Taking it in stride: 20 years after her MS diagnosis, marathon runner is as active as ever, thanks to advances in treatment | Canada Voices

Jennifer Pevec had been batting away the warning signs for months: the bone-deep fatigue, the recurring foot numbness. But as she neared the finish line of her second marathon, she lost feeling in her right leg and started tripping over her own feet. That’s when she knew. “Something was wrong.”

Soon after, Ms. Pevec was diagnosed with multiple sclerosis. At 36, she had to step away from a high-intensity career in marketing communications that she loved. She was in pain and regularly cried in the hours between dropping off and picking up her two small children. And running was no longer possible; her doctors said she would need a wheelchair within five years.

That was 2005. Two decades later, the future Ms. Pevec once feared has never come to pass, and on Sunday, she did something she never could have imagined back in those dark, early days – she celebrated the 20th anniversary of her MS diagnosis by lacing up her white running shoes to race in the 2025 Toronto half-marathon.

It was her 16th half-marathon since she was told her running days were over. Ms. Pevec, now 56, has also since competed in 16 full marathons, four triathlons and seven three-kilometre open-water swims.

“In my wildest dreams I couldn’t have thought that I would be where I am today,” she says. “Given the nature of the disease, given the fact that it is progressive, you would not expect to be better than you were 20 years ago. But that’s the case for me.”

Ms. Pevec has the relapsing-remitting form of MS, characterized by symptom flare-ups followed by periods of remission. From the beginning, she was determined to attack her disease with the latest and most aggressive drugs she could get her hands on. As it happens, her journey has also mapped onto a remarkable 20-year period of explosive progress in the MS landscape, which has seen game-changing shifts in understanding and treating the disease.

MS is a chronic neurological disease where the immune system attacks the protective sheath covering nerve fibres, disrupting communication between the brain and the rest of the body. Canada has one of the highest MS rates worldwide, affecting an estimated 90,000 people, 75 per cent of whom are women. Symptoms and disease progression can be variable and unpredictable; some people only experience mild symptoms, while others eventually lose the ability to walk or speak.

There is still no cure for MS, and much work remains, especially for treating the progressive forms of the disease. But walkers and wheelchairs are no longer a given for MS patients, who now have more than 20 disease-modifying drugs available to them.

It’s a far cry from 2005, when Ms. Pevec only had four therapies to choose from. Dr. Jiwon Oh, director of BARLO Multiple Sclerosis Centre at St. Michael’s Hospital in Toronto, was still a neurology resident at the time and recalls the dark euphemism her classmates used for MS and other neurological diseases: “diagnose and adios.”

“I had a bunch of classmates say, why would you ever go into neurology? It’s such a depressing field because there’s no treatments,” she recalls. “But I don’t think some of my other classmates … have had this experience, which is to see a field completely change in front of your eyes.”

The first disease-modifying therapy for MS was approved in Canada in 1995. It belonged to a class of drugs known as immunomodulators, says Mark Freedman, a professor of neurology at the University of Ottawa and senior scientist with the Ottawa Hospital Research Institute. “They trick the immune system back to not attacking the brain,” he says.

Early trials of immunomodulators showed they reduced relapse rates by 18 per cent to 34 per cent. Ms. Pevec’s first drug, Avonex, was an immunomodulator that had to be injected into her thigh muscle and left her flattened for days with debilitating flu-like symptoms. She had to take it weekly. “It was just a vicious circle of pain and discomfort and then anticipation of doing it all over again,” she said.

Her second immunomodulator worked better. But for Ms. Pevec, the immunomodulators were just buying her time until she could get natalizumab, a next-generation MS drug she’d read about online.

When natalizumab first came to market, it offered “an apparent doubling of efficacy” for reducing relapses, according to a 2022 paper in The Lancet Neurology. Dr. Oh recalls that some even speculated it might be a cure.

But “initial euphoria regarding this breakthrough turned to despair,” the Lancet paper says. Just months after approval, it became clear that the drug, sold as Tysabri, also put some patients at risk of developing a fatal brain infection. Natalizumab returned in 2006 with a risk evaluation and mitigation strategy in place.

In Canada, Ms. Pevec was among the first patients in line for it. “I was very scared,” she says. “But I knew I had to try.”

To take Tysabri, which was covered by her public and private insurance, Ms. Pevec visited a clinic every month to receive her hour-long infusion. Five months in, she was walking her dog when she suddenly realized she was no longer tripping over her own feet. On an impulse, she broke out into a run; she didn’t stop for 12 minutes.

“I got home and it was as if I had won the Olympic gold,” she says with a laugh. “I called my husband. I was like, ‘I ran!’”

Tysabri ushered in a new life for Ms. Pevec. MS was no longer the first and last thing she thought about every day. She ramped up her volunteering and started working part-time jobs. She also resumed running, and in 2009, Ms. Pevec started racing in marathons again.

After 72 infusions of Tysabri, her risk of developing dangerous complications became too high, so Ms. Pevec had to stop. But now, her doctor had more than a dozen other therapies to offer, including pills that could be taken at home.

This was 2015, well into what Dr. Oh calls “the renaissance period of treatment of MS.” “Literally every year or two, we started getting new treatments available,” she says. A new class of “cell-depleting” therapies had also arrived and “proved to be game-changers,” according to the Lancet paper.

Ms. Pevec opted for one of the newer therapies. It carried a high risk of side effects and required two rounds of multiday infusions at the hospital, but showed high efficacy. In November, she switched to an even newer drug that can be self-injected monthly – her fifth MS therapy to date.

In the 20 years since Ms. Pevec’s diagnosis, researchers have made huge strides toward better understanding MS, and doctors no longer wait to start treatment, Dr. Oh says. “This completely changes long-term outcome,” she says. “Even a year of a delay in treatment can change how you’re doing five to 10 years down the road.”

Ms. Pevec knows that not every MS patient can, or would, choose her aggressive treatment approach. But she’s grateful for the therapeutic advances that have given her 20 years of full and active living – and running.

When Ms. Pevec finished her second marathon, just months before her MS diagnosis, she did so in fits and spurts, stumbling every few steps. On Sunday, running hand in hand with her daughter Breanna, she crossed the finish line of the 2025 Toronto half-marathon, wearing carbon-fibre leg braces and a wide smile on her face. She did not break her stride.