Population Pharmacokinetics and CD20 Binding Dynamics for Mosunetuzumab in Relapsed/Refractory B-Cell Non-Hodgkin Lymphoma (R/R NHL)

Introduction:Mosunetuzumab (Mosun) is a CD20xCD3 T-cell engaging bispecific antibody that redirects T cells to eliminate malignant B cells. Clinical data from GO29781 (NCT02500407), a Phase I/II, open-label, multicenter dose-escalation and expansion study of Mosun in pts with relapsed or refractory (R/R) non-Hodgkin lymphoma (NHL), was used to develop a population pharmacokinetic (popPK) model describing Mosun concentration-time data. Prior to initiation of Mosun, many patients had circulating levels of other anti-CD20 drugs (e.g. rituximab (R) or obinutuzumab (G)) from prior treatment. In order to elucidate exposure-response (ER) relationships in the presence of these competitors, CD20 binding and R/G pharmacokinetics were incorporated into the popPK model to calculate the Mosun CD20 receptor occupancy percentage (RO%) over time.