A phase I double-blind, placebo-controlled, single rising dose study to determine the safety, tolerability, and pharmacokinetics of oral YM934 in healthy male volunteers

How First-Time-in-Human Studies Are Being Performed: A Survey of Phase I Dose-Escalation Trials in Healthy Volunteers Published Between 1995 and 2004

First-time-in-human studies are small, time-lagged dose-escalation studies including volunteer subjects evaluating safety and tolerability. There is little consensus in the design of a first-time-in-human study, and it is difficult to get an overview of studies performed. One hundred five studies comprising 3323 healthy volunteers published in the 5 major clinical pharmacology journals since 1995 were analyzed. The average trial was placebo controlled, double blind including 32 subjects at 5 dose levels but with great variation in cohort size and dose-escalation method. The parallel single-dose design was the most common design, with the crossover designs being more frequent in the early publications. Despite discussions on the optimization of phase I trials, little seems to be happening. The development of study designs and evaluation methods for cancer trials is extensive, but formal statistically based methods and more scientific study designs are unusual in phase I dose-escalation trials in healthy volunteers.

Potassium channel subtypes as molecular targets for overactive bladder and other urological disorders

Potassium channels have re-emerged as attractive targets for overactive bladder and other urological diseases in recent years, in part due to an enhanced understanding of their molecular heterogeneity, tissue distribution, functional roles and regulation in physiological and pathological states. Cloning and heterologous expression analysis, coupled with the advancement of improved high-throughput screening techniques, have enabled expeditious identification of selective small-molecule openers and blockers for ATP-sensitive K+ channels, Ca2+-activated K+ channels and voltage-dependent K+ channel-KQT-like subfamily (KCNQ) members, and has paved the way in the assessment of efficacy and adverse effects in preclinical models. This review focuses on the rationale for molecular targeting of K+ channels, the current status of target validation, including preclinical proof-of-concept studies, and provides perspectives on the limitations and hurdles to be overcome in realising the potential of these targets for diverse urological indications such as overactive bladder, erectile dysfunction and prostate diseases.

Effects of ATP-sensitive K+ channel openers and tolterodine on involuntary bladder contractions in a pig model of partial bladder outlet obstruction

AIMS

To compare in vivo the efficacy, potency, and bladder-vascular selectivity of ATP-sensitive potassium channel openers (KCOs), YM934 and (-)-cromakalim to a muscarinic antagonist, tolterodine in a novel partial outlet obstructed pig model.

METHODS

Partially obstructed female Landrace pigs were implanted with telemetry transmitters to allow the continuous measurement of intravesical, abdominal and arterial pressures. A subcutaneous port catheter was used to adjust bladder volume. Bladder and arterial pressure were simultaneously monitored under isoflurane anesthesia before and after increasing i.v. doses of test compounds.

RESULTS

Under anesthesia, voiding was completely inhibited, but spontaneous, nonvoiding bladder contractions were observed with mean amplitude of 16 +/- 1 cm H(2)O, duration of 35 +/- 2 seconds, and intercontraction interval of 43 +/- 4 seconds (n = 25). YM934 and (-)-cromakalim both caused dose-dependent decreases in bladder contraction area under the curve (AUC) with effective doses to inhibit AUC by 35% of 3.6 and 14.9 nmol/kg, i.v., respectively. However, concomitant reductions in mean arterial pressure of 12 and 13% were also observed. Tolterodine did not inhibit spontaneous bladder contractions at doses up to 100 nmol/kg, i.v. corresponding to plasma concentrations up to 41 ng/mL.

CONCLUSIONS

The superior efficacy of KCOs to inhibit spontaneous bladder contractions relative to tolterodine support the hypothesis that KCOs may provide an alternate therapeutic mechanism to treat symptoms of overactive bladder if bladder-vascular selectivity can be sufficiently improved. The minimally invasive model described herein appears useful in the preclinical evaluation of potential therapeutics targeted to treat the overactive bladder.