Growth Factor Imaging

生长因子受体在肿瘤生长和发展中的作用的认识对癌症治疗具有广泛的意义。不仅开发了阻断抗体，而且还开发了下游小分子抑制剂。这两种药物已经对几种主要癌症的治疗产生了影响。不管受体成像，成像代表了一个潜在的重要研究途径。靶向受体的显像剂的潜在用途包括更精确的组织采样、药物试验的患者选择、针对受体或影响受体表达的下游客户的治疗方法的监测、开发用于递送特定药物治疗的免疫偶联物以及将治疗同位素或光敏剂附着在抗体上的放射免疫治疗/光免疫治疗。我们正在进行各种临床前和临床研究，以调查这类显像剂的潜在作用。临床前研究单个抗体有局限性，因为肿瘤可能表达受体的多克隆分布。例如，肿瘤的一部分可能表达HER2，而另一部分可能表达MET、HER1或间皮素。我们已经探索了一种用于肿瘤诊断和表征的标记鸡尾酒抗体的想法。光学标记单克隆抗体用于诊断的潜在用途正在通过混合抗体组合和注射鸡尾酒进行探索。将光学标记的抗体鸡尾酒（曲妥珠单抗-抗HER2，西妥昔单抗，抗HER2和Declizimab -抗il - 2）注射到表达不同抗原的肿瘤小鼠中。光学标记的抗体，每个都用一个独特波长的荧光团标记，附着在各自的癌细胞上，打开了进行体内免疫组织化学的可能性。这可能会发现在手术或内镜检查期间改善肿瘤取样的特殊应用。然而，另一个潜在的用途是使用各种前药策略，通过不同的单克隆抗体载体递送前药的每个部分。光学成像证明了这一概念，可以证明体内两种或多种单克隆抗体的共定位和内化。光学成像相对于放射性核素成像的一个优点是光学成像本质上是多色的，允许每个试剂单独标记。这允许对肿瘤的药物作用进行实时药效学分析（至少表面上可见），并且对药物发现和药物测试具有潜在的重要性(2)。最近，我们发现当抗体附着在一种独特的光荧光上时，一种强度的近红外光可以用于诊断，但通过增加强度，实际上可以治疗肿瘤。这个过程被称为光免疫疗法，对于治疗某些可以用近红外光接近的癌症有很大的希望。与Dr. Brechbiels实验室合作，我们正在测试PET和SPECT标记的单克隆抗体，并对曲妥珠单抗、西妥昔单抗和帕尼单抗进行了测试(3)。目前尚不清楚是SPECT还是PET成像更可取，将进行一项使用小动物成像程序PET-SPECT- ct设备的比较试验。最近，这项工作已经在Bethesda使用分子成像程序中的微spect和微pet相机实现。我们还探索了比抗体小得多的放射性标记词缀的使用。在肺转移小鼠模型中，HER2结合修饰物比FDG PET检测转移更敏感。在MET受体上已经做了大量的工作，我们已经标记了该受体的外部和内部结构域。我们正在开发这种药物的F18标记版本，供人使用。在过去的两年里，我们还资助了一位美国国立卫生研究院牛津大学的研究生Ambika Bumb，她设计了一种具有抗体靶向的纳米颗粒。纳米颗粒由氧化铁核（用于核磁共振成像）和嵌入C5.5（用于光学成像）的二氧化硅壳组成（最初由a . Bumb NanoTech 07 San Diego，CA， 2007年提出）。在该平台药物上，附着与铟螯合的曲妥珠单抗（用于SPECT成像）。我们打算在几种体内HER2+肿瘤小鼠模型中测试这种纳米颗粒。抗间皮素抗体（Raffit Hassan, Ira Pastan，分子生物学实验室）也被开发出来。这种受体与侵袭性表型有关。我们已经用这种标记抗体在小鼠中进行了临床前研究，并将很快开始临床试验。临床研究我们正在进行几项涉及生长因子受体的研究。最初的临床研究使用111铟曲妥珠单抗治疗乳腺癌患者。该方案测试了过表达或不过表达HER2/neu的乳腺癌患者对曲妥珠单抗（赫赛汀）的摄取。111铟-帕尼米单抗也获得了JDC的初步批准，用于结肠癌和肺癌患者。初步临床前工作已提交给癌症成像项目，以纳入新药申报，并正在编写GMP产品的sop。铟标记间皮素（MORAb009）将很快开始临床试验。细胞增殖是生长因子受体激活的直接结果。我们已经研究了用一种新的用于人类的PET试剂，18f - l -胸苷，一种癌症的增殖标志物来测量增殖的能力。我们已经在各种肿瘤中使用了这种药物并证明了它的效用。这项工作正在淋巴瘤和儿童髓母细胞瘤、神经纤维瘤病和白血病移植后的试验中进行。1. Koyama， Y., Hama， Y., Urano， Y., Nguyen， D. M., Choyke， P. L.和Kobayashi， H.靶向HER2/neu肺转移的光谱荧光分子成像。临床肿瘤学杂志，13(3):2936-2945,2007。2. Hama， Y., Koyama， Y., Choyke， P. L.和Kobayashi， H.双色体内动态对比增强药代动力学成像。[J] .生物医学工程学报，2016,31(2):444 - 444。3. 许辉，白doo， K, Gunn， A. J, Boswell， C. A, Milenic， D. E, Choyke， P. L, Brechbiel， M. W.用于单克隆抗体肿瘤靶向成像的双模态正电子发射断层扫描和荧光显像剂的设计，合成和表征。医学化学杂志，2007。

Imaging of Growth Factor Receptors Background The recognition of the role of growth factor receptors in the growth and progression of tumors has had widespread implications for cancer treatment. Not only have blocking antibodies been developed , but downstream small molecule inhibitors have also been developed. Both drug types have already had impact on the management of several major cancers. Regardless of the receptor imaged, imaging represents a potentially important avenue of research. Potential uses of imaging agents targeting receptors include more accurate sampling of tissue, patient selection for drug trials, monitoring of therapies directed at the receptor or its downstream clients which impact receptor expression, developing immuno-conjugates for delivering specific drug therapy and radioimmunotherapy/photoimmunotherapy in which therapeutic isotopes or photosensitizers are attached to the antibody. We are conducting a variety of pre-clinical and clinical studies to investigate the potential roles of this class of imaging agents. Pre-Clinical Research Individual antibodies have limitations because a tumor may express polyclonal distribution of receptors. For instance, part of the tumor may express HER2 but another part may express MET, HER1 or Mesothelin. We have explored the idea of a labeled cocktail of antibodies for tumor diagnosis and characterization. The potential use of optically labeled monoclonal antibodies for diagnosis is being explored by mixing combinations of antibodies and injecting the cocktail. Cocktails of optically labeled antibodies (Trastuzumab-anti HER2, Cetuximab, anti-HER2, and Declizimab anti-IL2) are injected into mice growing tumors expressing different antigens. The optically labeled antibodies, each labeled with a fluorophore of a unique wavelenth, attach to their respective cancer cells opening the possibility of performing in vivo immunohistochemistry. This may find particular application in improving the sampling of tumors during surgery or during endoscopy. However, another potential use is to use various pro-drug strategies to deliver each part of the pro-drug via different monoclonal antibody vectors. Proof of