Single dose of XmAb5592 depletes blood and bone marrow plasma cells in cynomolgus monkeys. XmAb5592 was injected as a single intravenous dose at 20 mg/kg into cynomolgus monkeys (2 males, 2 females). Blood samples were collected predose and at indicated days after administration. Bone marrow aspirates were also collected predose and at 7, 14 and 28 days after XmAb5592 administration. Plasma cells (CD38^highCD19^low/−CD20⁻) were analyzed by flow cytometry and their numbers expressed as a percentage of total lymphocytes. XmAb5592 rapidly depleted blood plasma cells (A) an average of ∼ 80% after 1 day of injection which recovered to the initial level by day 14. In bone marrow (B), the plasma cells were reduced an average of ∼ 60% at day 7 after injection; however the levels did not recover completely by the study end on day 28.