In Silicon Valley, some quests for the fountain of youth have most definitely won the backing of tech's leading names.

Sam Altman, OpenAI's CEO, personally invested $180 million to launch Retro Biosciences, which is working on ways to rejuvenate aging cells. CoinBase's Brian Armstrong co-founded NewLimit, which has raised over $200 million for a similar pursuit from investors that include Peter Thiel's Founders Fund. And Jeff Bezos reportedly helped bankroll a startup focused on life extension therapies, Altos Labs, which has amassed $3 billion in funding.

Then there are longevity startups like Mitrix Bio, a Pleasanton, Calif.–based company that's working with only $4 million in funding, none of it coming from the tech billionaires who lately have become enthralled by the idea of treating death like a correctable software glitch.