Design, synthesis, and evaluation of a novel pyrrolobenzodiazepine DNA-interactive agent with highly efficient cross-linking ability and potent cytotoxicity
Design, synthesis, and evaluation of a novel pyrrolobenzodiazepine DNA-interactive agent with highly efficient cross-linking ability and potent cytotoxicity
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DOI：
10.1021/jm001064n
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发表时间：
2001-03-01
影响因子：
7.3
通讯作者：
Thurston, DE
中科院分区：
文献类型：
--
作者：
Gregson, SJ;Howard, PW;Thurston, DE
一种新型的序列选择性吡罗苯二氮卓（PBD）二聚体5 （SJG-136）由两个c2 -外置亚甲基取代的DC-81(3)亚基通过惰性丙二氧连接剂连接到它们的C8位置。这种对称分子是一种高效的小槽链间DNA交联剂（XL(50) = 0.045 muM），其效力是melphalan的440倍。热变性研究表明，与小牛胸腺DNA以5:1的DNA/配体比例孵育18小时后，T(m)值增加了33.6度，这是迄今为止在该实验中记录的最高值。类似的二聚体4 （DSB-120）在C2位置缺乏取代/不饱和，在相同条件下仅提高了15.1度，说明引入C2-外不饱和的效果，可以使c环变平，并在DNA小槽内实现更好的等螺旋配合。这种行为得到了分子模型研究的支持，这些研究表明：(i) PBD单元与相反链上的鸟嘌呤共价结合形成交联，（ii） 5比4具有更大的结合能，（iii） 4和5具有跨越6个碱基对的等效结合位点。二聚体5在许多人卵巢癌细胞系中的细胞毒性明显高于4（例如，在A2780细胞中，IC（50）值分别为0.0225 nM和7.2 nM）。此外，它在顺铂耐药细胞系A2780cisR （0.024 nM）中保持充分的效力，而4失去活性（0.21 muM），耐药因子为29.2，这可能是由于细胞内含硫醇分子对5的失活水平较低。还合成并评价了缺乏亲电性N10-C11/N10‘-C11’亚胺基团的5的二乙酰坦类似物（21）。虽然21不能与DNA共价相互作用，但仍能稳定螺旋结构（DeltaT(m) = 0.78°），并在某些细胞系中具有显著的细胞毒性（即CH1细胞中的IC(50) = 0.57 muM），可能是通过与DNA的非共价相互作用发挥作用。
A novel sequence-selective pyrrolobenzodiazepine (PBD) dimer 5 (SJG-136) has been developed that comprises two C2-exo-methylene-substituted DC-81 (3) subunits tethered through their C8 positions via an inert propanedioxy linker. This symmetric molecule is a highly efficient minor groove interstrand DNA cross-linking agent (XL(50) = 0.045 muM) that is 440-fold more potent than melphalan, Thermal denaturation studies show that, after 18 h incubation with calf thymus DNA at a 5:1 DNA/ligand ratio, it increases the T(m) value by 33.6 degreesC, the highest value so far recorded in this assay. The analogous dimer 4 (DSB-120) that lacks substitution/ unsaturation at the C2 position elevates melting by only 15.1 degreesC under the same conditions, illustrating the effect of introducing C2-exo-unsaturation which serves to flatten the C-rings and achieve a superior isohelical fit within the DNA minor groove. This behavior is supported by molecular modeling studies which indicate that (i) the PBD units are covalently bonded to guanines on opposite strands to form a cross-link, (ii) 5 has a greater binding energy compared to 4, and (iii) 4 and 5 have equivalent binding sites that span six base pairs. Dimer 5 is significantly more cytotoxic than 4 in a number of human ovarian cancer cell lines (e.g., IC(50) values of 0.0225 nM vs 7.2 nM, respectively, in A2780 cells). Furthermore, it retains full potency in the cisplatin-resistant cell line A2780cisR (0.024 nM), whereas 4 loses activity (0.21 muM) with a resistance factor of 29.2, This may be due to a lower level of inactivation of 5 by intracellular thiol-containing molecules. A dilactam analogue (21) of 5 that lacks the electrophilic N10-C11/N10'-C11' imine moieties has also been synthesized and evaluated. Although unable to interact covalently with DNA, 21 still stabilizes the helix (DeltaT(m) = 0.78 degreesC) and has significant cytotoxicity in some cell lines (i.e., IC(50) = 0.57 muM in CH1 cells), presumably exerting its effect through noncovalent interaction with DNA.