Jesse Karmazin, the 34-year-old founder of the startup Ambrosia, had a pitch journalists couldnt resist: For a fee, he could help his clients combat aging and its related ills with infusions of blood plasma from the young. Teen donors, vampiric undertones, a serious-sounding study, an $8,000-per-person price tag and rumors that venture capitalist Peter Thiel might be interested earned Ambrosia more than 100 press mentions in just two years.

The effects of young plasma, Karmazin told reporters, were astounding. Just one infusion dramatically improves peoples appearance, their memory and their strength, he told one reporter . I want to be clear, at this point, it works. It reverses aging, he told another . Im not really in the camp of saying this will provide immortality but I think it comes pretty close, he told a third , adding, Its like plastic surgery from the inside out.

The free publicity helped Ambrosia attract clients : One hundred and four people paid to receive plasma from 16- to 25-year-old donors as part of Ambrosias participant-funded study, Karmazin told HuffPost.

But despite declaring the study a success and announcing plans this week to accept new clients, Karmazin never showed any proof that the transfusions actually helped people. In the media, he touted impressive results, but almost a year after his study officially concluded in January 2018, he hasnt released them. Scientists have criticized the study as flawed and the procedure as medically unnecessary and not without risk ; in rare cases, transfusion complications can be fatal . One of the doctors Karmazin hired had previously been disciplined by a state medical board for unprofessional conduct. Karmazin himself cannot legally practice medicine in any state; he is explicitly prohibited from practicing in Massachusetts by authorities. Ambrosias president and chief operating officer quietly left the company in late December, leaving Karmazin as the sole employee. And the only patient who spoke publicly about Ambrosias transfusions treatments he hoped would help him live healthier into old age died at 65 after going into cardiac arrest.

Karmazin couldnt comment on individual patients but said there were no deaths during or after the trial related to the treatment.

HuffPost found that at least some of Karmazins young plasma came from a nonprofit blood bank in Texas that recruited teenage donors for saving lives, but noted on a consent form that their blood components could also be used for any other medical purpose.

The bank abruptly decided to stop selling young plasma after HuffPost reached out, according to an employee email.

Ambrosia, which declined to comment on whether the company has any investors, is only one of many firms investigating how to help people feel younger for longer . But Ambrosias ability to attract paying clients and years of positive press coverage without providing scientific data to back up its claims shows just how easy it can be for promises to outpace the research when Silicon Valley gold-chasing mixes with Americans fear of death.

You can easily imagine a situation where somebody whos vulnerable, and not wealthy, and not healthy, and may be desperate ... would potentially feel like they have no option but to spend this money, said Phuoc Le, a physician and global health specialist who teaches at the University of California, San Francisco.

They could literally spend their life savings on an unproven treatment, he said.

Doctor Karmazin

Karmazin was born in Palm Beach Gardens, Florida, and attended Princeton University, where he became a highly accomplished rower , going on to win a silver medal in the Paralympic Games in Beijing in 2008. He attended Stanford Medical School and participated in labs that focused on longevity and stem cell biology. His experience as an athlete and feeling slower athletically after turning 30 influenced his desire to work on aging as a treatable condition. After graduating in 2014, Karmazin started a residency at Brigham and Womens Hospital in Boston with a plan to eventually specialize in psychiatry. But as Karmazin tells it, he didnt like working the long hours and felt he didnt have time to pursue his other interests, transfusions and aging, in addition to general practice, so he left his residency in 2016 to start Ambrosia.

There is an asterisk to that story: On Feb. 29, 2016, Karmazin and his attorney signed a voluntary agreement with Massachusetts officials in which he promised to immediately stop practicing medicine in the state. Karmazin told HuffPost he signed the paperwork because he left his residency early, that doing so was pretty routine, there were no additional circumstances that he was aware of and thats all he knew. That account seems unlikely. Karmazin was practicing under a limited license; such a license terminates automatically if a physician leaves a residency program early for any reason, according to George Zachos, the executive director of the Massachusetts Board of Registration in Medicine. The board wouldnt typically pursue such an agreement with a limited licensee for leaving a residency early, Zachos said. Such a public agreement is used to protect patient safety. Last year, only 12 physicians in Massachusetts reached similar deals.

