CD24 and COVID-19: In a recent study that was successfully completed (phase 1 trial), it was found that exosomes isolated and purified from T-RExTM-293 cells engineered to express CD24 at high levels (EXO-CD24) inhaled once a day for a few minutes for five days selectively restrained certain cytokine and led to recovery in 35 patients with COVID-19 whose conditions were moderate or worse (ClinicalTrials.gov Identifier: NCT04747574).