Long-term safety and efficacy of antimuscarinic add-on therapy in patients with overactive bladder who had a suboptimal response to mirabegron monotherapy: A multicenter, randomized study in Japan (MILAI II study)

Mirabegron in the Management of Overactive Bladder Syndrome

Overactive bladder (OAB) negatively affects work productivity and quality of life in sufferers. Its overall impact is likely to increase as a result of increasing prevalence in an ageing population. The pathophysiology of OAB is not completely understood but the β3-adrenoceptor, which is highly expressed in the urinary bladder, is thought to be important for mediating human detrusor relaxation during the storage phase. Clinical trial results have demonstrated that mirabegron, a selective β3-adrenoceptor agonist offers substantial clinical efficacy and good adherence rates over 12 months. Furthermore, due to its different mechanism of action, it is likely to offer a favourable tolerability profile when compared with antimuscarinic agents, resulting in improved persistence over long-term treatment. Finally, from a health economic perspective, despite its higher drug acquisition cost, mirabegron has been found to be cost-effective, owing to the greater increase in quality-adjusted-life-years gained, when compared to antimuscarinic medications. The PubMed database was searched for English language articles published between 1 January 2005 to 31 January 2022, on the subject of mirabegron. Search terms included "mirabegron", "overactive bladder", "β3-adrenoceptor agonist", "urinary incontinence". This review summarises the evidence for mirabegron as a treatment option for the management of OAB.

Impact of Mirabegron Administration on the Blood Pressure and Pulse Rate in Patients with Overactive Bladder

Background and Objectives: To determine changes in the blood pressure (BP) and pulse rate (PR) before and after the administration of mirabegron in real-world clinical practice for patients with overactive bladder (OAB). Materials and Methods: This study was conducted in patients newly diagnosed with OAB. Before and 12 weeks after mirabegron treatment, we evaluated the effects on BP and PR. An overall examination was conducted, and the patients were divided into two groups according to their age: a young group (<65 years old) and an old group (≥65 years old). Results: A total of 263 patients were enrolled in this study. In the overall and intragroup comparisons, the systolic BP (SBP) did not change significantly after mirabegron administration. However, an increase in SBP of ≥10 mmHg was observed in 53 (20.2%), 4 (7.4%), and 49 (23.4%) in the entire group, young group, and old group, respectively (p = 0.009). Regarding diastolic BP, a significant decrease after the treatment was detected in entire (71.2 ± 11.4 versus 69.8 ± 10.7 mmHg; p = 0.041) and old patients (71.5 ± 10.6 versus 69.5 ± 10.2 mmHg; p = 0.012). There was no significant change in PR in our study population. Further examination using a propensity match score revealed that age was the risk factor for the increase in SBP after mirabegron administration. Conclusions: Mirabegron does not have any adverse effects on BP and PR. However, since some patients in this study had elevated SBP after administration, we suggest regular BP monitoring during mirabegron treatment.

Utilization rate and long-term persistence of combination pharmacotherapy with β3-agonists and antimuscarinics for overactive bladder refractory to monotherapy in a real-world setting

AIM

To assess real-world treatment profiles, including utilization rate, time to and reasons for discontinuation of combination pharmacotherapy with β₃ -agonists and antimuscarinics for refractory overactive bladder (OAB) through a retrospective chart review.

METHODS

We retrospectively reviewed the records of OAB patients who received β₃ -agonists or antimuscarinics at our hospital between 2012 and 2020 and analyzed the clinical course of patients who progressed to combination therapy. Data on age, sex, major complaints, OAB symptom score at the initiation of combination therapy, treatment persistence, and reasons for discontinuation were collected. Treatment persistence was assessed with respect to the median time to discontinuation and persistence rate at 12 months.

RESULTS

Of the 2163 patients receiving β₃ -agonists or antimuscarinics, only 84 (3.8%) progressed to combination therapy with both drug classes. At therapy initiation, most (98%) of these patients had moderate to severe OAB symptoms. Median treatment duration and 12-month persistence rate for combination therapy were 595 days and 64.0%, respectively. The reasons for discontinuation were insufficient treatment efficacy followed by adverse effects including voiding impairment in nearly 10% of the patients. None of the baseline parameters was independently associated with persistence in the multivariate analysis.

CONCLUSION

While underutilized among OAB patients refractory to monotherapy, combination pharmacotherapy showed a greater persistence rate than published mirabegron or antimuscarinic monotherapy when applied to patients with moderate to severe symptoms. Treatment-emergent voiding impairment is a concern associated with this mode of therapy. A small sample size at a single institution is the limitation of this study.

