Yang Jiyuan, Zhang Rui, Pan Huaizhong, Li Yuling, Fang Yixin, Zhang Libin, Kopeček Jindřich
TheraTarget, Inc., Salt Lake City, Utah 84112, United States.
Mol Pharm. 2017 May 1;14(5):1384-1394. doi: 10.1021/acs.molpharmaceut.6b01005. Epub 2017 Feb 3.
Degradable diblock and multiblock (tetrablock and hexablock) N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-gemcitabine (GEM) and -paclitaxel (PTX) conjugates were synthesized by reversible addition-fragmentation chain-transter (RAFT) copolymerization followed by click reaction for preclinical investigation. The aim was to validate the hypothesis that long-circulating conjugates are needed to generate a sustained concentration gradient between vasculature and a solid tumor and result in significant anticancer effect. To evaluate the impact of molecular weight of the conjugates on treatment efficacy, diblock, tetrablock, and hexablock GEM and PTX conjugates were administered intravenously to nude mice bearing A2780 human ovarian xenografts. For GEM conjugates, triple doses with dosage 5 mg/kg were given on days 0, 7, and 14 (q7dx3), whereas a single dose regime with 20 mg/kg was applied on day 0 for PTX conjugates treatment. The most effective conjugates for each monotherapy were the diblock ones, 2P-GEM and 2P-PTX (Mw ≈ 100 kDa). Increasing the Mw to 200 or 300 kDa resulted in decrease of activity most probably due to changes in the conformation of the macromolecule because of interaction of hydrophobic residues at side chain termini and formation of "unimer micelles". In addition to monotherapy, a sequential combination treatment of diblock PTX conjugate followed by GEM conjugate (2P-PTX/2P-GEM) was also performed, which showed the best tumor growth inhibition due to synergistic effect: complete remission was achieved after the first treatment cycle. However, because of low dose applied, tumor recurrence was observed 2 weeks after cease of treatment. To assess optimal route of administration, intraperitoneal (i.p.) application of 2P-GEM, 2P-PTX, and their combination was examined. The fact that the highest anticancer efficiency was achieved with diblock conjugates that can be synthesized in one scalable step bodes well for the translation into clinics.
通过可逆加成-断裂链转移（RAFT）共聚反应，随后进行点击反应，合成了可降解的二嵌段和多嵌段（四嵌段和六嵌段）N-(2-羟丙基)甲基丙烯酰胺（HPMA）共聚物-吉西他滨（GEM）和-紫杉醇（PTX）缀合物，用于临床前研究。目的是验证这样一个假设，即需要长循环缀合物在脉管系统和实体瘤之间产生持续的浓度梯度，并产生显著的抗癌效果。为了评估缀合物分子量对治疗效果的影响，将二嵌段、四嵌段和六嵌段GEM和PTX缀合物静脉注射给携带A2780人卵巢异种移植瘤的裸鼠。对于GEM缀合物，在第0、7和14天给予剂量为5mg/kg的三次剂量（每7天一次，共3次），而对于PTX缀合物治疗，在第0天采用20mg/kg的单次剂量方案。每种单一疗法中最有效的缀合物是二嵌段的，2P-GEM和2P-PTX（Mw≈100kDa）。将Mw增加到200或300kDa导致活性降低，最可能的原因是由于侧链末端疏水残基的相互作用以及“单分子胶束”的形成，大分子构象发生了变化。除了单一疗法外，还进行了二嵌段PTX缀合物后接GEM缀合物（2P-PTX/2P-GEM）的序贯联合治疗，由于协同作用，该联合治疗显示出最佳的肿瘤生长抑制效果：在第一个治疗周期后实现了完全缓解。然而，由于给药剂量较低，在治疗停止2周后观察到肿瘤复发。为了评估最佳给药途径，研究了2P-GEM、2P-PTX及其组合的腹腔内（i.p.）应用。可以通过一个可扩展步骤合成的二嵌段缀合物实现了最高的抗癌效率，这对于转化为临床应用来说是个好兆头。
