Cryo-EM structure of the ß3-adrenergic receptor reveals the molecular basis of subtype selectivity.

The ß3-adrenergic receptor (ß3AR) is predominantly expressed in adipose tissue and urinary bladder and has emerged as an attractive drug target for the treatment of type 2 diabetes, obesity, and overactive bladder (OAB). Here, we report the cryogenic electron microscopy structure of the ß3AR-Gs signaling complex with the selective agonist mirabegron, a first-in-class drug for OAB. Comparison of this structure with the previously reported ß1AR and ß2AR structures reveals a receptor activation mechanism upon mirabegron binding to the orthosteric site. Notably, the narrower exosite in ß3AR creates a perpendicular pocket for mirabegron. Mutational analyses suggest that a combination of both the exosite shape and the amino-acid-residue substitutions defines the drug selectivity of the ßAR agonists. Our findings provide a molecular basis for ßAR subtype selectivity, allowing the design of more-selective agents with fewer adverse effects.

Detrusor relaxing agents for neurogenic detrusor overactivity: a systematic review, meta-analysis and network meta-analysis.

OBJECTIVE: To evaluate the evidence regarding the therapeutic benefits and safety of oral detrusor relaxing agents (DRAs) in treating neurogenic detrusor overactivity (NDO). METHODS: A comprehensive search was performed on 1 September 2022. Two authors independently reviewed the articles to extract data using a pre-designed form. The meta-analysis was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. A common-effect or random-effects model was used based on the heterogeneity among studies. Bayesian network meta-analysis (NMA) was further performed to make indirect comparisons of antimuscarinics and mirabegron. RESULTS: A total of 23 randomised controlled trials (RCTs) comprising 1697 patients were included in our analysis. Compared to placebo, the clinical benefits of oral DRAs, along with more adverse events (AEs), were demonstrated in the treatment of NDO. In the subgroup analysis, antimuscarinics significantly improved both urodynamic and bladder diary outcomes (including urinary incontinence episodes, urinary frequency, and residual volume), with a higher rate of AEs, such as xerostomia. Mirabegron improved some of the parameters and had fewer bothersome side-effects in patients with NDO. The NMA showed that none of the antimuscarinics or mirabegron was superior or inferior to the other. CONCLUSIONS: Detrusor relaxing agents are associated with improved outcomes in patients with NDO and our analysis has added new evidence regarding antimuscarinics. Evidence concerning mirabegron as first-line therapy for NDO is still limited. Well-designed RCTs are still required in this specific population.

Comparison of mirabegron and vibegron for clinical efficacy and safety in female patients with overactive bladder: a multicenter prospective randomized crossover trial.

PURPOSE: To compare the efficacy and safety of mirabegron and vibegron in female OAB patients. METHODS: We conducted a multicenter, prospective, randomized crossover study of female patients with OAB. The patients were assigned to Group MV (mirabegron for 8 weeks, followed by vibegron for 8 weeks) or group VM (vibegron for 8 weeks, followed by mirabegron for 8 weeks). The primary endpoint was the change in OABSS from baseline, and the secondary endpoint was the change in FVC parameters. After completion of the study, each patient was asked which drug was preferable. RESULTS: A total of 83 patients were enrolled (40 and 43 in groups MV and VM, respectively). At 8th and 16th week, 33 and 29 in Group MV and 34 and 27 in Group VM continued to receive the treatment. The change in PVR was not significantly different between treatment with mirabegron and vibegron. The changes in OABSS, nighttime frequency, mean, and maximum voided volume were similar between mirabegron and vibegron. The mean change in the daytime frequency was greater in the vibegron than in the mirabegron. Of the 56 patients, 15 (27%) and 30 (53%) preferred mirabegron and vibegron, respectively. The remaining 11 patients (20%) showed no preference. The change in the urgency incontinence score during vibegron was better in patients who preferred vibegron to mirabegron. CONCLUSION: The efficacies of mirabegron and vibegron in female patients was similar. The patients' preference for vibegron could depend on the efficacy of vibegron for urgency incontinence.

Efficacy of transcutaneous electrical nerve stimulation combined with mirabegron therapy compared with mirabegron monotherapy for overactive bladder: a prospective randomized controlled study.

