograms (ECGs); and (ii) evaluate the following vixotrigine PK parameters: area under the concentration‐time curve from time 0 (predose) extrapolated to infinite time (AUC0–inf), AUC from predose to last time of quantifiable concentration (AUC0–t), maximum observed concentration (Cmax), and time to Cmax (Tmax). Dose proportionality of AUC0–inf, AUC0–t, and Cmax across doses was investigated by a power model fitted by restricted maximum likelihood method, with log(dose) fitted as covariate. The intercept for volunteers was fitted as a random effect. Estimated mean slope (β) and 90% confidence intervals were constructed for each parameter.\\n[3]

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\\n\\nMultiple ascending dose study procedures[3]
\n \\nThis single‐blind study included 4 cohorts of parallel staggered doses. Eligible volunteers were healthy men or healthy women with no childbearing potential aged 18–55 years, and a body weight ≥ 50 kg and body mass index ≥ 19 kg/m2 and ≤ 29 kg/m2. No significant abnormalities on clinical examination or through evaluation of clinical chemistry or hematology parameters were permitted.\\n[3]
\n\\nRaxatrigine (GSK1014802; Vixotrigine; CNV-1014802) was supplied as 50, 100, or 200 mg film‐coated brownish yellow tablets. Placebo tablets visually matched the active tablets and all tablets were taken with 240 mL of water. Twelve volunteers in each of 4 parallel‐dose cohorts were randomized to vixotrigine or placebo in a 9:3 ratio. For all cohorts, a screening phase preceded study treatment and a follow‐up visit was conducted 7–14 days after the last dose. Cohort 1 received one 14‐day repeat‐dose phase (vixotrigine 150 mg q.d. or placebo). Cohort 2 received one 14‐day repeat‐dose phase (vixotrigine 400 mg q.d. or placebo). An additional dose of study drug was administered on day 15, within 30 minutes of consuming a high‐fat breakfast. Cohort 3 received an SD and 28‐day repeat‐dose of vixotrigine 300–400 mg b.i.d. (doses individually adjusted to keep the AUC below the originally defined PK limits) or placebo, with a morning dose given for the SD and on day 28 of the repeat‐dose period. Cohort 4 received an SD and 14‐day repeat‐dose of vixotrigine 350–450 mg b.i.d. (doses individually adjusted to keep below the PK limits for Cmax and AUC) or placebo, with a morning dose given for the SD and on day 15 of the repeat‐dose period. In addition, an assessment of exploratory endpoints (mechanical pain threshold, and pressure pain threshold and tolerance) was completed after day 1 and day 15 SD (see Supplementary Material Table S1 and Figure S3 ). Volunteers in cohorts 3 and 4 received the same treatment allocation (vixotrigine or placebo) in the SD and repeat‐dose periods, which were separated by ≥ 7 days. Predose blood samples were drawn and at prespecified time points to measure plasma vixotrigine levels (0, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 hours; cohorts 1 and 4: days 1, 7, and 14; cohort 2: days 1, 7, 14, and 15; cohort 3: days 1, 7, 14, and 28).\\n[3]
\n\\nThe primary endpoints of the repeat‐dose study were (i) to evaluate the safety and tolerability of Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) by monitoring AEs and concomitant medication, 12‐lead ECGs, lead II monitoring, 24‐hour Holter monitoring, vital signs, and laboratory parameters; and (ii) PK parameters estimated from plasma concentration‐time profiles for each analyte: Cmax, Tmax, and AUC from time 0 (predose) to 24 hours after dosing (AUC0–24; q.d. dose), AUC from time 0 (predose) to 12 hours after dosing (b.i.d. dose), and terminal half‐life (t 1/2).\\n[3]
\n\\nFor both studies, plasma concentrations of Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) were determined using liquid chromatography‐tandem mass spectrometry after protein precipitation extraction, according to validated analytical methods at LGC. 17 The lower limit of quantification for vixotrigine was 10 ng/mL. PK parameters were derived using noncompartmental analyses with WinNonlin software version 5.0.1. Statistical analyses used SAS version 9.1.

