uPAR ‐Targeting T Cell Engager Exerts Senolytic Effects in Mice and Non‐Human Primates With Serum Aminotransferase Activity as a Safety Monitor

Senolytic CAR-T cells targeting uPAR induce dose-dependent toxicities. Although dosage adjustment mitigates these toxicities in laboratory mice, clinical translation remains challenging owing to the unpredictability of CAR-T cell proliferation across heterogeneous patient populations. In contrast, bispecific T-cell engagers (BiTEs) offer a safer alternative with superior dose-titratability. Here, we have developed a GFD-CD3 BiTE by employing the growth factor-like domain (GFD) of the natural ligand uPA as the targeting moiety to target uPAR-positive senescent cells. Dose-range finding studies revealed that high-dose GFD-CD3 predominantly induced hepatotoxicity through T cell-mediated attack on hepatic endothelial cells. Crucially, under transaminase-guided monitoring, low-dose GFD-CD3 effectively eliminated senescent cells and alleviated age-related pathologies in aged mice and non-human primates without adverse effects. These findings establish GFD-CD3 as a clinically translatable senolytic agent and provide the compelling preclinical evidence for BiTE as a senolytic strategy.