New leukemia and lymphoma treatment shuts off allergic reaction to airborne allergens and may offer hope for people with severe food allergies.

In medicine, doctors sometimes find unexpected applications for certain drugs.

Case in point: Ibrutinib, a drug that was recently approved by the FDA for people with leukemia and lymphoma, is effective at stopping reactions to common airborne allergens.

A team from Northwestern University headed by Dr. Bruce Bochner, the Samuel M. Feinberg Professor of Medicine at Northwestern University Feinberg School of Medicine, published its findings in last month’s Journal of Allergy and Clinical Immunology.

The findings have implications for people with food allergies and airborne allergies, but there is still a long way to go, according to Bochner.

Read more: How to fight this year’s strong allergy season »

To understand the connection between its application as a cancer drug and its allergy-fighting properties, it’s important to know how ibrutinib works.

According to Bochner, the drug binds to Bruton’s tyrosine kinase (BTK), an enzyme inside immune cells that is critical to both the growth of specific cancers and the body’s immune response to inhaled allergens.

“By blocking BTK, this slows the growth of B lymphocyte cancers, for which it is now prescribed. Compared with traditional chemotherapies, its toxicities are relatively mild,” wrote Bochner in an email to Healthline.

The connection of a cancer drug to allergies might seem unorthodox, but experts suspected the connection before they were able to prove it.

Bochner said that scientists at Pharmacyclics, the company that makes ibrutinib, along with colleagues at the Johns Hopkins Asthma and Allergy Center, reported that the drug was effective at preventing allergic reactions in test tube blood cells.

“Ibrutinib is considered a game changer in these two types of cancers,” said Dr. Leo Gordon, the Abby and John Friend Professor of Cancer Research at Feinberg, in a press release. “We understood that it might have some biologic effects in what Bruce is interested in, so we were happy to participate in his study. It’s an interesting repurposing of that drug.”

“This gave us the idea that perhaps cancer patients being prescribed ibrutinib for their B cell cancer might lose their allergic responses,” he wrote. “So we recruited newly-diagnosed cancer subjects and did allergy testing just before starting the ibrutinib and then during treatment, and indeed found that their skin test responses to allergens after just one week of treatment [were negative], and stayed away for at least one to two months with continued treatment.”

Read more: What it’s like to survive a severe food allergy attack »

While Bochner and his team established that ibrutinib has potential applications not just for people with cancer, but also those with airborne allergies, food allergies are a bit more complicated.

For starters, airborne allergies have traditionally been easier to treat, with a range of options including antihistamines and allergy shots.

People with food allergies, on the other hand, have very few options. Most are prescribed an epinephrine injector, which in the case of a suspected allergic reaction, provides a brief window in time to get to an emergency department for further evaluation and treatment. There is also promising work being done on helping food-allergic people build tolerance by gradually ingesting the problematic food, but this work is ongoing.

Factoring in that food allergies can be deadly, and affect 1 in 13 children and 1 in 25 adults in the United States, finding ways to lessen the risk is a top priority for allergists.

“Preventing or lessening the severity of an allergic reaction to a food you’ve ingested that you’re allergic to is kind of the Holy Grail of food allergy treatment,” noted Bochner in a press release. “I don’t know if this or similar drugs will ever make it possible for a peanut-allergic person to eat peanut butter and jelly sandwiches, but we’re excited to use this approach to teach us how to lessen the risks of food allergy reactions.”

To that end, Bochner’s team is expanding their study to include adults with food allergies. If the team sees success, the next step could be getting funding to explore if BTK inhibitors will allow food-allergic people to eat problematic foods.

Understanding the connection between BTK and allergies is crucial when it comes to potential applications of drugs that are currently under development.

“Since ibrutinib does have side effects, not to mention high cost, when taken chronically, it would be very difficult to justify its long-term use for anti-allergy purposes alone,” wrote Bochner.

“However, besides ibrutinib, there are other next-generation BTK inhibitors being developed, and perhaps some will have an even better safety profile. For now, we are using BTK inhibitors as a proof-of-concept to see if they can really stop food allergic reactions.”