Pharmacodynamic Effects of Administration of Maytansine Conjugated Anti-CD22 Monoclonal Antibodies to Cynomolgus Monkeys

Abstract CD22 is a B cell-specific glycoprotein expressed on the cell surface of all mature B cells. A candidate therapeutic anti-CD22 antibody, 10F4v3, was conjugated to the anti-mitotic agent maytansine (10F4v3-DM1). DM1 disrupts cellular mitosis through inhibition of tubulin polymerization when internalized into cells. The anti-CD22 DM1 conjugate was shown to have significant potency in preclinical efficacy models of NHL. In order to further characterize this antibody-drug conjugate in preclinical studies, we first evaluated the binding characteristics of the 10F4v3 to peripheral blood B cells from various geographical sources of cynomolgus monkeys. 10F4v3 bound to peripheral blood B cells from all cynomolgus monkeys of Indonesian and Mauritian origins, but displayed only limited binding to cynomolgus monkeys of Chinese and Cambodian origins. Therefore, further pre-clinical evaluation of 10F4v3-DM1 was conducted in Indonesian cynomolgus monkeys to examine the safety, pharmacokinetic, and pharmacodynamic effects in monkeys dosed at 10, 20, and 30 mg/kg (2000, 4000, and 6000 mg/m2 DM1). Pharmacodynamic assessments of peripheral blood and lymphoid tissues included examination of B cells, B cell subsets, CD4+ T cells, CD8+ T cells, and CD3−CD20− (NK) cells. B cell subsets included CD20+, CD20+CD21+, CD20+CD21−, CD20+CD21+CD27+, CD20+CD21+CD27−, and CD20+CD21high lymphocytes which are phenotypically similar to human B cells, mature B cells, germinal center B cells, memory B cells, naïve B cells, and marginal zone B cells, respectively. B cells and B cell subsets were substantially depleted in peripheral blood at all doses, with no apparent dose-dependent effects. In lymphoid tissue, B cells were also depleted, with substantial depletion of CD20+CD21− and CD20+CD21high B cell subsets in spleen and bone marrow. Based on the nonclinical data, 10F4v3-DM1 exhibits an encouraging pharmacodynamic profile that supports clinical development for the potential treatment of non-Hodgkin’s lymphoma.