In many ways, these are the best of times for Silicon Valley’s buzziest crop of longevity startups and their pursuit of drugs that can reverse aging.

NewLimit, a cell reprogramming company co-founded in 2022 by Coinbase CEO Brian Armstrong, announced earlier this month that it had raised another $435 million and plans to start testing a drug in humans next year. In all, it has collected over $630 million in funding.

Retro Biosciences, a startup launched in 2022 with $180 million from OpenAI’s Sam Altman, announced last month it too has raised more money and now has a $1.8 billion valuation. Retro, which is trying to restore cells and their activities that decline with aging, started testing its first drug in people last year.

Life Biosciences, a cell reprogramming company founded in 2017 whose investors include Joe Lonsdale’s 8VC, raised $80 million earlier this year, enough to complete the early phase of a clinical trial for its first drug. The company said this week it has dosed its first patient.

And yet despite these milestones, when I asked the CEOs of these companies if they are running trials for longevity drugs, each of them responded: Not yet.