Clinical use of the β3 adrenoceptor agonist mirabegron in patients with overactive bladder syndrome

Inside the Biology of the β3-Adrenoceptor

Since the first discovery in 1989, the β3-adrenoceptor (β3-AR) has gained great attention because it showed the ability to regulate many physiologic and metabolic activities, such as thermogenesis and lipolysis in brown and white adipose tissue, respectively (BAT, WAT), negative inotropic effects in cardiomyocytes, and relaxation of the blood vessels and the urinary bladder. The β3-AR has been suggested as a potential target for cancer treatment, both in adult and pediatric tumors, since under hypoxia its upregulation in the tumor microenvironment (TME) regulates stromal cell differentiation, tumor growth and metastases, signifying that its agonism/antagonism could be useful for clinical benefits. Promising results in cancer research have proposed the β3-AR being targeted for the treatment of many conditions, with some drugs, at present, undergoing phase II and III clinical trials. In this review, we report the scientific journey followed by the research from the β3-Ars' discovery, with focus on the β3-Ars' role in cancer initiation and progression that elects it an intriguing target for novel antineoplastic approaches. The overview highlights the great potential of the β3-AR, both in physiologic and pathologic conditions, with the intention to display the possible benefits of β3-AR modulation in cancer reality.

Repurposing the β3-Adrenergic Receptor Agonist Mirabegron in Patients With Structural Cardiac Disease: The Beta3-LVH Phase 2b Randomized Clinical Trial

Importance

Left ventricular (LV) hypertrophy contributes to the onset and progression of heart failure (HF), particularly for patients with pre-HF (stage B) for whom no treatment has yet proven effective to prevent transition to overt HF (stage C). The β3-adrenergic receptors (β3ARs) may represent a new target, as their activation attenuates LV remodeling.

Objective

To determine whether activation of β3ARs by repurposing a β3AR agonist, mirabegron, is safe and effective in preventing progression of LV hypertrophy and diastolic dysfunction among patients with pre- or mild HF.

Design, Setting, and Participants

The Beta3-LVH prospective, triple-blind, placebo-controlled phase 2b randomized clinical trial enrolled patients between September 12, 2016, and February 26, 2021, with a follow-up of 12 months. The trial was conducted at 10 academic hospitals in 8 countries across Europe (Germany, Poland, France, Belgium, Italy, Portugal, Greece, and the UK). Patients aged 18 years or older with or without HF symptoms (maximum New York Heart Association class II) were screened for the presence of LV hypertrophy (increased LV mass index [LVMI] of ≥95 g/m2 for women or ≥115 g/m2 for men) or maximum wall thickness of 13 mm or greater using echocardiography. Data analysis was performed in August 2022.

Intervention

Participants were randomly assigned (1:1) to mirabegron (50 mg/d) or placebo, stratified by the presence of atrial fibrillation and/or type 2 diabetes, for 12 months.

Main Outcomes and Measures

The primary end points were LVMI determined using cardiac magnetic resonance imaging and LV diastolic function (early diastolic tissue Doppler velocity [E/e'] ratio assessed using Doppler echocardiography) at 12 months. Patients with at least 1 valid measurement of either primary end point were included in the primary analysis. Safety was assessed for all patients who received at least 1 dose of study medication.

Results

Of the 380 patients screened, 296 were enrolled in the trial. There were 147 patients randomized to mirabegron (116 men [79%]; mean [SD] age, 64.0 [10.2] years) and 149 to placebo (112 men [75%]; mean [SD] age, 62.2 [10.9] years). All patients were included in the primary intention-to-treat analysis. At 12 months, the baseline and covariate-adjusted differences between groups included a 1.3-g/m2 increase in LVMI (95% CI, -0.15 to 2.74; P = .08) and a -0.15 decrease in E/e' (95% CI, -0.69 to 0.4; P = .60). A total of 213 adverse events (AEs) occurred in 82 mirabegron-treated patients (including 31 serious AEs in 19 patients) and 215 AEs occurred in 88 placebo-treated patients (including 30 serious AEs in 22 patients). No deaths occurred during the trial.

Conclusions

In this study, mirabegron therapy had a neutral effect on LV mass or diastolic function over 12 months among patients who had structural heart disease with no or mild HF symptoms.

