1a-N-Stearoyl mitomycin C (MMC) and six 1a-N-substituted derivatives of MMC possessing the cholesteryl moiety with different spacers were synthesized, and their biopharmaceutical properties were studied to assess the feasibility of such derivatives as prodrugs for intravenously injectable liposomal sustained-release carrier systems. All compounds showed increased lipophilic indices (logk'0) in high performance liquid chromatography. It was found that all the derivatives could be almost completely entrapped in liposomes, although MMC itself was hardly encapsulated. The derivatives with the exception of cholesteryloxycarbonyl MMC (II) and N-(cholesteryloxy-carbonyl)-4-aminophenylacetyl MMC (VI) were converted to the parent drug in rat serum. The suceptibility of the compounds to hydrolysis was strongly affected by the spacer structure between MMC and the cholesteryl moiety. Cholesteryloxyacetyl MMC (IV) was converted to MMC mainly by chemical hydrolysis. N-(Cholesteryloxycarbonyl)glycyl MMC (III) was also hydrolyzed to MMC chemically but in this case hydrolysis was accelerated in the presence of mouse, rat and human serum. No species differences were observed in these bioactivation phenomena. Entrapment of derivatives III and IV in liposomes resulted in enhancement of the stability against both chemical and enzymatic hydrolysis. The derivatives possessing the cholesteryl moiety were firmly associated with liposomes in the circulation, while stearoyl MMC (VIII) was rapidly recoved. These results suggest that derivatives III and IV have the potential to be utilized as lipophilic prodrugs for liposomal sustained-release carrier systems to be delivered by intravenous injection.
1a-N-硬脂酰基丝
裂霉素C(MMC)及其六种具有
胆固醇基团的MMC衍生替代品(含不同的间隔基)被合成,并研究了它们的药物特性,以评估这些衍
生物作为静脉注射脂质体长效释放载体系统的药物前体的可行性。所有化合物在高效
液相色谱中显示出增加的脂溶性指数(logk'0)。发现所有衍
生物几乎可以完全被包裹在脂质体中,尽管MMC本身很难被包裹。除了
胆固醇氧甲酰MMC(II)和N-(
胆固醇氧甲酰基)-4-
氨基
苯乙酰基MMC(VI)之外,所有其他衍
生物在鼠血清中转化为其母体药物。这些化合物对
水解作用的影响受到了MMC和
胆固醇基团之间间隔基结构的强烈影响。
胆固醇氧乙酰基MMC(IV)主要由
化学水解转化为MMC。N-(
胆固醇氧甲酰基)甘
氨酰MMC(III)也被
化学水解为MMC,但在这种情况下,在小鼠、大鼠和人类血清中的
水解作用被加速。在这些
生物活化现象中没有观察到物种差异。将III和IV衍
生物包裹在脂质体中,增强了其抵御
化学和酶
水解的稳定性。具有
胆固醇基团的衍
生物在循环中与脂质体紧密结合,而硬脂酰MMC(VIII)则迅速恢复。这些结果表明,III和IV衍
生物有可能作为脂质体长效释放载体系统的脂溶性药物前体,通过静脉注射进行输送。