SYK and COVID-19: The SYK inhibitor R406 (the active form of FDA- and EMA-approved drug fostamatinib) has been recently identified as an effective immunoregulatory drug modulating the activities of immune cells and platelets in severe COVID-19 (33, 37, 39, 40) and has been applied in several clinical trials (NCT04581954, NCT04629703, NCT04924660) (41).