DataSheet_1_SON-1210 - a novel bifunctional IL-12 / IL-15 fusion protein that improves cytokine half-life, targets tumors, and enhances therapeutic efficacy.pdf

BackgroundThe potential synergy between interleukin-12 (IL-12) and IL-15 holds promise for more effective solid tumor immunotherapy. Nevertheless, previous clinical trials involving therapeutic cytokines have encountered obstacles such as short pharmacokinetics, limited tumor microenvironment (TME) targeting, and substantial systemic toxicity.
MethodsTo address these challenges, we fused single-chain human IL-12 and native human IL-15 in cis onto a fully human albumin binding (FHAB) domain single-chain antibody fragment (scFv). This novel fusion protein, IL12-FHAB-IL15 (SON-1210), is anticipated to amplify the therapeutic impact of interleukins and combination immunotherapies in human TME. The molecule was studied in vitro and in animal models to assess its pharmacokinetics, potency, functional characteristics, safety, immune response, and efficacy.
ResultsSON-1210 demonstrated robust binding affinity to albumin and exhibited the anticipated in vitro activity and tumor model efficacy that might be expected based on decades of research on native IL-12 and IL-15. Notably, in the B16F10 melanoma model (a non-immunogenic, relatively “cold” tumor), the murine counterpart of the construct, which had mouse (m) and human (h) cytokine sequences for the respective payloads (mIL12-FHAB-hIL15), outperformed equimolar doses of the co-administered native cytokines in a dose-dependent manner. A single dose caused a marked reduction in tumor growth that was concomitant with increased IFNγ levels; increased Th1, CTL, and activated NK cells; a shift in macrophages from the M2 to M1 phenotype; and a reduction in Treg cells. In addition, a repeat-dose non-human primate (NHP) toxicology study displayed excellent tolerability up to 62.5 µg/kg of SON-1210 administered three times, which was accompanied by the anticipated increases in IFNγ levels. Toxicokinetic analyses showed sustained serum levels of SON-1210, using a sandwich ELISA with anti-IL-15 for capture and biotinylated anti-IL-12 for detection, along with sustained IFNγ levels, indicating prolonged kinetics and biological activity.
ConclusionCollectively, these findings support the suitability of SON-1210 for patient trials in terms of activity, efficacy, and safety, offering a promising opportunity for solid tumor immunotherapy. Linking cytokine payloads to a fully human albumin binding domain provides an indirect opportunity to target the TME using potent cytokines in cis that can redirect the immune response and control tumor growth.

背景：白细胞介素12（interleukin-12, IL-12）与IL-15之间的潜在协同效应，为更高效的实体瘤免疫治疗带来了希望。然而，既往涉及治疗性细胞因子的临床试验曾遭遇诸多障碍，包括药代动力学时长过短、肿瘤微环境（tumor microenvironment, TME）靶向性不足，以及严重的全身性毒性。
方法：为应对上述挑战，本研究将单链人源IL-12与天然人源IL-15顺式融合至全人源白蛋白结合（fully human albumin binding, FHAB）结构域单链抗体片段（single-chain antibody fragment, scFv）上。这款新型融合蛋白IL12-FHAB-IL15（代号SON-1210），有望增强细胞因子联合免疫疗法在人体肿瘤微环境中的治疗效果。本研究通过体外实验与动物模型，对该分子的药代动力学、效力、功能特性、安全性、免疫应答及抗肿瘤疗效进行了评估。
结果：SON-1210对白蛋白展现出强劲的结合亲和力，并呈现出基于天然IL-12与IL-15数十年研究可预期的体外活性与肿瘤模型疗效。值得注意的是，在B16F10黑色素瘤模型（一种非免疫原性、相对“冷”肿瘤）中，该构建体的鼠源对应物（携带小鼠源mIL12与人源hIL15细胞因子有效载荷，即mIL12-FHAB-hIL15），以剂量依赖的方式优于等摩尔剂量的共给药天然细胞因子。单次给药即可显著抑制肿瘤生长，同时伴随干扰素γ（IFNγ）水平升高、Th1细胞、细胞毒性T淋巴细胞（CTL）与活化自然杀伤（NK）细胞数量增加、巨噬细胞从M2表型向M1表型转化，以及调节性T细胞（Treg）数量减少。此外，一项重复给药的非人灵长类（non-human primate, NHP）毒理学研究显示，SON-1210在3次给药、剂量高达62.5 μg/kg时仍具有优异的耐受性，同时伴随预期的IFNγ水平升高。毒代动力学分析显示，采用以抗IL-15抗体包被捕获、生物素标记抗IL-12抗体检测的夹心酶联免疫吸附试验（sandwich ELISA），可检测到SON-1210的血清浓度持续维持，同时IFNγ水平也持续升高，表明其药代动力学时长与生物活性均得到延长。
结论：综上，上述研究结果从活性、疗效与安全性层面证实了SON-1210适用于患者临床试验，为实体瘤免疫治疗提供了极具前景的新策略。将细胞因子有效载荷与全人源白蛋白结合结构域相连，为通过顺式作用的强效细胞因子靶向肿瘤微环境提供了间接途径，可重塑免疫应答并控制肿瘤生长。