Cellular therapies: what is still missing?

Yeagy and colleagues present long-term data from a preclinical model of cystinosis after hematopoietic stem cell transplantation. The results suggest a therapeutic benefit independent of target tissue differentiation but dependent on the level of bone marrow chimerism. The mode of action remains mysterious, but positive effects are seen. Although the work presents a potential therapeutic option for an otherwise dismal disease, the search for the mechanism of action in cellular therapies continues.