Abstract

The clinical phase 1 study (NCT03773393) of the T regulatory (Treg) cell product CK0801 in nine patients with bone marrow failure syndromes reported by Kadia et al.1 in this issue of NEJM Evidence fits well into the current immunotherapy era. These cells, brought to the forefront by Shimon Sakaguchi two decades ago, constitute a subpopulation of CD4+ T cells characterized by the surface expression of the alpha chain of the interleukin-2 receptor, CD25, the inhibitory molecule CTLA-4, and the intracellular transcription factor FoxP3.2 They control, under healthy conditions and through several mechanisms, expansion and function of other immune cells, such as effector T cells and natural killer cells.