Applications of a planar electrochemiluminescence platform to support regulated studies of macromolecules: Benefits and limitations in assay range

Retrospective Analysis of Bioanalytical Method Validation Approaches in Biosimilar Biological Product Development

Development and validation of a bioanalytical method for biosimilar biological product development (BPD) can be challenging. It requires the development of a bioanalytical method that reliably and accurately measures both proposed biosimilar and reference products in a biological matrix. This survey summarizes the current state of bioanalysis in BPD. Bioanalytical data from 28 biosimilar biologic license applications submitted to U.S. Food and Drug Administration (FDA) up to December 2018 were analyzed. The aim of the analysis was to provide (i) a summary of the bioanalytical landscape for BPD, (ii) a cumulative review of bioanalytical method validation approaches to aid in understanding how a specific method was selected, and (iii) a summary of data regarding bioanalytical bias differences between products. Results show diversity of the bioanalytical approaches used, as well as the observed differences in bioanalytical bias. Our findings highlight the need for understanding the critical aspects of BPD bioanalysis and clarifying BPD bioanalytical best practices, which could help ensure consistent method validation approaches in the BPD community.

A First Tetraplex Assay for the Simultaneous Quantification of Total α-Synuclein, Tau, β-Amyloid42 and DJ-1 in Human Cerebrospinal Fluid

The quantification of four distinct proteins (α-synuclein, β-amyloid_1-42, DJ-1, and total tau) in cerebrospinal fluid (CSF) has been proposed as a laboratory-based platform for the diagnosis of Parkinson’s disease (PD) and Alzheimer’s disease (AD). While there is some clinical utility in measuring these markers individually, their usage in routine clinical testing remains challenging, in part due to substantial overlap of concentrations between healthy controls and diseased subjects. In contrast, measurement of different analytes in a single sample from individual patients in parallel appears to considerably improve the accuracy of AD or PD diagnosis. Here, we report the development and initial characterization of a first, electrochemiluminescence-based multiplex immunoassay for the simultaneous quantification of all four proteins (‘tetraplex’) in as little as 50 μl of CSF. In analytical performance experiments, we assessed its sensitivity, spike-recovery rate, parallelism and dilution linearity as well as the intra- and inter-assay variability. Using our in-house calibrators, we recorded a lower limit of detection for α-synuclein, β-amyloid₄₂, DJ-1, and t-tau of 1.95, 1.24, 5.63, and 4.05 pg/ml, respectively. The corresponding, linear concentration range covered >3 orders of magnitude. In diluted CSF samples (up to 1:4), spike-recovery rates ranged from a low of 55% for β-amyloid₄₂ to a high of 98% for DJ-1. Hillslopes ranged from 1.03 to 1.30, and inter-assay variability demonstrated very high reproducibility. Our newly established tetraplex assay represents a significant technical advance for fluid-based biomarker studies in neurodegenerative disorders allowing the simultaneous measurement of four pivotal makers in single CSF specimens. It provides exceptional sensitivity, accuracy and speed.

In Silico Evaluation of the Potential Impact of Bioanalytical Bias Difference between Two Therapeutic Protein Formulations for Pharmacokinetic Assessment in a Biocomparability Study

Formulation changes at later stages of biotherapeutics development require biocomparability (BC) assessment. Using simulation, this study aims to determine the potential effect of bias difference observed between the two formulations after spiking into serum in passing or failing of a critical BC study. An ELISA method with 20% total error was used to assess any bias differences between a reference (RF) and test formulations (TF) in serum. During bioanalytical comparison of these formulations, a 9% difference in bias was observed between the two formulations in sera. To determine acceptable level of bias difference between the RF and TF bioanalytically, two in silico simulations were performed. The in silico analysis showed that the likelihood of the study meeting the BC criteria was >90% when the bias difference between RF and TF in serum was 9% and the number of subjects was ≥20 per treatment arm. An additional simulation showed that when the bias difference was increased to 13% and the number of subjects was <40, the likelihood of meeting the BC criteria decreased to 80%. The result from in silico analysis allowed the bioanalytical laboratory to proceed with sample analysis using a single calibrator and quality controls made from the reference formulation. This modeling approach can be applied to other BC studies with similar situations.

Validation of a microfluidic platform to measure total therapeutic antibodies and incurred sample reanalysis performance

BACKGROUND

A microfluidic platform-based assay was validated to measure a humanized or fully human IgG in rat serum samples.

