A risk-based bioanalytical strategy for the assessment of antibody immune responses against biological drugs

Efficacy, drug sustainability, and safety of ustekinumab treatment in Crohn's disease patients over three years

Long-term data on ustekinumab in real-life Crohn's disease patients are still missing, though randomized controlled trials demonstrated it as a favorable therapeutic option. We aimed to evaluate ustekinumab's clinical efficacy, drug sustainability, and safety in a prospective, nationwide, multicenter Crohn's disease patient cohort with a three-year follow-up. Crohn's disease patients on ustekinumab treatment were consecutively enrolled from 9 Hungarian Inflammatory Bowel Disease centers between January 2019 and May 2020. Patient and disease characteristics, treatment history, clinical disease activity (Harvey Bradshaw Index (HBI)), biomarkers, and endoscopic activity (Simple Endoscopic Score for Crohn's Disease (SES-CD)) were collected for three-years' time. A total of 148 patients were included with an overall 48.9% of complex behavior of the Crohn's disease and 97.2% of previous anti-TNF exposure. The pre-induction remission rates were 12.2% (HBI), and 5.1% (SES-CD). Clinical remission rates (HBI) were 52.2%, 55.6%, and 50.9%, whereas criteria of an endoscopic remission were fulfilled in 14.3%, 27.5%, and 35.3% of the subjects at the end of the first, second, and third year, respectively. Dose intensification was high with 84.0% of the patients on an 8-weekly and 29.9% on a 4-weekly regimen at the end of year 3. Drug sustainability was 76.9% during the follow-up period with no serious adverse events observed. Ustekinumab in the long-term is an effective, sustainable, and safe therapeutic option for Crohn's disease patients with severe disease phenotype and high previous anti-TNF biological failure, requiring frequent dose intensifications.

Comparative assessment of immunogenicity of recombinant insulin Aspart from BioGenomics and its originator NovoRapid® in adult patients with type 2 diabetes mellitus

OBJECTIVES

To assess and compare the immunogenicity of recombinant Insulin Aspart [manufactured by BioGenomics Limited (BGL-ASP)] with its originator NovoRapid® (manufactured by Novo Nordisk) in adult patients with type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

BGL-IA-CTP301 study was a randomized, open label, parallel group, multicenter phase-III clinical study to compare the efficacy and safety of recombinant Insulin Aspart 100 U/mL [manufactured by BioGenomics Limited (BGL-ASP)] with its reference medicinal product (RMP); NovoRapid® [manufactured by Novo Nordisk], in adult patients with Type 2 diabetes mellitus (T2DM). The primary objective of the study was to compare the immunogenicity of BGL-ASP and RMP; NovoRapid® in patient serum samples collected from phase-III clinical study. Immunogenicity was studied as the incidence of patients positive for anti-insulin Aspart (AIA) antibodies, developed against BGL-ASP/RMP at baseline, end of 12 week and end of 24 week of the treatment period. The changes in incidence of patients positive for AIA antibodies post-baseline were also studied to assess and compare the treatment-emergent antibody response (TEAR) between the treatment groups (BGL-ASP and RMP). Statistical evaluation was done by Fisher's exact test to compare the overall incidence of patients positive for AIA antibodies and the TEAR positives observed post-baseline in both the treated groups. An in-vitro neutralizing antibody assay (Nab assay) was also performed to study the effect of AIA antibodies in neutralizing the biological activity/metabolic function of the insulin. The neutralizing potential of AIA was studied by its effect on %glucose uptake. We also evaluated the association between AIA antibody levels and its impact on biological activity by studying the correlation between them.

RESULTS

Analysis of immunogenicity data suggested that the percentage of patients positive for AIA antibodies until week 24 was similar and comparable in both the treatment groups, BGL-ASP and RMP; NovoRapid®. The changes in incidence of patients positive for AIA post-baseline in terms of TEAR positives were also similar and comparable between the treatment groups. The results of the Nab assay with confirmed positive AIA samples from BGL-ASP- and RMP-treated groups did not have any negative impact on %glucose uptake by the cells in Nab assay, confirming the absence of neutralizing antibodies in both the treatment groups. The correlation studies also showed absence of association between AIA antibody levels and percentage glucose uptake in both BGL-ASP and RMP-NovoRapid® treatment groups. CONCLUSIONS: The immunogenicity assessment based on the overall incidence of patients positive for AIA, changes in incidence of patients positive for AIA post-baseline, TEAR rates and absence of neutralizing antibodies, were found to be apparently similar and comparable in both the treatment groups (BGL-ASP and RMP). We conclude from our studies that the immunogenicity of BGL-ASP is similar and comparable to RMP and the observed immunogenicity in terms of anti-insulin Aspart antibody levels had no impact on the biological activity of insulin.

Enhancing thermal stability in the CH2 domain to suppress aggregation through the introduction of simultaneous disulfide bonds in Pichia pastoris

Protein aggregations decrease production yields and impair the efficacy of therapeutics. The CH2 domain is a crucial part of the constant region of human IgG. But, it is also the least stable domain in IgG, which can result in antibody instability and aggregation problems. We created a novel mutant of the CH2 domain (T250C/L314C, mut10) by introducing a disulfide bond and expressed it using Pichia pastoris. The mut10 variant exhibited enhanced thermal stability, resistance to enzymatic degradation, and reduced aggregation in comparison to the original CH2 domain. However, it was less stable than mut20 (L242C/K334C), which is the variant prepared in a previous study (Gong et al., J. Biol. Chem., 2009). A more advanced mutant, mut25, was created by combining mut10 and mut20. Mut25 artificially contains two disulfide bonds. The new mutant, mut25, showed enhanced thermal stability, increased resistance to enzymatic digestion, and reduced aggregation in comparison to mut20. According to our knowledge, mut25 achieves an unprecedented level of stability among the humanized whole CH2 domains that have been reported so far. Mut25 has the potential to serve as a new platform for antibody therapeutics due to its ability to reduce immunogenicity by decreasing aggregation.

The MHC Associated Peptide Proteomics assay is a useful tool for the non-clinical assessment of immunogenicity

The propensity of therapeutic proteins to elicit an immune response, poses a significant challenge in clinical development and safety of the patients. Assessment of immunogenicity is crucial to predict potential adverse events and design safer biologics. In this study, we employed MHC Associated Peptide Proteomics (MAPPS) to comprehensively evaluate the immunogenic potential of re-engineered variants of immunogenic FVIIa analog (Vatreptacog Alfa). Our finding revealed the correlation between the protein sequence affinity for MHCII and the number of peptides identified in a MAPPS assay and this further correlates with the reduced T-cell responses. Moreover, MAPPS enable the identification of "relevant" T cell epitopes and may contribute to the development of biologics with lower immunogenic potential.

