Cytotoxic T-lymphocyte antigen 4 (CTLA4)-FasL, a homo-hexameric signal converter protein, is capable of inducing robust apoptosis in malignant cells of the B-cell lineage expressing its cognate B7 and Fas targets, while sparing nonmalignant ones. This fusion protein's striking proapoptotic efficacy stems from its complementary abilities to coordinately activate apoptotic signals and abrogate antiapoptotic ones. A limiting factor in translating FasL or Fas receptor agonists into the clinic has been lethal hepatotoxicity. Here, we establish CTLA4-FasL's in vivo efficacy in multiple murine and xenograft models, for both systemic and subcutaneous tumors. Significantly, good laboratory practice (GLP) toxicology studies in mice indicate that CTLA4-FasL given repeatedly at doses up to five times the effective dose was well-tolerated and resulted in no significant adverse events. An equivalent single dose of CTLA4-FasL administered to nonhuman primates was also well-tolerated, albeit with a moderate dose-dependent leukopenia that was completely reversible. Interestingly, monkey peripheral blood mononuclear cells were more sensitive to CTLA4-FasL–induced apoptosis when tested in vitro. In both species, there was short-term elevation in serum levels of IL6, IL2, and IFNγ, although this was not associated with clinical signs of proinflammatory cytokine release, and further, this cytokine elevation could be completely prevented by dexamethasone premedication. Liver toxicity was not observed in either species, as confirmed by serum liver enzyme levels and histopathologic assessment. In conclusion, CTLA4-FasL emerges from animal model studies as an effective and safe agent for targeted FasL-mediated treatment of B7-expressing aggressive B-cell lymphomas.

中文翻译：

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无毒、高效、靶向六聚体 FasL：CTLA4-FasL 在小鼠和非人类灵长类动物中的毒理学和药代动力学研究

细胞毒性 T 淋巴细胞抗原 4 (CTLA4)-FasL 是一种同源六聚体信号转换器蛋白，能够在表达其同源 B7 和 Fas 靶标的 B 细胞谱系的恶性细胞中诱导强烈的细胞凋亡，同时保留非恶性细胞。这种融合蛋白惊人的促凋亡功效源于其协同激活凋亡信号和消除抗凋亡信号的互补能力。将 FasL 或 Fas 受体激动剂转化为临床的一个限制因素是致命的肝毒性。在这里，我们建立了 CTLA4-FasL 在多种小鼠和异种移植模型中的体内功效，适用于全身性和皮下肿瘤。显着地，小鼠的良好实验室实践 (GLP) 毒理学研究表明，CTLA4-FasL 以高达有效剂量的五倍的剂量反复给药具有良好的耐受性，并且没有导致显着的不良事件。给予非人类灵长类动物的等效单剂量 CTLA4-FasL 也具有良好的耐受性，尽管具有完全可逆的中等剂量依赖性白细胞减少症。有趣的是，在体外测试时，猴外周血单核细胞对 CTLA4-FasL 诱导的细胞凋亡更敏感。在这两个物种中，IL6、IL2 和 IFNγ 的血清水平都有短期升高，尽管这与促炎细胞因子释放的临床症状无关，而且，这种细胞因子升高可以通过地塞米松术前用药完全预防。在任一物种中均未观察到肝毒性，经血清肝酶水平和组织病理学评估证实。总之，CTLA4-FasL 从动物模型研究中脱颖而出，作为一种有效且安全的药物，可用于靶向 FasL 介导的 B7 表达侵袭性 B 细胞淋巴瘤的治疗。