PURPOSE: The objective was to evaluate the efficacy of transcutaneous electrical nerve stimulation (TENS) combined with mirabegron therapy compared with mirabegron monotherapy in the treatment of female patients with overactive bladder (OAB). METHODS: In this randomized controlled study, 100 female outpatients with OAB were screened. Among these patients, 86 who met the inclusion criteria were randomly divided into the TENS combined with mirabegron treatment group and mirabegron monotherapy treatment group, with 43 patients in each group. The voiding diary, Overactive Bladder Symptom Score (OABSS), Overactive Bladder Questionnaire Symptom Bother Score (OAB-q SBS), total health-related quality of life (OAB-q HRQoL), and treatment satisfaction-visual analog scale (TS-VAS) score before and after treatment were recorded to evaluate the efficacy of OAB treatment. Seventy-nine of the 86 patients (40 in the TENS plus mirabegron group and 39 in the mirabegron monotherapy group) completed 12 weeks of treatment. RESULTS: TENS combined with mirabegron therapy was superior to mirabegron monotherapy in improving the primary endpoints, including the daily number of micturition episodes and the daily MVV/micturition and secondary endpoints, including the daily number of urgency episodes, the OABSS, the OAB-q SBS, the HRQoL score and TS-VAS score. There were no statistically significant differences in urgency urinary incontinence and nocturia between the groups. Some minor adverse effects were observed, including muscle pain, local paresthesia and constipation. CONCLUSIONS: The combination of TENS and mirabegron was more effective than mirabegron alone in the treatment of female patients with OAB. TRIAL REGISTRATION NUMBER: ChiCTR2400080528 (31.01.2024, retrospectively registered).

An individual participant meta-analysis of mirabegron in multiple sclerosis and spinal cord injury.

INTRODUCTION: Our objective was to conduct an individual patient data meta-analysis (IPDMA) of the two published randomized placebo-controlled trials of mirabegron in people with neurogenic lower urinary tract dysfunction (NLUTD) due to spinal cord injury (SCI) or multiple sclerosis (MS). METHODS: We identified two randomized, placebo-controlled trials. We extracted individual patient data from the trials and evaluated two primary outcomes: change in maximum cystometric capacity and change in the patient perception of bladder condition (PPBC). We also evaluated several secondary outcomes related to urodynamic function and quality of life. We conducted three exploratory analyses to test hypotheses based on our clinical experiences with mirabegron in NLUTD. Analysis of covariance with adjustment for baseline values was used for the statistical analysis. RESULTS: Our IPDMA included 98 patients from the two trials. The results showed that mirabegron was associated with a significant improvement in maximum cystometric capacity (+41 mL, p = 0.04) and in the PPBC (-0.8, p < 0.01) compared to placebo. Secondary outcomes including peak neurogenic detrusor overactivity pressure (-20 cm H2O, p < 0.01), incontinence-QOL score (+12, p < 0.01), and 24 h pad weights (-79 g, p = 0.04) also improved significantly compared to placebo. Exploratory analyses found similar improvements in people with MS and SCI; some outcomes improved to a greater degree among people with incomplete SCI, or SCIs that were below T7. CONCLUSIONS: Our IPDMA provides evidence supporting the use of mirabegron in patients with NLUTD due to SCI or MS. Further work evaluating differential responses in people with different SCI lesion characteristics may be warranted.

In vitro effects of ß3-adrenoceptor agonist mirabegron on the human ureter.

INTRODUCTION: This study aimed to investigate the effect of mirabegron, a ß3-adrenoceptor agonist with widespread clinical use for treating overactive bladder disease, on isolated healthy human ureter strips. MATERIALS AND METHODS: This was a prospective study employing a series of in vitro organ bath experiments using ureteral tissues of kidney grafts from 10 healthy donors. The ureteral strips were subjected to cumulative mirabegron concentrations (10-9-10-4.5 M). Effects on frequency or amplitude of spontaneous, 10 mM KCl- or EFS-induced contractions were evaluated. RESULTS: Mirabegron decreased the frequency of spontaneous ureteric contraction in a concentration-dependent manner. Statistically significant decrease in the frequency of spontaneous contraction was observed at 10-8-10-4.5 M. In 10 mM KCl medium, statistically significant change in frequency was observed at 10-9-10-4.5 M. Statistically significant decrease in the amplitudes of spontaneous contraction was observed at 10-7-10-4.5 M. In a 10 mM KCl medium, statistically significant change in amplitudes was observed at 10-8-10-4.5 M. CONCLUSIONS: Mirabegron reduced the amplitude and frequency of human ureter activity in in vitro organ bath studies. This effect was achieved in a dose-dependent manner on isolated tissue strips. Although monotherapy with mirabegron remains uncertain, this study has the potential to elucidate the mechanism underlying the effectiveness of mirabegron, particularly in combination therapy for ureteral stones.

