Ivabradine: A Unique and Intriguing Medication for Treating Cardiovascular Disease

Seven-membered N-heterocycles as approved drugs and promising leads in medicinal chemistry as well as the metal-free domino access to their scaffolds

Azepanes or azepines are structural motifs of many drugs, drug candidates and evaluated lead compounds. Even though compounds having N-heterocyclic 7-membered rings are often found in nature (e.g. alkaloids), the natural compounds of this group are rather rare as approved therapeutics. Thus, recently studied and approved azepane or azepine-congeners predominantly consist of semi-synthetically or synthetically-obtained scaffolds. In this review a comparison of approved drugs and recently investigated leads was proposed taking into regard their structural aspects (stereochemistry), biological activities, pharmacokinetic properties and confirmed molecular targets. The 7-membered N-heterocycles reveal a wide range of biological activities, not only against CNS diseases, but also as e.g. antibacterial, anticancer, antiviral, antiparasitic and against allergy agents. As most of the approved or investigated potential drugs or lead structures, belonging to 7-membered N-heterocycles, are synthetic scaffolds, this report also reveals different and efficient metal-free cascade approaches useful to synthesize both simple azepane or azepine-containing congeners and those of oligocyclic structures. Stereochemistry of azepane/azepine fused systems, in view of biological data and binding with the targets, is discussed. Apart from the approved drugs, we compare advances in SAR studies of 7-membered N-heterocycles (mainly from 2018 to 2023), whereas the related synthetic part concerning various domino strategies is focused on the last ten years.

Mechanisms of current therapeutic strategies for heart failure: more questions than answers?

Heart failure (HF) is a complex, multifactorial and heterogeneous syndrome with substantial mortality and morbidity. Over the last few decades, numerous attempts have been made to develop targeted therapies that may attenuate the known pathophysiological pathways responsible for causing the progression of HF. However, therapies developed with this objective have sometimes failed to show benefit. The pathophysiological construct of HF with numerous aetiologies suggests that interventions with broad mechanisms of action which simultaneously target more than one pathway maybe more effective in improving the outcomes of patients with HF. Indeed, current therapeutics with clinical benefits in HF have targeted a wider range of intermediate phenotypes. Despite extensive scientific breakthroughs in HF research recently, questions persist regarding the ideal therapeutic targets which may help achieve maximum benefit. In this review, we evaluate the mechanism of action of current therapeutic strategies, the pathophysiological pathways they target and highlight remaining knowledge gaps regarding the mode of action of these interventions.

Ivabradine Overdose in a Newborn: Precautions of Dispensing in Infants

Ivabradine is currently approved to reduce heart rate in children with chronic heart failure and dilated cardiomyopathy. Ivabradine has also been used off-label in children to treat automatic tachyarrhythmias such as ectopic atrial tachycardia and junctional ectopic tachycardia. Adverse effects of ivabradine at physiological doses as well as its toxicity at supra-physiological doses have rarely been reported in adults. In children, weight-based dosing requires dilution of commercially available ivabradine oral solution for accuracy. We describe a case of ivabradine overdose in a newborn (treated for ectopic atrial tachycardia) secondary to inaccurate dosing leading to the infant receiving 10 times more drug than prescribed. This case highlights potential pitfalls of ivabradine prescription and preparation in children.

Repurposing hyperpolarization-activated cyclic nucleotide-gated channels as a novel therapy for breast cancer

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are members of the voltage-gated cation channel family known to be expressed in the heart and central nervous system. Ivabradine, a small molecule HCN channel-blocker, is FDA-approved for clinical use as a heart rate-reducing agent. We found that HCN2 and HCN3 are overexpressed in breast cancer cells compared with normal breast epithelia, and the high expression of HCN2 and HCN3 is associated with poorer survival in breast cancer patients. Inhibition of HCN by Ivabradine or by RNAi, aborted breast cancer cell proliferation in vitro and suppressed tumour growth in patient-derived tumour xenograft models established from triple-negative breast cancer (TNBC) tissues, with no evident side-effects on the mice. Transcriptome-wide analysis showed enrichment for cholesterol metabolism and biosynthesis as well as lipid metabolism pathways associated with ER-stress following Ivabradine treatment. Mechanistic studies confirmed that HCN inhibition leads to ER-stress, in part due to disturbed Ca2+ homeostasis, which subsequently triggered the apoptosis cascade. More importantly, we investigated the synergistic effect of Ivabradine and paclitaxel on TNBC and confirmed that both drugs acted synergistically in vitro through ER-stress to amplify signals for caspase activation. Combination therapy could suppress tumour growth of xenografts at much lower doses for both drugs. In summary, our study identified a new molecular target with potential for being developed into targeted therapy, providing scientific grounds for initiating clinical trials for a new treatment regimen of combining HCN inhibition with chemotherapy.

Sympathetic Outflow Disturbance After Posterior Deformity Correction: A Rare Complication

INTRODUCTION

Sympathetic system injury is a known but rare complication in scoliosis deformity correction. It is not common following posterior correction. We report a case of diastematomyelia with neuromuscular scoliosis with unusual complication of sympathetic outflow disturbance, after posterior instrumented correction.

