PRTN3 and rheumatoid arthritis: Historically, there have been some ineffective BTK inhibitors as therapeutic agents for RA (eg, spebrutinib and poseltinib), with fenebrutinib being one of the few successful agents for RA treatment with this mechanism of action.32 Despite the current study failing to show significant changes in the ACR20 response rates, changes in IgG, IgM, RF and ACPA biomarkers were similar between TAS5315 and those previously reported with fenebrutinib.32 Although fenebrutinib binds to BTK in a different way to TAS5315, its mechanism of action is largely similar.