Safety and efficacy of an α1 -blocker plus mirabegron compared with an α1 -blocker plus antimuscarinic in men with lower urinary tract symptoms secondary to benign prostatic hyperplasia and overactive bladder: A systematic review and network meta-analysis.

AIM: Antimuscarinics and the ß3-adrenoreceptor agonist, mirabegron, are commonly used for treating patients with overactive bladder (OAB) and α1 -adrenoreceptor antagonists (α1 -blockers) are the main pharmacological agents used for treating lower urinary tract symptoms (LUTS) secondary to benign prostatic hyperplasia (BPH). As these conditions commonly occur together, the aim of this systematic review was to identify publications that compared the use of an α1 -blocker plus mirabegron with an α1 -blocker plus antimuscarinic in men with LUTS secondary to BPH and OAB. A meta-analysis was subsequently conducted to explore the safety and efficacy of these combinations. METHODS: Included records had to be from a parallel-group, randomized clinical trial that was ≥8 weeks in duration. Participants were male with LUTS secondary to BPH and OAB. The indirect analyses that were identified compared an α1 -blocker plus OAB agent with an α1 -blocker plus placebo. The PubMed/Medical Literature Analysis and Retrieval System Online, the Excerpta Medica Database, the Cochrane Central Register of Controlled Trials, and the ClinicalTrials.gov registry were searched for relevant records up until March 5, 2020. Safety outcomes included incidences of overall treatment-emergent adverse events (TEAEs) and urinary retention, postvoid residual volume, and maximum urinary flow (Qmax ). Primary efficacy outcomes were micturitions/day, incontinence episodes/day, and urgency episodes/day, and secondary outcomes were Overactive Bladder Symptom Score and International Prostate Symptom Score. A Bayesian network meta-analysis approach was used for the meta-analysis. RESULTS: Out of a total of 1039 records identified, 24 were eligible for inclusion in the meta-analysis. There were no statistically significant differences between the α1 -blocker plus mirabegron and α1 -blocker plus antimuscarinic groups in terms of the comparisons identified for all the safety and efficacy analyses conducted. Numerically superior results were frequently observed for the α1 -blocker plus mirabegron group compared with the α1 -blocker plus antimuscarinic group for the safety parameters, including TEAEs, urinary retention, and Qmax . For some of the efficacy parameters, most notably micturitions/day, numerically superior results were noted for the α1 -blocker plus antimuscarinic group. Inconsistency in reporting and study variability were noted in the included records, which hindered data interpretation. CONCLUSION: This systematic review and meta-analysis showed that an α1 -blocker plus mirabegron and an α1 -blocker plus antimuscarinic have similar safety and efficacy profiles in male patients with LUTS secondary to BPH and OAB. Patients may, therefore, benefit from the use of either combination within the clinical setting.

Fragility of overactive bladder medication clinical trials: A systematic review.

PURPOSE: Overactive bladder (OAB) syndrome significantly impairs quality of life, often necessitating pharmacological interventions with associated risks. The fragility of OAB trial outcomes, as measured by the fragility index (FI: smallest number of event changes to reverse statistical significance) and quotient (FQ: FI divided by total sample size expressed as a percentage), is critical yet unstudied. MATERIALS AND METHODS: We conducted a systematic search for randomized controlled trials on OAB medications published between January 2000 and August 2023. Inclusion criteria were trials with two parallel arms reporting binary outcomes related to OAB medications. We extracted trial details, outcomes, and statistical tests employed. We calculated FI and FQ, analyzing associations with trial characteristics through linear regression. RESULTS: We included 57 trials with a median sample size of 211 participants and a 12% median lost to follow-up. Most studies investigated anticholinergics (37/57, 65%). The median FI/FQ was 5/3.5%. Larger trials were less fragile (median FI 8; FQ 1.0%) compared to medium (FI: 4; FQ 2.5%) and small trials (FI: 4; FQ 8.3%). Double-blinded studies exhibited higher FQs (median 2.9%) than unblinded trials (6.7%). Primary and secondary outcomes had higher FIs (median 5 and 6, respectively) than adverse events (FI: 4). Each increase in 10 participants was associated with a +0.19 increase in FI (p < 0.001). CONCLUSIONS: A change in outcome for a median of five participants, or 3.5% of the total sample size, could reverse the direction of statistical significance in OAB trials. Studies with larger sample sizes and efficacy outcomes from blinded trials were less fragile.

