A phase III randomized clinical trial found that fostamatinib may not improve outcomes in adult patients hospitalized with COVID-19 infections and hypoxemia, according to new research.

In the multicenter study, published in JAMA Network Open, researchers recruited 400 patients between November 2021 and September 2023 across 62 hospitals in 6 countries. The study population was 72.3% vaccinated against COVID-19 infections.

The researchers found no statistically significant difference in oxygen-free days between the patients receiving fostamatinib (mean = 13.4 days) vs those receiving placebo (mean = 14.2 days).

The 28-day mortality rate was 11.3% in the fostamatinib group compared with 8.1% in the placebo group. The proportion of patients alive and free of respiratory failure at day 28 was 85.5% with fostamatinib vs 88.9% with placebo.

Safety data showed elevated aspartate aminotransferase occurred in 11.6% of the patients who received fostamatinib compared with 5.5% in those who received placebo. Other safety outcomes remained similar between the groups.

The study included an older population with multiple chronic conditions—25.8% received high-flow oxygen therapy or mechanical ventilation at enrollment. Most of the participants (94%) were infected during the Omicron period.

The researchers documented factors distinguishing this trial from earlier studies, including its larger sample size, higher vaccination rates, different viral variants, more comorbidities in the study population, and increased antiviral use.

The oral medication was tested as a potential treatment targeting COVID-19–related inflammation through inhibition of neutrophils, macrophages, and platelets.

Conflict of interest disclosures can be found in the study.