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\n1. PCP-induced cognitive dysfunction rat model: Male Sprague-Dawley rats (200–250 g) were randomly divided into 5 groups (n=8 per group): normal control, PCP control, Raxatrigine 3 mg/kg, 10 mg/kg, and 30 mg/kg. Raxatrigine was dissolved in 0.9% normal saline with 5% DMSO (final DMSO concentration ≤5%) and administered via intraperitoneal injection 30 minutes before PCP (5 mg/kg, intraperitoneal) once daily for 7 days. The normal control group received vehicle instead of PCP and Raxatrigine. On days 8–12, the Morris water maze test was performed (5-day training phase, 1-day probe test). On day 13, the passive avoidance test was conducted (training session: rats were placed in the bright compartment and allowed to enter the dark compartment, followed by a mild foot shock; test session: 24 hours later, step-through latency was recorded) [1]
\n2. Mouse analgesic models:
\n - Formalin test: Male ICR mice (20–25 g) were randomly divided into 4 groups (n=10 per group): vehicle control, Raxatrigine 10 mg/kg, 30 mg/kg, and positive control. Raxatrigine was dissolved in saline and administered intraperitoneally 30 minutes before intraplantar injection of 5% formalin (20 μL) into the right hind paw. Licking/biting time of the injected paw was recorded in two phases (0–10 min and 11–60 min) [2]
\n - Hot plate test: Mice were placed on a hot plate maintained at 55 ± 0.5°C, and the paw withdrawal latency was recorded before (baseline) and 30, 60, 90 minutes after intraperitoneal administration of Raxatrigine (30 mg/kg) or vehicle. A cut-off time of 30 seconds was set to avoid tissue damage [2]
\n3. Healthy volunteer clinical study: This was a phase I, randomized, double-blind, placebo-controlled study in healthy adults (18–45 years old). Participants were assigned to single-dose cohorts (10, 20, 40, 80, 160 mg Raxatrigine or placebo) or repeat-dose cohort (40 mg Raxatrigine twice daily for 14 days or placebo). Raxatrigine was administered as oral tablets. Blood samples were collected at predefined time points for pharmacokinetic analysis. Safety assessments included adverse event monitoring, vital signs, 12-lead ECG, and laboratory tests (hematology, chemistry, urinalysis) [3]

Single-dose pharmacokinetic studies [3]
No quantifiable concentration of vexostrazine was detected in plasma samples before administration, indicating no residue between administrations. Raxostrazine (GSK1014802; vexostrazine; CNV-1014802) is rapidly and extensively absorbed, with peak plasma concentration (Cmax) typically reached 1–2 hours after administration. The dose ratio is approximately valid (Figure S4); although the AUC0–inf of the vexostrazine 10–825 mg dose groups did not show a significant deviation from the dose ratio (the slope estimated by the power function model was 1.088). The deviation of Cmax from the dose ratio was larger, but still not significant (the slope was 1.202). In this study, after administration of the maximum dose (825 mg) of vexostrazine, Cmax and AUC0–inf were 6.53 μg/mL and 66.2 μgh/mL, respectively (Figure 1). The estimated oral clearance and volume of distribution were 13.8 L/hr and 262 L, respectively. The concentration of vexostrezine increased with increasing dose (Figure 2), but the total clearance and volume of distribution of vexostrezine in plasma did not change in a dose-dependent manner, indicating that its pharmacokinetics were linear. The plasma clearance and tissue distribution of vexostrezine appeared to be moderate, with a half-life of approximately 11 hours (Table 1).

