Muscarinic-3-receptor positive allosteric modulator ASP8302 in patients with underactive bladder. A randomized controlled trial

AIM: The aim of this study is to evaluate safety and efficacy of ASP8302, a novel positive allosteric modulator for the muscarinic M3 receptor (M3-PAM), in patients with underactive bladder (UAB).

METHODS: A randomized, double-blind, placebo-controlled multicenter study was performed in adult male/female subjects with UAB, defined as incomplete bladder emptying (postvoid residual volume [PVR] > 100 ml) without significant bladder outlet obstruction and/or overactive bladder. Subjects were randomized (1:1) to receive 4-week oral once-daily administration of 100 mg ASP8302 or matching placebo. Primary endpoint was a change from baseline in PVR measured by catheterization after standardized bladder filling (PVRC2 ). Other endpoints included PVR and bladder voiding efficiency (BVE) measured in various ways, uroflowmetry, bladder diary, and questionnaires. Pressure-flow studies were performed in a subgroup.

RESULTS: One hundred and thirty-five patients were randomized (ASP8302 group: 65 patients, placebo group: 70 patients). The median change in PVRC2 was -40.0 ml (ASP8302) versus -35.0 ml (placebo) and the difference between groups was -5.0 ml (p = 0.960). In males, functional and symptomatic outcomes improved, for example, maximum urine flow rate (Qmax ) and detrusor pressure at Qmax (Pdet.Qmax ) increased (mean difference in change ASP8302 vs. placebo: 3.8 ml/s, p = 0.031 and 12.7 cm H2 O, p = 0.034, respectively). Urinary incontinence episodes/24 h decreased in males with preexisting incontinence (mean difference: -0.35; p = 0.028). The incidence of adverse events was similar between study groups (ASP8302: 33.3%, placebo: 31.4%). In the included subjects, both baseline urine flow and bladder voiding pressure was low. Compared with PVR, simultaneous BVE measurements were more consistent between various methods (spontaneous vs. standardized bladder filling, catheterization vs. ultrasound [US]).

CONCLUSIONS: ASP8302 was safe and well tolerated in patients with UAB identified by nonurodynamic clinical criteria, but it did not show efficacy in the primary endpoint. However, in males it showed improvement of symptoms and functional parameters. BVE (using US) is a more optimal outcome measure than PVR in UAB.