Effects of mirabegron on brown adipose tissue and metabolism in humans: A systematic review and meta-analysis.

BACKGROUND: Brown adipose tissue (BAT) has emerged as a potential therapeutic target for metabolic disorders due to its thermogenic and anti-obesity properties. ß3-adrenergic receptor (ß3-AR) agonists have also gained attention as potential agents for BAT activation and metabolic regulation. Mirabegron, a selective ß3-AR-agonist used clinically for overactive bladder syndrome, has been explored for its utility in metabolic disorders. However, the controversy surrounding the ability of mirabegron to activate BAT to accelerate metabolism requires further investigation. The aim of this systematic review is to characterize comprehensively the impact of mirabegron on human BAT and its metabolism. METHODS: We searched PubMed Central, Web of Science, Embase, and Cochrane Library databases for relevant papers published from the date of database inception to March 2023 for systematic reviews and meta-analyses. We extracted data on primary outcome indicators such as BAT volume, BAT activity, body temperature, and resting energy expenditure (REE), as well as secondary outcome indicators such as heart rate (HR), diastolic blood pressure (DBP), systolic blood pressure (SBP), non-esterified fatty acids (NEFA), blood glucose, and blood insulin from relevant studies. For studies that did not provide suitable data for meta-analysis, we used narrative data synthesis. For studies that provided suitable data for meta-analysis, we conducted meta-analysis using RevMan 5.4 software. RESULTS: We reviewed 10 papers and included 6 in our meta-analysis. Our findings revealed no significant changes in BAT volume (p = 0.72) or blood glucose (p = 0.52) with mirabegron when compared to the placebo or pre-dose population. However, patients showed significant increases in BAT activity (p < 0.01), blood NEFA (p < 0.01), body temperature (p < 0.01), REE (p < 0.01), HR (p < 0.01), DBP (p < 0.01), SBP (p = 0.25), and blood insulin (p < 0.01). CONCLUSION: Through our meta-analysis of 6 papers, we found that mirabegron has the potential to increase human BAT activity, REE, NEFA content, body temperature, HR, blood pressure, and blood insulin content. These effects may lead to reductions in blood glucose levels in obese/overweight and diabetic patients. Additionally, the activation of BAT by mirabegron could represent a novel approach for treating obesity, diabetes, and cardiovascular disease. TRIAL REGISTRATION NUMBER AND DATE: CRD42023413446, 04/11/2023.

Nerve Growth Factor and Brain-Derived Neurotrophic Factor as Potential Biomarkers of Mirabegron Efficacy in Patients with Overactive Bladder Syndrome.

INTRODUCTION: Overactive Bladder Syndrome (OAB) significantly impacts quality of life, necessitating improved diagnostic tools and treatment monitoring. This study explores the potential of neurotrophins, nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF) as urinary biomarkers in patients with OAB undergoing mirabegron therapy, a ß3-adrenergic agonist. This investigation is aimed at providing insights into the potential of neurotrophins to enhance OAB diagnosis and assess treatment efficacy. MATERIALS AND METHODS: Urinary NGF and BDNF levels were measured in 15 healthy controls and 30 patients with OAB. Patients were treated with mirabegron 50 mg once daily. Urinary NGF and BDNF levels were measured by enzyme-linked immunosorbent assay method and normalized by urinary creatinine levels (NGF/Cre and BDNF/Cre). The urinary NGF/Cre and BDNF/Cre levels were compared between controls and patients with OAB and subsequently at baseline and 3 months after mirabegron treatment. Treatment efficacy was assessed with the Indevus Urgency Severity Scale (IUSS) questionnaire. RESULTS: Urinary NGF/Cre and BDNF/Cre levels were significantly higher in patients with OAB than in the controls (p < 0.001 and p = 0.03 respectively). Moreover, NGF/Cre and BDNF/Cre levels significantly decreased post-mirabegron treatment (p < 0.001 and p = 0.005 respectively). Patients with improvement of OAB symptoms after treatment showed lower levels of NGF/Cre at the 3-month evaluation than those with no improvement (p = 0.05). CONCLUSION: Although both NGF/Cre and BDNF/Cre levels were significantly decreased after mirabegron treatment, only NGF/Cre levels were associated with treatment response.