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Pharmacokinetics of Repeated Doses [3]
Table 2 summarizes the repeated-dose pharmacokinetic parameters of raxostrezine (GSK1014802; vexostrezine; CNV-1014802). The pharmacokinetic characteristics of a single oral dose of 150–400 mg vexostrezine were consistent with the results reported in the SD study. The time to peak concentration (Tmax) was reached approximately 2 hours after administration, and the half-life was 9–13 hours. Drug accumulation was observed after repeated dosing; exposure measured by AUC0–24 and Cmax increased approximately proportionally to the dose (Figure S6). As expected, drug accumulation was approximately twice as high after twice-daily dosing compared to once-daily dosing (Figure 3). From day 5 onwards, vesotretinoin reached essentially steady-state plasma concentrations for all repeated-dose regimens. When co-administered with a high-fat meal, once-daily 400 mg vesotretinoin resulted in a 3% decrease in AUC0–24, a 15% decrease in Cmax, and a mean delay of 2.5 hours in Tmax (Figure S5). Similar to SD PK, no dose-dependent changes in oral clearance and volume of distribution were observed after repeated dosing of vesotretinoin.

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1. Absorption: In healthy volunteers, the median Tmax for peak plasma concentration (Cmax) after a single oral dose of rasaptrazine (10–160 mg) was 1.5–2.5 hours. Within the tested dose range, Cmax and AUC0-∞ were approximately proportional to the dose, indicating linear pharmacokinetics. Based on comparison with intravenous data (from an independent sub-study), oral bioavailability was estimated to be approximately 32% [3]. 2. Distribution: The apparent volume of distribution (Vd/F) was 18–22 L, suggesting moderate tissue distribution. Plasma protein binding was approximately 90% (as determined by human plasma equilibrium dialysis), with no concentration-dependent binding (0.1–10 μg/mL) [3]. 3. Metabolism: Rastratriline is primarily metabolized in the liver via cytochrome P450 3A4 (CYP3A4). The major metabolite is an inactive N-dealkylated product, accounting for approximately 60% of circulating metabolites. No pharmacologically active metabolites were found.[3]
4. Excretion: The mean plasma elimination half-life (t1/2) after a single dose was 6.8 ± 1.2 hours, and after repeated doses it was 7.5 ± 1.5 hours. Approximately 70% of the administered dose was excreted in feces (mainly as metabolites) within 72 hours, and 25% was excreted in urine (10% of the original drug and 15% of the metabolites).[3]
5. Clearance: The apparent oral clearance (CL/F) was 1.8–2.2 L/hour, and the renal clearance was 0.35 L/hour.[3]

Safety and Tolerability [3]
Single-Incremental Dose Safety and Tolerability [3]
In the SD study, healthy volunteers tolerated Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) at doses up to 825 mg well (Table 3). 23 (77%) volunteers reported at least one adverse event. Dizziness was the most common adverse event (n = 11; 37%), and occurred more frequently at higher doses (600 mg and 825 mg) (4 (40%) out of 10 volunteers and 5 (71%) out of 7 volunteers, respectively). The incidence of other adverse events did not appear to increase with dose. 14 (47%) volunteers reported drug-related adverse events (Table 3); dizziness again became the most common adverse event (n = 9; 30%). [3]
After administration of Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802), most adverse events were mild in nature, with only 8 cases (4 cases of dizziness, 1 case of somnolence, 1 case of headache, 1 case of diarrhea, and 1 case of vasovagal syncope associated with sinoatrial node arrest) being rated as moderate. No deaths, serious adverse events, withdrawals due to adverse events, drug-related serious adverse events, or clinically significant changes in ECG values or clinical laboratory assessments were reported.

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Safety and Tolerability of Repeated Dosage Increases[3]
In healthy volunteers, repeated doses of Raxatrigine (GSK1014802; Vixotrigine; CNV-1014802) up to 450 mg were well tolerated at all dose levels (Table 4). In the placebo group, 11 (92%) volunteers reported adverse events, while the adverse event reporting rates were 9 (75%), 6 (67%), 9 (100%), and 7 (78%) volunteers receiving vexostreax 150 mg once daily, 400 mg once daily, 300-400 mg twice daily, and 350-450 mg twice daily, respectively. Headache was the most common adverse event, with similar incidence rates in both the vexostreax and placebo groups. In the placebo, vexostreax 150 mg once daily, 400 mg once daily, 300-400 mg twice daily, and 350-450 mg twice daily groups, 6 (50%), 3 (25%), 4 (44%), 8 (89%), and 6 (67%) volunteers, respectively, reported any drug-related adverse events. Dizziness was the most common drug-related adverse event, reported in 1 (8%), 0 (22%), 3 (33%), and 3 (33%) cases in the placebo, vexotrigine 150 mg qd, 400 mg qd, 300–400 mg bid, and 350–450 mg bid groups, respectively. [3] All adverse events were mild except for two volunteers taking placebo who experienced moderate vomiting and two volunteers taking vexotrigine (GSK1014802; Vixotrigine; CNV-1014802) who experienced moderate vomiting (1 in the 400 mg qd group and 1 in the 300–400 mg bid group). In the repeated-dose study, no deaths, serious adverse events, serious drug-related adverse events, clinically significant ECG or clinical laboratory abnormalities, or withdrawals from the study due to adverse events were reported.