Development and validation of an automated assay for anti-drug-antibodies in rat serum

The potential immunogenicity of therapeutic human and humanized monoclonal antibodies (mAb) is a significant concern, and so preclinical testing of therapeutic mAbs routinely includes assessment of anti-drug antibody (ADA) induction. Here, we report the development of automated screening and confirmatory bridging ELISAs for the detection of rat antibodies against DH1042, an engineered human mAb for the SARS-CoV-2 receptor-binding domain. The assays were evaluated for specificity, sensitivity, selectivity, absence of a prozone effect, linearity, intra- and inter- assay precision, and robustness, and found to be suitable for purpose. The assays were then used to evaluate anti-DH1042 antibodies in the sera of rats dosed with lipid-nanoparticle (LNP)-encapsulated mRNA encoding DH1042. Rats received two doses of 0.1, 0.4 or 0.6 mg/kg/dose LNP-mRNA 8 days apart. Twenty-one days after the second dose, 50-100% of rats had developed confirmed anti-DH1042 ADA depending on dose level. No animals in the control group developed anti-DH1042 ADA. These assays reflect new applications for a non-specialized laboratory automation platform, and the methodologies and approaches reported here provide a template that can be adapted for the automated detection and confirmation of ADA in preclinical testing of other biologics.

Preclinical risk assessment strategy to mitigate the T-cell dependent immunogenicity of protein biotherapeutics: State of the art, challenges and future perspectives

Protein therapeutics hold a prominent role and have brought significant diversity in efficacious medicinal products. Not just monoclonal antibodies and different antibody formats (pegylated antigen-binding fragments, bispecifics, antibody-drug conjugates, single chain variable fragments, nanobodies, dia-, tria- and tetrabodies), but also purified blood products, growth factors, recombinant cytokines, enzyme replacement factors, fusion proteins are all good instances of therapeutic proteins that have been developed in the past decades and approved for their value in oncology, immune-oncology, and autoimmune diseases discovery programs. Although there was an ingrained belief that fully humanized proteins were expected to have limited immunogenicity, adverse effects associated with immune responses to biological therapies raised some concern in biotech companies. Consequently, drug developers are designing strategies to assess potential immune responses to protein therapeutics during both the preclinical and clinical phases of development. Despite the many factors that can contribute to protein immunogenicity, T cell- (thymus-) dependent (Td) immunogenicity seems to play a crucial role in the development of anti-drug antibodies (ADAs) to biologics. A broad range of methodologies to predict and rationally assess Td immune responses to protein drugs has been developed. This review aims to briefly summarize the preclinical immunogenicity risk assessment strategy to mitigate the risk of potential immunogenic candidates coming towards clinical phases, discussing the advantages and limitations of these technologies, and suggesting a rational approach for assessing and mitigating Td immunogenicity.

Development of a Cell-based Neutralizing Antibody Assay for Zinpentraxin Alfa: Challenges and Mitigation Strategies

Therapeutic protein drugs can potentially induce immune responses in patients and result in the production of anti-drug antibodies (ADAs), including a subset of ADAs called neutralizing antibodies (NAbs) that might cause loss of efficacy by inhibiting clinical activities of the drug. Herein, we describe the unique challenges encountered during the development of a fit-for-purpose cell-based NAb assay for a new protein modality, zinpentraxin alfa, including our strategies for assay design to overcome various matrix interferences and improve assay drug tolerance. We demonstrated that a typical biotin-drug extraction with acid dissociation (BEAD) approach alone was not sufficient to eliminate matrix interferences in this assay. Instead, the combination of the BEAD and ZebaTM spin size exclusion plate (SEP) was required to achieve the desirable assay performance. We also demonstrated that appropriate acidic buffers were critical in sample pretreatment to improve assay drug tolerance, which not only dissociated the drug/NAb immune complex but also effectively and irreversibly denatured the free drug. The final assay performed well with confirmed assay robustness and suitability for the clinical applications.

Development and validation of a LC-MS/MS method for quantitation of recombinant human growth hormone in rat plasma and application to a pharmacokinetic study

Recombinant human growth hormone (rhGH) is a peptide comprising 191 amino acids, that is mainly used to promote the growth of children and plays an important antiaging role. In the present study, a simple and sensitive quantitation method for rhGH in rat plasma was established by LCMS/MS. After simple and rapid enzymatic digestion of the plasma sample, two suitable surrogate peptides (LFDNAMLR and FPTIPLSR) were selected for quantitative analysis. The results showed good linearity over calibration range 10-2000 ng/mL. The quality control (QC) accuracy ranged from -13.8 to 14.3%, and the accuracy of the lower limit of quantification (LLOQ) ranged from -12.9 to 19.0%. The intra-day and inter-day precision ranges for all QCs were 1.7-13.6% and 4.0-7.0%, respectively. The method was successfully applied to intravenous and subcutaneous pharmacokinetic studies in rats. In comparison with previously published methods, our method features simple sample preparation combined with a short sample processing time (3.5 h), wide linear range (10-2000 ng/mL), small plasma volume (35 μL), and LLOQ (10 ng/mL).

A method for detection of anti-drug antibodies to a biotherapeutic (CSL112) with endogenous counterpart (apolipoprotein A-I) using a novel sample pre-treatment electrochemiluminescence assay

BACKGROUND

There are numerous challenges encountered during clinical testing for an immunogenic response to a plasma-derived therapeutic. Distinguishing between antibodies that recognize endogenous versus therapeutic protein can be particularly difficult. This study focused on CSL112 (human plasma-derived apolipoprotein A-I; apoA-I), which is in clinical development for reducing the risk of recurrent major adverse cardiovascular events following acute myocardial infarction.

AIM

To develop and validate a high-throughput, highly sensitive and specific assay to detect antibodies to CSL112 that can be used for immunogenicity assessment in large clinical studies.

RESULTS

We developed a clinical anti-drug antibody (ADA) assay utilizing an immunoglobulin purification step that improved specificity and drug tolerance, demonstrating that measurement of pre-existing or treatment emergent ADAs was highly dependent on assay format. The Sample Pre-treatment Electrochemiluminescence (ECL; SPECL) assay incorporates a protein A extraction of serum samples before a bridging assay is performed on an ECL platform. The assay is qualitative, sensitive (lower limit of quantification <39 ng/mL) and has a drug tolerance of 0.5 mg/mL in line with U.S. Food and Drug Administration requirements for clinical immunogenicity assays for therapeutic proteins. Importantly, the SPECL assay demonstrated the absence of antibodies to both apoA-I and CSL112 both prior to drug exposure and after repeated dosing across multiple trials (n = 970 subjects).

CONCLUSION

The SPECL method has been validated and applied to support the CSL112 preclinical and clinical development program and has broader application to similar protein therapeutics. Attributes of the methodology include high drug tolerance, high sensitivity, selectivity, and precision. This format is amenable to automation providing the high throughput and reduced variability required to support large scale clinical studies that span extended time periods.

The Immunology of Botulinum Toxin Therapy: A Brief Summary

Like all proteins foreign to the human body, also botulinum toxin (BT) is antigenic and may stimulate an immune response with formulation of antibodies (BT-AB). Affected patients may no longer respond to BT therapy and various degrees of BT-AB related therapy failure (ABF) may result. We want to review the immunological interactions between BT and BT-AB, the prevalence, the time course and the risk factors for BT-AB formation as they are related to the treatment algorithms, the patient's immune system and to exogenic factors. Special emphasis is placed on various features of the BT drugs including the specific biological activity (SBA) as a predictor of their antigenicity. Quantitative detection of BT-AB by the mouse diaphragm assay will be demonstrated. As ABF may have serious consequences for patients affected, careful risk factor analysis is warranted to reduce them wherever possible.

