MQ232, A Snake Toxin Derivative for Treatment of Hyponatremia and Polycystic Kidney Diseases.

BACKGROUND Vaptans were developed at the end of the previous century as V2R antagonists. Tolvaptan is the most prescribed vaptan for hyponatremia and the autosomal polycystic kidney disease (ADPKD). However, its use is not as widespread as it should be due to price issues, a narrow therapeutic window and some side effects. With the aim of discovering new efficient and safer V2R antagonists, we screened animal venoms and identified several interesting peptide toxins. Among them, MQ1 displayed such unique biological properties in that regard that it was the starting point for the development of a potential drug candidate. METHODS Human T-cell assays and bioinformatics was used to mitigate MQ1 immunogenicity risk. The MQ232 biodistribution in mice was done by positron emission tomography (PET). Pharmacodynamics, pharmacokinetics, acute and chronic toxicity tests were performed on control rats. A rat experimental model of dDAVP-induced hyponatremia, an ex vivo mice model of renal cysts and a mice orthologous model of ADPKD were used to validate MQ232 efficacy in these pathologies. RESULTS Three mutations were introduced in MQ1 to mitigate its immunogenicity risk. A fourth gain-of-function mutation was added to generate MQ232. MQ232's safety was demonstrated by a first toxic dose as high as 3,000 nmol/kg and a strong kidney organ selectivity by PET imaging, while showing almost no interaction with the liver. MQ232's efficacy was first demonstrated with an effective dose of 3 nmol/kg in a hyponatremic model, and then in polycystic kidney models on which MQ232 significantly reduced cyst growth. CONCLUSIONS We demonstrated, employing diverse translational techniques and minimizing animal use, MQ232's safety and efficacy in several rodent models of hyponatremia and ADPKD.