Darifenacin: a novel M3muscarinic selective receptor antagonist for the treatment of overactive bladder

Darifenacin Self-assembled Liquid Crystal Cubic Nanoparticles: a Sustained Release Approach for an Overnight Control of Overactive Bladder

The current study is regarding the development and characterization of Darifenacin-loaded self-assembled liquid crystal cubic nanoparticles (LCCN). An anhydrous approach was used for the preparation of these cubic nanoparticles using a hydrotropic agent (propylene glycol), with minimal energy input. Upon dispersion in aqueous medium, the system was successfully transformed to cubosomal nanoparticles counterpart as depicted by transmission electron micrographs. A Box-Behnken design was used to optimize formulation variables, namely A: amount of GMO, B: amount of Pluronic F127, C: amount of PG, and D: amount of HPMC. The design has generated 29 formulae which were tested regarding drug content uniformity, dispersibility in water, particle size, zeta potential, polydispersity index, and in vitro release behavior. The numerical optimization algorithms have generated an optimized formula with high desirability ≈ 1. The optimized formula displayed small particle size, good homogeneity, and zeta potential along with controlled in vitro release profile and ex vivo permeation through rabbit intestine. Thus, self-assembled LCCN might offer an alternative anhydrous approach for the preparation of cubosomal nanoparticles with controlled release profile for a possibly better control of overactive bladder syndrome which tremendously affect the overall life quality.

Acetylcholine Receptor Activation as a Modulator of Glioblastoma Invasion

Grade IV astrocytomas, or glioblastomas (GBMs), are the most common malignant primary brain tumor in adults. The median GBM patient survival of 12–15 months has remained stagnant, in spite of treatment strategies, making GBMs a tremendous challenge clinically. This is at least in part due to the complex interaction of GBM cells with the brain microenvironment and their tendency to aggressively infiltrate normal brain tissue. GBMs frequently invade supratentorial brain regions that are richly innervated by neurotransmitter projections, most notably acetylcholine (ACh). Here, we asked whether ACh signaling influences the biology of GBMs. We examined the expression and function of known ACh receptors (AChRs) in large GBM datasets, as well as, human GBM cell lines and patient-derived xenograft lines. Using RNA-Seq data from the “The Cancer Genome Atlas” (TCGA), we confirmed the expression of AChRs and demonstrated the functionality of these receptors in GBM cells with time-lapse calcium imaging. AChR activation did not alter cell proliferation or migration, however, it significantly increased cell invasion through complex extracellular matrices. This was due to the enhanced activity of matrix metalloproteinase-9 (MMP-9) from GBM cells, which we found to be dependent on an intracellular calcium-dependent mechanism. Consistent with these findings, AChRs were significantly upregulated in regions of GBM infiltration in situ (Ivy Glioblastoma Atlas Project) and elevated expression of muscarinic AChR M₃ correlated with reduced patient survival (TCGA). Data from the Repository for Molecular Brain Neoplasia Data (REMBRANDT) dataset also showed the co-expression of choline transporters, choline acetyltransferase, and vesicular acetylcholine transporters, suggesting that GBMs express all the proteins required for ACh synthesis and release. These findings identify ACh as a modulator of GBM behavior and posit that GBMs may utilize ACh as an autocrine signaling molecule.

Does concomitant diabetes affect treatment responses in overactive bladder patients?

AIMS

To compare the efficacy and tolerability of a muscarinic receptor antagonist, darifenacin, in the treatment of overactive bladder (OAB) patients with concomitant diabetes as compared with those without comorbidities.

METHODS

Post hoc exploratory analysis of a published, large, non-interventional study in OAB patients treated with darifenacin including 532 diabetics and 1315 controls. Associations of diabetes with treatment responses were evaluated by multiple regression models.

RESULTS

Diabetics (largely type 2 patients) and controls differed in baseline age, body weight, duration of OAB symptoms and presence of co-medications. However, they exhibited similar OAB symptom episode frequency and problem rating and received similar starting doses of darifenacin. Presence of diabetes was associated with a significantly smaller reduction of OAB symptoms, but the effect attributable to diabetes was small relative to the overall treatment response. The presence of diabetes was not associated with differences in tolerability.

DISCUSSION AND CONCLUSIONS

We conclude that a muscarinic receptor antagonist has comparable efficacy and tolerability in the treatment of OAB patients with and without concomitant diabetes.

