Semaglutide from the Novo Nordisk company is the first drug approved for the treatment of obesity that has achieved weight loss similar to that of bariatric surgery. Eli Lilly's tirzepatide, which acts in a similar way, is expected to be approved in the coming months after having demonstrated its effectiveness and safety in clinical trials. Other multinational pharmaceutical companies are developing similar drugs to treat a disorder that in Spain affects 22% of the adult population.
The new drugs imitate the action of the hormone GLP-1, which the human body produces naturally and has multiple effects on the body. In the pancreas, GLP-1 enhances insulin activity, which is why semaglutide was initially developed as a diabetes treatment. In the digestive system, it slows down the emptying of the stomach, which makes it easier for the person to take longer to feel hungry again after eating. Even more important is the effect of GLP-1 on the brain, where it reduces appetite and increases the feeling of satiety in regions that regulate food intake behavior.
Semaglutide has achieved an average weight loss of 17% in people with obesity in clinical trials. An average weight loss of 21% has been recorded with tirzepatide - although the design of the clinical trials was different, so the effectiveness of the two drugs cannot be directly compared. With a third drug in a less advanced phase of development, Eli Lilly's retatrutide, the average weight loss has reached 24%.
The new anti-obesity medications have proven to be effective in clinical trials where participants carried out diet and physical activity, in addition to receiving pharmacological treatment. Therefore, GLP-1 analogues are presented as complements to diet and physical activity, not as substitutes.
Side effects that require treatment to be discontinued are exceptional, but mild adverse effects that are bothersome are common. The most common are nausea (which affected 38% of participants in clinical trials of semaglutide), vomiting (22%), diarrhea (27%), constipation (22%) and vomiting (22%). These side effects usually occur in the first weeks of treatment and usually reduce over time. To minimize them, it is common to start treatment with low doses and increase them little by little over several weeks.
As these are drugs that have been used for a short time, they could have long-term effects that are still unknown, and that could be both positive and negative.
Semaglutide is available in Spain under the trade name Ozempic for the treatment of diabetes in people with obesity. For the treatment of obesity in people without diabetes, it is approved but has not yet begun to be distributed and will have the commercial name Wegovy. The difference between Ozempic and Wegovy is in the dosage, which is a maximum of 1 milligram weekly for diabetes and can reach 2.4 milligrams for obesity.
Tirzepatide, for its part, has been approved in Europe since last year for the treatment of diabetes under the name Mounjaro, but it is not yet available in Spain. The European Medicines Agency (EMA) is currently evaluating its approval for the treatment of obesity. The Eli Lilly company expects the EMA to announce its decision in late 2023 or early 2024.
There will be two options: weekly injection or daily pill. For now, Wegovy is only administered as a subcutaneous injection once a week. Users inject the drug themselves, usually into the abdomen or thigh, with an easy-to-use, extremely fine needle that causes no pain. For Ozempic against diabetes, in addition to the injectable presentation, there is an alternative in pills that must be taken daily in the morning on an empty stomach. “There are people who prefer pills and others who prefer the injection, because then they don't have to worry about taking the drug every day,” declares Andreea Ciudín, coordinator of the obesity unit at the Vall d'Hebron hospital in Barcelona. The different companies that are developing GLP-1 analogues for obesity are investigating both injectable and pill presentations.
The European Medicines Agency has approved Wegovy for three groups: adults with a body mass index (BMI) greater than 30 (the limit at which a person is considered obese); adults with a BMI between 27 and 30 (considered overweight but not obese) if they have at least one serious health problem associated with excess weight; and adolescents over 12 years of age with obesity and weighing more than 60 kilos.
BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters. For example, for a person who is 1.80 meters tall and weighs 80 kilos, the BMI is 24.7 (which is the result of dividing 80 by 1.80, and dividing the result again by 1.80).
Wegovy is not approved for rapid weight loss nor has it been proven effective for this purpose. Its effectiveness has been evaluated in clinical trials in which participants have taken the drug for a minimum of eleven months, in which they have progressively lost weight.
When treatment has been stopped at the end of clinical trials, most participants have regained weight. This observation suggests that, for many users, anti-obesity treatment with drugs based on the GLP-1 hormone will be longer term, and possibly chronic.
In Spain, both semaglutide and tirzepatide are available with a medical prescription.
“The price [of Wegovy] will be known when we are going to market the medicine in Spain,” a company spokeswoman reported on Friday. “We are currently not in a position to offer a figure.” In Germany, where the drug is already on sale, the price is around 310 euros per month.
