2015年2月21日讯 /生物谷BIOON/ --如果要问2014年生物医药行业取得的重大突破有哪些，那么CAR-T疗法必定榜上有名。这种免疫疗法首先是通过分离患者体内的T细胞并在体外进行特定肿瘤抗体的修饰，经过扩增后再回输至患者体内。这种经过修饰的T细胞能够特异、高效的识别肿瘤细胞，从而达到在治疗肿瘤的同时又避免对正常组织的损伤。此前的CAR-T疗法一般都是以治疗白血病等肿瘤为主要靶点。
最近来自宾州大学和诺华公司的研究人员进行了一系列的动物实验证实了CAR-T疗法有希望用于治疗恶性胶质瘤。这种恶性脑瘤一直都是肿瘤疗法开发中的一大难点。每年美国有约2万2千人被诊断为患有这种癌症。由于发病部位在脑部，许多患者都无法及早诊断。目前治疗癌症的一些标准疗法都难以起到良好疗效，大多数患者确诊后生存期不到18个月。
根据参与这一项目的Marcela Maus介绍，CAR-T疗法治疗恶性胶质瘤的一个困难就是如何寻找到一个合适的靶点。经过严格筛选，科学家们最终选择了一种名为EGFRvIII的表皮生长因子受体作为靶点。研究显示，在30%的恶性胶质瘤患者体内，肿瘤细胞表面都表达这种受体蛋白的突变体。更重要的是，表达这种突变体基因的肿瘤恶性程度更高。
基于这一原理，研究人员分离纯化了针对EGFRvIII突变体的抗体片段，并将其与T细胞进行偶联。科学家通过细胞实验和小鼠实验确定了这种抗体不会对正常的EGFRvIII产生作用以验证其安全性。随后研究人员在恶性胶质瘤小鼠模型上检测了CAR-T细胞疗法的抗肿瘤作用。通过磁共振成像等手段，科学家发现小鼠脑部的肿瘤出现萎缩的现象，当这种疗法和化疗药物替莫唑胺联用时，一些小鼠脑部的肿瘤甚至消失。大感振奋的研究人员随后根据这些数据设计出了一个小型的临床一期研究方案。科学家计划招募12名恶性胶质瘤患者，其中六人是接受过其他疗法治疗但未能收获理想疗效的患者，另外六人是刚刚确诊为恶性胶质瘤的患者。
而此次研究的赞助者为国际著名制药巨头诺华公司。CAR-T疗法的兴起使得宾州大学和诺华喜结连理。双方围绕着肿瘤免疫疗法达成了一系列长期的研究合作协议。也正由于这种产学研优势互补，使得诺华公司自免疫疗法兴起以来，就一直走在市场的最前列。
详细英文报道：
Preclinical Study Results Pave the Way for Newly Opened Clinical Trial of Immune Cells Engineered to Attack Protein Found on Tumors in 30 Percent of Patients with Glioblastoma
PHILADELPHIA - Immune cells engineered to seek out and attack a type of deadly brain cancer were found to be both safe and effective at controlling tumor growth in mice that were treated with these modified cells, according to a study published in Science Translational Medicine by a team from the Perelman School of Medicine at the University of Pennsylvania and the Novartis Institutes for BioMedical Research. The results paved the way for a newly opened clinical trial for glioblastoma patients at Penn.
"A series of Penn trials that began in 2010 have found that engineered T cells have an effect in treating some blood cancers, but expanding this approach into solid tumors has posed challenges," said the study's senior author, Marcela Maus, MD, PhD, an assistant professor of Hematology/Oncology in Penn's Abramson Cancer Center. "A challenging aspect of applying engineered T cell technology is finding the best targets that are found on tumors but not normal tissues. This is the key to making this kind of T cell therapy both effective and safe."
The new preclinical study, conducted in collaboration with Hideho Okada, MD, PhD and his colleagues at the University of Pittsburgh, details the design and use of T cells engineered to express a chimeric antigen receptor (CAR) that targets a mutation in the epidermal growth factor receptor protein called EGFRvIII, which is found on about 30 percent of glioblastoma patients' tumor cells. More than 22,000 Americans are diagnosed with glioblastoma each year. Patients whose tumors express the EGFRvIII mutation tend to have more aggressive glioblastomas. Their tumors are less likely to respond favorably to standard therapies and more likely to recur following those treatments.
