Therefore, we investigated the PK, biodistribution, and in vivo internalization of a fully murine Fc-inert bsAb targeting murine CD3ε and murine tyrosinase-related protein 1 (TRP1, also gp75 or TYRP-1) (CD3xTRP1 bsAb) that has been extensively evaluated for its immunological effects.10 11 TRP1 is translationally of interest as it is similarly expressed in mice and humans, with endogenous expression on melanocytes and upregulated expression in melanomas. Here, TYRP1 is linked to melanoma.