2021 White Paper on Recent Issues in Bioanalysis: TAb/NAb, Viral Vector CDx, Shedding Assays; CRISPR/Cas9 & CAR-T Immunogenicity; PCR & Vaccine Assay Performance; ADA Assay Comparability & Cut Point Appropriateness (Part 3 - Recommendations on Gene Therapy, Cell Therapy, Vaccine Assays; Immunogenicity of Biotherapeutics and Novel Modalities; Integrated Summary of Immunogenicity Harmonization).

The 15th edition of the Workshop on Recent Issues in Bioanalysis (15th WRIB) was held on 27 September to 1 October 2021. Even with a last-minute move from in-person to virtual, an overwhelmingly high number of nearly 900 professionals representing pharma and biotech companies, contract research organizations (CROs), and multiple regulatory agencies still eagerly convened to actively discuss the most current topics of interest in bioanalysis. The 15th WRIB included 3 Main Workshops and 7 Specialized Workshops that together spanned 1 week in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on biomarker assay development and validation (BAV) (focused on clarifying the confusion created by the increased use of the term "Context of Use - COU"); mass spectrometry of proteins (therapeutic, biomarker and transgene); state-of-the-art cytometry innovation and validation; and, critical reagent and positive control generation were the special features of the 15th edition. This 2021 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop, and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2021 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 3) covers the recommendations on TAb/NAb, Viral Vector CDx, Shedding Assays; CRISPR/Cas9 & CAR-T Immunogenicity; PCR & Vaccine Assay Performance; ADA Assay Comparability & Cut Point Appropriateness. Part 1A (Endogenous Compounds, Small Molecules, Complex Methods, Regulated Mass Spec of Large Molecules, Small Molecule, PoC), Part 1B (Regulatory Agencies' Inputs on Bioanalysis, Biomarkers, Immunogenicity, Gene & Cell Therapy and Vaccine) and Part 2 (ISR for Biomarkers, Liquid Biopsies, Spectral Cytometry, Inhalation/Oral & Multispecific Biotherapeutics, Accuracy/LLOQ for Flow Cytometry) are published in volume 14 of Bioanalysis, issues 9 and 10 (2022), respectively.

Tisagenlecleucel immunogenicity in relapsed/refractory acute lymphoblastic leukemia and diffuse large B-cell lymphoma.

Tisagenlecleucel is indicated for pediatric and young adult patients with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL) and adult patients with r/r diffuse large B-cell lymphoma (DLBCL). The tisagenlecleucel chimeric antigen receptor (CAR) contains a murine single-chain variable fragment domain; we examined the effects of humoral and cellular immune responses to tisagenlecleucel on clinical outcomes using 2 validated assays. Data were pooled from the ELIANA (registered at www.clinicaltrials.gov as #NCT02435849) and ENSIGN (#NCT02228096) trials in r/r B-ALL (N = 143) and the JULIET trial (#NCT02445248) in r/r DLBCL (N = 115). Humoral responses were determined by flow cytometric measurement of anti-murine CAR19 (mCAR19) antibodies in serum. Cellular responses were determined using T-cell production of interferon-γ in response to 2 different pools of mCAR19 peptides. Pretreatment anti-mCAR19 antibodies were detected in 81% of patients with r/r B-ALL and 94% of patients with r/r DLBCL. Posttreatment anti-mCAR19 antibodies were higher than patient-specific baseline in 42% of r/r B-ALL and 9% of r/r DLBCL patients. Pretreatment and posttreatment anti-mCAR19 antibodies did not affect tisagenlecleucel cellular kinetics, including maximum concentration and persistence (r2 < 0.05), clinical response (day-28 response, duration of response, and event-free survival), and safety. T-cell responses were consistent over time, with net responses <1% at baseline and posttreatment time points in a majority of patients and no effect on transgene expansion or persistence or outcomes. Presence of baseline and/or posttreatment anti-mCAR19 antibodies or T-cell responses did not alter the activity of tisagenlecleucel in patients with r/r B-ALL or r/r DLBCL.

A cell-based immunogenicity assay to detect antibodies against chimeric antigen receptor expressed by tisagenlecleucel.

