Repurposing Drugs to Combat Brain Tumours
Following trials to assess their safety and efficacy, drugs are usually approved for use in the clinic by the regulatory authorities for the treatment of a specific disease. This is referred to as the drug “license” – the condition for which it can be prescribed by a doctor. However, an increasing number of studies have shown that drugs which have been approved for one condition may be effective in the treatment of others. This is referred to as drug repurposing. The advantage of this approach is that the drugs are likely already to have passed the initial safety stage of drug development so that they can immediately go into clinical trials to assess how effective they may be.
In this blog post, our Director of Research, Dr Kieran Breen, looks at this subject in more depth as he prepares for Brain Tumour Research to play a key role in the future of influencing drug repurposing in the UK.
How can we identify these drugs?
A drug acts by influencing certain chemical reactions, or pathways, within a cell. This usually influences how the cell works. In the brain, for example, it may cause nerve cells to produce chemicals that are associated with the transmission of electrical activities between cells. However, in certain circumstances, modification of these pathways may damage or even kill cells. This is what we want to harness in order to destroy the cells within brain tumours.
In addition to drugs that are in use to treat specific conditions, there may be others which had been tested in early stage clinical trials but failed to show any significant benefit for that specific illness. But it is worthwhile re-testing some of these drugs based on our knowledge of how they work. Brain tumour cells grown in a dish in the laboratory can be used to carry out initial tests to determine whether the drug will kill the cells. We can also grow normal nerve cells in the lab. This is important because we want the drug to target tumour cells without harming the surrounding brain cells.
However, many of the drugs which could be considered to be suitable for repurposing may also have been on the market for a long time and are readily available in a generic form. Therefore, there are few incentives for a drug company to fund expensive clinical trials to prove that the drugs are effective for the treatment of brain tumours. So we need to develop a mechanism by which the initial clinical trials can be funded to bring the drugs closer to being used in the clinic.
Are there other factors that we should consider?
One of the challenges associated with treating brain tumours is the ability of the drug to get into the brain. The blood-brain barrier – a protective membrane surrounding the brain – prevents many drugs from entering the brain. But Prof Geoff Pilkington at our Centre of Excellence in the University of Portsmouth has developed an all-human model of the barrier. So as well as being able to test whether the drugs may be effective to treat tumours, we can also assess their potential ability to enter into the brain.
Is there any evidence of repurposed drugs for the treatment of brain tumours?
Our research team at Portsmouth have demonstrated that an anti-depressant drug, clomipramine may also be able to kill tumours. However, further work is needed to examine dosage, side effects and mechanisms by which it may kill tumour cells.
Studies have also been carried out in America on the anti-epileptic drug sodium valproate with mixed results. While there is no indication that people who take the drug over a long period of time have a lower incidence of brain tumours, there is some evidence that it may act to increase the efficacy of temozolomide, which is a primary drug use to treat brain tumours.
So, what is the next stage?
The UK Department of Health is leading a new initiative to develop guidelines for the repurposing of drugs. This is a key component of our manifesto and we will be working very closely with this group to develop guidelines to get potential repurposed drugs into clinical trials as quickly as possible. We will also be highlighting this as a priority area for our future research at our Centres of Excellence.
If you have any questions, you can comment here, or email Kieran@braintumourresearch.org. If you have any general questions about Brain Tumour Research, please get in touch with our office by email email@example.com or by calling 01908 867200.