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Is there a cure for cancer sitting at the back of the medicine cabinet already?

Could be – but there's no money in that, it seems

The hidden benefit of heartburn medicine

Changing the microenvironment can have radical effects on the viability of the tumour. If cancer is an insurgency, think of this as cutting off the supply lines and the support from the local population. Without those the insurgency doesn’t get to spread any further, even if you don’t directly kill the enemy fighters.

One of the best examples of this comes from the need for a tumour to have an adequate blood supply to gain nutrients and oxygen – the sprouting of this blood supply is called angiogenesis. Some of the first targeted agents were aimed at blocking angiogenesis through actions on specific parts of the pathway. But it turns out that some common drugs, such as the antacid cimetidine, the antifungal itraconazole and the anti-worming treatment mebendazole also target multiple parts of the pathway as part of their activity.

In fact if we take the example of cimetidine – better known as Tagamet in the US and used to controll heartburn – we find that it has multiple mechanisms of action that are useful against cancer. Cimetidine can have direct action on some cancers cells, it is anti-angiogenic, acts on cell adhesion and has multiple actions on the immune system, including helping to reverse the immune suppression that tumours use to protect themselves.

What’s more, we have data not just from theoretical analysis of these pathways or from test tube studies, but there’s also human evidence from case reports and clinical trials. In fact in the case of cimetidine, a Cochrane Review (a rigorous and independent meta-analysis of data from multiple studies) found that it conferred a survival advantage in colorectal cancer.

Cimetidine is not the only such case, there are other drugs for which we have evidence – epidemiological, pre-clinical, case reports and clinical studies. In some cases, for example with metformin and aspirin, the oncology world is actively investigating and running large clinical trials.

In other cases, for example with mebendazole, the mainstream oncology world remains sceptical and the ReDO project and other small research groups are bringing together the evidence to change this. But the number of potentially useful non-cancer drugs is rising as we do more work in this area.

An additional argument in favour of these repurposed drugs comes from the very fact that they’re well-known and well-used drugs. Unlike new drugs, we already know a lot about safety and side-effects and dosing. It means we can short-circuit a lot of early phase trials which are expressly designed to figure those out before we even start to test how good they are at fighting cancer.

So, how come a generic drug that costs pennies compared to a new targeted agent that costs thousands of pounds isn’t in clinical use? The data is there, the drugs are there and certainly the patients are there. At this point we begin to stray from medicine and into the arena of intellectual property and incentives.

There is a huge regulatory burden and massive costs involved in running the largest Phase III trials normally required to convince doctors to change medical practice. What’s more, drugs need to be licensed for new uses and this also incurs costs. Who pays for all this?

With no guarantee of a return on investment, we’re left with a class of drugs that has huge potential but we don’t have the incentives in place to see the science confirmed and the drugs moved into clinical use after that confirmation.

This leaves us looking for innovative solutions in the search for drugs, but also innovation in the field of economic incentives in drug development. But if we get this right – as I hope we do – then the pay-off for society at large is immense. ®

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