Rapid in vitro assessment of the immunogenicity potential of engineered antibody therapeutics through detection of CD4+ T cell interleukin-2 secretion.

Therapeutic antibodies sometimes elicit anti-drug antibodies (ADAs) that can affect efficacy and safety. Engineered antibodies that contain artificial amino acid sequences are potentially highly immunogenic, but this is currently difficult to predict. Therefore, it is important to efficiently assess immunogenicity during the development of complex antibody-based formats. Here, we present an in vitro peripheral blood mononuclear cell-based assay that can be used to assess immunogenicity potential within 3 days. This method involves examining the frequency and function of interleukin (IL)-2-secreting CD4+ T cells induced by therapeutic antibodies. IL-2-secreting CD4+ T cells seem to be functionally relevant to the immunogenic potential due to their proliferative activity and the expression of several cytokines. The rates of the donors responding to low and high immunogenic proteins, mAb1, and keyhole limpet hemocyanin were 1.3% and 93.5%, respectively. Seven antibodies with known rates of immunogenicity (etanercept, emicizumab, abciximab, romosozumab, blosozumab, humanized anti-human A33 antibody, and bococizumab) induced responses in 1.9%, 3.8%, 6.4%, 10.0%, 29.2%, 43.8%, and 89.5% of donors, respectively. These data are comparable with ADA incidences in clinical settings. Our results show that this assay can contribute to the swift assessment and mechanistic understanding of the immunogenicity of therapeutic antibodies.

In vitro toxicological support to establish specification limit for anti-CD3 monospecific impurity in a bispecific T cell engager drug, ERY974.

An emerging structure for anti-tumor antibody drugs utilizes a bispecific antibody (BiAb) that recognizes a tumor surface antigen and CD3 on T cells. An impurity that commonly contaminates these BiAb products is an anti-CD3 monoclonal antibody (mAb). The most plausible cause of toxic activity by an anti-CD3 mAb is the induction of cytokines via T cell activation. In this in vitro study, we compared cytokine induction and T cell activation after treatment with an anti-glypican-3/CD3 BiAb (ERY974), anti-CD3 mAb impurity (aCD3), or ERY974 spiked with 5% aCD3. We found that contamination with up to 5% aCD3 did not affect cytokine release by ERY974. Cytokine levels induced by ERY974 in the presence of target cells were significantly higher than those induced by aCD3, but were very similar to those by the spiked treatment. The results supported the specification of a 5% limit for aCD3. OKT-3 had much higher activity to induce cytokines from peripheral blood mononuclear cells in an in vitro assay than aCD3. This suggests that specification limit should be decided for each type of anti-CD3 impurity that affects T cell-activating BiAb drug products. In vitro cytokine assays can provide useful information for determining these specification limits.

Human induced pluripotent stem cell-derived mast cells useful for in vitro mast cell activation assay exhibiting phenotypes and morphological characteristics of human mast cells.

Mast cells are key players in the inflammatory response with an important role in allergic reactions and are therefore useful for assessing the risk of anaphylaxis. However, they are difficult to isolate due to their low abundance and wide distribution. To overcome this, we generated and characterized mast cell-like cells derived from human induced pluripotent stem (hiPS) cells. These hiPS cell-derived mast cells (hiPS-MCs) were generated using recombinant human bone morphogenetic protein 4 (BMP4), vascular endothelial growth factor 165 (VEGF), stem cell factor (SCF), interleukin-4 (IL-4), interleukin-6 (IL-6), and interleukin-9 (IL-9) in a StemPro-34 medium. The hiPS-MCs exhibited the morphological characteristics of human mast cells, expressing high affinity-IgE receptor (FcεRI) and mast cell markers such as tryptase, chymase, and CD117. In addition, FcεRI stimulation with agonistic anti-IgE functionally increased the expression of activation markers CD63 and CD203c, as well as the amount of released histamine. We think the hiPS-MCs generated in this study will be useful for assessing the pharmacology and toxicity of anti-allergy medicines.

In vitro human helper T-cell assay to screen antibody drug candidates for immunogenicity.

Monoclonal antibody (mAb) drugs offer a number of valuable treatments. Many newly developed mAb drugs include artificial modification of amino acid sequences from human origin, which may cause higher immunogenicity to induce anti-drug antibodies (ADA). If the immunogenicity of a new candidate can be understood in the nonclinical phase, clinical studies will be safer and the success rate of development improved. Empirically, in vitro immunogenicity assays with human cells have proved to be sufficiently sensitive to nonhuman proteins, but not to human/humanized mAb. To detect the weaker immunogenicity of human-based mAb, a more sensitive biomarker for in vitro assays is needed. The in vitro study here developed a proliferation assay (TH cell assay) using flow cytometry analysis that can detect a slight increase in proliferating TH cells. Samples from 218 donors treated with a low-immunogenic drug (etanercept) were measured to determine a positive threshold level. With this threshold, positive donor percentages among PBMC after treatment with higher-immunogenicity mAb drugs were noted, that is, 39.5% with humanized anti-human A33 antibody (hA33), 27.3% with abciximab, 25.9% with adalimumab, and 14.8% with infliximab. Biotherapeutics with low immunogenicity yielded values of 0% for basiliximab and 3.7% for etanercept. These data showed a good comparability with previously reported incidences of clinical ADA with the evaluated drugs. Calculations based on the data here showed that a TH cell assay with 40 donors could provide statistically significant differences when comparing low- (etanercept) versus highly immunogenic mAb (except for infliximab). Based on the outcomes here, for screening purposes, a practical cutoff point of 3/20 positives with 20 donors was proposed to alert immunogenicity of mAb drug candidates.

Sigma-1 receptor stimulation by dehydroepiandrosterone ameliorates cognitive impairment through activation of CaM kinase II, protein kinase C and extracellular signal-regulated kinase in olfactory bulbectomized mice.

Dehydroepiandrosterone (DHEA) is one of the most abundant neurosteroids synthesized de novo in the CNS. We here found that sigma-1 receptor stimulation by DHEA improves cognitive function through phosphorylation of synaptic proteins in olfactory bulbectomized (OBX) mouse hippocampus. We have previously reported that calcium/calmodulin-dependent protein kinase II (CaMKII), protein kinase C (PKC) and extracellular signal-regulated kinase (ERK) were impaired in OBX mouse hippocampus. OBX mice were administered once a day for 7-8 days with DHEA (30 or 60 mg/kg p.o.) 10 days after operation. The spatial, cognitive and conditioned fear memories in OBX mice were significantly improved as assessed by Y-maze, novel object recognition and passive avoidance task, respectively. DHEA also improved impaired hippocampal long-term potentiation in OBX mice. Notably, DHEA treatment restored PKCα (Ser-657) autophosphorylation and NR1 (Ser-896) and myristoylated alanine-rich protein kinase C substrate (Ser-152/156) phosphorylation to the control levels in the hippocampal CA1 region. Likewise, DHEA treatment improved CaMKIIα (Thr-286) autophosphorylation and GluR1 (Ser-831) phosphorylation to the control levels in the CA1 region. Furthermore, DHEA treatment improved ERK and cAMP-responsive element-binding protein (Ser-133) phosphorylation to the control levels. Finally, NE-100, sigma-1 receptor antagonist, significantly inhibited the DHEA-induced improvement of memory-related behaviors and CaMKII, PKC and ERK phosphorylation in CA1 region. Taken together, sigma-1 receptor stimulation by DHEA ameliorates OBX-induced impairment in memory-related behaviors and long-term potentiation in the hippocampal CA1 region through activation of CaMKII, PKC and ERK.