Trial Registration

ClinicalTrials.gov Identifier: NCT02599480.

Intermittent Hypoxia and Atherosclerosis: From Molecular Mechanisms to the Therapeutic Treatment

Intermittent hypoxia (IH) has a dual nature. On the one hand, chronic IH (CIH) is an important pathologic feature of obstructive sleep apnea (OSA) syndrome (OSAS), and many studies have confirmed that OSA-related CIH (OSA-CIH) has atherogenic effects involving complex and interacting mechanisms. Limited preventive and treatment methods are currently available for this condition. On the other hand, non-OSA-related IH has beneficial or detrimental effects on the body, depending on the degree, duration, and cyclic cycle of hypoxia. It includes two main states: intermittent hypoxia in a simulated plateau environment and intermittent hypoxia in a normobaric environment. In this paper, we compare the two types of IH and summarizes the pathologic mechanisms and research advances in the treatment of OSA-CIH-induced atherosclerosis (AS), to provide evidence for the systematic prevention and treatment of OSAS-related AS.

Discovery and characterization of a potent activator of the BKCa channel that relives overactive bladder syndrome in rats

The large-conductance Ca²⁺-activated K⁺ channel (BK_Ca channel) is involved in repolarizing the membrane potential and has a variety of cellular functions. The BK_Ca channel is highly expressed in bladder smooth muscle and mediates muscle relaxation. Compounds that activate the BK_Ca channel have therapeutic potential against pathological symptoms associated with the overactivity of bladder smooth muscle. In this regard, we screened a chemical library of 9938 compounds to identify novel BK_Ca channel activators. A cell-based fluorescence assay identified a structural family of compounds containing a common tricyclic quinazoline ring that activated the BK_Ca channel. The most potent compound TTQC-1 (7-bromo-N-(3-methylphenyl)-5-oxo-1-thioxo-4,5-dihydro[1,3]thiazolo[3,4-a]quinazoline-3-carboxamide) directly and reversibly activated the macroscopic current of BK_Ca channels expressed in Xenopus oocytes from both sides of the cellular membrane. TTQC-1 increased the maximum conductance and shifted the half activation voltage to the left. The apparent half-maximal effective concentration and dissociation constant were 2.8 μM and 7.95 μM, respectively. TTQC-1 delayed the kinetics of channel deactivation without affecting channel activation. The activation effects were observed over a wide range of intracellular Ca²⁺ concentrations and dependent on the co-expression of β1 and β4 auxiliary subunits, which are highly expressed in urinary bladder. In the isolated smooth muscle cells of rat urinary bladder, TTQC-1 increased the K⁺ currents which can be blocked by iberiotoxin. Finally, oral administration of TTQC-1 to hypertensive rats decreased the urination frequency. Therefore, TTQC-1 is a BK_Ca channel activator with a novel structure that is a potential therapeutic candidate for BK_Ca channel-related diseases, such as overactive bladder syndrome.

HIF-1-Dependent Induction of β3 Adrenoceptor: Evidence from the Mouse Retina

A major player in the homeostatic response to hypoxia is the hypoxia-inducible factor (HIF)-1 that transactivates a number of genes involved in neovessel proliferation in response to low oxygen tension. In the retina, hypoxia overstimulates β-adrenoceptors (β-ARs) which play a key role in the formation of pathogenic blood vessels. Among β-ARs, β3-AR expression is increased in proliferating vessels in concomitance with increased levels of HIF-1α and vascular endothelial growth factor (VEGF). Whether, similarly to VEGF, hypoxia-induced β3-AR upregulation is driven by HIF-1 is still unknown. We used the mouse model of oxygen-induced retinopathy (OIR), an acknowledged model of retinal angiogenesis, to verify the hypothesis of β3-AR transcriptional regulation by HIF-1. Investigation of β3-AR regulation over OIR progression revealed that the expression profile of β3-AR depends on oxygen tension, similar to VEGF. The additional evidence that HIF-1α stabilization decouples β3-AR expression from oxygen levels further indicates that HIF-1 regulates the expression of the β3-AR gene in the retina. Bioinformatics predicted the presence of six HIF-1 binding sites (HBS #1-6) upstream and inside the mouse β3-AR gene. Among these, HBS #1 has been identified as the most suitable HBS for HIF-1 binding. Chromatin immunoprecipitation-qPCR demonstrated an effective binding of HIF-1 to HBS #1 indicating the existence of a physical interaction between HIF-1 and the β3-AR gene. The additional finding that β3-AR gene expression is concomitantly activated indicates the possibility that HIF-1 transactivates the β3-AR gene. Our results are indicative of β3-AR involvement in HIF-1-mediated response to hypoxia.

