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.

First-in-human clinical trial to assess pharmacokinetics, pharmacodynamics, safety, and tolerability of iscalimab, an anti-CD40 monoclonal antibody.

Iscalimab is a fully human, CD40 pathway blocking, nondepleting monoclonal antibody being developed as an immunosuppressive agent. We describe a first-in-human, randomized, double-blind, placebo-controlled study investigating the safety, tolerability, pharmacokinetics, and pharmacodynamics of iscalimab in healthy subjects and rheumatoid arthritis patients. Healthy subjects (n = 56) received single doses of intravenous iscalimab (0.03, 0.1, 0.3, 1, or 3 mg/kg), or subcutaneous iscalimab (3 mg/kg), or placebo. Rheumatoid arthritis patients (n = 20) received single doses of intravenous iscalimab (10 or 30 mg/kg) or placebo. Iscalimab exhibited target-mediated drug disposition resulting in dose-dependent and nonlinear pharmacokinetics. Complete (≥90%) CD40 receptor occupancy on whole blood B cells was observed at plasma concentrations >0.3-0.4 µg/mL. In subjects receiving 3 mg/kg iscalimab, antibody responses to keyhole limpet hemocyanin were transiently suppressed. CD40 occupancy by iscalimab prevented ex vivo human rCD154-induced expression of CD69 on B cells in whole blood. All doses were generally safe and well tolerated, with no clinically relevant changes in any safety parameters, including no evidence of thromboembolic events. Iscalimab appears to be a promising blocker of the CD40-CD154 costimulatory pathway with potential use in transplantation and other autoimmune diseases.

Clinical Pharmacology of Tisagenlecleucel in B-cell Acute Lymphoblastic Leukemia.

PURPOSE: Tisagenlecleucel is an anti-CD19 chimeric antigen receptor (CAR19) T-cell therapy approved for the treatment of children and young adults with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL). PATIENTS AND METHODS: We evaluated the cellular kinetics of tisagenlecleucel, the effect of patient factors, humoral immunogenicity, and manufacturing attributes on its kinetics, and exposure-response analysis for efficacy, safety and pharmacodynamic endpoints in 79 patients across two studies in pediatric B-ALL (ELIANA and ENSIGN). RESULTS: Using quantitative polymerase chain reaction to quantify levels of tisagenlecleucel transgene, responders (N = 62) had ≈2-fold higher tisagenlecleucel expansion in peripheral blood than nonresponders (N = 8; 74% and 104% higher geometric mean Cmax and AUC0-28d, respectively) with persistence measurable beyond 2 years in responding patients. Cmax increased with occurrence and severity of cytokine release syndrome (CRS). Tisagenlecleucel continued to expand and persist following tocilizumab, used to manage CRS. Patients with B-cell recovery within 6 months had earlier loss of the transgene compared with patients with sustained clinical response. Clinical responses were seen across the entire dose range evaluated (patients ≤50 kg: 0.2 to 5.0 × 106/kg; patients >50 kg: 0.1 to 2.5 × 108 CAR-positive viable T cells) with no relationship between dose and safety. Neither preexisting nor treatment-induced antimurine CAR19 antibodies affected the persistence or clinical response. CONCLUSIONS: Response to tisagenlecleucel was associated with increased expansion across a wide dose range. These results highlight the importance of cellular kinetics in understanding determinants of response to chimeric antigen receptor T-cell therapy.

Nonclinical Safety Assessment of CFZ533, a Fc-Silent Anti-CD40 Antibody, in Cynomolgus Monkeys.

