Zepbound passes Wegovy in weekly new US prescriptions for the first time

Eli Lilly's tirzepatide weight-loss injection Zepbound recorded 77,590 new U.S. prescriptions in the week ending March 8, 2024, passing Novo Nordisk's semaglutide injection Wegovy among new patients for the first time since Zepbound launched, according to IQVIA data published by JPMorgan in a weekly note and reported by Reuters ^[1].

The gap was narrow. Roughly 6,000 fewer new Wegovy prescriptions were filled in the United States that week ^[1]. And on the broader measure that counts every prescription filled, including refills for people already on treatment, Novo Nordisk kept its lead over Zepbound by 25,307 prescriptions ^[1].

A four-month shift

Lilly launched Zepbound in the U.S. in December 2023, more than two years after Wegovy was approved in June 2021 ^[1]. Reaching the top spot among new prescriptions about four months after launch signals how quickly prescribers and patients moved toward the newer option, though the weekly IQVIA figures capture prescriptions written and filled, not how long people stay on a drug or whether they can get it consistently.

Supply is part of the backdrop. Reuters noted that demand for these medicines has well outpaced supplies, as consumers seek treatments shown to reduce weight by as much as 20% ^[1]. Prescription counts in any given week can reflect what is actually in stock at pharmacies as much as what doctors prefer.

Zepbound and Wegovy are both GLP-1 drugs, a class originally developed for type 2 diabetes that also reduces food cravings and slows how fast the stomach empties ^[1]. Zepbound contains tirzepatide, the same active ingredient as Lilly's diabetes drug Mounjaro; Wegovy contains semaglutide, the same molecule as Ozempic and Rybelsus.

Investors did not treat the milestone as a decisive turn. Shares of Lilly were off about 1% and Novo about 2% on the day, during a down session for the broader market ^[1]. Novo Nordisk, Lilly and IQVIA did not immediately respond to Reuters' requests for comment ^[1].

The money at stake

Analysts see the obesity drug market reaching at least $100 billion by the end of the decade ^[1]. Data analytics firm GlobalData forecast $105 billion by 2029 and projected that Novo Nordisk would capture more than half of it with its GLP-1 portfolio, including Wegovy ^[1]. GlobalData also forecast that Mounjaro would be the top-selling GLP-1 with $33.4 billion in annual sales by 2029 ^[1].

GlobalData said in a report that GLP-1 drugs are on pace this year to surpass widely used cancer immunotherapies as the best-selling medicines, driven by trial data showing they can treat other health conditions and by a surge in celebrity and influencer endorsements ^[1]. Merck's cancer drug Keytruda is currently the world's top-selling prescription medicine, with more than $25 billion in annual sales ^[1].

The prescription data landed one week after the FDA approved Wegovy for lowering the risk of stroke and heart attack in overweight or obese adults who do not have diabetes ^[1]. Zepbound did not have a comparable cardiovascular indication at that time, based on this reporting.

Why it matters for patients

For people weighing these two drugs, the headline number is a market signal, not a measure of which medicine works better for any individual. The sources do not compare the two drugs head to head on weight loss, side effects or safety.

What the numbers do hint at is where access and attention are moving. A rising share of new prescriptions can affect which drug a pharmacy stocks, how manufacturers allocate limited supply, and how aggressively each company competes on price and distribution. Lilly said this week it partnered with Amazon's pharmacy unit to deliver prescriptions sent to its direct-to-consumer service LillyDirect, including Zepbound, and Lilly executive Frank Cunningham said the company was "very pleased" with the number of prescriptions filled through LillyDirect so far ^[1].

Insurance coverage is the other variable, and it is not addressed in this reporting. Wegovy's new cardiovascular indication could influence coverage decisions, but the sources do not say how insurers responded ^[1].

What happens next

Weekly IQVIA scripts are volatile, and a single week does not establish a trend. Whether Zepbound holds the lead in new prescriptions, and whether it closes the 25,307-prescription gap in total weekly prescriptions, is not yet known ^[1]. Novo Nordisk said last week it was confident it would launch a pill version of its experimental weight-loss drug amycretin this decade; currently, GLP-1 drugs in this comparison are injected ^[1].