The drugs work, and for more than one purpose

Tried and trusted drugs can be effective in tackling medical issues for which they were not originally designed

Viagra: originally studied for the heart condition angina. Photograph: SSPL/Getty Images

Viagra: originally studied for the heart condition angina. Photograph: SSPL/Getty Images


Upcycling has gradually been taking over the fashion world. Now the pharmaceutical industry seems to be doing the same: taking an old item and putting it to a new purpose.

The drug companies are taking a systematic approach to getting maximum use out of old drugs, a development that is “welcome and necessary in many clinical areas”, according to the Health Products Regulatory Authority.

Most drugs have a number of effects. Usually there is one purpose for which a drug licence is obtained, for example, aspirin as a painkiller. But often a drug can have another practical use: low-dose aspirin can be used for stroke prevention, for example.

If it makes sense that a drug for one condition also has another effect on the body, doctors may prescribe “off-label” for purposes other than those covered by the drug licence. Sometimes enough evidence is gathered over time that a drug is safe and effective in this second disorder and it is repurposed., gaining a licence for this second use, says Prof Patrick Murray, dean of University College Dublin’s medical school and professor of clinical pharmacology.

Most repurposing of drugs to date has happened by chance, he says. “This is something doctors have been doing for a long time on a case-by-case basis. In every medical speciality there are examples of high-profile drugs that have been repurposed.”

In Ireland, medications such as Viagra, Lyrica and Rogaine have all been repurposed. “The difference now is that there’s a rethink of how we find new drugs: a more purposeful and systematic approach,” says Murray.

In Ireland, the Health Products Regulatory Authority acts as regulator for medicines and clinical trials of medicines. The authority says it is “very supportive of efforts to repurpose medicines in areas of unmet patient need. The standard approach is that an authorised medicine with a known and good safety profile undergoes clinical trials in a new indication for which there is a sound rationale for efficacy.”

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The practice represents a way of getting maximum value from drugs which have already been heavily researched and are known to be safe. In the US, the National Institutes of Health runs a programme dedicated to supporting researchers to find ways to repurpose existing drugs, including public databases. “Therapeutic development is a costly, complex and time-consuming process. The average length of time from drug target discovery to approval of a new drug is about 14 years,” according to the new therapeutic uses programme.

The failure rate during this process exceeds 95 per cent, and the cost per successful drug can be $2 billion or more, the National Institutes of Health says. The high drug failure rate means there are many existing, partially developed compounds that could be repurposed: “Exploiting this could produce new treatments much more quickly than starting from scratch.”

Repurposing has potential benefits beyond reducing cost, Murray says. “Aside from the economics of it, this is important for rare conditions where drug companies don’t invest because they’re not large enough markets, but it is also likely to benefit some conditions where there aren’t currently great hopes from the drug discovery pipelines, such as schizophrenia,” he says.

“European law provides incentives for the development of medicines in rare medical conditions. While the number of applications is low in overall terms, the legislation has resulted in drug authorisations in clinical areas of unmet need,” according to the Health Products Regulatory Authority.

Some medications originally legitimately withdrawn from the market because of side effects are being investigated for use in other, more specific circumstances. Thalidomide is one example. “If there is a property in a drug that we want to positively exploit, maybe in more specific circumstances it will be safe for a particular group of people,” says Murray.

But there’s a catch. If a drug is repurposed by the company that owns the licence, extending the patent can make a drug more expensive for longer, increasing overall cost to the consumer.

In Ireland, the National Centre for Pharmacoeconomics refers to this practice as “evergreening”, extending patents for use in new doses or formulations.

“Everybody is aware of examples where repurposing is done by a company to extend the life of their patent. You could say that if it’s done for that reason it has limited potential, but then people can be treated for more conditions so there is benefit in that. The financial incentive for patent extension is clear, but the flipside is that more people can be treated for other conditions,” says Murray.

“Although, in some cases, drug companies do stand to make a lot of money from repurposing, it’s not necessarily always a lucrative process for companies as many of these medications are older and off-patent” he says. “Ultimately anything that incentivises people to pursue more ideas so more conditions can be effectively treated has to be encouraged, whether the motive is commercial or academic,” says Murray. “The economics of it are controversial but in the end you have to look at the net outcome – more people being effectively treated for their condition.”

Versatile pharmaceuticals: The uses of Viagra, minoxidil and thalidomide Viagra is a common example of drug repurposing, says to the US National Institutes of Health. The drug was originally studied for the heart condition angina but studies were abandoned when men complained of erections as a side effect. It was licensed as a treatment for erectile dysfunction and research continued into its effects on the heart, leading to the discovery it can effectively treat a type of high blood pressure called pulmonary hypertension.

Similarly, the blood-pressure treatment minoxidil was found to cause hair growth as a side-effect and is now an active component of hair-loss treatments.

Thalidomide was sold over the counter in many countries in the 1950s as a sedative. It was withdrawn after it was discovered to be responsible for severe birth defects. Years later, it was proposed that the drug could have benefits in specific circumstances, and now it is used under strict regulations to treat skin disorders and some cancers.