Vascular effects of midazolam, flumazenil, and a novel imidazobenzodiazepine MP-III-058 on isolated rat aorta.

Hypotensive influences of benzodiazepines and other GABAA receptor ligands, recognized in clinical practice, seem to stem from the existence of "vascular" GABAA receptors in peripheral blood vessels, besides any mechanisms in the central and peripheral nervous systems. We aimed to further elucidate the vasodilatatory effects of ligands acting through GABAA receptors. Using immunohistochemistry, the rat aortic smooth muscle layer was found to express GABAA γ2 and α1-5 subunit proteins. To confirm the role of "vascular" GABAA receptors, we investigated the vascular effects of standard benzodiazepines, midazolam, and flumazenil, as well as the novel compound MP-III-058. Using two-electrode voltage clamp electrophysiology and radioligand binding assays, MP-III-058 was found to have modest binding but substantial functional selectivity for α5ß3γ2 over other αxß3γ2 GABAA receptors. Tissue bath assays revealed comparable vasodilatory effects of MP-III-058 and midazolam, both of which at 100 µmol/L concentrations had efficacy similar to prazosin. Flumazenil exhibited weak vasoactivity per se, but significantly prevented the relaxant effects of midazolam and MP-III-058. These studies indicate the existence of functional GABAA receptors in the rat aorta, where ligands exert vasodilatory effects by positive modulation of the benzodiazepine binding site, suggesting the potential for further quest for leads with optimized pharmacokinetic properties as prospective adjuvant vasodilators.

Structural Analogs of the GABAkine KRM-II-81 Are Orally Bioavailable Anticonvulsants without Sedation.

To provide back-up compounds to support the development of the GABAA receptor (GABAAR) potentiator KRM-II-81, three novel analogs were designed: replacing the pyridinyl with 2'-Cl-phenyl (FR-II-60), changing the positions of the N and O atoms in the oxazole ring with addition of an ethyl group (KPP-III-34 and KPP-III-51), or substituting a Br atom for the ethynyl of KRM-II-81 (KPP-III-34). The compounds bound to brain GABAARs. Intraperitoneal administration of FR-II-60 and KPP-III-34 produced anticonvulsant activity in mice [maximal electroshock (MES)-induced seizures or 6 Hz-induced seizures], whereas KPP-III-51 did not. Although all compounds were orally bioavailable, structural changes reduced the plasma and brain (FR-II-60 and KPP-III-51) exposures relative to KRM-II-81. Oral administration of each compound produced dose-dependent increases in the latency for both clonic and tonic seizures and the lethality induced by pentylenetetrazol (PTZ) in mice. Since KPP-III-34 produced the highest brain area under the curve (AUC) exposures, it was selected for further profiling. Oral administration of KPP-III-34 suppressed seizures in corneal-kindled mice, hippocampal paroxysmal discharges in mesial temporal lobe epileptic mice, and PTZ-induced convulsions in rats. Only transient sensorimotor impairment was observed in mice, and doses of KPP-III-34 up to 500 mg/kg did not produce impairment in rats. Molecular docking studies demonstrated that all compounds displayed a reduced propensity for binding to α1His102 compared with the sedating compound alprazolam; the bromine-substituted KPP-III-34 achieved the least interaction. Overall, these findings document the oral bioavailability and anticonvulsant efficacy of three novel analogs of KRM-II-81 with reduced sedative effects. SIGNIFICANCE STATEMENT: A new non-sedating compound, KRM-II-81, with reduced propensity for tolerance is moving into clinical development. Three new analogs were orally bioavailable, produced anticonvulsant effects in rodents, and displayed low sensorimotor impairment. KPP-III-34 demonstrated efficacy in models of pharmacoresistant epilepsy. Docking studies demonstrated a low propensity for compound binding to the α1His102 residue implicated in sedation. Thus, three additional structures have been added to the list of non-sedating imidazodiazepine anticonvulsants that could serve as backups in the clinical development of KRM-II-81.

Comparative anticonvulsant activity of the GABAkine KRM-II-81 and a deuterated analog.