Dual-pharmacology muscarinic antagonist and β₂ agonist molecules for the treatment of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death in the world today. Bronchodilators, particularly muscarinic antagonists and β(2) agonists, are recommended for patients with moderate to severe COPD. Dual-pharmacology muscarinic antagonist- β(2) agonist (MABA) molecules present an exciting new approach to the treatment of COPD by combining muscarinic antagonism and β(2) agonism in a single entity. They have the potential to demonstrate additive or synergistic bronchodilation over either pharmacology alone. Due to this enticing prospect, several companies have now reported MABA discovery efforts through a conjugated/linked strategy with one candidate (GSK-961081) demonstrating clinical proof of concept. Several MABA crystal forms have been identified, satisfying the requirements for inhaled dosing devices. There are significant challenges in designing MABAs, but the potential to achieve enhanced bronchoprotection in patients and facilitate 'triple therapy' makes this an extremely important and exciting area of pharmaceutical research.

An overview of the clinical use of antimuscarinics in the treatment of overactive bladder

Overactive bladder is a common and bothersome condition. Antimuscarinic agents, as a class, are the cornerstone of medical treatment of overactive bladder. They offer significant improvements in symptoms and patients' quality of life. Antimuscarinics are generally well tolerated with mild and predictable side effects. Available antimuscarinics have small, yet statistically significant, differences in their efficacy and tolerability profiles. In clinical practice, finding the agent that offers the optimum balance of efficacy and side effects for an individual patient remains the major challenge.

Pharmacologic therapy for the neurogenic bladder

This article is a review of the current and past literature on medical management of the neurogenic bladder, with a particular focus on spinal cord injury and multiple sclerosis. The use of antimuscarinics, αα-blocker, and tricyclic antidepressants and their combined use are discussed along with new therapies in human and animal trials.

Long-acting muscarinic M3 receptor antagonists

Two applications claim a novel class of muscarinic M(3) receptor antagonists and their use as long-acting agents for the treatment of chronic obstructive pulmonary disease. The two applications claim closely related structures with one claiming quaternary amine salts of the tertiary amines claimed in the other. The claimed compounds comprise a biarylmethylamine core with the amino group modified by acylation or sulfonation and a tertiary or quaternary amine coupled to the distal ring of the biaryl system.

Darifenacin hydro-bromide

In the title compound {systematic name: (S)-3-[(aminocar­bonyl)diphenylmethyl]-1-[2-(2,3-di­hy­dro­benzofuran-5-yl)ethyl]pyrrolidinium bromide}, C₂₈H₃₁N₂O₂⁺·Br⁻, the pyrrolidine rings adopts an envelope conformation. The two phenyl rings make a dihedral angle of 72.5 (1)°. The four coplanar atoms of the pyrrolidine ring makes dihedral angles of 33.1 (2) and 82.8 (2)° with the two phenyl rings. The mol­ecular conformation is influenced by a C—H⋯O inter­action. In the crystal packing, there are two N—H⋯Br hydrogen bonds running in opposite directions. They appear to form C(10) and C(9) chain motifs in the unit cell. In addition, the mol­ecular packing is further stabilized by C—H⋯Br and C—H⋯O hydrogen bonds. The C atom bonded to the benzofuran ring system is disordered in a 0.66:0.34 ratio.

Synthesis and optimization of novel and selective muscarinic M3 receptor antagonists

A series of constrained piperidine analogues were synthesized as novel muscarinic M(3) receptor antagonists. Evaluation of these compounds in binding assays revealed that they not only have high affinity for the M(3) receptor but also have high selectivity over the M(2) receptor.

Molecular characterization of M2 and M3 muscarinic receptor expression in bladder from women with refractory idiopathic detrusor overactivity

OBJECTIVE

To examine the expression of muscarinic M2 and M3 receptors in human bladder detrusor and mucosa, from controls and patients with idiopathic detrusor overactivity (IDO), as antimuscarinic agents are the primary pharmacological treatment for IDO.

PATIENTS AND METHODS

Biopsies from the bladder body were collected at cystoscopy from 20 women with urodynamically confirmed refractory IDO (age range 25-86 years); biopsies were also collected from 30 asymptomatic female controls (age range 32-87 years). Samples were collected into RNA extraction medium and dissected into mucosa (urothelium plus lamina propria) and detrusor. RNA was extracted and the expression of M2 and M3 receptor mRNA determined by quantitative competitive reverse transcription-polymerase chain reaction. Results were normalized to beta-actin expression in the same sample.

RESULTS

Expression of M3 receptor mRNA, in mucosa of IDO patients (median 0.057 pg M3/100 ng total RNA; interquartile range 0.03-0.13, 12 samples), was four times (P = 0.039, Mann-Whitney) lower than from the control (median 0.22 pg M3/100 ng total RNA; 0.13-0.51, 11 samples). The expression of muscarinic M3 receptor mRNA was higher (14-35 times) in detrusor (control median 3.17; 26 samples) than in mucosa and did not change in IDO (median 2.03; 14 samples). M2 expression was not significantly different with region or with IDO.

