Broadly acting envenomation therapeutics: Candidate inhibitors of highly conserved venom toxin families

Abstract

Envenomation, the delivery of venom, typically from a bite or sting, can cause both local andsystemic effects, including tissue necrosis, coagulopathies, paralysis, and death. Despite the lifesaving efficacy of antivenoms targeting specific neurotoxins or other lethal components, venom enzyme-driven tissue damage and long-term morbidity persist. Examination of venom bioactivities across diverse animal phyla reveals certain highly conserved constituents, notably phospholipases, metalloproteinases (MPs), and pore-forming toxins (PFTs). Small-molecule inhibitors of these conserved constituents demonstrate the potential to augment antivenom approaches. In this study, six small molecules – varespladib, doxycycline, marimastat, N-acetyl-L-cysteine (NALC), copper gluconate, and sodium aurothiomalate – were evaluated individually and in combination for their ability to specifically inhibit phospholipase A2 activity, gelatinase (an MP) activity, and PFT-driven hemolytic activity from representative venoms including those of the Hawaiian box jellyfish (Alatina alata), Australian box jellyfish (Chironex fleckeri), monocled cobra (Naja kaouthia), Russell’s viper (Daboia russelii) and honeybee (Apis mellifera). Doxycycline (0.1–2.0 mM) emerged as the top-performing monotherapy, effectively inhibiting all three enzymatic activities across venoms. Combinatorial treatments, particularly doxycycline with NALC or copper gluconate, enhanced efficacy and breadth of inhibition. However, some inhibitors required concentrations near or above cytotoxic thresholds, highlighting the need for further refinement such as targeted delivery or localized application. While all venoms are complex mixtures of bioactive molecules, these studies demonstrate that targeting common class components with broadly acting inhibitors show remarkable promise in preclinical and clinical management.