Comparative study of different combinations of mirabegron and antimuscarinics in treatment for overactive bladder syndrome in elderly patients

Objectives

To compare the therapeutic efficacy, adverse events (AEs), and patient preference in elderly patients with overactive bladder (OAB) receiving different combinations of mirabegron and solifenacin.

Materials and Methods

Elderly OAB patients received mirabegron 25 mg (M25) daily for 1 month (1M) followed by randomization to receive M25 (Group 1), mirabegron 50 mg (M50, Group 2), solifenacin 5 mg (S5, group 3); or M25 plus S5 (Group 4) for further 2 months. Efficacy and AEs were evaluated. At the end of 3M, patients' preferred option for future treatment was investigated.

Results

A total of 168 patients were enrolled, and 100 completed 3-month treatment. At 1M, all parameters improved significantly except postvoid residual (PVR), 23 (13.7%) patients had no symptom, 16 (9.5%) had no improvement, and 10 (6.0%) withdrew from the trial. Compared parameters at 3M with 1M revealed that quality of life, Patient's Perception of Bladder Condition scores, and voided volume improved significantly in group 1; the OAB Symptom Score (OABSS) increased in group 2; mean PVR and Global Response Assessment (GRA) deteriorated in group 3; and the OABSS and GRA improved in group 4. At 3M, the AEs prevalence increased significantly in group 3. Only 38.1% in group 4 preferred long-term usage of combination therapy.

Conclusion

M25 daily is effective and safe in treating elderly OAB patients. Dose escalation to 50 mg or shifting to S5 does not increase the therapeutic efficacy. Combining M25 with S5 provides better treatment efficacy but is associated with lower patient compliance than M25 alone.

Current pharmacotherapy of overactive bladder

Overactive bladder is a symptom complex consisting of bothersome storage urinary symptoms that is highly prevalent among both sexes and has a significant impact on quality of life. Various antimuscarinic agents and the beta-3 agonists mirabegron and vibegron are currently available for the treatment of OAB. Each drug has specific pharmacologic properties, dosing schedule and tolerability profile, making it essential to individualize the medical treatment for the patient's characteristics and expectations. In this manuscript, we review the most important factors involved in the contemporary pharmacological treatment of OAB.

Association between overactive bladder and pelvic organ mobility as evaluated by dynamic magnetic resonance imaging

Overactive bladder (OAB) is a prevalent condition, which negatively impacts patients’ quality of life. Pelvic organ prolapse (POP), also prevalent in women, has been recognized as an important etiology of female OAB, although the pathophysiological mechanisms remain controversial. In this study, we reviewed findings of dynamic magnetic resonance imaging (dMRI) in 118 patients with POP and investigated the association between dMRI findings, including positions and mobilities of pelvic organs as well as parameters of pelvic organ support and bladder outlet obstruction (urethral kinking), and OAB in order to elucidate the pathophysiology of OAB in patients with POP. Our results showed that compared with non-OAB patients, OAB patients had a significantly higher body mass index, more severe pelvic floor muscle impairment, and more profound supportive defects in the uterine cervix (apical compartment). On the other hand, dMRI parameters showed hardly any significant difference between patients with mild and moderate to severe OAB. These findings may imply that levator ani impairment and defective supports of the apical compartment could be associated with the presence of OAB and that the severity of OAB could be affected by factors other than those related to pelvic organ mobility and support or urethral kinking.

Possible Involvement of Muscarinic Receptor Blockade in Mirabegron Therapy for Patients with Overactive Bladder

The selective β ₃-adrenoceptor agonist mirabegron, an established alternative to antimuscarinic therapy for patients with overactive bladder, induces additional effects against receptors, transporters, and hepatic enzymes. The present study aimed to elucidate the effects of mirabegron on muscarinic receptors in the rat bladder using radioligand binding and functional assays. Mirabegron (0.1-100 μM) inhibited specific [N-methyl-³H]scopolamine methyl chloride binding in the bladder and other tissues of rats in a concentration-dependent manner. Binding affinity in the bladder was similar to that in the heart and significantly higher than those in the submaxillary gland and brain. Mirabegron induced the concentration-dependent relaxation of carbachol-induced contractions in the rat isolated bladder. Further analyses using a two-site model revealed that the relative quantities of high- and low-affinity components for mirabegron were 44.5% and 55.5%, respectively. Respective pEC₅₀ values were 7.06 and 4.97. Based on the receptor binding affinity and pharmacokinetics of mirabegron, muscarinic receptor occupancy in the human bladder for 24 hours after the administration of a single oral dose of 50 mg mirabegron was 37%-76%. The present results demonstrate for the first time that mirabegron may relax the detrusor smooth muscle not only by β ₃-adrenoceptor activation but also muscarinic receptor blockade. SIGNIFICANCE STATEMENT: Mirabegron, the first selective β ₃-adrenoceptor agonist, represents an alternative to antimuscarinic agents for management of overactive bladder (OAB). The present study aimed to clarify whether mirabegron directly binds to muscarinic receptors and affects cholinergic agonist-induced contractions in rat urinary bladder and to predict muscarinic receptor occupancy in human bladder after oral administration of mirabegron. The results demonstrated that mirabegron therapy for patients with OAB may be due not only to β ₃-adrenoceptor activation but also muscarinic receptor blockade.