Regulatory Experience Assessing the Carcinogenic Potential of a Monoclonal Antibody Inhibiting PCSK9, Bococizumab, Including a 2-Year Carcinogenicity Study in Rats

Bococizumab is an anti-PCSK9 monoclonal antibody that was intended for the treatment of hypercholesterolemia. After reviewing the 6-month rat toxicity study data, in which there was a low spontaneous tumor incidence, unrelated to bococizumab administration, the U.S. FDA granted a carcinogenicity waiver request based on a weight-of-evidence assessment of low carcinogenic risk. Subsequently, after reviewing 6-month rat toxicity study data from another anti-PCSK9 antibody, RN317, with a similar low tumor incidence (unrelated to RN317), the U.S. FDA rescinded the bococizumab carcinogenicity study waiver and requested a full 2-year rat carcinogenicity study be conducted. The resulting 2-year carcinogenicity study demonstrated no bococizumab-related increase in tumors, confirming the weight-of-evidence evaluation and alleviating concerns regarding the carcinogenic potential. Here we report the scientific and regulatory background that led to the request for a rat carcinogenicity study, the feedback on the design of the carcinogenicity study, and the results from this study which affirmed the original weight-of-evidence assessment of low carcinogenic risk.

Immunogenicity of LY2963016 insulin glargine and Lantus® insulin glargine in Chinese patients with type 1 or type 2 diabetes mellitus

AIMS

To evaluate the immunogenicity of LY2963016 insulin glargine (LY IGlar) versus originator insulin glargine (IGlar [Lantus®]) in Chinese patients with type 1 (T1DM) or type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

ABES and ABET were prospective, randomized, active control, open-label, phase III studies, which enrolled Chinese patients with T1DM (N = 272) and T2DM (N = 536), respectively. Using data from these trials, immunogenicity of LY IGlar and IGlar was evaluated by comparing the proportion of patients with detectable anti-insulin glargine antibodies and the median antibody levels (percent binding) between the treatment groups. The incidence of anti-insulin antibodies and treatment-emergent antibody response (TEAR) were compared using Fisher's exact test or Pearson's chi-squared test. Levels of anti-insulin antibodies were compared using the Wilcoxon rank-sum test. We also evaluated the relationship between antibody formation or TEAR and clinical outcomes using analysis of covariance, negative binomial regression, or partial correlations.

RESULTS

There were no significant treatment differences in the incidence of detectable anti-insulin antibodies, median antibody levels or TEAR, overall or at Week 24 with last observation carried forward, and median antibody levels were low (<5%) after 24 weeks of treatment, in patients with T1DM or T2DM. Levels of anti-insulin antibodies and development of TEAR were not associated with efficacy (glycated haemoglobin, insulin dose [U/kg/d] and hypoglycaemia) or safety outcomes.

CONCLUSIONS

The immunogenicity profiles of LY IGlar and IGlar are similar, with low levels of anti-insulin antibodies observed for both insulins. No association was observed between antibody levels or TEAR status and clinical outcomes.

When to Extend Monitoring of Anti-drug Antibodies for High-risk Biotherapeutics in Clinical Trials: an Opinion from the European Immunogenicity Platform

The determination of a tailored anti-drug antibody (ADA) testing strategy is based on the immunogenicity risk assessment to allow a correlation of ADAs with changes to pharmacokinetics, efficacy, and safety. The clinical impact of ADA formation refines the immunogenicity risk assessment and defines appropriate risk mitigation strategies. Health agencies request for high-risk biotherapeutics to extend ADA monitoring for patients that developed an ADA response to the drug until ADAs return to baseline levels. However, there is no common understanding in which cases an extension of ADA follow-up sampling beyond the end of study (EOS) defined in the clinical study protocol is required. Here, the Immunogenicity Strategy Working Group of the European Immunogenicity Platform (EIP) provides recommendations on requirements for an extension of ADA follow-up sampling in clinical studies where there is a high risk of serious consequences from ADAs. The importance of ADA evaluation during a treatment-free period is recognized but the decision whether to extend ADA monitoring at a predefined EOS should be based on evaluation of ADA data in the context of corresponding clinical signals. If the clinical data set shows that safety consequences are minor, mitigated, or resolved, further ADA monitoring may not be required despite potentially detectable ADAs above baseline. Extended ADA monitoring should be centered on individual patient benefit.

Immunogenicity assessment of bispecific antibody-based immunotherapy in oncology

With increasing numbers of bispecific antibodies (BsAbs) and multispecific products entering the clinic, recent data highlight immunogenicity as an emerging challenge in the development of such novel biologics. This review focuses on the immunogenicity risk assessment (IgRA) of BsAb-based immunotherapies for cancer, highlighting several risk factors that need to be considered. These include the novel scaffolds consisting of bioengineered sequences, the potentially synergistic immunomodulating mechanisms of action (MOAs) from different domains of the BsAb, as well as several other product-related and patient-related factors. In addition, the clinical relevance of anti-drug antibodies (ADAs) against selected BsAbs developed as anticancer agents is reviewed and the advances in our knowledge of tools and strategies for immunogenicity prediction, monitoring, and mitigation are discussed. It is critical to implement a drug-specific IgRA during the early development stage to guide ADA monitoring and risk management strategies. This IgRA may include a combination of several assessment tools to identify drug-specific risks as well as a proactive risk mitigation approach for candidate or format selection during the preclinical stage. The IgRA is an on-going process throughout clinical development. IgRA during the clinical stage may bridge the gap between preclinical immunogenicity prediction and clinical immunogenicity, and retrospectively guide optimization efforts for next-generation BsAbs. This iterative process throughout development may improve the reliability of the IgRA and enable the implementation of effective risk mitigation strategies, laying the foundation for improved clinical success.

Adaptation of an ELISA assay for detection of IgG2a responses against therapeutic monoclonal antibodies in a mouse immunization model

Biotherapeutic monoclonal antibodies (mAb) play important roles in clinical medicine but their potential to elicit immune responses in patients remains a major issue. In a study designed to investigate the effect of aggregation on immunogenic responses, mice were immunized with two monoclonal antibodies (mAb1 and mAb2). Serum levels of total IgG, IgG₁, and IgG_2a were measured by ELISA. An anti-mouse IgG_2a monoclonal detection antibody cross-reacted with mAb2 but not mAb1, leading to high background when the ELISA plate was coated with mAb2. The problem was solved by use of a goat anti-mouse IgG_2a polyclonal antibody that demonstrated the required specificity. IgG_2a responses were similar for monomer- or aggregate-coated ELISA plates. The results demonstrate the importance of assessment of the specificity of individual reagents when measuring antibody responses against therapeutic antibodies by ELISA.

