Houba P H, Leenders R G, Boven E, Scheeren J W, Pinedo H M, Haisma H J
Department of Medical Oncology, Academic Hospital Vrije Universiteit, Amsterdam, The Netherlands.
Biochem Pharmacol. 1996 Aug 9;52(3):455-63. doi: 10.1016/0006-2952(96)00248-1.
Antibody-directed enzyme prodrug therapy (ADEPT) aims at the specific activation of a prodrug by an enzyme-immunoconjugate localized in tumor tissue. The use of an enzyme of human origin is preferable in ADEPT because it might not be immunogenic when administered to patients. In the case of human beta-glucuronidase, prodrugs should be designed that are rapidly and completely activated at a neutral pH. Four new daunorubicin glucuronides were synthesized by coupling a glucuronide group to daunorubicin via an aliphatic (GA1 and GB1) or an aromatic (GA3, GB6) carbamate spacer, to be released by electron shift (A-type) or by ring closure (B-type). These prodrugs were characterized in vitro for their usefulness in ADEPT and were compared with the previously described prodrugs epirubicin-glucuronide and doxorubicin-nitrophenyl-glucuronide. The four new prodrugs were stable in serum, hydrophilic when compared to the lipophilic daunorubicin, and at least 20-fold less toxic than the parent compound. The hydrolysis rate at clinically relevant enzyme and prodrug concentrations (1 microgram/mL human beta-glucuronidase, 100 microM prodrug) at pH 6.8 were similar for GA3 (T1/2 160 min) and higher for GB6 (T1/2 40 min) when compared to that of doxorubicin-nitrophenyl-glucuronide (T1/2 170 min). Epirubicin-glucuronide, GA1, and GB1 showed a low hydrolysis rate (T1/2 > 400 min). GA1 and GA3, but not GB1 or GB6, were activated to the parent compound. Complete activation was confirmed in OVCAR-3 cells pretreated with a specific antibody-human beta-glucuronidase conjugate, where GA3 had similar antiproliferative effects to those of daunorubicin.
抗体导向酶前药疗法（ADEPT）旨在通过定位在肿瘤组织中的酶免疫缀合物特异性激活前药。在ADEPT中，使用源自人类的酶更为可取，因为给患者使用时它可能不会具有免疫原性。就人β-葡萄糖醛酸酶而言，应设计在中性pH下能快速且完全激活的前药。通过经由脂肪族（GA1和GB1）或芳香族（GA3、GB6）氨基甲酸酯间隔基将葡萄糖醛酸基团与柔红霉素偶联，合成了四种新的柔红霉素葡萄糖醛酸苷，它们可通过电子转移（A型）或闭环（B型）释放。对这些前药进行了体外表征，以评估其在ADEPT中的效用，并与先前描述的前药表柔比星-葡萄糖醛酸苷和多柔比星-硝基苯基-葡萄糖醛酸苷进行了比较。这四种新前药在血清中稳定，与亲脂性的柔红霉素相比具有亲水性，且毒性比母体化合物至少低20倍。在pH 6.8时，在临床相关的酶和前药浓度（1微克/毫升人β-葡萄糖醛酸酶，100微摩尔前药）下，GA3（半衰期160分钟）的水解速率与多柔比星-硝基苯基-葡萄糖醛酸苷（半衰期170分钟）相似，GB6（半衰期40分钟）的水解速率更高。表柔比星-葡萄糖醛酸苷、GA1和GB1的水解速率较低（半衰期>400分钟）。GA1和GA3，但不是GB1或GB6，被激活为母体化合物。在用特异性抗体-人β-葡萄糖醛酸酶缀合物预处理的OVCAR-3细胞中证实了完全激活，其中GA3具有与柔红霉素相似的抗增殖作用。