CONCLUSIONS

These data show that M3 muscarinic receptor mRNA expression was significantly less in mucosa from IDO patients than from age-matched controls. The role of mucosal M3 receptors is unknown at present and elucidation of this role might provide a greater understanding of the aetiology of IDO.

Characterization of a novel ATP-sensitive K+ channel opener, A-251179, on urinary bladder relaxation and cystometric parameters

BACKGROUND AND PURPOSE

ATP-sensitive K(+) channels (K(ATP)) play a pivotal role in contractility of urinary bladder smooth muscle. This study reports the characterization of 4-methyl-N-(2,2,2-trichloro-1-(3-pyridin-3-ylthioureido)ethyl)benzamide (A-251179) as a K(ATP) channel opener.

EXPERIMENTAL APPROACH

Glyburide-sensitive membrane potential, patch clamp and tension assays were employed to study the effect of A-251179 in vitro. The in vivo efficacy of A-251179 was characterized by suppression of spontaneous contractions in obstructed rat bladder and by measuring urodynamic function of urethane-anesthetized rat models.

KEY RESULTS

A-251179 was about 4-fold more selective in activating SUR2B-Kir6.2 derived K(ATP) channels compared to those derived from SUR2A-Kir6.2. In pig bladder smooth muscle strips, A-251179 suppressed spontaneous contractions, about 27- and 71-fold more potently compared to suppression of contractions evoked by low-frequency electrical stimulation and carbachol, respectively. In vivo, A-251179 suppressed spontaneous non-voiding bladder contractions from partial outlet-obstructed rats. Interestingly, in the neurogenic model where isovolumetric contractions were measured by continuous transvesical cystometry, A-251179 at a dose of 0.3 micromol kg(-1), but not higher, was found to increase bladder capacity without affecting either the voiding efficiency or changes in mean arterial blood pressure.

CONCLUSIONS AND IMPLICATIONS

The thioureabenzamide analog, A-251179 is a potent novel K(ATP) channel opener with selectivity for SUR2B/Kir6.2 containing K(ATP) channels relative to pinacidil. The pharmacological profile of A-251179 is to increase bladder capacity and to prolong the time between voids without affecting voiding efficiency and represents an interesting characteristic to be explored for further investigations of K(ATP) channel openers for the treatment of overactive bladder.

Comparative evaluation of central muscarinic receptor binding activity by oxybutynin, tolterodine and darifenacin used to treat overactive bladder

PURPOSE

We characterized muscarinic receptor binding in the mouse cerebral cortex after oral administration of anticholinergic agents used to treat overactive bladder.

MATERIALS AND METHODS

Muscarinic receptors in the mouse cerebral cortex and bladder after oral administration of anticholinergic agents were measured using [(3)H]N-methylscopolamine.

RESULTS

In vitro binding affinities of tolterodine and its metabolite 5-hydroxymethyl metabolite in the mouse cerebral cortex and bladder were considerably greater than those of oxybutynin and darifenacin. Also, muscarinic receptor binding affinity of oxybutynin and its metabolite N-desethyl-oxybutynin in the cerebral cortex compared with that in the bladder was 2 to 3 times higher, whereas that of tolterodine and 5-hydroxymethyl metabolite was approximately 2 times lower. Oral administration of oxybutynin (76.1 micromol/kg), tolterodine (6.31 micromol/kg) and darifenacin (59.1 micromol/kg) showed binding activity that was approximately equal to that of bladder muscarinic receptors. Oral administration of oxybutynin (76.1 micromol/kg) showed significant binding of cerebral cortical muscarinic receptors in mice, as indicated by about a 2-fold increase in K(d) values for specific [(3)H]N-methylscopolamine binding 0.5 and 2 hours later. On the other hand, tolterodine and darifenacin given at oral doses that would exert a similar extent of bladder receptor binding activity as oxybutynin showed only a low level of binding activity of central muscarinic receptors in mice.

CONCLUSIONS

Significant binding of brain muscarinic receptors in mice was observed by the oral administration of oxybutynin but not tolterodine and darifenacin.

Darifenacin: Pharmacology and Clinical Usage

Darifenacin is one of several recently approved antimuscarinics for the treatment of overactive bladder (OAB) and urge urinary incontinence. Darifenacin is an effective drug for the treatment of OAB and is tolerated by patients. Darifenacin's M3 selectivity is unique among antimuscarinics. This M3 selectivity could confer advantages in patients who have cardiovascular side effects (tachycardia), impaired cognition, complaints of dizziness, or sleep disturbances. In some studies, darifenacin caused less dry mouth than oxybutynin. Rates of constipation, although significant, are tolerated and rarely a cause for discontinuation in clinical trials. This review describes the role of M3 receptors and covers the mechanism of action, pharmacokinetic properties, clinical efficacy safety and tolerability, drug interactions, and dosing guidelines for darifenacin.