Immunogenicity Risk Assessment for Multi-specific Therapeutics

The objective of this manuscript is to provide the reader with a hypothetical case study to present an immunogenicity risk assessment for a multi-specific therapeutic as part of Investigational New Drug (IND) application. In order to provide context for the bioanalytical strategies used to support the multi-specific therapeutic presented herein, the introduction focuses on known immunogenicity risk factors. The subsequent hypothetical case study applies these principles to a specific example HC-12, based loosely on anti-TNFα and anti-IL-17A bispecific molecules previously in development, structured as an example immunogenicity risk assessment for submission to health authorities. The risk of higher incidence and safety impact of anti-drug antibodies (ADA) due to large protein complexes is explored in the context of multi-specificity and multi-valency of the therapeutic in combination with the oligomeric forms of the targets.

Secondary failure: immune responses to approved protein therapeutics

Recombinant therapeutic proteins are a broad class of biological products used to replace dysfunctional human proteins in individuals with genetic defects (e.g., factor VIII for hemophilia) or, in the case of monoclonal antibodies, bind to disease targets involved in cancers, autoimmune disorders, or other conditions. Unfortunately, immunogenicity (immune response to the drug) remains a key impediment, potentially affecting the safety and efficacy of these therapeutics. Immunogenicity risk is routinely evaluated during the licensure of therapeutic proteins. However, despite eliciting anti-drug immune responses in at least some patients, most protein drugs are nevertheless licensed as they address unmet medical needs. The pre-licensure immunogenicity assessments of therapeutic proteins are the subject of numerous reviews and white papers. However, observation and clinical management of the immunogenicity of approved therapeutic proteins face additional challenges. We survey the immunogenicity of approved therapeutic proteins, discuss the clinical management of immunogenicity, and identify the challenges to establishing clinically relevant immunogenicity assays for use in routine clinical practice.

Investigation of Factors Associated with Immunogenicity Labeling Updates and Characteristics of Biologics License Applications

Immunogenicity, the potential to elicit an anti-drug immune response, is a critical concern in developing biological products, but its consequences are difficult to predict with animal studies. The aims of the present study are to investigate the evolution of immunogenicity information in labeling and to identify attributes associated with immunogenicity labeling updates. Biologics License Applications (BLAs) approved by the Center for Drug Evaluation and Research, United States Food and Drug Administration between 2008 and 2017 were studied. A majority of BLAs described the incidence/prevalence of anti-drug antibodies (ADAs) (94.9%) and neutralizing antibodies (NAbs) (68.4%) in their original labeling documents. However, less than one-third of the BLAs mentioned the impact of ADAs/NAbs in the original (20.3%) and most recent (29.1%) labeling documents. BLAs with a priority review status (57.4% versus 33.3%), orphan designation (61.5% versus 34.2%), or a mention of ADA impact in the latest label (69.6% versus 38.9%) had higher percentages of applications with postmarketing requirements (PMRs) directly related to immunogenicity concerns in comparison with applications without those characteristics. Among the BLAs with updated immunogenicity information, the mean time to the first update was 1077 days, while that for BLAs with accelerated approval was shorter (709.1 ± 492.2 days versus 1173.8 ± 661.8 days). The results suggest that there is a substantial amount of critical information lacking in the original labeling documents and an overdependence on PMRs for more evidence. Additional efforts should be made to investigate the impact of ADAs to provide timely information for improved patient care.

Subcutaneous engineered factor VIIa marzeptacog alfa (activated) in hemophilia with inhibitors: Phase 2 trial of pharmacokinetics, pharmacodynamics, efficacy, and safety

BACKGROUND

Marzeptacog alfa (activated) (MarzAA), a novel recombinant activated human factor VII (FVIIa) variant, was developed to provide increased procoagulant activity, subcutaneous (SC) administration, and longer duration of action in people with hemophilia.

OBJECTIVES

To investigate if daily SC administration of MarzAA in subjects with inhibitors can provide effective prophylaxis.

METHODS

This multicenter, open-label phase 2 trial (NCT03407651) enrolled men with severe congenital hemophilia with an inhibitor. All subjects had a baseline annualized bleeding rate (ABR) of ≥12 events/year. Subjects received a single 18 μg/kg intravenous dose of MarzAA to measure 24-hour pharmacokinetics (PK) and pharmacodynamics (PD), single 30 μg/kg SC dose to measure 48-hour PK/PD, then daily SC 30 μg/kg MarzAA for 50 days. If spontaneous bleeding occurred, the dose was sequentially escalated to 60, 90, or 120 μg/kg, with 50 days at the final effective dose without spontaneous bleeding to proceed to a 30-day follow-up. The primary end point was reduction in ABR. Secondary end points were safety, tolerability, and antidrug antibody (ADA) formation.

RESULTS

In the 11 subjects, the mean ABR significantly reduced from 19.8 to 1.6, and the mean proportion of days with bleeding significantly reduced from 12.3% to 0.8%. Of a total of 517 SC doses, six injection site reactions in two subjects were reported. No ADAs were detected. One fatal unrelated serious adverse event occurred: intracerebral hemorrhage due to untreated hypertension.

CONCLUSIONS

The data demonstrated that MarzAA was highly efficacious for prophylactic treatment in patients with inhibitors by significantly decreasing bleed frequency and duration of bleeding episodes.

Liquid chromatography-mass spectrometry method for the quantification of an anti-sclerostin monoclonal antibody in cynomolgus monkey serum

Liquid chromatography tandem mass spectrometry (LC-MS/MS) has gradually become a promising alternative to ligand binding assay for the bioanalysis of biotherapeutic molecules, due to its rapid method development and high accuracy. In this study, we established a new LC-MS/MS method for the determination of the anti-sclerostin monoclonal antibody (SHR-1222) in cynomolgus monkey serum, and compared it to a previous electrochemiluminescence method. The antibody was quantified by detecting the surrogate peptide obtained by trypsin digestion. The surrogate peptide was carefully selected by investigating its uniqueness, stability and MS response. The quantitative range of the proposed method was 2.00-500 μg/mL, and this verified method was successfully applied to the toxicokinetic assessment of SHR-1222 in cynomolgus monkey serum. It was found that the concentrations of SHR-1222 in cynomolgus monkeys displayed an excellent agreement between the LC-MS/MS and electrochemiluminescence methods (ratios of drug exposure, 0.8-1.0). Notably, two monkeys in the 60 mg/kg dose group had abnormal profiles with a low detection value of SHR-1222 in their individual sample. Combining the high-level anti-drug antibodies (ADAs) in these samples and the consistent quantitative results of the two methods, we found that the decreased concentration of SHR-1222 was due to the accelerated clearance mediated by ADAs rather than the interference of ADAs to the detection platform. Taken together, we successfully developed an accurate, efficient and cost-effective LC-MS/MS method for the quantification of SHR-1222 in serum samples, which could serve as a powerful tool to improve the preclinical development of antibody drugs.

