Development of tumour imaging and therapy strategies utilising unengineered bacteria

The ability of systemically administered bacteria to target and replicate to high numbers within solid tumours is well established. Tumour localising bacteria can be exploited as biological vehicles for the delivery of nucleic acid, protein or therapeutic payloads to tumour sites and present researchers with a highly targeted and safe vehicle for tumour imaging and cancer therapy. This work aimed to utilise bacteria to activate imaging probes or prodrugs specifically within target tissue in order to facilitate the development of novel imaging and therapeutic strategies. The vast majority of existing bacterial-mediated cancer therapy strategies rely on the use of bacteria that have been genetically modified (GM) to express genes of interest. While these approaches have been shown to be effective in a preclinical setting, GM presents extra regulatory hurdles in a clinical context. Also, many strains of bacteria are not genetically tractably and hence cannot currently be engineered to express genes of interest. For this reason, the development of imaging and therapeutic systems that utilise unengineered bacteria for the activation of probes or drugs represents a significant improvement on the current gold standard. Endogenously expressed bacterial enzymes that are not found in mammalian cells can be used for the targeted activation of imaging probes or prodrugs whose activation is only achieved in the presence of these enzymes. Exploitation of the intrinsic enzymatic activity of bacteria allows the use of a wider range of bacteria and presents a more clinically relevant system than those that are currently in use. The nitroreductase (NTR) enzymes, found only in bacteria, represent one such option. Chapter 2 introduces the novel concept of utilising native bacterial NTRs for the targeted activation of the fluorophore CytoCy5S. Bacterial-mediated probe activation allowed for non-invasive fluorescence imaging of in vivo bacteria in models of infection and cancer. Chapter 3 extends the concept of using native bacterial enzymes to activate a novel luminescent, NTR activated probe. The use of luminescence based imaging improved the sensitivity of the system and provides researchers with a more accessible modality for preclinical imaging. It also represents an improvement over existing caged luciferin probe systems described to date. Chapter 4 focuses on the employment of endogenous bacterial enzymes for use in a therapeutic setting. Native bacterial enzymatic activity (including NTR enzymes) was shown to be capable of activating multiple prodrugs, in isolation and in combination, and eliciting therapeutic responses in murine models of cancer. Overall, the data presented in this thesis advance the fields of bacterial therapy and imaging and introduce novel strategies for disease diagnosis and treatment. These preclinical studies demonstrate potential for clinical translation in multiple fields of research and medicine.

Strategies to prevent potentially inappropriate prescribing and adverse drug reactions in older patients

INTRODUCTION: Potentially inappropriate prescribing (PIP) is a major contributor to adverse drug reactions and overall increased healthcare costs. The aim of this thesis was to identify, develop and implement strategies with the potential to prevent PIP and ADRs in older patients. METHODS: A systematic review of the qualitative literature (Meta-synthesis); A qualitative study in Irish hospitals; A randomised controlled trial (RCT) to assess the impact of an online educational module on doctors’ prescribing knowledge and confidence; Exploration of the potential for a frailty index score to enable doctors identify patients at increased risk of PIP and ADRs; Exploration of the potential for the SHiM tool to enable doctors to optimise prescribing for older patients. RESULTS: The meta-synthesis identified four key concepts: (i) Desire to please the patient; (ii) Feeling of being forced to prescribe; (iii) Tension between experience and guidelines; (iv) Prescriber fear. Similar themes also emerged from the qualitative study. In the RCT, the online educational module resulted in a highly significant 22% difference in test scores between intervention and control groups. The studies exploring the frailty index score showed a significant positive relationship between a patient’s frailty status and their likelihood of experiencing PIP/ADRs. Patients above a frailty threshold of 0.16 were at least twice as likely to experience PIP/ADRs. SHiM was found to be a useful tool in terms of reconciling patients’ medications. However, the evidence for it being capable of preventing clinically relevant adverse events was poor. CONCLUSION:Qualitative research in this thesis has proposed novel theories relating to the causative factors of PIP in older patients. In doing so, it has identified several areas for intervention and laid down a road map for future research.