It was a Saturday night in November 2010. At Café des Amis on Union Street in San Francisco, Parker and legendary angel investor Ron Conway—both part owners of the place—were sitting across from each other at a crowded banquette at what amounted to a family dinner. Ron’s wife, Gayle, was next to him; Alexandra Lenas, Parker’s new girlfriend and future wife, was curled up beside him. Still, the crowd was boisterous, and it was so loud that Parker had to shout to be heard.

“I’m going to cure cancer!” he yelled.

The outburst was vintage Sean. “We’d both had plenty of wine,” remembers Conway, who has known Parker, now 36, since he was an “edgy” 19-year-old—a daredevil hacker from Herndon, Va., whose music file-sharing company would almost single-handedly humble the recording industry. Conway, now 65, had mentored Parker through nearly every company he had helped start or lead—Napster; Plaxo, an automated address book that had made clever, if infuriating, use of viral marketing; and of course Facebook, the college-dorm-project-turned-juggernaut that had made Parker truly rich. (When the company went public in May 2012, Parker’s 66 million shares turned him into an instant paper billionaire. Sources close to him say that he’s currently worth between $2 billion and $3 billion.)

Conway had seen Parker’s eyes go moonlike before; he had seen him dance from one “world-changing” project to the next. But something about this declaration on this night felt different: “He looked me in the eye and said it again: ‘I’m going to spend the rest of my life curing cancer. There are not going to be any more Lauras in the world.’ ”

“Laura” was Laura Ziskin, a petite, radiantly effusive woman who had produced the blockbuster Spider-Man franchise, Pretty Woman, and dozens of other movies and who had co-founded the Stand Up to Cancer movement. In the short time since Parker had met her, at a 2009 retreat on philanthropy in Tuscany, they had become exceptionally close. And when Ziskin’s breast cancer had reemerged with brutal efficiency after a long remission, Parker had managed to get her into a last-ditch immunotherapy protocol at the Hutch, the famed Fred Hutchinson Cancer Research Center in Seattle—chartering private planes at his own expense to shepherd her back and forth from Los Angeles.

“Most of the dinner conversation at Café des Amis that evening was about Laura’s cancer,” Conway recalls, “and why they had to try everything possible to save her.” Parker was deeply affected. Conway had no doubt about that. After dinner, as the party ­headed for home, the valet took the older man’s ticket and turned to get his car. “I said, ‘No, no, no, no! You get Sean Parker’s car first. Because he, as of an hour ago, is curing cancer!’ ”

Immunotherapy research pioneers Carl June (left), Jedd Wolchok (center), and Jim Allison are among those partnering with PICI. Photograph by Winni Wintermeyer for Fortune Magazine

When that story is relayed to Parker, he cringes—and waves it off as a sign of his mentor’s knack for hyperbole. But sub in the more Parkeresque verb “hack” for “cure,” and the claim no longer seems far-fetched: Sean Parker is going to hack cancer.

Well, yes—he is.

A hack, the way Parker defines it, is “a clever work-around or a clever way of leveraging an existing system to do something you didn’t think it was going to be able to do.” By that definition, just about every memorable entry on Parker’s steadily growing curriculum vitae, from Napster and Facebook to current projects like music-streaming company Spotify and in-home movie service The Screening Room, counts as a hack. Why wouldn’t medical ­research—one of the most labyrinthine, bureaucratized, and slow moving of all important human endeavors—be ripe for a creative work-around of its own?

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In mid-April—in an over-the-top, celebrity-gawking, Lady Gaga–serenading event that brought 900 people in black tie to his 2½-acre backyard in L.A.’s Holmby Hills neighborhood—Parker announced a $250 million cancer research hack that he’d been working on quietly, diligently, for three years: the Parker Institute for Cancer Immunotherapy. PICI (pronounced “pie-sea”), as it’s called by its member scientists, is doing something unprecedented in academic medicine: combining and coordinating the efforts of six of the top cancer immunology centers in the country—MD Anderson Cancer Center, Memorial Sloan Kettering, Penn Medicine, Stanford, UCLA, and UCSF—in order to greatly expand and, more important, to accelerate our understanding of why some immune-based treatments work miraculously in some patients and not at all in others. Carl June, an oncologist at Penn and a PICI team member, says he almost can’t believe Parker pulled it off. “Never before would I think you could get all these institutions to sign the exact same document,” he says.