Posterior Tibial Nerve Stimulation With versus Without Mirabegron: A Randomized Controlled Trial.

INTRODUCTION AND HYPOTHESIS: To compare change in urgency urinary incontinence episodes (UUIEs) in women undergoing posterior tibial nerve stimulation (PTNS) plus mirabegron versus PTNS plus placebo for the treatment of refractory urgency urinary incontinence (UUI). The primary hypothesis was that combination therapy is superior to monotherapy. METHODS: A randomized controlled trial was performed in individuals identifying as female aged ≥ 18 years with UUI symptoms refractory to second-line treatment or who could not tolerate antimuscarinic medications. Both participants and providers were blinded to medication treatment allocation. Participants were randomized (1:1) to PTNS plus mirabegron or PTNS plus placebo. Participants completed a 3-day bladder diary prior to and after 12-week treatment. Validated symptom distress and impact questionnaires were obtained pre- and post-treatment. The primary outcome was change in mean number of UUIEs on a 3-day bladder diary pre- versus post-treatment between arms. Primary and secondary outcomes were analyzed via sample t tests. RESULTS: Fifty-four subjects were randomized, mean ± SD baseline age 56.2±15.6 years and body mass index 35.0±9.4 (kg/m2); no differences were noted in any clinical-demographic characteristics. There was a significant difference between arms in mean pre- to post-treatment UUIEs, 9.4±3.9, mirabegron versus 5.3±5.5, placebo (p=0.007). Significant differences were found pre- compared with post-treatment in urinary frequency, Overactive Bladder Questionnaire Short Form Symptom Bother and Symptom Health-Related Quality of Life scores. CONCLUSIONS: In subjects undergoing PTNS treatment for refractory UUI and OAB-wet symptoms, the addition of a ß-3 agonist produced significant improvement in both objective and subjective overactive bladder symptom outcomes compared with PTNS plus placebo.

Roles of ß-adrenoceptor Subtypes and Therapeutics in Human Cardiovascular Disease: Heart Failure, Tachyarrhythmias and Other Cardiovascular Disorders.

ß-Adrenoceptors (ß-ARs) provide an important therapeutic target for the treatment of cardiovascular disease. Three ß-ARs, ß1-AR, ß2-AR, ß3-AR are localized to the human heart. Activation of ß1-AR and ß2-ARs increases heart rate, force of contraction (inotropy) and consequently cardiac output to meet physiological demand. However, in disease, chronic over-activation of ß1-AR is responsible for the progression of disease (e.g. heart failure) mediated by pathological hypertrophy, adverse remodelling and premature cell death. Furthermore, activation of ß1-AR is critical in the pathogenesis of cardiac arrhythmias while activation of ß2-AR directly influences blood pressure haemostasis. There is an increasing awareness of the contribution of ß2-AR in cardiovascular disease, particularly arrhythmia generation. All ß-blockers used therapeutically to treat cardiovascular disease block ß1-AR with variable blockade of ß2-AR depending on relative affinity for ß1-AR vs ß2-AR. Since the introduction of ß-blockers into clinical practice in 1965, ß-blockers with different properties have been trialled, used and evaluated, leading to better understanding of their therapeutic effects and tolerability in various cardiovascular conditions. ß-Blockers with the property of intrinsic sympathomimetic activity (ISA), i.e. ß-blockers that also activate the receptor, were used in the past for post-treatment of myocardial infarction and had limited use in heart failure. The ß-blocker carvedilol continues to intrigue due to numerous properties that differentiate it from other ß-blockers and is used successfully in the treatment of heart failure. The discovery of ß3-AR in human heart created interest in the role of ß3-AR in heart failure but has not resulted in therapeutics at this stage.

Mirabegron Add-On Tamsulosin for Men with Overactive Bladder Symptoms: A Pooled Analysis of Four Randomized Controlled Trials.

