CL-275838

Hepatic microsomal metabolism of the potential memory-enhancing agent, CL 275,838, to its desbenzyl derivative

1. The oxidation of the potential memory-enhancer and antidepressant agent CL 275,838 by rat liver microsomes was investigated. CL 275,838 was rapidly and extensively biotransformed in vitro to its desbenzyl derivative (II), the main metabolite observed in vivo. No other known metabolites could be detected in the incubation mixture except for trace amounts of a hydrolysis product (IV). 2. The formation of the desbenzylated derivative II required the presence of an NADPH-generating system and was significantly inhibited by carbon monoxide, SKF 525-A and cimetidine, indicating the participation of P450 in the oxidation of CL 275,838. The reaction was markedly enhanced by phenobarbital and by pregnenolone-16 alpha-carbonitrile [particularly in the female]. beta-Naphthoflavone did not significantly affect desbenzylation. 3. Kinetic studies indicate that there are sex-dependent differences in CL 275,838 metabolism in vitro, as observed in vivo in rat. Maximal velocity for the oxidation of CL 275,838 in microsomes isolated from the male rat was 17 times greater than in the female rat. The apparent Km for metabolism of CL 275,838 was similar in microsomes derived from the male and female rat. 4. CL 275,838 does not appreciably affect its own oxidation and does not cause significant hepatic microsomal enzyme induction in the male or female rat, except for slight enhancement of some components of the P450 system at doses (300 mg/kg once daily for 7 days) well above the effective pharmacological range.

Single-dose safety and pharmacokinetics of a potential cognition-enhancing compound, CL 275,838, in healthy volunteers

The pharmacokinetics and safety of CL 275,838, a potential cognition-enhancing compound, were studied after single escalating oral doses first in young healthy male volunteers and then in old (60-74 years) and very old (over 75 years) volunteers of both sexes. In all age groups absorption of CL 275,838 was rapid as assessed by the mean time to reach maximum plasma concentrations (Cmax) which averaged 1-2 hr, regardless of the dose administered. In young male volunteers both Cmax and area under the curve (AUC) increased proportionally with dose from 10 to 100 mg. Mean elimination half-lives (t1/2) of the parent compound (18-21 hr) and of its circulating metabolites II (20-22 hr) and IV (27-30 hr) were well comparable for the doses tested (50 and 100 mg). Age did not appreciably affect plasma Cmax of CL 275,838 or its two metabolites. Mean AUC and elimination half-life did not appreciably differ between old and very old subjects given 50 mg CL 275,838, with the limitations dictated by the small number of elderly subjects examined. Compared with younger volunteers receiving comparable doses, however, the elderly had higher mean plasma AUC of the unchanged compound and its two metabolites, although the parameter varied widely between subjects. The mean elimination t1/2 (+/- SD) was longer in the elderly (38.8 +/- 19.6, 50.5 +/- 24.5 and 41.7 +/- 12.1 hr, respectively, for the parent compound and its metabolites II and IV) than in the young subjects. The cause(s) of these variations and the possible clinical implications remain to be established.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain uptake and distribution of the potential memory enhancer CL 275,838 and its main metabolites in rats: relationship between brain concentrations and in vitro potencies on neurotransmitter mechanisms

The kinetics, brain uptake and distribution of CL 275,838, a potential memory enhancer, and its main metabolites (II and IV) were evaluated in rats after intraperitoneal doses of 5, 10 and 20 mg/kg. Brain maximum concentrations (Cmax) of the three compounds after pharmacologically active doses were then related to the in vitro concentrations affecting some monoaminergic and amino acid receptor sites to examine the relative importance of these neurotransmitter systems in the pharmacological actions of CL 275,838. After 10 mg/kg CL 275,838, the unchanged compound rapidly entered the brain and distributed almost uniformly in various regions inside the blood-brain barrier. Its disappearance from brain and plasma was almost parallel with a comparable elimination half-life (t 1/2) of about 2 h. Metabolite II entered the brain and equilibrated with plasma more slowly than the parent compound, achieving mean Cmax (0.2 microM) within 3 h of dosing. Metabolite IV was rapidly detected in rat brain but hardly amounted to 10% (0.1 microM) of the parent compound Cmax (1 microM). There was a linear relationship between dose and plasma and brain concentrations of the three compounds up to 20 mg/kg CL 275,838. At micromolar concentrations the parent compound had affinity for serotonin (5-HT) uptake sites, 5-HT2 and dopamine (DA2) receptors. Only at much higher concentrations than those achieved in vivo after pharmacologically active doses did it increase the binding of 3H-glutamate to NMDA (N-methyl-D-aspartate) receptors. Metabolite II has a similar neurochemical profile.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple-dose pharmacokinetics and safety of a potential memory-enhancing compound, CL 275,838, in healthy male volunteers

The pharmacokinetics and safety of CL 275,838, a new potential memory-enhancing compound, were examined after 14 daily doses (50 and 100 mg) in 16 healthy male volunteers, age 20 to 59 years, in a randomized, double-blind, placebo-controlled, parallel group study. Trough blood samples (predose) were collected on days 2, 4, 7, 10, and 14, and further samples were drawn after the final dose (day 14) to define the multiple-dose kinetics of the parent compound and its metabolites II and IV. Intercurrent clinical events, vital functions, EEG, ECG, and cognitive tests (attention, verbal memory, and spatial memory) were considered as outcome measures of safety. Performance in cognitive tests was also studied to collect preliminary information on possible therapeutic action. Predose plasma concentrations of the parent compound and its two metabolites increased approximately in proportion to the dose, and accumulation was complete within 7 days, regardless of the dose. At steady state, mean Cmax and AUC of the parent compound and its two metabolites were dose related. Mean wash-out t1/2 was 18 to 20 hours for the parent compound, 22-23 hours for metabolite II, and 28-33 hours for metabolite IV; these elimination t1/2 are comparable for the two doses, and are similar to those observed in single-dose studies. For the 50-mg-dose group, predicted and observed average plasma concentrations (Css) of CL 275,838 and its two metabolites did not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Liquid chromatography of the potential memory-enhancing agent CL 275,838 and its main metabolites, using a post-column photochemical reactor and fluorimetric detection

On irradiation with short-wavelength ultraviolet light, the potential memory-enhancing compound CL 275,838 (I) and its desbenzyl derivative CL 286,527 (metabolite II) are cleaved into the highly fluorescent derivative CL 228,346 (metabolite IV). This reaction was exploited for the sensitive and selective detection of these compounds in human and animal plasma, after reversed-phase high-performance liquid chromatography on a Supelco LC18 DB column (15 cm x 4.6 mm I.D.) at room temperature. The parent compound and its metabolites were isolated from plasma constituents using the Sep-Pak C18 Plus cartridge, with satisfactory recovery (76-90%) and selectivity. The detection limits were ca. 1.25, 5 and 0.3 ng/ml for I, II and IV, respectively, using 1 ml of plasma. The validation procedure, which includes analysis of multiple ascending calibration curves based on between-day values and replicate analysis of quality control samples analysed with each standard curve, indicated acceptable precision and accuracy of the method within the concentration ranges investigated, the overall coefficient of variation and relative error being less than 10%. The method was successfully applied to plasma samples from healthy volunteers and animals after single of multiple doses of compound I. Metabolites II and IV were detectable in plasma of all species, the former at higher concentrations than the parent compound and metabolite IV. Together with the fact that metabolite II retains much of the parent compound's biological activity in vivo and in vitro, this suggests that it may contribute to the pharmacological effects of compound I.