Science

Pioneering scientific expertise and proprietary ion channel drug discovery platform

At Autifony we are leveraging our pioneering scientific expertise and proprietary ion channel drug discovery platform to generate a pipeline of small molecule modulators that selectively target specific subtypes of ion channels.

The most advanced clinical programmes target the Kv3 (KCNC) family of voltage-gated potassium channels. At an early stage, we are exploring novel ion channel families that control neural excitability, intracellular functions (e.g. lysosomal activity), and neurovascular coupling.

Ion channels as therapeutics targets

Ion channels are vital to many physiological functions including the activity of nerves and muscles. They are membrane proteins that act as gated pathways for the movement of ions across cell membranes. Increasingly, a number of diseases have been associated with defects in ion channel function. Many of these diseases are the result of mutations in the genes encoding ion channel proteins, and they are now known as the “channelopathies”.

Ion channels – molecular structure and complexity

Ion channels consist of protein subunits that form aqueous pores across cellular lipid membranes through which charged molecules (ions), such as potassium (K⁺), sodium (Na⁺), calcium (Ca²⁺), and chloride ( Cl^–) can pass.

Voltage-gated ion channels are sensitive to changes in the electrostatic charge across the membrane, which drives conformational changes in the protein complex, allowing the channels to open and close. Other types of ion channels can be activated by different ligands, pH, stretch or temperature.

Eleven ion channel families have been identified ^{1, 2, 3}, for which structural information is increasingly available ^{4, 5}.

Biophysical properties of voltage-gated channels

1. Electrical dynamics/circuits

The structure and function of the voltage-sensor domain, ion selectivity filter, as well as gating and inactivation mechanisms of voltage-gated channels have been worked out in detail using molecular genetics and structural imaging techniques. Furthermore, cryogenic electron microscopy, which freezes the channel protein in its physiological conformation prior to imaging, has successfully resolved the structure of several voltage-gated channels at angstrom resolution ^{6, 7, 8}.

The structural elements of ion channels combine to confer a range of biophysical properties that characterise individual channels and channel families. These properties affect the:

Voltage range over which channels open and close
Speed with which this occurs
Whether or not the channels inactivate after opening
How quickly they recover from inactivation ⁹

Databases, such as Channelpedia ¹⁰ provide a useful resource to navigate amongst the > 140 ion channel proteins that have been cloned.

VGIC channels sculpt the electrical dynamics of excitable cells, and in the case of neurons, orchestrate their characteristic ability to integrate synaptic input, fire action potentials, and release neurotransmitter.

2. Physiological role in health and disease

Knowledge of the biophysical properties of a specific neuronal channel, coupled with information about its sub-cellular location (somatic, dendritic, or axonal) permits prediction of its physiological role, and how the channel might contribute to human disease ¹¹.

Given the frequent association between ion channels, cellular excitability, transmitter release in the case of neurons, and different intracellular functions (e.g. autophagy or mitochondrial activity), drugs targeting ion channels have the potential for influencing a wide range of human disorders from epilepsy, to Parkinson’s disease, to Fragile X, neuromuscular disorders, and cardiac arrhythmias.

Autifony’s focus on Kv3 ion channels – unique fast kinetic properties

Kv3 voltage-gated potassium channels (Kv3.1-Kv3.4) are activated by depolarization of the neuronal plasma membrane to potentials above -20 mV; they open rapidly during the depolarising phase of the neuronal action potential to initiate repolarisation and prevent sodium channel inactivation.

As the neuron begins to repolarise, the channels deactivate quickly and so do not contribute significantly to the after-hyperpolarisation ^{12, 13}.

These distinct properties allow the channels to terminate the action potential rapidly without compromising action potential threshold, rise time, or magnitude, and without increasing the duration of the refractory period that follows. Consequently, neurons expressing Kv3 channels can sustain action potential firing at high frequencies ¹⁴.

Kv3 subtypes – differential cell expression and tissue localisation

Kv3.1-Kv3.3 subtypes are expressed mainly in the central nervous system, whereas Kv3.4 channels are predominant in skeletal muscle and sympathetic neurons ¹⁵. Kv3.1-Kv3.3 channel subtypes are differentially expressed in corticolimbic brain areas ^{16, 17, 18}, thalamus ¹⁹, and cerebellum ²⁰. Kv3.1 and Kv3.3 channels are also expressed at high levels in auditory brainstem nuclei ^{21, 22}.

Autifony’s Kv3 ion channel research

Autifony has different structural classes of small molecules that are selective modulators of Kv3 subtypes. Early prototypical compounds, such as “AUT1” have served as research tools across several studies to examine the effects of Kv3 modulation in different excitatory cell types and/or disease models. Results from these studies demonstrate the therapeutic potential of activating specific Kv3 ion channels for the treatment of a range of diseases.

Highlights from our published research:

Selectivity of “AUT” compound research tools

Autifony has developed compounds that selectively enhance the function of Kv3.1 and Kv3.2 channels ^{23, 24}. Rosato-Siri et al. showed that one of these, AUT1, caused a leftward shift in the voltage-dependence of activation of human recombinant Kv3.1 and Kv3.2 channels. The compound also restored the ability of somatosensory cortex PV+ interneurons to fire at high frequency ²⁵.

Auditory neuron studies

Our own published studies have confirmed effects of AUT1 on the activity of neurons in the auditory brainstem consistent with Kv3 channel modulation ²⁶.

Studies by other research groups have confirmed the effects of AUT1 (“RE1”) and another Autifony compound, AUT5 (“EX15”) on recombinant Kv3 channels ²⁷. Similar to Autifony studies, others have also shown effects of these compounds on the firing of fast-spiking interneurons in rodent brain slices, in vitro ²⁸.

Fragile X syndrome studies

In a detailed study employing AUT2, El-Hassar et al. showed that this compound could restore the normal firing pattern of auditory brainstem neurons in mice carrying the Fragile X gene mutation ²⁹. They also confirmed that AUT2 could improve measures of hearing in these mice; increased sensitivity to sound (hyperacusis) is a common issue in children with Fragile X syndrome.

Alzheimer disease studies

We have published research papers showing the potential therapeutic opportunity for Kv3 modulators include a study demonstrating that AUT1 and AUT5 can rescue the deficit in interneuron firing and gamma-oscillations in mouse hippocampus exposed to beta-amyloid ³⁰, providing promise that Kv3 modulators could treat cognitive deficits in patients with Alzheimer’s disease.

Learn more about our science and clinical research studies

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