Investigation of a Ca 2+ Channel α2δ Ligand for the Treatment of Interstitial Cystitis: Results of a Randomized, Double-Blind, Placebo Controlled Phase II Trial

Mechanism of Analgesia by Gabapentinoid Drugs: Involvement of Modulation of Synaptogenesis and Trafficking of Glutamate-Gated Ion Channels

Gabapentinoids have clinically been used for treating epilepsy, neuropathic pain, and several other neurologic disorders for >30 years; however, the definitive molecular mechanism responsible for their therapeutic actions remained uncertain. The conventional pharmacological observation regarding their efficacy in chronic pain modulation is the weakening of glutamate release at presynaptic terminals in the spinal cord. While the α2/δ-1 subunit of voltage-gated calcium channels (VGCCs) has been identified as the primary drug receptor for gabapentinoids, the lack of consistent effect of this drug class on VGCC function is indicative of a minor role in regulating this ion channel's activity. The current review targets the efficacy and mechanism of gabapentinoids in treating chronic pain. The discovery of interaction of α2/δ-1 with thrombospondins established this protein as a major synaptogenic neuronal receptor for thrombospondins. Other findings identified α2/δ-1 as a powerful regulator of N-methyl-D-aspartate receptor (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) by potentiating the synaptic expression, a putative pathophysiological mechanism of neuropathic pain. Further, the interdependent interactions between thrombospondin and α2/δ-1 contribute to chronic pain states, while gabapentinoid ligands efficaciously reverse such pain conditions. Gabapentin normalizes and even blocks NMDAR and AMPAR synaptic targeting and activity elicited by nerve injury. SIGNIFICANCE STATEMENT: Gabapentinoid drugs are used to treat various neurological conditions including chronic pain. In chronic pain states, gene expression of cacnα2/δ-1 and thrombospondins are upregulated and promote aberrant excitatory synaptogenesis. The complex trait of protein associations that involve interdependent interactions between α2/δ-1 and thrombospondins, further, association of N-methyl-D-aspartate receptor and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor with the C-tail of α2/δ-1, constitutes a macromolecular signaling complex that forms the crucial elements for the pharmacological mode of action of gabapentinoids.

Broaden Horizons: The Advancement of Interstitial Cystitis/Bladder Pain Syndrome

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a debilitating disease that induces mental stress, lower urinary symptoms, and pelvic pain, therefore resulting in a decline in quality of life. The present diagnoses and treatments still lead to unsatisfactory outcomes, and novel diagnostic and therapeutic modalities are needed. Although our understanding of the etiology and pathophysiology of IC/BPS is growing, the altered permeability of the impaired urothelium, the sensitized nerves on the bladder wall, and the chronic or intermittent sensory pain with inaccurate location, as well as pathologic angiogenesis, fibrosis, and Hunner lesions, all act as barriers to better diagnoses and treatments. This study aimed to summarize the comprehensive information on IC/BPS research, thereby promoting the progress of IC/BPS in the aspects of diagnosis, treatment, and prognosis. According to diverse international guidelines, the etiology of IC/BPS is associated with multiple factors, while the presence of Hunner lesions could largely distinguish the pathology, diagnosis, and treatment of non-Hunner lesions in IC/BPS patients. On the basis of the diagnosis of exclusion, the diverse present diagnostic and therapeutic procedures are undergoing a transition from a single approach to multimodal strategies targeting different potential phenotypes recommended by different guidelines. Investigations into the mechanisms involved in urinary symptoms, pain sensation, and bladder fibrosis indicate the pathophysiology of IC/BPS for further potential strategies, both in diagnosis and treatment. An overview of IC/BPS in terms of epidemiology, etiology, pathology, diagnosis, treatment, and fundamental research is provided with the latest evidence. On the basis of shared decision-making, a multimodal strategy of diagnosis and treatment targeting potential phenotypes for individual patients with IC/BPS would be of great benefit for the entire process of management. The complexity and emerging evidence on IC/BPS elicit more relevant studies and research and could optimize the management of IC/BPS patients.

Efficacy and safety of oral pharmacological and supplementary therapies in bladder pain syndrome: a systematic review

Treatment goals in bladder pain syndrome (BPS) or interstitial cystitis (IC) focusing on relieving symptoms to improve quality of life and avoiding adverse events (AEs) since curative treatment for BPS/IC is not available. The readily available pharmacologic options for BPS/IC including oral, intravesical, and transdermal therapy. The purpose of this study is to review randomized trial studies over the last 15 years examining the efficacy and safety of oral pharmacological and supplementary therapies for BPS/IC. A systematic search was conducted in PubMed and Medline Library. Only randomized-controlled trials and randomized comparative trials published between 2005 and 2020 on the efficacy and safety of oral therapies for BPS/IC were included. The keywords used were “bladder pain syndrome”, or “interstitial cystitis”, and “random” or “trial”. From 629 articles, nine were included in this review. Oral therapies included consist of cyclosporine A (CyA), amitriptyline, amitriptyline plus alpha lipoic acid (ALA) and omega-3 fatty acids (n-3 PUFA), PD-0299685, sildenafil, pentosan polysulfate sodium (PPS), AQX-1125, and hydrogen-rich water. Among retrieved trials, amitriptyline in combination with ALA and n-3 PUFA, sildenafil, and cyclosporine A proved their efficacy for BPS/IC. Sildenafil was generally well tolerated, while amitriptyline and CyA must be used with caution, the supplementation of ALA/n-3 PUFAs possibly lower dosage of amitriptyline, subsequently reduce its AEs. CyA was superior to PPS but possessed greater AEs. Further studies focusing on etiopathology and phenotype differentiation of this syndrome will greatly contribute to the development of effective therapy.

