The treatment from Southampton-based biotech Synairgen uses a protein called interferon beta which the body produces when it gets a viral infection.
The protein is inhaled directly into the lungs of patients with coronavirus, using a nebuliser, in the hope that it will stimulate an immune response.
The initial findings suggest the treatment cut the odds of a Covid-19 patient in hospital developing severe disease – such as requiring ventilation – by 79%.
Patients were two to three times more likely to recover to the point where everyday activities were not compromised by their illness, Synairgen claims.
It said the trial also indicated “very significant” reductions in breathlessness among patients who received the treatment.