Pharmacokinetics and Immunogenicity of Frunevetmab in Osteoarthritic Cats Following Intravenous and Subcutaneous Administration

Osteoarthritis and other degenerative joint diseases are common causes of chronic pain in cats. Frunevetmab is a felinized monoclonal antibody that binds to nerve growth factor (NGF) and provides relief from pain by blocking the receptor-mediated signaling cascade induced by NGF. Results from three studies were combined to provide an overview of frunevetmab pharmacokinetics (PK) and immunogenicity. The objective of the first study was to establish the pharmacokinetic parameters resulting from intravenous (IV) and subcutaneous (SC) administration of frunevetmab to the feline patient population at 3 mg/kg. Ten adult cats with naturally-occurring osteoarthritis were administered frunevetmab in a crossover design at 28 day intervals. Non-compartmental pharmacokinetic analysis of the plasma concentration-time data showed that the half-life was 10.1 ± 1.9 days after IV dosing and the SC bioavailability was 60.3 ± 15.8% with maximum drug levels observed at 3-7 days after dosing. Plasma samples were collected at ~28 days after dosing during two field safety and effectiveness studies of cats with degenerative joint disease. The doses ranged from 1.0 to 2.8 mg/kg; 2 or 3 doses were administered either SC/IV, SC/SC, or SC/SC/SC. The data from these studies along with the data from the laboratory pharmacokinetic study were analyzed using non-linear mixed-effects (NLME) modeling. The model closely predicted the trough concentrations from the two field studies, including the IV treatment in the pilot field study. The trough concentrations were predicted to be close to steady-state after 2 doses. A second objective was to determine the incidence and clinical relevance of frunevetmab immunogenicity. A three-tier anti-drug antibody assay (screen, confirm, titer) was developed and validated. Immunogenicity was assessed in 259 frunevetmab-treated animals enrolled in the two field studies. Only 4 of these animals (1.5%) appeared to develop immunogenicity to frunevetmab. None of the four exhibited adverse events attributed to immunogenicity and no impact on drug levels or efficacy was observed in three of the animals. In the placebo animals, 2.3% (3/131) appeared to develop treatment-emergent immunogenicity. Overall, frunevetmab administration resulted in a very low incidence of treatment-emergent immunogenicity with no safety findings and minimal effect on drug exposure and efficacy.

Circumventing the side effects of L-asparaginase

L-asparaginase is an enzyme that catalyzes the degradation of asparagine and successfully used in the treatment of acute lymphoblastic leukemia. L-asparaginase toxicity is either related to hypersensitivity to the foreign protein or to a secondary L-glutaminase activity that causes inhibition of protein synthesis. PEGylated versions have been incorporated into the treatment protocols to reduce immunogenicity and an alternative L-asparaginase derived from Dickeya chrysanthemi is used in patients with anaphylactic reactions to the E. coli L-asparaginase. Alternative approaches commonly explore new sources of the enzyme as well as the use of protein engineering techniques to create less immunogenic, more stable variants with lower L-glutaminase activity. This article reviews the main strategies used to overcome L-asparaginase shortcomings and introduces recent tools that can be used to create therapeutic enzymes with improved features.

Characterization of the robust humoral immune response to GSK2618960, a humanized anti-IL-7 receptor monoclonal antibody, observed in healthy subjects in a Phase 1 study

Interleukin-7 (IL-7) signaling modulates T cell activity and is implicated in numerous autoimmune diseases. An anti-IL-7 receptor monoclonal antibody (GSK2618960) biotherapeutic was evaluated in healthy subjects for safety, pharmacokinetics (PK), pharmacodynamics (PD) and immunogenicity in a single-dose escalation phase I study. We found that antibodies against GSK2618960 (i.e., anti-drug antibodies or ADA) developed in 83% and 100% of GSK2618960-treated subjects in the 0.6 and 2.0 mg/kg dose cohorts, respectively. Of the ADA positive subjects, 64% (7 of 11) had detectable neutralizing activity. Further investigation revealed the presence of GSK2618960-specific memory B cells, indicating the development of immunological memory for the ADAs. Ex vivo stimulation of peripheral blood mononuclear cell (PBMC) samples demonstrated a relatively strong CD4⁺ T cell proliferation response to GSK2618960 as compared to the control anti-RSV antibody (which is known to have only low immunogenic potential), confirming the high immunogenic potential of GSK2618960. Furthermore, GSK2618960 was found to bind in vitro monocyte-derived dendritic cells (DCs). GSK2618960 treatment of PBMCs increased the proportion of DC cells showing an increase in expression of CD83, CD86 and CD209, which indicated enhanced DC differentiation and activation relative to the isotype control anti-β amyloid antibody. Collectively, the evidence supports that the high incidence of observed clinical immunogenicity was likely related to the receptor-mediated activity by GSK2618960.

Epitope characterization of anti-drug antibodies-a tool for discovery and health: an overview of the necessity of early epitope characterization to avoid anti-drug antibodies and promote patient health

Introduction: The market for monoclonal antibody (mAb) therapies is growing rapidly as the pharmaceutical industry expands its development across a broad spectrum of diseases. Unfortunately, as shown in the recent failure of bococizumab by Pfizer, these treatments often stimulate the formation of problematic anti-drug antibodies (ADAs). ADAs can cause side effects and limit efficacy for many patients. To increase efficacy and decrease safety concerns from ADAs, immunogenicity characterization is needed early in the drug development process. Here, we present emerging techniques that hold promise to improve ADA assays and their potential applications to pharmaceutical development and personalized medicine.Areas covered: This manuscript outlines the importance of epitope characterization to better understand immunogenicity and describes a strategy for using this information in treating patients taking mAb therapies.Expert opinion: We propose using high-information assays to characterize epitopes to help mAb therapy engineering and potentially improve individual patient outcomes. To understand this, we will discuss three different aspects of ADAs: (1) the problem of ADAs and what is currently being done about them, (2) the current state of epitope characterization and how it is being utilized, and (3) how early epitope characterization can advance drug discovery and improve outcomes for patients taking mAb therapies.

Comparison of the ELISA and ECL Assay for Vedolizumab Anti-drug Antibodies: Assessing the Impact on Pharmacokinetics and Safety Outcomes of the Phase 3 GEMINI Trials

Vedolizumab immunogenicity has been assessed using an enzyme-linked immunosorbent assay (ELISA) with a ~ 0.5 μg/mL drug interference, which may underestimate on-drug immunogenicity. We aimed to compare immunogenicity results between ELISA and the new drug-tolerant electrochemiluminescence (ECL) assay (and the two versions of neutralizing assays, drug-sensitive versus drug-tolerant). The ECL assay drug tolerance is ~ 100 times higher than that of the ELISA (≥ 50 μg/mL vs. 0.5 μg/mL with a 500 ng/mL positive control), and assay sensitivity is < 5 ng/mL for both assays. Vedolizumab immunogenicity was assessed in 2000 GEMINI 1 and 2 patients originally tested by ELISA and retested by ECL assay. Anti-drug antibody (ADA) impact on infusion-related reactions and pharmacokinetics (PK) was examined using descriptive statistics and population PK analyses. By ECL assay, 6% (86/1427) of patients treated with vedolizumab as induction and maintenance therapy tested ADA-positive. Of these, 20 patients were persistently positive and 56 had neutralizing antibodies. By ELISA, 4% (56/1434) of these patients were ADA-positive, 9 were persistently positive, and 33 had neutralizing antibodies. Among 61 patients with infusion-related reactions, 6 (10%) were ADA-positive (2 persistently positive) by ECL assay. By ELISA, 3 (5%) patients were both ADA-positive and persistently positive. Most results (96%) were similar with both assays. In the updated population PK model, ADA-positive status was estimated to increase vedolizumab linear clearance by a factor of 1.10 (95% credible interval 1.03-1.17), which is consistent with previous reports. The impact of ADA on safety and PK modeling remained generally consistent using either ELISA or ECL assay. ClinicalTrials.gov: NCT00783718 and NCT00783692.

