As human lifespan increases, a greater fraction of the population is suffering from age-related cognitive impairments, making it important to elucidate a means to combat the effects of aging. Exposure of an aged animal to young blood can counteract and reverse pre-existing effects of brain aging at the molecular, structural, functional and cognitive level.

It was one of the most mind-blowing scientific reports: Injecting old mice with the plasma portion of blood from young mice seemed to improve the elderly rodents’ memory and ability to learn. Inspired by such findings, a startup company has now launched the first clinical trial in the United States to test the anti-aging benefits of young blood in relatively healthy people. But there’s a big caveat: It’s a pay-to-participate trial, a type that has raised ethical concerns before, most recently in the stem cell field.

The firm’s co-founder and trial principal investigator is a 31-year-old physician named Jesse Karmazin. His company, Ambrosia in Monterey, California, plans to charge participants $8000 for lab tests and a one-time treatment with young plasma. The volunteers don’t have to be sick or even particularly aged—the trial is open to anyone 35 and older. Karmazin notes that the study passed ethical review and argues that it’s not that unusual to charge people to participate in clinical trials.

To some ethicists and researchers, however, the trial raises red flags, both for its cost to participants and for a design that they say is unlikely to deliver much science. “There’s just no clinical evidence [that the treatment will be beneficial], and you’re basically abusing people’s trust and the public excitement around this,” says neuroscientist Tony Wyss-Coray of Stanford University in Palo Alto, California, who led the 2014 young plasma study in mice.

Decades ago, so-called parabiosis studies, in which the circulation of old and young animals was connected so that their blood mingles, suggested that young blood can rejuvenate aging mice. A recent revival of the unusual approach has shown beneficial effects on muscle, the heart, brain, and other organs, and some researchers are scrutinizing young blood for specific factors that explain these observations. The study, however, suggested that repeated injections of plasma from young animals were an easy alternative to parabiosis. Wyss-Coray has since started a company, Alkahest, that, with Stanford, has launched a study of young plasma in 18 people with Alzheimer’s disease, evaluating its safety and monitoring whether the treatment relieves any cognitive problems or other symptoms. The company covers the participants’ costs. Wyss-Coray expects results by the end of this year. (Another trial at a research hospital in South Korea is examining whether cord blood or plasma can prevent frailty in the elderly.)

Read also: Chinese Medicine Reveals The Top 5 Golden Points In Our Bodies With Incredible Anti-Aging Benefits

In Ambrosia’s trial, 600 people age 35 and older would receive plasma from a donor under age 25, according to the description registered on ClinicalTrials.gov, the federal website intended to track human trials and their results. Karmazin says each person will receive roughly 1.5 liters over 2 days. Before the infusions and 1 month after, their blood will be tested for more than 100 biomarkers that may vary with age, from hemoglobin level to inflammation markers. The $8000 fee—not mentioned on ClinicalTrials.gov—will cover costs such as plasma from a blood bank, lab tests, the ethics review, insurance, and an administrative fee, Karmazin says. “It adds up fairly quickly.”

Ambrosia’s trial has already attracted attention from the investment company of billionaire Peter Thiel, who is apparently interested in trying young plasma treatments himself, Inc. reported today.

Karmazin says he’s filling a void, suggesting that most companies wouldn’t be interested in developing human plasma as an anti-aging treatment.

“It’s this extremely abundant therapeutic that’s just sitting in blood banks,” he insists.

Watch the video bellow:

Read also: 5 Tibetan Exercises You Should Do Every Day To Stay Youthful And Energized

Sources used: Nature, Science Mag