Exclusive: Khosla Ventures backs startup selling ‘therapeutic plasma exchange’ at longevity clinics

Circulate Health, a startup offering a potential anti-aging procedure, has raised $12 million in seed funding led by Khosla Ventures, the companies told Endpoints News in exclusive interviews.

The startup’s procedure, called therapeutic plasma exchange, is already being offered at clinics for about $8,000 to $10,000 a session. That makes it a somewhat unusual business for Khosla’s biotech team, which typically invests in companies, including longevity-focused ones, developing new treatments that require years of testing and vetting by regulators before commercializing them.

Alex Morgan, a partner at Khosla, told Endpoints that Circulate was an attractive investment because the company can begin collecting data — from paying customers — “without deploying a tremendous amount of capital to see whether it works,” he said. Early data “are suggestive that it will provide benefit, and we’re going to try to figure out what that benefit is, and how beneficial,” Morgan added. Seaside Ventures and CSC Ventures also contributed to the seed funding.

Replacing plasma

Plasma exchange is an existing medical procedure sometimes used to remove problematic antibodies that cause autoimmune diseases. A patient’s blood is extracted, and blood and immune cells are then separated from plasma, the liquid portion of blood that contains other molecules. The cells are returned to the patient along with additional fluid to make up for the lost volume.

Circulate’s process is largely the same, but the company is pitching it as a way to improve healthspan. “This is an off-label use for an FDA-cleared device,” CEO and co-founder Brad Younggren said. The process can take a few hours and removes as much plasma as safely possible, usually two to three liters, he added.

Therapeutic plasma exchange has recently garnered attention among alternative health promoters and the longevity crowd, with recipients of the procedure sometimes posting pictures holding their bag of plasma. It’s an offshoot of a previous trend of companies offering transfusions of “young blood,” sourced by people in their teens and 20s. Young blood transfusions, however, drew ire from the FDA, which warned of risks from the unproven and potentially dangerous therapies in 2019 and 2024.

In Circulate’s case, rather than putting allegedly helpful things into the bloodstream, it is centered on removing potentially harmful molecules that it believes accumulate in the bloodstream with age. “We take out all of the inflammatory cytokines and proteins,” Younggren said.

The startup has its own clinicians that perform the procedure at existing sites, most of which brand themselves as “longevity clinics,” Younggren said. The new funding will help Circulate double from 22 to more than 40 clinics by the end of the year, including its first locations outside the US, he added.

Plasma exchange for longevity

Khosla has been quietly building Circulate for a few years based on work from its co-founder Eric Verdin, a prominent longevity researcher.

The startup ran a small clinical trial with Verdin’s Buck Institute for Research on Aging, testing plasma exchange in 42 healthy people in their 60s on average. Participants got the treatment a total of six times either monthly, twice a month, or twice a month along with an intravenous immunoglobulin (IVIG) infusion to make up for the antibodies sucked out during the plasma removal. Ten people in the study got a sham procedure.

The study, published in Aging Cell in May, notes that people who got the therapy had fewer inflammatory proteins in their blood. But the measure the Buck Institute and Circulate have promoted the most is a 2.6-year reduction in “biological age,” a number that can be higher or lower than a person’s chronological age.

Changes to the biological age are not proven to be meaningful for long-term health, and the results varied widely depending on what treatment regimen participants got and which test was used to assess biological age. The study is more blunt about tangible impacts on health, noting that “[t]here were no clinically meaningful changes (e.g., functional, cognitive, or symptomatic) observed or assessed in this short-term study.”

But the company and its investors believe the potential benefits make it worth offering.

“This therapy could have a powerful impact, but it will take years to see how this evolves, because we’re going to treat people and see what happens to them,” Morgan said. “It’s safe. I think people should have a chance of being able to go get it as long as they’re well informed.”

The funding will also pay for additional studies, including one using Circulate’s procedure to remove microplastics from the blood. Younggren said he envisions future studies for moving other toxins like mercury and PFAS too. Morgan mentioned the startup is interested in investigating the impacts of plasma exchange on brain health and cognition.

“There’s a bunch of other research we want to do,” Younggren said. “We have a bunch of ideas about new indications, new reasons why people would get this.”