Development of Isotopically Labeled Glycoproteins for use as Internal Standards

描述（由申请人提供）：准确定量附着在糖蛋白上的聚糖链的能力具有广泛的意义。过去40年的大量研究表明，异常糖基化发生在几乎所有类型的人类癌症中，并证明了在诊断或预后方式中使用聚糖标记物的潜力。重组蛋白治疗的糖基化也被认为具有深远的影响，其中一个较著名的例子是糖工程导致红细胞生成素（EPO）的血清半衰期增加。因此，糖蛋白聚糖的定量从发现新的诊断/预后标志物到开发各种治疗剂都起着重要的作用。目前进行定量糖组学的一个障碍是缺乏广泛可用的标准糖蛋白和同位素标记试剂，以实现准确的定量。人类蛋白质组组织（HUPO）和生物分子资源设施协会（ABRF）进行的实验室间研究强调了多糖定量的问题。这两项研究都表明，在参与的实验室中，对中低水平聚糖的分析误差大于百分之几百。无法准确定量低水平的聚糖尤其令人担忧，因为低丰度的聚糖通常具有最大的影响，正如治疗性人静脉注射免疫球蛋白G （IVIg）所见。本提案的重点是开发一个具有同位素标记聚糖的特征良好的标准糖蛋白，以便在相对水平和潜在的绝对水平上对n链聚糖进行准确，稳健和可重复性的分析。选择单克隆抗体（mAb）是因为这些作为治疗剂的广泛使用，以及各种监管机构对多糖定量的需要。在这里，已知数量的同位素标记单抗（i-mAb）可以直接添加到治疗性单抗制剂中，通过包括质谱法在内的任何标准程序进行分析，并通过比较天然离子与同位素标记离子的比例来提供聚糖定量。由于多糖结构的相似性，i-mAb有望成为所有治疗性mab的优秀内标

DESCRIPTION (provided by applicant): The ability to accurately quantitate the glycan chains attached to glycoproteins has wide-ranging implications. Numerous studies over the past 40 years have demonstrated that abnormal glycosylation occurs in virtually all types of human cancers, and demonstrate the potential of using glycan markers in either a diagnostic or a prognostic manner. The glycosylation on recombinant protein therapeutics is also known to have profound effects, with one of the better known examples being the increased serum half-life of erythropoietin (EPO) resulting from glycoengineering. Hence, the quantification of glycoprotein glycans play important roles from the discovery of new diagnostic/prognostic markers to the development of various therapeutic agents. A current impediment for performing quantitative glycomics is the shortage of widely available standard glycoproteins and isotopically labeled reagents to enable accurate quantitation. The issue with glycan quantitation was highlighted by inter-laboratory studies conducted by the Human Proteome Organization (HUPO) and the Association of Biomolecular Resource Facilities (ABRF). Both of these studies demonstrated errors greater than several hundred percent in the analysis of mid-to-low level glycans were compared across participating laboratories. The inability to accurately quantitate low level glycans is particularly worrisome since it is often glycans of low abundance that have the largest impact, as is seen with the therapeutic human intravenous immunoglobulin G (IVIg). The focus of this proposal is to develop a well-characterized standard glycoprotein with isotopically labeled glycans to enable the accurate, robust, and reproducible analysis of N-linked glycans at the relative and potentially absolute level. A monoclonal antibody (mAb) was selected because of the widespread use of these as therapeutic agents coupled with the need for glycan quantification by various regulatory agencies. Here, a known quantity of the isotopically labeled mAb (i-mAb) can be added directly to therapeutic mAb preparation, analyzed by any standard procedure that includes mass spectrometry, and glycan quantitation will be provided by comparing the ratios of the native to isotopically labeled ions. i-mAb is expected to be an excellent internal standard for all therapeutic mAbs because of the similarity in glycan structures and in the amino acid sequence flanking the glycosylation site that is found on most mAb-based therapeutics. Since i-mAb can be added directly to the sample before any processing and is virtually identical to the analyte mAb, this approach is expected to be capable of compensating for a wide range of systematic errors, such as differential losses during sample handling, matrix effects, operator errors/inequalities, instrumental drift/response, etc. It is further anticipated hat i-mAb will enable researchers at different locations to obtain comparable results despite using different instruments, which is not possible with current methodology.