Clinical Guidelines for Female Lower Urinary Tract Symptoms (second edition)

The present article is an abridged English translation of the Japanese Clinical Guidelines for Female Lower Urinary Tract Symptoms (second edition), published in September 2019. These guidelines consist of a total of 212 pages and are unique worldwide in that they cover female lower urinary tract symptoms other than urinary incontinence. They contain two algorithms for "primary treatment" and "specialized treatment," respectively. These guidelines, consisting of six chapters, address a total of 26 clinical questions including: (i) treatment algorithms; (ii) what are female lower urinary tract symptoms?; (iii) epidemiology and quality of life; (iv) pathology and illness; (v) diagnosis; and (vi) treatment. When the patient's symptoms mainly involve voiding and post-micturition symptoms, specialized treatment should be considered. In the event of voiding symptoms concurrent with storage symptoms, residual urine should be measured; if the residual urine volume is <100 mL, then diagnosis and treatment for storage symptoms is prioritized, and if the volume is ≥100 mL, then specialized treatment should be considered. When storage symptoms are the primary condition, then the patient is subject to the primary treatment algorithm. Specialized treatment for refractory overactive bladder includes botulinum toxin injection and sacral nerve stimulation. For stress urinary incontinence, surgical treatment is indicated, such as urethral slings. The two causes of voiding symptoms and post-micturition symptoms are lower urinary tract obstruction and detrusor underactivity (underactive bladder). Mechanical lower urinary tract obstruction, such as pelvic organ prolapse, is expected to improve with surgery.

Treatment of Non-neurogenic Lower Urinary Tract Symptoms-A Review of Key Publications from 2018 Onward

CONTEXT

A considerable number of studies addressing the management of lower urinary tract symptoms (LUTS) have been published since 2018.

OBJECTIVE

To review the key studies involving pharmacological and neuromodulation treatment of LUTS published from 2018 onward.

EVIDENCE ACQUISITION

We followed the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) statement. We conducted an Embase/PubMed search of English literature with the words "OAB" or "LUTS" matched with several different treatment modalities. The search ranged between January 2018 and January 2020. All retrieved papers were first reviewed by title and abstract, yielding a total of 236 papers. Additional manuscripts, such as those presented at major meetings, were also included. After revision, 46 publications were included.

EVIDENCE SYNTHESIS

Papers on β3-adrenoreceptor agonists were most abundant. The efficacy and safety of mirabegron in monotherapy and combination therapy were further confirmed by large observational studies and randomized control trials, including one carried out in elderly patients. The use of vibegron for overactive bladder (OAB) was effective and safe in pivotal clinical trials. More database analyses confirm the risk of dementia associated with long-term use of anticholinergics. Onabotulinum toxinA (OnabotA) and sacral neuromodulation provided similar improvement for incontinence in OAB patients at a 2-yr follow-up. Retrospective studies show that OnabotA is effective in men with OAB. New subcutaneous or transcutaneous devices for tibial nerve stimulation were investigated. The potential role of gene therapy in LUTS was assessed in a pilot study.

CONCLUSIONS

Important progresses occurred in the pharmacological and neuromodulation treatments of LUTS, which may change clinical practice. Inoculation of gene vectors was investigated for the first time.

PATIENT SUMMARY

The investigation in the therapeutic field of lower urinary tract symptoms is active. The search for the best option for each patient continues. This systematic review summarizes the findings of the most recent and relevant studies in the field.

