Anticonvulsant preclinical profile of CHF 3381: dopaminergic and glutamatergic mechanisms

A comparison of bimatoprost 0.03% versus the fixed-combination of latanoprost 0.005% and timolol 0.5% in adult patients with elevated intraocular pressure: an eight-week, randomized, open-label trial

INTRODUCTION AND PURPOSE

Bimatoprost and the fixed combination of latanoprost with timolol maleate are 2 medications widely used to treat glaucoma and ocular hypertension (OHT). The aim of the study is to compare the efficacy of these 2 drugs in reducing intraocular pressure (IOP) after 8 weeks of treatment in patients with primary open angle glaucoma (POAG) or OHT.

METHODS

In this randomized, open-label trial, 44 patients with POAG or OHT were allocated to receive either bimatoprost (1 drop QD) or latanoprost/timolol (1 drop QD). Primary outcome was the mean diurnal IOP measurement at the 8th week, calculated as the mean IOP measurements taken at 8:00 am, 10:00 am, and 12:00 pm Secondary outcomes included the baseline change in IOP measured 3 times a day, after the water-drinking test (performed after the last IOP measurement), and the assessment of side effects of each therapy.

RESULTS

The mean IOP levels of latanoprost/timolol (13.83, SD = 2.54) was significantly lower than of bimatoprost (16.16, SD = 3.28; P < 0.0001) at week 8. Also, the change in mean IOP values was significantly higher in the latanoprost/timolol group at 10:00 am (P = 0.013) and 12:00 pm (P = 0.01), but not at 8:00 am (P = ns). During the water-drinking test, there was no significant difference in IOP increase (absolute and percentage) between groups; however, there was a significant decrease in mean heart rate in the latanoprost/timolol group. Finally, no significant changes in blood pressure and lung spirometry were observed in either groups.

CONCLUSIONS

The fixed combination of latanoprost/timolol was significantly superior to bimatoprost alone in reducing IOP in patients with POAG or OHT. Further studies with large sample sizes should be taken to support the superior efficacy of latanoprost/timolol, as well as to better assess its profile of side effects.

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.

The glutamatergic system and Alzheimer's disease: therapeutic implications

Alzheimer's disease affects nearly 5 million Americans currently and, as a result of the baby boomer cohort, is predicted to affect 14 million Americans and 22 million persons totally worldwide in just a few decades. Alzheimer's disease is present in nearly half of individuals aged 85 years. The main symptom of Alzheimer's disease is a gradual loss of cognitive function. Glutamatergic neurotransmission, an important process in learning and memory, is severely disrupted in patients with Alzheimer's disease. Loss of glutamatergic function in Alzheimer's disease may be related to the increase in oxidative stress associated with the amyloid beta-peptide that is found in the brains of individuals who have the disease. Therefore, therapeutic strategies directed at the glutamatergic system may hold promise. Therapies addressing oxidative stress induced by hyperactivity of glutamate receptors include supplementation with estrogen and antioxidants such as tocopherol (vitamin E) and acetylcysteine (N-acetylcysteine). Therapy for hypoactivity of glutamate receptors is aimed at inducing the NMDA receptor with glycine and cycloserine (D-cycloserine). Recently, memantine, an NMDA receptor antagonist that addresses the hyperactivity of these receptors, has been approved in some countries for use in Alzheimer's disease.

Antinociceptive activity of the N-methyl-D-aspartate receptor antagonist N-(2-Indanyl)-glycinamide hydrochloride (CHF3381) in experimental models of inflammatory and neuropathic pain

N-(2-Indanyl)-glycinamide hydrochloride (CHF3381) is a novel low-affinity, noncompetitive N-methyl-d-aspartate receptor antagonist. The current study compared the antinociceptive effects of CHF3381 with those of gabapentin and memantine in in vitro and in vivo models of pain. In isolated rat spinal cord, CHF3381 and memantine, but not gabapentin, produced similar inhibition of the wind-up phenomenon. CHF3381 suppressed the maintenance of carrageenan-induced thermal and mechanical hyperalgesia in the rat with a minimum significantly effective dose (MED) of 30 mg/kg p.o. Memantine produced a partial reversal of both thermal and mechanical hyperalgesia (MED = 10 and 15 mg/kg i.p., respectively). Gabapentin reversed mechanical hyperalgesia (MED = 10 mg/kg s.c.), but did not affect thermal hyperalgesia. In the mouse formalin test, CHF3381 and memantine preferentially inhibited the late phase (MED = 30 and 20 mg/kg i.p., respectively); gabapentin inhibited only the late phase (MED = 30 mg/kg s.c.). Unlike morphine, CHF3381 chronic administration was not accompanied by the development of tolerance in the formalin test. Furthermore, morphine tolerance did not cross-generalize to CHF3381. In rats with a sciatic nerve injury, CHF3381 relieved both cold and mechanical allodynia (MED = 100 mg/kg p.o.). In contrast, memantine was inactive. Gabapentin blocked cold allodynia (MED = 30 mg/kg s.c.), but had marginal effects on mechanical allodynia. In diabetic neuropathy, CHF3381 reversed mechanical hyperalgesia (MED = 50 mg/kg p.o.). Memantine (15 mg/kg i.p.) produced an antinociceptive effect, whereas gabapentin (100 mg/kg p.o.) had no significant effect. Thus, CHF3381 may be useful for the therapy of peripheral painful neuropathies.

