Here’s a question from a reader who wishes to remain anonymous:
A new weight-loss drug was recently approved. My understanding is that it works in two pathways, while another class of drugs only works in one. Is this true? And what does it mean for the drugs?
Dr. James Prescribes
What a timely question for Thanksgiving, when the Calorie Control Council estimates the average American consumes 3,000 to 4,500 calories at a single meal.
Now, a quick warning: This may get a bit confusing with all of the drug names.
Earlier this month, the Food and Drug Administration approved the injectable weight-loss drug tirzepatide as a treatment for obesity. This is the same compound in the drug Mounjaro, which was approved as a diabetes treatment in 2022. However, for weight loss, it will be sold under the name Zepbound.
It will compete with semaglutide, the compound found in Wegovy, another injectable drug already approved for weight loss in obesity. It’s also the active ingredient in the diabetes drug Ozempic.
Wegovy, the previously available drug, simulates one hormone in the body. That hormone, known as GLP-1, prompts the body to secrete insulin when blood sugar rises.
But more than one hormone is involved in regulating blood sugar. The new drug, Zepbound, adds a second molecule that acts like another hormone, known as GIP.
Although GIP has had a more modest effect when administered alone, it increased GLP-1’s effects when given together. In 72-week clinical trials involving 2,500 people, participants receiving the highest dose of Zepbound lost an average of 18% of their body weight. This was slightly more than for Wegovy, where clinical trial participants lost an average of just under 15% in 68 weeks.
Does this mean people should switch from Wegovy to Zepbound? Not necessarily. Someone might shed pounds on one drug but lose little to no weight on the other. Plus, both drugs have relatively high rates of side effects, chiefly gastrointestinal issues like nausea and diarrhea. If you’re tolerating one well, a change could bring unwanted problems.
There’s also the issue of availability. These drugs are — and will be — in such high demand that if you’re able to get one of them, consider yourself fortunate.
And there’s the issue of cost and insurance. Both drugs are quite expensive, and insurance coverage varies from plan to plan. So, again, if you have an arrangement that works for you in terms of economics, be very cautious before switching things up.
The bottom line is that both drugs have shown results that, until even a few years ago, would have been unimaginable. If you are interested in whether one might be appropriate for you, talk to your healthcare provider.
James, a physician-scientist, is executive vice president and chief medical officer of the Oklahoma Medical Research Foundation. Cohen is a marathoner and OMRF’s senior vice president and general counsel. Submit your health questions to firstname.lastname@example.org.