Lysosomes are a critical component of eukaryotic cells, playing a role in degradation and recycling processes, signal transduction and extracellular secretion(I). Ion channels expressed on the endo-lysosomal membrane are crucial in intracellular signalling and maintaining the acidic luminal pH for optimal hydrolase activity(II). There are a number metabolic disorders, known as lysosomal storage diseases, that arise from lysosomal dysfunction(III).

The dF508 mutation represents the most common cause underlying cystic fibrosis. The resultant misfolding of the nascent cystic fibrosis transmembrane regulator (CFTR) protein and its subsequent proteasomal degradation lead to a deficiency in functional CFTR channels and Cl- efflux at the apical cell membrane in ducts throughout the body (Veit et al. 2016).

The development of Automated Patch Clamp (APC) technology over the last 20 years has
transformed the research and development process for identifying novel drugs for ion channel targets.

Nonclinical safety pharmacology studies for siRNA follow a hybrid of the small molecule (SM) guidance and biologics guidance. The Oligonucleotide Safety Working Group (OSWG) has published a series of recommendation papers for oligonucleotides, including recommendations for safety assessment, because development of oligonucleotide-based therapeutics is not addressed by regulations. This is especially true regarding the hERG assay, which is a core assay in ICH S7B for SM. While OSWG states that a hERG study is not necessary for IND submission, all approved siRNAs have submitted hERG data which are necessary for requesting a TQT waiver.

There is growing interest in automated patch-clamp (APC) assays for ligand-gated targets which are expressed throughout the peripheral and central nervous system. The Acid-Sensing Ion Channel (ASIC) family comprises combinations of ASIC1-4 proteins that form acid-activated cation-selective channels.

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.