"Patients with this type of brain cancer have a very poor prognosis. Many survive less than 18 months following their diagnosis," said M. Sean Grady, MD, the Charles Harrison Frazier Professor and chair of the department of Neurosurgery. "We've brought together experts in an array of fields to develop an innovative personalized immunotherapy for certain brain cancers."
The new trial is led by Donald M. O'Rourke, MD, an associate professor of Neurosurgery, who oversees an interdisciplinary collaboration of neurosurgeons, neuro-oncologists, neuropathologists, immunologists, and transfusion medicine experts.
Maus describes the genesis of the new results as a "tour de force," in terms of the range of experiments performed to characterize the EGFRvIII CAR T cell. First, the team developed and tested multiple antibodies, or what immunologists call single-chain variable fragments (scFv), which bind to cells expressing EGFRvIII on their surface. The scFvs recognizing the mutated EGFRvIII protein must be rigorously tested to confirm that they do not also bind to normal, non-mutated EGFR proteins, which are widely expressed on cells in the human body.
The researchers then generated a panel of humanized scFvs and tested their specificity and function in CAR modified T cells. (Humanized scFvs are molecularly changed from their origins in non-human species to increase their similarity to human antibodies.) Out of the panel of humanized scFvs that were tested, the researchers selected one scFv to explore further based on its binding selectivity for EGFRvIII over normal non-mutated EGFR. They also evaluated the EGFRvIII CAR T cells in an assay utilizing normal EGFR-expressing skin cells in mice grafted with human skin. They found that the engineered EGFRvIII CAR T cells did not attack cells with normal EGFR in this model.
The lead scFv was then tested for its anti-cancer efficacy. Using human tumor cells, the scientific team determined that the EGFRvIII CAR T cells could multiply and secrete cytokines in response to tumor cells bearing the EGFRvIII protein. Importantly, the researchers found that the EGFRvIII CAR T cells controlled tumor growth in several mouse models of glioblastoma, as measured by magnetic resonance imaging (MRI) and luminescence of tumors in the mouse brains. In the mouse model, the EGFRvIII CAR T cells caused tumor shrinkage when measured by MRI and were also effective in eliminating tumors when administered in combination with temozolomide chemotherapy that is used to treat patients with glioblastoma.
On the basis of these preclinical results, the investigators designed a phase 1 clinical study of CAR T cells transduced with humanized scFv directed to EGFRvIII for both newly diagnosed and recurrent glioblastoma patients carrying the EGFRvIII mutation. "There are unique aspects about the immune system that we're now able to utilize to study a completely new type of therapy," said O'Rourke.
The investigational approach begins when some of each patient's T cells are removed via an apheresis process similar to dialysis, the cells are engineered using a viral vector that programs them to find cancer cells that express EGFRvIII. Then, the patient's own engineered cells are infused back into their body, where a signaling domain built into the CAR promotes proliferation of these "hunter" T-cells. In contrast to certain T cell therapies that also target some healthy cells, EGFRvIII is believed to be found only on tumor tissue, which the study's leaders hope will minimize side effects.
The new trial will enroll 12 adult patients whose tumors express EGFRvIII, in two groups: One arm of 6 patients whose cancers have returned after receiving other therapies, and one arm of 6 patients who are newly diagnosed with the disease and still have 1 cm or more of tumor tissue remaining after undergoing surgery to remove it.
The clinical trial is sponsored by Novartis. In 2012, the University of Pennsylvania and Novartis announced an exclusive global research and licensing agreement to further study and commercialize novel cellular immunotherapies using CAR technologies. The STM study is the first pre-clinical paper developed within the Penn-Novartis alliance, with Penn and Novartis scientists working collaboratively. Ongoing clinical trials evaluating a different type of Penn-developed CAR therapy known as CTL019 have yielded promising results among some patients with certain blood cancers. In July 2014, the FDA granted CTL019 its Breakthrough Therapy designation for the treatment of relapsed and refractory acute lymphoblastic leukemia in both children and adults. For more information about the glioblastoma trial, visit clinicaltrials.gov.
This STM study was supported by funding from the National Institutes of Health (DP2CA174502), the National Cancer Institute (K08-166039), an American Society of Clinical Oncology Conquer Cancer Foundation Young Investigator Award, and the Novartis Institutes for BioMedical Research as part of an alliance with the University of Pennsylvania.