An ion channel library for drug discovery and safety screening on automated platforms.

Ion channels represent the third largest class of targets in drug discovery after G-protein coupled receptors and kinases. In spite of this ranking, ion channels continue to be under exploited as drug targets compared with the other two groups for several reasons. First, with 400 ion channel genes and an even greater number of functional channels due to mixing and matching of individual subunits, a systematic collection of ion channel-expressing cell lines for drug discovery and safety screening has not been available. Second, the lack of high-throughput functional assays for ion channels has limited their use as drug targets. Now that automated electrophysiology has come of age and provided the technology to assay ion channels at medium to high throughput, we have addressed the need for a library of ion channel cell lines by constructing the Ion Channel Panel (ChanTest Corp., Cleveland, OH). From 400 ion channel genes, a collection of 82 of the most relevant human ion channels for drug discovery, safety, and human disease has been assembled.Each channel has been stably overexpressed in human embryonic kidney 293 or Chinese hamster ovary cells. Cell lines have been selected and validated on automated electrophysiology systems to facilitate cost-effective screening for safe and selective compounds at earlier stages in the drug development process. The screening and validation processes as well as the relative advantages of different screening platforms are discussed.

Efficacy and safety of fexofenadine hydrochloride for treatment of seasonal allergic rhinitis.

BACKGROUND: H1-receptor antagonists are effective for the treatment of seasonal allergic rhinitis. In rare circumstances, some second-generation H1-receptor antagonists have been associated with prolongation of the corrected QT interval (QTc), thus increasing the risk of ventricular arrhythmias. Fexofendine HCl, the carboxylic acid metabolite of terfenadine, is a new second-generation antihistamine that is nonsedating and does not cause electrocardiographic effects. OBJECTIVE: To investigate the clinical efficacy and safety of fexofenadine HCl in the treatment of ragweed seasonal allergic rhinitis and to characterize the dose-response relationship of fexofenadine HCl at dosages of 60, 120, and 240 mg bid. METHODS: A multicenter, 14-day, placebo-controlled, double-blind trial was conducted with patients suffering from moderate to severe ragweed seasonal allergic rhinitis who met symptom severity criteria after a 3-day placebo baseline period. Patients with minimal or very severe symptoms during the baseline period were excluded. Patients were randomized to receive fexofenadine HCl (60, 120, or 240 mg bid) or placebo at 12-hour dosing intervals (7:00 AM and 7:00 PM). The primary efficacy measure was patient-assessed 12-hour reflective total symptom score before the evening dose (trough). RESULTS: Five hundred seventy patients completed the trial. Fexofenadine HCl at each dosage provided significant improvement in total symptom score (P < or = .003) and in all individual nasal symptoms compared with placebo. The frequency of adverse events was similar among fexofenadine HCl and placebo groups, with no dose-related trends. No sedative effects or electrocardiographic abnormalities, including prolongations in QTc were detected. CONCLUSIONS: Fexofenadine HCl is both effective and safe for the treatment of ragweed seasonal allergic rhinitis. Because there was no additional efficacy at higher dosages, 60 mg bid appears to be the optimal therapeutic dosage for these patients.

Safety and efficacy of terfenadine/pseudoephedrine versus clemastine/phenylpropanolamine in the treatment of seasonal allergic rhinitis.

A double-blind, randomized, placebo-controlled, parallel trial was conducted to compare the efficacy and safety of terfenadine, 60 mg (immediate-release)/pseudoephedrine hydrochloride, 120 mg (controlled-release) (T/Ps) and clemastine fumarate, 1.34 mg (immediate-release)/phenylpropanolamine, 75 mg (sustained-release) (C/Ph) in a combination tablet b.i.d. in 178 patients (12-59 years of age) with symptoms of seasonal allergic rhinitis. After seven days of treatment, the total symptom scores recorded in the diaries of 175 patients showed that both therapies had a highly significant overall treatment effect when compared with placebo (P < or = .02). The overall level of improvement, as well as improvement of individual symptoms, was similar with the two therapies. Total symptom scores assigned by physicians to 170 patients showed significant and similar levels of improvement with both therapies when compared with placebo (P < .01). The two therapies were also similar on physicians' evaluations of overall effectiveness. Both therapies relieved most histamine-mediated symptoms as well as nasal congestion, although only T/Ps showed improvement of the latter symptom in both the patients' diaries and physicians' evaluations. Among 178 patients, drowsiness and fatigue occurred more often in the C/Ph group (25% and 11.7% for the two adverse events, respectively) than in the T/Ps group (10.2% and 1.7%, respectively). The incidence of insomnia and dry mouth/nose/throat was higher with T/Ps (23.7% and 11.9%, respectively) than with C/Ph (6.7% and 3.3%, respectively). No serious or unexpected adverse events were reported. These results indicate that T/Ps and C/Ph are both superior to placebo and equally effective in the treatment of symptoms of seasonal allergic rhinitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Multicenter, crossover study of the efficacy and tolerability of terfenadine, 120 mg, versus cetirizine, 10 mg, in perennial allergic rhinitis.

In this 3-week randomized, double-blind, double-dummy multicenter, crossover study terfenadine, 120 mg, was compared with cetirizine, 10 mg, both given once daily in the treatment of perennial allergic rhinitis in sixty patients. Compared with the investigators' pretreatment assessment, both terfenadine and cetirizine significantly reduced the severity of all five symptoms (P less than .001). The two treatments were equally effective in controlling eye irritation, sneezing, nasal congestion and itchy nose, throat and palate, but cetirizine improved rhinorrhea more than terfenadine (P less than .05). Daily symptom assessments by the patients for the last 14 days of each treatment period showed no difference in efficacy between the two drugs for any of the symptoms. There were also no differences between the two drugs for overall assessments of efficacy or patient preference. Adverse events were recorded more frequently while taking cetirizine, with 14 attributable events compared with only five with terfenadine. Four of the cetirizine-related events were drowsiness or tiredness, but none was reported while patients were taking terfenadine. There was a tendency to increased weight (greater than 1 kg) with both treatments.