9 December 2025

Hydroxychloroquine Does Not Improve biomarkers of Vascular Damage or Blood Clotting in Hospitalized COVID-19 Patients

At the start of the COVID-19 pandemic, hydroxychloroquine (HCQ)—a drug commonly prescribed for autoimmune diseases and in particular antiphospholip syndrome—was considered a potential treatment due to its anti-inflammatory but also its supposed blood vessel-protective effects. Because severe COVID-19 induces damage to the blood vessels and abnormal blood clotting, we explored whether HCQ might offer vascular protection in infected patients.

To evaluate this, we conducted a study within the DisCoVeRy trial, focusing on patients recruited during the first wave of the pandemic. We compared the biological effects in patients who received hydroxychloroquine plus standard hospital care with those who received standard care alone. Our investigation centered on three key biomarkers in the blood that reflect blood vessel damage and coagulopathy: angiopoietin-2, P-selectin, and D-dimer. These markers were measured repeatedly throughout hospitalization to assess whether HCQ influenced their progression.

The results showed that patients with more severe illness had higher levels of these biomarkers at baseline, indicating greater blood vessel injury. However, hydroxychloroquine had no effect on how these markers evolved over time. Unlike its documented benefits in autoimmune diseases, HCQ did not reduce endotheliopathy or clotting abnormalities in patients with COVID-19.

These findings reinforce the growing body of evidence that hydroxychloroquine is not effective in the treatment of COVID-19. More importantly, the study underscores the urgent need to focus on therapies that specifically target blood vessel health—a critical factor in the progression of severe COVID-19. In summary, hydroxychloroquine does not protect against vascular complications or improve outcomes related to blood clotting in hospitalized patients.

Link to the article published in Angiogenesis : https://link.springer.com/article/10.1007/s10456-025-10023-7