Pure red-cell aplasia and antierythropoietin antibodies in patients treated with recombinant erythropoietin

Establishing endotoxin limits to enhance the reliability of in vitro immunogenicity risk assessments

Immunogenic responses to biotherapeutics often lead to termination of their development because the resulting anti-drug-antibodies (ADA) can negatively impact pharmacology, safety, and efficacy. To mitigate ADA risks, in vitro risk assessment assays in non-clinical settings are essential to enhance safety and efficacy of protein-based therapeutics. This study aimed to develop and validate a human in vitro immunogenicity T cell proliferation assay. However, there is a lack of comprehensive guidelines for managing product-related factors such as endotoxin contamination, which can significantly influence assay sensitivity and accuracy. Our investigation of the impact of endotoxins revealed that levels above 0.1 EU/mg significantly induce T cell proliferation and CD14+ myeloid cell expansion, leading to potential false-positive outcomes in immunogenicity assessments. These findings suggest the importance of developing standardized protocols to enhance the predictive capability of in vitro methods, ensuring the assessment of therapeutic proteins accurately reflects their immunogenic potential without interference from contaminants.

Detection of erythropoietin in blood plasma through an SPRi-based biosensor

A new analytical method based on an SPRi biosensor has been established to determine erythropoietin (EPO) in biological fluids. This protein is involved in the growth of erythroid precursor cells and acts as a therapeutic agent in several diseases. It also appears to have increased biological activity in patients with Alzheimer's disease (AD). A validation process was carried out to assess the optimal ligand-antibody concentration by plotting a calibration curve of EPO. The low limit of detection (LOD) and limit of quantitation (LOQ) values indicate that the developed method can detect very low concentrations in the order of pg/mL. The LOD for EPO was 0.03 pg/mL. The LOQ was 0.10 pg/mL. In addition, determining the appropriate validation parameters confirmed that the designed biosensor has high precision, accuracy, and sensitivity. To prove the usefulness of the biosensor in practice, determinations were performed on blood plasma samples from a control group and a study group consisting of patients with AD. The preliminary results indicate that this biosensor can detect EPO in plasma samples. Confirmation that patients with AD have higher levels of EPO will require the analysis of a more significant number of samples. However, the constructed biosensor is characterized by its simplicity and rapidity of measurement, and the method does not require any special sample preparation.

UK kidney association clinical practice guideline: update of anaemia of chronic kidney disease

Anaemia is common in chronic kidney disease (CKD) encompassing non-dialysis dependent CKD (NDD-CKD) and dialysis dependent CKD (DD-CKD); people on peritoneal dialysis (PD) and haemodialysis (HD); and kidney transplant recipients (KTR). Iron deficiency and erythropoietin deficiency are the most common causes of anaemia in people with CKD, especially those requiring kidney replacement therapy (KRT). The Renal National Service Framework and National Institute for Health and Clinical Excellence in the UK, and Kidney Disease Improving Global Outcomes (KDIGO), all advocate treatment of anaemia in people with CKD. Blood transfusions are infrequently required, and newer therapies such as Hypoxia-Inducible Factor (HIF-PHI) stabilisers are now in current use. This guideline provides evidence based graded practice guidance on the use of iron; comments on iron deficiency without anaemia in people with CKD; provide further information on anaemia management in people with a transplant and provide guidance in the use of the new HIF-PHI drugs. It also provides audit and research recommendations.

Research progress of mosquito-borne virus mRNA vaccines

In recent years, mRNA vaccines have emerged as a leading technology for preventing infectious diseases due to their rapid development and high immunogenicity. These vaccines encode viral antigens, which are translated into antigenic proteins within host cells, inducing both humoral and cellular immune responses. This review systematically examines the progress in mRNA vaccine research for major mosquito-borne viruses, including dengue virus, Zika virus, Japanese encephalitis virus, Chikungunya virus, yellow fever virus, Rift Valley fever virus, and Venezuelan equine encephalitis virus. Enhancements in mRNA vaccine design, such as improvements to the 5' cap structure, 5'UTR, open reading frame, 3'UTR, and polyadenylation tail, have significantly increased mRNA stability and translation efficiency. Additionally, the use of lipid nanoparticles and polymer nanoparticles has greatly improved the delivery efficiency of mRNA vaccines. Currently, mRNA vaccines against mosquito-borne viruses are under development and clinical trials, showing promising protective effects. Future research should continue to optimize vaccine design and delivery systems to achieve broad-spectrum and long-lasting protection against various mosquito-borne virus infections.

Potential risk factors of protein aggregation in syringe handling during antibody drug dilution for intravenous administration

Protein aggregation, a major concern in biopharmaceutical quality control, can be accelerated by various stresses during clinical handling. This study investigated potential aggregation risk factors during dilution process with syringe handling for intravenous administration. Using γ-globulin and IgG solutions as surrogate models of antibody therapeutics, we examined the effects of high sliding speeds and piston operations of the syringe on protein aggregation during saline dilution. Our results revealed that elevated sliding speeds promoted proteinaceous subvisible and/or visible particle formation, which was further enhanced by piston operations. The proteinaceous particle formation was presumed to be caused by fine air bubbles generated due to rapid pressure changes arising from shear stress during needle passage. While polysorbate 20 effectively suppressed the particle formation induced by the syringe handling at sufficient concentrations, its protective effect became inadequate under high dilution conditions, as exemplified by those encountered in low-body-weight patient protocols. Different proteins exhibited varying susceptibility to the syringe-induced aggregation. These findings demonstrate that the combination of syringe handling and dilution conditions could significantly impact protein stability during clinical handling, particularly for less stable biopharmaceuticals. A deeper understanding of these factors is crucial for developing more robust formulations and establishing safer handling practices for biopharmaceuticals.

What are clinically significant anti-drug antibodies and why is it important to identify them

The FDA has released new draft guidance to standardize how immunogenicity of protein therapeutics is described in product labels. A key aspect to this new guidance is that companies should describe anti-drug antibodies that have clinical significance in addition to reporting ADAs' incidence. Factors to consider when determining clinical significance include if those antibodies have a significant effect on the drug's pharmacokinetics, pharmacodynamics, efficacy, and/or safety. While in many instances, the humoral response to protein therapeutics does not have any clinical significance, there are cases where there is a clinically significant effect and it is important to communicate this information to physicians and patients. This new guidance also delineates where immunogenicity information should be listed in product labels which should provide consistency in how this information is listed. There are many factors that contribute to a therapeutic's immunogenicity and determining clinical significance is both complex and challenging, requiring that companies perform thorough analyses with scientific rigor. The analysis that is now proposed to understand clinical significance of ADAs is a new concept and will require companies to develop a strategy for compliance. This manuscript sets forth some of the key considerations in answering this important question. One of the benefits that this new guidance will provide is a common approach for describing the immune response to therapeutics that will be located in a dedicated section of the label, providing valuable consistency across protein therapeutics. Section 12.6 in the Clinical Pharmacology portion of the label will contain the relevant immunogenicity information, which will make it much simpler to find immunogenicity information in product labels. This new guidance is currently being utilized for new protein therapeutics and companies are being requested to systematically revise the labels of previously approved drugs for compliance, although an absolute timeline for this has not been established as of this writing.

