Master's Student Johns Hopkins Univ., United States
Introduction/Rationale: Interleukin-2 (IL-2) harbors great immunomodulatory potential for cancer treatment but its clinical use is predominantly hindered by: (i) concurrent activation of both effector and regulatory immune cells; (ii) toxicity at high doses; and (iii) short serum half-life. A promising approach to enhance IL-2 selectivity, safety, and circulation half-life was found in complexing IL-2 with anti–IL-2 antibodies, leading to the bias of cytokine activity toward specific immune subsets. However, clinical translation of such cytokine/antibody complexes is complicated by challenges as drug formulation or stability.
Methods: Here we designed a novel single-chain fusion protein denoted immunocytokines (IC) in which human IL-2 is covalently linked to the N-terminus of the heavy chain of the anti–IL-2 antibody F10, which was previously engineered by our lab to preferentially stimulate immune effector cells (i.e., effector T cells and natural killer cells) over regulatory T cells (Tregs). ICs transiently expressed in mammalian cells and purified with Protein G. Signaling activity was assessed in human peripheral blood mononuclear cells (PBMCs) and binding was evaluated via biolayer interferometry. In vivo activity is being interrogated by treating C57BL/6 mice with selected ICs and analyzing immune subset expansion via flow cytometry.
Results: PBMC studies showed that the F10 IC with IL-2 fused to the heavy chain selectively stimulates immune effector populations (CD8+ and CD4+ effector T cells) over Tregs. Interestingly, compared to F10 IC with IL-2 fused to the light chain, our novel F10 IC more potently stimulates both immune effector populations and Tregs.In vivo studies are ongoing.
Conclusion: This study pioneers the design and development of a novel IC that enhances IL-2 efficacy and selectively expands immune effector cell populations, which are critical for tumor suppression.This work presents a roadmap for engineering and translating cytokine/antibody fusion proteins as a novel class of anti-cancer drugs.