Current Considerations for Immunoglobulin Isotype Characterization of Antibody Response against Biotherapeutics

The ability of biotherapeutics to induce immune response in patients has been broadly accepted. Humoral immune response to biotherapeutics is expected to be polyclonal in nature with a high degree of diversity, including treatment-induced anti-drug antibodies (ADA) immunoglobulin isotype composition. Therapeutics with strong potential to induce immunity may produce a T cell-dependent response resulting in a gradual transition from initial IgM based to mature, IgG-based ADAs. Immunoglobulin class switch and transition to high affinity IgG1 and IgG4 antibodies were linked to a reduced drug efficacy, accelerated clearance, development of drug neutralizing antibodies, and modulation of hypersensitivity reaction rates. Examples presented herein demonstrate that understanding of isotype composition of ADA response can be highly important to predict future of disease progression. Isotype characterization of ADA response can be viewed highly useful, particularly for high immunogenicity risk biotherapeutics although may be less relevant or used as a research tool only for medium and low immunogenicity risk level therapeutics. Isotype-specific characteristics, methods of detection, and several case studies are presented herein.

Assessment of clinically relevant immunogenicity for mAbs; are we over reporting ADA?

Immunogenicity is recognized as a possible clinical risk due to the development of anti drug antibodies (ADAs) that can adversely impact drug safety and efficacy. Although robust assays are currently used to assess the ADA, there is a debate on how best to generate the most appropriate immunogenicity data. There are several factors that can trigger ADA formation including the immunity status of the target population and the severity of the disease indication. Immunogenicity testing has defaulted to the most conservative approach regardless of the inherent risk of the molecule or the patient population. For low-risk biotherapeutics such as human monoclonal antibodies, ADA data that provide clinically relevant information should be prioritized when establishing immunogenicity monitoring plans.

Toward comparability of anti-drug antibody assays: is the amount of anti-drug antibody–reagent complexes at cut-point (CP-ARC) the missing piece?

Immunogenicity testing is a mandatory and critical activity during the development of therapeutic proteins. Multiple regulatory guidelines provide clear recommendations on appropriate immunogenicity testing strategies and required bioanalytical assay performances. Unfortunately, it is still generally accepted that a comparison of the immunogenicity of different compounds is not possible due to apparent performance differences of the used bioanalytical methods. In this perspective, we propose the ‘cut-point anti-drug antibody–reagents complex’ (CP-ARC) concept for technical comparability of the bioanalytical methods. The feasibility and implementation in routine assay development is discussed as well as the potential improvement of reporting of bioanalytical immunogenicity data to allow comparison across drugs. Scientific sound comparability of the bioanalytical methods is the first step toward comparability of clinical immunogenicity.

Formation and Glomerular Deposition of Immune Complexes in Mice Administered Human Antibodies: Evaluation of Dose, Frequency, and Biomarkers

Administration of human protein-based drugs to animals often leads to formation of antidrug antibodies (ADAs) that may form circulating immune complexes (CICs) with the dosed protein. Circulating immune complexes can activate and bind complement (cCICs), and if large amount of CICs or cCICs is formed, the clearance mechanism potentially becomes saturated, which can lead to immune complex (IC) deposition and inflammation. To obtain a better understanding of the underlying factors, including the relationship between different dose regimes on IC formation and deposition and identification of possible biomarkers of IC deposition and IC-related pathological changes in kidneys, BALB/c and C57BL/6J mice were administered with human anti-tumor necrosis factor α (aTNFα, adalimumab) or a humanized anti-TNP (aTNP) antibody for 13 weeks. Particularly, ADA, CIC, cCIC formation, IC deposition, and glomerulonephritis were observed in C57BL/6J administered with aTNFα, whereas the immunologic response was minor in BALB/c mice administered with aTNFα and in BALB/c and C57BL/6J mice administered aTNP. Changing dose levels or increasing dosing frequency of aTNFα on top of an already-established CIC and cCIC response did not lead to substantial changes in CIC, cCIC formation, or IC deposition. Finally, no association between the presence of CICs or cCIC in plasma and glomerular IC deposition and/or glomerulonephritis was observed.

Analysis of regulatory guidance on antidrug antibody testing for therapeutic protein products

Therapeutic proteins have the potential to induce unwanted immune responses. The potential impact of immunogenicity on pharmacokinetics, pharmacodynamics, safety and efficacy are well established. Here, we analyze key aspects of current US FDA and EMA guidelines on the development and validation of antidrug antibody assays. Although FDA and EMA guidance documents are in harmony on most points, EMA allows greater leeway for scientific judgement, while FDA recommends specific approaches that may not be appropriate in some situations. Many white papers suggest approaches different from the guidance documents, however, these can conflict with each other and are themselves only scientifically valid in certain situations. Here, we indicate when alternatives to guidance may be needed and what those approaches might be.

Clinical Immunogenicity Risk Assessment Strategy for a Low Risk Monoclonal Antibody

This article provides a theoretical case-study risk assessment report for a low-risk monoclonal antibody (mAb) therapeutic. In terms of risk, there are considerations around risks to safety, but also risks regarding effects on pharmacokinetics (PK), pharmacodynamics (PD), and efficacy. Much of the discussion in this document is around the risk of immunogenicity incidence. A higher incidence of immunogenicity would necessitate a detailed review of the PK, efficacy and safety in anti-drug antibody (ADA) positive and ADA negative subjects, in order to evaluate potential effects. The publication is intended to provide a framework of some the current thought processes around assessing immunogenicity risk and for building strategies to mitigate those risks. For this example, we have created a hypothetical antibody, ABC-123, targeting a membrane protein on antigen presenting cells, for the treatment of rheumatoid arthritis (RA). This hypothetical antibody therapeutic is provided as an example for the purposes of risk assessment for a low risk molecule, although any application of similar approach would be case by case.

IM-UNITI: Three-year Efficacy, Safety, and Immunogenicity of Ustekinumab Treatment of Crohn's Disease

BACKGROUND AND AIMS

Following induction/maintenance treatment in the UNITI/IM-UNITI studies of ustekinumab for Crohn's disease, patients entered a long-term extension for up to 5 years from induction. Efficacy through 152 and safety through 156 weeks are reported.

METHODS

At IM-UNITI Week 44, 567 ustekinumab-treated patients entered the long-term extension and continued to receive blinded subcutaneous ustekinumab on their assigned dose interval, without any subsequent dose adjustment. Placebo-treated patients discontinued after study unblinding [after IM-UNITI Week 44 analyses]. Efficacy data in the long-term extension [LTE] were collected every 12 weeks [q12w] before unblinding and then at q12w/q8w dosing visits.