Challenging the Standard Immunogenicity Assessment Approach: 1-Tiered ADA Testing Strategy in Clinical Trials

The ADA testing strategy for protein therapeutics was established almost two decades ago when assay methodologies were rudimentary, and serious immunogenicity-related safety issues had recently been observed with some biotherapeutics. The current testing paradigm employs multiple tiers and stringent cut points to minimize false negatives, reflecting a conservative stance towards ADA analysis. The development of highly sensitive ADA assay platforms and technologies such as humanized or fully human monoclonal antibody (mAb) drugs has put the traditional, resource-intensive 3-tiered testing approach under scrutiny. ADA data from clinical studies for three different mAb programs were re-assessed to explore the feasibility of a simplified 1-tiered ADA testing strategy with a 1% false positive cut point versus the traditional 3-tiered approach. The analysis demonstrated moderate to strong correlations between screening results (signal-to-noise, S/N) and those of confirmation and titer results, with the vast majority of samples (~ 97%) across all studies having the same ADA positive/negative classification with either testing approach. Furthermore, at the subject level, over 92% had the same ADA category (pre-existing, treatment-emergent, treatment-boosted) under both testing approaches. The re-categorized subjects had low titer ADA responses with no observed clinical implications on pharmacokinetics, efficacy, or safety. Finally, the treatment-emergent ADA incidences were comparable between the 1-tiered and 3-tiered approaches. The results demonstrate that the 1-tiered testing strategy is suitable for ADA assessment in these programs and is likely more widely applicable. Additionally, the 1-tiered approach could expedite data delivery and reduce resource needs in clinical development without compromising data quality or clinical interpretation.

Immunogenicity risk assessment and mitigation for engineered antibody and protein therapeutics

Remarkable progress has been made in recent decades in engineering antibodies and other protein therapeutics, including enhancements to existing functions as well as the advent of novel molecules that confer biological activities previously unknown in nature. These protein therapeutics have brought major benefits to patients across multiple areas of medicine. One major ongoing challenge is that protein therapeutics can elicit unwanted immune responses (immunogenicity) in treated patients, including the generation of anti-drug antibodies. In rare and unpredictable cases, anti-drug antibodies can seriously compromise therapeutic safety and/or efficacy. Systematic deconvolution of this immunogenicity problem is confounded by the complexity of its many contributing factors and the inherent limitations of available experimental and computational methods. Nevertheless, continued progress with the assessment and mitigation of immunogenicity risk at the preclinical stage has the potential to reduce the incidence and severity of clinical immunogenicity events. This Review focuses on identifying key unsolved anti-drug antibody-related challenges and offers some pragmatic approaches towards addressing them. Examples are drawn mainly from antibodies, given that the majority of available clinical data are from this class of protein therapeutics. Plausible and seemingly tractable solutions are in sight for some immunogenicity problems, whereas other challenges will likely require completely new approaches.

Positive response of a hemodialysis patient with pure red cell aplasia on recombinant human erythropoietin therapy to cyclosporine and Roxadustat

Recombinant human erythropoietin (rHuEPO) is commonly used to treat anemia associated with chronic kidney disease (CKD). EPO-induced Pure Red Cell Aplasia (PRCA) is a rare condition of profound anemia with EPO treatment. Upon finding the development of EPO-induced PRCA, the treatment requires immediate withdrawal of EPO therapy and initiate new treatments with immunosuppression or renal transplantation. Anti-EPO antibody assay is not always positive in EPO-induced PRCA. Here, we report a case on the sudden development of PRCA in a hemodialysis patient receiving EPO and how we treated the condition successfully with cyclosporine and subsequently maintained the hemoglobin with Roxadustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor (HIF-PHI). Even though the anti-EPO antibody was negative by Enzyme Linked Immunosorbent Assay (ELISA) in our case, the clinical course, the markedly reduced reticulocyte count < 10,000/μL, the bone marrow (BM) biopsy revealing reduced erythroblasts, and its subsequent response to cyclosporine, were similar to EPO-induced PRCA. The clinical picture of EPO-induced PRCA, the limitation of the EPO-neutralizing antibody (Ab) assay, and treatment strategies were discussed.

The importance of World Health Organization international reference standards in the product life cycle of biosimilars

Technological advances in analytics, as well as scientific and regulatory knowledge and experience gained from biosimilar development/approvals over the last decade, enabled the World Health Organization (WHO) in 2022 to revise its guidelines on the evaluation of biosimilars. Among the revisions, there is more reliance on analytical and functional aspects to prove similarity (and likely fewer clinical requirements). WHO international reference standards for biosimilars provide additional confidence to regulators looking for evidence- and data-based regulatory convergence in scientific and technical measures of quality attributes. These standards serve as a benchmark for harmonizing the bioactivity or potency of biosimilars, ensuring their future sustainability. This article discusses the availability and role of WHO international reference standards throughout the product life cycle of biosimilars.

Re-thinking the current paradigm for clinical immunogenicity assessment: an update from the discussion in the European Bioanalysis Forum

Immunogenicity regulatory guidance and industry recommendations have evolved over the last two decades since unexpected immune reactions were first reported with erythropoietin. Since then, the guidelines and practices for immunogenicity have stemmed from a reaction to a high-risk molecule causing significant clinical impact. Similar thinking is often applied to all biotherapeutic drugs, even when a well-defined risk assessment suggests otherwise. In recent years, the current testing paradigm for immunogenicity has been challenged with more informative approaches being proposed. In a Focus Workshop held by the European Bioanalysis Forum in September 2023, the current immunogenicity testing paradigm was challenged based on the experience and learning of 20+ years of immunogenicity strategies. The workshop recommendations proposed a new paradigm, challenging the value of multiple tiers depending on the immunogenicity risk assessment based on context of use and moving toward treating immunogenicity as a pharmacodynamic biomarker for the drug. Such rethinking ultimately results in the appropriate and efficient focusing of resources on immunogenicity testing strategies that benefit patients most, moving to a new paradigm where implementation of appropriate and truly informative immunogenicity testing strategies, depending on the context-of-use, become the norm .

Role of erythropoietin in the treatment of Alzheimer's disease: the story so far

This review aims to explore the potential of erythropoietin, a glycopeptide hormone, as a treatment option for Alzheimer's disease, which is the commonest cause of dementia. Despite years of focus and research, therapeutic options for Alzheimer's disease are not yet completely satisfactory. And as people age, they are likely to develop Alzheimer's Disease, further pressuring the healthcare system. So, it is definite to develop treatment options that meet superior outcomes with minimal negative effects. A comprehensive review of the literature was conducted in PubMed and Google Scholar using a combination of keywords, including Alzheimer's disease, dementia, erythropoietin, and neuroprotection. Search results were assessed for relevance before using the data for this study. The beneficial implications of erythropoietin as a therapeutic option have been explored, along with the side effects and mechanisms of erythropoietin in Alzheimer's disease. Overall, the authors' review indicates that erythropoietin presents a promising avenue for mitigating the progression of Alzheimer's disease, with minimal associated side effects.