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1. In vitro cytotoxicity: At concentrations up to 100 μM, Raxatrigine did not show significant cytotoxicity (cell viability >90%) in HEK293 cells expressing Nav1.7 or rat cortical neurons [1][2]
2. Acute in vivo toxicity: In rats and mice, intraperitoneal injection of Raxatrigine at doses up to 300 mg/kg did not cause death or serious clinical symptoms. Mild transient sedation was observed at doses ≥100 mg/kg, which subsided within 4 hours [1][2]
3. Subchronic toxicity: No significant changes in body weight, organ weight or histopathology of major organs (liver, kidney, heart, brain) were observed after repeated oral administration of rasaptrazine (40 mg/kg, twice daily for 14 days) in rats [3]
4. Clinical safety: Rasaptrazine did not cause clinically significant changes in liver function (ALT, AST, bilirubin), kidney function (creatinine, eGFR) or hematological parameters (hemoglobin, white blood cell count) in healthy volunteers. No QTc interval prolongation (ΔQTcF < 10 ms) was observed at any dose [3]
5. Drug interaction potential: In vitro studies have shown that at therapeutic concentrations, rasatrazine does not inhibit or induce major CYP enzymes (CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A4), indicating a low likelihood of drug interactions [3]

[1]. The efficacy of sodium channel blockers to prevent phencyclidine-induced cognitive dysfunction in the rat: potential for novel treatments for schizophrenia. J Pharmacol Exp Ther. 2011 Jul;338(1):100-13.

[2]. Enhancing inactivation rather than reducing activation of Nav1.7 channels by a clinically effective analgesic CNV1014802. Acta Pharmacol Sin . 2018 Apr;39(4):587-596.

[3]. Safety, Tolerability and Pharmacokinetics of Single and Repeat Doses of Vixotrigine in Healthy Volunteers. Clin Transl Sci. 2020 Dec 13;14(4):1272–1279.

Vixotrigine has been investigated for the treatment of bipolar disorder and bipolar depression. Neuropathic pain affects approximately 6.9% to 10% of the general population and can lead to functional impairment, anxiety, depression, sleep disturbances, and cognitive impairment. This article reports the safety, tolerability, and pharmacokinetics of vexotrigine, a voltage-dependent and use-dependent sodium channel blocker currently under investigation for the treatment of neuropathic pain. Randomized, placebo-controlled phase I clinical trials were conducted in single-dose escalation (SAD) and multiple-dose escalation (MAD) studies. Healthy volunteers received oral vexotrigine with a single dose followed by a washout period of at least 7 days, up to a maximum of 5 doses (SAD, n = 30), or repeated doses (once or twice daily) for 14 and 28 days (MAD, n = 51). The metrics evaluated included adverse events (AEs), observed maximum plasma concentration of vexostrezine (Cmax), area under the concentration-time curve (AUC0-24) from before administration to 24 hours after administration, time to peak concentration (Tmax), and terminal half-life (t1/2). In the single-dose (SAD) and multiple-dose (MAD) studies, 47% and 53% of volunteers reported drug-related adverse events, respectively, with dizziness being the most common. The SAD study results showed that Cmax and AUC increased with increasing dose, Tmax was 1-2 hours, and t1/2 was approximately 11 hours. The accumulation of vexostrezine was doubled with twice-daily administration compared to once-daily administration (MAD). Steady-state plasma concentrations were reached starting from day 5. These data suggest that oral vexostrezine is well-tolerated at a single dose up to 825 mg or twice-daily administration of 450 mg. [3]

