The U.S. Food and Drug Administration (FDA) has approved Zepbound (tirzepatide), a new drug manufactured by Eli Lilly, for chronic weight management. This approval marks a significant step forward in addressing obesity, affecting over 100 million adults and 15 million children in the U.S. Zepbound is approved for adults with obesity (BMI of 30 or higher) or those who are overweight (BMI of 27 or higher) with at least one weight-related condition, such as high blood pressure, high cholesterol, or type 2 diabetes. The drug is intended to be used in conjunction with a reduced-calorie diet and increased physical activity.
Clinical Trial Results
The FDA's approval was based on data from two large clinical trials. In one trial, participants without diabetes who received the highest dose of Zepbound experienced an average weight loss of approximately 18% of their body weight, or about 41 pounds (19 kilograms), compared to those on placebo over 16 months. A separate study showed that individuals with diabetes, who often find weight loss more challenging, achieved an average weight reduction of 12%, or nearly 27 pounds (12 kilograms).
Another recent study indicated that Zepbound, when combined with intensive diet and exercise, helped people lose up to a quarter of their weight, or 60 pounds (27 kilograms).
Mechanism of Action
Tirzepatide, the active ingredient in both Zepbound and Mounjaro, works by mimicking the effects of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), two incretin hormones that play a crucial role in regulating appetite and blood sugar levels. By activating these receptors, tirzepatide enhances insulin secretion, suppresses glucagon secretion, slows gastric emptying, and promotes satiety, ultimately leading to reduced food intake and weight loss.
Comparison to Other Weight Loss Drugs
Zepbound appears to demonstrate greater efficacy in weight loss compared to semaglutide (Wegovy, Ozempic). Studies have shown Wegovy resulting in approximately 15% weight loss, or 34 pounds (15 kilograms). Dr. Fatima Cody Stanford, an obesity medicine expert at Massachusetts General Hospital in Boston, stated that Zepbound could be "the most highly efficacious drug ever approved for the treatment of obesity."
Cost and Accessibility
Eli Lilly has announced that the list price for Zepbound will be approximately $1,000 per month, similar to Mounjaro. The drug is expected to be available in the U.S. by the end of the year. However, experts have expressed concerns about accessibility, as many insurance plans may not cover obesity care. Dr. Katherine Saunders, an obesity expert at New York's Weill Cornell Medicine, noted that most patients would be unable to afford Zepbound without insurance coverage.
Side Effects
The most common side effects associated with Zepbound include nausea, vomiting, diarrhea, constipation, and other gastrointestinal issues. In clinical trials, approximately 10% of participants taking tirzepatide discontinued the study due to these side effects, compared to about 2% of those taking placebo.