Propiverine and metabolites: differences in binding to muscarinic receptors and in functional models of detrusor contraction

Propiverine is a commonly used antimuscarinic drug used as therapy for symptoms of an overactive bladder. Propiverine is extensively biotransformed into several metabolites that could contribute to its spasmolytic action. In fact, three propiverine metabolites (M-5, M-6 and M-14) have been shown to affect various detrusor functions, including contractile responses and L-type calcium-currents, in humans, pigs and mice, albeit with different potency. The aim of our study was to provide experimental evidence for the relationship between the binding of propiverine and its metabolites to human muscarinic receptor subtypes (hM(1)-hM(5)) expressed in chinese hamster ovary cells, and to examine the effects of these compounds on muscarinic receptor-mediated detrusor function. Propiverine, M-5, M-6 and M-14 bound to hM(1)-hM(5) receptors with the same order of affinity for all five subtypes: M-6 > propiverine > M-14 > M-5. In HEK-293 cells expressing hM(3), carbachol-induced release of intracellular Ca(2+) ([Ca(2+)](i)) was suppressed by propiverine and its metabolites; the respective concentration-response curves for carbachol-induced Ca(2+)-responses were shifted to the right. At higher concentrations, propiverine and M-14, but not M-5 and M-6, directly elevated [Ca(2+)](i). These results were confirmed for propiverine in human detrusor smooth muscle cells (hDSMC). Propiverine and the three metabolites decreased detrusor contractions evoked by electric field stimulation in a concentration-dependent manner, the order of potency being the same as the order of binding affinity. We conclude that, in comparison with the parent compound, loss of the aliphatic side chain in propiverine metabolites is associated with higher binding affinity to hM(1)-hM(5) receptors and higher functional potency. Change from a tertiary to a secondary amine (M-14) results in lower binding affinity and reduced potency. Oxidation of the nitrogen (M-5) further lowers binding affinity as well as functional potency.

Cost implications of antimuscarinic drugs in the treatment of overactive bladder syndrome

Overactive bladder syndrome is highly prevalent, particularly among the elderly. As well as the consequent morbidity, such as urinary infections, skin irritation and bone fractures, almost all aspects of quality of life, personal and social, are influenced. Therefore, the associated cost is substantial. Pharmacotherapy with antimuscarinics is the mainstay of treatment. Because of the good balance between efficacy, safety and tolerability, these drugs seem to be cost-effective therapeutic modalities for overactive bladder. In the milieu of a constantly ageing population, rising demand for the treatment of health conditions and the need for rational use of healthcare resources, further studies with long-term antimuscarinic drug treatment and follow-up are needed to redefine their therapeutic value.

Effect of an ATP-sensitive potassium channel opener in subjects with overactive bladder: a randomized, double-blind, placebo-controlled study (ZD0947IL/0004)

OBJECTIVES

Improvements over existing treatment standards in overactive bladder (OAB) may only be possible through the development of drugs acting via non-cholinergic pathways. This is the first clinical study to be reported in full for the use of a potassium channel opener in OAB.

METHODS

This randomized, double-blind, placebo-controlled phase II study evaluated the efficacy and safety of ZD0947 (25mg/day for 12 weeks) in patients with OAB. The primary endpoint was mean volume voided per micturition per 24 hours. Key secondary endpoints were changes from baseline in mean numbers of micturition episodes (total, voluntary, and incontinent) per 24 hours.

RESULTS

ZD0947 was not superior to placebo for the primary or secondary efficacy variables. The placebo-adjusted magnitude of effect for ZD0947 (approx. 4 mL) was less than the historic data for cholinergic antagonists (approx. 20 mL). Treatment was generally safe and well tolerated.

CONCLUSIONS

The data for ZD0947 are disappointing. More studies are needed to advance the identification of novel, non-cholinergic therapies for OAB.

Newer pharmacologic options in management of overactive bladder syndrome

PURPOSE OF REVIEW

Urinary incontinence is an under-reported epidemic that currently affects an estimated 13 million people in the United States, of whom about 11 million are women, according to the National Institute of Diabetes and Digestive and Kidney Diseases (Publication No. 02-4132). Because many patients are unaware of curative options and perceive it to be an inevitable outcome of advancing age, they fail to report their symptoms and increase their risk of developing associated co-morbid disease. Failure to diagnose and treat this condition increases financial burdens on individuals, their families and health care organizations.

