title: Development of highly selective Kv1.3-blocking peptides based on the sea anemone peptide ShK.
abstract: ShK, from the sea anemone Stichodactyla helianthus, is a 35-residue disulfide-rich peptide that blocks the voltage-gated potassium channel Kv1.3 at ca. 10 pM and the related channel Kv1.1 at ca. 16 pM. We developed an analog of this peptide, ShK-186, which is currently in Phase 1b-2a clinical trials for the treatment of autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. While ShK-186 displays a >100-fold improvement in selectivity for Kv1.3 over Kv1.1 compared with ShK, there is considerable interest in developing peptides with an even greater selectivity ratio. In this report, we describe several variants of ShK that incorporate p-phophono-phenylalanine at the N-terminus coupled with internal substitutions at Gln16 and Met21. In addition, we also explored the combinatorial effects of these internal substitutions with an alanine extension at the C-terminus. Their selectivity was determined by patch-clamp electrophysiology on Kv1.3 and Kv1.1 channels stably expressed in mouse fibroblasts. The peptides with an alanine extension blocked Kv1.3 at low pM concentrations and exhibited up to 2250-fold selectivity for Kv1.3 over Kv1.1. Analogs that incorporates p-phosphono-phenylalanine at the N-terminus blocked Kv1.3 with IC50s in the low pM range and did not affect Kv1.1 at concentrations up to 100 nM, displaying a selectivity enhancement of >10,000-fold for Kv1.3 over Kv1.1. Other potentially important Kv channels such as Kv1.4 and Kv1.6 were only partially blocked at 100 nM concentrations of each of the ShK analogs.
authors.affiliation: Peptides International Inc., 11621 Electron Drive, Louisville, KY 40065, USA. mpennington@pepnet.com.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Pennington
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia. sandeep.chhabra@monash.edu.
authors.forename: Shih Chieh
authors.initials: SC
authors.lastname: Chang
authors.affiliation: Peptides International Inc., 11621 Electron Drive, Louisville, KY 40065, USA. schauhan@pepnet.com.
authors.forename: Satendra
authors.initials: S
authors.lastname: Chauhan
authors.affiliation: Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA. ruhuq@bcm.edu.
authors.forename: Redwan
authors.initials: R
authors.lastname: Huq
authors.affiliation: Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA. tajhya@bcm.edu.
authors.forename: Rajeev B
authors.initials: RB
authors.lastname: Tajhya
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia. sandeep.chhabra@monash.edu.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Chhabra
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia. ray.norton@monash.edu.
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Norton
authors.affiliation: Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA. beeton@bcm.edu.
authors.forename: Christine
authors.initials: C
authors.lastname: Beeton
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D056148:Chromatography, Reverse-Phase; D004305:Dose-Response Relationship, Drug; D020128:Inhibitory Concentration 50; D051662:Kv1.1 Potassium Channel / Q000037:antagonists & inhibitors; D051664:Kv1.3 Potassium Channel / Q000037:antagonists & inhibitors*; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology*; D012615:Sea Anemones / Q000737:chemistry* / Q000235:genetics
chemical_list: D051664:Kv1.3 Potassium Channel; D010455:Peptides; D051662:Kv1.1 Potassium Channel