Developing a novel catalytic uncaging drug delivery system to deliver a focal therapy for post-radiotherapy tissue regeneration

Background

This project aims to develop a novel way of delivering a pharmacological therapy to radiotherapy-injured salivary glands (SGs) to stimulate their regeneration and repair. Radiotherapy is a life-saving treatment for those with HNC (550,000/year worldwide) and >75% undergo radiotherapy as part of their treatment regime. Although radiotherapy is increasingly effective in treating cancer, it also damages/destroys healthy tissues within the radiation field as a side-effect. In particular, damage to the SGs can lead to significant oral health problems, as well as difficulties in speaking, chewing and swallowing, which severely affect quality-of-life. Specifically, the saliva-producing acinar cells are destroyed, resulting in salivary dysfunction and chronic dry mouth (termed xerostomia). Patients rely solely on short-term palliative treatments which temporarily alleviate the symptoms, but do not replicate the consistency and oral protective features of saliva. To date there is no permanent, long-term cure. Our work has shown that cholinergic drugs can effectively stimulate regeneration; however, there is currently no strategy to restrict this locally to the SGs, and significant dose-limiting toxicities would occur if given systemically. 

Aims

This project represents a novel, multi-disciplinary approach, that will build upon the discovery of the Emmerson lab, that SG regeneration can be driven by cholinergic stimulation¹, coupled with the powerful new chemistry developed by the Unciti-Broceta lab, which relies on catalytic conversion of an inactive drug (prodrug) to an active drug in-situ^2-3.

This approach consists of two components:

1. An inactive derivate of the chosen drug (termed a pro-drug) is designed to be specifically activated by a palladium (Pd)-triggered catalytic reaction, which removes the pro-drug portion, leaving an active drug locally.

2. An inert and implantable polymer-based device, functionalised with Pd, is implanted into the tissue to catalyse drug conversion from pro-drug to active drug.

Cholinergic nerves are necessary for SG maintenance. However, over time following radiotherapy innervation of the SG is disrupted, leading to SG dysfunction¹. Restoration of cholinergic signalling, via cholinergic drugs, shows therapeutic promise, but such drugs have significant off-target side-effects. We have previously screened a range of cholinergic compounds for their regenerative potential in mouse SG. The student will extend this analysis and take a precision medicine approach by combining the availability of fresh human SG and our ability to culture organotypic SG slices ex vivo⁴ to explore the heterogeneic response of human SG to cholinergic stimulation. From this the student would chose a candidate compound, which can be structurally altered to a pro-drug, which will be further tested in mouse. We hypothesise that local activation of a cholinergic pro-drug will enable a focal therapy that stimulates regeneration of radiation-damaged SGs.

The PhD student will address this hypothesis via the following aims:

Aim 1: Exploring the response to cholinergic stimulation in human salivary gland organotypic slices⁴

Aim 2. Designing and synthesising a cholinergic pro-drug

Aim 3. Testing drug conversion and cell replacement in mouse salivary gland organotypic slices⁴

Aim 4. In vivo examination of drug conversion to regenerate radiation-induced SG

This would providea way of restoring SG function after cancer treatment whilst limiting systemic side-effects. Such a therapeutic option has never yet been explored for those living with the side-effects of cancer treatment but would help tackle a major clinical problem.

Training Outcomes

The student will be given training in research methods and state-of-the-art techniques, including drug synthesis and mass spectroscopy (by members of the Unciti-Broceta lab), tissue culture, immunofluorescent and transcriptional analysis (by members of the Emmerson research group), multicolour flow cytometry and confocal microscopy (by expert core facilities staff) and in vivo techniques (by dedicated veterinary staff and trainers). The student will also gain experience in scientific writing and communication through: 1) regular report writing, 2) presenting at internal seminars and journal clubs, 3) attending conferences and meetings, and 4) participating in lab and Centre-wide public engagement activities.

The student will attend both University-wide and Institute-specific training courses in generic and transferable skills, and will also be encouraged to attend specific workshops that concentrate on the professional development of postgraduates (via the University’s Institute for Academic Development programme). The student will also be supported to attend scientific meetings and conferences and to participate in career development activities, such as demonstrating/teaching and public engagement.

References

1. Emmerson, et al. Salivary glands regenerate after radiation injury through SOX2-mediated secretory cell replacement. 2018. EMBO Mol Med. PMID: 29335337

2. Adam, et al. A 5-FU Precursor Designed to Evade Anabolic and Catabolic Drug Pathways and Activated by Pd Chemistry In Vitro and In Vivo. 2022. J Med Chem. PMID: 34979089

3. Ortega-Liebana, et al. Truly-Biocompatible Gold Catalysis Enables Vivo-Orthogonal Intra-CNS Release of Anxiolytics. 2021. Angew Chem Int Ed Engl. PMID: 34730266

4. Elder, et al. Interrogating cell-cell interactions in the salivary gland via ex vivo live cell imaging. J Vis Exp. 2023. PMID: 38047566