Synthesis of Carboxymethylpullulan-Peptide-Doxorubicin Conjugates and Their Properties.
作者:Hideo NOGUSA、Toshiro YANO、Satoshi OKUNO、Hiroshi HAMANA、Kazuhiro INOUE
DOI:10.1248/cpb.43.1931
日期:——
The amino group of doxorubicin (DXR) was found to be bound to the carboxyl group of carboxymethylpullulan (CMPul) either directly or through tetrapeptide spacers, including Gly-Gly-Phe-Gly, Gly-Phe-Gly-Gly and Gly-Gly-Gly-Gly. These conjugates had DXR contents of 6.1-7.1%, with the degree of substitution of carboxymethyl groups being 0.6 per sugar moiety. These conjugates associate in phosphate-buffered saline (PBS)(pH 7.4), forming micelles with hydrophobic DXR inside and hydrophilic CMPul on the outside. The amounts of DXR released from the conjugates in the presence of rat liver lysosomal enzymes were determined by HPLC. The rate of the drug release differed among the conjugates tested. CMPul-DXR conjugate bound through Gly-Gly-Phe-Gly released 35% of its DXR over 24 h. On the other hand, CMPul-DXR conjugate without spacer released no free DXR. The antitumor effect of each conjugate in rats bearing Walker 256 was studied by monitoring the tumor weights after a single intravenous injection. Compared with DXR, CMPul-DXR conjugates bound through Gly-Gly-Phe-Gly and Gly-Phe-Gly-Gly spacers significantly suppressed the tumor growth, while CMPul-DXR conjugate bound through Gly-Gly-Gly-Gly showed less antitumor effect than DXR. CMPul-DXR conjugate without spacer showed no in vivo antitumor effect even at a dose equivalent to as much as 20 mg/kg of DXR.
发现多柔比星(DXR)的氨基与羧甲基支链淀粉(CMPul)的羧基直接或通过包括甘-甘-苯丙-甘、甘-苯丙-甘-甘和甘-甘-甘-甘的四肽间隔物结合。这些偶联物的DXR含量为6.1-7.1%,羧甲基的取代度为每个糖单元0.6。这些偶联物在磷酸盐缓冲盐水(PBS,pH 7.4)中聚集,形成内部为疏水性DXR、外部为亲水性CMPul的胶束。通过高效液相色谱法测定了在大鼠肝脏溶酶体酶存在下,从这些偶联物中释放的DXR的量。药物释放速率因偶联物的不同而异。通过甘-甘-苯丙-甘连接的CMPul-DXR偶联物在24小时内释放了其35%的DXR。另一方面,没有间隔物的CMPul-DXR偶联物未释放出自由DXR。通过监测单次静脉注射后肿瘤重量,研究了每种偶联物对携带Walker 256肿瘤的大鼠的抗肿瘤效果。与DXR相比,通过甘-甘-苯丙-甘和甘-苯丙-甘-甘间隔物连接的CMPul-DXR偶联物显著抑制了肿瘤生长,而通过甘-甘-甘-甘连接的CMPul-DXR偶联物的抗肿瘤效果低于DXR。即使剂量相当于20 mg/kg的DXR,没有间隔物的CMPul-DXR偶联物也没有显示出体内抗肿瘤效果。