Mirabegron Ameliorated Atherosclerosis of ApoE-/- Mice in Chronic Intermittent Hypoxia but Not in Normoxia

PURPOSE

It has been established that obstructive sleep apnea (OSA) is an independent risk factor for atherosclerosis. Chronic intermittent hypoxia (CIH) activates sympathoadrenal system and upregulates β3 adrenergic receptor (β3 AR). However, the effect of selective β3 AR agonist mirabegron in CIH-induced atherosclerosis remains unknown.

METHODS

We generated a CIH-induced atherosclerosis model through exposing ApoE^-/- mice to CIH (8 h per day, cyclic inspiratory oxygen fraction 5-21%, 60-s cycle) for 6 weeks after 4-week high-fat dieting and investigated the effects of mirabegron, a selective β3 AR agonist, on CIH-induced atherosclerosis. The coronary endarterectomy (CE) specimens from coronary artery disease patients with OSA and without OSA were collected.

RESULTS

The expression of β3 AR was significantly elevated in CIH-induced atherosclerosis model. Furthermore, treatment with mirabegron (10mg/kg per day by oral administration for 6 weeks) ameliorated atherosclerosis in ApoE^-/- mice in CIH but not in normoxia. Mechanistically, mirabegron activated β3 AR and ameliorated intraplaque oxidative stress by suppressing p22phox expression and reactive oxygen species (ROS) level. In addition, in human CE specimens, β3 AR was also upregulated associated with increased p22phox expression and ROS level both in the lumen and in the plaque of coronary artery in OSA subjects.

CONCLUSION

This study first demonstrated that mirabegron impeded the progression of CIH-induced atherosclerosis, at least in part, via β3 AR-mediated oxidative stress, suggesting a promising therapeutic strategy for protecting against atherosclerosis induced by CIH.

The Beta3 Adrenergic Receptor in Healthy and Pathological Cardiovascular Tissues

The third isotype of beta-adrenoreceptors (β3-AR) has recently come (back) into focus after the observation of its expression in white and beige human adipocytes and its implication in metabolic regulation. This coincides with the recent development and marketing of agonists at the human receptor with superior specificity. Twenty years ago, however, we and others described the expression of β3-AR in human myocardium and its regulation of contractility and cardiac remodeling. Subsequent work from many laboratories has since expanded the characterization of β3-AR involvement in many aspects of cardiovascular physio(patho)logy, justifying the present effort to update current paradigms under the light of the most recent evidence.

Mirabegron, a Clinically Approved β3 Adrenergic Receptor Agonist, Does Not Reduce Infarct Size in a Swine Model of Reperfused Myocardial Infarction

The administration of the selective β3 adrenergic receptor (β3AR) agonist BRL-37344 protects from myocardial ischemia/reperfusion injury (IRI), although the lack of clinical approval limits its translatability. We tested the cardioprotective effect of mirabegron, the first-in-class β3AR agonist approved for human use. A dose-response study was conducted in 6 pigs to select the highest intravenous dose of mirabegron without significant detrimental hemodynamic effect. Subsequently, closed chest anterior myocardial infarction (45 min ischemia followed by reperfusion) was performed in 26 pigs which randomly received either mirabegron (10 μg/kg) or placebo 5 min before reperfusion. Day-7 cardiac magnetic resonance (CMR) showed no differences in infarct size (35.0 ± 2.0% of left ventricle (LV) vs. 35.9 ± 2.4% in mirabegron and placebo respectively, p = 0.782) or LV ejection fraction (36.3 ± 1.1 vs. 34.6 ± 1.9%, p = 0.430). Consistent results were obtained on day-45 CMR. In conclusion, the intravenous administration of the clinically available selective β3AR agonist mirabegron does not reduce infarct size in a swine model of IRI.

