Preliminary evidence supporting a new enzymatic debridement product for use in chronic wounds

Abstract

A new recombinant proteolytic enzyme, isolated from maggot saliva, with fibrinolytic action has been investigated through a series of non-clinical toxicology and in-vitro/in-vivo pharmacology studies to explore its potential safety and efficacy as an enzymatic debridement agent for use in chronic wounds. Studies indicate that the enzyme has a good safety profile. When locally administered, it is not detrimental to wound healing, is non-sensitising and is rapidly inactivated in the systemic circulation. Adverse effects are limited, at very high concentrations, to transient erythema at the site of application. In-vitro testing indicates that the enzyme, whilst selective for fibrin, has additional proteolytic action against collagen and elastin, with enzymatic action for all three substrates being dose dependent. In-vivo, we used an established MRSA biofilm model, in which microbiological counts were used as a surrogate for debridement efficacy. Here, we showed that higher concentrations of the enzyme in a formulated proprietary gel, significantly reduced MRSA counts over a period of 2 to 14 days, and significantly improved the vascularity of the wound at 14 days. Together, these data support the potential for this maggot-derived proteolytic enzyme as a clinically effective debriding agent.

Keywords: chronic; debridement; pharmacology; toxicology; wounds.

FIGURE 1

Residual proteolytic activity of aurase with and without incubation with 2 M excess of alpha‐2‐macroglobulin (A2M), alpha‐2‐antiplasmin (A2AP) and alpha‐1‐antitrypsin (A1AT). Error bars are mean ± SD

FIGURE 2

Reducing SDS PAGE showing aurase incubated with A1AT after 1, 2, 5, 15, 60, 240 minutes in SDS buffer

FIGURE 3

Illustrative representations of the dispersal of collagen/fibrin/elastin fAWE disks after a 7 hours incubation period, at 37°C with (LEFT) 5 mL tris‐buffer (CENTRE LEFT) 5 mL aurase solution (5 μg/mL), (CENTRE RIGHT) 5 mL aurase solution (25 μg/mL) and (RIGHT) collagenase solution (200 μg/mL)

FIGURE 4

Cumulative degradation of fluorescent artificial wound eschar (fAWE) proteins by tris‐buffer (control), Aurase 5 μg/mL, Aurase 25 μg/mL and collagenase 200 μg/mL against A, fibrin‐coumarin; B, collagen‐FITC and C, Elastin‐rhodamine. *P < .05; **P < .01; ***P < .0001 ****P < .0001.

FIGURE 5

MRSA USA300 Counts following treatment with aurase, placebo and untreated controls compared with baseline. □ P < .05 compared with baseline and all treatments; * P < .05 compared with baseline, placebo and untreated controls; • P < .05 compared with baseline only.

FIGURE 6

Treatment with high dose aurase (0.25 g/L) was noted to increase wound neovascularization. Morphological scores of vascularization in H&E‐stained histological sections of wounds were used for quantification. 0 = normal vascularization, 1 = discrete, 2 = moderate and 3 = high vascularity