CFZ533 is a pathway blocking, nondepleting anti-CD40 antibody that is in clinical development for inhibition of transplant organ rejection and therapy for autoimmune diseases. A 26-week GLP toxicity study in sexually mature Cynomolgus monkeys was conducted in order to support chronic application of CFZ533. CFZ533 was subcutaneously administered at doses up to 150 mg/kg/week and was safe and generally well tolerated. CFZ533 showed no adverse effects for cardiovascular, respiratory, and neurobehavioral endpoints, and no changes were observed for blood lymphocyte and platelet counts or blood coagulation markers. In line with the nondepleting nature of CFZ533, CD20+ B cells in the blood were only marginally reduced. A complete suppression of germinal center (GC) development in lymph nodes and spleen was the most prominent result of post-mortem histological investigations. This was corroborated by an abrogated T-dependent antibody response (TDAR) to the antigen Keyhole Limpet Hemocyanin (KLH) as well as an absence of anti-drug antibodies (ADAs) in the absence of B cell depletion as seen with immunophenotyping and histology. When serum levels of CFZ533 in recovery animals dropped levels necessary for full CD40 occupancy on B cells, all animals were able to mount a TDAR to KLH. All histological changes also reverted to normal appearance after recovery. In summary, CFZ533 was shown to be well tolerated and safe in the 26-week toxicity study with a distinct pharmacodynamic profile in histology and immune function.

Characterization of the in vitro and in vivo properties of CFZ533, a blocking and non-depleting anti-CD40 monoclonal antibody.

The CD40-CD154 costimulatory pathway is essential for T cell-dependent immune responses, development of humoral memory, and antigen presenting cell function. These immune functions have been implicated in the pathology of multiple autoimmune diseases as well as allograft rejection. We have generated CFZ533, a fully human, pathway blocking anti-CD40 monoclonal antibody that has been modified with a N297A mutation to render it unable to mediate Fcγ-dependent effector functions. CFZ533 inhibited CD154-induced activation of human leukocytes in vitro, but failed to induce human leukocyte activation. Additionally, CFZ533 was unable to mediate depletion of human CD40 expressing B cells. In vivo, CFZ533 blocked primary and recall T cell-dependent antibody responses in nonhuman primates and abrogated germinal formation without depleting peripheral blood B cells. We also established a relationship between plasma concentrations of CFZ533 and CD40 pathway-relevant pharmacodynamic effects in tissue. Collectively these data support the scientific rationale and posology for clinical utility of this antibody in select autoimmune diseases and solid organ transplantation.

Feedback from the European Bioanalysis Forum: focus workshop on current analysis of immunogenicity: best practices and regulatory hurdles.

European Bioanalysis Forum Workshop, Lisbon, Portugal, September 2016: At the recent European Bioanalysis Forum Focus Workshop, 'current analysis of immunogenicity: best practices and regulatory hurdles', several important challenges facing the bioanalytical community in relation to immunogenicity assays were discussed through a mixture of presentations and panel sessions. The main areas of focus were the evolving regulatory landscape, challenges of assay interferences from either drug or target, cut-point setting and whether alternative assays can be used to replace neutralizing antibody assays. This workshop report captures discussions and potential solutions and/or recommendations made by the speakers and delegates.

Evaluation of dried blood spots for the quantification of therapeutic monoclonal antibodies and detection of anti-drug antibodies.

BACKGROUND: Recently, the potential of dried blood spots (DBS) for small-molecule bioanalysis by LC-MS has been explored. The goal of this investigation was to evaluate the use of DBS for the quantification of biologics, where bioanalysis is with immunoassay. RESULTS: Therapeutic monoclonal antibodies were successfully eluted from DBS and detected by immunoassays, and the procedure could be validated in alignment with current guidelines. Accuracy, precision, selectivity and dilution linearity were all within the acceptance criteria currently used for the validation of binding assays with serum samples. Serum and DBS samples obtained in parallel during a PK research study in rats were analyzed for drug and anti-drug antibodies using AlphaLISA(®) technology. Drug concentrations in both sample types showed a strong correlation, and there was very good alignment in detection of immunogenicity positive animals. CONCLUSION: Using two examples, we have demonstrated that therapeutic monoclonal antibodies can be accurately quantified in DBS, and since anti-drug antibodies could also be successfully detected, there is scope for application of DBS to preclinical and clinical bioanalysis of monoclonal antibody drugs and anti-drug antibodies.