RESULTS

Through Week 156, 29.6% of ustekinumab-treated patients discontinued. In an intent-to-treat analysis of randomised patients from IM-UNITI Weeks 0-152, 38.0% of ustekinumab induction responders receiving the drug q12w and 43.0% q8w were in remission at Week 152. Among patients entering the long-term extension in their original randomised groups, 61.9% of q12w and 69.5% of q8w patients were in remission at Week 152. Across all ustekinumab-treated patients [randomised and non-randomised] entering the long-term extension, remission rates at Week 152 were 56.3% and 55.1% for q12w and q8w, respectively. Safety events [per 100 patient-years] were similar among all ustekinumab-treated patients entering the long-term extension and placebo [overall adverse events 389.70 vs 444.17; serious adverse events, 18.97 vs 19.54; serious infections, 4.21 vs 3.97]. Rates of antibodies to ustekinumab through Week 156 remained low, 4.6% in all randomised ustekinumab-treated patients; lowest among patients in the original randomised q8w group [2/82, 2.4%].

CONCLUSIONS

Continued treatment with subcutaneous ustekinumab maintained clinical response and remission through 3 years in a majority of patients who responded to induction therapy and was well-tolerated. ClinicalTrials.gov number NCT01369355.

Design, creation and in vitro testing of a reduced immunogenicity humanized anti-CD25 monoclonal antibody that retains functional activity

Humanized and fully human sequence-derived therapeutic antibodies retain the capacity to induce anti-drug antibodies. Daclizumab (humanized version of the murine anti-Tac antibody; E.HAT) was selected for a proof of concept application of engineering approaches to reduce potential immunogenicity due to its demonstrated immunogenicity in the clinic. Reduced immunogenicity variants of E.HAT were created by identifying and modifying a CD4+ T cell epitope region in the VH region. Variant epitope region peptides were selected for their reduced capacity to induce CD4+ T cell proliferative responses in vitro. Variant antibody molecules were created, and CD25 affinity and potency were similar to the unmodified parent antibody. Fab fragments from the variant antibodies induced a lower frequency and magnitude of responses in human peripheral blood mononuclear cells proliferation tests. By the empirical selection of two amino acid mutations, fully functional humanized E.HAT antibodies with reduced potential to induce immune responses in vitro were created.

Biological Significance of Anti-GH Antibodies in Children Treated with rhGH

BACKGROUND

The occurrence of antidrug antibodies is common in children treated with recombinant human growth hormone (rhGH). However, their clinical significance is unclear.

OBJECTIVE

This study aimed to examine the clinical significance of anti-GH antibodies by analyzing the phenotype of patients who tested positive in relation to the quantity of anti-GH antibodies.

METHOD

In this laboratory-based retrospective study encompassing a time span of 6 years, all positive samples were identified, and senders were contacted. Anti-GH antibodies were measured using a radioprecipitation assay; positive samples underwent a confirmatory assay.

RESULTS

Out of a total of 104 samples from 66 patients, positive test results were found in 28 samples from 13 patients. Clinical data were available from all but one. The group with positive test results comprised 6 patients with a normal response to GH provocative tests (group A) and 6 with an insufficient response or with isolated GH deficiency (IGHD) type 1A (group B). Diagnoses in group A were neurosecretory dysfunction, bioinactive GH syndrome and constitutional delay of growth and puberty. Diagnoses in group B were IGHD type 1A, septo-optic dysplasia, and cerebral midline defect with multiple pituitary hormone deficiency. Insufficient growth response to rhGH was absent except in one sibling pair with IGHD type 1A and a patient with cerebral midline defect. These patients had the highest concentrations of anti-GH antibodies.

CONCLUSIONS

The biological significance of anti-GH antibodies seems to be limited to patients with high concentrations of anti-GH antibodies. For all other patients, we recommend a careful "wait and see" strategy and monitoring antibody titers.

Approaches to improve drug tolerance and target tolerance in the assessment of neutralizing anti-drug antibodies

Aim: Neutralizing anti-drug antibody (NAb) assays are inherently prone to the interference from drug and its soluble target, potentially resulting in erroneous results. An effective approach to improve drug tolerance of an NAb assay is pretreatment of samples with acid to dissociate immune complexes of NAb and drug, followed by separating NAbs from circulating drug before testing them in the assay. Methods and Results: The acid pretreatment conditions were optimized to improve drug tolerance of cell-based and non-cell-based NAb assays. NAbs were further separated from circulating drug either through direct drug removal or purification of NAb from the sample. In addition, an integrated experimental strategy was implemented to simultaneously improve drug and its soluble target tolerance for reliable NAb assessment. Conclusion: The approaches described herein would enable the development of reliable NAb assays that overcome drug and its target interference for more precise and sensitive NAb assessment.

Alternative dosing regimens for atezolizumab: an example of model-informed drug development in the postmarketing setting

PURPOSE

To determine the exposure-response (ER) relationships between atezolizumab exposure and efficacy or safety in patients with advanced non-small cell lung cancer (NSCLC) or urothelial carcinoma (UC) and to identify alternative dosing regimens.

METHODS

ER analyses were conducted using pooled NSCLC and UC data from phase 1 and 3 studies (PCD4989g, OAK, IMvigor211; ClinicalTrials.gov IDs, NCT01375842, NCT02008227, and NCT02302807, respectively). Objective response rate, overall survival, and adverse events were evaluated vs pharmacokinetic (PK) metrics. Population PK-simulated exposures for regimens of 840 mg every 2 weeks (q2w) and 1680 mg every 4 weeks (q4w) were compared with the approved regimen of 1200 mg every 3 weeks (q3w) and the maximum assessed dose (MAD; 20 mg/kg q3w). Phase 3 IMpassion130 (NCT02425891) data were used to validate the PK simulations for 840 mg q2w. Observed safety data were evaluated by exposure and body weight subgroups.

RESULTS

No significant ER relationships were observed for safety or efficacy. Predicted exposures for 840 mg q2w and 1680 mg q4w were comparable to 1200 mg q3w and the MAD and consistent with observed PK data from IMpassion130. Observed safety was similar between patients with a C_max above and below the predicted C_max for 1680 mg q4w and between patients in the lowest and upper 3 body weight quartiles.

CONCLUSION

Atezolizumab regimens of 840 mg q2w and 1680 mg q4w are expected to have comparable efficacy and safety as the approved regimen of 1200 mg q3w, supporting their interchangeable use and offering patients greater flexibility.

Mitigating target interference in bridging immunogenicity assay with target-blocking reagents and mild basic pH

Background: Soluble drug target in clinical study samples generated false positive results in anti-drug antibody (ADA) bridging assays due to target-mediated bridging. Results: The combination of two target-blocking reagents and mild basic assay pH resulted in high tolerance to recombinant target protein and reduced levels of positivity in clinical study samples with pharmacokinetic profiles that did not indicate significant ADA response. Testing with low-affinity ADA positive serum from immunized rabbits and known ADA positive samples from nonclinical studies in rats confirmed the assay's ability to detect ADA positive samples and the minimal impact of basic pH and target-blocking reagents on ADA detection. Conclusion: These strategies provide alternatives for mitigating target interference when standard target-blocking antibodies alone are ineffective.

