Myeloproliferative neoplasms (MPNs) can only be cured, to date, using allogeneic stem cell transplantation which, in turn, only works for up to 20% of patients. As calreticulin (CALR) frameshift mutations are the second most common cause of MPNs, targeting this endoplasmic reticulum resident protein is one of the strategies emerging at the forefront of hematological malignancies research.