IL11 and Thrombocytopenia: Following its identification in 1990,1 recombinant human IL11 (rhIL11) was found to increase megakaryocyte activity and peripheral platelet counts in mice.2 Soon after, IL11 was developed as a therapeutic (Oprelvekin; Neumega) to increase platelet counts in patients with chemotherapy-induced thrombocytopenia, received FDA approval for this indication in 1998, and is still used to this day.3,4 In recent years, longer-acting formulations of rhIL11 have been tested in pre-clinical studies and new clinical trials of PEGylated rhIL11 in patients are anticipated.5