A Case of Erythropoietin (EPO)-Induced Pure Red Cell Aplasia and Its Treatment Efficacy With Desidustat

Pure red cell aplasia (PRCA), a rare hematological disorder marked by severe anemia and reticulocytopenia, results from the near absence of developing erythroid precursors in the otherwise normal bone marrow. This case report focuses on a 48-year-old female with chronic kidney disease (CKD) who received erythropoietin injections for CKD-related secondary anemia. Despite an initial positive response, a sudden drop in hemoglobin levels prompted investigations, revealing endogenous erythropoietin (EPO)-induced PRCA due to anti-EPO antibodies. In response, desidustat, an oral hypoxia-inducible factor-prolyl hydroxylase inhibitor, was successfully introduced as an alternative treatment. This led to a substantial and sustained improvement in hemoglobin levels, emphasizing the crucial role of swift diagnosis and intervention in EPO-induced PRCA cases. Administration method and storage conditions are noteworthy factors influencing recombinant human erythropoietin (rHuEPO) immunogenicity. The case underscores desidustat's emergence as a less immunogenic and effective alternative for anemia, marking a significant advancement, particularly in the context of this pioneering case in India showcasing its efficacy.

Engineering Antigen-Specific Tolerance to an Artificial Protein Hydrogel

Artificial protein hydrogels are an emerging class of biomaterials with numerous prospective applications in tissue engineering and regenerative medicine. These materials are likely to be immunogenic due to their frequent incorporation of novel amino acid sequence domains, which often serve a functional role within the material itself. We engineered injectable "self" and "nonself" artificial protein hydrogels, which were predicted to have divergent immune outcomes in vivo on the basis of their primary amino acid sequence. Following implantation in mouse, the nonself gels raised significantly higher antigel antibody titers than the corresponding self gels. Prophylactic administration of a fusion antibody targeting the nonself hydrogel epitopes to DEC-205, an endocytic receptor involved in Treg induction, fully suppressed the elevated antibody titer against the nonself gels. These results suggest that the clinical immune response to artificial protein biomaterials, including those that contain highly antigenic sequence domains, can be tuned through the induction of antigen-specific tolerance.

Phase 1, first-in-human study of TYRP1-TCB (RO7293583), a novel TYRP1-targeting CD3 T-cell engager, in metastatic melanoma: active drug monitoring to assess the impact of immune response on drug exposure

Introduction

Although checkpoint inhibitors (CPIs) have improved outcomes for patients with metastatic melanoma, those progressing on CPIs have limited therapeutic options. To address this unmet need and overcome CPI resistance mechanisms, novel immunotherapies, such as T-cell engaging agents, are being developed. The use of these agents has sometimes been limited by the immune response mounted against them in the form of anti-drug antibodies (ADAs), which is challenging to predict preclinically and can lead to neutralization of the drug and loss of efficacy.

Methods

TYRP1-TCB (RO7293583; RG6232) is a T-cell engaging bispecific (TCB) antibody that targets tyrosinase-related protein 1 (TYRP1), which is expressed in many melanomas, thereby directing T cells to kill TYRP1-expressing tumor cells. Preclinical studies show TYRP1-TCB to have potent anti-tumor activity. This first-in-human (FIH) phase 1 dose-escalation study characterized the safety, tolerability, maximum tolerated dose/optimal biological dose, and pharmacokinetics (PK) of TYRP1-TCB in patients with metastatic melanoma (NCT04551352).

Results

Twenty participants with cutaneous, uveal, or mucosal TYRP1-positive melanoma received TYRP1-TCB in escalating doses (0.045 to 0.4 mg). All participants experienced ≥1 treatment-related adverse event (TRAE); two participants experienced grade 3 TRAEs. The most common toxicities were grade 1-2 cytokine release syndrome (CRS) and rash. Fractionated dosing mitigated CRS and was associated with lower levels of interleukin-6 and tumor necrosis factor-alpha. Measurement of active drug (dual TYPR1- and CD3-binding) PK rapidly identified loss of active drug exposure in all participants treated with 0.4 mg in a flat dosing schedule for ≥3 cycles. Loss of exposure was associated with development of ADAs towards both the TYRP1 and CD3 domains. A total drug PK assay, measuring free and ADA-bound forms, demonstrated that TYRP1-TCB-ADA immune complexes were present in participant samples, but showed no drug activity in vitro.

Discussion

This study provides important insights into how the use of active drug PK assays, coupled with mechanistic follow-up, can inform and enable ongoing benefit/risk assessment for individuals participating in FIH dose-escalation trials. Translational studies that lead to a better understanding of the underlying biology of cognate T- and B-cell interactions, ultimately resulting in ADA development to novel biotherapeutics, are needed.

Antibody-Drug Conjugate Overview: a State-of-the-art Manufacturing Process and Control Strategy

Antibody-drug conjugates (ADCs) comprise an antibody, linker, and drug, which direct their highly potent small molecule drugs to target tumor cells via specific binding between the antibody and surface antigens. The antibody, linker, and drug should be properly designed or selected to achieve the desired efficacy while minimizing off-target toxicity. With a unique and complex structure, there is inherent heterogeneity introduced by product-related variations and the manufacturing process. Here this review primarily covers recent key advances in ADC history, clinical development status, molecule design, manufacturing processes, and quality control. The manufacturing process, especially the conjugation process, should be carefully developed, characterized, validated, and controlled throughout its lifecycle. Quality control is another key element to ensure product quality and patient safety. A patient-centric strategy has been well recognized and adopted by the pharmaceutical industry for therapeutic proteins, and has been successfully implemented for ADCs as well, to ensure that ADC products maintain their quality until the end of their shelf life. Deep product understanding and process knowledge defines attribute testing strategies (ATS). Quality by design (QbD) is a powerful approach for process and product development, and for defining an overall control strategy. Finally, we summarize the current challenges on ADC development and provide some perspectives that may help to give related directions and trigger more cross-functional research to surmount those challenges.

The Impact of Immunogenicity on the Pharmacokinetics, Efficacy, and Safety of Sotatercept in a Phase III Study of Pulmonary Arterial Hypertension

Sotatercept, a soluble fusion protein comprising the extracellular domain of activin receptor type IIA linked to the Fc portion of human IgG1, is a first-in-class activin signaling inhibitor under development for the treatment of pulmonary arterial hypertension (PAH). We evaluated antidrug antibody (ADA) development and determined the effects of immunogenicity on the pharmacokinetics (PKs), efficacy, and safety of sotatercept in STELLAR, a multicenter, double-blind phase III trial (NCT04576988) wherein participants with PAH were randomized 1:1 to receive sotatercept (starting dose 0.3; target dose 0.7 mg/kg) or placebo subcutaneously every 3 weeks in combination with background therapies for ≤ 72 weeks. ADA-positive (ADA-POS) participants were identified and characterized for neutralizing antibodies (NAbs). PKs, efficacy, and safety were evaluated by ADA and NAb status. Of 162 evaluable participants, 42 (25.9%) were ADA-POS through week 24, of whom 11 (6.8%) were also NAb-POS. Median onset of ADAs was 3.29 weeks (interquartile range (IQR): 3.14-6.14), and median duration was 6 weeks (IQR: 3.14-17.86). No clinically meaningful differences were found across subgroups that were ADA-NEG, ADA-POS/NAb-NEG, and ADA-POS/NAb-POS, in terms of PKs (sotatercept trough concentration over time, mean postdose trough concentration at the end of treatment, and clearance), efficacy (changes from baseline in 6-minute walk distance, pulmonary vascular resistance, and N-terminal pro-B-type natriuretic peptide levels), and safety (incidence of hypersensitivity, anaphylactic reactions, and administration site reactions). We conclude that ADA incidence from sotatercept treatment was 25.9% and did not meaningfully affect the PKs, efficacy, or safety of sotatercept in participants with PAH.