INTRODUCTION: Overactive bladder symptoms (OABSs) affect patients' quality of life (QOL) worldwide. This pooled analysis compared the efficacy and safety of mirabegron add-on tamsulosin with those of tamsulosin add-on placebo in OABS treatment. METHODS: PubMed, Embase, MEDLINE, and the Cochrane Controlled Trial Register databases were searched for randomized controlled trials (RCTs) examining the efficacy of mirabegron add-on therapy to tamsulosin in the treatment of OABS. Moreover, references from the selected studies were screened. Review Manager 5.4 was used to analyze data. RESULTS: Four RCTs involving 1,397 patients with OABS were selected. Of the total, 697 patients receiving mirabegron add-on tamsulosin constituted the experimental group, and 700 patients receiving tamsulosin add-on placebo constituted the control group. The efficacy endpoints were as follows: mean number of micturition per day (mean difference [MD] = -0.26, 95% confidence interval [CI] = -0.41 to -0.10, p = 0.0001), urgency episodes per day (MD = -0.67, 95% CI = -1.02 to -0.32, p = 0.0002), urgency urinary incontinence (UUI) episodes per day (MD = -0.42, 95% CI = -0.66 to -0.19, p = 0.0005), mean volume voided/micturition (MD = 10.84, 95% CI = 4.97-16.71, p = 0.0003), total International Prostate Symptom Score (IPSS) (MD = -2.01, 95% CI = -4.02 to -0.01, p = 0.05), and IPSS QOL index (MD = -0.65, 95% CI = -0.94 to -0.35, p < 0.0001). Mirabegron therapy, an add-on therapy to tamsulosin, was effective in treating patients with OABS. Moreover, mirabegron might reduce the total IPSS (MD = -2.01, 95% CI = -4.02 to -0.01, p = 0.05). The safety endpoint, treatment-emergent adverse events (odds ratio = 0.94, 95% CI = 0.78-1.13, p = 0.49), suggested that although mirabegron was well-tolerated, it possibly increased the post-void residual urine volume (MD = 10.28, 95% CI = 1.82-18.75, p = 0.02). CONCLUSION: Combination therapy using mirabegron and tamsulosin may be effective in treating patients with non-neurogenic OABS in terms of UUI episodes, total IPSS, and IPSS QOL index. However, its effectiveness must be verified by analyzing additional factors for OABS through further RCTs.

Ligand-Receptor Interactions and Structure-Function Relationships in Off-Target Binding of the ß3-Adrenergic Agonist Mirabegron to α1A-Adrenergic Receptors.

The ß3-adrenoceptor agonist mirabegron is available for the treatment of storage symptoms of overactive bladder, including frequency, urgency, and incontinence. The off-target effects of mirabegron include binding to α1-adrenoceptors, which are central in the treatment of voiding symptoms. Here, we examined the structure-function relationships in the binding of mirabegron to a cryo-electron microscopy structure of α1A. The binding was simulated by docking mirabegron to a 3D structure of a human α1A-adrenoceptor (7YMH) using Autodock Vina. The simulations identified two binding states: slope orientation involving 10 positions and horizontal binding to the receptor surface involving 4 positions. No interactions occurred with positions constituting the α1A binding pocket, including Asp-106, Ser-188, or Phe-312, despite the positioning of the phenylethanolamine moiety in transmembrane regions close to the binding pocket by contact with Phe-288, -289, and Val-107. Contact with the unique positions of α1A included the transmembrane Met-292 during slope binding and exosite Phe-86 during horizontal binding. Exosite binding in slope orientation involved contact of the anilino part, rather than the aminothiazol end, to Ile-178, Ala-103, and Asn-179. In conclusion, contact with Met-292 and Phe-86, which are unique positions of α1A, accounts for mirabegron binding to α1A. Because of its lack of interactions with the binding pocket, mirabegron has lower affinity compared to α1A-blockers and no effects on voiding symptoms.

Pre-Steady-State and Steady-State Kinetic Analysis of Butyrylcholinesterase-Catalyzed Hydrolysis of Mirabegron, an Arylacylamide Drug.

