Table_1_The Relative Efficacy of Chemically Diverse Small-Molecule Enzyme-Inhibitors Against Anticoagulant Activities of African Spitting Cobra (Naja Species) Venoms.xlsx

African spitting cobras are unique among cobras for their potent anticoagulant venom activity arising from strong inhibition of Factor Xa. This anticoagulant effect is exerted by venom phospholipase A2 (Group I PLA2) toxins whose activity contributes to the lethality of these species. This anticoagulant toxicity is particularly problematic as it is not neutralized by current antivenoms. Previous work demonstrated this trait for Naja mossambica, N. nigricincta, N. nigricollis, and N. pallida. The present work builds upon previous research by testing across the full taxonomical range of African spitting cobras, demonstrating that N. ashei, N. katiensis, and N. nubiae are also potently anticoagulant through the inhibition of Factor Xa, and therefore the amplification of potent anticoagulant activity occurred at the base of the African spitting cobra radiation. Previous work demonstrated that the enzyme-inhibitor varespladib was able to neutralize this toxic action for N. mossambica, N. nigricincta, N. nigricollis, and N. pallida venoms. The current work demonstrates that varespladib was also able to neutralize N. ashei, N. katiensis, and N. nubiae. Thus varespladib is shown to have broad utility across the full range of African spitting cobras. In addition, we examined the cross-reactivity of the metalloprotease inhibitor prinomastat, which had been previously intriguingly indicated as being capable of neutralizing viperid venom PLA2 (Group II PLA2). In this study prinomastat inhibited the FXa-inhibiting PLA2 toxins of all the African spitting cobras at the same concentration at which it has been shown to inhibit metalloproteases, and thus was comparably effective in its cross-reactivity. In addition we showed that the metalloprotease-inhibitor marimastat was also able to cross-neutralize PLA2 but less effectively than prinomastat. Due to logistical (cold-chain requirement) and efficacy (cross-reactivity across snake species) limitations of traditional antivenoms, particularly in developing countries where snakebite is most common, these small molecule inhibitors (SMIs) might hold great promise as initial, field-based, treatments for snakebite envenoming as well as addressing fundamental limitations of antivenom in the clinical setting where certain toxin effects are unneutralized.</p

Average treatment costs of different categories of total treatment costs for each snake.

All the values are shown in percentages of total treatment costs for each snake.</p

The breakdown of total treatment costs based on the type of snake species and nature of expenses.

(A) Total treatment costs of patients bitten by different snake species. The total costs for the hospital (B), pharmacy (C), laboratory (D) and investigation (E) were also analysed individually.</p

Total average treatment costs for snakebite patients who were bitten at different times of the day/night.

The treatment costs are shown in INR and the number of patients is shown in brackets.</p

Total average treatment costs for snakebite patients who arrived at hospitals at different times following bites.

The total treatment costs are shown in INR, and the number of patients in each category was shown within the brackets.</p

A Sankey plot showing the relationships between treatment costs and various parameters analysed in this study.

RV—Russell’s viper, CO—cobra, KR—common krait, UN—unknown, NV—non-venomous snakes and SSV—saw-scaled viper.</p

Age and gender profile of snakebite patients.

(A) A graph showing the age and gender distribution of the 913 total snakebite patients included in this study. (B) The age and gender distribution of 355 Russell’s viper bite patients.</p

The relationship between the gender and age of snakebite patients and their total treatment costs.

(A) The relationship between the gender of the patient and their total treatment costs for different snake species. (B) The patient’s age and the total treatment costs for different snakebites.</p

Impact of the number of vials of antivenom used, and the length of hospital stay in snakebite treatment costs.

(A) The relationship between the number of antivenom vials received by snakebite patients and their corresponding total treatment costs for the species in question. (B) The length of hospital stay in days for snakebite patients and the corresponding total treatment costs. NA—‘not available’ indicates that for a small number of patients, accurate details are not available. (C) The number of patients arrived at the hospital at different time points following the snakebites.</p

Some of the specialist treatments given to patients who were bitten by different snakes and their total treatment costs.

The values shown are average total treatment costs presented in INR, and the values in brackets represent the number of patients who received those treatments. ICU-intensive care unit, PCV-packed red cell volume and FFP-fresh frozen plasma.</p