Metal Chelate Conjugated Monoclonal Antibodies for Tumor Diagnosis and Therapy

肿瘤相关单克隆抗体（mAb’s）作为恶性肿瘤细胞毒性药物的选择性载体是一种治疗药物。这一假设在动物模型系统中进行了测试，其中单克隆抗体针对与人类疾病相关的抗原。所使用的细胞杀伤剂是粒子发射放射性核素。在适当验证的小鼠肿瘤异种移植模型系统中评估其相对疗效。选择用于研究的放射性核素跨越了放射性核素性质的范围，允许测定发射能量、半衰期和发射类型的影响。目前的研究重点是对α粒子发射放射性核素Pb-212进行广泛的临床前研究，对Bi-213的兴趣减少，并充分激活α粒子发射物At-211的平行研究。正在进行的合作临床试验使用第二代双功能螯合剂1bm - dtpa（又名MX-DTPA或tixetan）来隔离Y-90， Y-90是一种高能纯放射放射性核素，已在临床应用和商业产品Zevalin中得到广泛应用。请注意，使Zevalin （FDA批准的第一种放射性标记抗体治疗药物）成为可能的化学物质是由化学部门开发的。该部门正在进行和计划进行的几乎所有研究现在都使用第三代双功能螯合剂CHX-A“DTPA”来隔离In-111、Y-90、Bi-213和Lu-177。目前已经开始和正在进行的研究继续验证使用Y-86生产的回旋加速器（由化学部门精制和纯化）在PET成像中使用CHX-A“DTPA”。化学部最近报道了许多PET成像研究，关于Y-86用于靶向HER2和HER1（EGFR）的PET成像，用于卵巢癌、结直肠癌、胰腺癌、前列腺癌等多种疾病的可视化；Y-86靶向HER1(EGFR) PET成像治疗间皮瘤的相关研究已提交发表。作为Y-86用于免疫pet应用的补充，化学部门也有一个活跃的研究领域，即开发新型和优质的双功能螯合剂，用于Zr-89用于免疫pet应用，因为目前的技术既笨重，限制了临床/放射药物的转化，又不稳定，导致释放的Zr-89在体内骨沉积。新型双功能螯合剂和靶向放射治疗的连接剂的临床前评估主要是为了改进偶联化学功能基团的选择和放射性标记的改进。这些改进源于提供用于肽化学的试剂以及适用于放射性镧系元素和α粒子发射放射性核素的特定位点偶联策略。现有双功能螯合剂的新型连接化学已被开发用于肽的使用，并与肽合成仪器一起使用。该部门已建立的制剂正在扩展到肽和其他针对感兴趣受体的小递送载体。这种新颖的化学和其中的发现经常被认为适合该科的其他项目。该科为特定位点的连锁策略（如点击化学和碳水化合物修饰策略）创建了许多新颖的连锁化学试剂。At-211研究已经完全启动，等待回旋加速器的运行状态。该科继续改进这种放射性核素的生产设施。化学部分之前报道了最稳定的At-211连接试剂N-Me-SAPS的验证，以及最近对该试剂的完整再合成，将促进与先前Pb-212研究平行的研究。该科最近增加的新人员将在今年晚些时候加速这个项目的进展，包括进一步改进生产和放射性标签技术。对使用Pb-212治疗弥漫性腹腔内疾病（如卵巢癌或胰腺癌）的高度广泛和集中的临床前研究仍在继续。Bi-213达到了这样一个程度，即成本效益评价加上国家供应不足，实际上迫使终止对这种放射性核素的研究。尽管其疗效显著，但Bi-213在治疗中的全部用途和价值可能永远无法确定。随着FDA批准了一项I期临床试验的IND， Pb-212的开发继续向前推进，该临床试验由于NCI领导层的反应迟钝而被转移到UAB。为支持IND，该科完成了小鼠毒理学实验以及该科开发的许多附加文件、研究和标准操作程序。继续系统地评估Pb-212与特异性单克隆抗体的疗效，使用联合放射标记单克隆抗体，以及它们与化疗药物的联合。假设是单一剂量的单一靶向放射性核素缺乏癌症治疗的合理基础；联合治疗将显著提高治疗效果。在小鼠模型中，单剂量的Pb-212结合临床相关抗体（如曲妥珠单抗和帕尼单抗）可显著提高中位预期寿命。放射标记困难使西妥昔单抗无法进一步研究。Pb-212标记的曲妥珠单抗与吉西他滨联合提供了令人印象深刻的增强治疗效果；多剂量的Pb-212和吉西他滨提供了优化药物组合和计划延长生存期的重要证据。研究表明，Pb-212与紫杉醇联合用药可显著延长患者的生存期，并依赖于给药计划。同样，与卡铂联合也延长了生存期，并且正在进行中。报道了克服抗原异质性的多分子肿瘤靶点放射治疗；联合CC49(Delta)CH2和曲妥珠单抗放射标记Pb-212证明需要经验确定给药顺序以优化治疗效果，而不是依赖于无法预测体内肿瘤环境的体外研究。结果显示Pb-212优于Bi-213的治疗效果。研究确定了细胞水平上损伤反应和修复的生物学机制，以及高let辐射对细胞生物学的遗传调控。Camphausen实验室正在开展研究，评估肿瘤生长环境对基因型的影响。正在与Citrin实验室开展研究，以评估目标辐射与外部光束辐射相结合的影响。研究扩大使用三功能显像剂结合放射性核素成像（SPECT或PET）和近红外染料（光学成像）纳入PEG片段。关于染料抗体偶联物的自聚集和信号猝灭特性的重要发现使大量文献受到质疑。这一进展为创建直接定量的光学-放射性核素双模态分子显像剂提供了对基础化学的实际理解。继续进行合作研究；提供试剂和/或专业知识，以方便所有研究人员迅速进行实验，以充分确定靶向放射治疗的临床影响。为此，该科继续与代谢科、NCI和路德维希研究所保持非常牢固和有效的合作关系，并已将这一活动充分扩展到与UAB的合作关系，将Pb-212转化为其治疗弥弥性卵巢癌的首个临床试验。

Tumor associated monoclonal antibodies (mAb's) are therapeutic agents when used as selective carriers of cytotoxic agents to malignancies. This hypothesis is tested in animal model systems with mAbs directed toward antigens associated with human disease. The cytocidal agents employed are particle emitting radionuclides. The relative efficacy is evaluated in the appropriately validated murine tumor xenograft model system. The radionuclides chosen for study span the range of radionuclidic properties available permitting an assay of the effects of emission energy, half-life, and type of emission. Current research focuses on performing extensive pre-clinical studies with the alpha-particle emitting radionuclide Pb-212, with decreased interest in Bi-213, and full activation of parallel studies with the alpha emitter, At-211. Ongoing collaborative clinical trials employ the second generation bifunctional chelating agent 1B4M-DTPA (aka MX-DTPA or tiuxetan) for sequestering Y-90, a high energy pure beta emitting radionuclide well established in clinical applications and