RECENT FINDINGS

Pharmacologic therapy of urge incontinence previously had limited treatment success because efficacious drugs were poorly tolerated, resulting in low patient compliance. Tolerance and effectiveness continue to be improved due to innovative new drugs and alternative delivery systems.

SUMMARY

The goal of this review is to update the clinician on the efficacy and the tolerability of established and investigational pharmacologic modalities of therapy.

Propiverine versus Tolterodine: Efficacy and Tolerability in Patients with Overactive Bladder

OBJECTIVES

Propiverine and tolterodine were compared with respect to efficacy, tolerability and impact on the quality of life in the treatment of patients with idiopathic detrusor overactivity.

METHODS

In a randomised, double-blind, multicentre clinical trial, patients with idiopathic detrusor overactivity were treated with 15 mg propiverine twice daily or 2mg tolterodine twice daily over a period of 28 days. The maximum cystometric capacity was determined at baseline and after 4 weeks of therapy. The difference of both values was used as the primary endpoint. Secondary endpoints were voided volume per micturition, evaluation of efficacy (by the investigator), tolerability, post void residual urine, and quality of life.

RESULTS

The mean maximum cystometric capacity increased significantly (p < 0.01) in both groups. The volume at first urge and the frequency/volume chart parameters also showed relevant improvements during treatment. 42/100 patients in the propiverine group and 43/102 in the tolterodine group experienced adverse events. The most common adverse event, dry mouth, occurred in 20 patients in the propiverine group and in 19 patients in the tolterodine group. The scores for the quality of life improved comparably in both groups.

CONCLUSION

The study demonstrates comparable efficacy, tolerability, and improvement in the quality of life of 15 mg propiverine twice-daily and 2mg tolterodine twice-daily in the treatment of the symptoms of idiopathic detrusor overactivity.

Overactive Bladder in the Elderly

Overactive bladder (OAB) is a common condition characterised by the symptoms of urinary frequency and urgency, with or without urge incontinence and nocturia. The prevalence of OAB increases markedly with age in both men and women. OAB can have a detrimental effect on physical functioning and psychological well-being, as well as significantly reducing quality of life. Antimuscarinic therapy -- with or without behavioural therapy -- represents the most common treatment for patients with OAB. Several antimuscarinic agents are currently available for the treatment of OAB in adults, including oxybutynin, tolterodine, trospium chloride, darifenacin and solifenacin. The antimuscarinics all appear to exert their clinical effect through inhibition of the bladder muscarinic receptors, but they vary both in structure and in their functional profile. While efficacy has been demonstrated in adult populations (including patients >65 years of age), few studies have been reported specifically in a geriatric population, and antimuscarinics are often underutilised in the elderly despite the marked increase in the prevalence of OAB in this age group. One explanation for this apparent underuse of an effective treatment option may be concerns about the frequency of anticholinergic adverse events, such as dry mouth; the likelihood of detrimental CNS effects, including cognitive impairment and sleep disturbances; and the potential for harmful interactions with existing pharmacotherapy. When selecting an antimuscarinic agent for the management of an elderly patient presenting with OAB, in addition to considering evidence of clinical efficacy and tolerability, issues of safety specific to an older population should be borne in mind. In particular, the likelihood of detrimental CNS effects should be considered, including cognitive impairment and sleep disturbances, secondary to anticholinergic load. Oxybutynin and tolterodine have both been associated with cognitive adverse events and effects on sleep architecture and quality. In contrast, trospium chloride and darifenacin do not appear to be associated with cognitive adverse events and trospium chloride does not negatively affect sleep architecture or quality. Biotransformation by the cytochrome P450 (CYP450) system is an important step in the activation or elimination of a large number of drugs, including oxybutynin, tolterodine, darifenacin and solifenacin, raising the possibility of clinically relevant and potentially serious drug interactions. In elderly patients, such interactions are of particular relevance given the potential for declining activity of certain members of the CYP450 family combined with decreased hepatic blood flow, which can reduce first-pass metabolism and thus the bioavailability of drugs metabolised via this route. Of the antimuscarinic agents used to treat OAB, only trospium chloride is not extensively metabolised in the liver by the CYP450 system and is excreted largely as the active parent compound in the urine. This paper provides an overview of the pathophysiology of OAB and reviews current approaches to achieving a differential diagnosis and selecting appropriate treatment for the older patient. The pharmacology and clinical effects of current medication for the treatment of OAB symptoms in patients defined by the OAB pharmacology literature as 'elderly' are also reviewed.