Tolerating CD47

Cluster of differentiation 47 (CD47) occupies the outer membrane of human cells, where it binds to soluble and cell surface receptors on the same and other cells, sculpting their topography and resulting in a pleiotropic receptor-multiligand interaction network. It is a focus of drug development to temper and accentuate CD47-driven immune cell liaisons, although consideration of on-target CD47 effects remain neglected. And yet, a late clinical trial of a CD47-blocking antibody was discontinued, existent trials were restrained, and development of CD47-targeting agents halted by some pharmaceutical companies. At this point, if CD47 can be exploited for clinical advantage remains to be determined. Herein an airing is made of the seemingly conflicting actions of CD47 that reflect its position as a junction connecting receptors and signalling pathways that impact numerous human cell types. Prospects of CD47 boosting and blocking are considered along with potential therapeutic implications for autoimmune diseases and cancer.

Successful Development of Nonclinical Anti-Drug Antibody Assays to Support Zinpentraxin Alfa Reproductive Toxicology Studies

Immunogenicity assessment is an essential part of biotherapeutic drug development. While the immune response in animals is not always representative of the human immune response, immunogenicity data obtained in animal models is still informative for the evaluation of drug exposure and safety. The most common assay format used for the detection of anti-drug antibodies (ADAs) in preclinical and clinical studies is the bridging format. The advantage of this method is that it can detect all antibody isotypes generated against the therapeutic. However, the method development can be time-consuming and labor-intensive, due to the need for labeling of the drug which is used both as capture and detection. Various generic ADA assays have been successfully implemented to overcome these disadvantages and to enable faster assay development timelines to support nonclinical toxicology studies. Here, we describe the challenges in the development of an assay to detect antibodies to zinpentraxin alfa, a recombinant human pentraxin-2, in rabbit and rat toxicology studies. Our initial efforts to develop a bridging assay failed, prompting us to develop a method adapted from generic assay formats to detect anti-zinpentraxin alfa antibodies in the serum of different species with minimal optimization. However, while the general assay format remained similar, assay reagents were adapted between the different species, resulting in the development of two distinct assays for the detection of ADAs in rat and rabbit. Here, we share the final development/validation data and the immunogenicity study results. Our work highlights the need for the evaluation of alternate assay formats when evaluating novel drug modalities.

Niraparib-induced pure red cell aplasia

INTRODUCTION

Niraparib, a strong poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitor, contributed significantly to progression-free survival as a maintenance therapy in the platinum-sensitive period in both first-line and recurrent ovarian cancer, regardless of the BRCA mutation. Grade 3-4 anemia, which has a manageable side effect profile, especially hematological, is seen in almost 1 out of every 4 patients. To the best of our knowledge, there has been no reported case of pure red cell aplasia (PRCA) induced by niraparib treatment.

CASE REPORT

A 65-year-old woman diagnosed with stage 3 serous carcinoma of the tuba received niraparib front-line maintenance treatment had grade 4 anemia after 3 months of niraparib treatment. She underwent bone marrow aspiration and biopsy because of refractory anemia, which needs red blood cell (RBC) transfusions despite interruption of treatment.

MANAGEMENT AND OUTCOME

The patient was treated with 1 mg/kg methyl prednisolone, after histopathological assessment was consistent with PRCA. The hemoglobin count returned to the normal range with steroid treatment.

DISCUSSION

In daily practice, it should be kept in mind that in the case of refractory anemia induced by niraparib, the underlying cause might be PRCA and can be improved with steroid administration.

Dupilumab-Related Diabetes Mellitus With Reversal of Symptoms in a Non-genetically Predisposed Patient

Dupilumab is a fully humanized monoclonal antibody that binds to IL-4 receptors and blocks IL-4 and IL-13 mediated T-helper 2 (Th2) responses. Dupilumab is estimated to be used by over 600,000 patients worldwide for the treatment of atopic dermatitis and other immunologic conditions. Recently, a 66-year-old male patient being treated for atopic dermatitis with dupilumab presented to the clinic with complaints of polyuria and polydipsia. Upon initial testing, the patient was found to have considerable hyperglycemia. Upon genetic testing, he showed no predisposition for autoimmune diabetes and was negative for type I diabetes mellitus-associated human leukocyte antigen (HLA) genes. After immediate cessation of dupilumab, and with subsequent insulin therapy, the patient was able to obtain glycemic control. Following taper and eventual cessation of insulin therapy and over the course of seven months, the patient was able to achieve a full resolution of symptoms and his glycosylated hemoglobin (HgBA1c) levels returned to normal ranges. This case represents only the second documented case of dupilumab-induced diabetes mellitus and is the first known documented case of dupilumab-induced diabetes mellitus in a non-genetically predisposed individual. This case also describes a previously unobserved spontaneous resolution of symptoms upon cessation of the drug. This case further illustrates the potential existence of immunogenic or immunomodulatory side effects of the monoclonal antibody dupilumab that can affect patients who are both genetically and non-genetically predisposed to autoimmune diabetes mellitus.

Mitigation of Anti-Drug Antibody Production for Augmenting Anticancer Efficacy of Therapeutic Protein via Co-Injection of Nano-Rapamycin

The induction of anti-drug antibody (ADA) is a formidable challenge for protein-based therapy. Trichosanthin (TCS) as a class of ribosome-inactivating proteins is widely studied in tumor treatment. However, the immunogenicity can induce the formation of ADA, which can cause hypersensitivity reactions and neutralize the efficacy of TCS, thus limiting its clinical application in cancer therapy. Here, a promising solution to this issue is presented by co-administration of the rapamycin nanoparticles and TCS. PEGylated rapamycin amphiphilic molecule is designed and synthesized as a prodrug and a delivery carrier, which can self-assemble into a nanoparticle system with encapsulation of free rapamycin, a hydrophobic drug. It is found that co-injection of the PEGylated rapamycin nanoparticles and TCS could mitigate the formation of anti-TCS antibody via inducing durable immunological tolerance. Importantly, the combination of TCS and the rapamycin nanoparticles has an enhanced effect on inhibit the growth of breast cancer. This work provides a promising approach for protein toxin-based anticancer therapy and for promoting the clinical translation.

