A new weight-loss drug was approved by the Food and Drug Administration (FDA) on Wednesday, opening up more options for U.S. patients seeking treatment for obesity.
In the past year, there has been a huge boon in the popularity of weight-loss drugs thanks to Ozempic, a type-two diabetes drug that generated headlines for its off-label use as an obesity drug. Demand for Ozempic and its sister drug Wegovy, which is approved specifically for obesity, has led to shortages.
Wegovy has never been available in Canada — despite being approved two years ago — due to persistent supply issues.
But with the FDA approval of Zepbound by drugmaker Eli Lilly, it looks like Wegovy is no longer the only obesity drug on the market.
What is Zepbound?
Zepbound is a new product, but it’s not a new drug.
The medical ingredient in Zepbound is called tirzepatide, which is the same ingredient in another Eli Lilly drug called Mounjaro, a type-two diabetes medicine. Mounjaro was approved in Canada last year and has been prescribed off-label for obesity.
This is similar to the case of Ozempic and Wegovy. Both drugs are made by Novo Nordisk and share the same medical ingredient, called semaglutide. Despite being the same drug, the former is approved specifically for diabetes while the latter is approved for obesity.
According to clinical trials, however, Zepbound (or tirzepatide) may perform better than semaglutide when it comes to weight loss.
A Phase 3 study (a study that demonstrates whether or not a product offers a treatment benefit to a specific population) found that adults with obesity taking the highest dose of Zepbound lost an average of 22.5 per cent of their body weight, amounting to about 52 pounds. At lower doses, study participants lost an average 21.4 per cent to 16 per cent of their body weight.
In a similar trial, semaglutide was shown to reduce body weight on average by around 15 per cent.
Semaglutide has been a huge money-maker for Novo Nordisk, bringing in nearly US$10 billion in 2022. With tirzepatide’s high efficacy, industry analysts predict it could become one of the top-selling drugs ever.
How does it work?
Semaglutide mimics a hormone that humans naturally produce called glucagon-like peptide 1, GLP-1 for short.
GLP-1 is created in the pancreas and signals the body to increase insulin production. It also blocks the release of another hormone called glucagon (the G in GLP-1), which tells the liver to release more glucose (sugar) into the bloodstream. In short, semaglutide mimics this GLP-1 hormone and can trick the body’s intricate system of chemical receptors to boost insulin and lower blood sugar.
It’s clear to see why semaglutide works as a diabetes treatment, but researchers are less sure how it works for weight loss. It appears that GLP-1 slows the movement of food through the stomach, a process called gastric emptying.
Tirzepatide builds on the same mechanism semaglutide uses to spark weight loss. While semaglutide mimics one hunger-regulating hormone, GLP-1, tirzepatide mimics two hormones, GLP-1 and GIP (glucose-dependent insulinotropic polypeptide).
According to Dr. Sean Wharton, an internal medicine physician and weight management specialist, the GLP-1 hormone probably confers the most weight-loss benefit. But having another hunger-regulating hormone in the mix is like “having a running back, trying to get into the end zone” with an extra blocker.
“The running back by himself probably does pretty well — and we’re seeing that the semaglutide molecule is amazing — but with (more) blockers he’s probably going to do really well,” Dr. Wharton says.
Dr. Wharton says the arrival of new weight-loss drugs is great for doctors and patients alike, because it means that there are more options for care and more competition in the market could drive these drug prices down across the board.
Ozempic, for instance, comes with a hefty price tag — about $200 to $300 a month in Canada — because it isn’t typically covered for weight loss under insurance plans, doctors told Global News.
Zepbound in the U.S. will have a list price of about US$1,000 a month, the same as Mounjaro, but U.S. medicare is prohibited from covering drugs specifically for weight loss.
“Most patients won’t be able to afford Zepbound without insurance coverage and many health plans exclude obesity care,” said Dr. Katherine Saunders, an obesity expert at New York’s Weill Cornell Medicine.
Who can be prescribed Zepbound?
So far, Zepbound has only been approved in the U.S.
Health Canada told Global News in an email that Eli Lilly has not submitted Zepbound for review in Canada.
Global News has reached out to Eli Lilly for comment on whether they plan to submit Zepbound for Health Canada approval.
In the U.S., Zepbound is approved for adults who are considered obese using a measure known as body mass index (BMI), a ratio of weight to height. People are eligible for the drug if they have a BMI of at least 30 or higher, so are patients with a BMI of 27 if they have at least one weight-related health condition like diabetes or high blood pressure.
The drug should be used along with a reduced calorie diet and increased physical activity. Zepbound should not be used with other drugs that belong to the same class of medicines, like Ozempic, and is only approved for adults 18 and older.
What are the risks of taking weight loss drugs?
While doctors and drugmakers have hailed advancements in weight-loss drugs as a treatment for obesity, these medications do come with serious downsides.
For some, taking these medications is worth it to shed pounds and the stigma of living in a larger body.
“Unfortunately, despite scientific evidence to the contrary, obesity is often seen as a lifestyle choice – something that people should manage themselves,” said Dr. Leonard Glass, a senior vice president of global medical affairs for Lilly Diabetes and Obesity.
“For decades, diet and exercise have been a go-to, but it’s not uncommon for a person to have tried 20-30 times to lose weight with this approach. Research now shows that the body may respond to a calorie-deficit diet by increasing hunger and reducing feelings of fullness, making weight loss more difficult. Lilly is aiming to eliminate misperceptions about this disease and transform how it can be managed.”
Side effects of Zepbound can include nausea, diarrhea, vomiting, constipation, abdominal discomfort and pain. Other adverse effects listed in the drug’s label include injection site reactions, fatigue, burping, hair loss and gastroesophageal reflux disease.
In the most recent published trial, about 10 per cent of people taking tirzepatide dropped out of the study because of such problems, compared to about 2 per cent of people taking a placebo.
People who are pregnant should not take Zepbound.
While not listed as a side-effect of Zepbound, patients taking weight-loss drugs have said they experienced stomach paralysis, which occurs when ones stomach takes too long to empty food. This can cause the food to harden into solid masses called bezoars which can cause blockages.
According to a study by the University of British Columbia, Wegovy and Ozempic are associated with an increased risk of stomach paralysis, pancreatitis and bowel obstruction.
Susanne Brown, a woman who has been on Ozempic for four years, told Global News that Ozempic has been life-changing for her, and has allowed her to hit her fitness goals.
But she also likened being on Ozempic to “doctor-approved anorexia,” and said she felt addicted to losing weight on the drug.
Because her appetite was so suppressed on Ozempic, she fell into dangerous eating habits.
Brown recalls that she had to take caffeine supplements to stay awake during the day and to have enough energy to work out because she wasn’t getting enough nutrition on Ozempic. Eventually, she became anemic and her hair started to fall out.
Even with these distressing downsides, Brown said she would never discourage someone with obesity from taking Ozempic, in part because of how much better society treats her now that she’s physically smaller.
Disability rights scholar and assistant professor Fady Shanouda of Carleton University says that weight-loss drugs like Ozempic can have a “coercive” effect on people in larger bodies because of societal expectations to be thin.
Instead of accepting their bodies, people may feel pressured to lose weight in a way that actually makes them less healthy.
“I’m not invested in people feeling bad about their bodies,” he said. “Unhealthy bodies should still be allowed to exist in our world.”
— With files from The Associated Press and Reuters