AARP’s personal investment was $60 million into a broader, $350 million collaboration called the Dementia Discovery Fund (DDF), as part of an effort to kick off its own “Disrupt Dementia” campaign. The DDF has a number of other big name partners including Bill Gates (who’s poured in $50 million of his own money into the fund), the NFL Players Association, and a whole host of pharmaceutical companies like Biogen, Eli Lilly, GlaxoSmithKline, Takeda, and others.

Fortune spoke with Steve Rusckowski, CEO of Quest Diagnostics, and AARP’s chief operating officer, Scott Frisch, about the collaboration—and the greater promise and peril in Alzheimer’s and dementia-related drug development and prevention.

“Right now, the two biggest killers are cardiovascular disease and cancer,” said Rusckowski. He’s right—heart disease and related conditions are responsible for about one in four American deaths. Cancers aren’t too far behind. But Alzheimer’s is catching up fast, especially in the wake of an aging population. And unlike heart disease or cancer, there hasn’t been a significant new medical advance in Alzheimer’s in about 15 years. In fact, there have been several heartbreaking R&D failures in the space in the last two years alone.

“Of the leading causes of death still around, Alzheimer’s is the only one without a cure or treatment,” notes Rusckowski, adding that a number of conditions like HIV and cancer have, on some level, been transformed into chronic conditions rather than death sentences thanks to the advent of new drugs.

AARP’s Frisch adds that this issue is one that is especially important to the organization’s membership of older Americans. “Of our 38 million members, so many say that staying mentally sharp is a top priority and top concern,” he tells Fortune. “[Yet] there is no known diagnosis, no single test you could have for Alzheimer’s, dementia, etc.”

That critical shortfall is what this dementia fund is setting out to solve. In part, that will involve experimenting with new ways of dealing with dementia-related disease, such as by seeking out how to prevent it in the first place. A prevention-focused model got a major boost in April when the Alzheimer’s Association and the National Institute on Aging released a new proposed framework focusing on that tactic.

But success will require answering questions that have gone frustratingly unanswered, such as which biological markers can be used to sniff out the basic roots of the disease (rather than just identifying the tell-tale signs after someone already has it).

The downstream effects could be dire barring progress. In America alone, 15 million people are expected to have Alzheimer’s by 2060, and caregivers for people with the disease and other dementia-related disorders (usually family and friends) provided a staggering 18.4 billion hours of unpaid care to the patients in 2017.

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