An integrated biophysics approach towards realisation of a new class of membrane-active anticancer therapies

Organisms are well known to produce their own antibiotic host-defence peptides that act through damaging bacterial membranes due to their different molecular composition compared to the host organism's own cells. Some of these antimicrobial peptides are also known to have anticancer properties. One particularly promising anticancer peptide is polybia MP1 (MP1) from the venom of the Brazilian wasp Paulista Polybia.

The mechanistic basis for the anticancer properties of these peptides bears similarities to their antimicrobial mode of action. Recently we showed that MP1's membrane disrupting effects were significantly amplified by two classes of lipid, PE and PS, which are present in much higher composition on the surface of cancer cells than the cells of normal tissue. Therefore, MP1 is a promising candidate peptide for development of a novel anticancer agent. This project will aim to optimise this peptide for potency and specificity to generate promising compounds for further clinical development.

Through our current understanding of its interaction mechanism and how this relates to molecular structure, we will generate a set of MP1-derived peptides with predetermined single changes in amino acid composition. These peptides will be screened for activity against model membranes with compositions representative of cancer and normal cells as well as cancer and normal cell lines. Mutations that display enhanced potency or specificity compared to MP1 will be combined in a second round of designed peptides and activity screening.

The most promising peptides from this screening phase will be taken forward for more detailed characterisation of their interactions with membranes and cells. We will use a novel approach that takes advantage of the different insights we can gain from systems of increasing complexity from minimal membrane models with simplified lipid mixtures representative of key compositional contents of the relevant cells, to membranes extracted from the relevant cells, to the cells themselves. This will allow unprecedented correlation between the detailed biophysical information obtained from model membranes to the complex biological response in whole cells. The lipid compositions of the cell lines will also be characterised, with particular interest in the compositions of membranes that are most sensitive to and those that are most resistant to peptide-induced membrane disruption.

Application of highly sensitive surface analytical and optical microscopy techniques will provide detailed insight into the nature of peptide-membrane interactions. Importantly, beyond development of an anticancer peptide, this information will contribute valuable fundamental insight into the relationship between peptide structure, membrane composition and interaction mechanism that will be of use in the development of a wide range of membrane-active peptides, including antimicrobial peptides and cell penetrating peptides.

We aim to identify the three most potent compounds that can be taken forward towards first-in-man clinical trials through full preclinical development in a project that will follow on from this one. No current anticancer drug targets the membrane of these cells. Therefore successful translation of an MP1-derived peptide would signal a new class of anticancer drug in the therapeutic arsenal against cancer. In particular we will also test the peptides' promise for use in combination with existing chemotherapeutics and investigate any synergistic effects.

Beyond the broad academic impact previously described, this project has the potential to yield significant socioeconomic benefits in the longer term. The long term vision of this project is the development of an anticancer peptide approved for use in the clinic. While the specific work in this proposal is early stage development and mechanistic understanding, we outline our strategy and commitment to developing the most promising compounds through preclinical development to first-in-man studies and eventual licensing to a pharmaceutical company in the pathways to impact. Successful translation of a novel anticancer medicine would bring economic benefit to the UK.

The pharmaceutical sector generates a large trade surplus (in excess of £2.8bn in 2013) for the UK, greater than any other industrial sector. The UK is home to two of the world's largest pharmaceutical companies in AstraZeneca and GSK as well as many others maintaining a UK presence, including Novartis, Roche and Pfizer. The most likely time for a pharmaceutical company to license a novel compound would be at a point following first-in-man studies, which would form the basis of a proposal subsequent to this one. However we will still aim to engage the pharmaceutical industry during this early stage development. Combination studies with established oncology drugs epirubicin and docetaxel will add further value. These drugs were off-patent in 2007 and 2010 respectively. While their original manufacturers Pfizer and Sanofi-Aventis still manufacture these drugs, generics are available and all IP would rest with the novel peptide entity.

Novel insights gained from the cancer lipidomics studies within this project will also be more broadly useful to the pharmaceutical industry by providing data that could reveal possible new drug targets within these cancer cells. This could be through a more in depth understanding of the differences in plasma membrane composition between "normal" cells and various cancers, or through revealing important regulatory proteins within the lipid synthesis pathway that could be targeted for therapeutic benefit.

With >350k new cancer diagnoses each year in the UK and climbing, cancer has touched the lives of nearly everyone in the UK whether it be their friends, family or a personal diagnosis. The potential to add to the therapeutic arsenal against this disease will benefit social welfare through improving treatment options for a disease that saw 163k UK deaths in 2014. In particular, anticancer peptides would target the membranes of cancer cells, a novel mode of action, different to current clinical chemotherapeutics. This may open new opportunities in combination therapies where multiple drugs simultaneously target different aspects of the cancer cell, drastically reducing the likelihood of drug resistance.

Due to the fundamental mechanistic structure-function insight into membrane-active peptides we will gain in this study, this broader new knowledge will also benefit the development of more effective antimicrobial peptides. The problem of antimicrobial resistance is one of the biggest scientific challenges of our time. Overuse of antibiotics is enhancing the rate of development of antibiotic resistant strains with, most worryingly, some strains starting to exhibit resistance to front-line antibiotics and the pipeline of new antibiotics is drying up. This raises concerns of an "antibiotic apocalypse": a post antibiotic era where public health standards drastically deteriorate such that even an infected cut could be potentially fatal. Antimicrobial peptides are natural host-defence antibiotics that target the membranes of bacteria. The prevalence of this strategy across a wide range of living organisms suggests a promising approach to development of new antibiotics that might present sterner challenges to the development of resistance through targeting the structural matrix of their membranes instead of specific receptors.