The efficacy and safety of acalabrutinib, a Bruton tyrosine kinase (BTK) inhibitor, was evaluated in 2 phase 2 studies in hospitalized patients with coronavirus disease 2019 (COVID-19) who received acalabrutinib + best supportive care (BSC) versus BSC alone (Clinicaltrials.gov: NCT04380688 and NCT04346199). The gene discussed is BTK; the disease is COVID-19.