Mechanisms of action of CHF3381 in the forebrain

(1) Aim of this study was to gain insight into the mechanism of action of CHF3381, a novel putative antiepileptic and neuroprotective drug. (2) CHF3381 blocked NMDA currents in primary cultures of cortical neurons: maximal effect was nearly -80% of the NMDA-evoked current, with EC(50) of approximately 5 micro M. This effect was selective, reversible, use-dependent and elicited at the concentrations reached in the rodent brain after peripheral administration of therapeutic doses. (3) CHF3381 also inhibited voltage-gated Na(+) currents in an apparently voltage-dependent manner. However, this effect could be obtained only at relatively high concentrations (100 micro M). (4) Consistent with the mild effects on voltage-gated Na(+) channels, CHF3381 (100 micro M) failed to affect electrical stimulation-evoked glutamate overflow in hippocampal slices. In contrast, the anti-convulsant agent and Na(+) channel blocker lamotrigine (100 micro M) inhibited stimulation-evoked glutamate overflow by approximately 50%. (5) CHF3381 reduced kindled seizure-induced c-fos mRNA levels within the same brain regions, and to a similar level, as the selective NMDA receptor antagonist MK801, providing circumstantial evidence to the idea that CHF3381 blocks NMDA receptors in vivo. (6) The present mechanistic studies suggest that the primary mechanism of action of CHF3381 in the forebrain is blockade of NMDA receptors. On this basis, this compound may have a potential use in other diseases caused by or associated with a pathologically high level of NMDA receptor activation.

Safety, pharmacokinetics, and pharmacodynamics of CHF 3381, a novel N-methyl-D-aspartate antagonist, after single oral doses in healthy subjects

A double-blind, randomized, placebo-controlled study was performed to assess the safety, tolerability, and pharmacokinetics of single oral doses of CHF 3381 in 56 young healthy male volunteers. The central nervous system effects of CHF 3381 were also evaluated, as well as the effect of food on the rate and extent of CHF 3381 absorption. Seven doses of CHF 3381 (25, 50, 100, 200, 300, 450, and 600 mg) were evaluated in an escalating order. At each dose level, 6 subjects were given CHF 3381, and 2 subjects were given placebo. Safety and tolerability evaluation included adverse events, physical examination, vital functions, electrocardiogram, laboratory tests, and 24-hour Holter (100-mg and 450-mg dose panels). Plasma and urinary concentrations of CHF 3381 and its two main metabolites (CHF 3567 and 2-aminoindane) were measured with a validated high-performance liquid chromatography method. Central nervous system effects were evaluated with the simple reaction time (SRT); learning memory task (LMT); Bond & Lader Visual Analog Scale for alertness, contentedness, and calmness; Addiction Research Center Inventory (ARCI); and electroencephalogram. There were no serious adverse events; the most frequent adverse events were dizziness, abnormal thinking, and asthenia. The number of adverse events with moderate intensity increased sharply with the dose, with no or few events up to 450 mg and 17 events with 600 mg. Therefore, 600 mg was defined as the maximum tolerated dose. There were no significant treatment effects on cardiovascular function and electrocardiogram parameters at any CHF 3381 dose or on oral temperature or laboratory tests. There were no clinically significant changes in laboratory variables. CHF 3381 was absorbed rapidly (tmax = 0.5-2 h) and cleared from plasma with a half-life of 3 to 4 hours. Plasma levels of CHF 3381 and its two major metabolites were found to be proportional to the dose. 2-Aminoindane formed slowly and reached much lower concentrations compared to the parent compound and the other metabolite (CHF 3567). Within 48 hours after dosing, 2% to 6% of the administered dose was found in the urine as unchanged drug, about 50% to 55% as the acid derivative (CHF 3567), and 2% to 3% as 2-aminoindane. Ingestion of food did not affect the extent of absorption of the drug, while the rate of absorption was considerably reduced (tmax = 4 h). No significant effects of CHF 3381 were observed on attention (SRT) or memory (LMT). Visual analog scales revealed a decreasing effect of CHF 3381 on alertness at 1 hour that reached statistical significance at 300 and 600 mg. EEG spectral analysis revealed minor decreasing effects of the 200-mg dose on total electric power measured at 2 hours. A stimulant effect was detected by the ARCI scale 24 hours after the 300-mg dose and might be related to the slow formation of the 2-aminoindane metabolite. In conclusion, this study has shown that the maximum tolerated dose of CHF 3381 after single oral administration in young healthy male volunteers is 600 mg. CHF 3381 displays linear pharmacokinetics in the dose range of 25 to 600 mg. The compound is rapidly absorbed and cleared from plasma with a half-life of 3 to 4 hours. The ingestion of food seems to not affect the extent of absorption of the drug. Minor effects on the central nervous system were detected at doses equal to or greater than 300 mg.

Neuroprotective activity of CHF3381, a putative N-methyl-D-aspartate receptor antagonist

The aim of this study was to evaluate the neuroprotective effect of CHF3381, a novel putative NMDA antagonist characterized by a good therapeutic index. We have compared the effects of CHF3381 on kainate seizure-induced neurodegeneration with those produced by the non competitive NMDA receptor antagonist MK-801 and by the Na channel blocker lamotrigine. All compounds have been employed at doses incapable of preventing or attenuating seizures. The fluorescent marker Fluoro-Jade B has been used to identify degenerating cells. Animals pretreated with lamotrigine presented the same degree of cell damage as the controls. As for the controls, a clear correlation was also observed between seizure severity and neurodegeneration. In contrast, MK-801 and CHF3381 completely prevented cell damage. These data indicate that CHF3381 may be successfully utilized in neurological disorders characterized by or associated with neurodegenerative excitotoxicity.