Preclinical validation of a repurposed metal chelator as a community-based therapeutic for hemotoxic snakebite

Abstract

Snakebite envenoming causes 138,000 deaths annually and ~400,000 victims are left with permanent disabilities. Envenoming by saw-scaled vipers (Viperidae: Echis) leads to systemic hemorrhage and coagulopathy, and represents a major cause of snakebite mortality and morbidity in Africa and Asia. The only specific treatment for snakebite, antivenom, has poor specificity, low affordability, and must be administered in clinical settings due to its intravenous delivery and high rates of adverse reactions. This requirement results in major treatment delays in resource-poor regions and impacts substantially on patient outcomes following envenoming. Here we investigated the value of metal chelators as novel community-based therapeutics for snakebite. Among the tested chelators, dimercaprol (British anti-Lewisite) and its derivative 2,3-dimercapto-1-propanesulfonic acid (DMPS), were found to potently antagonize the activity of Zn2+-dependent snake venom metalloproteinase toxins in vitro. Moreover, DMPS prolonged or conferred complete survival in murine preclinical models of envenoming against a variety of saw-scaled viper venoms. DMPS also significantly extended survival in a challenge and treat model, where drug administration was delayed post-venom injection, and the oral administration of this chelator provided partial protection against envenoming. Finally, the potential clinical scenario of early oral DMPS therapy combined with a later, delayed, intravenous dose of conventional antivenom provided prolonged protection against the lethal effects of envenoming in vivo. Our findings demonstrate that safe and affordable repurposed metal chelators effectively neutralize saw-scaled viper venoms in vitro and in vivo and highlight the great promise of DMPS as a novel, community-based, early therapeutic intervention for hemotoxic snakebite envenoming.