Imidafenacin for the treatment of overactive bladder

Imidafenacin, An Orally Active Muscarinic Receptor Antagonist, Improves Pulmonary Function In Patients With Chronic Obstructive Pulmonary Disease: A Multicenter, Randomized, Double-Blind, Placebo-Controlled 3×3 Crossover Phase II Trial

Background

Although long-acting muscarinic receptor antagonists are central to the management of chronic obstructive pulmonary disease (COPD), inhaled medicines may have technical difficulty in some patients and adherence barriers.

Methods

A multicenter, randomized, double-blind, placebo-controlled 3×3 crossover Phase II trial was performed to evaluate the efficacy and safety of oral administration of the antimuscarinic agent imidafenacin in patients with COPD. Twenty-seven male COPD patients with % forced expiratory volume in 1 s (FEV₁) ≥30% and <80% predicted were randomized to single oral dose of imidafenacin 0.1 mg, imidafenacin 0.2 mg, or placebo.

Results

Maximum change in FEV₁ with both doses of imidafenacin significantly improved from baseline to 24 hrs after administration when compared with a placebo. Area under the curve in FEV₁ during 24 hrs after administration with 0.2 mg, but not 0.1 mg dose, was significantly improved when compared with a placebo, and the improvement was significantly based on dose-dependent manners. Plasma imidafenacin level was positively correlated with change in FEV₁. All subjects with both doses of imidafenacin completed without moderate nor severe adverse events.

Conclusion

A single oral dose of imidafenacin 0.1 mg or imidafenacin 0.2 mg may contribute to the improvement of pulmonary function with excellent safety and tolerability in patients with COPD.

Trial registration

JapicCTI-121760 (Japan Pharmaceutical Information Center – Clinical Trials Information [JapicCTI]; http://www.clinicaltrials.jp/user/cteSearch_e.jsp).

Novel Extended-Release Multiple-Unit System of Imidafenacin Prepared by Fluid-Bed Coating Technique

The objective of this study was to formulate once-a-day extended-release (ER) pellet system of imidafenacin (IDN), a recently approved urinary antispasmodic agent with twice-a-day dosing regimen. The sugar sphere pellets were firstly layered with IDN and hypromellose and then coated with Eudragit RS (copolymers of acrylic and methacrylic acid esters), employed as a release modifier, using a fluid-bed coater. Solid-state characterizations using solid-state X-ray diffraction and differential scanning calorimeter indicated that the antispasmodic agent was homogeneously layered onto the pellets in an amorphous state. Drug release from multiple-unit ER system was effectively retarded in proportion to the amount of Eudragit RS in the outer layer, with a high correlation value above 0.86. In a pharmacokinetic evaluation in beagle dogs, the plasma concentration profile of IDN was markedly protracted by ER pellets, exhibiting delayed the time needed to reach the maximum drug concentration and the elimination half-life in plasma, compared to the commercial immediate release form (Uritos® tablet, Kyorin Pharmaceutical Co., Ltd., Japan). Therefore, the novel ER pellets can be a promising tool for oral IDN therapy, providing a once-a-day dosing regimen, and thus, improving patient compliance.

Imidafenacin exerts the antidiuretic effect by enhancing vasopressin-related responses in orally water-loaded rats

Imidafenacin, an antimuscarinic agent for treating overactive bladder, has an antidiuretic effect, but the detailed mechanisms of action remain unclear. The cholinergic and vasopressin systems are known to interact, for example, in the suppression of vasopressin-induced water reabsorption through muscarinic stimulation in the renal collecting duct. We, therefore, investigated whether vasopressin signaling pathway would participate in the antidiuretic effect of imidafenacin. In female Sprague-Dawley rats, urine production was measured by collecting urine from cystostomy chatheter using a Bollman restraining cage for 2h after drug i.v. injection and water load (25ml/kg p.o.). Both imidafenacin and a vasopressin V₂ receptor agonist desmopressin acetate (desmopressin) dose-dependently suppressed urine production. The combination of imidafenacin and desmopressin at the minimum effective doses suppressed the urine production more strongly than each alone. Mozavaptan hydrochloride (mozavaptan, 3mg/kg), a vasopressin V₂ receptor antagonist, completely inhibited the antidiuretic effects of imidafenacin and desmopressin at their respective minimum effective doses. The antidiuretic effect of desmopressin emerged at the maximum antidiuretic dose level (0.1µg/kg) even under mozavaptan-treatment, whereas that of imidafenacin (300µg/kg) was still kept suppressed by mozavaptan. When 300µg/kg imidafenacin was added to the combination of mozavaptan 3mg/kg and desmopressin 0.1µg/kg, the antidiuretic effect was further enhanced. The present study suggests that vasopressin signaling pathway participates in the antidiuretic effect of imidafenacin, and that imidafenacin exerts its antidiuretic effects by enhancing some part of the vasopressin signaling pathway in orally water-loaded rats.