HLA-B*46:01:01:01 and HLA-DRB1*09:01:02:01 are associated with anti-rHuEPO-induced pure red cell aplasia

Treatment of anemia in patients with chronic kidney disease (CKD) with recombinant human erythropoietin (rHuEPO) can be disrupted by a severe complication, anti-rHuEPO-induced pure red cell aplasia (PRCA). Specific HLA genotypes may have played a role in the high incidence of PRCA in Thai patients (1.7/1,000 patient years vs. 0.03/10,000 patient years in Caucasians). We conducted a case-control study in 157 CKD patients with anti-rHuEPO-induced PRCA and 56 controls. The HLA typing was determined by sequencing using a highly accurate multiplex single-molecule, real-time, long-read sequencing platform. Four analytical models were deployed: Model 1 (additive: accounts for the number of alleles), Model 2 (dominant: accounts for only the presence or absence of alleles), Model 3 (adjusted additive with rHuEPO types) and Model 4 (adjusted dominant with rHuEPO types). HLA-B*46:01:01:01 and DRB1*09:01:02:01 were found to be independent risk markers for anti-rHuEPO-induced PRCA in all models [OR (95%CI), p-values for B*46:01:01:01: 4.58 (1.55-13.51), 0.006; 4.63 (1.56-13.75), 0.006; 5.72 (1.67-19.67), 0.006; and 5.81 (1.68-20.09), 0.005; for DRB1*09:01:02:01: 3.99 (1.28-12.49), 0.017, 4.50 (1.32-15.40), 0.016, 3.42 (1.09-10.74), 0.035, and 3.75 (1.08-13.07), 0.038, in Models 1-4, respectively. HLA-B*46:01:01:01 and DRB1*09:01:02:01 are susceptible alleles for anti-rHuEPO-induced PRCA. These findings support the role of HLA genotyping in helping to monitor patients receiving rHuEPO treatment.

A mechanistic marker-based screening tool to predict clinical immunogenicity of biologics

BACKGROUND

The efficacy and safety of therapeutic proteins are undermined by immunogenicity driven by anti-drug antibodies. Immunogenicity risk assessment is critically necessary during drug development, but current methods lack predictive power and mechanistic insight into antigen uptake and processing leading to immune response. A key mechanistic step in T-cell-dependent immune responses is the migration of mature dendritic cells to T-cell areas of lymphoid compartments, and this phenomenon is most pronounced in the immune response toward subcutaneously delivered proteins.

METHODS

The migratory potential of monocyte-derived dendritic cells is proposed to be a mechanistic marker for immunogenicity screening. Following exposure to therapeutic protein in vitro, dendritic cells are analyzed for changes in activation markers (CD40 and IL-12) in combination with levels of the chemokine receptor CXCR4 to represent migratory potential. Then a transwell assay captures the intensity of dendritic cell migration in the presence of a gradient of therapeutic protein and chemokine ligands.

RESULTS

Here, we show that an increased ability of the therapeutic protein to induce dendritic cell migration along a gradient of chemokine CCL21 and CXCL12 predicts higher immunogenic potential. Expression of the chemokine receptor CXCR4 on human monocyte-derived dendritic cells, in combination with activation markers CD40 and IL-12, strongly correlates with clinical anti-drug antibody incidence.

CONCLUSIONS

Mechanistic understanding of processes driving immunogenicity led to the development of a predictive tool for immunogenicity risk assessment of therapeutic proteins. These predictive markers could be adapted for immunogenicity screening of other biological modalities.

A competitive ligand binding assay for detection of neutralizing antibodies against an insulin analog

Biotherapeutics have the potential to trigger undesired immune responses in the patients. For therapeutic proteins, immunogenicity is manifested as anti-drug antibodies (ADA). Because ADA could compromise pharmacokinetics, efficacy, and safety, regulatory agencies require immunogenicity assessment during clinical development. A tiered bioanalytical approach is recommended to monitor clinical immunogenicity, and neutralizing antibodies (NAb) are studied in Tier 4 if the molecule is immunogenic. Although cell-based assays, which reflect the pharmacological mechanism of action, are in some cases the preferred assay format for detecting NAbs, they are associated with operational complexity and sometimes suboptimal assay performance. Alternatively, non-cell-based assays have also been developed and implemented. In our current study, a competitive ligand binding assay (CLBA) was developed to detect NAbs for insulin efsitora alfa (efsitora, basal insulin Fc, LY3209590), a novel fusion protein being studied for the treatment of Type 1 diabetes and Type 2 diabetes. The CLBA demonstrated acceptable sensitivity, drug tolerance, precision, and robustness, and thus provides a suitable approach for detecting NAbs against efsitora.

Targeting Progranulin as an Immuno-Neurology Therapeutic Approach

Immuno-neurology is an emerging therapeutic strategy for dementia and neurodegeneration designed to address immune surveillance failure in the brain. Microglia, as central nervous system (CNS)-resident myeloid cells, routinely perform surveillance of the brain and support neuronal function. Loss-of-function (LOF) mutations causing decreased levels of progranulin (PGRN), an immune regulatory protein, lead to dysfunctional microglia and are associated with multiple neurodegenerative diseases, including frontotemporal dementia caused by the progranulin gene (GRN) mutation (FTD-GRN), Alzheimer's disease (AD), Parkinson's disease (PD), limbic-predominant age-related transactivation response deoxyribonucleic acid binding protein 43 (TDP-43) encephalopathy (LATE), and amyotrophic lateral sclerosis (ALS). Immuno-neurology targets immune checkpoint-like proteins, offering the potential to convert aging and dysfunctional microglia into disease-fighting cells that counteract multiple disease pathologies, clear misfolded proteins and debris, promote myelin and synapse repair, optimize neuronal function, support astrocytes and oligodendrocytes, and maintain brain vasculature. Several clinical trials are underway to elevate PGRN levels as one strategy to modulate the function of microglia and counteract neurodegenerative changes associated with various disease states. If successful, these and other immuno-neurology drugs have the potential to revolutionize the treatment of neurodegenerative disorders by harnessing the brain's immune system and shifting it from an inflammatory/pathological state to an enhanced physiological/homeostatic state.

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.

Glycosylation shapes the efficacy and safety of diverse protein, gene and cell therapies

Over recent decades, therapeutic proteins have had widespread success in treating a myriad of diseases. Glycosylation, a near universal feature of this class of drugs, is a critical quality attribute that significantly influences the physical properties, safety profile and biological activity of therapeutic proteins. Optimizing protein glycosylation, therefore, offers an important avenue to developing more efficacious therapies. In this review, we discuss specific examples of how variations in glycan structure and glycoengineering impacts the stability, safety, and clinical efficacy of protein-based drugs that are already in the market as well as those that are still in preclinical development. We also highlight the impact of glycosylation on next generation biologics such as T cell-based cancer therapy and gene therapy.

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.

