Title: Development of epoxy-tiglianes as novel small molecule therapeutics for impaired re-epithelialisation associated with non-healing, chronic skin wounds in the aged
Funder: Dunhill Medical Trust

Abstract: Normal (acute) dermal wound healing occurs through a series of phases, to induce wound closure and restore skin barrier function. However, non-healing chronic wounds, such as venous and diabetic ulcers, represent an important source of morbidity in ageing societies and are a significant economic burden to Healthcare Providers worldwide. Indeed, chronic wounds are estimated to affect ~2-3% of the UK population, costing the NHS ~£4.5-5.1BN/p.a. [1]. These cause significant pain and disability, dramatically affecting patient quality of life [2]; with projections estimating further escalations in their prevalence as age demographics and type II diabetes rates increase worldwide [3-5]. Due to disruptions in skin barrier integrity, chronic wounds are commonly characterised by bacterial colonisation/infection, contributing to perpetual inflammation and altered keratinocyte/fibroblast repair capabilities, culminating in impaired wound re-epithelialisation and closure [6-7]. Despite many chronic wound treatment modalities being available, these often offer limited benefit to healing outcomes and consequently, non-healing or recurrence remain common. Thus, there remains a significantly unmet clinical need for more efficacious therapies, capable of restoring normal healing responses in chronic wounds [8]. Epoxy-tiglianes are a novel class of diterpene esters isolated from native Australian rainforest plant, Fontainea picrosperma. Prototype epoxy-tigliane, EBC-46 (tigilanol tiglate), possesses potent anti-cancer properties, mediated via protein kinase C (PKC) activation [9]; and is currently under clinical development as a human/veterinary anti-cancer drug for cutaneous and subcutaneous tumours. EBC-46 also stimulates exceptional dermal wound healing in vivo post-tumour destruction, particularly manifested as accelerated wound re-epithelialisation and closure, 1-month post-treatment [10-11]. These studies provide compelling proof-of-concept data supporting further assessment of epoxy-tiglianes as therapeutics for other clinical situations associated with impaired re-epithelialisation, such as chronic wounds. We have previously confirmed that EBC-46 and analogues (e.g. EBC-211, EBC-1013) stimulate significant proliferation and migration by human immortalised keratinocytes (HaCaTs) in vitro, mediated via PKC activation and differential keratin, cell cycle/proliferation, migratory, differentiation, proteinase and cytokine/chemokine gene expression. Patents relating to this work are filed and manuscript submitted (Biochemical Pharmacology; see supplementary Figures, Appendix I). We will now undertake complementary studies to confirm epoxy-tigliane (EBC-46, EBC-1013) wound healing responses in primary human keratinocytes, more representative of in vivo epithelial repair. As veterinary studies have only provided qualitative macroscopic confirmation of wound healing efficacy to date, we also aim to obtain quantitative macroscopic/microscopic histological data on topically-applied, epoxy-tigliane efficacies in promoting wound re-epithelialisation and other key healing parameters, using the established in vivo (db/db mouse) impaired wound healing model.

Lay abstract: Normal healing in skin occurs through many different stages, allowing wounds to close. However, an inability for wounds to heal properly can lead to the formation of chronic wounds, such as venous and diabetic ulcers. As doctors often find these wounds difficult to treat, they cause significant pain and disability in patients, especially in older people where these wounds are particularly common and who may suffer with these wounds for many years. Therefore, chronic wounds dramatically affect patients’ physical and psychological quality of life. Chronic wounds are also extremely expensive to treat, costing the NHS approximately £4.5-5.1 billion per year. In chronic wounds, we know that the keratinocyte cells responsible for healing wounds do not perform their functions as effectively as they should. This situation is worsened by existing therapies being unsatisfactory for the treatment of all chronic wounds. As no effective therapies currently exist, there is a significant need to develop new and improved treatments for non-healing chronic wounds in skin. With collaborators in Australia, we are developing a new class of naturally occurring chemicals (epoxy-tiglianes) isolated from seeds from certain trees found in the Queensland Tropical Rainforest, which have potent anti-cancer properties in skin. Studies have also shown that these chemicals accelerate the healing and closure of wounds remaining after tumours have been cured. Our recent work has shown that epoxy-tiglianes have significant beneficial effects by enhancing the wound healing functions of ‘keratinocyte-like’ cells, potentially explaining the faster healing seen in treated skin. We now wish to use laboratory methods to confirm whether epoxy-tiglianes can induce stimulatory effects on wound healing functions in ‘true’ keratinocytes, exactly like those found in skin; and identify how epoxy-tiglianes achieves these beneficial effects. In addition, we wish to use an animal model with an inability to heal properly similar to chronic wounds in humans, to further analyse how epoxy-tiglianes alter keratinocyte cell and other wound healing functions to promote the closure of treated wounds. These studies will also help us determine the best epoxy-tiglianes and doses to use in future human studies. By confirming epoxy-tigliane effectiveness in promoting healing in treated skin, we can develop these chemicals as new treatments for non-healing chronic wounds, especially in older patients where these wounds are more prevalent. By achieving these aims, we will undoubtedly help Healthcare Providers and patients worldwide, by allowing doctors to treat their patients more effectively, so improving patient quality of life.

Research activity codes: 5.1 PHARMACEUTICALS
Health categories: SKIN