A Cheap Asthma Pill May Have Cracked Cancer’s ‘Invisibility Cloak’, Say Scientists

For years, cancer researchers chased billion-dollar “miracle drugs” inside ultra-modern laboratories. Now, scientists in Chicago believe part of the answer may have been sitting quietly inside ordinary medicine cabinets all along.

A common asthma medicine used for decades to control allergies and breathing problems may also help the immune system fight some of the world’s most aggressive cancers, according to a major new study published on Tuesday in Nature Cancer.

Researchers from Northwestern University's Feinberg School of Medicine discovered that tumours appear to exploit a molecular pathway known as CysLTR1 — a switch already well known to asthma specialists. Drugs such as Singulair, commonly prescribed for asthma and allergies, block that switch. In mouse experiments and studies involving human immune cells and tumour samples, blocking the pathway slowed tumour growth and helped restore the body’s natural anti-cancer defences.

The findings are drawing global attention not only because of the science but also because the medicine involved — montelukast — is already FDA-approved and widely available at relatively low cost.

That could dramatically shorten the long and painfully expensive road normally required to develop new cancer medicines.

Inside laboratories at Northwestern, researchers spent months analysing tumour samples, immune-cell behaviour and large patient cancer databases. What they found was unsettling. Certain tumours were effectively “re-training” neutrophils — a type of white blood cell that normally fights infection — to help cancers survive. Instead of attacking the tumour, the immune cells became protectors of the disease.

The CysLTR1 molecule appeared to function like a hidden control switch in that process.

“When we turned off this switch, either genetically or with existing drugs, we not only slowed tumour growth but also helped the immune system recover its ability to fight the cancer,” said Dr Bin Zhang, senior author of the study and professor of cancer immunology at Northwestern.

The team tested the approach across several difficult cancers, including melanoma, ovarian cancer, colon cancer, prostate cancer, and triple-negative breast cancer— one of the deadliest forms of breast cancer because it often stops responding to treatment.

In several mouse models, tumours that had already become resistant to immunotherapy started responding again after the pathway was blocked.

“Importantly, instead of simply removing these harmful white blood cells, we were able to reprogramme them into cells that support immune attack,” Zhang explained in the paper.

That distinction matters. Scientists say modern cancer treatment is increasingly shifting away from simply destroying cells toward re-educating the immune system itself.

The discovery also reflects a much larger global trend now reshaping medicine: drug repurposing. Instead of spending 15 years building entirely new medicines from scratch, researchers are increasingly testing older drugs for entirely different diseases. The strategy accelerated sharply during the COVID-19 pandemic and has since expanded to include cancer, neurology, infectious diseases, and metabolic disorders.

Industry analysts estimate the global repurposed-drug market could grow into a multi-billion-dollar sector by the early 2030s as governments and healthcare systems search for faster and cheaper treatments. In countries like India, where affordability remains a major public-health concern, recycled medicines could become especially important because generic manufacturing infrastructure is already strong.

The economics are difficult to ignore. It takes years of testing and billions of dollars to develop new cancer drugs, and they might not even work.

Still, cancer specialists caution that early excitement must be balanced with scientific discipline. Mouse studies do not always translate into success in humans. Large-scale clinical trials will still be necessary before montelukast can become part of standard cancer care.

But researchers believe the pathway to patient testing may now move unusually fast.

“We may be able to quickly and safely test it in cancer patients to improve immunotherapy,” Zhang said. “Especially in aggressive cancers, like triple-negative breast cancer, where new options are urgently needed,” he added.

For decades, medicine searched for futuristic “super-drugs” to defeat cancer. This latest discovery suggests something far simpler—and perhaps far more practical—may also play a role: giving old medicines a second life in humanity’s fight against one of its deadliest diseases.

The writer is a Delhi-based freelancer who writes on health issues and medical discoveries.