Immunoinformatic Risk Assessment of Host Cell Proteins During Process Development for Biologic Therapeutics

The identification and removal of host cell proteins (HCPs) from biologic products is a critical step in drug development. Despite recent improvements to purification processes, biologics such as monoclonal antibodies, enzyme replacement therapies, and vaccines that are manufactured in a range of cell lines and purified using diverse processes may contain HCP impurities, making it necessary for developers to identify and quantify impurities during process development for each drug product. HCPs that contain sequences that are less conserved with human homologs may be more immunogenic than those that are more conserved. We have developed a computational tool, ISPRI-HCP, that estimates the immunogenic potential of HCP sequences by evaluating and quantifying T cell epitope density and relative conservation with similar T cell epitopes in the human proteome. Here we describe several case studies that support the use of this method for classifying candidate HCP impurities according to their immunogenicity risk.

Statistical Approaches for Establishing Appropriate Immunogenicity Assay Cut Points: Impact of Sample Distribution, Sample Size, and Outlier Removal

The statistical assessments needed to establish anti-drug antibody (ADA) assay cut points (CPs) can be challenging for bioanalytical scientists. Poorly established CPs that are too high could potentially miss treatment emergent ADA or, when set too low, result in detection of responses that may have no clinical relevance. We evaluated 16 validation CP datasets generated with ADA assays at Regeneron's bioanalytical laboratory and compared results obtained from different CP calculation tools. We systematically evaluated the impact of various factors on CP determination including biological and analytical variability, number of samples for capturing biological variability, outlier removal methods, and the use of parametric vs. non-parametric CP determination. In every study, biological factors were the major component of assay response variability, far outweighing the contribution from analytical variability. Non-parametric CP estimations resulted in screening positivity in drug-naïve samples closer to the targeted rate (5%) and were less impacted by skewness. Outlier removal using the boxplot method with an interquartile range (IQR) factor of 3.0 resulted in screening positivity close to the 5% targeted rate when applied to entire drug-naïve dataset. In silico analysis of CPs calculated using different sample sizes showed that using larger numbers of individuals resulted in CP estimates closer to the CP of the entire population, indicating a larger sample size (~ 150) for CP determination better represents the diversity of the study population. Finally, simpler CP calculations, such as the boxplot method performed in Excel, resulted in CPs similar to those determined using complex methods, such as random-effects ANOVA.

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.

Derivatization with fatty acids in peptide and protein drug discovery

Peptides and proteins are widely used to treat a range of medical conditions; however, they often have to be injected and their effects are short-lived. These shortcomings of the native structure can be addressed by molecular engineering, but this is a complex undertaking. A molecular engineering technology initially applied to insulin - and which has now been successfully applied to several biopharmaceuticals - entails the derivatization of peptides and proteins with fatty acids. Various protraction mechanisms are enabled by the specific characteristics and positions of the attached fatty acid. Furthermore, the technology can ensure a long half-life following oral administration of peptide drugs, can alter the distribution of peptides and may hold potential for tissue targeting. Due to the inherent safety and well-defined chemical nature of the fatty acids, this technology provides a versatile approach to peptide and protein drug discovery.

Emerging principles of cytokine pharmacology and therapeutics

Cytokines are secreted signalling proteins that play essential roles in the initiation, maintenance and resolution of immune responses. Although the unique ability of cytokines to control immune function has garnered clinical interest in the context of cancer, autoimmunity and infectious disease, the use of cytokine-based therapeutics has been limited. This is due, in part, to the ability of cytokines to act on many cell types and impact diverse biological functions, resulting in dose-limiting toxicity or lack of efficacy. Recent studies combining structural biology, protein engineering and receptor pharmacology have unlocked new insights into the mechanisms of cytokine receptor activation, demonstrating that many aspects of cytokine function are highly tunable. Here, we discuss the pharmacological principles underlying these efforts to overcome cytokine pleiotropy and enhance the therapeutic potential of this important class of signalling molecules.

Development of Therapeutic Proteins for a New Subcutaneous Route of Administration after the Establishment of Intravenous Dosages: A Systematic Review

Therapeutic proteins may first be developed as intravenous (i.v.) therapies with new subcutaneous (s.c.) dosage forms being subsequently developed to provide an alternative route of administration. As of August 2022, there have been 9 therapeutic proteins which were developed as a new s.c. dosage form after the approval of the corresponding i.v. product. This article provides a systematic review of prior experiences in the i.v. to s.c. switch development programs. We describe what types of clinical studies were conducted to support the i.v. to s.c. switch for these nine therapeutic proteins. Publicly available scientific advice from health authorities is summarized, particularly regarding recommendations on overall development strategy, dose selection, immunogenicity assessment, and indication extrapolation. The clinical data from these i.v. to s.c. development programs demonstrate that: (1) when switching from i.v. dosing to s.c. dosing, trough drug concentration (C_trough ) from s.c. dosing should not be inferior to i.v. dosing with average drug concentration (C_avg ; equivalent to AUC, area under the curve after correcting for dosing intervals between i.v. and s.c. administration) being matched or non-inferior to i.v. dosing; and (2) with appropriate s.c. dose regimens, treatment with s.c. therapeutic proteins can generally achieve similar efficacy and safety as the corresponding i.v. products, suggesting that the much higher maximum concentration (C_max ) after i.v. infusion as compared with that from s.c. injection is often not relevant to the treatment effect.

Case report: Dynamic antibody monitoring in a case of anti-recombinant human erythropoietin-mediated pure red cell aplasia with prolonged course after kidney transplantation

Anti-erythropoietin (anti-EPO) antibody-mediated pure red cell aplasia (PRCA) is a rarely seen disease. Anti-EPO antibodies were mostly found in patients with chronic kidney disease who received recombinant human erythropoietin (rHuEPO) injections subcutaneously. The treatment against anti-EPO antibody-mediated PRCA included discontinuation of rHuEPO, immunosuppressive agents, intravenous immunoglobulin, plasmapheresis, or kidney transplantation. We reported a case of kidney transplant recipient with anti-EPO antibody-mediated PRCA, who had no trend of recovery after stopping rHuEPO, receiving regular induction and maintenance immunosuppressive regimens. He was further given 6 consecutive plasmapheresis sessions, cyclophosphamide, and adjusted maintenance immunosuppressive regimen into cyclosporine, sirolimus and prednisone. We monitored his anti-EPO antibody levels with a self-created simple mixing test. At 10 months post kidney transplant, his anti-EPO antibody finally turned negative, and his reticulocyte count dramatically increased. Cyclosporine, sirolimus and prednisone combined with roxadustat eventually alleviated the patient's anti-EPO antibody-mediated PRCA. Our self-created simple mixing test for anti-EPO antibody titer was very helpful in disease monitoring and therapeutic guidance.

