The National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health (NIH), along with Inova Health System, has sponsored the trial.
Fostamatinib, which is sold in the US as Tavalisse (fostamatinib disodium hexahydrate) tablets, is an oral spleen tyrosine kinase (SYK) inhibitor.
Rigel is conducting the study at the NIH Clinical Center in Bethesda of Maryland and Inova Fairfax Hospital.
The randomised, double-blind and placebo-controlled study will assess the safety of fostamatinib to treat hospitalised Covid-19 patients.
Rigel Pharmaceuticals will randomly assign fostamatinib or matched placebo (1:1) to around 60 evaluable patients who are a 5 to 7 on the 8-point ordinal scale. It will administer treatment orally twice daily for 14 days.
According to the company, the trial’s primary objective is to assess the safety of fostamatinib compared to placebo for the treatment of hospitalised Covid-19 patients.
The secondary objective is the assessment of the early efficacy and clinically relevant measures of disease progression.
NHLBI clinical director Dr Richard Childs said: “As mortality continues to rise, it is evident that new therapeutics selectively targeting immune response are desperately needed to treat patients infected with SARS-CoV-2.
“This is a rigorously-designed clinical trial, which should provide insight into the potential safety and efficacy of fostamatinib in the treatment of severely ill patients suffering from Covid-19.”
The company is also evaluating fostamatinib in a phase 3 trial to treat warm autoimmune hemolytic anaemia (AIHA), as well as in a phase 2 trial to treat Covid-19 pneumonia being carried out by Imperial College London.
Rigel Pharmaceuticals secured approval for Tavalisse in the US and Europe as a treatment for adult chronic immune thrombocytopenia (ITP).
Earlier this month, GlaxoSmithKline (GSK) and Vir Biotechnology have announced that they will expand the study of a VIR-7831 (GSK4182136) monoclonal antibody to treat Covid-19.