Organophosphates are toxic compounds found in chemical warfare agents, such as nerve gases, and insect pesticides.Use of volatile nerve gas agents by terrorist organizations is a key concern of governments around the world. V-type nerve agents (e.g. VX, RVX, and CVX) are particularly toxic nerve gases, with an exceptionally high potency. Although not as lethal as nerve agents, organophosphate insecticides can be harmful in large or prolonged doses. The standard therapy has limited efficacy, carry risks of serious adverse effects and have relatively short shelf life in field conditions.Bioscavengers represent a preferred to rapidly detoxify organophosphates in the blood, before they had the chance to reach its physiological targets and cause damage, but usually require the use of very high doses. The present invention provides genetically modified phosphotriesterase (PTE) variants, which serve as catalytic bioscavengers for V-type nerve agents, with exceptional detoxification activity at low doses, and improved stability.
Reduced effective doses allows to reduce adverse effects
High stability increasing shelf life
Compatible with both prophylaxis and post exposure
Compatible for both surface decontamination and administration to patients
Researchers at Prof. Tawfik lab use directed evolution to drive protein mutagenesis towards desired traits. Appling this approach, using the actual threat agents, the present inventors generated recombinant phosphotriesterase (PTE) variants with improved catalytic efficiencies towards V-type nerve agent hydrolysis. Serving as catalytic bioscavengers, these recombinant PTE variants hydrolyze organophosphates without being consumed and thus can be applied at low doses (catalytic efficiency (kcat/KM) greater than 3.106 M-1min-1).Importantly, PTE is efficient both as a prophylactic agent that may be given several hours prior to exposure as a preventive measure, and as post exposure antidote, even days after in a single or multiple-doses.It is compatible with both decontamination of surfaces and detoxification administrated to a patient by standard routes such as orally or injectables. Finally, some PTE variants show superior stability properties, retaining at least 50% of their catalytic activity at 50?C, indicating extended shelf life. This may be especially critical in field conditions, where the risk for nerve agent exposure is high.