Tumor-targeted 4-1BB agonists for combination with T cell bispecific antibodies as off-the-shelf therapy

Area of Science:

• Immunology
• Oncology
• Biotechnology

Background:

• Endogenous costimulatory molecules like 4-1BB (CD137) are crucial for T cell activation in cancer immunotherapy.
• Systemic administration of agonistic anti-4-1BB antibodies faces challenges including Fcγ receptor dependency and hepatotoxicity, hindering clinical advancement.
• Novel strategies are needed to safely and effectively harness 4-1BB costimulation for cancer treatment.

Purpose of the Study:

• To engineer novel bispecific proteins (FAP-4-1BBL and CD19-4-1BBL) that target 4-1BB and tumor-associated antigens or stroma.
• To evaluate the efficacy and safety of these engineered proteins in preclinical cancer models.
• To assess the potential of these agents as off-the-shelf combination immunotherapies.

Main Methods:

• Protein engineering of dual-targeting molecules (FAP-4-1BBL, CD19-4-1BBL) for simultaneous binding to 4-1BB and tumor targets.
• In vitro assessment of T cell costimulation dependent on tumor antigen-mediated clustering.
• In vivo studies in colorectal cancer models (rhesus monkey) and combination therapy models (mouse) using engineered proteins and T cell bispecific (TCB) molecules.
• Analysis of cytokine secretion (IFN-γ, granzyme B) and immune cell populations (CD8+ T cells).

Main Results:

• Engineered FAP-4-1BBL and CD19-4-1BBL proteins provide potent T cell costimulation strictly dependent on tumor antigen-mediated clustering, avoiding systemic FcγR activation.
• FAP-4-1BBL demonstrated successful targeting to tumor stroma and lymph nodes in a colorectal cancer model.
• Combination therapy with FAP- or CD19-4-1BBL and TCB molecules induced tumor remission in mouse models, associated with increased effector CD8+ T cell activity.
• Enhanced IFN-γ and granzyme B secretion observed when combining FAP-4-1BBL with TCB molecules in human tumor samples.

Conclusions:

• Engineered 4-1BBL fusion proteins offer a promising strategy to overcome the limitations of traditional anti-4-1BB antibodies.
• These novel agents enable potent, tumor-targeted T cell costimulation, leading to effective anti-tumor immunity.
• FAP-4-1BBL and CD19-4-1BBL represent viable off-the-shelf combination immunotherapies for solid and hematological malignancies without requiring genetic modification of effector cells.