A series of imidazodiazepines has been developed that possess reduced sedative liabilities but retain efficacy in anticonvulsant screening models. The latest of these compounds, (5-(8-ethynyl-6-(pyridin-2-yl)-4H-benzo[f]imidazole[1,5-α][1,4]diazepin-3-yl) oxazole known as KRM-II-81) is currently awaiting advancement into the clinic. A deuterated structural analog (D5-KRM-II-81) was made as a potential backup compound and studied here in comparison to KRM-II-81. In the present study, both compounds significantly prevented seizures in mice induced by 6 Hz (44 mA) electrical stimulation without significantly altering motoric function on a rotarod after intraperitoneal administration. Both compounds also significantly prevented clonic seizures, tonic seizures, and lethality induced by pentylenetetrazol in mice when given orally. D5-KRM-II-81 had a slightly longer duration of action against clonic and tonic seizures than KRM-II-81. Oral administration of 100 mg/kg of either KRM-II-81 or D5-KRM-II-81 was significantly less disruptive of sensorimotor function in mice than diazepam (5 mg/kg, p.o.). The present report documents that D5-KRM-II-81 represents another in this series of imidazodiazepines with anticonvulsant activity at doses that do not impair sensorimotor function.

Rationalizing the binding and α subtype selectivity of synthesized imidazodiazepines and benzodiazepines at GABAA receptors by using molecular docking studies.

The pharmacological actions exerted by benzodiazepines are dependent on the discrete α protein subunits of the γ-aminobutyric acid type A receptor (GABAA R). Recent developments via a cryo-EM structure of the α1ß3γ2L GABAA R ion channel provide crucial insights into ligand efficacy and binding affinity at this subtype. We investigated the molecular interactions of diazepam and alprazolam bound GABAA R structures (6HUP and 6HUO) to determine key binding interaction domains. A halogen bond between the chlorine atoms of diazepam and alprazolam with the group on the backbone of the α1 histidine amino acid 102 is important to the positive allosteric modulatory actions of diazepam and alprazolam in the α1ß3γ2L GABAA R ion channel. In order to gain insight into α subtype selectivity we designed and synthesized close structural analogs of diazepam and alprazolam. These compounds were then docked into the recently publish cryo-EM structures of GABAA Rs (6HUP and 6HUO). This modeling along with radio-ligand binding data resulted in the conclusion that the non-classical bioisosteric replacement of the chlorine atom at C7 with an ethinyl group (compound 5) resulted in an 11-fold gain in α5 binding selectivity over the α1 subtype. Moreover, the potency of compound 5 resulted in a ligand with less sedation than diazepam, while still maintaining the same anxiolytic potency. These modeling data extend our understanding of the structural requirements for α-subtype-selective compounds that can be utilized to achieve improved medical treatments. It is clear that the ethinyl group in place of a halogen atom decreases the affinity and efficacy of benzodiazepines and imidazodiazepines at α1 subtypes, which results in less sedation and ataxia.

Metabolism, pharmacokinetics, and anticonvulsant activity of a deuterated analog of the α2/3-selective GABAkine KRM-II-81.

The imidazodiazepine, (5-(8-ethynyl-6-(pyridin-2-yl)-4H-benzo [f]imidazole[1,5-α][1,4]diazepin-3-yl) oxazole or KRM-II-81) is a new α2/3-selective GABAkine (gamma aminobutyric acid A receptor potentiator) with anticonvulsant, anxiolytic, and antinociceptive activity in preclinical models. Reducing metabolism was utilized as a means of potentially extending the half-life of KRM-II-81. In vitro and in vivo studies were conducted to evaluate metabolic liabilities. Incubation of KRM-II-81 in hepatocytes revealed sites of potential metabolism on the oxazole and the diazepine rings. These sites were targeted in the design of a deuterated analog (D5-KRM-II-81) that could be evaluated as a potentially longer-acting analog. In contrast to computer predictions, peak plasma concentrations of D5-KRM-II-81 in rats were not significantly greater than those produced by KRM-II-81 after oral administration. Furthermore, brain disposition of KRM-II-81 was higher than that of D5-KRM-II-81. The half-life of the two compounds in either plasma or brain did not statistically differ from one another but the tmax for D5-KRM-II-81 occurred slightly earlier than for KRM-II-81. Non-metabolic considerations might be relevant to the lack of increases in exposure by D5-KRM-II-81. Alternative sites of metabolism on KRM-II-81, not targeted by the current deuteration process, are also possible. Despite its lack of augmented exposure, D5-KRM-II-81, like KRM-II-81, significantly prevented seizures induced by pentylenetetrazol when given orally. The present findings introduce a new orally active anticonvulsant GABAkine, D5-KRM-II-81.

