A method for clinical purging of myeloma bone marrow using peanut agglutinin as an anti-plasma cell agent, in combination with CD19 monoclonal antibody.

Previous studies have shown that the lectin peanut agglutinin (PNA) binds bone marrow plasma cells in the majority of patients with myeloma and does not bind to normal haemopoietic progenitors. This lectin has been used in combination with anti-CD19 monoclonal antibody (moAb) in a system for purging myeloma bone marrow. This has now been scaled up for application to ex vivo treatment of large volumes of bone marrow suitable for autologous bone marrow transplantation. Four bone marrow harvests from patients with myeloma containing 9.5 +/- 4.9% plasma cells were depleted of erythrocytes and mature granulocytes by Ficoll separation using the Haemonetics V50 cell separator. The mononuclear fraction was then purged with magnetic beads coated with PNA and anti-CD19 moAb. The system proved highly efficient with removal of all detectable plasma cells and CD19+ cells. Average mononuclear cell recovery following purging was 71% of the concentrated marrow with 78% yield of CFU-GM. Normal progenitor recovery related to patients' weight is predicted to be adequate for haemopoietic reconstitution following ablative chemoradiotherapy. This system is therefore feasible for large-scale clinical purging.