Roger Crystal was the on-call surgeon at University College Hospital in London on July 7, 2005, when a series of explosions in the Underground killed 56 people and injured more than 700. Terror victims streamed into his operating room. Even so, his toughest case that day, he says, was a heroin addict who’d contracted a flesh-eating infection from a dirty needle. “He was lying there with his liver and intestines exposed, and all he wanted to do was shoot up on heroin,” Crystal says. “That’s when I realized just how bad a disease addiction can be, how dysfunctional the circuitry of the brain can become.”

He could provide care at the individual level, but the problem of addiction required a population-level solution. Crystal quit his medical career to pursue an MBA from London Business School, then did a stint at Goldman Sachs Group, worked on acquisitions and licensing deals at GE Healthcare, and consulted for companies that treat diabetics. When the opportunity arose to become chief executive officer of Lightlake Therapeutics in 2009, Crystal saw his opportunity.

Researchers at Lightlake—now called Opiant Pharmaceuticals Inc.—were developing a version of the drug naloxone, which blocks addiction pathways in the brain, that could be administered as a nasal spray. Naloxone had been used since the early 1970s to reverse heroin overdoses, but per U.S. regulations it could only be marketed for use intravenously, making it relatively hard to use—one study found it to be effective only 59 percent of the time when administered by a layperson.

The intranasal formulation is easy to administer and can be counted on to work every time. “It’s as user-friendly as it gets,” says Dr. Nora Volkow, head of the National Institute on Drug Abuse, which helps fund Opiant’s research. “People don’t realize, because it’s not sexy—you’re just changing the delivery system—but to be able to deliver the drug at concentrations equivalent to injection is a big, big deal.” In 2015 the company received U.S. Food and Drug Administration approval for its naloxone product, Narcan, which is now available over the counter in most states. Crystal’s next goal is a heroin vaccine: a one-time treatment that would trick the body into thinking heroin molecules are a disease, prompting the immune system to destroy the drug before it reaches the brain.

In the past, it’s been difficult to secure funding for clinical trials of a drug that would most benefit people who tend to be incarcerated or uninsured and likely unable to afford expensive treatment. With the income from Narcan to bolster it, Crystal thinks Opiant can be a critical bridge between scientists and the world of retail medicine. “You have the most brilliant minds, who are restricted by being in a government or academic setting,” he says. “Then you have our company: We’re that transition zone out of clinical development.”