Completion of the Total Synthesis of Several Bioactive Sarpagine/Macroline Alkaloids including the Important NF-κB Inhibitor N4-Methyltalpinine.

The unification of the general synthetic strategy regarding the important and emerging group of C-19 methyl-substituted sarpagine/macroline alkaloids has culminated in the completion of the total synthesis of several bioactive alkaloids. Key transformations include an ACE-Cl mediated late-stage N(4)-demethylation and an anhydrous acid-mediated intramolecular quaternary hemiaminal formation between a tertiary amine and an aldehyde function to allow efficient access to several biologically important alkaloids from this group. Herein, the enantiospecific total synthesis of the first known sarpagine/macroline alkaloid with NF-κB inhibitory activity, N(4)-methyltalpinine (as a chloride salt), as well as the anticancer alkaloids talpinine, O-acetyltalpinine, and macrocarpines F-G, are described.

Synergism of AZD6738, an ATR Inhibitor, in Combination with Belotecan, a Camptothecin Analogue, in Chemotherapy-Resistant Ovarian Cancer.

Epithelial ovarian cancer remains the leading cause of mortality among all gynecologic malignancies owing to recurrence and ultimate development of chemotherapy resistance in the majority of patients. In the chemotherapy-resistant ovarian cancer preclinical model, we investigated whether AZD6738 (an ataxia telangiectasia and Rad3-related (ATR) inhibitor) could synergize with belotecan (a camptothecin analog and topoisomerase I inhibitor). In vitro, both chemotherapy-resistant and chemotherapy-sensitive ovarian cancer cell lines showed synergistic anti-proliferative activity with a combination treatment of belotecan and AZD6738. The combination also demonstrated synergistic tumor inhibition in mice with a chemotherapy-resistant cell line xenograft. Mechanistically, belotecan, a DNA-damaging agent, increased phospho-ATR (pATR) and phospho-Chk1 (pChk1) in consecutive order, indicating the activation of the DNA repair system. This consequently induced G2/M arrest in the cell cycle analysis. However, when AZD6738 was added to belotecan, pATR and pChk1 induced by belotecan alone were suppressed again. A cell cycle analysis in betotecan showed a sub-G1 increase as well as a G2/M decrease, representing the release of G2/M arrest and the induction of apoptosis. In ascites-derived primary cancer cells from both chemotherapy-sensitive and -resistant ovarian cancer patients, this combination was also synergistic, providing further support for our hypothesis. The combined administration of ATR inhibitor and belotecan proved to be synergistic in our preclinical model. This combination warrants further investigation in a clinical trial, with a particular aim of overcoming chemotherapy resistance in ovarian cancer.

Bisindole Alkaloids from the Alstonia Species: Recent Isolation, Bioactivity, Biosynthesis, and Synthesis.

Bisindoles are structurally complex dimers and are intriguing targets for partial and total synthesis. They exhibit stronger biological activity than their corresponding monomeric units. Alkaloids, including those containing C-19 methyl-substitution in their monomeric units, their synthetic derivatives, and their mismatched pairs can be attractive targets for synthesis and may unlock better drug targets. We herein discuss the isolation of bisindoles from various Alstonia species, their bioactivity, putative biosynthesis, and synthesis. The total synthesis of macralstonidine, macralstonine, O-acetylmacralstonine, and dispegatrine, as well as the partial synthesis of alstonisidine, villalstonine, and macrocarpamine are also discussed in this review. The completion of the total synthesis of pleiocarpamine by Sato et al. completes the formal synthesis of the latter two bisindoles.

