Formulation-based approach to support early drug discovery and development efforts: a case study with enteric microencapsulation dosage form development for a triarylmethane derivative TRAM-34; a novel potential immunosuppressant

KCa channel targeting impairs DNA repair and invasiveness of patient-derived glioblastoma stem cells in culture and orthotopic mouse xenografts which only in part is predictable by KCa expression levels

Prognosis of glioblastoma patients is still poor despite multimodal therapy. The highly brain-infiltrating growth in concert with a pronounced therapy resistance particularly of mesenchymal glioblastoma stem-like cells (GSCs) has been proposed to contribute to therapy failure. Recently, we have shown that a mesenchymal-to-proneural mRNA signature of patient derived GSC-enriched (pGSC) cultures associates with in vitro radioresistance and gel invasion. Importantly, this pGSC mRNA signature is prognostic for patients' tumor recurrence pattern and overall survival. Two mesenchymal markers of the mRNA signature encode for IKCa and BKCa Ca2+-activated K+ channels. Therefore, we analyzed here the effect of IKCa- and BKCa-targeting concomitant to (fractionated) irradiation on radioresistance and glioblastoma spreading in pGSC cultures and in pGSC-derived orthotopic xenograft glioma mouse models. To this end, in vitro gel invasion, clonogenic survival, in vitro and in vivo residual DNA double strand breaks (DSBs), tumor growth, and brain invasion were assessed in the dependence on tumor irradiation and K+ channel targeting. As a result, the IKCa- and BKCa-blocker TRAM-34 and paxilline, respectively, increased number of residual DSBs and (numerically) decreased clonogenic survival in some but not in all IKCa- and BKCa-expressing pGSC cultures, respectively. In addition, BKCa- but not IKCa-blockade slowed-down gel invasion in vitro. Moreover, systemic administration of TRAM-34 or paxilline concomitant to fractionated tumor irradiation increased in the xenograft model(s) residual number of DSBs and attenuated glioblastoma brain invasion and (numerically) tumor growth. We conclude, that KCa-blockade concomitant to fractionated radiotherapy might be a promising new strategy in glioblastoma therapy.

IK Channel-Independent Effects of Clotrimazole and Senicapoc on Cancer Cells Viability and Migration

Many studies highlighted the importance of the IK channel for the proliferation and the migration of different types of cancer cells, showing how IK blockers could slow down cancer growth. Based on these data, we wanted to characterize the effects of IK blockers on melanoma metastatic cells and to understand if such effects were exclusively IK-dependent. For this purpose, we employed two different blockers, namely clotrimazole and senicapoc, and two cell lines: metastatic melanoma WM266-4 and pancreatic cancer Panc-1, which is reported to have little or no IK expression. Clotrimazole and senicapoc induced a decrease in viability and the migration of both WM266-4 and Panc-1 cells irrespective of IK expression levels. Patch-clamp experiments on WM266-4 cells revealed Ca2+-dependent, IK-like, clotrimazole- and senicapoc-sensitive currents, which could not be detected in Panc-1 cells. Neither clotrimazole nor senicapoc altered the intracellular Ca2+ concentration. These results suggest that the effects of IK blockers on cancer cells are not strictly dependent on a robust presence of the channel in the plasma membrane, but they might be due to off-target effects on other cellular targets or to the blockade of IK channels localized in intracellular organelles.

Endothelial KCa channels: Novel targets to reduce atherosclerosis-driven vascular dysfunction

Elevated levels of cholesterol in the blood can induce endothelial dysfunction, a condition characterized by impaired nitric oxide production and decreased vasodilatory capacity. Endothelial dysfunction can promote vascular disease, such as atherosclerosis, where macrophages accumulate in the vascular intima and fatty plaques form that impair normal blood flow in conduit arteries. Current pharmacological strategies to treat atherosclerosis mostly focus on lipid lowering to prevent high levels of plasma cholesterol that induce endothelial dysfunction and atherosclerosis. While this approach is effective for most patients with atherosclerosis, for some, lipid lowering is not enough to reduce their cardiovascular risk factors associated with atherosclerosis (e.g., hypertension, cardiac dysfunction, stroke, etc.). For such patients, additional strategies targeted at reducing endothelial dysfunction may be beneficial. One novel strategy to restore endothelial function and mitigate atherosclerosis risk is to enhance the activity of Ca2+-activated K+ (KCa) channels in the endothelium with positive gating modulator drugs. Here, we review the mechanism of action of these small molecules and discuss their ability to improve endothelial function. We then explore how this strategy could mitigate endothelial dysfunction in the context of atherosclerosis by examining how KCa modulators can improve cardiovascular function in other settings, such as aging and type 2 diabetes. Finally, we consider questions that will need to be addressed to determine whether KCa channel activation could be used as a long-term add-on to lipid lowering to augment atherosclerosis treatment, particularly in patients where lipid-lowering is not adequate to improve their cardiovascular health.

Transition-Metal-Free Synthesis of Polyfluoro-Polyarylmethanes via Direct Cross-Coupling of Polyfluoroarenes and Benzyl Chlorides

The transition-metal-free direct cross-coupling between polyfluoroarenes and benzyl chlorides is reported. In this strategy, a variety of polyfluoro di-, tri- and tetra-arylmethanes was efficiently prepared with good to excellent yields in the presence of Mg turnings via a one-pot procedure. Significantly, this method provides a general approach for the synthesis of polyfluorinated polyarylmethanes.