this concept is provided by optical imaging that can demonstrate the co-localization and internalization of two or more monoclonal antibodies in vivo. An advantage of optical imaging over radionuclide imaging is that optical imaging is inherently polychromatic allowing each agent to be tagged individually. This allows real time pharmacodynamic analysis of drug effects of tumors (visible superficially at least) and is of potential importance to drug discovery and drug testing(2). Recently, we have discovered that when the antibody is attached to a unique photofluor, near infrared light at one intensity could be used for diagnosis but by increasing the intensity the tumor can actually be treated. This process is known as photoimmunotherapy and holds great promise for the treatment of some forms of cancer that can be approached with near infrared light. In collaboration with Dr. Brechbiels lab we are testing PET and SPECT labeled monoclonal antibodies and have performed this with both trastuzumab and cetuximab and panitumimab(3). It is still unclear whether SPECT or PET imaging is preferred and a comparison trial using the Small Animal Imaging Programs PET-SPECT-CT device will be conducted. Recently, this work has been enabled in Bethesda using microSPECT and microPET cameras in the Molecular Imaging Program. We have also explored theuse of radiolabeled affibodies which are considerably smaller than antibodies. HER2 binding affibodies have proven to be more sensitive than FDG PET for detecting metastases in mouse models of lung metastases. Extensive work has been done on MET receptor where we have labeled both the external and internal domains of this receptor. We are developing an F18 labeled version of this agent for human use. Over the past two years we have also sponsored an NIH-Oxford Graduate student, Ambika Bumb, who has designed an implemented a nanoparticle with antibody targeting. The nanoparticle consists of a core of iron oxide (for MRI) with a shell of silica embedded with C5.5 (for optical imaging) (presented originally by A. Bumb NanoTech 07 San Diego,CA, 2007). To this platform agent, trastuzumab, chelated with Indium (for SPECT imaging) is attached. We intend to test this nanoparticle in several in vivo murine models of HER2+ tumors. Anti-Mesothelin antibody (Raffit Hassan, Ira Pastan, Laboratory of Molecular Biology) has also been developed. This receptor is associated with an aggressive phenotype. We have performed preclinical studies in mice with this labeled antibody and will shortly initiate a clinical trial. Clinical Studies We are conducting several studies involving growth factor receptors. The original clinical study used 111Indium trastuzumab in breast cancer patients. This protocols tests the uptake of trastuzumab (Herceptin) in patients with breast cancer who either overexpress or do not overexpress HER2/neu. Preliminary JDC approval was also received for 111Indium-panitumimab to be used in patients with colon and lung cancer. The preliminary pre-clinical work has been submitted to the Cancer Imaging Program for incorporation into an xIND submission and SOPs are being written for a GMP product. Indium labeled mesothelin (MORAb009) will begin clinical trials shortly. Cell proliferation is a direct result of activation of the growth factor receptors. We have investigated the ability to measure proliferation with a novel PET agent for human use, 18 F-L-thymidine, a proliferation marker for cancer. We have been using this agent in a variety of tumors and have demonstrated its utility. This work is ongoing in a trial of lymphoma and pediatric medulloblastoma, neurofibromatosis and leukemia post transplant. 1. Koyama, Y., Hama, Y., Urano, Y., Nguyen, D. M., Choyke, P. L., and Kobayashi, H. Spectral fluorescence molecular imaging of lung metastases targeting HER2/neu. Clin Cancer Res, 13: 2936-2945, 2007. 2. Hama, Y., Koyama, Y., Choyke, P. L., and Kobayashi, H. Two-color in vivo dynamic contrast-enhanced pharmacokinetic imaging. J Biomed Opt, 12: 034016, 2007. 3. Xu, H., Baidoo, K., Gunn, A. J., Boswell, C. A., Milenic, D. E., Choyke, P. L., and Brechbiel, M. W. Design, Synthesis, and Characterization of a Dual Modality Positron Emission Tomography and Fluorescence Imaging Agent for Monoclonal Antibody Tumor-Targeted Imaging. J Med Chem, 2007.