MATERIALS & METHODS

The cumulative assessment for accuracy and precision was performed with three accuracy and precision runs.

RESULTS

The inter-assay accuracy (mean %bias) ranged from -4.3 to 3.8%, and inter-batch %CV ranged from 5.0 to 9.2%. The method acceptance criterion was determined as 15% total error. The assay dynamic range was 50 to 10000 ng/ml. Incurred sample reanalysis passed with 95% of samples meeting incurred sample reanalysis acceptance criteria. Potential carryover effect was not observed.

CONCLUSION

This study demonstrated the need for evaluating additional platform-specific processes when new technologies are employed to ensure the reproducibility of a successfully validated microfluidic platform method.

PK-PD modeling of protein drugs: implications in assay development

Pharmacokinetic-pharmacodynamic (PK-PD) modeling is an integral part of the preclinical and clinical development of protein drugs. Bioanalytical data from appropriately selected and well-characterized PK and PD biomarker assays can be incorporated into mechanistic PK-PD models and allow a quantitative relationship between protein drug exposure, target modulation, and biochemical, physiological and pathophysiological effects to be established. The selection of PD biomarkers that assess target engagement and modulation in the extracellular milieu and downstream cellular effects can provide proof-of-mechanism and define the magnitude and duration of target modulation following drug administration. The PK-PD data can provide an important link between magnitude of target modulation and clinical efficacy and safety outcomes, and guide the selection of doses and dosing schedules for clinical trials. In this article, approaches to the selection and development of fit-for-purpose, PK and PD assays for protein drugs are reviewed, and the applications of the assay results in PK-PD models are discussed.

Key amino acid residues of ankyrin-sensitive phosphatidylethanolamine/phosphatidylcholine-lipid binding site of βI-spectrin

It was shown previously that an ankyrin-sensitive, phosphatidylethanolamine/phosphatidylcholine (PE/PC) binding site maps to the N-terminal part of the ankyrin-binding domain of β-spectrin (ankBDn). Here we have identified the amino acid residues within this domain which are responsible for recognizing monolayers and bilayers composed of PE/PC mixtures. In vitro binding studies revealed that a quadruple mutant with substituted hydrophobic residues W1771, L1775, M1778 and W1779 not only failed to effectively bind PE/PC, but its residual PE/PC-binding activity was insensitive to inhibition with ankyrin. Structure prediction and analysis, supported by in vitro experiments, suggests that “opening” of the coiled-coil structure underlies the mechanism of this interaction. Experiments on red blood cells and HeLa cells supported the conclusions derived from the model and in vitro lipid-protein interaction results, and showed the potential physiological role of this binding. We postulate that direct interactions between spectrin ankBDn and PE-rich domains play an important role in stabilizing the structure of the spectrin-based membrane skeleton.

Assessment of incurred sample reanalysis for macromolecules to evaluate bioanalytical method robustness: effects from imprecision

Incurred sample reanalysis (ISR) is recommended by regulatory agencies to demonstrate reproducibility of validated methods and provide confidence that methods used in pharmacokinetic and toxicokinetic assessments give reproducible results. For macromolecules to pass ISR, regulatory recommendations require that two thirds of ISR samples be within 30% of the average of original and reanalyzed values. A modified Bland-Altman (mBA) analysis was used to evaluate whether total error (TE), the sum of precision and accuracy, was predictive of a method's passing ISR and to identify potential contributing parameters for ISR success. Simulated studies determined minimum precision requirements for methods to have successful ISR and evaluated the relationship between precision and the probability of a method's passing ISR acceptance criteria. The present analysis evaluated ISRs conducted for 37 studies involving ligand-binding assays (LBAs), with TEs ranging from 15% to 30%. An mBA approach was used to assess accuracy and precision of ISR, each with a threshold of 30%. All ISR studies met current regulatory criteria; using mBA, all studies met the accuracy threshold of 30% or less, but two studies (5%) failed to meet the 30% precision threshold. Simulation results showed that when an LBA has ≤15% imprecision, the ISR criteria for both the regulatory recommendation and mBA would be met in 99.9% of studies. Approximately 71% of samples are expected to be within 1.5 times the method imprecision. Therefore, precision appears to be a critical parameter in LBA reproducibility and may also be useful in identifying methods that have difficulty passing ISR.