Systematic Review of Voltage-Gated Calcium Channel α2δ Subunit Ligands for the Treatment of Chronic Neuropathic Pain and Insight into Structure-Activity Relationship (SAR) by Pharmacophore Modeling

BACKGROUND

Neuropathic pain (NP) is a complex symptom related to the nerve damage. The discovery of new drugs for treating chronic NP has been continuing for several decades, while more progress is still needed to be made because of the unsatisfactory efficacy and the side effects of the currently available drugs. Among all the approved drugs for chronic NP, voltage-gated calcium channel (VGCC) α2δ subunit ligands, also known as gabapentinoids, are among the first-line treatment and represent a class of efficacious and relatively safe therapeutic agents. However, new strategies are still needed to be explored due to the unsatisfied response rate.

OBJECTIVES

To review the latest status of the discovery and development of gabapentinoids for the treatment of chronic NP by covering both the marketed and the preclinical/clinical ones. To analyze the structure-activity relationship (SAR) of gabapentinoids to facilitate the future design of structurally novel therapeutic agents targeting VGCC α2δ subunit.

METHODS

We searched PubMed Central, Embase, Cochrane Library, Web of Science, Scopus and Espacenet for the literature and patents of diabetic peripheral neuropathic pain, postherpetic neuralgia, fibromyalgia, voltage-gated calcium channel α2δ subunit and related therapeutic agents from incipient to June 10, 2021. The SAR of gabapentinoids were analyzed by pharmacophore modeling using Phase module in Schrödinger suite.

RESULTS

A variety of gabapentinoids were identified as VGCC α2δ ligands that have ever been under development for the treatment of chronic NP. Among them, four gabapentinoids are marketed, one is at the active late clinical trials, and eight have been discontinued. Pharmacophore models were generated by using Phase module in Schrödinger suite, and common pharmacophores were predicted based on pharmacophoric features and analyzed.

CONCLUSION

The latest progress of the discovery and development of gabapentinoids for the treatment of chronic NP was reviewed. Moreover, the structure-activity relationship (SAR) of gabapentinoids is analyzed by pharmacophore modeling, which will be valuable for the future design of structurally novel therapeutic agents targeting VGCC α2δ subunit.

Interventions for treating people with symptoms of bladder pain syndrome: a network meta-analysis

BACKGROUND

Bladder pain syndrome (BPS), which includes the condition of interstitial cystitis, is a poorly understood clinical condition for which patients present with varying symptoms. Management of BPS is challenging for both patients and practitioners. At present, there is no universally accepted diagnosis and diverse causes have been proposed. This is reflected in wide-ranging treatment options, used alone or in combination, with limited evidence. A network meta-analysis (NMA) simultaneously comparing multiple treatments may help to determine the best treatment options for patients with BPS.

OBJECTIVES

To conduct a network meta-analysis to assess the effects of interventions for treating people with symptoms of bladder pain syndrome (BPS).

SEARCH METHODS

We searched the Cochrane Incontinence Specialised Register, which contains trials identified from the Cochrane Central Register of Controlled Trials (CENTRAL, in the Cochrane Library), MEDLINE, MEDLINE In-Process, MEDLINE Epub Ahead of Print, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) and handsearched journals and conference proceedings (searched 11 May 2018) and the reference lists of relevant articles. We conducted a further search on 5 June 2019, which yielded four small studies that were screened for eligibility but were not incorporated into the review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs of interventions for treating adults with BPS. All types of interventions (including conservative, pharmacological and surgical) were eligible.

DATA COLLECTION AND ANALYSIS

We assessed the risk of bias of included studies using Cochrane's 'Risk of bias' tool. Primary outcomes were the number of people cured or improved, pain, frequency and nocturia. For each outcome, random-effects NMA models were fitted using WinBUGS 1.4. We monitored median odds ratios (ORs) for binary outcomes and mean differences (MDs) for continuous outcomes with 95% credible intervals (Crls). We compared results of the NMA with direct evidence from pairwise meta-analysis of head-to-head trials. We used the CINeMA tool to assess the certainty of evidence for selected treatment categories.

