Chemical bioreductive approaches to targeted radiosensitisation and imaging of tumours

All cells in the human body require oxygen to survive. The condition where insufficient oxygen is available, as occurs in heart attacks and strokes for example, is referred to as hypoxia.

The human body is designed to resist the formation of tumours, so any developing tumour faces many challenges, one of which is oxygen supply. Unfortunately, tumours manage to overcome this challenge and cheat the body into providing oxygen to a greater or lesser extent.

The tumour cells, which receive insufficient oxygen and experience hypoxia, adapt to this condition and in so doing become stronger and more difficult to kill.

In particular, hypoxic tumour cells are more resistant to radiotherapy than tumour cells that receive sufficient oxygen.

Clearly, as 50% off all people treated for cancer receive radiotherapy, it is important to find ways of making this treatment more effective against hypoxic tumour cells. Presently, the more hypoxic the cancer the less effective is the radiotherapy treatment.

This new work is a collaboration between the Chemistry Department and Oncology at Oxford who together have come up with a way to tackle hypoxic tumour cells.

So far, the chemists have made a drug, which can kill hypoxic tumour cells and make them more susceptible to radiotherapy, but does not harm normal cells. The biologists have tested this drug on hypoxic human cancer cells grown in the laboratory

As a next step, we would like to be able to make more of this new drug and to test it further both in the laboratory and in mice.

This kind of testing is essential if this drug is ever going to progress to being useful in combination with radiotherapy for cancer patients.

We also plan to modify the drug so that it becomes fluorescent as soon as it becomes active in hypoxic conditions. This will make the biological testing much easier as we will be able to see exactly when and where it becomes active.

In summary, the more hypoxic a tumour is the more likely it is to kill the patient. Therefore, our approach to target these cells specifically could have a major impact on patient survival.

Tumour hypoxia presents a major barrier to effective radiotherapy. We have taken a novel approach to targeting hypoxic cancer cells through the development of a molecularly targeted bioreductive drug. Our proof-of-concept compound CH-01 is a Chk1/Aurora A kinase inhibitor that only shows activity in hypoxic conditions. We have synthesised a small quantity of an improved next generation compound CH-02 and determined that it is reduced/fragmented in hypoxic conditions and also inhibits Chk1 in these situations. As a result of these positive data, we propose to scale up the synthesis of CH-02, complete the in vitro testing and progress to using it in xenograft tumour models. Our goal is to demonstrate that CH-02, in combination with radiation, is an effective was to delay tumour growth. In order to facilitate the use of this agent, and subsequent bioreductives, we have designed the compounds such that they become fluorescent in the near infrared (NIR) after bioreduction. This "switch-on" NIR fluorescence will allow us to monitor the biodistribution and activation of the prodrug during both in vitro and in vivo testing. This entirely novel approach will provide real time information on the bio-distribution of a molecularly targeted bioreductive compound for the first time. Together, our cross-disciplinary approach represents a novel strategy for the treatment of hypoxic cancers, which is likely to highly effective when combined with radiotherapy.

Academic beneficiaries
-Basic/biomedical scientists investigating hypoxia in any setting
Immediate beneficiaries of this work will be scientists investigating hypoxia. This includes those working on bacterial hypoxia and those studying tumour hypoxia. The ability to deliver a potent and selective Chk1 inhibitor selectively to hypoxia is a powerful tool for those studying the effects of Chk1 and the wider DNA damage pathway. The fluorogenic bioreductive group will be of interest to scientists investigating hypoxia in any setting. This work will provide a generally applicable tool that can deliver a compound selectively to hypoxia and simultaneously image the biodistribution. This approach is already the subject of a patent application (Conway/Hammond). 1-3 years.

-Training of highly skilled professionals
Two PDRAs will be recruited and will join a multi-disciplinary team. Both will be exposed to all aspects of the project.

Health care impact
-Clinicians treating patients with solid tumours
The work in this grant is the precursor to a full clinical study on the application of bioreductive Chk1 inhibitors as novel cancer chemotherapeutics. Our expectation is that the agents could be used in a range of tumours, thereby having an impact across a spectrum of cancers. Should our work be successful it will be the first example of a hypoxia-targeted Chk1 inhibitor as a chemotherapeutic strategy. This strategy will provide new options for clinicians treating patients with hypoxic tumours, which are typically the most difficult tumours to treat due to their resistance to chemo/radiotherapy. The ability to image the biodistribution of the therapeutic agent will be a powerful tool for assessing how effective a treatment regime is. In addition, the fluorogenic bioreductive group can be used as a companion diagnostic to determine whether a bioreductive drug is appropriate for a given patient. 5-10 years.

-Cancer patients
All cancer patients will benefit from this work. Using the fluorogenic bioreductive group as a companion diagnostic, we will be able to determine which patients will benefit from the bioreductive Chk1 inhibitor. This obviously benefits these patients as they will have access to a novel, and hopefully more effective, form of chemotherapy, with potentially fewer side effects compared to conventional therapies. Those patients with non-hypoxic tumours will also be identified and hence they will benefit from receiving treatment that is appropriate for their condition. 5-10 years.

Economic and societal impacts
-Pharmaceutical companies
Pharmaceutical companies could be significant beneficiaries of this work. If successful, we will protect the IP generated in this project and form a spin out company. The goal of this company will be to assist pharmaceutical companies stratify their clinical trials and potentially reposition cancer chemotherapies that have failed in clinical trials. Using the fluorogenic bioreductive compounds as companion diagnostics will ensure that the bioreductive drugs are only applied to that fraction of patients for which they are useful. Consequently, patients who are not identified as having hypoxic tumours can be treated in a manner that is suitable for their condition. 5-10 years.

-The UK tax payer
The UK tax payer and Government all potentially benefit from this research in two ways. 1- the fluorogenic hypoxia-activated group to ensure that patients receive appropriate treatment will save money for the NHS. 2- The formation of a spin out company benefits the local and national economy. The interaction of this company with global pharmaceutical companies will further benefit the national economy and hence the Government and public. 10-20 years.

-Public engagement
Both Profs Conway and Hammond are heavily involved in public engagement activities. Prof. Hammond is the academic engagement and outreach lead for the CRUK Oxford Centre. Continuous.