Pharmacology of the lower urinary tract: update on LUTS treatment

The number of compounds used in the pharmacological treatment of lower urinary tract symptoms (LUTS) of patients who do not respond to conservative measures has been relatively stable during the last decade, with the exception of the introduction of the new class of β3 adrenoceptor agonists. However, different combinations have been investigated, and the long-term use of these compounds has raised new concerns about adherence and safety. This review summarizes the current state of pharmacology for LUTS, and presents a thorough discussion of the possible challenges concerning their future use. In this narrative review, we analyze the most recent articles related to LUTS pharmacotherapy, after an initial review of mechanisms of bladder function relevant in present clinical practice. The main problems with pharmacotherapy in LUTS are associated with its moderate efficacy, low persistence on treatment, and the incidence of short- and long-term adverse events (AE) associated with some compounds. The long-term AE, such as cognitive impairment in the elderly vulnerable patients associated with antimuscarinic drugs or persistent erectile dysfunction in sexually active men after treatment with 5-α-reductase inhibitors (5-ARI), are some of the problems addressed in this review. Combination therapy taking advantage of the synergistic mechanisms of action between some classes of compounds may overcome AE associated with dose escalation. LUTS pharmacotherapy offers moderate results to most patients but not a full cure. The use of combination drugs to achieve better clinical results, reduce AE and improve both efficacy and adherence, will be used more frequently in the future. The recently raised concern on potential long-term irreversible AE associated with some of these drugs, like antimuscarinics and 5-ARI, are critically important and require further investigation.

Effects of combined treatment with fesoterodine and mirabegron in a pelvic congestion rat model: Results from in vitro and in vivo functional studies

Objectives

To examine the effect of combining a nonselective muscarinic receptor antagonist, 5‐hydroxymethyl tolterodine (an active metabolite of fesoterodine), with a β3 adrenoceptor agonist, mirabegron, in a rat model of pelvic congestion.

Methods

The rat pelvic congestion model used female Sprague‐Dawley rats with their bilateral common iliac and uterine veins ligated. Expressions of M2 and M3 receptor subtypes in the urothelium and detrusor were detected by real‐time polymerase chain reaction assays. The effects of both drugs were investigated on isolated bladder strips contracted by electrical field stimulation. in vivo single cystometry was used to assess the effects of 5‐hydroxymethyl tolterodine and mirabegron independently or in combination on bladder capacity, micturition pressure, and threshold pressure.

Results

Pelvic congestion rats showed decreased bladder capacity compared with controls, but micturition pressure and threshold pressure were unchanged. Pelvic congestion model rats also demonstrated an approximately two‐fold increase in expression of both M2 and M3 receptor subtypes in the urothelium. Additive relaxant effects of 5‐hydroxymethyl tolterodine and mirabegron were observed in vitro in the electrical field stimulation‐induced contractions of bladder strips from pelvic congestion rats. In vivo, bladder capacity was increased significantly by a combination of 5‐hydroxymethyl tolterodine and mirabegron, with the combined effect exceeding the sum of the effects of monotherapies. Micturition pressure and threshold pressure did not significantly differ between groups.

Conclusions

The combination of 5‐hydroxymethyl tolterodine with mirabegron suggests the potential of synergistic effects in a rat pelvic congestion model.

Cardiovascular safety of antimuscarinic add-on therapy in patients with overactive bladder who had a suboptimal response to mirabegron monotherapy: A post hoc analysis from the Japanese MILAI II study

Objective

This analysis was conducted to investigate the cardiovascular (CV) safety outcomes from the MILAI II study. MILAI II was conducted to evaluate the long‐term safety and efficacy of antimuscarinic add‐on therapy to mirabegron over 52 weeks in patients with overactive bladder (OAB) symptoms.

Methods

MILAI II consisted of a 2‐week screening period (patients received mirabegron 50 mg once daily) plus a 52‐week treatment period (patients were randomized to receive a combination of mirabegron 50 mg/d plus solifenacin 5 mg/d, propiverine 20 mg/d, imidafenacin 0.2 mg/d, or tolterodine 4 mg/d). CV safety was assessed using treatment‐emergent adverse events (TEAEs), vital signs, and 12‐lead electrocardiograms (ECGs). Vital signs and ECG data were evaluated for each patient using worst post‐baseline values reported.

Results

Of 647 patients, 570 (88.1%) were female with a mean age of 65 years. CV history at baseline and CV‐related concomitant medication use throughout the study were balanced between groups. The incidences of overall and drug‐related CV TEAEs were ≤8.1% and ≤6.2%, respectively, for all groups. The most common TEAEs were ECG T wave amplitude decreased, ECG QT prolonged, and ventricular extrasystoles. Overall, 36 TEAEs of interest related to the CV system that were possibly/probably related to treatment were reported with similar incidences for each group. For the worst post‐baseline vital signs and ECGs, no relationships were noted in terms of either timing or treatment group.

Conclusion

A favorable CV safety profile was observed following long‐term combination treatment with mirabegron and an antimuscarinic in patients with OAB symptoms.