Development and Evaluation of Purine and Coumarin Based Hsp90 Inhibitors`

描述（由申请人提供）：目前正在进行的26项临床试验证明，90 kDa热休克蛋白是非凡的癌症化疗靶点。不幸的是，所有这些试验都是基于n端抑制剂格尔达霉素，由于其氧化还原活性和亲电的醌环，格尔达霉素具有严重的配方困难，并且产生与抑制Hsp90无关的毒性。目前只报道了该分子的一次全合成，43步后总收率为0.017%，说明类似物的制备难度较大。最近，Neckers和同事确定Hsp90含有c端ATP结合位点，与香豆素抗生素竞争性地结合ATP。与n端抑制剂一样，c端结合域的抑制剂也会导致参与肿瘤细胞生长和增殖的hsp90依赖性客户蛋白的降解。香豆素类抗生素的一个主要缺点是它们与Hsp90结合较弱（IC50约为700微摩尔）；然而，它们仍然是文献中描述的最有效的c端抑制剂。我们最近与Len Neckers和Jeff Holzbeierlein合作发现了一种比香豆素抗生素活性高700-7000倍的化合物。该分子已在几种肿瘤细胞系中进行了评估，并对多种Hsp90客户蛋白具有有效活性。为了提高我们的先导分子的效力，我们建议将核苷酸特异性底物中存在的功能结合到我们的先导化合物中，以提供与Hsp90 c端结合位点的额外相互作用。此外，我们建议评估我们的先导化合物在小鼠前列腺癌异种移植模型中的作用。最后，我们提出，通过低剂量的先导化合物或任何改进的类似物破坏Hsp90蛋白折叠机制，它将提供一个可接受的浓度的其他临床使用的抗肿瘤药物来诱导细胞凋亡，而不会产生有害的副作用。由于这些研究的结果，我们相信我们可以为开发新的Hsp90蛋白折叠过程抑制剂提供基础，而不会产生目前在临床试验中困扰的格尔达霉素衍生物的有害副作用。

DESCRIPTION (provided by applicant): The 90 kDa heat shock proteins are proving to be extraordinary cancer chemotherapeutic targets as evidenced by the fact that 26 clinical trials are currently in progress. Unfortunately, all of these trials are based upon the N-terminal inhibitor, geldanamycin, which has serious formulation difficulties and produces toxicity unrelated to Hsp90 inhibition by virtue of its redox-active and electrophilic quinone ring. Only one total synthesis of this molecule has been reported, and the overall yield was 0.017% after 43 steps, suggesting that the preparation of analogues would be difficult. More recently, Neckers and coworkers determined that Hsp90 contains a C-terminal ATP binding site that bound coumarin antibiotics competitively versus ATP. Like N-terminal inhibitors, inhibitors of the C-terminal binding domain also cause the degradation of Hsp90-dependent client proteins involved in tumor cell growth and proliferation. A major drawback of the coumarin antibiotics is that they bind weakly to Hsp90 (IC50 approximately 700 micromolar); however, they remain the most potent C-terminal inhibitors described in the literature. We have recently identified a compound that is 700-7000 x's more active than the coumarin antibiotic in collaboration with Len Neckers and Jeff Holzbeierlein. This molecule has been evaluated in several tumor cell lines and has potent activity against a wide range of Hsp90 client proteins. In an effort to increase the potency of our lead molecule, we have proposed to incorporate functionalities that exist in the nucleotide specific substrates onto our lead compound to afford additional interactions with the Hsp90 C-terminal binding site. In addition, we propose to evaluate our lead compound in murine xenograft models of prostate cancer. Finally, it is proposed that by compromising the Hsp90 protein folding machinery with low doses of our lead compound, or any improved analogue, it will provide an acceptable concentration of other clinically used anti-tumor agents to induce apoptosis without detrimental side effects. As a consequence of these studies, we believe we can provide a basis upon which new inhibitors of the Hsp90 protein folding process can be developed without the deleterious side effects of the geldanamycin derivatives that are currently plagued in clinical trials.