Stability and safety of inhibitor cystine knot peptide, gtx1-15, from the tarantula spider grammostola rosea

Abstract

Inhibitor cystine knot (ICK) peptides are knotted peptides with three intramolecular di-sulfide bonds that affect several types of ion channels. Some are proteolytically stable and are promising scaffolds for drug development. GTx1-15 is an ICK peptide that inhibits the voltage-dependent calcium channel Cav3.1 and the voltage-dependent sodium channels Nav1.3 and Nav1.7. As a model molecule to develop an ICK peptide drug, we investigated several important pharmaceutical char-acteristics of GTx1-15. The stability of GTx1-15 in rat and human blood plasma was examined, and no GTx1-15 degradation was observed in either rat or human blood plasma for 24 h in vitro. GTx1-15 in blood circulation was detected for several hours after intravenous and intramuscular admin-istration, indicating high stability in plasma. The thermal stability of GTx1-15 as examined by high thermal incubation and protein thermal shift assays indicated that GTx1-15 possesses high heat sta-bility. The cytotoxicity and immunogenicity of GTx1-15 were examined using the human monocytic leukemia cell line THP-1. GTx1-15 showed no cytotoxicity or immunogenicity even at high concen-trations. These results indicate that GTx1-15 itself is suitable for peptide drug development and as a peptide library scaffold.