Human-Enzyme Mediated, Systemic Depletion of Cystine for Cancer Treatment.

描述（由申请人提供）：大量研究表明，与正常组织相比，前列腺癌（PCa）和其他高死亡率的癌症，包括胶质母细胞瘤和小细胞肺癌，严重依赖于非必需氨基酸l -半胱氨酸（L-Cys）及其氧化形式l -胱氨酸（CSSC）的摄取，以促进增殖和存活（由于抗氧化剂的需求增加，在一些肿瘤中，因为它们显示内源性L-Cys合成缺陷）。我们假设，酶介导的血清L-Cys/CSSC池的全身耗损（使用工程化的人类酶，因此可能具有良好的耐受性）构成了一种强大的、全新的前列腺癌治疗方法，作为一种单一疗法，作为一种与现有化疗方式机械协同的药物。这一假设得到了强有力的初步数据的支持，这些数据表明，在PCa同种异体移植模型中（每4天）给药一种原型工程人L-Cys/CSSC消耗酶：(i)导致血清L-Cys/CSSC池几乎完全耗尽；（ii）介导持续和完全停止肿瘤生长，癌细胞经历细胞周期停滞，并伴有氧化应激和自噬增加；（iii）重要的是，治疗超过一个月的耐受性非常好，没有体重减轻或严重毒性。在这些初步观察的基础上，我们提出了一项详细的研究计划，旨在提供临床相关的候选酶治疗，并通过体外和异体移植/异种移植PCa模型进行验证，最终有助于后期临床前开发和IND应用。虽然L-Cys/CSSC消耗可能适用于许多肿瘤的治疗，但我们选择关注PCa首先是因为许多人类PCa肿瘤已知存在L-Cys/CSSC稳态缺陷，其次是因为PCa是美国男性癌症死亡的第二大原因，因此需要有效的无毒治疗。实现这些目标将需要完成以下3个具体目标：Sp.目标1将侧重于L-Cys/CSSC消耗的候选人类酶的工程设计，该酶具有最佳的酶动力学，底物选择性，稳定性

DESCRIPTION (provided by applicant): Extensive studies have revealed that in contrast to normal tissue, prostate carcinomas (PCa) and other high mortality cancers including glioblastomas, and small cell lung carcinomas are critically dependent on the uptake of the non-essential amino acid L-cysteine (L-Cys) and its oxidized form L-cystine (CSSC) for proliferation and survival (due to increased requirements for anti-oxidants and in some tumors because they display defects in endogenous L-Cys synthesis). We hypothesize that enzyme-mediated systemic depletion of the serum L-Cys/CSSC pool (using an engineered human enzyme, and thus likely well tolerated) constitutes a powerful and completely novel cancer therapeutic approach for PCa as a monotherapy and as an agent that is mechanistically synergistic with existing chemotherapeutic modalities. This hypothesis is supported by strong preliminary data demonstrating that the administration (every 4 days) of a prototypical engineered human L- Cys/CSSC depleting enzyme in an allograft model of PCa: (i) results in near complete depletion of the serum L-Cys/CSSC pool; (ii) mediates sustained and complete cessation of tumor growth with cancer cells experiencing cell cycle arrest accompanied by increased oxidative stress and autophagy and (iii) importantly treatment for over a month was very well tolerated with no weight loss or gross toxicities. To build on these preliminary observations we present a detailed research plan that is aimed at delivering a clinically relevant enzyme therapeutic candidate and providing the validation by in vitro and in allograft/xenograft PCa models that will eventually hel support late stage preclinical development and an IND application. While L-Cys/CSSC depletion may be applicable to the treatment of many tumors we elected to focus on PCa first because many human PCA tumors are known to experience defects in L-Cys/CSSC homeostasis and second because effective non-toxic treatments are needed as PCa is the second leading cause of cancer death in American men. Reaching these goals will require the completion of work under 3 Specific Aims: Sp. Aim 1 will focus on the engineering of a candidate human enzyme for L-Cys/CSSC depletion that displays optimal enzyme kinetics, substrate selectivity, stability to deactivation and aggregation and facile production by bioprocessing. The PK and PD of the optimized enzymes as well as any toxic effects upon repeated administration will be evaluated in detail. In Sp. Aim 2 we will seek to understand the global mechanistic/metabolic consequences of L-Cys/CSSC depletion on PCa cells, what biomarkers may predict susceptibility/resistance and to determine which combinations with standard of care chemotherapeutics may provide synergistic/additive effects. Finally, in Sp. Aim 3 we will evaluate the optimized enzyme in clinically relevant orthotopic PCa animal models that represent diverse phenotypes (i.e. p53 status, androgen dependence/independence) and mouse orthotopic PCa allografts such that the efficacy of the drug can be studied in models closely mimicking the actual disease.