Characterization of muscarinic receptor binding by the novel radioligand, [(3)H]imidafenacin, in the bladder and other tissues of rats

The present study aimed to directly characterize specific binding sites of tritium ([(3)H])-labeled imidafenacin, a new radioligand for labeling muscarinic receptors, in the bladder and other peripheral or central nervous tissues of rats. Muscarinic receptors in rat tissues were measured by radioligand binding assay using [(3)H]imidafenacin. Specific [(3)H]imidafenacin binding in rat tissues was saturable, reversible, and of high affinity. Estimated dissociation constants (Kd values) were significantly lower in submaxillary gland and prostate and higher in heart than in bladder, indicating lower Kd values in M1 and M3 subtype- than M2 subtype-dominating tissues. Unlabeled imidafenacin and clinically used antimuscarinic agents competed with [(3)H]imidafenacin for binding sites in bladder and other tissues in a concentration-dependent manner, which indicated pharmacological specificity of [(3)H]imidafenacin binding sites. Pretreatment with N-(2-chloroethyl)-4-piperidinyl diphenylacetate (4-DAMP mustard), an irreversible inactivating agent of M3 subtype, significantly decreased the number of [(3)H]imidafenacin binding sites in bladder, submaxillary gland, and colon, but not in heart. [(3)H]imidafenacin labeled muscarinic receptors in M1 and M3 subtype-dominating tissues with higher affinity than [N-methyl-(3)H]scopolamine methyl chloride (NMS). [(3)H]imidafenacin is a useful radioligand to label muscarinic receptors in M1- and M3-dominating tissues with high affinity.

Comprehensive Health-Related Quality of Life is Influenced by Nocturia and Sleep Disturbance: Investigation Based on the SF-8

We investigated the influence of nocturia and sleep disturbance on health-related quality of life(HRQOL) using the Medical Outcomes Study 8-item Short Form Health Survey (SF-8) in patients with nocturia. We also assessed the effect of therapeutic intervention by means of an anticholinergic agent on the results of the SF-8. One hundred and eighty-four patients who voided at least once per night were surveyed using the SF-8, Overactive Bladder Symptom Score (OABSS), Pittsburgh Sleep Quality Index (PSQI), and Epworth Sleepiness Scale (ESS). These parameters were also evaluated before and after 12 weeks of imidafenacin treatment in 51 patients with OAB accompanied by nocturia. The SF-8 physical component summary score (PCS) showed a significant decrease as nighttime voiding frequency increased. The mental health component summary score was 47.1 and 47.6 (which were lower than the standard value of 50) in the group with a nighttime frequency of once and ≥3/night, respectively. The SF-8 PCS and 6 subscales were negatively associated with nighttime voiding frequency, while the PSQI global score was positively associated with it. Imidafenacin significantly improved the OABSS, PSQI, and ESS, as well as the SF-8 score. This is the first study using the SF-8 to show that nocturia and sleep disturbance have a major influence on comprehensive HRQOL and that the SF-8 can be used to monitor HRQOL in OAB patients receiving treatment for nocturia.

Emerging drugs for overactive bladder

INTRODUCTION

Overactive bladder (OAB) is a common problem which can have disastrous effects on the quality of life of the sufferer. There are established treatments for the problem but they have significant adverse effects. Better drugs and new treatment modalities are necessary to deal with OAB.

AREA COVERED

Antimuscarinics, mirabegron and intravesical injection of botulinum toxin A are established treatments for OAB. Sacral neuromodulation is more invasive but has been successful in treating OAB. Phase II and III trials are in progress for newer β3-agonists and various combinations of antimuscarinics, β3-agonists and antidiuretics. Targeted secretion inhibitors (TSI) can increase efficacy and reduce adverse effects. Liposome integrated botulinum toxin A has an advantage of effective administration by intravesical instillation. Both medicines are in Phase II trials. Many other drugs which have promising results are discussed.

EXPERT OPINION

Newer antimuscarinics have better tolerability. Long-term data for mirabegron has shown that it is more effective in severe OAB. Combination drugs may prove to be more effective with less adverse effects. Emerging treatments with TSI, lipotoxin and gene therapy appear promising.

Mirabegron in the treatment of overactive bladder

INTRODUCTION

Mirabegron is a selective β3-adrenergic receptor agonist recently developed for the treatment of patients with overactive bladder (OAB), which offers an alternative pharmacological option to the well-established treatment with antimuscarinics (AMs).

AREAS COVERED

This review offers an explanation of the mechanism of action, of the pharmacokinetics and pharmacodynamics of mirabegron and gives readers a complete overview of Phase II and III studies on the clinical efficacy, tolerability and safety of this agent in the setting of OAB treatment.

EXPERT OPINION

Both Phase II and III trials have shown that mirabegron is efficacious and safe in treating patients with OAB. Future research should focus on the assessment of mirabegron concentrations in the CNS and on the evaluation of the potential of the combination of mirabegron with AMs. Another field for future research is represented by the investigation of the interaction of mirabegron with CYP2D6 inhibitors. Furthermore, current literature completely lacks studies on the efficacy and safety of mirabegron in the pediatric population and such trials are awaited.