Comprehensive review of cardiovascular toxicity of drugs and related agents

Cardiovascular diseases are a leading cause of morbidity and mortality in most developed countries of the world. Pharmaceuticals, illicit drugs, and toxins can significantly contribute to the overall cardiovascular burden and thus deserve attention. The present article is a systematic overview of drugs that may induce distinct cardiovascular toxicity. The compounds are classified into agents that have significant effects on the heart, blood vessels, or both. The mechanism(s) of toxic action are discussed and treatment modalities are briefly mentioned in relevant cases. Due to the large number of clinically relevant compounds discussed, this article could be of interest to a broad audience including pharmacologists and toxicologists, pharmacists, physicians, and medicinal chemists. Particular emphasis is given to clinically relevant topics including the cardiovascular toxicity of illicit sympathomimetic drugs (e.g., cocaine, amphetamines, cathinones), drugs that prolong the QT interval, antidysrhythmic drugs, digoxin and other cardioactive steroids, beta-blockers, calcium channel blockers, female hormones, nonsteroidal anti-inflammatory, and anticancer compounds encompassing anthracyclines and novel targeted therapy interfering with the HER2 or the vascular endothelial growth factor pathway.

Cardiovascular Safety of the β3 -Adrenoceptor Agonist Mirabegron and the Antimuscarinic Agent Solifenacin in the SYNERGY Trial

There have been concerns that treatment of overactive bladder with β₃ -adrenoceptor agonists may potentially have detrimental cardiovascular (CV) side effects. We evaluated the CV safety of mirabegron, a β₃ -adrenoceptor agonist, alone and in combination therapy with the antimuscarinic agent solifenacin. The SYNERGY trial was a multinational, multicenter, randomized, double-blind, parallel-group, placebo and active-controlled phase 3 trial. Patients were randomized to receive solifenacin 5 mg + mirabegron 50 mg (combination 5 + 50 mg), solifenacin 5 mg + mirabegron 25 mg (combination 5 + 25 mg), solifenacin 5 mg monotherapy, mirabegron 25 mg monotherapy, mirabegron 50 mg monotherapy, or placebo for a 12-week double-blind treatment period. A total of 3398 patients were included in the study. Mean changes from baseline to the end of therapy in ECG parameters were similar across treatment groups, although there was an increase in heart rate of 1 beat/minute in the mirabegron treatment groups. There were no clinically meaningful differences in change from baseline in QTcF between monotherapies and placebo and between monotherapies and combination therapy. There were very few major CV events: 1 of 853 (0.1%) with a nonfatal myocardial infarction in the combination 5 + 25 mg group, 2 of 848 (0.2%) with a nonfatal stroke in the combination 5 + 50 mg group, and no events in the other groups. This CV safety analysis of the combination of mirabegron and solifenacin showed rates of CV events comparable with those for monotherapy treatments based on assessments of vital signs, electrocardiograms, and adjudicated CV events.

A strategy utilizing ambulatory monitoring and home and clinic blood pressure measurements to optimize the safety evaluation of noncardiovascular drugs with potential for hemodynamic effects: a report from the SYNERGY trial

Supplemental Digital Content is available in the text.

Objective

The aim of this study was to perform a blood pressure (BP) safety evaluation in patients with an overactive bladder receiving solifenacin (an antimuscarinic agent), mirabegron (a β₃-adrenoceptor agonist), or both compared with placebo in the SYNERGY trial.

Patients and methods

Patients were randomized to receive solifenacin 5 mg+mirabegron 50 mg (combination 5+50 mg); solifenacin 5 mg+mirabegron 25 mg (combination 5+25 mg); solifenacin 5 mg; mirabegron 50 mg; mirabegron 25 mg; or placebo for a double-blind 12-week treatment period. Systolic BP, diastolic BP, and heart rate were measured by ambulatory BP monitoring, and in the clinic or home.