Repurposing the KCa3.1 inhibitor senicapoc for Alzheimer's disease

Objective

Microglia play a pivotal role in the initiation and progression of Alzheimer's disease (AD). We here tested the therapeutic hypothesis that the Ca²⁺‐activated potassium channel KCa3.1 constitutes a potential target for treating AD by reducing neuroinflammation.

Methods

To determine if KCa3.1 is relevant to AD, we tested if treating cultured microglia or hippocampal slices with Aβ oligomer (AβO) activated KCa3.1 in microglia, and if microglial KCa3.1 was upregulated in 5xFAD mice and in human AD brains. The expression/activity of KCa3.1 was examined by qPCR, Western blotting, immunohistochemistry, and whole‐cell patch‐clamp. To investigate the role of KCa3.1 in AD pathology, we resynthesized senicapoc, a clinically tested KCa3.1 blocker, and determined its pharmacokinetic properties and its effect on microglial activation, Aβ deposition and hippocampal long‐term potentiation (hLTP) in 5xFAD mice.

Results

We found markedly enhanced microglial KCa3.1 expression/activity in brains of both 5xFAD mice and AD patients. In hippocampal slices, microglial KCa3.1 expression/activity was increased by AβO treatment, and its inhibition diminished the proinflammatory and hLTP‐impairing activities of AβO. Senicapoc exhibited excellent brain penetrance and oral availability, and in 5xFAD mice, reduced neuroinflammation, decreased cerebral amyloid load, and enhanced hippocampal neuronal plasticity.

Interpretation

Our results prompt us to propose repurposing senicapoc for AD clinical trials, as senicapoc has excellent pharmacological properties and was safe and well‐tolerated in a prior phase‐3 clinical trial for sickle cell anemia. Such repurposing has the potential to expedite the urgently needed new drug discovery for AD.

KCa3.1 Channel Modulators as Potential Therapeutic Compounds for Glioblastoma

Background

The intermediate-conductance Ca²⁺-activated K⁺ channel KCa3.1 is widely expressed in cells of the immune system such as T- and B-lymphocytes, mast cells, macrophages and microglia, but also found in dedifferentiated vascular smooth muscle cells, fibroblasts and many cancer cells including pancreatic, prostate, leukemia and glioblastoma. In all these cell types K_Ca3.1 plays an important role in cellular activation, migration and proliferation by regulating membrane potential and Ca²⁺ signaling.

Methods and Results

KCa3.1 therefore constitutes an attractive therapeutic target for diseases involving excessive proliferation or activation of one more of these cell types and researchers both in academia and in the pharmaceutical industry have developed several potent and selective small molecule inhibitors of K_Ca3.1. This article will briefly review the available compounds (TRAM-34, senicapoc, NS6180), their binding sites and mechanisms of action, and then discuss the potential usefulness of these compounds for the treatment of brain tumors based on their brain penetration and their efficacy in reducing microglia activation in animal models of ischemic stroke and Alzheimer’s disease.

Conclusion

Senicapoc, which has previously been in Phase III clinical trials, would be available for repurposing, and could be used to quickly translate findings made with other K_Ca3.1 blocking tool compounds into clinical trials.

Bacteroides fragilis polysaccharide A is necessary and sufficient for acute activation of intestinal sensory neurons

Symbionts or probiotics are known to affect the nervous system. To understand the mechanisms involved, it is important to measure sensory neuron responses and identify molecules responsible for this interaction. Here we test the effects of adding Lactobacillus rhamnosus (JB-1) and Bacteroides fragilis to the epithelium while making voltage recordings from intestinal primary afferent neurons. Sensory responses are recorded within 8 s of applying JB-1 and excitability facilitated within 15 min. Bacteroides fragilis produces similar results, as does its isolated, capsular exopolysaccharide, polysaccharide A. Lipopolysaccharide-free polysaccharide A completely mimics the neuronal effects of the parent organism. Experiments with a mutant Bacteroides fragilis devoid of polysaccharide A shows that polysaccharide A is necessary and sufficient for the neuronal effects. Complex carbohydrates have not been reported before as candidates for such signalling between symbionts and the host. These observations indicate new neuronal targets and invite further study of bacterial carbohydrates as inter-kingdom signalling molecules between beneficial bacteria and sensory neurons.

Therapeutic potential of KCa3.1 blockers: recent advances and promising trends

The Ca(2+)-activated K(+) channel K(Ca)3.1 regulates membrane potential and calcium signaling in erythrocytes, activated T and B cells, macrophages, microglia, vascular endothelium, epithelia, and proliferating vascular smooth muscle cells and fibroblasts. K(Ca)3.1 has therefore been suggested as a potential therapeutic target for diseases such as sickle cell anemia, asthma, coronary restenosis after angioplasty, atherosclerosis, kidney fibrosis and autoimmunity, where activation and excessive proliferation of one or more of these cell types is involved in the pathology. This article will review the physiology and pharmacology of K(Ca)3.1 and critically examine the available preclinical and clinical data validating K(Ca)3.1 as a therapeutic target.