CD200 and B-cell chronic lymphocytic leukemia: While the initial Phase I trial findings for samalizumab in CLL patients [51] certainly warrant further clinical investigation of different dosing regiments and its efficacy in additional blood cancers, shortcomings related to partial responses, lack of a durable response and the high incidence of mild to moderate toxicities raise concerns over the potential impact of CD200 antibody blockade therapy may hold for certain blood cancers other than CLL and solid malignancies.