Triazolen -

Elara’s grip tightened on the vial. “What remains is a machine. We are not meant to be eternal. Our meaning comes from our limits.”

News of Triazolen had leaked six months ago, stripped of nuance by financial forums and bio-hacker chat rooms. "The Age Pause," they called it. A pharmaceutical company in Zurich offered her two billion dollars for the patent. A consortium of longevity billionaires sent private jets. A desperate mother whose daughter had progeria—the rapid-aging disease—chained herself to the lab’s front door. triazolen

In simpler terms, it reversed aging.