ALKS 4230: a novel engineered IL-2 fusion protein with an improved cellular selectivity profile for cancer immunotherapy

Abstract

BackgroundInterleukin-2 (IL-2) plays a pivotal role in immune homeostasis due to its ability to stimulate numerous lymphocyte subsets including natural killer (NK) cells, effector CD4+and CD8+T cells, and regulatory T cells (Tregs). Low concentrations of IL-2 induce signaling through the high-affinity IL-2 receptor (IL-2R) comprised of IL-2Rα, IL-2Rβ, and common γ chain (γc), preferentially expressed on Tregs. Higher concentrations of IL-2 are necessary to induce signaling through the intermediate-affinity IL-2R, composed of IL-2Rβ and γc, expressed on memory CD8+T cells and NK cells. Recombinant human IL-2 (rhIL-2) is approved for treatment of metastatic melanoma and renal cell carcinoma (RCC), but adverse events including capillary leak syndrome, potentially mediated through interaction with the high-affinity IL-2R, limit its therapeutic use. Furthermore, antitumor efficacy of IL-2 may also be limited by preferential expansion of immunosuppressive Tregs. ALKS 4230 is an engineered fusion protein comprised of a circularly-permuted IL-2 with the extracellular domain of IL-2Rα, designed to selectively activate effector lymphocytes bearing the intermediate-affinity IL-2R.ResultsALKS 4230 was equipotent to rhIL-2 in activating human cells bearing the intermediate-affinity IL-2R, and less potent than rhIL-2 on cells bearing the high-affinity IL-2R. As observed in vitro with primary human cells from healthy donors and advanced cancer patients, ALKS 4230 induced greater activation and expansion of NK cells with reduced expansion of Tregsrelative to rhIL-2. Similarly, in mice, ALKS 4230 treatment stimulated greater expansion of NK cells and memory-phenotype CD8+T cells at doses that did not expand or activate Tregs. ALKS 4230 treatment induced significantly lower levels of proinflammatory cytokines, including tumor necrosis factor alpha, interleukin-6, and interferon gamma relative to rhIL-2. Furthermore, ALKS 4230 exhibited superior antitumor efficacy in the mouse B16F10 lung tumor model, where ALKS 4230 could be administered via multiple routes of administration and dosing schedules while achieving equivalent antitumor efficacy.ConclusionsALKS 4230 exhibited enhanced pharmacokinetic and selective pharmacodynamic properties resulting in both improved antitumor efficacy and lower indices of toxicity relative to rhIL-2 in mice. These data highlight the potential of ALKS 4230 as a novel cancer immunotherapy, and as such, the molecule is being evaluated clinically.

Immunomodulatory Effects of IL-2 and IL-15; Implications for Cancer Immunotherapy

“…Compared to wild-type IL-2, the superkine elicited enhanced expression of cytotoxic T cells but less of Treg cells [102]. Some newly developed fusion proteins that comprise IL-2 and IL-2Rα, such as ALKS 4230, could selectively active the effector cells bearing intermediate receptors, and exhibit superior tumor control efficacy and less toxicity in mouse tumor models [103]. Pharmacokinetic profile modification of IL-2 has been attained by chimerization with antibodies that direct the cytokine to the TME, or though covalent binding with moieties such as PEG molecules.…”

Targeting an engineered cytokine with interleukin-2 and interleukin-15 activity to the neovasculature of solid tumors

“…IL2 muteins may alter the interaction of the cytokine with one or more of the IL2 receptor subunits [ 20 ], thus altering the selectivity towards the intermediate affinity receptor [consisting of CD122 (IL2Rβ) and CD132 (γ C )] or towards the high affinity receptor [consisting of CD25 (IL2Rα), CD122, and CD132] [ 28 ]. Since regulatory T cells (Tregs) predominantly express the high affinity receptor [ 28 ], the selective activation of the intermediate affinity receptor (expressed by resting and memory lymphocytes including CD8 + T cells) [ 28 ] has attracted considerable research efforts [ 29 – 35 ]. In one approach, the strength of the interaction of IL2 with the cognate intermediate affinity receptor was increased through mutations, which also stabilized folding [ 34 ].…”

“…The increased CD8 + : Treg ratio correlated with an improved therapeutic effect [ 34 ]. In a second approach, an increased selectivity towards the intermediate affinity IL2 receptor was achieved by blocking the interaction with CD25 either through IL2 mutations or by antibody blockade of the IL2 epitope involved in CD25 binding [ 31 – 33 , 35 ]. Interestingly, a decreased IL2 toxicity was observed in CD25 knock-out mice [ 36 ].…”

A bispecific antibody agonist of the IL-2 heterodimeric receptor preferentially promotes in vivo expansion of CD8 and NK cells

“…Variant proteins that avoid the preferential activation of high-affinity IL-2R-expressing cells such as T-regs and vascular endothelial cells is one approach to achieving this goal. In an effort to create such a molecule, groups have mutated the IL-2Rα binding interface on IL-2, attached poly-ethylene glycol to the IL-2 protein, created synthetic IL-2 proteins, and generated an antibody that blocks the IL-2Rα binding domain [20][21][22][23][24][25] . As an alternative to IL-2, other groups have engineered IL-15 variants that bind to IL-2Rβ/ IL-2Rγ subunits.…”