Endocyte, Inc., 3000 Kent Avenue, West Lafayette, IN 47906, USA.
Arthritis Res Ther. 2011 Apr 4;13(2):R56. doi: 10.1186/ar3304.
Folate receptor (FR)-expressing macrophages have been shown to accumulate at sites of inflammation, where they promote development of inflammatory symptoms. To target such a macrophage population, we designed and evaluated the biologic activity of EC0746, a novel folic acid conjugate of the highly potent antifolate, aminopterin.
Using a FR-positive subclone of murine macrophage-derived RAW264.7 cells and rat thioglycollate-elicited macrophages, we studied the effect of EC0746 on dihydrofolate reductase activity, cell proliferation, and cellular response towards bacterial lipopolysaccharide as well as IFNγ activation. The EC0746 anti-inflammatory activity, pharmacokinetics, and toxicity were also evaluated in normal rats or in rats with adjuvant-induced arthritis; that is, a FR-positive macrophage model that closely resembles rheumatoid arthritis in humans.
EC0746 suppresses the proliferation of RAW264.7 cells and prevents the ability of nonproliferating rat macrophages to respond to inflammatory stimuli. In the macrophage-rich rat arthritis model, brief treatment with subcutaneously administered EC0746 is shown to mediate an FR-specific anti-inflammatory response that is more potent than either orally administered methotrexate or subcutaneously delivered etanercept. More importantly, EC0746 therapy is also shown to be ~40-fold less toxic than unmodified aminopterin, with fewer bone marrow and gastrointestinal problems.
EC0746 is the first high FR-binding dihydrofolate reductase inhibitor that demonstrates FR-specific anti-inflammatory activities both in vitro and in vivo. Our data reveal that a relatively toxic anti-inflammatory drug, such as aminopterin, can be targeted with folic acid to inflammatory macrophages and thereby relieve inflammatory symptoms with greatly reduced toxicity.
已有研究表明，叶酸受体（FR）表达的巨噬细胞会在炎症部位聚集，从而促进炎症症状的发展。为了靶向这种巨噬细胞群体，我们设计并评估了 EC0746 的生物学活性，它是一种新型叶酸缀合物，由强效抗叶酸药氨喋呤衍生而来。
我们使用 FR 阳性的鼠源巨噬细胞 RAW264.7 细胞亚克隆和大鼠巯基乙酸酯诱导的巨噬细胞，研究了 EC0746 对二氢叶酸还原酶活性、细胞增殖以及细胞对细菌脂多糖和 IFNγ激活的反应的影响。还在正常大鼠或佐剂诱导关节炎大鼠（即 FR 阳性巨噬细胞模型，与人的类风湿关节炎非常相似）中评估了 EC0746 的抗炎活性、药代动力学和毒性。
EC0746 抑制 RAW264.7 细胞的增殖，并阻止非增殖大鼠巨噬细胞对炎症刺激的反应能力。在富含巨噬细胞的大鼠关节炎模型中，短暂给予皮下注射的 EC0746 可介导 FR 特异性抗炎反应，其效力强于口服甲氨蝶呤或皮下给予依那西普。更重要的是，与未修饰的氨喋呤相比，EC0746 治疗的毒性也低约 40 倍，骨髓和胃肠道问题更少。
EC0746 是第一个具有高 FR 结合能力的二氢叶酸还原酶抑制剂，它在体外和体内均表现出 FR 特异性抗炎活性。我们的数据表明，一种相对毒性的抗炎药物，如氨喋呤，可以通过叶酸靶向炎症巨噬细胞，从而大大降低毒性来缓解炎症症状。
