Pharmacokinetics of nefiracetam and three metabolites in humans and stereoselective hydroxylation of its pyrrolidine ring

Pharmacological reversal of synaptic and network pathology in human MECP2-KO neurons and cortical organoids

Duplication or deficiency of the X-linked MECP2 gene reliably produces profound neurodevelopmental impairment. MECP2 mutations are almost universally responsible for Rett syndrome (RTT), and particular mutations and cellular mosaicism of MECP2 may underlie the spectrum of RTT symptomatic severity. No clinically approved treatments for RTT are currently available, but human pluripotent stem cell technology offers a platform to identify neuropathology and test candidate therapeutics. Using a strategic series of increasingly complex human stem cell-derived technologies, including human neurons, MECP2-mosaic neurospheres to model RTT female brain mosaicism, and cortical organoids, we identified synaptic dysregulation downstream from knockout of MECP2 and screened select pharmacological compounds for their ability to treat this dysfunction. Two lead compounds, Nefiracetam and PHA 543613, specifically reversed MECP2-knockout cytologic neuropathology. The capacity of these compounds to reverse neuropathologic phenotypes and networks in human models supports clinical studies for neurodevelopmental disorders in which MeCP2 deficiency is the predominant etiology.

Nefiracetam metabolism by human liver microsomes: role of cytochrome P450 3A4 and cytochrome P450 1A2 in 5-hydroxynefiracetam formation

An in-vitro study was conducted to investigate the metabolism of nefiracetam in human liver microsomes and to identify the enzymes responsible for the metabolism. Nefiracetam was hydroxylated by human liver microsomes to 5-hydroxynefiracetam (5-OHN). Eadie-Hofstee plots for the formation of 5-OHN suggested substrate activation. The kinetic parameters, apparent Km, Vmax, and Hill coefficient, for the formation of 5-OHN by pooled human liver microsomes were 4012 microM, 2.66 nmol min(-1) (mg protein)(-1), and 1.65, respectively. The formation of 5-OHN was significantly correlated with cytochrome P450 (CYP)3A4-mediated testosterone 6beta-hydroxylase activity and dextromethorphan N-demethylase activity. The 5-OHN formation was inhibited (94%) by antibody to human CYP3A4/5. The 5-OHN formation was also inhibited by the CYP3A4 inhibitors ketoconazole and troleandomycin, but not significantly inhibited by several other P450 inhibitors. The microsomes containing cDNA-expressed CYP3A4 formed 5-OHN with sigmoidal kinetics. CYP3A5-containing microsomes did not form 5-OHN. These results indicated that CYP3A, most likely CYP3A4, was the major isozyme responsible for the formation of 5-OHN in human liver microsomes. CYP1A2 and CYP2C19 microsomes were also capable of forming 5-OHN. However, the contribution of CYP1A2 was considered to be relatively minor compared with that of CYP3A4, and the contribution of CYP2C19 was assumed to be negligible, based on the result of the immunoinhibition study and taking into account both the turnover rate by each isozyme and the relative abundance of each isozyme in human liver. We conclude that on average the formation of 5-OHN, the major metabolite of nefiracetam, is principally mediated by CYP3A4 with a relatively minor contribution by CYP1A2.

Nefiracetam hydroxylation by rat liver microsomes and expressed human cytochrome P450s

1. The metabolism of nefiracetam, a novel cognition-enhancer, by rat liver microsomes has been studied. 2. Formation of 5-hydroxy (5-OH-NEF) and hydroxymethyl (HM-NEF) derivatives was the principal pathway of NEF oxidation in male rats, and followed Michaelis-Menten kinetics with Km values of 2.9 and 3.3 mM, and Vmax values of 7.8 and 4.5 nmol/min/mg protein, respectively. 3. Enzymes catalysing the formation of these two major metabolites were examined. 5-OH-NEF formation was inhibited by antibody to rat CYP3A2 by 60%, and antibodies to CYP2B1, CYP2C11 and CYP2E1 also showed 15-25% inhibition of the formation of 5-OH-NEF. The formation of HM-NEF was inhibited by antibodies to CYP2C11 and CYP2B1 by 80% and 35%, respectively. These findings indicate that CYP3A plays a major role in the formation of 5-OH-NEF, and CYP2B, CYP2C11 and CYP2E1 are also involved to some extent in the 5-hydroxylation, and that CYP2C11 is mainly responsible for HM-NEF formation, and CYP2B is also involved in that catalysis in male rats. The results from the studies of the effects of various chemical inducers, of selective substrates or inhibitors of P450s on the formation of these metabolites also supported these latter findings. 4. NEF metabolism in microsomes prepared from B-lymphoblastoid cells expressing human cytochrome P450s showed that 5-OH-NEF formation by CYP3A4 is the principal metabolic pathway in humans.