BioMarin Pharmaceutical Inc., 105 Digital Drive, Novato, CA 94949, USA.
BioMarin Pharmaceutical Inc., 105 Digital Drive, Novato, CA 94949, USA.
J Immunol Methods. 2019 May;468:20-28. doi: 10.1016/j.jim.2019.03.004. Epub 2019 Mar 14.
Pegvaliase is an enzyme substitution therapy developed to lower blood phenylalanine (Phe) in adults with phenylketonuria (PKU). In phase 3 clinical studies, pegvaliase substantially reduced mean blood Phe in adult subjects with PKU. The most common type of adverse event observed in the pegvaliase clinical program was hypersensitivity adverse events (HAEs), which included occurrences of arthralgia, rash, and pruritis. The most clinically relevant HAEs were acute systemic hypersensitivity reactions consistent with anaphylaxis observed in 4.6% of phase 3 patients. HAEs were more commonly observed around the time of high circulating immune complex (CIC) levels and complement activation, and the majority of subjects that experienced acute systemic hypersensitivity events were able to continue treatment, which is atypical for a classical IgE-mediated anaphylactic event, but common for type III hypersensitivity reactions. To investigate the alternative mechanism of type III hypersensitivity, serum samples collected shortly after hypersensitivity events (in phase 2 and 3 studies) were tested for anti-pegvaliase IgE using custom radioallergosorbent test and/or ImmunoCAP® (ThermoFisher Scientific, Waltham, MA) assay methods. All subjects with acute systemic hypersensitivity that were tested for anti-pegvaliase IgE at or near the time of event with one or both assays tested negative for IgE. As presented here, an investigation using selected study samples with high anti-drug antibody (ADA) titers demonstrated that presence of IgM and/or IgG ADA can interfere with measurement of a human anti-pegvaliase IgE surrogate positive control. A depletion method was therefore developed using protein A- and G-conjugated Sepharose to remove interfering IgG and IgM in serum samples to low levels (<45 mg/dL) before IgE testing. A final 2× concentration step brought the IgE concentration in the depleted sample to approximately the same level of the starting serum. Phase 3 study samples with sufficient volume remaining that previously tested negative for anti-pegvaliase IgE were re-tested after depletion of IgG and IgM. All samples again tested negative, confirming the original test results. Taken together, the clinical presentation, temporal association of HAEs with CIC levels and complement activation, and lack of anti-pegvaliase IgE suggest pegvaliase-associated acute systemic hypersensitivity events were not IgE-mediated. Furthermore, we describe a universal method that is broadly applicable to enzyme therapies for detection of low concentrations of drug-specific IgE in the presence of high titer anti-drug antibodies of different isotypes.
培维利塞是一种酶替代疗法，用于降低苯丙酮尿症（PKU）成人患者的血液苯丙氨酸（Phe）水平。在 3 期临床研究中，培维利塞显著降低了 PKU 成年患者的平均血液 Phe 水平。培维利塞临床研究项目中观察到的最常见的不良事件类型是超敏反应不良事件（HAE），包括关节痛、皮疹和瘙痒的发生。在 3 期患者中，最具临床相关性的 HAE 是与过敏反应一致的急性全身性超敏反应，发生率为 4.6%。HAE 更常见于高循环免疫复合物（CIC）水平和补体激活时，大多数经历急性全身性超敏反应事件的受试者能够继续治疗，这与典型的 IgE 介导的过敏反应不同，但与 III 型超敏反应常见。为了研究 III 型超敏反应的替代机制，在 2 期和 3 期研究中，在 HAE 发生后不久收集的血清样本使用定制放射过敏原吸附试验和/或 ImmunoCAP®（ThermoFisher Scientific，Waltham，MA）检测方法检测抗培维利塞 IgE。所有接受急性全身性超敏反应检测的患者，在事件发生时或附近使用一种或两种检测方法进行抗培维利塞 IgE 检测，结果均为 IgE 阴性。如本文所述，使用具有高抗药物抗体（ADA）滴度的选定研究样本进行的一项调查表明，存在 IgM 和/或 IgG ADA 会干扰人抗培维利塞 IgE 替代阳性对照的测量。因此，开发了一种使用蛋白 A 和 G 偶联琼脂糖的耗尽方法，将血清样本中的干扰 IgG 和 IgM 降低到低水平（<45mg/dL），然后再进行 IgE 检测。在浓缩步骤中，将耗尽样本中的 IgE 浓度浓缩至与起始血清大致相同的水平。先前用抗培维利塞 IgE 检测结果为阴性的 3 期研究样本，在耗尽 IgG 和 IgM 后再次进行检测。所有样本再次检测均为阴性，证实了最初的检测结果。综上所述，HAE 的临床特征、与 CIC 水平和补体激活的时间关联以及缺乏抗培维利塞 IgE 提示培维利塞相关的急性全身性超敏反应事件不是 IgE 介导的。此外，我们描述了一种通用方法，该方法广泛适用于检测不同同种型的高滴度抗药物抗体存在时的低浓度药物特异性 IgE。