Add-on anticholinergic therapy for residual nocturia in patients with lower urinary tract symptoms receiving α1-blocker treatment: a multi-centre, prospective, randomised study

PURPOSE

To evaluate the efficacy and safety of imidafenacin (IM), a novel short half-life anticholinergic, as add-on therapy for male LUTS with nocturia and nocturnal polyuria.

MATERIALS AND METHODS

This multicenter, prospective, randomized, open-labelled study was conducted and involved men who had frequency, urgency, and nocturia despite receiving a stable dose of α1-blocker for ≥1 month. Subjects were randomised to control (α1-blocker alone), IM twice/day (α1-blocker +0.1 mg imidafenacin twice daily), or IM nightly (α1-blocker plus 0.1 mg imidafenacin nightly) group; the treatment period was 8 weeks. Primary endpoints included improvements in night-time frequency and Nocturia Quality of Life Questionnaire (N-QOL) scores. Secondary endpoints included changes from the baseline in frequency volume chart variables, and post-void residual volume.

RESULTS AND LIMITATIONS

Compared with the controls, IM twice/day and IM nightly patients had a significantly lower night-time frequency (changes from baseline: 0.1 ± 0.8 in control, -0.6 ± 0.9 in IM twice/day, and -0.4 ± 1.0 in IM nightly, p = 0.5227, 0.0006 and 0.0143, respectively). The hours of undisturbed sleep and N-QOL score were significantly improved in IM twice/day group, though not IM nightly group. Nocturnal urine volume was significantly reduced in IM nightly group, although total urine volume remained unchanged.

CONCLUSIONS

A short half-life anticholinergic is suggested to be safe and effective as an add-on therapy for residual nocturia in patients with male LUTS receiving α1-blocker treatment. Anticholinergic administration nightly could reduce the nocturnal urine volume.

Muscarinic receptors mediate cold stress-induced detrusor overactivity in type 2 diabetes mellitus rats

OBJECTIVES

This study determined if muscarinic receptors could mediate the cold stress-induced detrusor overactivity induced in type 2 diabetes mellitus rats.

METHODS

Ten-week-old female Goto-Kakizaki diabetic rats (n = 12) and Wister Kyoto non-diabetic rats (n = 12) were maintained on a high-fat diet for 4 weeks. Cystometric investigations of the unanesthetized rats were carried out at room temperature (27 ± 2°C) for 20 min. They were intravenously administered imidafenacin (0.3 mg/kg, n = 6) or vehicle (n = 6). After 5 min, the rats were transferred to a low temperature (4 ± 2°C) for 40 min where the cystometry was continued. The rats were then returned to room temperature for the final cystometric measurements. Afterwards, expressions of bladder muscarinic receptor M3 and M2 messenger ribonucleic acids and proteins were assessed by reverse transcription polymerase chain reaction and immunohistochemistry.

RESULTS

In non-diabetic Wister Kyoto rats, imidafenacin did not reduce cold stress-induced detrusor overactivity. In diabetic Goto-Kakizaki rats, just after transfer to a low temperature, the cold stress-induced detrusor overactivity in imidafenacin-treated rats was reduced compared with vehicle-treated rats. Within the urinary bladders, the ratio of M3 to M2 receptor messenger ribonucleic acid in the diabetic Goto-Kakizaki rats was significantly higher than that of the non-diabetic Wister Kyoto rats. The proportion of muscarinic M3 receptor-positive area within the detrusor in diabetic Goto-Kakizaki rats was also significantly higher than that in non-diabetic Wister Kyoto rats.

CONCLUSIONS

Imidafenacin partially inhibits cold stress-induced detrusor overactivity in diabetic Goto-Kakizaki rats. In this animal model, muscarinic M3 receptors partially mediate cold stress-induced detrusor overactivity.

Future therapies: Early trials and basic science

Pharmacotherapeutic options for overactive bladder (OAB) include antimuscarinics and the beta3-adrenoceptor agonist mirabegron. Research and development of novel therapeutic options for OAB continues to be an active field. This review summarizes recent research with the existing therapies as well as the most promising agents in development.

New therapies in the treatment of overactive bladder

INTRODUCTION

Overactive bladder (OAB) is a common condition which affects both men and women across many age groups with significant impact on quality of life. There is currently an armamentarium of treatment options available ranging from conservative, medical therapy to radical surgeries. Increasing understanding of OAB is resulting in the rapid development of new therapies today.

AREAS COVERED

The purpose of this article was to summarise the latest developments in non-neurogenic OAB treatment, discuss the evidence and results of current and new treatment modalities available through review of published data and results presented at recent international meetings.

EXPERT OPINION

The ultimate goal in OAB therapy is to provide good clinical efficacy, safe, non-invasive and easy to administer. There is definitely room for development of new therapies in OAB and current progress is encouraging.