MAIN RESULTS

We included 81 RCTs involving 4674 people with a median of 38 participants (range 10 to 369) per RCT. Most trials compared treatment against control; few trials compared two active treatments. There were 65 different active treatments, and some comparisons were informed by direct evidence from only one trial. To simplify, treatments were grouped into 31 treatment categories by mode of action. Most studies were judged to have unclear or high risk of bias for most domains, particularly for selection and detection bias. Overall, the NMA suggested that six (proportion cured/improved), one (pain), one (frequency) and zero (nocturia) treatment categories were effective compared with control, but there was great uncertainty around estimates of effect. Due to the large number of intervention comparisons in this review, we focus on three interventions: antidepressants, pentosan polysulfate (PPS) and neuromuscular blockade. We selected these interventions on the basis that they are given 'strong recommendations' in the EAU Guidelines for management of BPS (EAU Guidelines 2019). We found very low-certainty evidence suggesting that antidepressants were associated with greater likelihood of cure or improvement compared with control (OR 5.91, 95% CrI 1.12 to 37.56), but it was uncertain whether they reduced pain (MD -1.27, 95% CrI -3.25 to 0.71; low-certainty evidence), daytime frequency (MD -2.41, 95% CrI -6.85 to 2.05; very low-certainty evidence) or nocturia (MD 0.01, 95% CrI -2.53 to 2.50; very low-certainty evidence). There was no evidence that PPS had improved cure/improvement rates (OR 0.14, 95% CrI 0.40 to 3.35; very low-certainty evidence) or reduced pain (MD 0.42, 95% CrI -1.04 to 1.91; low-certainty evidence), frequency (MD -0.37, 95% CrI -5.00 to 3.44; very low-certainty evidence) or nocturia (MD -1.20, 95% CrI -3.62 to 1.28; very low-certainty evidence). There was evidence that neuromuscular blockade resulted in greater cure or improvement (OR 5.80, 95% CrI 2.08 to 18.30) but no evidence that it improved pain (MD -0.33, 95% CrI -1.71 to 1.03), frequency (MD -0.91, 95% CrI -3.24, 1.29) or nocturia (MD -0.04, 95% CrI -1.35 to 1.27). The certainty of this evidence was always very low.

AUTHORS' CONCLUSIONS

We are uncertain whether some treatments may be effective in treating patients with BPS because the certainty of evidence was generally low or very low. Data were available for a relatively large number of trials, but most had small sample sizes and effects of treatments often could not be estimated with precision. An NMA was successfully conducted, but limited numbers of small trials for each treatment category hampered our ability to fully exploit the advantages of this analysis. Larger, more focused trials are needed to improve the current evidence base.

Recent advances in imaging and understanding interstitial cystitis

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a debilitating condition associated with intense pelvic pain and bladder storage symptoms. Since diagnosis is difficult, prevalence estimates vary with the methodology used. There is also a lack of proven imaging tools and biomarkers to assist in differentiation of IC/BPS from other urinary disorders (overactive bladder, vulvodynia, endometriosis, and prostatitis). Current uncertainty regarding the etiology and pathology of IC/BPS ultimately impacts its timely and successful treatment, as well as hampers future drug development. This review will cover recent developments in imaging methods, such as magnetic resonance imaging, that advance the understanding of IC/BPS and guide drug development.

Investigational drugs for bladder pain syndrome (BPS) / interstitial cystitis (IC)

INTRODUCTION

Bladder pain syndrome (BPS)/interstitial cystitis (IC) is associated with sensory lower urinary tract symptoms. Unfortunately, many of the existing oral treatments are ineffective in most patients of BPS/IC, which is the motivation for developing new drugs and therapeutic approaches. This review covers the latest drugs that have been investigated in BPS/IC patients. Intravesical treatments offer the opportunity to directly target the painful bladder with less systemic side effects.

AREAS COVERED

In this review, the authors analyze the existing literature supporting the treatment of BPS/IC with conventional drugs including heparin, hyaluronic acid, chondroitin sulfate, and dimethylsulfoxide (DMSO). Furthermore, investigational drugs such as tanezumab and adalimumab, capable of sequestering nerve growth factor (NGF), and Tumor necrosis factor-α (TNF- α) are discussed. Investigational treatments such as liposomes, botulinum toxin (BTX), liposomal BTX, PD-0299685 (a Ca(2+) channel ɑ2δ ligand), continuous intravesical lidocaine, and AQX-1125 (a novel SHIP1 activating compound) are also covered.

EXPERT OPINION

New investigational drugs offer promising improvements in clinical outcomes for BPS/IC patients; however, BPS/IC is a chronic pain disorder that is very vulnerable to a strong placebo effect. In addition, BPS/IC is a heterogeneous disorder that can be classified into several phenotypes. Since different phenotypes of BPS/IC respond differently to systemic and intravesical treatments, the authors believe that new drugs developed for BPS/IC are more likely to meet their predetermined clinical endpoints if the inclusion/exclusion criterion is tailored to specific phenotype of BPS/IC patients.