Wegovy cancer risk fears: Experts probe link between miracle fat jab ingredient and two diseases

A ‘game-changing’ weight loss jab is being investigated over fears it may raise the risk of cancer, MailOnline can reveal. 

US research on mice and rats has suggested semaglutide — the powerful ingredient behind Wegovy — could raise the risk of medullary thyroid cancer (MTC).

Novo Nordisk, the Danish pharmaceutical giant that makes the weekly injection, is probing whether it may have the same effect in humans. 

Another study run by the firm itself is looking at whether semaglutide may lead to pancreatic cancer. 

Both diseases are listed as being ‘important potential risks’ by European Medicines Agency (EMA) bosses. 

Under new recommendations by NHS watchdog NICE published this week, Wegovy will be available for people who have a BMI of 35 or more — a classification which means they are morbidly obese. Patients must also have at least one weight-related comorbidity, such as type 2 diabetes, to be eligible. Adults with a BMI between 30 and 35 could also be recommended the drug, if they have been referred for specialist help

But no evidence yet proves they are definitely side effects — even in extremely rare cases.

It means that Novo Nordisk does not have to list either disease as being a potential consequences in leaflets tucked inside the packaging of either Wegovy or its sister Ozempic, a slightly weaker version licenced for type 2 diabetes. 

The former will be rolled out on the NHS in coming weeks after being approved this week. 

That could change if either study firms up the link, MailOnline understands. 

A spokesperson for Novo Nordisk told MailOnline: ‘We continuously collect and analyse data on the use of our medicines post marketing authorisation, and follow international pharmacovigilance standards to report and analyse any adverse events experienced by people taking our medicines.’ 

They added: ‘We work closely with the Medicines and Healthcare products Regulatory Agency (MHRA) to ensure that healthcare professionals have a thorough and full understanding of the safety profile of our medicines.’ 

Meanwhile the MHRA, which polices the safety of drugs used in the UK, said: ‘As with all medicines, the safety of Wegovy is kept under continual review to ensure the benefits outweigh the risks.

‘The MHRA will carefully evaluate any emerging evidence from ongoing studies alongside other sources of information and promptly communicate any new advice to healthcare professionals and patients as needed.’

They added: ‘No medicine is completely risk-free, so the decision to start, continue or stop treatments for obesity and weight management should be made jointly by patients and their doctor, based on the best advice available and their own personal circumstances.

‘We ask everyone to report any suspected side effects using our Yellow Card scheme website. Patient safety is our top priority.’

Alex Guevara, 47, (pictured) is a paramedic practitioner from Milton Keynes. He has three children, and lives with his wife Christina, 29. He said: ‘When a friend told me about semaglutide I felt I had nothing to lose. I went to a private clinic, and paid £250 a month for six months’

Wegovy works by triggering the body to produce a hormone called glucagon-like peptide-1 that is released naturally from the intestines after meals

Ozempic, available on the NHS since 2019, is solely targeted at patients with type 2 diabetes. Although, it has been given out off label privately for people trying to lose weight 

Thyroid cancer is already listed in the ‘most important information’ patients should know about Wegovy on the product’s own website. 

Other rare side effects include diabetic retinopathy complications — damage to the blood vessels at the back of the eye.

Semaglutide is self-administered once a week with pre-filled pens straight into the stomach, thigh or upper arm.

Wegovy works by hijacking the brain to suppress appetite and reduce calorie intake, resulting in substantial weight loss. 

It is packed with a more potent dose than Ozempic and is instead targeted at people who weigh too much.

Ozempic, available on the NHS since 2019, is solely targeted at patients with type 2 diabetes. Although, it has been given out off label privately for people trying to lose weight. 

It lowers their blood sugar and reduces the risk of heart attacks and strokes among those who also have heart disease.

Under new recommendations by NHS watchdog the National Institute for Health and Care Excellence (NICE) published this week, Wegovy will be available for people who have a BMI of 35 or more — a classification which means they are morbidly obese.

Patients must also have at least one weight-related comorbidity, such as type 2 diabetes, to be eligible.

Adults with a BMI between 30 and 35 could also be recommended the drug, if they have been referred for specialist help.

But patients eligible for the injections must only use them for up to two years.

And, despite being hailed as one of the most powerful pharmaceutical tools to date, experts have warned it is not a ‘magic pill’ or miracle fix all.  