Improvement of drug tolerance in immunogenicity testing by acid treatment on Biacore.

Detection of anti-drug antibodies (ADA) can be difficult, if not impossible, in the presence of drug in the sample. This is a particular concern with therapeutic monoclonal antibodies (mAbs), which have typically longer half-lives than other proteins. For detection of ADA in presence of high drug concentrations, assay choice is limited to ELISA-like methods, capable of incorporating acid dissociation procedures to separate drug-ADA immune complexes. To our knowledge, Biacore assays have not been shown to be directly compatible with acid dissociation procedures, until now. As a consequence, steps to ensure adequate clearance of the drug are prerequisite to enable sensitive detection of ADA. Here we describe the development of a novel, rapid and highly drug tolerant Biacore method that uses an acid dissociation step to detect ADA in the presence of excess drug in human serum. Removal of drug after acid treatment is not required.

Characterization of macrophage subpopulations and microvessel density in carcinomas of the gastrointestinal tract.

BACKGROUND: The role of tumor associated macrophages (TAMs) in tumor angiogenesis and inflammation and the interactions between TAMs and tumor cells as well as lymphocytes appear to be critical factors in the development and progression of cancer. PATIENTS AND METHODS: Carcinomas of the gastrointestinal tract have been analysed by tissue microarrays. TAMs and vessels were characterized by immunohistochemistry using the antibodies PG-M1, KP1, MRP8, MRP14, MRP8/14 and CD31, CD34, respectively. RESULTS: The number of all macrophages was significantly higher and lymphocyte densities were lower in tumor tissues than in tumor-free tissues. The MRP-antibodies identified a minority population of macrophages and a low numbers of these macrophages tended to occur in more advanced cancers. There was a positive correlation between the number of macrophages and the number of microvessels in all tumors, but no correlation between macrophages and vessel counts in tumor-free tissues. CONCLUSION: The results indicated a suppressed immune response towards the tumors. The observed common characteristics regarding macrophage attraction, lymphocyte suppression and microvessel density suggested that these mechanisms are regulated similarly in all carcinomas of the GI-tract.

Multiple tumor marker analyses (PSA, hK2, PSCA, trp-p8) in primary prostate cancers using quantitative RT-PCR.

The identification of new diagnostic markers and potential treatment targets for prostate carcinoma (PCa) necessitates the evaluation of expression patterns in both malignant and non-malignant tissue specimens. In this study, we compared the mRNA expression of recently identified prostate-associated genes, prostate stem cell antigen (PSCA) and transient receptor potential p8 (trp-p8), to the mRNA expression of the most commonly used markers for PCa, prostate-specific antigen (PSA) and human kallikrein 2 (hK2). For these four candidates we performed highly specific quantitative real-time LightCycler RT-PCR assays with cDNA originating from matched tissue specimens of 40 patients with primary PCa. The highest transcript amounts were found for PSA in malignant as well as in non-malignant tissue specimens followed by hK2, trp-p8 and PSCA with an mRNA expression remarkably lower. The relative transcript levels of PSA, hK2 and trp-p8 were elevated in malignant in comparison to non-malignant tissues, but only for trp-p8 this increased expression was statistically significant. Focussing on organ confined tumors, we found a significant difference of the mRNA expression of PSA and trp-p8 between malignant and non-malignant tissue specimens. The marker trp-p8 is also suited to differentiate between the tumor stages when quantifying its transcript levels within tumor tissue specimens. The evaluation of the mRNA expression patterns of these markers by quantitative real-time RT-PCR could provide new tools for differential diagnosis and molecular staging. According to our data, the novel marker trp-p8 seems to represent a highly prostate-specific and PCa-associated gene qualifying it as a potential target for specific therapies.