in the commercial product, Zevalin. Note that the chemistry that makes Zevalin, the 1st FDA approved radiolabeled antibody therapeutic, possible was developed by the Chemistry Section. Nearly all of those studies ongoing and planned by the Section now employ the 3rd generation bifunctional chelating agent, CHX-A'' DTPA for sequestering In-111, Y-90, Bi-213, and Lu-177. Current studies initiated and ongoing continue to validate use of CHX-A'' DTPA in PET imaging with the cyclotron produced (refined and purified by the Chemistry Section) Y-86. There have been a number of PET imaging studies recently reported by the Chemistry Section regarding the application of Y-86 for PET imaging targeting HER2 and HER1(EGFR) for visualizing a variety of diseases such ovarian, colorectal, pancreatic, prostate cancer; related studies on Y-86 for PET imaging targeting HER1(EGFR) for imaging mesothelioma has been submitted for publication. Complementary to the development of Y-86 for immunoPET applications, the Chemistry Section also has an active area of study on development of novel and superior bifunctional chelating agents for use with Zr-89 for immunoPET applications as the current technology is both cumbersome, limiting clinical/radiopharmacy translation, and not stable in vivo leading to bone deposition of the freed Zr-89 in vivo. Pre-clinical evaluation of novel bifunctional chelating agents and linkers for targeted radiotherapy with isotopes of interest continues primarily to refine conjugation chemistry functional group options and radiolabeling improvements. These refinements stem from the provision of agents for peptide chemistry as well as for site-specific conjugation strategies amenable for use with both radio-lanthanides and alpha-particle emitting radionuclides. Novel linking chemistry for extant bifunctional chelating agents has been developed for peptide usage and in use with peptide synthesizer instrumentation. The established agents of the Section are being extended to peptides and other small delivery vectors targeting receptors of interest. This novel chemistry and discoveries therein are frequently found to be appropriate to the Section's other project. The Section has created a number of novel linkage chemistry agents for site-specific linkage strategies such as click chemistry and carbohydrate modification strategies. At-211 studies have been fully activated pending operation status of the cyclotron. The Section continues to upgrade the production facilities for this radionuclide. The Chemistry section previously reported on validation of the most stable At-211 linker reagent, N-Me-SAPS, and a recent entire re-synthesis of the agent will facilitate studies parallel to the prior Pb-212 studies. The recent addition of new personnel to the Section will accelerate progress on this project later this year incorporating additional production and radiolabeling technology refinements. The highly extensive and focused pre-clinical investigation into the use of Pb-212 continues for the treatment of disseminated intraperitoneal disease, e.g., from either ovarian or pancreatic cancer. Bi-213 reached a point whereby evaluation of cost-effectiveness combined with failed national availability effectively forced termination of study of this radionuclide. Despite its significant efficacy, the full range of use and value of Bi-213 for therapy will