ABO2203: mRNA-Encoded T-Cell Engager Achieves 100% Complete Response in High-Dose B-NHL Cohort

Abogen Biosciences presented an oral presentation at AACR 2026 with Phase 1 first-in-human data for ABO2203, an mRNA-encoded CD3xCD19 bispecific T-cell engager (TCE) for relapsed/refractory B-cell non-Hodgkin lymphoma (B-NHL). Efficacy was dose-dependent: objective response rate was 33% in the low-dose cohort, 67% in the medium-dose cohort, and 100% complete response rate in the high-dose cohort. Unlike conventional protein-based T-cell engagers requiring IV infusion of a recombinant antibody, ABO2203 encodes the bispecific antibody construct as mRNA in a lipid nanoparticle, enabling sustained in vivo production of the therapeutic protein by the patient's own cells. This approach potentially overcomes the short half-life and complex pharmacokinetics of protein-based TCEs while leveraging established mRNA-LNP manufacturing. The data represent a significant expansion of mRNA technology beyond vaccines into complex antibody therapeutics.