Recent updates on the resistance mechanisms to epidermal growth factor receptor tyrosine kinase inhibitors and resistance reversion strategies in lung cancer.

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have led to a substantial improvement in the prognosis of lung cancer patients by explicitly targeting the activating mutations within the EGFR. Initially, patients harboring tumors with EGFR mutations show progression-free survival and improvement in the response rates toward all-generation EGFR-TKIs; however, these agents fail to deliver the intended results in the long-term due to drug resistance. Therefore, it is necessary to recognize specific cardinal mechanisms that regulate the resistance phenomenon. Understanding the intricate mechanisms underlying EGFR-TKIs resistance in lung cancer could provide cognizance for more advanced targeted therapeutics. The present review features insights into current updates on the discrete mechanisms, including secondary or tertiary mutations, parallel and downstream signaling pathways, acquiring an epithelial-to-mesenchymal transition (EMT) signature, microRNAs (miRNAs), and epigenetic alterations, which lead to intrinsic and acquired resistance against EGFR-TKIs in lung cancer. In addition, this paper also reviews current possible strategies to overcome this issue using combination treatment of recently developed MET inhibitors, allosteric inhibitors or immunotherapies, transformation of EMT, targeting miRNAs, and epigenetic alterations in intrinsic and acquired EGFR-TKIs resistant lung cancer. In conclusion, multiple factors are responsible for intrinsic and acquired resistance to EGFR-TKIs and understanding of the detailed molecular mechanisms, and recent advancements in pharmacological studies are needed to develop new strategies to overcome intrinsic and acquired EGFR-TKIs resistance in lung cancer.

Molecular mechanisms of resistance to CDK4/6 inhibitors in breast cancer: A review.

Deregulation of the cyclin D-CDK4/6-INK4-RB pathway leading to uncontrolled cell proliferation, is frequently observed in breast cancer. Currently, three selective CDK4/6 inhibitors have been FDA approved: palbociclib, ribociclib and abemaciclib. Despite promising clinical outcomes, intrinsic or acquired resistance to CDK4/6 inhibitors has limited the success of these treatments; therefore, the development of various strategies to overcome this resistance is of great importance. We highlight the various mechanisms that are directly or indirectly responsible for resistance to CDK4/6 inhibitors, categorizing them into two broad groups; cell cycle-specific mechanisms and cell cycle-nonspecific mechanisms. Elucidation of the diverse mechanisms through which resistance to CDK4/6 inhibitors occurs, may aid in the design of novel therapeutic strategies to improve patient outcomes. This review summarizes the currently available knowledge regarding mechanisms of resistance to CDK4/6 inhibitors, and possible therapeutic strategies that may overcome this resistance as well.

The potential of retinoids for combination therapy of lung cancer: Updates and future directions.

Lung cancer is the most common cancer-related death worldwide. Natural compounds have shown high biological and pharmaceutical relevance as anticancer agents. Retinoids are natural derivatives of vitamin A having many regulatory functions in the human body, including vision, cellular proliferation and differentiation, and activation of tumour suppressor genes. Retinoic acid (RA) is a highly active retinoid isoform with promising anti-lung cancer activity. The abnormal expression of retinoid receptors is associated with loss of anticancer activities and acquired resistance to RA in lung cancer. The preclinical promise has not translated to the general clinical utility of retinoids for lung cancer patients, especially those with a history of smoking. Newer retinoid nano-formulations and the combinatorial use of retinoids has been associated with lower toxicity and more favorably efficacy in both the preclinical and clinical settings. Here, we highlight epidemiological and clinical therapeutic studies involving retinoids and lung cancer. We also discuss the biological actions of retinoids in lung cancer, which include effects on cancer stem cell differentiation, angiogenesis, metastasis, and proliferative. We suggest that the use of retinoids in combination with conventional and targeted anticancer agents will broaden the utility of these potent anticancer compounds in the lung cancer clinic.