Trials have shown that users can rapidly pile pounds back on once they stop taking the fat-fighting drug, dubbed ‘Hollywood’s worst-kept secret’ and used by the likes of Elon Musk.

And it can trigger a variety of nasty side effects. Some patients have told of how they have had to stop taking the drug because of them.

Users commonly complain of nausea, constipation and diarrhoea after taking the medication. 

A UK study found that people who used Wegovy experienced rapid weight loss, dropping 18% of their weight over 68 weeks. They regained two-thirds of that weight, or 12% of their original body weight in the year after dropping the weekly injections. Experts says the drug needs to be used over a lifetime to keep off the pounds

A spokesperson for Novo Nordisk told MailOnline: ‘We continuously collect and analyse data on the use of our medicines post marketing authorisation, and follow international pharmacovigilance standards to report and analyse any adverse events experienced by people taking our medicines’

Some also suffer from acid reflux, fatigue and complain that food tastes different after taking the drug. 

It is this side effect that some people credit for further assisting their weight loss — by making their favourite junk foods taste bad.

Other rarer side effects include gallstones, inflammation of your pancreas — known medically as pancreatitis — and an increased risk of low blood sugar and kidney problems. 

But the American Society of Health-System Pharmacists also warns that semaglutide ‘may increase the risk you will develop tumors of the thyroid gland, including MTC’. 

MTC is a rare type of thyroid cancer, accounting for between five and 10 per cent of all thyroid cancers in the UK, according to Macmillan Cancer Support.

Around three quarters of sufferers will be alive five years after being diagnosed. 

Writing in the US National Library of Medicine, the society said: ‘Laboratory animals who were given semaglutide developed tumors. But it’s not known if this medication increases the risk of tumors in humans.’ 

Novo Nordisk launched a trial in 2012 to investigate this possible association in patients with type 2 diabetes. 

Results of the US-only study are not expected until December 2035, by which time the drug will have been used on the NHS for 12 years. 

‘An active surveillance program is the most efficient means of identifying a possible association’, the manufacturer wrote. 

‘Given the uncertainty of the association of MTC in humans treated with these drugs, a study duration of at least fifteen years… was thought to provide evidence of an association, if one exists.’ 

Further research would begin if a link was found, Novo Nordisk said. 

Meanwhile, a second multi-national study run by Novo Nordisk involving 600,000 participants was established in January 2021. 

It was created to assess the risk of pancreatic cancer in type 2 diabetes patients.

That study, estimated to end in 2024, will compare the risk associated with new users of semaglutide drugs Ozempic and Rybelsus against other antidiabetic drugs, including insulin. 

Danielle Breckenridge (pictured before the weight loss, left, and after, right) says she also lost more than 2st after taking semaglutide injections

Ciara Lawless, from Dublin, lost 2st (28lbs/12.7kg) in May 2020 after getting semaglutide injections when she weighed around 12 and a half stone. She said she maintained her weight after coming off the jab through healthy eating and a weekly treat but has since used the jab ‘for help’ when she ‘needs it’

A report by the European Medicines Agency says, however, there is ‘no evidence from clinical trials, that GLP-1-based therapies (the family of drugs semaglutide belongs to) increase the risk of pancreatic cancer’.

Another complication being probed is diabetic retinopathy, caused by high blood sugar levels damaging the back of the eye. It can cause blindness, if left untreated.

In its ‘summary of risk management plan for Ozempic’, the EMA revealed it had identified an ‘important’ risk of diabetic retinopathy complications, following a 2021 trial of the drug. 

Higher rates of the condition were reported among those with type 2 diabetes who used semaglutide 2.4 mg than those with the placebo.  

Results from the diabetic retinopathy trial are not expected until December 2026. 

But this is already listed as a potential rare side effect in the patient information leaflet. 

The drug works by mimicking the effects of glucagon-like peptide-1 (GLP-1), a hormone which targets areas of the brain that regulate appetite and food intake — making users feel less hungry.

It also slows down the movement of food in the gut, which helps users stay full for longer and signals to the body to release insulin, which helps move digested sugar from the blood into cells where it can be used for energy. 

MailOnline understands studies have been and are continuing to investigate the risks of medullary thyroid cancer and pancreatic cancer linked to all GLP-1 drugs including exenatide, liraglutide, lixisenatide, dulaglutide and semaglutide.