With a critical mass of 450,000 patients annually among them, the six centers have agreed to combine their efforts on planning clinical trials in immunotherapy, recruit patients quickly, and share the information learned—which could be the single biggest factor in speeding up drug development. They’ll set up common platforms and standards for sharing and storing data. And perhaps most meaningful of all, PICI will manage all the intellectual property—the discoveries, new drugs, new tools, new technologies—that come out of the six member groups, splitting any revenue generated from this IP between the institute and the sites.

“Centrally managing the IP is an important break from the way that things are traditionally done,” says Jedd Wolchok, a medical oncologist and the director of the PICI center at Memorial Sloan Kettering. “But even bigger is that the royalties and licensing go into a collective communal fund, if you will, that is redistributed to the individual scientists. So essentially, if the [Parker] experiment works, this becomes a self-perpetuating entity.”

It may all sound like more of a logical next step than a revolution—until you come to understand, as Parker has, just how fragmented the cancer-research community has become. Lack of money isn’t the main problem. There’s much in what Parker calls our “dysfunctional human systems” that is getting in the way of anti­cancer efforts throughout academia, government, and industry: the zeal for secrecy among competitors that prevents the quick sharing of ideas, tools, and platforms; the frenzy of grant applications and publication that keeps brilliant scientists from their real work; the inherent caution, baked into the regulatory system and medical culture itself, that slows the testing of promising ideas in clinical trials.

There have to be hacks for these too, Parker thinks. By now we’ve been talking in his luminous, book-strewn office in his Holmby Hills house for nearly two hours. Every few minutes he clears his throat, as though he needs to catch his breath. “Between the pure science in an academic model, in the ivory tower, so to speak, and the ultra-­cutthroat laser focus of a biotech, we have to somehow bridge those two worlds in order to get [therapies] to patients” faster, Parker says. In his dark sweater and pants and red beard, he looks a bit like a beat poet. But a moment later, when he’s describing his own function in PICI, he’s back to being a venture capitalist. His role? “To program the organization to pursue commercialization of therapies.” If it works, Parker notes, PICI could be a force for cancer research for decades to come. “But that depends on us having hits,” he says. “I sound like a record executive now: We’ve gotta have hits.”

For now, PICI is bringing disparate scientists to the table with funding that’s gargantuan by academic-research standards. Every hospital “gets a big chunk of money upfront—between $20 million and $35 million, depending on the institution,” says Jeff Bluestone, a UCSF scientist who’s now the Parker Institute’s president and CEO. Each can use it to study pretty much what­ever he or she wants, so long as it fits PICI’s strategic road map—and so long as it involves cancer immunotherapy.

Parker (left); Jeff Bluestone (center), CEO of PICI; and Wolchok. Parker has become known for his deep dives into cancer research. Photograph by Winni Wintermeyer for Fortune Magazine

Immunotherapy differs from more traditional cancer treatments, such as surgery (cutting malignant cells out of the body), chemotherapy and radiation (poisoning the deadly mutants), and even the newer, more precise molecular drugs that attempt to jam the protein signals that tell tumor cells to keep dividing and conquering. Most immunotherapy strategies don’t take aim at cancer cells directly; rather, they rev up the immune system to be more aggressive in its interdiction, or they help it zero in on malignant cells more efficiently, or they silence the “stand down” messages the body sends to T cells, the immune system’s natural-born assassins, so that the cells can continue to seek out and kill their targets. The name given to this last strategy fits the Jason Bourne–like plotline underlying the biology: “checkpoint inhibition.”

Immunotherapy, in short, helps the body do the dirty work of defending itself against homegrown terrorists. And the approach, say a growing number of cancer experts, is both radically intuitive and radically promising. There are more than 80 immune-related cancer therapies currently in clinical trials, fueled by many billions of dollars in pharmaceutical investment from the likes of Bristol-Myers Squibb (BMY), Merck (MRK), Pfizer (PFE), and dozens of biotechs.

Sharon Belvin is one of the miracles—the kind of story that ­fuels the immunotherapy dream and has even long-term skeptics shaking their heads with wonder. Belvin was 22 years old in 2004 when she discovered a lump beneath her left collarbone—which turned out to be an outgrowth of a tumor in her lung. The New Jersey grad student had Stage 4 melanoma, a disease for which the five-year survival rate was just 17% (meaning five out of six patients die within five years of diagnosis).