New Imidazodiazepine Analogue, 5-(8-Bromo-6-(pyridin-2-yl)-4H-benzo[f]imidazo[1,5-a][1,4]diazepin-3-yl)oxazole, Provides a Simplified Synthetic Scheme, High Oral Plasma and Brain Exposures, and Produces Antiseizure Efficacy in Mice, and Antiepileptogenic Activity in Neural Networks in Brain Slices from a Patient with Mesial Temporal Lobe Epilepsy.

KRM-II-81 (1) is an imidazodiazepine GABAA receptor (GABAAR) potentiator with broad antiseizure efficacy and a low sedative burden. A brominated analogue, DS-II-73 (5), was synthesized and pharmacologically characterized as a potential backup compound as KRM-II-81 moves forward into development. The synthesis from 2-amino-5-bromophenyl)(pyridin-2yl)methanone (6) was processed in five steps with an overall yield of 38% and without the need for a palladium catalyst. GABAAR binding occurred with a Ki of 150 nM, and only 3 of 41 screened binding sites produced inhibition ≥50% at 10 µM, and the potency to induce cytotoxicity was ≥240 mM. DS-II-73 was selective for α2/3/5- over that of α1-containing GABAARs. Oral exposure of plasma and brain of rats was more than sufficient to functionally impact GABAARs. Tonic convulsions in mice and lethality induced by pentylenetetrazol were suppressed by DS-II-73 after oral administration and latencies to clonic and tonic seizures were prolonged. Cortical slice preparations from a patient with pharmacoresistant epilepsy (mesial temporal lobe) showed decreases in the frequency of local field potentials by DS-II-73. As with KRM-II-81, the motor-impairing effects of DS-II-73 were low compared to diazepam. Molecular docking studies of DS-II-73 with the α1ß3γ2L-configured GABAAR showed low interaction with α1His102 that is suggested as a potential molecular mechanism for its low sedative side effects. These findings support the viability of DS-II-73 as a backup molecule for its ethynyl analogue, KRM-II-81, with the human tissue data providing translational credibility.

Chemically Functionalized Gold Nanosphere-Blended Nematic Liquid Crystals for Photonic Applications.

A demand for functional materials that are capable of tailoring light-emissive properties has apparently been rising nowadays substantially for their utilization in organic optoelectronic devices. Motivated by such promising characteristics, we present highly emissive as well as aggregation-induced emission (AIE) electroluminescent composite systems composed of a nematic liquid crystals (NLC) blended with polyethylene-functionalized gold nanospheres (GNSs). The major findings of this study include superior electro-optical properties such as threshold voltage reduction by around 24%. The fall time is reduced by 11.50, 30.33, 49.33, and 63.17% respectively, and rotational viscosity is reduced by 13.86, 32.77, 36.97, and 49.58% for 5.0 × 1011, 5.0 × 1012, 2.5 × 1013, and 5.0 × 1013 number of GNS-blended liquid crystal (LC) cells. The increased UV absorbance and greatly enhanced luminescence properties have been attributed to surface plasmon resonance near the surface of GNSs and AIE effect risen due to agglomeration of the capping agent with the NLC molecules respectively, and these characteristics make them suitable for new-age display applications.

Unusually isolated Staphylococcus arlettae in intra-oral sutures - Case series.

Introduction: The human oral cavity comprises various niches such as teeth, gingiva, tongue, soft and hard palate, and various dental prostheses, all inhabited by different bacterial species. Although more than 600 taxa belong to the oral cavity, identifying Staphylococcus arlettae , an incompletely understood bacterium, has been rare. Methods: Three patients who underwent periodontal flap surgeries were reported with the incidental finding of S. arlettae associated with the intra-oral sutures placed. Environmental sampling was performed, to establish the exact source of this bacterium. Results: Staphylococcus arlettae was isolated in three patients' intra-oral sutures. All environmental samples were negative for the presence of the bacterium. Conclusion: . To this date, no studies have identified such an occurrence of Staphylococcus arlettae with intra-oral sutures. Its identification in association with foreign materials, such as sutures, can be considered a potential for surgical site infections and requires further investigation.

Preclinical Platform Using a Triple-negative Breast Cancer Syngeneic Murine Model to Evaluate Immune Checkpoint Inhibitors.

