TransCon IL-2 β/γ: a novel long-acting prodrug with sustained release of an IL-2Rβ/γ-selective IL-2 variant with improved pharmacokinetics and potent activation of cytotoxic immune cells for the treatment of cancer

Abstract

BackgroundRecombinant interleukin-2 (IL-2, aldesleukin) is an approved cancer immunotherapy but causes severe toxicities including cytokine storm and vascular leak syndrome (VLS). IL-2 promotes antitumor function of IL-2Rβ/γ+ natural killer (NK) cells and CD8+, CD4+ and gamma delta (γδ) T cells. However, IL-2 also potently activates immunosuppressive IL-2Rα+ regulatory T cells (Tregs) and IL-2Rα+ eosinophils and endothelial cells, which may promote VLS. Aldesleukin is rapidly cleared requiring frequent dosing, resulting in high Cmax likely potentiating toxicity. Thus, IL-2 cancer immunotherapy has two critical drawbacks: potent activation of undesired IL-2Rα+ cells and suboptimal pharmacokinetics with high Cmax and short half-life.MethodsTransCon IL-2 β/γ was designed to optimally address these drawbacks. To abolish IL-2Rα binding yet retain strong IL-2Rβ/γ activity, IL-2 β/γ was created by permanently attaching a small methoxy polyethylene glycol (mPEG) moiety in the IL-2Rα binding site. To improve pharmacokinetics, IL-2 β/γ was transiently attached to a 40 kDa mPEG carrier via a TransCon (transient conjugation) linker creating a prodrug, TransCon IL-2 β/γ, with sustained release of IL-2 β/γ. IL-2 β/γ was characterized in binding and primary cell assays while TransCon IL-2 β/γ was studied in tumor-bearing mice and cynomolgus monkeys.ResultsIL-2 β/γ demonstrated selective and potent human IL-2Rβ/γ binding and activation without IL-2Rα interactions. TransCon IL-2 β/γ showed slow-release pharmacokinetics with a low Cmax and a long (>30 hours) effective half-life for IL-2 β/γ in monkeys. In mouse tumor models, TransCon IL-2 β/γ promoted CD8+ T cell and NK cell activation and antitumor activity. In monkeys, TransCon IL-2 β/γ induced robust activation and expansion of CD8+ T cells, NK cells and γδ T cells, relative to CD4+ T cells, Tregs and eosinophils, with no evidence of cytokine storm or VLS. Similarly, IL-2 β/γ enhanced proliferation and cytotoxicity of primary human CD8+ T cells, NK cells and γδ T cells.SummaryTransCon IL-2 β/γ is a novel long-acting prodrug with sustained release of an IL-2Rβ/γ-selective IL-2. It has remarkable and durable pharmacodynamic effects in monkeys and potential for improved clinical efficacy and tolerability compared with aldesleukin. TransCon IL-2 β/γ is currently being evaluated in a Phase 1/2 clinical trial (NCT05081609).

A phase Ib study of interleukin-2 plus pembrolizumab for patients with advanced melanoma

“…New variants of IL-2 designed to preferentially target CD8+ effector cells are in clinical testing ( 12 , 13 ). Pegylation is another popular strategy to both extend the half-life of IL-2 and to avoid CD25 signaling.…”

IL-2-driven CD8+ T cell phenotypes: implications for immunotherapy

“…However, one of the biggest concerns in the design of IL-2-derived biologicals is avoidance of the concomitant stimulation of Tregs. This has motivated the design of IL-2 variants that do not act on Tregs [ 48 – 51 ], but suffer from low efficacy on CD8 + T cells [ 8 , 11 ]. Based on recent data, we propose that Tregs might not be able to suppress CD8 + T cell responses in the presence of strong exogenous IL-2R agonists and, thus, might not substantially mitigate the effects of IL-2-based therapy.…”

“…The second generation of IL-2-based antitumor therapies featured drugs with modified binding to IL-2R aiming to stimulate cytotoxic CD8 + T cells and NK cells, but not endothelial cells or Tregs in mouse models and, subsequently, in clinical trials (NCT05267626 i , NCT02983045 ii , and NCT04855929 iii ) [ 18 – 20 , 48 – 51 , 58 – 69 ]. The respective strategies included modifications of the IL-2Rα binding site [ 48 – 51 , 58 , 59 ], selecting IL-2 variants with increased affinity to IL-2Rβ [ 18 , 60 ], complexes and fusion of IL-2 with anti-IL-2-antibodies [ 61 – 64 ] or IL-2Rα [ 65 , 66 ], or by designing novel IL-2-like drugs [ 67 , 68 ]. These innovative strategies resolved the adverse effects, but have not yet shown promising results in clinical trials [ 16 ], potentially due to their limited antitumor efficacy.…”

“…(B) Multiple IL-2 variants (IL-2v) were designed with a mutated IL-2Rα-binding site. These variants can bind only to IL-2Rβγ receptors, regardless of the availability of IL-2Rα [ 48 – 51 , 59 ]. (C,D) The apparent affinity of binding of IL-2 variants (IL2v) to IL-2Rβγ is increased in cis by fusion to (C) monovalent [ 7 ] or (D) bivalent [ 8 , 11 ] anti-PD-1 antibodies, regardless of the availability of IL-2Rα.…”

A Review of Protein- and Peptide-Based Chemical Conjugates: Past, Present, and Future

“…SAR444245 uses a permanently conjugated PEG chain to simultaneously improve half-life and disrupt rhIL2 binding to IL2Rα, which suppresses T reg activation while stimulating CD8+ T-cells and NK cells in the tumor microenvironment [ 284 ]. Likewise, TransCon IL-2 β/γ consists of a short, permanent PEG chain to eliminate IL2Rα binding coupled with a transiently conjugated 40 kDa PEG for half-life extension [ 285 ]. A second class of IL2-based therapeutics biases the cytokine towards IL2Rα binding; NKTR-358 uses permanent PEG conjugation to selectively induce T reg proliferation without expanding CD8+ and CD4+ T-cells and is undergoing multiple Phase 1 trials for treatment of autoimmune disorders [ 286 ].…”