We describe lead compound MIDD0301 for the oral treatment of asthma based on previously developed positive allosteric αβγ selective GABA receptor (GABAR) ligands. MIDD0301 relaxed airway smooth muscle at single micromolar concentrations as demonstrated with ex vivo guinea pig tracheal rings. MIDD0301 also attenuated airway hyperresponsiveness (AHR) in an ovalbumin murine model of asthma by oral administration. Reduced numbers of eosinophils and macrophages were observed in mouse bronchoalveolar lavage fluid without changing mucous metaplasia. Importantly, lung cytokine expression of IL-17A, IL-4, and TNF-α were reduced for MIDD0301-treated mice without changing antiinflammatory cytokine IL-10 levels. Automated patch clamp confirmed amplification of GABA induced current mediated by αβγ GABARs in the presence of MIDD0301. Pharmacodynamically, transmembrane currents of ex vivo CD4 T cells from asthmatic mice were potentiated by MIDD0301 in the presence of GABA. The number of CD4 T cells observed in the lung of MIDD0301-treated mice were reduced by an oral treatment of 20 mg/kg b.i.d. for 5 days. A half-life of almost 14 h was demonstrated by pharmacokinetic studies (PK) with no adverse CNS effects when treated mice were subjected to sensorimotor studies using the rotarod. PK studies also confirmed very low brain distribution. In conclusion, MIDD0301 represents a safe and improved oral asthma drug candidate that relaxes airway smooth muscle and attenuates inflammation in the lung leading to a reduction of AHR at a dosage lower than earlier reported GABAR ligands.
Recent studies have demonstrated that subtype-selective GABAA receptor modulators are able to relax pre-contracted human airway smooth muscle ex vivo and reduce airway hyper-responsiveness in mice upon aerosol administration. Our goal in this study was to investigate systemic administration of subtype-selective GABAA receptor modulators to alleviate bronchoconstriction in a mouse model of asthma. Expression of GABAA receptor subunits was identified in mouse lungs and the effects of α4-subunit-selective GABAAR modulators, XHE-III-74EE and its metabolite XHE-III-74A, were investigated in a murine model of asthma (ovalbumin sensitized and challenged BALB/c mice). We observed that chronic treatment with XHE-III-74EE significantly reduced airway hyper-responsiveness. In addition, acute treatment with XHE-III-74A but not XHE-III-74EE decreased airway eosinophilia. Immune suppressive activity was also shown in activated human T-cells with a reduction in IL-2 expression and intracellular calcium concentrations [Ca2+]i in the presence of GABA or XHE-III-74A, whereas XHE-III-74EE showed only partial reduction of [Ca2+]i and no inhibition of IL-2 secretion. However, both compounds significantly relaxed pre-contracted tracheal rings ex vivo. Overall, we conclude that the systemic delivery of a α4-subunit-selective GABAAR modulator shows good potential for a novel asthma therapy, however, the pharmacokinetic properties of this class of drug candidates have to be improved to enable better beneficial systemic pharmacodynamic effects.
We describe pharmacokinetic and pharmacodynamic properties of two novel oral drug candidates for asthma. Phenolic α4β3γ2 GABAAR selective compound 1 and acidic α5β3γ2 selective GABAAR positive allosteric modulator compound 2 relaxed airway smooth muscle ex vivo and attenuated airway hyperresponsiveness (AHR) in a murine model of asthma. Importantly, compound 2 relaxed acetylcholine contracted human tracheal airway smooth muscle strips. Oral treatment of compound 1 and 2 decreased eosinophils in bronchoalveolar lavage fluid in ovalbumin sensitized and challenged mice, thus exhibiting anti-inflammatory properties. Additionally, compound 1 reduced the number of lung CD4+ T lymphocytes and directly modulated their transmembrane currents by acting on GABAARs. Excellent pharmacokinetic properties were observed, including long plasma half-life (up to 15 hours), oral availability, and extremely low brain distribution. In conclusion, we report the selective targeting of GABAARs expressed outside the brain and demonstrate reduction of AHR and airway inflammation with two novel orally available GABAAR ligands.
We previously demonstrated that airway smooth muscle (ASM) cells express g-aminobutyric acid A receptors (GABA A Rs), and that GABA A R agonists acutely relax ASM. Among the GABA A R a subunits, human ASM cells express only a4 and a5, providing the opportunity for selective pharmacologic targeting. Novel GABA A R-positive allosteric modulators designed for enhanced a4/a6 subunit selectivity were synthesized using iterative computational analyses (CMD-45 and XHe-III-74). Studies using oocyte heterologous expression systems confirmed that CMD-45 and XHe-III-74 led to significantly greater augmentation of currents induced by a 3% maximal effective concentration (EC 3 ) of GABA [EC 3 ]-induced currents in oocytes expressing a4 or a6 subunits (along with b3 and g2) compared with other a subunits. CMD-45 and XHe-III-74 also led to greater ex vivo relaxation of contracted wild-type mouse tracheal rings compared with tracheal rings from GABA A R a4 subunit (Gabra4) knockout mice. Furthermore, CMD-45 and XHe-III-74 significantly relaxed precontracted human ASM ex vivo, and, at a low concentration, both ligands led to a significant leftward shift in albuterolmediated ASM relaxation. In vivo, inhaled XHe-III-74 reduced respiratory system resistance in an asthmatic mouse model. Pretreatment of human ASM cells with CMD-45 and XHe-III-74 inhibited histamine-induced increases in intracellular calcium concentrations in vitro, an effect that was lost when calcium was omitted from the extracellular buffer, suggesting that inhibition of calcium influx due to alterations in plasma membrane potential may play a role in the mechanism of ASM relaxation. Selective targeting of the GABA A R a4 subunit with inhaled ligands may be a novel therapeutic pathway to treat bronchoconstriction, while avoiding sedative central nervous system effects, which are largely mediated by a1-3 subunit-containing GABA A Rs in the brain.
The α2,3selective potentiator of GABAA receptors, KRM-II-81, reduces nociceptive-associated behaviors induced by formalin and spinal nerve ligation in rats. Pharmacology Biochemistry and Behavior.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.