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March 3 (Reuters) - The U.S. Food and Drug Administration has issued warning letters to 30 telehealth companies for making false or misleading claims about compounded versions of popular GLP-1 weight‑loss drugs, the agency said on Tuesday.

It said some companies made claims that their compounded products were the same as approved GLP‑1 drugs, and also hid where the products came from by branding the drugs with their own names in a way that made it look like they were the manufacturer.

This marks the second group of such letters, following warning letters the FDA sent in September to companies that make or sell weight-loss drugs, including Eli Lilly LLY.N, Novo Nordisk NOVOb.CO and telehealth firm Hims & Hers Health HIMS.N as part of President Donald Trump's order to crack down on drug advertising.

"It's a new era of enforcement," FDA Commissioner Marty Makary said in a statement, warning that companies should not try to "circumvent FDA's approval process by mass-marketing compounded drugs."

In the latest letters, the FDA said the telehealth firms had made false or misleading claims about compounded semaglutide and tirzepatide products on their websites, with few also cited over a third drug, liraglutide.

Semaglutide is the active ingredient in Novo Nordisk's Wegovy and Ozempic, while tirzepatide is used in Eli Lilly's Zepbound and Mounjaro. Liraglutide is sold by Novo Nordisk as Saxenda.

The companies have been given 15 working days to respond in writing and outline steps to correct the violations.

Hims & Hers came under scrutiny after the FDA warned in February that it could take action over the company's $49 compounded weight‑loss pill. That same month, Novo Nordisk escalated the dispute by suing the company.

Compounded drugs are customized medicines made when a licensed pharmacist or physician combines, mixes or alters drug ingredients to meet the needs of an individual patient, according to FDA.

(Reporting by Kamal Choudhury in Bengaluru; Editing by Shinjini Ganguli)

((Kamal.Choudhury@thomsonreuters.com;))