S-ethyl N-[4-(trifluoromethyl)phenyl] Isothiourea (hydrochloride)

S-ethyl N-[4-(trifluoromethyl)phenyl] Isothiourea (hydrochloride) is a selective and competitive nNOS inhibitor with Ki value of 0.32 μM for the purified human enzyme [1].

Nitric oxide (NO) is an endogenously produced inorganic free radical gas which has been implicated in blood pressure homeostasis, platelet aggregation, neurotransmission, and immunological defense mechanisms. NO is synthesized by three isoforms of nitric oxide synthase (NOS): nNOS, eNOS and iNOS [1].

S-ethyl N-[4-(trifluoromethyl)phenyl] Isothiourea (hydrochloride) (EPIT) is a selective and competitive nNOS inhibitor. S-ethyl N-[4-(trifluoromethyl)phenyl] Isothiourea inhibited human nNOS, eNOS and iNOS with Ki values of 0.32 μM, 9.4 μM and 37 μM, respectively. EPIT exhibited 115-fold and 29-fold selectivity for nNOS compared to iNOS and eNOS, respectively [1].

In mice, EPIT administered intravenously at 25 mg/kg readily penetrated the blood-brain barrier, immediately reaching concentrations in the brain equal to the plasma concentration. In rat brain slices, EPIT failed to inhibit nNOS activity, possibly due to reduced intracellular uptake [1].

Reference:
[1].  Shearer BG, Lee S, Oplinger JA, et al. Substituted N-phenylisothioureas: potent inhibitors of human nitric oxide synthase with neuronal isoform selectivity. J Med Chem. 1997 Jun 6;40(12):1901-5.