On Wednesday, pharmaceutical giant Eli Lilly sued four prominent telehealth companies that offer more affordable, off-brand versions of its patented best-selling GLP-1 medications Mounjaro and Zepbound. Together, the drugs accounted for over $16.4 billion in revenue for the company last year. It’s the latest escalation in an ongoing war between the drug industry and health care providers over what are widely seen as the most effective—and lucrative—drugs for treating obesity and diabetes to come on the market in years.

The lawsuits target four telehealth brands, Mochi Health, Fella & Delilah Health, Willow Health, and Henry Meds. Eli Lilly alleges that each company is selling illegal knockoffs of its drugs, in some cases, with untested added ingredients like vitamins and amino acids in an attempt to distinguish them from its name-brand medications.

None of the companies named as defendants immediately responded to requests for comment from WIRED about the lawsuits. In response to general questions about its business practices, Mochi Health said in a statement that it offers compounded GLP-1 medications that are “customized for medical necessity."

“Their use remains appropriate and legal when tailored to individual patient needs and prescribed by a licensed medical provider—not as mass-market substitutes for branded medications,” Mochi Health said. Fella & Delilah Health, Willow Health, and Henry Meds did not respond to questions about its business practices in time for publication.