Ozempic, Viagra and the life-changing drugs that were created for something else

The process of repurposing has long been used in pharmacology, including some familiar household medications. Photo / 123RF

For the second time this week, a drug that was invented to treat one condition has been given the green light for something else. The diabetes medication tirzepatide has been authorised to help patients with weight-related health problems – such as prediabetes, high blood pressure, high cholesterol or heart conditions.

This follows on from the groundbreaking decision this week to “repurpose” a breast cancer drug: anastrozole. The daily pill, which halves the risk of contracting breast cancer for certain women – was originally licensed for treatment of the disease, rather than the prevention for which it can now be used.

Anastrozole became the first drug to be authorised via the UK’s NHS “repurposing” programme, to ensure that drugs which are licensed for one use can be given the green light for another. It will be available immediately, and could potentially help 300,000 women who otherwise may not have had preventative treatment.

The NHS programme may be new, but the process of “repurposing” (which is similar to using a drug “off label”) has actually long been used in pharmacology, including some familiar household medications. The infamous Ozempic, for example – beloved of celebrities – is commonly used “off-label” for weight loss and prescribed by private clinics, even though it has not been licensed for this use in the UK by the NHS.

“In a nutshell, repurposing means to teach an old drug new tricks,” says Chris Smith, a consultant virologist and lecturer at Queens’ College, Cambridge. Scientists are currently looking at a wide range of drugs to repurpose. For example, the British Heart Foundation is part-funding research alongside the University of Manchester which has found that amlodipine, a drug used to treat high blood pressure, could help treat vascular dementia or stop it in the early stages.

There are also hopes that a cancer drug called aldesleukin could offer a solution to the damage that happens to the heart after a cardiac event, boosting anti-inflammatory cells in the patient’s immune system.

These drugs offer hope for the future. But as Smith suggests, many of us are already using repurposed drugs daily, without being aware of their provenance. “The classic example is Viagra,” he says. " It was invented as a blood pressure medication, but in the phase one trials, all the healthy young men reported certain side-effects, which we all now know about. So Pfizer pivoted and found a new use for their drug.”

Smith says that repurposing is much sought after in the pharmaceutical industry. “It short-circuits the need for further checks and balances, as these tests have already been done to establish a drug’s safety profile in another indication, and the regulator has said ‘OK’,”  he says. “New trials take too long, and can become very expensive. The industry tends to run on the ‘rule of 10s’. Only 10 per cent of new drugs make it through trials, they often take 10 years, and cost 10 billion pounds.”

Some repurposed drugs are now used for totally different illnesses and cures. Photo / 123RF

Sometimes, the repurposing is to use the drug for a different use to target the same illness, as with the anastrozole case. “We knew this drug worked as a treatment in women who had oestrogen-sensitive breast cancers,” says Smith. “We gave it to post-menopausal women and it reduced their cancers coming back: in effect, taking away the hormone which was the cancer’s food supply. Now we know it stops breast cancer coming back, why not give it to people who are at risk of getting breast cancer in the first place?”

There’s been particular fanfare around the anastrozole announcement because of the massive clinical effect, says Smith. “One in 11 women will get breast cancer. The survival rate is now 80 per cent, but it could be higher.” As well as saving lots of lives, anastrozole represents a massive cost saving for the NHS, a pill is far cheaper than treating women for cancer – and its possible recurrence.

Other repurposed drugs are used for totally different illnesses and cures. “The first-generation antidepressants were originally for TB,” says Smith. “Scientists discovered that people’s moods improved while taking them, so they decided to market them for a new use. Many people know AZT as one of the first Aids drugs, but before that it was a crappy cancer drug that really didn’t work very well. But during trials, doctors noticed it worked on HIV.”

Then there’s the notorious case of thalidomide, the morning sickness drug that led to birth deformities in the 1950s and 1960s. “Few people know that in the 2000s, thalidomide got a new lease of life as a treatment for multiple myeloma, a cancer of the white blood cells,” says Smith.

Smith describes the days of AZT as “brute force – we threw everything at an illness, until it seemed to work”. But now, the repurposing of drugs is becoming far more sophisticated. “We now have an enormous amount of data,” he says. “A computer can track that if a patient has taken X, they will get the side-effect Y. When you look at the data, you can see the outcomes – while taking a certain drug, the death rates from a totally different illness will go down, for example. With computers, and the gene mapping we have done, we can expand this on a massive scale. So if a drug turns off a certain gene, it could well be a cure for something entirely different.”

Adds Smith: “With AI, the potential to repurpose drugs is huge.”

Common hero drugs, which started life as something else

Aspirin

The oldest repurposed drug. Aspirin was originally marketed by drug company Bayer in 1899 as a painkiller, but was first repositioned in the 1980s, at low doses only, as an antiplatelet aggregation drug, and is still widely used today to prevent cardiovascular events.

Sildenafil (or Viagra)

Viagra started life as a drug to treat hypertension, or high blood pressure. But it was also shown to produce vasodilation (or the widening of blood vessels), and an unexpected side-effect was the stimulation of penile erections, when in the presence of sexual stimulation. This physiological effect led Pfizer to market sildenafil in 1998 for erectile dysfunction, under the brand name Viagra, generating peak annual sales in excess of US$2 billion.

Tamoxifen

This drug was originally licensed for the treatment of breast cancer. But in 2002, The Center for Reproductive Medicine and Infertility at NewYork Weill Cornell Medical Center discovered that tamoxifen could help breast cancer patients have babies – even after they experienced fertility loss associated with chemotherapy. This was later broadened out to help women who hadn’t had breast cancer conceive via IVF.

Plus:

Beta-blockers – blood pressure drugs that are prescribed for anxiety.

Tocilizumab – an arthritis drug used to treat Covid during the pandemic, which cut the risk of Covid death by 14 per cent.

Spironolactone – a blood pressure drug that can treat acne.

Nortriptyline – an antidepressant prescribed for chronic pain.