Abstract 4507: TransConTM IL-2 β/γ: a novel long-acting prodrug of receptor-biased IL-2 designed for improved pharmocokinetics and optimal activation of T cells for the treatment of cancer
Authors: Rosen David Brian , Laufer Burkhardt , Knappe Thomas , Schnabel Meike , Begaliew Diana , Zettler Joachim , Krusch Mathias , Bernhard Ana , Heinig Stefan , Konjik Valentino , Wegge Thomas , Breinholt Vibeke , Tabrizi Mohammad , Sprogoe Kennett , Punnonen Juha 
Published: September 2020

Abstract
Background: Recombinant Interleukin-2 (IL-2, aldesleukin) is an approved immunotherapy for metastatic melanoma and renal cell carcinoma. However, treatment with IL-2 can induce severe side effects, such as vascular leak syndrome (VLS) and eosinophilic infiltration of cardiac and pulmonary tissues. IL-2 promotes the survival, proliferation and anti-tumor functions of CD8+ cytotoxic T cells, CD4+ effector T cells and natural killer cells, which mostly express the dimeric IL-2Rβγ receptor with low IL-2Rα levels. However, IL-2 also potently activates IL-2Rα+ immunosuppressive regulatory T cells as well as IL-2Rα+ eosinophils, type 2 innate lymphoid cells and endothelial cells, which may promote VLS. Aldesleukin is rapidly cleared with elimination T1/2 of 85 minutes requiring thrice daily dosing and resulting in large fluctuations in serum exposure, likely contributing to its toxicity. Thus, IL-2 has two critical drawbacks for cancer immunotherapy: 1) potent activation of undesired cells types expressing IL-2Rα and 2) high Cmax with rapid clearance.
Methods: We developed TransCon (transient conjugation) IL-2 β/γ, a novel sustained release prodrug of a receptor-biased IL-2 (IL-2 β/γ) to optimally address each of these drawbacks. First, to block IL-2Rα binding yet retain IL-2Rβγ activity, we created IL2 β/γ by permanently attaching a small PEG moiety to an engineered cysteine placed at the IL-2Rα binding site. Second, to improve PK properties, we attached the receptor-biased IL-2 β/γ to a TransCon PEG carrier via a TransCon linker, shielding bioactivity and creating a prodrug. Under physiological conditions, TransCon IL-2 β/γ was designed for sustained release of the bioactive IL-2 β/γ from the PEG carrier, aiming for a much lower Cmax and longer effective half-life of released IL-2 β/γ compared to aldesleukin.
Results: In binding and cell-based functional assays, free IL-2 β/γ demonstrated desirable IL-2 receptor selectivity maintaining IL-2Rβγ potency while losing IL2Rα potency. In vitro, TransCon IL-2 β/γ showed expected slow-release kinetics, supporting a half-life in humans of 2-3 days. In mouse tumor models, TransCon IL2 β/γ promoted CD8 and NK cell proliferation and activation. In cynomolgus monkeys, a single dose of TransCon IL-2 β/γ was well tolerated and induced a more robust CD8+ T cell and NK cell expansion relative to CD4+ T cells or eosinophils as compared to daily aldesleukin treatment. Consistent with these observations, TransCon IL-2 β/γ induced lower levels of systemic inflammatory cytokines and endothelial activity biomarkers when compared to aldesleukin.
Summary: The data presented here provide evidence that TransCon IL-2 β/γ may promote anti-tumor immune effector function with improved tolerability. TransCon IL-2 β/γ was designed as a novel long-acting, receptor-biased IL-2 prodrug that has the potential to overcome the challenges of existing IL-2 treatments.
Citation Format: David Brian Rosen, Burkhardt Laufer, Thomas Knappe, Meike Schnabel, Diana Begaliew, Joachim Zettler, Mathias Krusch, Ana Bernhard, Stefan Heinig, Valentino Konjik, Thomas Wegge, Vibeke Breinholt, Mohammad Tabrizi, Kennett Sprogoe, Juha Punnonen. TransConTM IL-2 β/γ: a novel long-acting prodrug of receptor-biased IL-2 designed for improved pharmocokinetics and optimal activation of T cells for the treatment of cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4507.