Inhaled form of blood thinner treats serious COVID infections

A widely available and affordable drug has proven effective in treating seriously ill COVID-19 patients, according to an international study led by The Australian National University (ANU) in collaboration with King’s College London. The team’s results have been published in the journal eClinicalMedicine and were presented at the ERS Congress 2025, held in Amsterdam last month.

Heparin has traditionally been injected and used to treat blood clots, but the new study tested it in an inhaled form, targeting the lungs directly. As noted by study co-leader Professor Clive Page, from King’s College in London, “Inhaled heparin is antiviral, anti-inflammatory and anticoagulant — there’s no other drug that has that unique combination.”

As explained by study co-leader Professor Frank van Haren, from ANU, the study analysed data from almost 500 patients hospitalised with COVID-19 across six countries in the early stages of the pandemic. Patients who inhaled heparin were half as likely to require ventilation and had a significantly lower risk of dying compared with those receiving standard care.

“It follows our initial results which found breathing and oxygen levels improved in COVID-19 patients after they inhaled a course of heparin,” Van Haren added.

Heparin is a pathogen-agnostic drug, meaning it could help treat patients with a whole range of respiratory infections, regardless of which viruses or bacteria are causing them. The drug would also be helpful for those with a compromised immune system, such as cancer patients, who develop a respiratory infection.

“It doesn’t matter what kind of respiratory infection the patient is dealing with — when inhaled, the drug will stop it from infecting the patient and damaging the lungs,” Van Haren said.

“We’re aiming to conduct another trial in Europe to confirm its effectiveness in fighting other common respiratory infections such as influenza and RSV.

“And because it’s inexpensive, it’s much more accessible for those from low-income countries.”

While the findings highlight the potential of inhaled heparin, further development is required before the treatment can be routinely adopted. The team is now working on an improved formulation of heparin specifically designed to be given by inhalation.

“We know it’s only a matter of time until the next pandemic, and there are still COVID-19 patients who get very sick,” Page noted. “This is a great weapon to have up our sleeve.”

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