The ß-adrenergic drug Mirabegron, a drug initially used for the treatment of an overactive bladder, has new potential indications and is hydrolyzed by butyrylcholinesterase (BChE). This compound is one of the only arylacylamide substrates to be catabolized by BChE. A steady-state kinetic analysis at 25 °C and pH 7.0 showed that the enzyme behavior is Michaelian with this substrate and displays a long pre-steady-state phase characterized by a burst. The induction time, τ, increased with substrate concentration (τ ≈ 18 min at maximum velocity). The kinetic behavior was interpreted in terms of hysteretic behavior, resulting from a slow equilibrium between two enzyme active forms, E and E'. The pre-steady-state phase with the highest activity corresponds to action of the E form, and the steady state corresponds to action of the E' form. The catalytic parameters were determined as kcat = 7.3 min-1 and Km = 23.5 µM for the initial (burst) form E, and kcat = 1.6 min-1 and Km = 3.9 µM for the final form E'. Thus, the higher affinity of E' for Mirabegron triggers the slow enzyme state equilibrium toward a slow steady state. Despite the complexity of the reaction mechanism of Mirabegron with BChE, slow BChE-catalyzed degradation of Mirabegron in blood should have no impact on the pharmacological activities of this drug.

Intestinal Absorption Site-Guided Development and Evaluation of Oral Disintegrating Controlled Release Tablets of Mirabegron.

The aim was to employ site-dependent absorption of mirabegron (MB) as a guide for fabrication of oral disintegrating controlled release tablet (ODCRT) which undergoes instantaneous release of loading fraction followed by delayed release of the rest of MB. The goal was to release MB in a manner consistent with the chronobiology of overactive bladder (OAB) syndrome. In situ rabbit intestinal permeability of MB was adopted to assess absorption sites. MB was subjected to dry co-grinding with citric acid to develop the fast-dissolving fraction in the mouth. Delayed release fraction was formulated by ethanol-assisted co-processing with increasing proportions of Eudragit polymer (S100) as pH responsive polymer. The developed dry mixtures underwent thermal (DSC) and physical (X-ray diffraction) characterization, in addition to in vitro release behavior. Optimized fast dissolving and delayed release formulations were mixed with tablet excipient before compression in ODCRT which was assessed for release profile using continuous pH variation. MB underwent preferential permeation through ileum and colon. Co-grinding with citric acid provided co-amorphous powder with fast dissolution. Co-amorphization of MB with Eudragit S100 (1:5) showed pH-dependent release to release most of the dose at pH 7.4. The developed ODCRT released 43.5% of MB in the buccal environment and retained MB at acidic pH to start release at pH 7.4. The study successfully fabricated ODCRT guided by site-dependent absorption. The ODCRT instantaneously released loading fraction to support the patient after administration with delayed fraction to sustain the effect.

Investigation of Mirabegron-loaded Nanostructured Lipid Carriers for Improved Bioabsorption: Formulation, Statistical Optimization, and In-Vivo Evaluation.

Overactive bladder (OAB) is a usual medical syndrome that affects the bladder, and Mirabegron (MBG) is preferred medicine for its control. Currently, available marketed formulations (MYRBETRIQ® granules and MYRBETRIQ® ER tablets) suffer from low bioavailability (29-35%) hampering their therapeutic effectiveness and compromising patient compliance. By creating MBG nanostructured lipid carriers (MBG-NLCs) for improved systemic availability and drug release, specifically in oral administration of OAB treatment, this study aimed to address these issues. MBG-NLCs were fabricated using a hot-melt ultrasonication technique. MBG-GMS; MBG-oleic acid interaction was assessed by in silico molecular docking. QbD relied on the concentration of Span 80 (X1) and homogenizer speed (X2) as critical material attribute (CMA) and critical process parameter (CPP) respectively, while critical quality attributes (CQA) such as particle size (Y1) and cumulative drug release at 24 h (Y2) were estimated as dependent variables. 32 factorial design was utilized to investigate the interconnection in variables that are dependent and independents. Optimized MBG-NLCs with a particle size of 194.4 ± 2.25 nm were suitable for lymphatic uptake. A PDI score of 0.275 ± 0.02 and zeta potential of -36.2 ± 0.721 mV indicated a uniform monodisperse system with stable dispersion properties. MBG-NLCs exhibited entrapment efficiency of 77.3 ± 1.17% and a sustained release in SIF of 94.75 ± 1.60% for 24 h. MBG-NLCs exhibited the Higuchi model with diffusion as a release mechanism. A pharmacokinetic study in Wistar rats exhibited a 1.67-fold higher bioavailability as compared to MBG suspension. Hence, MBG-NLCs hold promise for treating OAB by improving MBG's oral bio absorption.

Development and validation of stability indicating RP-HPLC method for simultaneous estimation of silodosin and mirabegron in synthetic mixture.

