Big Success for Anti-obesity Drug

Will an expensive, new, injectable, untested medication help people lose weight?

Maybe! But right now, we don’t know if it’s safety and efficacy profiles make it worth the price.

When I saw this headline on an article in The Week magazine, I was impressed. Diet and exercise, when combined with existing obesity drugs, typically result in only a 10% weight loss; this new drug produced a 22.5% weight loss, or about 52 pounds. That sounds fantastic, but my enthusiasm quickly abated as I learned more.

In the first place, it was not intended to be an anti-obesity drug. Eli Lilly’s tirzepatide, brand name Mounjaro, was recently approved by the FDA to treat type-2 diabetes. It is given once weekly by subcutaneous injection. It is the first and only combined GIP and GLP-1 receptor agonist. Another injectable drug, Wegovy (semaglutide) was previously approved to help manage weight loss in combination with reduced-calorie diet and exercise in patients with obesity or overweight who have at least one weight-related condition such as high blood pressure, type 2 diabetes, or high cholesterol. It targets only GLP-1. I wrote about semaglutide here. GIP has been shown to decrease food intake and increase energy expenditure.

Mounjaro is not indicated for type 1 diabetes and has not been studied in patients who have had pancreatitis. It can cause thyroid cancer and there is a long list of side effects, some serious, including gall bladder and kidney problems and changes in vision. Its use for weight loss is based on what might be considered a side effect. That’s not necessarily a problem. Minoxidil was originally a blood pressure drug and was approved for treatment of hair loss after many reports of unexpected hair growth.

The retail price has been set at $12,666 a year.

The company intends to ask the FDA to approve Mounjaro for weight loss, but the study has not yet been published and the data has not been submitted for peer review.

Conclusion: Stay tuned

Tirzepatide sounds very promising as a drug to help obese and overweight people lose a substantial amount of weight (in conjunction with reduced calorie diet and exercise), but it will be expensive and is not without risk. I am cautiously optimistic but must withhold judgment for now. More research is needed, and FDA approval has not yet been granted.

This article was originally published in the Science-Based Medicine Blog.

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine Blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.

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