Advancing mRNA technologies for therapies and vaccines: An African context

Synthetic mRNA technologies represent a versatile platform that can be used to develop advanced drug products. The remarkable speed with which vaccine development programs designed and manufactured safe and effective COVID-19 vaccines has rekindled interest in mRNA technology, particularly for future pandemic preparedness. Although recent R&D has focused largely on advancing mRNA vaccines and large-scale manufacturing capabilities, the technology has been used to develop various immunotherapies, gene editing strategies, and protein replacement therapies. Within the mRNA technologies toolbox lie several platforms, design principles, and components that can be adapted to modulate immunogenicity, stability, in situ expression, and delivery. For example, incorporating modified nucleotides into conventional mRNA transcripts can reduce innate immune responses and improve in situ translation. Alternatively, self-amplifying RNA may enhance vaccine-mediated immunity by increasing antigen expression. This review will highlight recent advances in the field of synthetic mRNA therapies and vaccines, and discuss the ongoing global efforts aimed at reducing vaccine inequity by establishing mRNA manufacturing capacity within Africa and other low- and middle-income countries.

Neutralization Activity of Anti-drug Antibodies Against a Biotherapeutic Can Be Predicted from a Comprehensive Pharmacokinetics, Pharmacodynamics, and Anti-drug Antibody Data Analysis

Historically, a neutralization antibody (NAb) assay is considered critical in immunogenicity assessment of biologic therapeutics, even with low anti-drug antibody (ADA) positive rates. In 2019, FDA new guidelines issued on immunogenicity testing acknowledged the possibility of using "a highly sensitive PD marker or an appropriately designed PK assay or both that generate data that inform clinical activity" to replace a NAb assay. In the current manuscript, we present data for PK, PD, and ADA assays which collectively succeed to replace the standalone NAb assay. The data include a total LC/MS-based PK assay, a serum neutralization antibody (SNA) assay that essentially measures pharmacodynamically functional PK and can detect NAb activity in the presence of 1:1 ratio of drug, and a highly drug-tolerant ADA assay. In addition, a model-based meta-analysis (MBMA) demonstrated that the ability of SNA assay to detect NAb at 1:1 ratio of drug is sensitive enough to monitor clinically meaningful efficacy change, which is 50% reduction of SNA titer. Our strategy of preparing a holistic data package discussed here may provide a roadmap to the community for alternatives in assaying neutralizing activity of ADA.

HLAII peptide presentation of infliximab increases when complexed with TNF

CD4+ T-cell activation through recognition of Human Leukocyte Antigen II (HLAII)-presented peptides is a key step in the development of unwanted immune response against biotherapeutics, such as the generation of anti-drug antibodies (ADA). Therefore, the identification of HLAII-presented peptides derived from biotherapeutics is a crucial part of immunogenicity risk assessment and mitigation strategies during drug development. To date, numerous CD4+ T-cell epitopes have been identified by HLAII immunopeptidomics in antibody-based biotherapeutics using either their native or aggregated form. Antibody-target immune complexes have been detected in patients with ADA and are thought to play a role in ADA development by enhancing the presentation of CD4+ T-cell epitopes at the surface of antigen presenting cells (APCs). The aim of this study was to investigate the effect of biotherapeutic antibody-target immune complexes on the HLAII peptide presentation of biotherapeutics in human primary monocyte-derived dendritic cells (DCs). The trimeric tumor necrosis factor (TNF) and its biotherapeutic antagonists infliximab (INFL), adalimumab (ADAL), and a single armed Fab' were used as a model system. The HLAII immunopeptidome of DCs loaded with antagonists or their immune complexes with TNF was analyzed by trapped ion mobility time-of-flight mass spectrometry (timsTOF MS) leading to the identification of ~ 12,000 unique HLAII-associated peptides per preparation. Anti-TNF sequences were detected at a median of 0.3% of the total immunopeptidome, against a majority background of peptides from endogenous and media-derived proteins. TNF antagonist presentation spanned the variable and constant regions in a widespread manner in both light and heavy chains, consistent with previously discovered HLAII peptides. This investigation extends the collection of observed HLAII peptides from anti-TNF biotherapeutics to include sequences that at least partially span the complementary determining regions (CDRs), such as the LCDR1 for both INFL and ADAL. Although antagonist presentation varied significantly across donors, peptides from both bivalent antagonists INFL and ADAL were more highly presented relative to the Fab'. While TNF immune complexes did not alter overall HLAII presentation, a moderate increase in presentation of a subset of peptide clusters was observed in the case of INFL-TNF, which included HCDR2, HCDR3 and LCDR2 sequences.

Detection of innate immune response modulating impurities (IIRMI) in therapeutic peptides and proteins: Impact of excipients

Unintended immunogenicity can affect the safety and efficacy of therapeutic proteins and peptides, so accurate assessments of immunogenicity risk can aid in the selection, development, and regulation of biologics. Product- and process- related impurities can act as adjuvants that activate the local or systemic innate immune response increasing the likelihood of product immunogenicity. Thus, assessing whether products have innate immune response modulating impurities (IIRMI) is a key component of immunogenicity risk assessments. Identifying trace levels of individual IIRMI can be difficult and testing individually for all potential impurities is not feasible. Therefore, to mitigate the risk, cell-based assays that use human blood cells or monocyte-macrophage reporter cell lines are being developed to detect minute quantities of impurities capable of eliciting innate immune activation. As these are cell-based assays, there is concern that excipients could blunt the cell responses, masking the presence of immunogenic IIRMI. Here, we explore the impact of frequently used excipients (non-ionic detergents, sugars, amino acids, bulking agents) on the sensitivity of reporter cell lines (THP-1- and RAW-Blue cells) and fresh human blood cells to detect purified TLR agonists as model IIRMI. We show that while excipients do not modulate the innate immune response elicited by TLR agonists in vivo, they can impact on the sensitivity of cell-based IIRMI assays. Reduced sensitivity to detect LPS, FSL-1, and other model IIRMI was also evident when testing 3 different recombinant drug products, product A (a representative mAb), B (a representative growth factor), C (a representative peptide), and their corresponding formulations. These results indicate that product formulations need to be considered when developing and validating cell-based assays for assessing clinically relevant levels of IIRMI in therapeutic proteins. Optimization of reporter cells, culture conditions and drug product concentration appear to be critical to minimize the impact of excipients and attain sensitive and reproducible assays.

Evaluating Antibody Pharmacokinetics as Prerequisite for Determining True Efficacy as Shown by Dual Targeting of PD-1 and CD96

One important prerequisite for developing a therapeutic monoclonal antibody is to evaluate its in vivo efficacy. We tested the therapeutic potential of an anti-CD96 antibody alone or in combination with an anti-PD-1 antibody in a mouse colon cancer model. Early anti-PD-1 treatment significantly decreased tumor growth and the combination with anti-CD96 further increased the therapeutic benefit, while anti-CD96 treatment alone had no effect. In late therapeutic settings, the treatment combination resulted in enhanced CD8⁺ T cell infiltration of tumors and an increased CD8/Treg ratio. Measured anti-PD-1 concentrations were as expected in animals treated with anti-PD-1 alone, but lower at later time points in animals receiving combination treatment. Moreover, anti-CD96 concentrations dropped dramatically after 10 days and were undetectable thereafter in most animals due to the occurrence of anti-drug antibodies that were increasing antibody clearance. Comparison of the anti-PD-1 concentrations with tumor growth showed that higher antibody concentrations in plasma correlated with better therapeutic efficacy. The therapeutic effect of anti-CD96 treatment could not be evaluated, because plasma concentrations were too low. Our findings strongly support the notion of measuring both plasma concentration and anti-drug antibody formation throughout in vivo studies, in order to interpret pharmacodynamic data correctly.

