Steven P. Treon, MD, PhD, of Dana-Farber Cancer Institute, discusses Bruton’s tyrosine kinase (BTK), which is activated during severe COVID-19 infection. Patients with the coronavirus and chronic lymphocytic leukemia who remained on the BTK inhibitor ibrutinib had a mild disease course, with decreased C-reactive protein and improved oxygenation. Clinical trials to validate the role of BTK inhibitors in treating COVID-19–related pulmonary distress are now underway.