Kv1.3: A Promising New Target for Autoimmune Diseases

In innovative drug discovery, an excellent therapeutic target must typically possess clear disease relevance, druggability, and a favorable safety profile simultaneously. In recent years, due to its specific expression in effector memory T cells (Tem) and its critical role in autoimmune diseases, Kv1.3 has gradually evolved from an ion channel studied in immune electrophysiology into a highly anticipated target for drug development. From natural toxin peptides to engineered peptides, and further to novel biologics such as antibodies, various Kv1.3 targeting strategies are continuously advancing, thereby driving the development of related research tools and evaluation systems.

What is Kv1.3?

Kv1.3 (Potassium voltage-gated channel subfamily A member 3) belongs to the voltage-gated potassium channel family and is one of the eight members of the Kv1 family, encoded by the KCNA3 gene. It is widely expressed in various immune cells, including T lymphocytes, macrophages, and dendritic cells, with particularly prominent expression on effector memory T cells (Tem).  Structurally, Kv1.3 is a typical tetrameric transmembrane protein. Each subunit contains six transmembrane helices (S1-S6). S1-S4 form the voltage-sensing domain (VSD), which is responsible for sensing changes in membrane potential; S5 and S6 together form the pore domain (PD), which determines the selective transport of K⁺. The four subunits assemble to form a complete, functional channel, where the four S6 helices converge on the intracellular side of the cell membrane to form an inner gate. The gate is closed when the cell is at rest, but upon membrane depolarization, the VSD undergoes conformational changes that open the gate, allowing K⁺ efflux. On the extracellular side of the pore, the S5-S6 loop region further extends to form an extracellular pore structure; this region is located at the entrance of the ion conduction pore and is the primary binding site for peptide toxins and some antibodies.

Structure of Kv1.3^[1]

Why Does Kv1.3 Affect Immune Responses and Become a Crucial Target for Autoimmune Diseases?

Kv1.3 itself does not directly regulate the expression of inflammatory cytokines; instead, it modulates Ca²⁺ signaling by maintaining the membrane potential of T cells. Upon antigen stimulation, Ca²⁺ influx mediated by CRAC (calcium release-activated calcium) channels leads to membrane depolarization, which activates the opening of Kv1.3 and promotes K⁺ efflux. This repolarizes the membrane potential, thereby maintaining the electrochemical driving force required for continuous CRAC-mediated Ca²⁺ influx. The sustained Ca²⁺ signal activates pathways such as Calcineurin-NFAT, inducing the expression of cytokines like IL-2 and IFN-γ, as well as T cell proliferation. Therefore, Kv1.3 is a crucial regulatory node for maintaining continuous T cell activation.

Tem cells upregulate Kv1.3 expression during differentiation, making them dependent on Kv1.3 to maintain Ca²⁺ signaling and effector functions. Because pathogenic memory T cells in various autoimmune diseases exhibit Tem-like characteristics, Kv1.3 has emerged as a potential therapeutic target for selectively modulating the activation of autoreactive T cells.

Expression of potassium channels during T cell activation and memory T cell generation^[2]

For example, in multiple sclerosis (MS), the high expression of Kv1.3 in Tem cells amplifies the Ca²⁺ signaling response, allowing even low-intensity stimuli to trigger abnormal T cell activation. Simultaneously, enhanced Kv1.3-related signaling can upregulate β1-integrin function, improving cell adhesion and migration capabilities, thereby promoting their entry into the central nervous system to participate in neuroinflammation and demyelinating injury.  

Upregulation of Kv1.3 enhances T cell signal transduction in multiple sclerosis^[3]

Precisely because of the relative enrichment of Kv1.3 in pathogenic Tem cells, blocking this channel holds the promise of selectively inhibiting abnormal immune responses while preserving the normal immune functions of naive T cells and central memory T cells as much as possible. This characteristic of relatively precise regulation makes Kv1.3 a vital direction in autoimmune disease drug development in recent years and is an important feature distinguishing Kv1.3 from traditional broad-spectrum immunosuppressants.

From Toxins to Antibodies: Why Are Large Molecules the Focus of R&D?

Kv1.3 is an ion channel target, and ion channels have long been considered difficult to drug. This is primarily because the Kv family has high homology, especially in the conserved pore region structure, making it difficult for small molecule drugs to balance activity and selectivity, often leading to off-target effects on other potassium channels. In contrast, large molecule drugs can recognize more complex three-dimensional conformations; thus, theoretically, their selectivity should be superior. Currently, large molecule drugs targeting Kv1.3 are mainly divided into two categories:

Natural Toxins and Their Derivative Peptides

Certain peptides derived from biological toxins such as sea anemone and scorpion venom can bind to the extracellular pore region of Kv1.3 with high affinity and exhibit good selectivity. Various engineered peptides developed on this basis have improved stability, half-life, and immunogenicity while retaining activity. This is also currently the most mature research route.  

