Surprisingly, other cytokines elevated in COVID-19 patients such as C-X-C motif chemokine ligand 10, IL-6, MIP-1α, and TNF-α, which are downregulated in patients with certain B-cell malignancies and graft-versus-host disease treated with BTK inhibitors, showed no differences between zanubrutinib- and placebo-treated patients in cytokine studies (13–16). Here, IL6 is linked to graft versus host disease.