Early data from a clinical study suggest that blocking the Bruton tyrosine kinase (BTK) protein provided clinical benefit to a small group of patients with severe COVID-19. Researchers observed that the off-label use of the cancer drug acalabrutinib, a BTK inhibitor that is approved to treat several blood cancers, was associated with reduced respiratory distress and a reduction in the overactive immune response in most of the treated patients.

The results of this study were used to inform the trial design of the CALAVI (acalabrutinib) randomized, controlled clinical trial, sponsored by AstraZeneca, which will examine the safety and efficacy of acalabrutinib in patients with severe COVID-19.