Belvin was given heavy doses of chemotherapy—in 2004 that was almost all there was to offer. Her first IV infusions came in a toxic sweep on a Monday, Tuesday, and Wednesday. She got married that Saturday. “We had guest invites out to everybody—we had been planning this for a year and a half,” she says. Instead of the wedding dress she had picked out, she wore a white suit to cover the Port-a-Cath and tubes sticking out of her body. The cancer soon spread to her brain. Her chest cavity filled with 12 liters of fluid. Her body was breaking down. She couldn’t breathe.

When Wolchok, Belvin’s oncologist at Sloan Kettering, offered her the opportunity to participate in an immunotherapy clinical trial, she jumped at the chance. The trial involved an experimental checkpoint inhibitor from Bristol-Myers Squibb called ipilimumab (now marketed as Yervoy)—whose aim was to release the molecular brakes on her own army of T cells. She got one 90-minute infusion every three to four weeks; four treatments in all. That was it. The cancer never came back.

The never-coming-back part of the story is a critical element of this strategy’s appeal. Our immune system has a great memory. In treatment of melanoma, for example, a significant percentage of patients who enter full remission with immunotherapy remain there.

It is easy, of course, to get breathless about such uplifting tales. But the cancer immunotherapy saga is a long one, fraught with a century’s worth of hype and disappointment. Time magazine put an immune-boosting protein called interferon on its cover in 1980; Fortune did the same in 1985 with another immune protein called interleukin-2, hailing it as a “Cancer Breakthrough.” (It wasn’t, at least for most patients in most situations.)

That said, there is a growing sense among many cancer experts that immunotherapy could improve by leaps and bounds if the right mysteries are unlocked. The status quo for hundreds of thousands of people, meanwhile, is untenable: More than 333,000 Americans will be diagnosed this year in any of four cancer types in which the five-year survival rate remains lower than 20%, and in all, nearly 600,000 U.S. deaths are expected from cancer in 2016.

In the current phase of the war on cancer, the nation is in the midst of a hackapalooza. Or maybe “space race” is more apt. President Obama’s National Cancer Moonshot Initiative, announced in January’s State of the Union, follows Patrick Soon-Shiong’s Cancer MoonShot 2020, which joins MD Anderson’s Moon Shots Program on an already crowded launchpad.

Just two weeks or so before PICI’s debut, Johns Hopkins opened its own institute for cancer immunotherapy, with a $125 million gift from donors, including billionaires Michael Bloomberg and Sidney Kimmel. That, in turn, followed ambitious cancer efforts over the years by Michael Milken and the late Andy Grove, among others (read more here).

All of which raises the legitimate question of whether Parker’s new endeavor is worth getting Lady Gaga over. The answer lies partly in PICI’s collaboration model—and partly in Parker, who has immersed himself in cancer science in the way that few of his fellow philanthropists can match, according to some of the most prominent people in the field, inside PICI and out of it.

“Here is a guy who’s just like, wow, he gets it,” says virologist Larry Corey, president and director emeritus at the Hutch. “He asks ­really great questions that lead to things. And he’ll stop for a minute and think. Then all of a sudden—bam!—out comes this great idea.”

Long before his fascination with cancer, Parker was drawn to the study of the immune system by his own profoundly serious food allergies. He takes corticosteroids and carries Benadryl and an EpiPen for emergencies, but he has still ended up in the ER a number of times. Autoimmune disorders run in his family: His mom suffers from Hashimoto’s disease, in which the immune system attacks the thyroid gland.

His family history is part of the connect-the-dots Parker plays without end, reading late into the night, swimming in medical papers, diving into conversations with researchers of any stripe—discussing malarial vectors with Sir Richard Feachem at UCSF and checkpoint inhibitors with Jim Allison, a groundbreaking immunotherapy researcher at MD Anderson in Houston. “The first time I met him, we talked for about an hour,” recalls Allison. “After that I actually went to San Francisco and met him at a hotel, and we talked for about three hours. I was amazed. He operates at the level of a really well-trained graduate student—if not better.”