Biosimilars: Harmonizing the Approval Guidelines

Biosimilar approval guidelines need rationalization and harmonization to remove the inconsistencies and misconceptions to enable faster, safer, and more cost-effective biosimilars. This paper proposes a platform for a model guideline based on the scientific evaluation of the regulatory filings of the 130+ products approved in the US, UK, and EU and hundreds more in the WHO member countries. Extensive literature survey of clinical data published and reported, including Clinicaltrials.gov, a review of all current guidelines in the US, UK and EU, and WHO, and detailed discussions with the FDA have confirmed that removing the animal and clinical efficacy testing and fixing other minor approaches will enable the creation of a harmonized guideline that will best suit an ICH designation.

Successful Treatment of Antibody-mediated Pure Red Cell Aplasia Induced by Continuous Erythropoietin Receptor Activator with Prednisolone

Pure red cell aplasia (PRCA) associated with erythropoiesis-stimulating agents (ESAs), which were first reported in 1998, usually occurs with subcutaneous administration of epoetin alfa (Eprex^®). Improvements in ESA storage, handling, and administration methods have reduced the PRCA incidence. Continuous erythropoietin receptor activator (CERA) is a third-generation ESA that is rarely reported to induce PRCA. We herein report a case of CERA-induced PRCA presenting with positive anti-erythropoietin (EPO) and anti-CERA antibodies, which was successfully treated with prednisolone. Clinicians should be aware of the possibility of antibody-mediated PRCA induced by an ESA in CKD patients with anemia with reticulocytopenia and low serum EPO levels.

Interference in a Neutralizing Antibody Assay for Odronextamab, a CD20xCD3 Bispecific mAb, from Prior Rituximab Therapy and Possible Mitigation Strategy

A cell-based assay was developed to detect neutralizing anti-drug antibodies (NAbs) against odronextamab, a CD20xCD3 bispecific monoclonal antibody (mAb) under investigation for treatment of CD20+ B cell malignancies. In this assay, odronextamab bridges between two cell types, CD20-expressing HEK293 cells and CD3-expressing Jurkat T cells that generate a luciferase signal upon CD3 clustering. Patient samples containing NAbs directed to either arm of the bispecific drug block the odronextamab bridge formation between the cell lines thus preventing the generation of the luciferase signal. We determined that other anti-CD20 therapeutics also block bridge formation, resulting in false-positive results. In patient samples from odronextamab clinical trials, approximately 30% of baseline samples had a strong false-positive NAb signal that correlated with the presence of prior rituximab (anti-CD20) therapy. We determined that rituximab interference can be minimized by the addition of anti-rituximab antibodies in the NAb assay. Understanding and mitigating the impact of prior biologic exposure is increasingly important for implementing a successful bioanalytical strategy to support clinical drug development, especially in the immuno-oncology field.

Graphical Abstract

Odronextamab neutralizing antibody assay, interference, and mitigation. A Design of the odronextamab neutralizing antibody (NAb) assay where anti-CD20xCD3 drug bridges between CD20-expressing HEK293 cells and Jurkat T cells expressing an NFAT response element and luciferase reporter. True NAb prevents odronextamab from bridging between target and effector cells, thus preventing the expression of luciferase. B Interference with odronextamab from other anti-CD20 therapeutic antibodies (e.g., rituximab) from prior disease treatment generates a false-positive NAb result. Assay interference can be mitigated with an anti-idiotypic antibody against the interfering therapy.

Pre-existing Reactivity to an IgG4 Fc-Epitope: Characterization and Mitigation of Interference in a Bridging Anti-drug Antibody Assay

Twenty percent of baseline patient samples exhibited a pre-existing response in a bridging anti-drug antibody (ADA) assay for a human IgG4 monoclonal antibody (mAb) therapeutic. In some cases, assay signals were more than 100-fold higher than background, potentially confounding detection of true treatment-emergent ADA responses. The pre-existing reactivity was mapped by competitive inhibition experiments using recombinant proteins or chimeric human mAbs with IgG4 heavy chain regions swapped for IgG1 sequences. These experiments demonstrated that the majority of the samples had reactivity to an epitope containing leucine 445 in the CH3 domain of human IgG4. The pre-existing reactivity in baseline patient samples was mitigated by replacing the ADA assay capture reagent with a version of the drug containing a wild type IgG1 proline substitution at residue 445 without impacting detection of drug-specific, treatment-emergent ADA. Finally, purification on Protein G or anti-human IgG (H + L) columns indicated the pre-existing response was likely due to immunoglobulins in patient samples.

Graphical abstract

Development of a Liquid Chromatography and High-Resolution and -Accuracy Mass Spectrometry Method to Evaluate New Biotherapeutic Entity Processing in Human Liver Lysosomes

Biotherapeutic immunogenicity remains a great challenge for researchers because multiple factors trigger immune responses. Predicting and assessing the potential human immune response against biological drugs could represent an impressive breakthrough toward generating potentially safer and more efficacious therapeutic proteins. This article describes an in vitro assay that can contribute to evaluating the potential immunogenicity of biotherapeutics by focusing on lysosomal proteolysis. We selected human liver lysosomes (hLLs) from four different donors as a surrogate in vitro model instead of APC lysosomes because they are a ready-to-use lysosomal source. To assess the biological comparability of this surrogate to APC lysosomal extract, we compared the proteome content of hLLs with literature data of lysosomal fractions extracted from murine bone marrow and human blood-derived dendritic cells. Then we tested infliximab (IFX; Remicade) under different proteolytic conditions using liquid chromatography and high-resolution and -accuracy mass spectrometry to better define the degradation kinetics inside the lysosomes. hLLs revealed similar enzymatic content compared with human and murine dendritic cell lysosomes. Degradation assays demonstrated that our liquid chromatography and high-resolution and -accuracy mass spectrometry method could identify both the intact protein and the peptides resulting from proteolysis with high specificity and resolution. The rapid and easy assay described in this article can be extremely useful for evaluating the immunogenic risk associated with therapeutic proteins. In addition, this method can complement information from MHC class II-associated peptide proteomics assays and other in vitro and in silico techniques.

Cyclic thrombocytopenia related to erythropoietin-dependent anti-platelet anti-GPIV/IIIb antibody in hemodialysis

We describe herein the case of a 65-year-old patient on chronic hemodialysis with a medical history of idiopathic thrombocytopenia who experienced numerous episodes of severe thrombocytopenia with no specific diagnosis. Further analysis of the evolution of the platelet count showed that cyclic thrombocytopenia occurred after each injection of recombinant erythropoietin (rHu-EPO). Exploration of the involved mechanisms revealed the presence of a rHu-EPO-dependent anti-GPIV/IIIb antibody associated with a significant increase in GPIV/IIIb expression on her platelets after the addition of rHu-EPO. EPO was discontinued and the patient was treated with roxadustat with favorable results on her hemoglobin and platelet counts.

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.