Repurposed Blood Clot Drug Shows Promise for Hospitalized COVID-19 Patients

The study analysed data from almost 500 patients hospitalised with COVID-19 across six countries. 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.

Heparin, a drug traditionally injected to treat blood clots, was tested in this study in an inhaled form, targeting the lungs directly. As well as acting as an anticoagulant, heparin has anti-inflammatory and pan-antiviral properties. Earlier research results showed breathing and oxygen levels improved in COVID-19 patients after they inhaled a course of heparin.

The researchers believe the drug could also be useful in fighting other serious respiratory infections such as pneumonia.

Professor Clive Page, Emeritus Professor of Pharmacology at King’s, who co-led the international study with ANU Professor van Haren, said: “Inhaled heparin is anti-viral, anti-inflammatory and anti-coagulant. There’s no other drug that has that unique combination. We know it’s only a matter of time until the next pandemic, and there are still COVID-19 patients who get very sick. This is a great weapon to have up our sleeve.”

While the findings highlight the potential of inhaled heparin, further development is required before the treatment can be routinely adopted. The researchers believe the drug could also be useful in fighting other serious respiratory infections, such as pneumonia, which can be caused by a range of viruses and bacteria.

According to Professor van Haren, the drug would also be helpful for those with a compromised immune system, such as cancer patients, when they experience a respiratory infection.

Professor Frank van Haren, lead author, ANU and Director of the Intensive Care Unit at the St George Hospital in Sydney, said: “It doesn’t matter what kind of respiratory infection the patient is dealing with, the drug – when inhaled - will stop it from infecting the patient and from damaging the lungs. 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"

The researchers are now also developing an improved formulation of heparin, specifically designed to be given by inhalation.

Reference: van Haren FMP, Valle SJ, Neto AS, et al. Efficacy of inhaled nebulised unfractionated heparin to prevent intubation or death in hospitalised patients with COVID-19: an investigator-initiated international meta-trial of randomised clinical studies. eClinicalMedicine. 2025. doi: 10.1016/j.eclinm.2025.103339

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