The boards review is confidential, but a representative noted the circumstances that led to the agreement were unrelated to Karmazins work with Ambrosia or xVitality Sciences, a separate rejuvenation project he also worked on.

Karmazin, who introduces himself as Dr. Karmazin, moved forward with Ambrosia after signing that agreement. He said he got the idea for young plasma transfusions from several studies in which young and old mice were surgically conjoined in order to examine the effects of mixing their blood . In some cases, the older mice became temporarily stronger and showed slight improvements to their health. Karmazin believed those results could be replicated in humans.

Scientists have questioned Karmazins interpretation of the data. Researchers at the University of California, Berkeley, who led conjoined-mice tests noticed small positive changes in older animals muscles, livers and brains. But the more important finding was the significant decline in the health of the younger animals. For the older animals, the young blood was largely diluted by the old blood.

There was much more negative effect from the stuff in the old blood than there was positive effect from the stuff in the young blood, said Irina Conboy, an aging and rejuvenation researcher at Berkeley, who compared young blood transfusions to taking a pile of rotten bananas and throwing one good one on top. Maybe there are secret sources [for human rejuvenation] in young blood, she said. But there is no scientific evidence for that.

Karmazin went ahead anyway: In the summer of 2016, he announced that he would charge people ages 35 and older $8,000 each for about 2 liters of young plasma as part of what he called a clinical trial. Karmazin didnt feel the need to go through the Food and Drug Administrations drug approval process , as plasma transfusions are already a well-established procedure. Most of the time, however, they are used to treat patients who have specific health issues , not carried out to potentially make people feel younger.

Ambrosias trial whipped up the flurry of press coverage that doubled as free advertising, and in some cases, suggested inaccurately that people were drinking young blood . But what really got people talking about Ambrosia was a report that Peter Thiel, the tech entrepreneur billionaire, was interested in young blood. Karmazin himself appears to have made the explicit connection to Ambrosia. In 2016, he told an Inc. magazine reporter that Jason Camm, chief medical officer at Thiel Capital, had contacted him to express interest in Ambrosia. Its not clear whether Camm was reaching out on Thiels behalf, or how extensive the alleged contact was. But the story prompted a wave of Thiel-vampire insinuations in the media . Later, in an interview with TechCrunch , Karmazin completely denied having contact with anyone from Thiel Capital, raising questions about who wanted to quash the story.

Camm and Thiel Capital did not respond to requests for comment. In November, Thiel said at the New York Times DealBook conference: On the record. Im not a vampire. He also said hes never injected himself with young blood. Karmazin reiterated to HuffPost that hes not in any contact with Thiel. When asked why his story appears to have changed, Karmazin repeatedly declined to comment.

Sweet Little 16-Year-Old Plasma

To launch his study, Karmazin needed plasma, the liquid part of blood, from young people. He needed a lot of it Ambrosia performed more than 150 roughly 2-liter transfusions (some clients reportedly returned for multiple treatments), according to Karmazin, which would have required at least 80 gallons of young plasma, hundreds of donations worth. But he faced a hitch: Blood banks dont typically separate out blood plasma by age and sell it for rejuvenation purposes; their primary mission is to provide donated blood for hospital patients and save lives.

When blood centers have unused plasma, they commonly provide it to different companies in order to make products to treat serious medical conditions such as hemophilia, according to a spokesperson for AABB, a nonprofit that accredits blood centers.

But it wasnt easy to find a blood bank willing to supply a startup for Karmazins purposes. In the beginning, Karmazin called some 20 blood banks, he said. It took a while to find the right partner, he added. There was interest, he claimed, but banks didnt have a process in place to get him the plasma he needed. HuffPost contacted more than a dozen U.S. blood banks, many of which cited ethical concerns and raised questions about Ambrosias study. The chief medical and scientific officer of Vitalant, a nonprofit that distributes blood to more than 1,000 U.S. hospitals, told HuffPost that Vitalant leadership contacted all its donation centers after hearing about Ambrosia to confirm none worked with the company. Ambrosias study didnt seem to be a legitimate clinical trial, Dr. Ralph Vassallo said, so Vitalant shouldnt be selling to the startup.

Eventually, Karmazin said, he found two blood banks to provide the company with excess young plasma that he could use for his study. Karmazin refused to say which ones they were.