The use of T-cells expressing Chimeric Antigen Receptors (CARs) offers new opportunities for cancer treatment, as well as new challenges for the bioanalysis of this new class of drugs. The analysis of humoral immunogenicity (anti-drug antibodies) against CARs could be performed with a bridging ELISA, using labeled CAR fragments. However, outside of its native cell membrane environment and without potential interaction partners on the cell surface, a labeled or coated recombinant CAR fragment may structurally differ from the membrane-bound CAR expressed on CAR-T cells. Consequently, immunogenicity to CARs may be missed due to the artificial nature of a ligand binding assay setup. T-cell lines expressing the CAR offer the opportunity to measure anti-drug antibodies to the CAR in its natural cell environment, as an alternative to ligand-binding assays. Here we describe a novel, flow cytometry-based humoral immunogenicity assay for tisagenlecleucel (CTL019, Kymriah®) using a human T-cell line that expresses murine CAR19. The assay described here was fully validated according to health authority guidelines for the development and validation of immunogenicity assays and has a sensitivity of 100 ng/mL. A good correlation of screening assay signal strengths to titer assay results was observed while exploring options to increase titration assay throughput. Pre-existing antibodies against the cell line used in the assay as well as against the CAR itself complicate the assay and data interpretation.

Effect of interleukin-10 gene polymorphisms on clinical outcome of patients with aggressive non-Hodgkin's lymphoma: an exploratory study.

PURPOSE: Current chemotherapy can achieve high response rates in aggressive non-Hodgkin's lymphoma (NHL), but the factors that influence regression and survival remain unknown. The present exploratory study tested the hypothesis whether interleukin-10 (IL-10) polymorphisms predict clinical outcome, leukocytopenia, or infectivity during therapy. IL-10 was chosen because immune alterations are a major risk factor for NHL, and IL-10 is a cytokine involved in inflammatory processes associated with clinical outcome. EXPERIMENTAL DESIGN: Five hundred patients with aggressive NHL treated with CHOP/CHOEP were analyzed for IL-10 gene polymorphisms, including distal loci -7400InDel, -6752AT (rs6676671), and -6208CG (rs10494879) in comparison with proximal loci -3538AT (rs1800890), -1087AG (rs1800896), and -597AC (rs1800872) according to the incidence and outcome of the lymphoma. RESULTS: No differences in allele frequencies or haplotypes were found comparing a cohort of patients with aggressive NHL/diffuse large B-cell lymphoma with a healthy control group. Patients with aggressive NHL characterized by IL-10(-7400DelDel) had shorter overall survival periods compared with the other genotypes (P = 0.004). The 3-year rate is 43.4% for IL-10(-7400DelDel) and 73.4% for IL-10(-7400InIn) and IL-10(-7400InDel) together. A significant increased risk for event-free survival is found for carriers of the genotype IL-10(-6752TT-6208CC-3538AA) (P = 0.047). Multivariate analysis of IL-10(-7400) gene variation in relation to overall survival adjusted to international prognostic index revealed a relative risk of 1.9 for carriers of IL-10(-7400DelDel) (P = 0.037). No associations were found analyzing diffuse large B-cell lymphoma patients separately. CONCLUSION: Our results indicate that IL-10 gene variations could be associated to the clinical course of aggressive NHL, which points out the importance of host factors and respective genetic elements for treatment response.

Mdy2, a ubiquitin-like (UBL)-domain protein, is required for efficient mating in Saccharomyces cerevisiae.

MDY2, a gene required for efficient mating of the yeast Saccharomyces cerevisiae, was characterized in this study. The gene encodes a protein of 212 amino acids, which contains a ubiquitin-like (UBL) domain (residues 74-149). Deletion of MDY2 is associated with a five- to sevenfold reduction in mating efficiency, mainly due to defects in nuclear migration and karyogamy at the prezygotic stage. However, prior to mating pair fusion, shmoo formation is reduced by 30%, with a concomitant failure to form mating pairs. Strikingly, migration of the nucleus into the shmoo tip is also delayed or fails to occur. In addition, we show that in mdy2 mutants, microtubule bundles, as well as the microtubule end-binding protein Kar9, fail to localize properly to the shmoo tip, suggesting that the nuclear migration defect could be due to aberrant localization of Kar9. Pheromone signal transduction (as measured by FUS1 induction by alpha-factor) is not affected in mdy2delta mutants and mitosis is also normal in these cells. MDY2 is not induced by mating pheromone. In vegetatively growing cells, GFP-Mdy2 is localized in the nucleus, and remains nuclear after exposure of cells to alpha-factor. His-tagged Mdy2 shows no evidence of the C-terminal processing typical of ubiquitin, and also localizes to the nucleus. Thus MDY2 is a novel gene, whose product plays a role in shmoo formation and in nuclear migration in the pre-zygote, possibly by interacting with other UBL-type proteins that possess ubiquitin association (UBA) domains.