Acid-sensing ion channels (ASICs) are proton-gated ion channels which are highly sensitive to extracellular acidosis and are permeable to cations1, predominantly Na+. To date, six different ASIC subunits (1a, 1b, 2a, 2b, 3 and 4) encoded by four genes have been identified.
The cardiac late Na+ current (late INa) generates persistent inward currents throughout the plateau phase of the ventricular action potential and is an important determinant of repolarisation rate, EADs and arrythmia risk. As inhibition of late INa can offset drug effects on hERG and other repolarising K+ conductances it is one of the key cardiac channels in the Comprehensive in vitro Proarrythmia Assay CiPA panel being developed by the FDA to improve human clinical arrythmia risk assessment.
The FDA’s Comprehensive in vitro Proarrhythmia Assay (CiPA) initiative is designed to remove the over-reliance on hERG data to predict human clinical cardiac risk, with recent results suggesting that inclusion of additional cardiac ion channels and assays (e.g. peak and late Nav1.5, Cav1.2, dynamic hERG) improve risk predictions of in silico action potential models.
Domainex and Metrion Biosciences have formed an alliance to identify new chemical hits against ion-channel targets. Key to this collaboration are Domainex’s experience in hit identification and Metrion Bioscience’s expertise in ion channel screening and pharmacology.
Activated effector memory T-cells (TEM) have been implicated in the pathogenesis of autoimmune diseases.1 TEM cells express high levels of the voltage-gated potassium channel, Kv1.3, which plays a role in controlling the function of TEM. Inhibition of Kv1.3 reduces the release of pro-inflammatory mediators, inhibits T-cell proliferation and migration to inflamed tissues, and has been shown to ameliorate autoimmune disease symptoms in preclinical animal models.
Ion channels play a key role in regulating resting membrane potential and cell excitability and are attractive targets for therapeutic intervention.
Thallium (Tl+) flux assays, which measure the flow of Tl+ through potassium channels, offer a high throughput method for the identification of potassium channel activators.
Recent work by FDA and HESI CiPA working groups indicate that in vitro hERG, Nav1.5 and Cav1.2 potency data in addition to dynamic hERG kinetic data is required to accurately predict proarrhythmic risk.
Cardiac toxicity remains the leading cause of new drug safety side-effects. Current preclinical cardiac safety assays rely on in vitro cell-based ion channel assays and ex vivo and in vivo animal models. These assays provide an indication of acute risk but they do not always predict the effect of chronic compound exposure, as recently seen with oncology drugs.
Metrion Biosciences is a UK based CRO, located at Granta Park in Cambridge. Our team has substantial expertise in providing research services to deliver preclinical and clinical stage drug candidates, and has a proven track record of providing high quality drug discovery services to our customers for ion channel targets on a fee-for-service or collaboration basis. The Metrion team takes pride in providing a knowledgeable, collaborative and flexible service to all customers, whether for small stand alone projects or fully integrated drug discovery programmes.
Ion channels represent 15 – 20% of historic drug approvals and recent drug discovery projects. Many ion channel families (Nav, Cav, TRPx and GABA) are validated as therapeutic targets based on human genetics, animal models and selective pharmacology. However, ion channels are challenging targets requiring expert target class knowledge and specialised screening technology such as automated patch-clamp (APC) electrophysiology.