Punch “stem cells” into YouTube and your first hit looks like something from a seventh-grade biology textbook. Number two features a Duke sports medicine doc injecting a syringe of bright red liquid into a heavily tattooed shoulder. Number three, with more than 2.5 million views, is a miked-up Mel Gibson regaling Joe Rogan with tales about his 92-year-old father’s “miraculous recovery” following a trip to Panama to get umbilical cord stem cells. In the more than 11,000 comments on the video, many tout their own experiences with stem-cell injections. Others leave their emails and phone numbers, hoping for a last-ditch shot at survival for themselves or their family members with leaky hearts and stage four cancer diagnoses.

Since the mid-2000s, clinics have been selling expensive, unproven stem-cell treatments to any patient desperate enough to believe their claims of cures for everything from arthritis to autism. At first, these clinics operated almost entirely overseas. But for the past decade, they have flourished in the US without much of a fight from regulators, even as the experimental therapies they hawk have been tied to serious infections, several cases of blindness, and one patient’s death.

But the feds are no longer sitting on the sidelines. Earlier this month, the US Food and Drug Administration won a landmark case against US Stem Cell, a company that manages three large clinics in Florida where at least four patients were reportedly blinded. The injunction ruling on June 3 empowers the agency to stop the private clinic from injecting patients with a cellular cocktail centrifuged down from their own liposuctioned fat. That controversial practice is common at clinics across the country. Barring the decision being overturned on appeal, it cements the FDA’s position that anyone doing that is illegally peddling an unapproved drug.

Over the past two years, the FDA has been escalating its enforcement of such clinics. It has also sued a collection of clinics based mostly in California called the Cell Surgical Network (that case is ongoing). But it faces an uphill battle against the viral marketing tactics that the burgeoning stem-cell industry employs to keep patients pouring in.

“Rather than melting away, business is growing. That’s the anomaly,” says Leigh Turner, a bioethicist at the University of Minnesota who studies the stem-cell industry. In 2016 he calculated that 570 clinics were offering unproven stem-cell treatments in the US. By 2018, he reported in a study that the number had jumped to 716. Today, Turner feels comfortable saying that the US has crossed the 1,000-clinic threshold. “Despite the rule changes and the public hearings and more inspections and warning letters and the lawsuits, the market is still expanding at a rapid rate.”

It’s possible that there’s just a lag; it could take years for those FDA ripples to reach the market. More likely, says Turner, is that there’s too much money to be made with too few potential consequences. The FDA can’t sue all 1,000 clinics into submission, and whatever monetary penalties the agency might impose for noncompliance are likely to be recovered quickly by clinics charging between $3,000 and $15,000 per treatment.

Then there’s the ease with which stem-cell clinics reach potential patients online. They advertise their treatments directly to customers almost exclusively over the internet, flooding their Google searches with vague yet hopeful promises. Often, this involves the patient testimonial video—one of the most successful marketing strategies employed by stem-cell clinics. You can find them on clinic websites, blogs, Facebook groups, and YouTube.