Compatibility of immunogenicity guidance by the EMA and the US FDA

The guidelines for immunogenicity studies by the European Medicines Agency and the US FDA are based on different legislations and regulatory philosophies. In spite of the different background, the main guidelines are compatible on the scientific level, especially for new innovative therapeutic protein products. The importance of sensitive and drug-tolerant antidrug antibody assays and multidisciplinary approach to development and assessment are highlighted by both agencies. The main differences are in the field of biosimilars. The nonclinical in vivo immunogenicity studies are seen more useful by the FDA than by the European Medicines Agency. The draft FDA guidance on interchangeability will complicate global biosimilar development by requiring clinical switch studies with US sourced reference product.

Highly sensitive biomolecular interaction detection method using optical bound/free separation with grating-coupled surface plasmon field-enhanced fluorescence spectroscopy (GC-SPFS)

Grating-coupled surface plasmon field-enhanced fluorescence spectroscopy (GC-SPFS) with optical bound/free (B/F) separation technique was developed by employing a highly directional fluorescence with polarization of surface plasmon-coupled emission (SPCE) to realize highly sensitive immunoassay regardless of the ligand affinity. A highly sensitive immunoassay system with GC-SPFS was constructed using a plastic sensor chip reproducibly fabricated in-house by nanoimprinting and applied to the quantitative detection of an anti-lysozyme single-domain antibody (sdAb), to compare conventional washing B/F separation with optical B/F separation. Differences in the affinity of the anti-lysozyme sdAb, induced by artificial mutation of only one amino acid residue in the variable domain were attributed to higher sensitivity than that of the conventional Biacore surface plasmon resonance (SPR) system. The detection limit (LOD; means of six replicates of the zero standard plus three standard deviations) of the GC-SPFS immunoassay with optical B/F separation, was estimated to be 1.2 ng/ml with the low-affinity ligand (mutant sdAb Y52A: K_D level was of the order of 10⁻⁷ ~ 10⁻⁶ M) and was clearly improved as compared to that (LOD: 9.4 ng/ml) obtained with the conventional washing B/F separation. These results indicate that GC-SPFS with the optical B/F separation technique offers opportunities to re-evaluate low-affinity biomaterials that are neither fully utilized nor widespread, and could facilitate the creation of novel and innovative methods in drug and diagnostic development.

TCPro: an In Silico Risk Assessment Tool for Biotherapeutic Protein Immunogenicity

Most immune responses to biotherapeutic proteins involve the development of anti-drug antibodies (ADAs). New drugs must undergo immunogenicity assessments to identify potential risks at early stages in the drug development process. This immune response is T cell-dependent. Ex vivo assays that monitor T cell proliferation often are used to assess immunogenicity risk. Such assays can be expensive and time-consuming to carry out. Furthermore, T cell proliferation requires presentation of the immunogenic epitope by major histocompatibility complex class II (MHCII) proteins on antigen-presenting cells. The MHC proteins are the most diverse in the human genome. Thus, obtaining cells from subjects that reflect the distribution of the different MHCII proteins in the human population can be challenging. The allelic frequencies of MHCII proteins differ among subpopulations, and understanding the potential immunogenicity risks would thus require generation of datasets for specific subpopulations involving complex subject recruitment. We developed TCPro, a computational tool that predicts the temporal dynamics of T cell counts in common ex vivo assays for drug immunogenicity. Using TCPro, we can test virtual pools of subjects based on MHCII frequencies and estimate immunogenicity risks for different populations. It also provides rapid and inexpensive initial screens for new biotherapeutics and can be used to determine the potential immunogenicity risk of new sequences introduced while bioengineering proteins. We validated TCPro using an experimental immunogenicity dataset, making predictions on the population-based immunogenicity risk of 15 protein-based biotherapeutics. Immunogenicity rankings generated using TCPro are consistent with the reported clinical experience with these therapeutics.

Two validated liquid chromatography-mass spectrometry methods with different pretreatments for the quantification of an anti-CD47 monoclonal antibody in rat and cynomolgus monkey serum compared with an electrochemiluminescence method

Establishing reliable bioanalytical methods is essential to support pharmacokinetic (PK) studies in the preclinical and clinical evaluation of monoclonal antibody (mAb) drugs. Ligand binding assay (LBA) has always been the gold standard for protein quantification, whereas LC-MS has gradually become a promising alternative method for the study of pharmacokinetics of biotherapeutics with its advantages of accuracy and rapid method development. Here, we described for the first time two liquid chromatography-mass spectrometry (LC-MS) methods with different purification pretreatments, protein precipitation and immune affinity (IA) enrichment, along with one electrochemiluminescence (ECL) method for the quantification of an anti-CD47 monoclonal antibody (SHR-1603) in rat and cynomolgus monkey serum. An anti-adsorption reagent was added and digestion conditions were optimized to resolve the absorption issue of hydrophobic peptide in this study. These methods were all validated according to China Food and Drug Administration (CFDA) and European Medicines Agency (EMA) guidelines and were successfully applied to a preclinical study for the quantification of SHR-1603. The respective quantitative ranges of the three methods are respectively 250-500,000 ng/mL (protein precipitation), 100-100,000 ng/mL (IA) and 19.5-10,000 ng/mL (ECL). The two LC-MS methods were compared with ECL method respectively by the cross-validation using the Passing-Bablok regression and Bland-Altman plots. Systematic differences and proportional bias were observed between two LC-MS methods on the one hand and with the ECL method on the other hand. The drug concentrations obtained by the three methods showed good agreement in the low-dose group (ratios of drug exposure, 1.05-1.11), whereas the drug concentrations measured using the LC-MS methods were higher than those obtained by the ECL method in medium-dose and high-dose groups, which can be attributed to the forms of antibodies being determined (free and total). In conclusion, the established LC-MS methods exhibited superior accuracy, efficiency and cost-effectiveness for the PK assessment of SHR-1603 in the preclinical study. Thus, it provides a promising alternative to LBA in pre-clinical and clinical evaluation studies of mAb drugs in various matrices to facilitate the development of anti-tumor drugs.

Neutralizing Antibody Assay Development with High Drug and Target Tolerance to Support Clinical Development of an Anti-TFPI Therapeutic Monoclonal Antibody

Immunogenicity is a major challenge for protein therapeutics which can potentially reduce drug efficacy and safety and is often being monitored by anti-drug antibody (ADA) and neutralizing antibody (NAb) assays. Circulating targets and residual drugs in matrices can have significant impacts on accuracy of results from ADA and NAb assays, and sufficient drug and target tolerance for these assays are necessary. Here, we report the development of a competitive ligand binding (CLB) NAb assay for an anti-TFPI (tissue factor pathway inhibitor) monoclonal antibody (PF-06741086) with high drug and target tolerance to support ongoing clinical studies. A double acid affinity capture elution approach was used to mitigate drug interference, and a robust target removal strategy was employed to enhance target tolerance. The validated NAb assay has sensitivity of 313 ng/mL, drug tolerance of 50 μg/mL, and target tolerance of 1200 ng/mL. A step-by-step tutorial of assay development is described in this manuscript along with the rationale for using a high drug/target tolerant NAb assay. The NAb assay cut point factor obtained was 0.78. Other assay performance characteristics, e.g., precision and selectivity, are also discussed. This validated method demonstrated a superior drug and target tolerance to warrant specific and precise characterization of the NAb responses in support of ongoing clinical studies.