Discovered in the 1880s, the myxoma virus is a deadly pathogen that was found to kill 99.9 percent of the European hoppers it infected. It was so effective in culling their numbers that Australians used it as a population control technique in the 1950s. McFadden, a 71-year-old Arizona State University researcher, has tried to decode just why the virus is so fatal for rabbits, yet isn’t even remotely deadly for humans.

But through research — which he conducted alongside his wife and occasional lab partner, Dr. Alexandra Lucas — McFadden happened upon another discovery beyond his wildest imagination: that this bunny-killing virus can actually attack cancer cells in humans … without harming a patient at all. “It will infect them [cancer cells], kill them, but leave the host alone as long as it is not a rabbit,” McFadden says.

That stunning finding is at the heart of OncoMyx Therapeutics, an Arizona-based biotech company that McFadden co-founded four years ago that’s quickly becoming a mainstay in the competitive industry to battle cancer. The company raised $25 million in series A funding in 2019. And in April, it presented preclinical data at the annual meeting of the American Association for Cancer Research that pointed to the effectiveness of myxoma-based treatments against non-small cell lung cancer. This success led to the closing of a further $50 million series B funding in December 2021.

“The purpose of the company is to bring genetic versions of this virus into human clinical trials,” McFadden adds. He and his team have yet to pinpoint the specific types of cancer they will target in their first clinical trials, but they’re keen to focus on areas that don’t have significant treatment options at the moment.

As his business partner, Steve Potts, says, launching OncoMyx Therapeutics wouldn’t have been possible if it weren’t for McFadden’s decades of studying the mysterious deaths of rabbits. “We are daily in contact, asking questions like, ‘Hey Grant, what if we did this with the virus. And he goes off and engineers it and tries it out. It’s almost like early R&D for us,” Potts says.

That research could prove pathbreaking at a time when America’s cancer burden is poised to explode. Almost 40 percent of the U.S. population will get cancer in their lifetime, according to the National Cancer Institute. And for McFadden, the stakes increased on a personal level after he became a cancer survivor himself. Luckily, his thyroid cancer was very treatable. “I went through normal therapy and the cancer is gone,” McFadden explains.

Still, the scare added new passion to his work. “There are a lot of cancers that don’t respond as well to current therapy, so those are the ones we want to see if we can make a contribution to — to see if we can help to treat the cancers that are not currently very well treated.”

Eric Bartee is working on similar research at the Medical University of South Carolina alongside Phoenix-area company Systems Oncology in a race to get to market. Bartee and McFadden are facing the same hurdle in finding partners with the interest and experience to produce the myxoma virus at a clinical grade level: They’re moving into uncharted territory, especially when it comes to manufacturing and regulatory approval. The difficulty is “finding a way to manufacture it in a way that is acceptable to the FDA in terms of purity and potency,” says Bartee.

Pursuing cutting-edge research can be frustrating, with no guarantee of the results you’re hoping for. In Lucas, McFadden has much more than just an understanding partner: She’s a comrade-in-arms who has aided and helped shape his research. An interventional cardiologist who also works at Arizona State University, Lucas collaborated with McFadden for years before they moved to ASU. They have two children and share a love for martial arts — both are black belts in Taekwondo. And then there is, of course, their shared passion for developing life-saving treatments.

It was in one of their late-night conversations that they realized the myxoma virus may have a role to play in cancer treatments. Lucas later tested their theory in her lab, discovering that a purified version of the protein the virus creates can be a therapeutic treatment for atherosclerosis — a condition where plaque builds up in arteries, blocking them.

“We’ve been together on this for years,” says Lucas, who met McFadden at McGill University in Montreal. It was during a cycling road trip in southern France that much of the path of their lives was determined. “We got married in 1976 after the bike ride,” Lucas says, adding that’s also when she decided to pursue her M.D. and when McFadden discovered his own career path. Fast forward to today, and the two are using that same drive and curiosity to potentially disrupt cancer care as we know it.