probably never be defined. Development of Pb-212 continues to move forward with FDA approval of an IND for a phase I clinical trial that was relocated to UAB due to unresponsive leadership within the NCI. Murine toxicology experiments were completed by the Section in support of the IND along with numerous additional documents, studies, and SOPs developed by the Section. Evaluation of the efficacy of Pb-212 with specific mAbs, use of combined radiolabeled mAbs, and their combinations with chemotherapeutics continues with systematically. The hypothesis is that single doses of a single, targeted radionuclide lacks a rational basis for cancer therapy; combined modality therapies will achieve significant therapeutic enhancements. Substantial increases in median life expectancy in murine models result with single doses of Pb-212 conjugated to clinically relevant antibodies, e.g., trastuzumab and panitumumab. Radiolabeling difficulties eliminated cetuximab from further study. Pb-212 labeled trastuzumab in combination with gemcitabine provided impressive enhanced therapeutic efficacy; multi-dosing of Pb-212 and gemcitabine provided significant evidence that optimization of drug combination and scheduling extends survival. Studies combining administration of Pb-212 with paclitaxel resulted in significant extension of survival with a dependence on administration scheduling. Similarly, combination with carboplatin also extended survival and is ongoing. Delivery of radiation to multiple molecular tumor targets overcoming antigen heterogeneity was reported; combining, CC49(Delta)CH2 and trastuzumab radiolabeled with Pb-212 demonstrated the requirement for empirical determination of administration order to optimize therapeutic efficacy vs. reliance on in vitro studies that fail to predict in vivo tumor environments. Results have indicated superior therapeutic response to Pb-212 vs. Bi-213. Studies define the biological mechanisms at the cellular level of both damage response and repair as well as genetic regulation of the cell biology in response to high-LET radiation are ongoing by the Section. Studies with the Camphausen lab to evaluate tumor growth environment impact on genotype are being initiated. Studies with the Citrin lab are being initiated to assess impact of targeted radiation combined with external beam radiation. Studies to expand use trifunctional imaging agents combining radionuclidic imaging (SPECT or PET) and NIR dye (Optical imaging) incorporated a PEG moiety. Critical discoveries were made regarding self-aggregation and signal quenching properties of dye-antibody conjugates putting a significant body of literature in doubt. This advance provides actual understanding of fundamental chemistry for creation of directly quantitative Optical-radionuclidic dual modality molecular imaging agents. Collaborative studies continue to be executed; reagents and/or expertise are supplied to facilitate all researchers to expeditiously perform experiments required to fully define the clinical impact of targeted radiation therapy. To this end, the Section continues to enjoy very strong and potent collaborative relationships with the Metabolism Branch, NCI and with the Ludwig Institute, and has fully extended this activity to a collaborative relationship with UAB to translate Pb-212 into its first clinical trial for treatment of disseminated ovarian cancer.