The study focuses to validate and develop a precise, simple and accurate stability indicating RP-HPLC method for estimation simultaneously of and silodosin and mirabegron in synthetic mixture. The chromatographic separation was achieved by using Shimpack Solar C18 column (250×4.5mm, 5µm) with acetonitrile: 5mM ammonium acetate in ratio of 90:10% v/v as a mobile phase at a constant flow rate of about 1.2mL/min. The development and validation were carried out at detection wavelength of 229nm. We developed a robust RP-HPLC method, validated for linearity, precision, accuracy, specificity, and system suitability. The method demonstrated excellent linearity with correlation coefficient value r2 was nearly 0.998 with linearity range 8-18µg/mL for Silodosin and 24-54µg/mL for mirabegron. LOD and LOQ were found to be lower; hence, the method is sensitive. Percentage recovery was obtained 99.97% and 99.99% for silodosin and mirabegron, respectively. In case of precision, robustness and repeatability, RSD was found to be less than 2. The validated and developed RP-HPLC method offers an efficient and practical approach for the simultaneous quantification of silodosin and mirabegron in pharmaceutical formulations, making it a valuable tool for quality control and pharmaceutical research.

Brown adipose tissue and regulation of human body weight.

BACKGROUND: Approximately 30% of the global population is affected by obesity. Traditional non-surgical measures for weight loss have limited efficacy and tolerability. Therefore, there is a need for novel, effective therapies. Brown adipose tissue (BAT) has been implicated in physiological energy expenditure, indicating that it could be targeted to achieve weight loss in humans. The use of 18 F-fluorodeoxyglucose (18 F-FDG) positron emission tomography-computed tomography-(PET-CT) imaging has enabled the discovery of functionally active BAT in the supraclavicular, subclavian, and thoracic spine regions of human adults. This review aims to discuss the reasons behind the renewed interest in BAT, assess whether it is metabolically important in humans, and evaluate its feasibility as a therapeutic target for treating obesity. SOURCES OF MATERIAL: PubMed Central, Europe PMC, Medline. FINDINGS: In vivo studies have shown that BAT activity is regulated by thyroid hormones and the sympathetic nervous system. Furthermore, BAT uniquely contains uncoupling protein 1 (UCP1) that is largely responsible for non-shivering thermogenesis. Cold exposure can increase BAT recruitment through the browning of white adipose tissue (WAT); however, this technique has practical limitations that may preclude its use. Currently available medicines for humans, such as the ß3-adrenergic receptor agonist mirabegron or the farnesoid X receptor agonist obeticholic acid, have generated excitement, although adverse effects are a concern. Capsinoids represent a tolerable alternative, which require further investigation. CONCLUSIONS: The use of currently available BAT-activating agents alone is unlikely to achieve significant weight loss in humans. A combination of BAT activation with physical exercise and modern, successful dietary strategies represents a more realistic option.

Does metabolic syndrome influence the efficacy of mirabegron treatment in female patients with overactive bladder?

INTRODUCTION AND HYPOTHESIS: We aimed to determine whether the presence of metabolic syndrome (MS) affects the efficacy of mirabegron in treatment-naïve women with overactive bladder (OAB). METHODS: Women being treated with mirabegron 50 mg were allocated to MS and non-MS groups, and the efficacy of treatment of OAB was compared using the OAB symptom score (OABSS) and a 3-day voiding diary before and 12 weeks after starting treatment. The Wilcoxon signed-rank and Mann-Whitney U tests and multivariate logistic regression were used for statistical analyses, and a p-value < 0.05 was considered to represent statistical significance. RESULTS: Of the 197 patients who completed the trial, 43 (23.9%) had MS. After 12 weeks of mirabegron treatment, both the MS and non-MS groups showed significant improvements in OABSS score, the number of incontinence episodes/24 h, the number of micturition episodes/24 h, and the number of episodes of urgency/24 h. The factors associated with clinically important differences in OABSS were the presence of hyperglycemia (odds ratio 2.43, 95% confidence interval [CI] 1.05-5.60) and OABSS score at baseline (odds ratio 1.23, 95% CI 1.09-1.39). CONCLUSIONS: Mirabegron is effective in patients with and without MS, and comorbid hyperglycemia and severe OAB symptoms before treatment are predictors of the efficacy of mirabegron treatment.