Results

A total of 715 patients were analyzed in an ambulatory BP monitoring substudy. At the end of treatment, ambulatory BP monitoring measurements showed no consistent increases from baseline in the mean 24-h systolic BP or diastolic BP for combination versus monotherapy groups or for monotherapy groups versus placebo. Analysis of 1-h BP averages during the 6 h range that included the T_max values of both study drugs showed no significant BP effects. Shift analysis (switch between different normotension/hypertension stages) did not show differences among the active and placebo groups, nor did outlier analysis of major BP changes differ between placebo and active treatment. Similarly, there were no significant signals in the 24-h heart rate. Office and home measurements were consistent with ambulatory BP monitoring findings.

Conclusions

A paradigm of ambulatory BP monitoring analysis designed to test BP safety of noncardiovascular drugs showed that solifenacin plus mirabegron combination therapy during 12 weeks produced no meaningful changes in BP or heart rate.

Nitric oxide signalling in cardiovascular health and disease

Nitric oxide (NO) signalling has pleiotropic roles in biology and a crucial function in cardiovascular homeostasis. Tremendous knowledge has been accumulated on the mechanisms of the nitric oxide synthase (NOS)-NO pathway, but how this highly reactive, free radical gas signals to specific targets for precise regulation of cardiovascular function remains the focus of much intense research. In this Review, we summarize the updated paradigms on NOS regulation, NO interaction with reactive oxidant species in specific subcellular compartments, and downstream effects of NO in target cardiovascular tissues, while emphasizing the latest developments of molecular tools and biomarkers to modulate and monitor NO production and bioavailability.

Therapeutic efficacy of low-dose (25 mg) mirabegron therapy for patients with mild to moderate overactive bladder symptoms due to central nervous system diseases

OBJECTIVE

The incidence of overactive bladder (OAB) increases with age, especially in patients with central nervous system (CNS) disorders such as cerebrovascular accident (CVA) and Parkinson's disease (PD). Mirabegron is a novel medication for the treatment of OAB. The present study investigated the therapeutic effect of mirabegron on OAB patients with CNS diseases.

METHODS

Patients with CVA, PD, dementia, and OAB symptoms were consecutively enrolled in the study group, and mirabegron 25 mg q.d. was prescribed. Clinical effects, evaluated using the Overactive Bladder Symptom Score (OABSS), Urinary Sensation Scale (USS), International Prostate Symptom Score (IPSS), and Patient Perception of Bladder Condition (PPBC), as well as urodynamic parameters and adverse events were assessed at baseline and 4 and 12 weeks after treatment.

RESULTS

In all, 44 patients (mean [± SD] age 77.7 ± 9.49 years) with OAB due to CVA (n = 27), PD (n = 6), and dementia (n = 11) were included in the present prospective study. Mirabegron resulted in significant improvements in symptom scores on the OABSS (P = .02), USS (P = .009), total IPSS (P = .002), Storage and Voiding domains of the IPSS (P = .001 and .017, respectively), and PPBC (P = .001). No significant changes were noted in post-void residual, maximum flow rate, and voided volume after treatment. Only 5 patients dropped out due to poor therapeutic efficacy and shifted to antimuscarinics. Three patients complained of adverse effects, including dizziness and dysuria. No patient complained of urine retention or constipation.

CONCLUSION

Mirabegron 25 mg once daily effectively decreased urgency symptoms in elderly OAB patients with CNS lesions after the 12-week treatment period. The adverse events were mild and only noted in a few cases.

New and Emerging Therapies and Targets: Beta-3 Agonists

While crucial for the acute physiologic response to stress, the adrenergic system may become maladaptive upon prolonged stimulation in the course of development of heart failure. This has been the basis for the development of beta-blocking therapies, targeting mainly beta1-2 adrenoreceptors (B1-2AR). The third isotype, B3AR, was more recently identified in cardiac myocytes and endothelial cells from human (and many other animal species), where its distinctive coupling to nitric oxide and antioxidant pathways suggested potential protective properties that were unexploited so far. The observation of beneficial effects of B3AR expression/activation on myocardial remodeling and the availability of specific agonists for clinical use now open the way for directly testing the hypothesis in heart failure patients. We will briefly review the specificities of B3AR signaling in the context of the cardiovascular adrenergic system, the evidence supporting its beneficial effects and outline an ongoing clinical trial using the B3AR agonist, mirabegron in patients with/at risk of developing heart failure with preserved ejection fraction (HFpEF).

