IL7R and myeloid sarcoma: GSK2618966, a humanized Fc-disabled immunoglobulin G1 (IgG1) blocking Ab to the interleukin-7 receptor (IL-7R) was developed to block IL-7 signaling in T cells for the treatment of numerous autoimmune diseases (RA, type I diabetes, MS, SLE and primary Sjogren syndrome), but was discontinued during Phase I clinical studies due to its high immunogenicity (92% of subjects) and the high incidence of neutralizing Abs (42).