It’s a kind of seriousness belied by the lighter, harder-partying side of Parker’s personality. That image was cemented in the public mind, and in a not-so-positive light, by David Fincher’s movie The Social Network, in which Parker was played by Justin Timberlake as a self-serving, callous playboy. (Parker calls the depiction a “caricature,” and in 24 interviews for this story, I couldn’t find a single person who thinks of Parker that way or who could identify anyone who did.) Still, the Hollywood version wasn’t entirely fiction. Marc Benioff, CEO of Salesforce (CRM), remembers meeting Parker years ago—“in his single days,” Benioff adds—when Parker was being profiled by another magazine. “He had a bottle of Maker’s Mark in his right hand that he proceeded to finish during the interview,” Benioff recalls. But then “Sean would also say these amazingly prophetic and visionary, insightful, brilliant things, and he has been quite prescient in thinking about some big trends.”

In the cancer fight, Parker’s brainpower is harnessed to a personal passion that anyone who’s lost a loved one to the disease can understand—the kind of passion that exerts its own gravitational pull. Even cancer doctors aren’t immune. Cassian Yee, an MD Anderson oncologist, recalls meeting Parker in September 2010. The doctor, who was then at the Hutch, had flown to Los Angeles from Seattle in the afternoon, and had waited an hour for Parker in the lobby of the swank Peninsula Hotel, where the young entrepreneur had been holed up for weeks in the wake of knee surgery—residing with a pair of finches that were flying about in his suite. (Someone had given them to Parker as a gift.) Then Yee and Parker, a pair of crutches by his side, took a limo to a Sony Pictures (SNE) studio in Culver City, where a televised fundraiser, Stand Up to Cancer, was being recorded that evening.

Backstage, Parker introduced Yee to Twitter co-founder Jack Dorsey and to Elizabeth Edwards—the wife of Sen. John Edwards—who had Stage 4 breast cancer and was donning a chic wig for the evening. (“Do you like my new do?” she asked.) Then he called over the show’s producer, Laura Ziskin—the friend whose breast cancer had returned with a vengeance.

“We want you to treat her with immunotherapy,” said Parker. Yee had been practicing oncology at the Hutch with this general approach for several years. He was a believer. But there were rules—the Food and Drug Administration had to sign off on each protocol, as did the Hutch’s own Institutional Review Board. “I can only treat melanoma patients right now,” he objected. “I don’t have approval.”

“We’ll send you to an island,” Parker ­offered—somewhere outside American jurisdiction.

After a bit more prodding, Yee agreed to apply to the FDA for a single-patient, or “compassionate use,” exemption to the agency’s strict rules on testing investigational new drugs. (He got the approval.) Weeks later, Yee realized that he didn’t have the equipment he needed to pluck out of Ziskin’s blood the rare (perhaps one in 100,000) T cells that could identify the subtle peptide markers on the surface of her cancer cells and attack the disease. The doctor sent a note to Ziskin explaining the delay and apologizing. The following week, two checks from Parker, totaling $600,000, arrived at the lab. “For: laser cell sorter,” the note said.

Parker was resourceful, but ultimately mortality triumphed over medicine. Ziskin died in June 2011. At the next Stand Up to Cancer benefit program, Parker delivered her eulogy.

Parker (center, in blue sweater) has built relationships among competing scientists at PICI retreats like this one in St. Helena, Calif. Photograph by Winni Wintermeyer for Fortune Magazine

I’m trying to figure out a way to say this,” starts entrepreneur Peter Thiel, who was Facebook’s first big investor, thanks largely to Parker, and who later brought on Parker at his VC firm, Founders Fund. In both technology and science, there are those who generate ideas and those who disseminate them, he explains. “And Sean is really good at both. We tend to think of there being some sort of tradeoff,” but in fact the skills are “deeply complementary.”

The reason his cancer initiative has such potential when others have failed is that Parker has both the vision and the ability to articulate it, says Thiel. And there’s another factor that will drive this forward, says Parker’s friend Benioff, of Salesforce. It comes down to the word “Why?”

“Sean doesn’t have a traditional motivational cause,” says ­Benioff. “He’s not doing this to be wealthy or to be known or to be significant. He is not doing this to be loved. He is doing this because he feels it. He feels it deeply inside him, and it’s coming through him in the way that a tree emerges from a seed in the forest. And he can’t actually stop it. It’s something that has taken him over.”

A version of this article appears in the May 1, 2016 issue of Fortune with the headline “Hacker, Bad Boy, Venture Capitalist, Disrupter, Healer. Can Sean Parker Hack Cancer?”

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