Structurally Enabled Discovery of Adenosine A2A Receptor Antagonists

Over the past decade there has been a revolution in the field of G protein-coupled receptor (GPCR) structural biology. Many years of innovative research from different areas have come together to fuel this significant change in the fortunes of this field, which for many years was characterized by the paucity of high-resolution structures. The determination to succeed has been in part due to the recognized importance of these proteins as drug targets, and although the pharmaceutical industry has been focusing on these receptors, it can be justifiably argued and demonstrated that many of the approved and commercially successful GPCR drugs can be significantly improved to increase efficacy and/or reduce undesired side effects. In addition, many validated targets in this class remain to be drugged. It is widely recognized that application of structure-based drug design approaches can help medicinal chemists a long way toward discovering better drugs. The achievement of structural biologists in providing high-resolution insight is beginning to transform drug discovery efforts, and there are a number of GPCR drugs that have been discovered by use of structural information that are in clinical development. This review aims to highlight the key developments that have brought success to GPCR structure resolution efforts and exemplify the practical application of structural information for the discovery of adenosine A_2A receptor antagonists that have potential to treat multiple conditions.

New therapeutic strategies for the treatment of male lower urinary tract symptoms

Male lower urinary tract symptoms (LUTS) are prevalent in the general population, especially in those of advanced age, and are characterized by notable diversity in etiology and presentation, and have been proven to cause various degrees of impairment on quality of life. The prostate has traditionally been regarded as the core cause of male LUTS. As a result, medical treatment aims to provide symptomatic relief and effective management of progression of male LUTS due to benign prostatic enlargement. In this context, α₁-blockers, phosphodiesterase-5 inhibitors, and 5α-reductase inhibitors have long been used as monotherapies or in combination treatment to control voiding LUTS. There is accumulating evidence, however, that highlights the role of the bladder in the pathogenesis of male LUTS. Current research interests have shifted to bladder disorders, and medical management is aimed at the bladder. Muscarinic receptor antagonists and the newly approved β₃-adrenergic agonist mirabegron aim to alleviate the most bothersome storage LUTS and thus improve quality of life. As voiding and storage LUTS frequently coexist, combination therapeutic strategies with α₁-blockers and antimuscarinics or β₃-agonists have been introduced to manage symptoms effectively. Anti-inflammatory agents, vitamin D₃-receptor analogs, and cannabinoids represent treatment modalities currently under investigation for use in LUTS patients. Furthermore, luteinizing hormone-releasing hormone antagonists, transient receptor-potential channel blockers, purinergic neurotransmission antagonists, Rho-kinase inhibitors, and inhibitors of endothelin-converting enzymes could have therapeutic potential in LUTS management, but still remain in the experimental setting. This article reviews new strategies for the medical treatment of male LUTS, which are dictated by the potential role of the bladder and the risk of benign prostatic hyperplasia progression. Moreover, combination treatments and therapies currently under investigation are also presented.

Cardiac salvage by tweaking with beta-3-adrenergic receptors

Overstimulation of the orthosympathetic system leads to cardiovascular cell and tissue damage through prolonged activation of β-1-2 adrenergic receptors (BARs). The more recent identification of the third isotype of BAR (B3AR) in cardiac myocytes and endothelial cells with a distinctive coupling and effect on cardiac function and remodelling introduced a new facet to this paradigm. In particular, B3AR is up-regulated in cardiac disease and less prone to homologous desensitization, which may reinforce its influence on the diseased myocardium. Mice with transgenic cardiac-specific expression of the human B3AR are protected from cardiac hypertrophy and fibrosis in response to neurohormonal stimulation. B3AR has also been implicated in cardiac protection after ischaemia-reperfusion and the benefits of exercise on the heart. Many of these salvage mechanisms are mediated by B3AR coupling to nitric oxide synthase (eNOS and nNOS) and downstream cGMP/protein kinase G signalling. Notably, B3AR exerts antioxidant protective effects on these and other signalling elements, which may subserve its protective properties in the setting of chronic heart failure. Additional vasorelaxing properties and paracrine NO-mediated signalling by B3AR in endothelium, together with systemic metabolic effects on beige/brown fat complete the pleiotropic protective properties of this new therapeutic target.