A representative drug, ShK-186 (i.e., Dalazatide, developed by Kineta), was modified from the sea anemone toxin ShK (containing 35 amino acids). It introduces a pTyr-AEEA modification at the N-terminus and C-terminal amidation, improving its selectivity and stability while maintaining its Kv1.3 blocking capability. In a Phase 1b clinical trial, ShK-186 was generally well-tolerated in patients with mild to moderate plaque psoriasis, with adverse reactions mainly being transient, mild paresthesia. Post-treatment, inflammation-related markers decreased, and skin lesions improved; notably, most patients in the 60μg dose group experienced a decrease in their PASI scores.

Individual PASI scores following ShK-186 treatment^[4]

Antibodies and Engineered Antibody Molecules

The development of ion channel antibody technology has prompted an increasing number of studies to utilize monoclonal antibodies, nanobodies, or bispecific antibodies to target Kv1.3, aiming to improve targeting and prolong the duration of action. While this direction remains in the early stages, it has become a research hotspot. Compared to peptides, antibodies possess a longer half-life and a more mature engineering platform. Of course, due to the complex transmembrane structure and limited accessible epitopes, developing high-affinity functional antibodies remains challenging.  

One disclosed example is the nanobody A0194009G09 (developed by Sanofi/Ablynx)^[5]. Unlike ShK, which directly blocks the pore, A0194009G09 binds to an allosteric site between the extracellular turret of Kv1.3 and the VSD, promoting the channel to enter a C-type inactivated state, thereby impeding ion conduction. A0194009G09 provides a crucial structural foundation for the development of Kv1.3 antibody drugs and is currently still in preclinical research. Other companies laying out Kv1.3 antibodies include AbCellera (TetraGenetics).  

Cryo-EM density map of A0194009G09 binding to Kv1.3^[6]

Beyond small molecules, peptides, and antibodies, Kv1.3 design strategies also encompass RNA interference, nanodelivery, etc., providing new directions for improving the selectivity of Kv1.3 regulation, optimizing pharmacokinetics, and expanding into new indications.

KACTUS High-Quality Kv1.3 Full-Length Proteins

Drug development for Kv1.3 continues to explore various molecular formats, leading to an increasing demand for high-quality protein tools. Relying on its dual VLP and Nanodisc platforms, the company has achieved high-fidelity and stabilized presentation of Kv1.3, providing highly efficient support for the discovery of antibodies, peptides, and novel regulatory molecules, accelerating the druggability translation of the Kv1.3 target.

Product Data

Biotinylated Human Kv1.3 Nanodisc, His Tag captured on CM5 Chip via Streptavidin can bind Anti-Kv1.3 Antibody, hFc Tag with an affinity constant of 0.78 nM as determined in SPR assay (QC Test).

Immobilized Biotinylated Human Kv1.3 Nanodisc, His Tag at 5 μg/ml (100 μl/well) on the streptavidin precoated plate (5 μg/ml). Dose response curve for Anti-Kv1.3 Antibody, hFc Tag with the EC50 of 0.11 μg/ml determined by ELISA (QC Test).

Immobilized Human Kv1.3 VLP at 5 μg/ml (100 μl/well) on the plate. Dose response curve for Anti-Kv1.3 Antibody, hFc Tag with the EC50 of 1.4 ng/ml determined by ELISA (QC Test).

Product List

References

[1] The secret life of ion channels: Kv1.3 potassium channels and proliferation. doi: 10.1152/ajpcell.00136.2017.
[2] Kv1.3 potassium channels as a therapeutic target in multiple sclerosis. doi: 10.1517/14728220903018957.
[3] Kv1.3 Channel Up-Regulation in Peripheral Blood T Lymphocytes of Patients With Multiple Sclerosis. doi: 10.3389/fphar.2021.714841.
[4] Safety and pharmacodynamics of dalazatide, a Kv1.3 channel inhibitor, in the treatment of plaque psoriasis: A randomized phase 1b trial. doi: 10.1371/journal.pone.0180762.
[5] Kv1.3 binding immunoglobulins, CA2951443A1.
[6] Structures of the T cell potassium channel Kv1.3 with immunoglobulin modulators. doi: 10.1038/s41467-022-31285-5.