New obesity drug Mounjaro launches in Korea — is it worth switching from Wegovy?

Boxes of Ozempic and Mounjaro, semaglutide and tirzepatide injection drugs used for treating Type 2 diabetes and made by Novo Nordisk and Eli Lilly, respectively, are seen at a Rock Canyon Pharmacy in Provo, Utah, U.S., March 29, 2023. Reuters-Yonhap

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Korea’s obesity treatment market has reached a turning point as Eli Lilly’s diabetes and weight loss drug Mounjaro (tirzepatide) began distribution to pharmaceutical wholesalers on Aug. 14. The move sets the stage for a head-to-head competition in efficacy and price with Novo Nordisk’s Wegovy (semaglutide), which is already on the market.

According to Eli Lilly Korea, wholesalers will begin full-scale distribution on Aug. 20, with prescriptions expected at medical institutions as early as Aug. 21.

Mounjaro’s biggest selling point is its strong weight-loss effect. Clinical trials showed that Wegovy users lost an average of 14.9 percent of body weight after 68 weeks, while Mounjaro users lost up to 22.5 percent after 72 weeks. Both drugs were originally developed for diabetes treatment and also improve blood sugar control.

“In clinical practice, some patients were able to stop insulin or significantly reduce oral diabetes medications, and some who were prediabetic returned to normal blood sugar levels,” said Cho Young-min, a professor of internal medicine at Seoul National University Hospital.

On the difference in weight-loss effects, Cho said, “For non-diabetic patients, Wegovy results in about 15 percent weight loss and Mounjaro about 20 percent. The difference is roughly 5 percent, and Mounjaro can be considered slightly stronger, though that’s just an estimate.”

Vials of Eli Lilly's Mounjaro, a tirzepatide injection drug used for treating Type 2 diabetes and weight loss, are placed on a table for a photograph in a health clinic in Hyderabad, India, April 14. Reuters-Yonhap

Asked whether Wegovy users could switch to Mounjaro, Cho noted that “there are no official studies on drug switching yet,” but added, “It wouldn’t make sense for a patient on a high dose of Wegovy to start Mounjaro at the lowest dose. It might be better to start at a mid-level dose.”

‘Muscle loss is a bigger concern than temporary digestive side effects’

Oh Sang-woo, a professor of family medicine at Dongguk University Ilsan Hospital, said both Mounjaro and Wegovy can cause gastrointestinal side effects such as nausea, bloating, constipation and diarrhea as the dose increases. “These symptoms are usually temporary, but the real side effect to watch out for is muscle loss,” he said.

“The faster you lose weight, the more pronounced the muscle loss. If you lose too much muscle, rebound weight gain can happen quickly when you stop the drug,” he explained, stressing the importance of balanced nutrition and regular exercise to maintain muscle mass.

Oh added that younger people and those with higher muscle mass, regular lifestyles and proper diet control tend to lose weight faster. Men generally lose weight slightly faster than women, though pancreatic function, insulin resistance and other factors vary widely among individuals.

Price war lowers starting monthly cost to 200,000-300,000 won range

Mounjaro entered the market with aggressive pricing. Eli Lilly set the supply price for the lowest 2.5 milligram dose at 278,000 won ($204) for four weeks — about 25 percent cheaper than Wegovy’s starting dose price. However, higher doses such as 7 milligrams are expected to exceed 500,000 won.

In response, Novo Nordisk announced price cuts for Wegovy ranging from 10 to 40 percent depending on dose. The starting 0.25 milligram dose is expected to be supplied at around 220,000 won, 40 percent lower than before. Previously, all Wegovy doses were priced at about 370,000 won, but the company is shifting to a tiered pricing system.

Industry officials expect the price competition to lower the monthly cost for starting doses to the 200,000-300,000 won range.

This article from Kormedi.com, Korea’s top health care and medical portal, is translated by a generative AI system and edited by The Korea Times.