A single-patient study conducted by English researchers revealed that the antiviral drug remdesivir could be a highly effective treatment for COVID-19.

Published on Monday, Dec. 14, in the journal Nature Communications, the latest study raises questions about previous studies that found remdesivir had no impact on death rates from the disease.

The study describes how a patient with COVID-19 and X-linked agammaglobulinemia (XLA), a rare, inherited immunodeficiency disorder, showed significant improvement when treated with remdesivir.

Prior to being treated, the patient showed moderate but persistent symptoms of COVID-19 due to his inability to produce antibodies. Antibodies play a key role in defending against pathogens.

Though unusual, the presence of both COVID-19 and XLA in the patient gave the researchers rare insight into remdesivir’s antiviral properties and its effectiveness in the treatment of COVID-19.

Overall, the patient’s dramatic response to the drug indicates that it may be highly effective against COVID-19, even if only for some patients, said co-author Nicholas Matheson from the University of Cambridge School of Clinical Medicine in the U.K.

Remdesivir reduces virus levels, improves symptoms

There have been several studies supporting or questioning remdesivir’s effectiveness. However, some of those studies conducted during the first wave of the pandemic might not be ideal for assessing remdesivir’s antiviral properties, said Cambridge’s James Thaventhiran, who also worked on the case.

To address that, the researchers studied the case of a patient aged 31 years who became ill with COVID-19. He also had XLA, a disorder that affects the immune system’s ability to produce antibodies. Antibodies latch onto foreign invaders and substances, or antigens, in order to remove them from the body. Because the patient was unable to produce antibodies, his body couldn’t heal itself, hence the persistent symptoms.

Over a period of more than two months, the patient was first treated with two drugs that were also studied for their effects against COVID-19: hydroxychloroquine and azithromycin.

When those drugs proved ineffective, the patient was given two separate courses of treatment with remdesivir. During the first course of treatment, the patient’s virus levels fell and his symptoms greatly improved.

The patient was discharged but returned a week later after his virus levels rose and he started showing several symptoms again. The second course of treatment with remdesivir proved to be even more effective after he no longer tested positive for COVID-19.

During both courses of treatment with the drug, the patient’s virus levels declined, suggesting that remdesivir helped prevent SARS-CoV-2 from spreading. The researchers believe this also proves that XLA was inhibiting the patient’s immune system from fighting the virus.