Mounjaro, dubbed the ‘King Kong’ of a new generation of slimming injections, has been approved by the NHS for some patients with diabetes.
However, many are very interested in its use as a weight loss drug in the UK after clinical trials showed that people taking it could lose 20 per cent of their body weight.
While Mounjaro, the brand name of the drug tirzepatide, has not yet been approved for those seeking to lose weight, private clinics can offer the drug for this purpose through the “off-label” prescription method.
MailOnline has set out everything you need to know about the latest weight loss drug approved in the UK.
Tirzepatide, sold under the brand name Mounjaro, has been approved for use in diabetics on the NHS.
What is Monjaro?
Mounjaro is the brand name for a drug called tirzepatide, manufactured by the American pharmaceutical giant Eli Lilly.
The medication is taken once a week by injection and helps increase the production of insulin, the hormone that regulates blood sugar, to control type 2 diabetes.
Mounjaro patients typically start with a 2.5 mg injection once a week for four weeks.
This dose is gradually increased by an additional 2.5 mg every four weeks.
The highest dose of Mounjaro that has been studied is 15 mg, so this will likely be the maximum dose a doctor will prescribe.
Mounjaro is the latest in a family of next-generation drugs that could help people lose weight, similar to its rival Wegovy.
Experts hope these drugs will provide a radical new way of treating obesity, a problem that costs the NHS around £6.5 billion each year.
The graph above shows how the weight loss drug tirzepatide works. It works to suppress hunger by mimicking hormones that signal the body is full. It also shows the passage of food through the stomach by reducing stomach acid production and muscle contractions.
How does it work to lose weight?
Tirzepatide belongs to a class of medications called GLP-1 agonists, which mimic a natural hormone that tells the body when it is full, suppressing appetite.
This helps reduce food and calorie intake, causing people to lose more weight than they normally would in combination with diet and exercise.
But unlike its competitors, it also mimics a second hormone that influences appetite called glucose-dependent insulinotropic polypeptide (GIP), which compounds the weight loss effect.
Some patients already taking the drug have shared their results on social media, and one overweight man claimed it helped him lose 100 pounds (45.4 kg).
How effective is it compared to Ozempic and Wegovy?
Clinical trials found that after just one year, one-third of type 2 diabetics taking Mounjaro lost more than 20 percent of their body weight.
This is more than the weight loss seen by the rival punches of Ozempic and Wegovy.
These drugs, made by Danish firm Novo Nordisk, use a different ingredient called semaglutide, also a GLP-1 agonist.
Ozempic is a specific formulation to help manage diabetes, while Wegovy is more potent and designed to treat obesity.
Patients taking Ozempic could lose up to 10 percent of their body weight, while those taking Wegovy could lose about 15 percent.
The difference in results led American diabetes expert Dr. Julio Rosenstock to declare Mounjaro “King Kong” compared to rival Wegovy’s “gorilla.”
It is important to note that these figures are the upper ranges of weight loss patients experienced and individual results may vary.
Does it have side effects?
Clinical trials have reported a number of side effects when taking Mounjaro.
One with 900 participants found that a fifth suffered from nausea and diarrhea, and about one in 10 reported vomiting or constipation.
Eli Lilly said Mounjaro side effects were reported most frequently during the dose escalation period.
Only about 4 percent and 7.5 percent of participants, in the 10 mg and 15 mg dose cohorts respectively, dropped out of the study due to side effects.
Other people who took the drug outside of clinical trials reported experiencing hair loss while taking Mounjaro.
A link to an increased risk of cancer from the injection has also been suggested.
The EU’s medicines watchdog, the European Medicines Agency (EMA), said earlier this year that research in rodents has suggested that the artificial hormones packaged in tirzepatide could increase the risk of medullary thyroid cancer.
The EMA has ruled that a follow-up study of patients taking the drug is necessary to explore the potential for an increased risk of cancer in humans.
According to the latest data, digestive problems were the most common side effects of tirzepatide, the active ingredient in Mounjaro. These included about one in five participants who suffered from nausea and diarrhea, and about one in 10 reported vomiting or diarrhea.
Who can get it currently?
As things stand, no one. Although that is expected to change soon.
Yesterday, the National Institute for Health and Care Excellence (Nice) recommended Mounjano as a medicine for diabetes, which should be prescribed together with diet and exercise.
However, supplies are not expected to arrive in the UK until October.
When they arrive, around 180,000 NHS patients with type 2 diabetes will eventually be eligible to receive tirzepatide.
While it’s not yet approved specifically for weight loss, some Americans are already using it “off-label.” One of them is Matthew Barlow, a 48-year-old health technology executive living in California, who said he has lost more than 100 pounds since November using Mounjaro and changing his diet.
Can it be used to lose weight?
Nice is expected to make a decision on whether tirzepatide can be used for weight loss in the coming months.
If approved, it is likely to have similar rules to Wegovy regarding its use in the NHS.
NHS patients can only be prescribed Wegovy if they have a body mass index (BMI) of 30 or more, or a BMI of more than 27 and at least one weight-related illness, and are committed to following plans diet and exercise are eligible.
However, this will not stop private clinics from distributing tirzepatide for weight loss once UK diabetic supplies become available.
Private clinics can do this through “off-label” prescriptions.
This is a system in which doctors can distribute a medicine approved in the UK, but for a purpose other than that for which it was approved.
In this example, a doctor might prescribe tirzepatide, a diabetes medication, to a patient who wants to lose weight.
Similar private prescriptions for Ozempic were observed before Wegovy supplies were available in the UK.
This has contributed to shortages and, as a result, some diabetes patients have been left without their diabetes medication prescriptions.
Some doctors have also expressed concern that private clinics seizing the supply of these drugs could prevent patients with the greatest medical need for the drugs from going without them.
How much could it cost?
NHS patients would only have to pay £9.65 for their dose in England.
In practice, however, many will get it for free under an exemption rule that exempts people with certain health conditions from paying for prescription drugs.
Most private clinics in the UK have not yet revealed what prices they would charge patients to access Mounjaro, but some have already listed it at £119 for an initial dose.
This is a far cry from what people pay in the US, where the price can exceed $1,000 per dose (around £820) depending on the patient’s insurance.
Elon Musk (left) attributes his dramatic 2020 weight loss to Wegovy. The tech mogul looked remarkably thin when he first arrived at Twitter headquarters after purchasing the company in October (right).
Could we see a shortage similar to Ozempic?
Possibly. Demand for semaglutide skyrocketed following the results of Wegovy’s clinical trials, leading patients to opt for Ozempic as an alternative.
This was also sparked by celebrities like Elon Musk and Jeremy Clarkson using the ‘miracle’ drug for weight loss, which only increased the clamor to get it.
This is not just a UK problem. Global interest in these drugs, including their public health potential to help combat obesity, has led to a global shortage.
But these supply problems are expected to reduce as more such drugs, like Mounjaro, come online.