Mechanisms of action of CHF3381 in the forebrain

Ion channel blockers for the treatment of neuropathic pain

Neuropathic pain, a severe chronic pain condition characterized by a complex pathophysiology, is a largely unmet medical need. Ion channels, which underlie cell excitability, are heavily implicated in the biological mechanisms that generate and sustain neuropathic pain. This review highlights the biological evidence supporting the involvement of voltage-, proton- and ligand-gated ion channels in the neuropathic pain setting. Ion channel modulators at different research or development stages are reviewed and referenced. Ion channel modulation is one of the main avenues to achieve novel, improved neuropathic pain treatments. Voltage-gated sodium and calcium channel and glutamate receptor modulators are likely to produce new, improved agents in the future. Rationally targeting subtypes of known ion channels, tackling recently discovered ion channel targets or combining drugs with different mechanism of action will be primary sources of new drugs in the longer term.

Synthesis and anticonvulsant activity of a class of 2-amino 3-hydroxypropanamide and 2-aminoacetamide derivatives

Several studies have demonstrated that N-substituted amino acid derivatives exhibit weak anticonvulsant activities in vivo. In the present study, a series of amides of aminoacids structurally related to aminoacetamide have been synthesised and investigated for anticonvulsant activity. Among the molecules investigated, those containing a bicyclic (tetralinyl, indanyl) group linked to the aminoacetamide chain (40, 47 and 59) were among the most active as anticonvulsants (ED50 > 10, <100 mg/kg after oral administration) against tonic seizures in the mouse maximal electroshock, bicuculline and picrotoxin tests at doses devoid of neurotoxic activity. Altogether, these results suggest the described compounds as a class of orally available anticonvulsants. The ability of these compounds to partially block veratridine-induced aspartate efflux from rat cortical synaptosomes suggests that their anticonvulsant activity may be only partly the consequence of an interaction with neuronal voltage-dependent sodium channels. Some of the most potent compounds appear worthy of a further investigation aimed at assessing their anticonvulsant activity in other models and at elucidating the underlying mechanism of action.

Anticonvulsant and Behavioural Effects of the Denatured Venom of the Social Wasp Polybia occidentalis (Polistinae, Vespidae)

Several investigations demonstrate that neurotoxins isolated from venoms of spiders and wasps may exert specific and selective activity on structures of the mammalian CNS. In the present work we examine the neurological effects of the low molecular weight compounds of the denatured venom of the neotropical social wasp Polybia occidentalis in freely moving rats. Central administration of denatured venom decreased the duration of exploratory, elevation and grooming behaviours on the open field. Moreover, denatured venom inhibited convulsing action of bicuculline (ED50 57 microg/microl), picrotoxin (ED50 75 microg/microl) and kainic acid (ED50 44 microg/microl), although it was ineffective against pentylenetetrazole-induced seizures. Despite of its inhibitory activity, toxic effects on motor performance examined in the rotarod test were not found, not even in extremely high doses. Also, denatured venom moderately reduced the spontaneous locomotor activity at anticonvulsant doses. These findings may indicate that the denatured venom has anticonvulsant activity with scarce propensity to cause neurological side-effects. Further studies are necessary to isolate the active compound and establish its mechanism of action.

Steady-state pharmacokinetics and pharmacodynamics of CHF3381, a novel antineuropathic pain agent, in healthy subjects

AIMS

To evaluate the safety, tolerability, pharmacokinetic and pharmacodynamic profiles of CHF3381, a dual NMDA and MAO-A inhibitor, after multiple oral doses in healthy subjects.

METHODS

Forty-eight young males received CHF3381 at doses of 100 mg twice daily, 200 mg twice daily, 400 mg twice daily or placebo for 2 weeks according to a double-blind, randomized, parallel group design. Plasma and urine concentrations of the parent drug and of two major metabolites (CHF3567 and 2-aminoindane) were measured over time. MAO-A activity in plasma was estimated by measuring plasma concentrations of 3,4-dihydroxyphenylglycol. Sustained attention, memory and sedation were assessed throughout the study with standard psychometric tests.

RESULTS

Most of the adverse events were mild in intensity, with dose regimens of 100 mg twice daily and 200 mg twice daily being indistinguishable from placebo. After 400 mg twice daily, the most frequent adverse events were mild dizziness, asthenia and insomnia. At steady-state, 400 mg twice daily slightly increased supine heart rate (+ 9 +/- 2 beats min(-1)) and diastolic blood pressure (+6 +/- 2 mmHg) compared with placebo. There were no dose-dependent or consistent effects of CHF3381 on attention, motor co-ordination or memory, but 400 mg twice daily significantly decreased alertness compared with placebo. Plasma concentrations of CHF3381 peaked at around 3 h and were dose-proportional. The elimination half-life of CHF3381 was estimated to be 4-6 h. At steady-state, significant CHF3381 plasma concentrations were detected at predose with a modest accumulation (1.3-1.5 times), showing that the drug given twice daily is active over the entire 24 h period. Plasma concentrations of CHF3567 and of 2-aminoindane were also proportional to the dose of CHF3381. CHF3381 dose-dependently inhibited MAO-A activity with peak effects at steady-state of 27 +/- 4%, 46 +/- 2% and 65 +/- 5% after 100 mg twice daily, 200 mg twice daily and 400 mg twice daily, respectively. There were no significant effects of CHF3381 on attention (rapid visual information processing), motor co-ordination (body sway) or memory (learning memory task) at any of the doses. At steady-state, there was a significant decrease in alertness (Bond & Lader visual analogue scale) in the 400 mg twice daily group compared with placebo.

CONCLUSIONS

A twice daily regimen of CHF3381 appears to be adequate from a pharmacokinetic and pharmacodynamic perspective. Plasma concentrations reached with 400 mg twice daily exceeded those observed in animals receiving pharmacologically active doses in chronic pain models.

Mechanistic Pharmacokinetic and Pharmacodynamic Modeling of CHF3381 (2-[(2,3-Dihydro-1H-inden-2-yl)amino]acetamide Monohydrochloride), a Novel N-Methyl-d-aspartate Antagonist and Monoamine Oxidase-A Inhibitor in Healthy Subjects

CHF3381 (2-[(2,3-dihydro-1H-inden-2-yl)amino]acetamide monohydrochloride) is a new N-methyl-D-aspartate antagonist and reversible monoamine oxidase-A (MAO-A) inhibitor in development for the treatment of neuropathic pain. This study developed a mechanistic model to describe the pharmacokinetics of CHF3381 and of its two metabolites, the relationship with MAO-A activity and heart rate. Doses of 100, 200, and 400 mg twice daily for 2 weeks were administered orally to 36 subjects. MAO-A activity was estimated by measuring concentrations of 3,4-dihydroxyphenylglycol (DHPG), a stable metabolite of norepinephrine. A multicompartment model with time-dependent clearance was used to describe the kinetics of CHF3381 and metabolite concentrations. Estimated pharmacokinetic parameters were CL (41.2 to 27.4 l/h over the study), V (131 liters), Q (1.7 l/h), V(p) (36 liters), and k(a) (1.85 h(-1)). The relationship between CHF3381 and DHPG or heart rate was described using an indirect or a direct linear model, respectively. The production rate of DHPG (k(in)) was 2540 ng . h(-1), reduced by 63% at maximal CHF3381 concentrations. EC(50) was 1670 mug/l, not significantly different from the in vitro IC(50). The increase in heart rate due to CHF3381 was 0.0055 bpm/micro(g l-1). CHF3381 produces a concentration-dependent decrease in DHPG plasma concentrations, whose magnitude increased after multiple twice-a-day regimens for 14 days.