Aptamer therapeutic for safe and low-cost treatment of snake bite envenomation

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Snake bite envenomation is a significant problem in the US and worldwide that can result in substantial morbidity and even death. Snake venom contains a complex mixture of toxins including neurotoxins and myotoxins, as well as toxins that disrupt normal hemostasis and can produce fatal hemorrhage. Snake venoms also include several classes of digestive and proteolytic enzymes that are responsible for the extensive local tissue destruction from snake bites that can result in permanent disability or require limb amputation. Current antivenom products consist of antibody fragments raised in horses or sheep and are generally effective at stabilizing envenomation patients, however they come with several limitations in that they are not effective against all species of N. American venomous snakes in mitigating tissue damage, and there are adverse effects such as serum sickness, hypersensitivity, and recurrent coagulopathy. In addition, antibody-based formulations have an extremely high cost, with the cost of the drug ranging from $20,000 to $40,000 per patient treatment. We propose to develop a novel antivenom therapeutic based on high-affinity aptamers, which consist of single-stranded oligodeoxynucleotides that form stem-loop structures to bind to their targets. Our proprietary X-Aptamer selection technology utilizes bead-based oligo DNA combinatorial libraries in which certain bases contain protein-like side modifications to enhance binding affinity. In this project, we will generate X-Aptamers against a set of major toxin classes found in N. American venomous snakes, to develop novel antivenom formulation with a better safety profile than current antibody-based antivenoms. Our preliminary studies have demonstrated selection of aptamers capable of neutralizing myotoxin from Southern Pacific rattlesnakes (C. o. helleri) in a hind limb paralysis model in mice. The project aims are: 1) Generate high-affinity oligonucleotide X-Aptamers against the five major classes of N. American snake venom toxins and measure the dissociation constant for each X-Aptamer and its target toxin; 2) Demonstrate in vivo efficacy of X-Aptamers against snake venom toxins and crude venom, using mouse models of hemorrhagic activity, creatine kinase activity, hind-limb paralysis, and lethality, to determine the effective dose for each aptamer; 3) Perform dose-ranging and toxicology studies in rats with the blended aptamer antivenom formulation. The completion of these studies will demonstrate safety and efficacy of a novel aptamer-based formulation which will have a strong impact and market potential in the emergency treatment of snake bite envenomation.