BACKGROUND/AIM: To evaluate the feasibility of syngeneic mouse models of breast cancer by analyzing the efficacy of immune checkpoint inhibitors (ICIs) and potential predictive biomarkers. MATERIALS AND METHODS: To establish the murine triple-negative breast cancer (TNBC) models, JC, 4T1, EMT6, and E0771 cells were subcutaneously implanted into female syngeneic mice. When the tumor reached 50-100 mm3, each mouse model was divided into a treatment (using a murine PD-1 antibody) and a no-treatment control group. The treatment group was further divided into the responder and non-responder groups. Potential predictive biomarkers were evaluated by analyzing serum cytokines, peripheral blood T cells and tumor infiltrating immune cells. RESULTS: The EMT6 model showed the highest tumor response rate (54%, 6/11) of the syngeneic models: 4T1 (45%, 5/11), JC (40%, 4/10), or E0771 (23%, 3/13). Early changes in tumor size at 7 days post-PD-1 inhibitor treatment predicted the final efficacy of the PD-1 inhibitor. Peripheral blood CD8+ and CD4+ T cells with or without Ki67 expression at 7 days post-PD-1 inhibitor treatment were higher in the finally designated responder group than in the non-responder group. At the time of sacrifice, analyses of tumor infiltrating lymphocytes consistently supported these results. We also demonstrated that retro-orbital blood sampling procedures (baseline, 7 days post-treatment, time of sacrifice) were safe for serum cytokine analyses, suggesting that our preclinical platform may be used for biomarker research using serum cytokines. CONCLUSION: Our syngeneic mouse model of TNBC is a feasible preclinical platform to evaluate ICI efficacy combined with other drugs and predictive biomarkers in the screening process of immune-oncology drug development.

Towards precision radiation oncology: endocrine therapy response as a biomarker for personalization of breast radiotherapy.

Targeted therapies, such as endocrine therapies (ET), can exert selective pressure on cancer cells and promote adaptations that confer treatment resistance. In this study, we show that ET resistance in breast cancer drives radiation resistance through reprogramming of DNA repair pathways. We also show that pharmacological bromodomain and extraterminal domain inhibition reverses pathological DNA repair reprogramming in ET-resistant breast tumors and overcomes resistance to radiation therapy.

Clinical investigations of compounds targeting metabotropic glutamate receptors.

Pharmacological modulation of glutamate has long been considered to be of immense therapeutic utility. The metabotropic glutamate receptors (mGluRs) are potential targets for safely altering glutamate-driven excitation. Data support the potential therapeutic use of mGluR modulators in the treatment of anxiety, depression, schizophrenia, and other psychiatric disorders, pain, epilepsy, as well as neurodegenerative and neurodevelopmental disorders. For each of the three mGluR groups, compounds have been constructed that produce either potentiation or functional blockade. PET ligands for mGlu5Rs have been studied in a range of patient populations and several mGlu5R antagonists have been tested for potential efficacy in patients including mavoglurant, diploglurant, basimglurant, GET 73, and ADX10059. Efficacy with mGlu5R antagonists has been reported in trials with patients with gastroesophageal reflux disease; data from patients with Parkinson's disease or Fragile X syndrome have not been as robust as hoped. Fenobam was approved for use as an anxiolytic prior to its recognition as an mGlu5R antagonist. mGlu2/3R agonists (pomaglumated methionil) and mGlu2R agonists (JNJ-40411813, AZD 8529, and LY2979165) have been studied in patients with schizophrenia with promising but mixed results. Antagonists of mGlu2/3Rs (decoglurant and TS-161) have been studied in depression where TS-161 has advanced into a planned Phase 2 study in treatment-resistant depression. The Group III mGluRs are the least developed of the mGluR receptor targets. The mGlu4R potentiator, foliglurax, did not meet its primary endpoint in patients with Parkinson's disease. Ongoing efforts to develop mGluR-targeted compounds continue to promise these glutamate modulators as medicines for psychiatric and neurological disorders.

Mandibular Alveolar Ridge Split With Simultaneous Implant Placement: A Case Report.

