摘要：SummaryCostimulation of tumor-infiltrating T lymphocytes by anti-4-1BB monoclonal antibodies (mAbs) has shown anti-tumor activity in human trials, but can be associated with significant off-tumor toxicities involving FcγR interactions. Here, we introduce albumin-fused mouse and human bispecific antibodies with clinically favorable pharmacokinetics designed to confine 4-1BB costimulation to the tumor microenvironment. These Fc-free 4-1BB agonists consist of an EGFR-specific VHHantibody, a 4-1BB-specific scFv, and a human albumin sequence engineered for high FcRn binding connected in tandem (LiTCo-Albu). We demonstratein vitrocognate target engagement, EGFR-specific costimulatory activity, and FcRn-driven cellular recycling similar to non-fused FcRn high-binding albumin. The mouse LiTCo-Albu exhibited a prolonged circulatory half-life andin vivotumor inhibition, with no indication of 4-1BB mAb-associated toxicity. Furthermore, we show a greater therapeutic effect when used in combination with PD-1-blocking mAbs. These findings demonstrate the feasibility of tumor-specific LiTCo-Albu antibodies for safe and effective costimulatory strategies in cancer immunotherapy.Graphical abstractDisplay OmittedHighlights•Tumor targeted 4-1BB agonist antibody-albumin fusions with high affinity to FcRn•Potent EGFR-specific 4-1BB costimulation and FcRn-driven cellular recycling•Prolonged circulatory half-life andin vivotumor inhibition, without toxicity•Combination with an anti-PD-1 blocking antibody further enhanced anti-tumor activityImmunology; Immunological methods; Immune response; Cancer.
