Preclinical characterization of the antiviral activity of SCH 900518 (narlaprevir), a novel mechanism-based inhibitor of hepatitis C virus NS3 protease.

Small-molecule hepatitis C virus (HCV) NS3 protease inhibitors such as boceprevir (SCH 503034) have been shown to have antiviral activity when they are used as monotherapy and in combination with pegylated alpha interferon and ribavirin in clinical trials. Improvements in inhibitor potency and pharmacokinetic properties offer opportunities to increase drug exposure and to further increase the sustained virological response. Exploration of the structure-activity relationships of ketoamide inhibitors related to boceprevir has led to the discovery of SCH 900518, a novel ketoamide protease inhibitor which forms a reversible covalent bond with the active-site serine. It has an overall inhibition constant (K*(i)) of 7 nM and a dissociation half-life of 1 to 2 h. SCH 900518 inhibited replicon RNA at a 90% effective concentration (EC(90)) of 40 nM. In biochemical assays, SCH 900518 was active against proteases of genotypes 1 to 3. A 2-week treatment with 5x EC(90) of the inhibitor reduced the replicon RNA level by 3 log units. Selection of replicon cells with SCH 900518 resulted in the outgrowth of several resistant mutants (with the T54A/S and A156S/T/V mutations). Cross-resistance studies demonstrated that the majority of mutations for resistance to boceprevir and telaprevir caused similar fold losses of activity against all three inhibitors; however, SCH 900518 retained more activity against these mutants due to its higher intrinsic potency. Combination treatment with alpha interferon enhanced the inhibition of replicon RNA and suppressed the emergence of resistant replicon colonies, supporting the use of SCH 900518-pegylated alpha interferon combination therapy in the clinic. In summary, the results of the preclinical characterization of the antiviral activity of SCH 900518 support its evaluation in clinical studies.

[Ketorolac protection in damage due to myocardial ischemia and reperfusion]. / Protección por Ketorolac en el daño producido por isquemia y reperfusión miocardica.

This study shows that the nonsteroidal anti-inflammatory drug. Ketorolac, has an ionophore-like action for calcium, such a drug may transfer calcium through an hydrophobic phase. This property does not affect the respiratory rate of mitochondria. These results indicate that the ionophoretic effect is not due to an uncoupling action of Ketorolac. The effect of this compound was tested in a reperfusion model where it was observed that Ketorolac (1 mg/Kg weight) administered 30 min before an ischemic period was induced, reverts the arrhythmic effect of reperfusion. These results are in agreement with the analysis of the plasmatic concentrations of the enzymes creatine kinase and lactic dehydrogenase. It was found that the levels of such enzymes were lower in Ketorolac treated group, than in the untreated one. The results clearly indicate that Ketorolac prevents from the myocardial damage induced by reperfusion, probably by avoiding calcium overload in myocytes.

Fluorescamine-induced membrane permeability in mitochondria.

1. Addition of fluorescamine (75 microM) to mitochondria induced an increase in membrane permeability. 2. The leakiness of the inner mitochondrial membrane is characterized by extensive release of accumulated Ca2+, collapse of the transmembrane potential, mitochondrial swelling and efflux of matrix proteins, among them, malate dehydrogenase. 3. These effects were diminished by supplementing the media with 1 mM phosphate, and partially prevented by Mg2+. 4. These results indicate that the primary amino groups of membrane components contribute, partially, to the maintenance of the permeability barrier in mitochondria.