Despite the advances in cancer treatment achieved, for example, by the CD20 antibody rituximab, an urgent medical need remains to optimize the capacity of such antibodies to induce antibody-dependent cellular cytotoxicity (ADCC) that determines therapeutic efficacy. The cytokine IL-15 stimulates proliferation, activation, and cytolytic capacity of NK cells, but broad clinical use is prevented by short half-life, poor accumulation at the tumor site, and severe toxicity due to unspecific immune activation. We here report modified immunocytokines consisting of Fc-optimized CD19 and CD20 antibodies fused to an IL-15 moiety comprising an L45E-E46K double mutation (MIC⁺ format). The E46K mutation abrogated binding to IL-15Rα, thereby enabling substitution of physiological trans-presentation by target binding and thus conditional IL-15Rβγ stimulation, whereas the L45E mutation optimized IL-15Rβγ agonism and producibility. In vitro analysis of NK activation, anti-leukemia reactivity, and toxicity using autologous and allogeneic B cells confirmed target-dependent function of MIC⁺ constructs. Compared with Fc-optimized CD19 and CD20 antibodies, MIC⁺ constructs mediated superior target cell killing and NK cell proliferation. Mouse models using luciferase-expressing human NALM-6 lymphoma cells, patient acute lymphoblastic leukemia (ALL) cells, and murine EL-4 lymphoma cells transduced with human CD19/CD20 as targets and human and murine NK cells as effectors, respectively, confirmed superior and target-dependent anti-leukemic activity. In summary, MIC⁺ constructs combine the benefits of Fc-optimized antibodies and IL-15 cytokine activity and mediate superior NK cell immunity with potentially reduced side effects. They thus constitute a promising new immunotherapeutic approach shown here for B cell malignancies.

中文翻译：

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具有靶细胞限制 IL-15 活性的免疫细胞因子用于治疗 B 细胞恶性肿瘤

尽管在癌症治疗方面取得了进展，例如 CD20 抗体利妥昔单抗，但仍然迫切需要优化此类抗体诱导决定治疗效果的抗体依赖性细胞毒性 (ADCC) 的能力。细胞因子 IL-15 刺激 NK 细胞的增殖、活化和溶细胞能力，但由于半衰期短、在肿瘤部位积累不良以及非特异性免疫激活导致的严重毒性，阻碍了其广泛的临床应用。我们在这里报告了由 Fc 优化的 CD19 和 CD20 抗体与包含 L45E-E46K 双突变的 IL-15 部分融合组成的修饰免疫细胞因子（MIC ⁺格式）。E46K突变消除了与IL-15Rα的结合，从而能够通过靶标结合替代生理反式呈递，从而实现条件性IL-15Rβγ刺激，而L45E突变优化了IL-15Rβγ激动和生产能力。使用自体和同种异体 B 细胞对 NK 活化、抗白血病反应性和毒性进行体外分析，证实了 MIC ⁺构建体的靶标依赖性功能。与 Fc 优化的 CD19 和 CD20 抗体相比，MIC ⁺构建体介导了更好的靶细胞杀伤和 NK 细胞增殖。使用表达荧光素酶的人 NALM-6 淋巴瘤细胞、患者急性淋巴细胞白血病 (ALL) 细胞和分别用人 CD19/CD20 转导的小鼠 EL-4 淋巴瘤细胞作为靶标，以及人和小鼠 NK 细胞作为效应细胞的小鼠模型证实了优越性和靶点依赖性抗白血病活性。总之，MIC ⁺构建体结合了 Fc 优化抗体和 IL-15 细胞因子活性的优点，介导卓越的 NK 细胞免疫，并可能减少副作用。因此，它们构成了一种有前途的新的 B 细胞恶性肿瘤免疫治疗方法。