Prolonged immunomodulation in inflammatory arthritis using the selective Kv1.3 channel blocker HsTX1[R14A] and its PEGylated analog

Abstract Effector memory T lymphocytes (T EM cells) that lack expression of CCR7 are major drivers of inflammation in a number of autoimmune diseases, including multiple sclerosis and rheumatoid arthritis. The Kv1.3 potassium channel is a key regulator of CCR7 − T EM cell activation. Blocking Kv1.3 inhibits T EM cell activation and attenuates inflammation in autoimmunity, and as such, Kv1.3 has emerged as a promising target for the treatment of T EM cell-mediated autoimmune diseases. The scorpionvenom-derived peptide HsTX1 and its analog HsTX1[R14A] are potent Kv1.3 blockers and HsTX1[R14A] is selective for Kv1.3 over closely-related Kv1 channels. PEGylationof HsTX1[R14A] to create a Kv1.3 blocker with a long circulating half-lifereduced its affinity but not its selectivity for Kv1.3, dramatically reduced its adsorption to inert surfaces, and enhanced its circulating half-lifein rats. PEG-HsTX1[R14A] is equipotent to HsTX1[R14A] in preferential inhibition of human and rat CCR7 − T EM cell proliferation, leaving CCR7 + naive and central memory T cellsable to proliferate. It reduced inflammation in an active delayed-type hypersensitivity model and in the pristane-induced arthritis (PIA) model of rheumatoid arthritis (RA). Importantly, a single subcutaneous dose of PEG-HsTX1[R14A] reduced inflammation in PIA for a longer period of time than the non- PEGylatedHsTX1[R14A]. Together, these data indicate that HsTX1[R14A] and PEG-HsTX1[R14A] are effective in a model of RA and are therefore potential therapeutics for T EM cell-mediated autoimmune diseases. PEG-HsTX1[R14A] has the additional advantages of reduced non-specific adsorption to inert surfaces and enhanced circulating half-life.