The present invention concerns antigen binding proteins and fragments thereof which specifically bind B Cell Maturation Antigen (BCMA), particularly human BCMA (hBCMA) and which inhibit the binding of BAFF and APRIL to the BCMA receptor. Further disclosed are pharmaceutical compositions, screening and medical treatment methods.本發明係關於抗原結合蛋白及其片段,其特異性結合B細胞成熟抗原(BCMA)(特定而言人類BCMA(hBCMA))且抑制BAFF及APRIL與BCMA受體之結合。本發明進一步揭示醫藥組合物、篩選及醫學治療方法。