"You're not 100 percent sure if you're having a totally positive or totally negative impact in the world when you're working in consumer internet," Parker explained at the Wired25 conference in San Francisco on Monday.
"You're spending a lot of time trying to make your products as addictive as possible. Transitioning to life sciences is incredibly refreshing, because you really feel as though the energy and time you are putting into it are helping people. It's about saving lives, really changing people's lives, advancing medicine."
Parker said he could never have predicted the impact Facebook would have on today's world, pointing out the move to mobile made it "ubiquitous" and "rewire(d) the fabric of society." In 2016, he started the Parker Institute for Cancer Immunotherapy (PICI) to develop better cancer treatments.
"I, at some point, got a little bit frustrated with the monoculture of the consumer internet world," Parker said. "It feels somewhat unsatisfying to constantly make products for teenage girls.... You worry about what this effect may be having on their development and on society."
It was refreshing to work with scientists instead of Silicon Valley entrepreneurs, he said.
"Every 22-year- old shows up at your doorstep with this sort of belief that they are going to be the next Mark Zuckerberg, and they deserve to be a billionaire, and their company deserves an absolutely obscene valuation," Parker said.
Scientists find the work itself "the true reward," Parker said. His new work reminds Parker of the early days working on the Internet when people like him were more interested in making products that were "great for the world."
"Scientists have a level of humility where they have quite a bit of pride in their work, and being published is important, and being recognized by your peers is important, and having an impact on patients is important - but scientists aren't running around trying to get rich and don't have the same distorted expectations about how rich they are going to become," he pointed out.