Nepicastat (SYN-117) HCl

2 years -80 in solvent

Administered via p.o.

Nepicastat hydrochloride is currently in Phase II clinical trials in patients with Posttraumatic Stress Disorder.

Nepicastat hydrochloride is dissolved in distilled water.

In vitro, Nepicastat hydrochloride shows the selective and concentration-dependent inhibition effects on bovine and human dopamine-beta-hydroxylase activity with IC50 of 8.5 nM and 9.0 nM, respectively. While Nepicastat hydrochloride has negligible affinity for twelve other enzymes and thirteen neurotransmitter receptors. [1]

In vitro studies, Bovine and human dopamine-beta-hydroxylase activity are assayed by measuring the conversion of tyramine to octopamine. Human dopamine-beta-hydroxylase is purified from the culture medium of the neuroblastoma cell line SK-N-SH. The assay is performed at pH 5.2 and 32C in a medium containing 0.125 M sodium acetate, 10 mM fumarate, 0.5 +/- 2 uM CuSO4, 0.1 mg/mL catalase, 0.1 mM tyramine and 4 mM ascorbate. In a typical assay, 0.5 +/- 1 mu of enzyme are added to the reaction mixture and, subsequently, a substrate mixture containing catalase, tyramine and ascorbate is added to initiate the reaction (final volume of 0.2 mL). Samples are incubated with or without the appropriate concentration of nepicastat (RS-25560-197, S-enantiomer) or RS-25560-198 (R-enantiomer) at 37 C for 30-40 minutes. The reaction is quenched by the stop solution containing 25 mM EDTA and 240 uM 3-hydroxytyramine (internal standard). The samples are analysed for octopamine by reverse phase high pressure liquid chromatography (h.p.l.c.) with ultraviolet (u.v.)-detection at 280 nM. The h.p.l.c. run is carried out at a flow rate of 1 mL/min with a LiChroCART 125-4 RP-18 column and isocratic elution with 10 mM acetic acid, 10 mM 1-heptane sulphonic acid, 12 mM tetrabutyl ammonium phosphate and 10% methanol. The remaining % activity is calculated based on controls (without RS 25560), corrected with internal standards and fitted to a non-linear four-parameter concentration-response curve. The activity of nepicastat at twelve selected enzymes and receptors is determined by use of established assays. Binding data are analysed by iterative curve-fitting to a four parameter logistic equation. Ki values are calculated from IC50 values by the Cheng-Pruso€ equation. Enzyme inhibitory activity is expressed as IC50 (concentration required to produce 50% inhibition of enzyme activity).

Nepicastat (SYN-117) HCl is a potent and selective inhibitor of both bovine and human dopamine-β-hydroxylase with IC50 of 8.5 nM and 9 nM, with negligible affinity for twelve other enzymes and thirteen neurotransmitter receptors. Phase 2.