Protein kinase inhibitors represent a novel and promising approach to the 
treatment of rheumatoid arthritis (RA). By targeting intracellular signaling 
pathways of cytokine-mediated reactions, these substances are able to interfere 
with critical immune processes that underly the pathology of RA. With 
tofacitinib, the first Janus kinase (JAK) inhibitor has been approved in the 
USA, as well as in Switzerland and other countries. Several other substances are 
currently undergoing phase II or phase III trials.A crucial question that will 
shape the future of these new drugs is whether they are safe and in particular, 
whether they are safer than biological therapies. This article provides an 
overview on current data concerning the efficacy and safety of the most 
promising substances and discusses the potential future role of intracellular 
kinase inhibitors.