Forever Young

Now on his fifth startup, Unity Biotechnology, Ned David has the blueprint for creating a lucrative biotech. His latest project: a company that will take on the ravages of aging. The idea behind Unity -- preventing aging -- sounds crazy, but it's backed by dozens of scientific papers, the key two in Nature. There are aging cells, called senescent cells, that build up throughout the body and contribute to what people think of as old age -- things like achy joints, waning vision, even perhaps Alzheimer's. Kill those senescent cells with drugs, David reasons, and people might be able to grow old without becoming infirm. It's an amazing goal, backed by great science, not to mention $222 million in venture capital and $85 million raised from a May initial public offering, which valued Unity at $700 million, flat with its last fundraising. But achieving that goal also entails incredible risk.