Lee Tong-Young, Tjin Tham Sjin Robert M, Movahedi Shahla, Ahmed Bissan, Pravda Elke A, Lo Kin-Ming, Gillies Stephen D, Folkman Judah, Javaherian Kashi
Vascular Biology Program, Department of Surgery, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts 02115, USA.
Clin Cancer Res. 2008 Mar 1;14(5):1487-93. doi: 10.1158/1078-0432.CCR-07-1530.
The half-life of the antiangiogenic molecule endostatin that has been used in clinical trial is short ( approximately 2 h). In addition, approximately 50% of the clinical grade endostatin molecules lack four amino acids at their NH(2) termini. Lack of these amino acids gives rise to a molecule that is devoid of zinc, resulting in no antitumor activity. Our goal was to develop a new version of endostatin that does not show such deficiency.
A recombinant human endostatin conjugated to the Fc domain of IgG was constructed and expressed in mammalian cell culture. The presence of Fc has been shown by previous investigators to play a major role in increasing the half-life of the molecule. Fc-endostatin was tested in tumor-bearing mice, and its half-life was compared with the clinical grade endostatin.
The antitumor dose of Fc-endostatin was found to be approximately 100 times less than the clinical grade endostatin. The half-life of Fc-endostatin in the circulation was found to be weeks rather than hours, as observed for endostatin alone. In addition, a U-shaped curve was observed for antitumor activity of endostatin as a function of endostatin concentration delivered to the animals.
Fc-endostatin is a superior molecule to the original clinical endostatin. Due to its long half-life, the amount of protein required is substantially reduced compared with the clinically tested endostatin. Furthermore, in view of the U-shaped curve of efficacy observed for endostatin, we estimate that the requirement for Fc-endostatin is approximately 700-fold less than endostatin alone. The half-life of endostatin is similar to that of vascular endothelial growth factor-Trap and Avastin, two other antiangiogenic reagents. We conclude that a new clinical trial of endostatin, incorporating Fc, may benefit cancer patients.
用于临床试验的抗血管生成分子内皮抑素半衰期较短（约2小时）。此外，约50%的临床级内皮抑素分子在其NH₂末端缺少四个氨基酸。这些氨基酸的缺失导致分子不含锌，从而没有抗肿瘤活性。我们的目标是开发一种不存在此类缺陷的新型内皮抑素。
构建了一种与IgG的Fc结构域偶联的重组人内皮抑素，并在哺乳动物细胞培养中表达。先前的研究人员已表明Fc在延长分子半衰期方面起主要作用。对荷瘤小鼠进行了Fc-内皮抑素测试，并将其半衰期与临床级内皮抑素进行了比较。
发现Fc-内皮抑素的抗肿瘤剂量约为临床级内皮抑素的1/100。Fc-内皮抑素在循环中的半衰期为数周，而单独的内皮抑素半衰期仅为数小时。此外，观察到内皮抑素的抗肿瘤活性随给予动物的内皮抑素浓度呈U形曲线。
Fc-内皮抑素是一种优于原始临床内皮抑素的分子。由于其半衰期长，与经过临床测试的内皮抑素相比，所需的蛋白量大幅减少。此外，鉴于观察到内皮抑素的疗效呈U形曲线，我们估计Fc-内皮抑素的需求量比单独的内皮抑素少约700倍。内皮抑素的半衰期与另外两种抗血管生成试剂血管内皮生长因子受体-抗体融合蛋白和阿瓦斯汀相似。我们得出结论，纳入Fc的内皮抑素新临床试验可能会使癌症患者受益。
