Single Agents with Designed Combination Chemotherapy Potential

针对受体酪氨酸激酶(RTK)的分子靶向药物，特别是抗血管生成药物(AAs)，已经引起了癌症化疗的范式转变。这些药物针对的是肿瘤血管生成机制(新血管的萌发)，这些机制在正常细胞中是不存在的(除了伤口愈合、月经周期和怀孕)，但对肿瘤的生长和转移至关重要。血管生成途径是多余的，多靶点AAs是消除血管生成所必需的。AAS主要是抑制细胞生长和阻止肿瘤生长，但不杀死肿瘤。因此，AAs和细胞毒剂的组合显示出了巨大的前景，数百项这样的临床试验证明了它们的临床相关性。两种或两种以上药物的药代动力学差异、药-药相互作用、重叠毒性、多种药物的成本和患者的依从性是联合化疗失败的重要方面。对于与细胞毒剂联合使用的AAs，要求甚至更严格。一些重要的抗血管生成作用，如肿瘤血管正常化，是暂时表现出来的，单独使用细胞毒剂可能会完全错过这个短暂的窗口。联合化疗并不是一个新的想法，新颖的是设计一种既具有多种抗血管生成活性又具有细胞毒性的单一药物。这样的单一药物将绕过两个或两个以上单独药物的缺点，并提供单分子联合化疗的潜力。当抗血管生成作用发生时，这种“现场”单药的细胞毒性效应就会显现出来，因此不需要像单独使用细胞毒性药物那样计时或有效(因此毒性较小)。我们最近发现了两个化合物AAG14843和AAG148311，它们分别抑制VEGFR-2和PDGFR-1(肿瘤血管生成作用)，并显著抑制人胸苷酸合成酶(HTS)(细胞毒作用)。抑制力 与VEGFR-2(SU5416)、PDGFR-$(DMBI)和HTS(培美曲塞，Alimta)的标准抑制剂相当。在Colo-205异种移植小鼠模型中，与对照相比，AAG14843显著减少了肿瘤生长、肝脏转移和原发肿瘤中的血管。具体目标是：1.合成AAG14843和AAG148311类似物，进行构效关系研究、三维定量构效关系研究，优化其对VEGFR-2、PDGFR-1、HTS的抑制活性和抗肿瘤活性。2.)检测特异性靶点1的类似物对EGFR、VEGFR-1和2、PDGFR-$、P13K、Flt3、A431细胞、hDHFR、HTS和CAM的抑制作用。3.)为了评价AAG14843(在其他异种移植模型中)、AAG148311和另外三个类似物的体内毒性、抗肿瘤活性、转移和抗血管生成活性 肿瘤小鼠模型中的特异性靶点1和2。这项研究将提供一种具有AAG14843优化属性的SAR和药物，并允许选择将用于单一治疗、与其他药物和/或放射临床使用的药物相结合的药物，比目前使用的组合具有更高的疗效和更低的毒性。

Molecularly targeted agents against receptor tyrosine kinases (RTK), particularly the antiangiogenic agents (AAs), have caused a paradigm shift in cancer chemotherapy. These agents target tumor angiogenic mechanisms (sprouting of new blood vessels) that are absent in normal cells (except wound healing, menstrual cycle and pregnancy) but are vital for tumor growth and metastases. Angiogenesis pathways are redundant and multi-targeted AAs are necessary to abrogate angiogenesis. AAs are mainly cytostatic and arrest tumor growth but do not kill tumors. Thus combinations of AAs and cytotoxic agents have shown significant promise, and hundreds of such clinical trials attest to their clinical relevance. Pharmacokinetic differences of two or more drugs, drug-drug interactions, overlapping toxicities, cost of multiple drugs and patient compliance are important facets of combination chemotherapy failure. For AAs in combination with cytotoxic agents there are even more stringent requirements. Some important antiangiogenic effects like tumor vascular normalization are transiently manifested and a separately administered cytotoxic agent might completely miss this transient window. Combination chemotherapy is not a new idea, what would be novel is the design of a single agent with both multiple antiangiogenic activities as well as cytotoxicity. Such single agents would circumvent the disadvantages of two or more separate agents and afford combination chemotherapy potential in single molecules. The cytotoxic effects of such “on the spot” single agents would be manifested when dictated by the antiangiogenic effects and hence would not need to be timed or be as potent (hence less toxic) as separately administered cytotoxic agents. We have recently discovered two compounds AAG14843 and AAG148311 that each inhibit VEGFR-2 and PDGFR-$, (tumor angiogenic effects) and remarkably also inhibit human thymidylate synthase (hTS) (cytotoxic effects). The inhibitory potencies are comparable to standard inhibitors of VEGFR-2 (SU5416), PDGFR-$ (DMBI) and hTS (pemetrexed, Alimta). In a COLO-205 xenograft mouse model AAG14843 significantly decreased tumor growth, liver metastases and blood vessels in the primary tumor compared to control. The Specific Aims are: 1.) to synthesize analogs of AAG14843 and AAG148311 to provide a structure-activity relationship (SAR) study, 3D QSAR and to optimize inhibitory activity against VEGFR-2, PDGFR-$ and hTS and antitumor activity. 2.) To test analogs from Specific Aim 1 against EGFR, VEGFR-1 and 2, PDGFR-$, P13K, FLT3, A431 cells, hDHFR, hTS and in the CAM assay. 3.) To evaluate in vivo toxicity, antitumor activity, metastases and antiangiogenic activity of AAG14843 (in other xenograft models), AAG148311 and three additional analogs identified from Specific Aims 1 and 2 in tumor mouse models. This study will afford a SAR and agents with optimized attributes of AAG14843 and allow the selection of agents to be developed for monotherapy, in combination with other agents and/or radiation for clinical use with greater efficacy and reduced toxicity than combinations currently in use.