NVP-QBE170: an inhaled blocker of the epithelial sodium channel with a reduced potential to induce hyperkalaemia

BACKGROUND AND PURPOSE

Inhaled amiloride, a blocker of the epithelial sodium channel (ENaC), enhances mucociliary clearance (MCC) in cystic fibrosis (CF) patients. However, the dose of amiloride is limited by the mechanism-based side effect of hyperkalaemia resulting from renal ENaC blockade. Inhaled ENaC blockers with a reduced potential to induce hyperkalaemia provide a therapeutic strategy to improve mucosal hydration and MCC in the lungs of CF patients. The present study describes the preclinical profile of a novel ENaC blocker, NVP-QBE170, designed for inhaled delivery, with a reduced potential to induce hyperkalaemia.

EXPERIMENTAL APPROACH

The in vitro potency and duration of action of NVP-QBE170 were compared with amiloride and a newer ENaC blocker, P552-02, in primary human bronchial epithelial cells (HBECs) by short-circuit current. In vivo efficacy and safety were assessed in guinea pig (tracheal potential difference/hyperkalaemia), rat (hyperkalaemia) and sheep (MCC).

KEY RESULTS

In vitro, NVP-QBE170 potently inhibited ENaC function in HBEC and showed a longer duration of action to comparator molecules. In vivo, intratracheal (i.t.) instillation of NVP-QBE170 attenuated ENaC activity in the guinea pig airways with greater potency and duration of action than that of amiloride without inducing hyperkalaemia in either guinea pig or rat. Dry powder inhalation of NVP-QBE170 by conscious sheep increased MCC and was better than inhaled hypertonic saline in terms of efficacy and duration of action.

CONCLUSIONS AND IMPLICATIONS

NVP-QBE170 highlights the potential for inhaled ENaC blockers to exhibit efficacy in the airways with a reduced risk of hyperkalaemia, relative to existing compounds.

The design and synthesis of thrombin inhibitors: analogues of MD805 containing non-polar surrogates for arginine at the P1 position

A series of monocyclic and bicyclic amino acids have been synthesised and incorporated into thrombin inhibitors based on CGH728, an analogue of the Mitsubishi compound MD805. Benzthiazolylalanine (Bta) was found to be a good non-polar substitute for arginine at the P1 position, yielding compounds with low nanomolar potency and good selectivity for thrombin.

Tropisetron for the prevention of postoperative nausea and vomiting in women undergoing gynecologic surgery

The aim of this study was to evaluate the efficacy of tropisetron, a selective 5-hydroxytryptamine type 3 (5-HT3) receptor antagonist, versus placebo in the prevention of postoperative nausea and vomiting in patients undergoing general anesthesia for gynecologic surgery. Ten minutes before induction of general anesthesia, 80 patients received in a double-blind manner a single intravenous (IV) injection of either 5 mg tropisetron or a matching placebo. Anesthesia was induced with thiopental and maintained with nitrous oxide and enflurane in oxygen. In the first 24 h postoperatively 7 of 40 patients (17.5%) given tropisetron and 16 of 40 patients (40%) receiving placebo vomited (P < 0.05). The incidence of nausea was 30% (12/40) in the tropisetron group and 52% (21/40) in the placebo group (P < 0.05). A total effective antiemetic response showed 26 patients (65%) in the tropisetron group and 16 patients (40%) in the placebo group (P < 0.05). We conclude that tropisetron given IV prior to gynecologic procedures in general anesthesia significantly reduces postoperative nausea and vomiting when compared to placebo without causing any adverse effect.