Transforming toxins into therapeutics: design, stability & delivery

RS Norton

Monash Institute of Pharmaceutical Sciences, Monash University

Kv1.3 potassium channels play a major role in the activation of effector memory T cells, which are involved in autoimmune diseases such as multiple sclerosis, type 1 diabetes mellitus and rheumatoid arthritis. Kv1.3 blockers selectively inhibit the activation of these cells and show considerable potential as therapeutics for autoimmune diseases.[1] HsTX1, from the scorpion Heterometrus spinier, is a 34-residue, C-terminally amidated peptide cross-linked by four disulfide bridges. Using docking and molecular dynamics simulations, then umbrella sampling simulations to construct the potential of mean force of the ligand and calculate the binding free energy,[2] we have designed new HsTX1 analogues with Ala, Phe, Val or Abu substitutions at position 14.[3] Functional assays confirmed the predicted selectivity gain for HsTX1[R14A] and HsTX1[R14Abu], with an affinity for Kv1.3 in the low pM range and a selectivity of more than 2,000-fold for Kv1.3 over Kv1.1.[3] The remarkable potency and selectivity for Kv1.3 make these analogues valuable leads in the development of therapeutics for autoimmune diseases. These analogues also show significant stability to proteolysis and in human plasma. We are now investigating means of delivery that avoid injection and would therefore enhance patient acceptance and compliance. The results of buccal[4-5] and pulmonary[6] delivery studies will be presented, as well as strategies for slow release of the peptide into the circulation.
References: [1] V. Chi, et al., Toxicon 2012, 59, 529. [2] M. H. Rashid, et al., PLoS One 2013, 8, e78712. [3] M. H. Rashid, et al., Sci Rep 2014, 4, 4509. [4] L. Jin, et al., J Control Release 2015, 199, 37. [5] L. Jin, et al., J. Pharm. Sci. 2016. [6] L. Jin, et al., J. Pharm. Sci. 2016, 105, 650.