CASE DESCRIPTION

A 13-year-old girl presented with complaints of deformity in the back first noticed 4 years ago. Roentgenogram revealed a right thoracolumbar kyphoscoliotic deformity of 105° with apex at T8 with non-structural lumbar and cervicothoracic curves with positive sagittal alignment. Magnetic resonance imaging showed split-cord malformation with bony crest near the apex of the curve. Detethering followed by removal of the bony crest and restoration of the dual dural sleeves of the split cord into single neural tube was done in the first stage. In the second stage, pedicle screw fixation with was done from D3 to L3. Deformity correction was achieved using multilevel Smith Peterson osteotomy and concave rib osteotomy. On the second postoperative day, intensive care unit staff noticed persistent sinus tachycardia and profuse sweating in both upper limbs, chest, and upper-back. Twenty-four-hour Holter monitoring did not reveal any abnormality. Patient improved gradually and was discharged on postoperative day 9 when both sinus tachycardia and hyperhidrosis resolved.

CONCLUSIONS

Sympathetic chain disturbances after surgery recover with time. The exact time duration needed for recovery is not yet defined, however. Spine surgeons should be aware of this postsurgical complication and identify it so that management can be initiated. The symptoms may be long and drawn out, thus the roles of communication with and counseling of the patient as cannot be underemphasized.

Pharmacology of Ivabradine and the Effect on Chronic Heart Failure

Chronic Heart Failure (CHF) is a complex clinical syndrome with a high incidence worldwide. Although various types of pharmacological and device therapies are available for CHF, the prognosis is not ideal, for which, the control of increased Heart Rate (HR) is critical. Recently, a bradycardic agent, ivabradine, is found to reduce HR by inhibiting the funny current (If). The underlying mechanism states that ivabradine can enter the Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channels and bind to the intracellular side, subsequently inhibiting the If. This phenomenon can prolong the slow spontaneous phase in the diastolic depolarization, and thus, reduce HR. The clinical trials demonstrated the significant effects of the drug on reducing HR and improving the symptoms of CHF with fewer adverse effects. This review primarily introduces the chemical features and pharmacological characteristics of ivabradine and the mechanism of treating CHF. Also, some expected therapeutic effects on different diseases were also concluded. However, ivabradine, as a typical If channel inhibitor, necessitates additional research to verify its pharmacological functions.

New Novel Treatment Approaches for Heart Failure With Reduced Ejection Fraction

Despite availability of standardized drug therapies with proven beneficial outcomes, heart failure is associated with poor quality of life, increased hospital readmission, and high mortality rate. In the recent years, comprehensive understanding of the pathophysiological mechanisms of heart failure has led to the development and approval of 2 new pharmacological agents, sacubitril–valsartan and ivabradine. These agents are currently approved for use in heart failure with reduced ejection fraction (HFrEF) and present as novel approaches to further improve prognosis and outcomes in patients with HF. They offer alternative treatment options for patients who are intolerant or continue to be symptomatic despite utilization of standard HF drug therapies at optimally tolerated dosages. A review of these 2 novel agents in HFrEF, including information on pivotal trials that led to its approval and its place in therapy for HFrEF, is presented.

Heart rate lowering treatment leads to a reduction in vulnerable plaque features in atherosclerotic rabbits

Objective

To investigate the effect of a heart rate (HR) lowering agent (Ivabradine) on features of atherosclerotic plaque vulnerability with magnetic resonance imaging (MRI), ultrasound imaging, and histology.

Approach and results

Atherosclerosis was induced in the abdominal aorta of 19 rabbits. Nine rabbits were treated with Ivabradine (17 mg/kg/day) during the entire study period. At week 14, imaging was performed. Plaque size was quantified on contrast-enhanced T1-weighted MR images. Microvascular flow, density, and permeability was studied with dynamic contrast-enhanced MRI. Plaque biomechanics was studied by measuring the aortic distension with ultrasound. After, animals were sacrificed and histology was performed.

HR was reduced by 16% (p = 0.026) in Ivabradine-treated animals. No differences in absolute and relative vessel wall beat-to-beat distension were found, but due to the reduction in HR, the frequency of the biomechanical load on the plaque was reduced. Plaque size (MR and histology) was similar between groups. Although microvessel density (histology) was similar between groups, AUC and K^trans, indicative for plaque microvasculature flow, density, and permeability, were decreased by 24% (p = 0.029) and 32% (p = 0.037), respectively. Macrophage content (relative RAM11 positive area) was reduced by 44% (p<0.001) on histology in Ivabradine-treated animals.

Conclusions

HR lowering treatment with Ivabradine in an atherosclerotic rabbit model is associated with a reduction in vulnerable plaque features. The current study suggests that HR reduction may be beneficial for inducing or maintaining a more stable plaque phenotype.

Acute on Chronic Ivabradine Overdose: a Case Report

Ivabradine is a newly approved medication which reduces the heart rate by antagonizing the If channel. We report a case of intentional overdose on ivabradine. A 26-year-old female presented after taking 250 mg ivabradine. On arrival, her vital signs and neurologic exam were unremarkable. Within 30 min, her heart rate decreased to 31 bpm, but she remained normotensive with no change in mentation. Her bradycardia resolved after treatment with atropine. She experienced two further bradycardic episodes responsive to atropine; the second episode was associated with hypotension, responsive to a fluid bolus. For the remainder of her hospitalization, she remained hemodynamically stable without further interventions. She was dispositioned to the psychiatry service approximately 36 h post-ingestion with a heart rate of 67 bpm. Laboratory analysis confirmed a serum ivabradine concentration of 525 ng/mL, greater than 50 times the mean level in therapeutic trials. Proposed treatments for ivabradine include activated charcoal, atropine, isoproterenol, and intravenous pacing. Further study is needed to identify ideal treatment modalities.