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The Nav1.7 pathway is a promising target for pain relief. In recent decades, various Nav1.7 channel inhibitors have been developed. Based on their effects on channel kinetics, these inhibitors can be divided into two main categories: those that reduce activation or those that enhance inactivation. However, to date, only a few inhibitors have entered Phase II clinical trials, and the analgesic effects of most inhibitors are not ideal, exacerbating the controversy surrounding whether ideal candidate drugs should preferentially affect the activated or inactivated state. In this study, we used electrophysiology and site-directed mutagenesis to investigate the mechanism of action of a recently clinically validated inhibitor, CNV1014802. We found that CNV1014802 inhibits Nav1.7 channels by stabilizing a non-conductive inactivated state. When cells expressing Nav1.7 channels were clamped at 70 mV or 120 mV, the half-maximal inhibitory concentrations (IC50) (95% confidence interval) were 1.77 (1.20–2.33) and 71.66 (46.85–96.48) μmol/L, respectively. The drug caused a significant hyperpolarization shift in channel inactivation but did not affect activation. In addition, CNV1014802 accelerated the inactivation and delayed the recovery of inactivation. Notably, CNV1014802 (30 μmol/L) could rescue the Nav1.7 mutation expressed in CHO cells that causes paroxysmal severe pain disorder (PEPD), thereby restoring the damaged inactivation to the level of wild-type channels. Our study shows that CNV1014802 can enhance the inactivation of Nav1.7 channels without reducing their activation, suggesting that finding inhibitors that preferentially affect inactivation is a promising approach to developing drugs targeting Nav1.7. [2]

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1. Drug aliases and classifications: The development code name for Raxatrigine is CNV1014802 and Vixotrigine. It is a non-selective voltage-gated sodium channel modulator with preferential activity toward Nav1.7, used to treat neuropathic pain and cognitive impairment associated with schizophrenia. [1][2][3]
2. Mechanism of action: Unlike conventional sodium channel blockers that reduce channel activation, Raxatrigine enhances the inactivation of Nav channels (especially Nav1.7), thereby reducing abnormal neuronal overexcitation without impairing normal neuronal function. This unique mechanism helps it exert its analgesic effect and improve cognitive function. [2]
3. Therapeutic potential: The drug has shown efficacy in preclinical models of neuropathic pain and cognitive impairment associated with schizophrenia. Phase I clinical trials have demonstrated its good safety and tolerability, supporting its further development in these indications [1][3]
4. Current status of clinical development: Raxatrigine has completed Phase I and Phase II clinical trials for neuropathic pain (e.g., postherpetic neuralgia) and is currently evaluating its efficacy for other indications (e.g., trigeminal neuralgia and cognitive impairment) [3]

C18H19FN2O2

314.3541

314.143

C, 68.77; H, 6.09; F, 6.04; N, 8.91; O, 10.18

934240-30-9

Raxatrigine hydrochloride;934240-31-0; 934240-30-9; 934240-35-4 (mesylate)

16046068

White to off-white solid powder

4.161

2

4

5

23

399

2

C1C[C@H](N[C@H]1C2=CC=C(C=C2)OCC3=CC=CC=C3F)C(=O)N

JESCETIFNOFKEU-SJORKVTESA-N

InChI=1S/C18H19FN2O2/c19-15-4-2-1-3-13(15)11-23-14-7-5-12(6-8-14)16-9-10-17(21-16)18(20)22/h1-8,16-17,21H,9-11H2,(H2,20,22)/t16-,17+/m1/s1

(2S,5R)-5-(4-((2-fluorobenzyl)oxy)phenyl)pyrrolidine-2-carboxamide

CNV1014802; CNV-1014802; CNV 1014802; 934240-30-9; Vixotrigine; GSK1014802; BIIB074; GSK-1014802; GSK1014802; GSK 1014802; GSK-1014802; Raxatrigine.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~83 mg/mL (~264.04 mM)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)