Bone resorption following tooth loss is an obvious, continuous, and unpredictable process, which poses one of the greatest challenges in implant placement. The posterior regions of the jaws show more resorption compared to the anterior regions, with the mandible being affected more. Augmentation of the narrow alveolar ridge has been done using various techniques. The alveolar ridge split technique (ARST) is frequently used for the horizontal augmentation of the narrow ridge. In this case report, a 47-year-old female patient who had partial edentulism on the lower left jaw region associated with a narrow alveolar ridge was treated using the ridge split technique. A piezosurgical unit was used for splitting the ridge, followed by simultaneous implant placement. This alveolar ridge split technique is considered to be more predictable, reliable, and successful as compared to other techniques such as autogenous onlay bone graft and guided bone regeneration.

The imidazodiazepine, KRM-II-81: An example of a newly emerging generation of GABAkines for neurological and psychiatric disorders.

GABAkines, or positive allosteric modulators of γ-aminobutyric acid-A (GABAA) receptors, are used for the treatment of anxiety, epilepsy, sleep, and other disorders. The search for improved GABAkines, with reduced safety liabilities (e.g., dependence) or side-effect profiles (e.g., sedation) constituted multiple discovery and development campaigns that involved a multitude of strategies over the past century. Due to the general lack of success in the development of new GABAkines, there had been a decades-long draught in bringing new GABAkines to market. Recently, however, there has been a resurgence of efforts to bring GABAkines to patients, the FDA approval of the neuroactive steroid brexanolone for post-partum depression in 2019 being the first. Other neuroactive steroids are in various stages of clinical development (ganaxolone, zuranolone, LYT-300, Sage-324, PRAX 114, and ETX-155). These GABAkines and non-steroid compounds (GRX-917, a TSPO binding site ligand), darigabat (CVL-865), an α2/3/5-preferring GABAkine, SAN711, an α3-preferring GABAkine, and the α2/3-preferring GABAkine, KRM-II-81, bring new therapeutic promise to this highly utilized medicinal target in neurology and psychiatry. Herein, we also discuss possible conditions that have enabled the transition to a new age of GABAkines. We highlight the pharmacology of KRM-II-81 that has the most preclinical data reported. KRM-II-81 is the lead compound in a new series of orally bioavailable imidazodiazepines entering IND-enabling safety studies. KRM-II-81 has a preclinical profile predicting efficacy against pharmacoresistant epilepsies, traumatic brain injury, and neuropathic pain. KRM-II-81 also produces anxiolytic- and antidepressant-like effects in rodent models. Other key features of the pharmacology of this compound are its low sedation rate, lack of tolerance development, and the ability to prevent the development of seizure sensitization.

Combination of Abemaciclib following Eribulin Overcomes Palbociclib-Resistant Breast Cancer by Inhibiting the G2/M Cell Cycle Phase.

Breast cancer remains a leading cancer burden among women worldwide. Acquired resistance of cyclin-dependent kinase (CDK) 4/6 inhibitors occurs in almost all hormone receptor (HR)-positive subtype cases, comprising 70% of breast cancers, although CDK4/6 inhibitors combined with endocrine therapy are highly effective. CDK4/6 inhibitors are not expected to cooperate with cytotoxic chemotherapy based on the basic cytotoxic chemotherapy mode of action that inhibits rapidly proliferating cells. The palbociclib-resistant preclinical model developed in the current study investigated whether the combination of abemaciclib, CDK4/6 inhibitor with eribulin, an antimitotic chemotherapy could be a strategy to overcome palbociclib-resistant HR-positive breast cancer. The current study demonstrated that sequential abemaciclib treatment following eribulin synergistically suppressed CDK4/6 inhibitor-resistant cells by inhibiting the G2/M cell cycle phase more effectively. The current study showed the significant association of the pole-like kinase 1 (PLK1) level and palbociclib resistance. Moreover, the cumulative PLK1 inhibition in the G2/M phase by each eribulin or abemaciclib proved to be a mechanism of the synergistic effect. The synergistic antitumor effect was also supported by in vivo study. The sequential combination of abemaciclib following eribulin merits further clinical trials to overcome resistance to CDK4/6 inhibitors in HR-positive breast cancer.