Antibody Constructs Research Articles

Bispecific T cell engager (BiTE®) antibody constructs can mediate bystander tumor cell killing.

For targets that are homogenously expressed, such as CD19 on cells of the B lymphocyte lineage, immunotherapies can be highly effective. Targeting CD19 with blinatumomab, a CD19/CD3 bispecific antibody construct (BiTE®), or with chimeric antigen receptor T cells (CAR-T) has shown great promise for treating certain CD19-positive hematological malignancies. In contrast, solid tumors with heterogeneous expression of the tumor-associated antigen (TAA) may present a challenge for targeted therapies. To prevent escape of TAA-negative cancer cells, immunotherapies with a local bystander effect would be beneficial. As a model to investigate BiTE®-mediated bystander killing in the solid tumor setting, we used epidermal growth factor receptor (EGFR) as a target. We measured lysis of EGFR-negative populations in vitro and in vivo when co-cultured with EGFR-positive cells, human T cells and an EGFR/CD3 BiTE® antibody construct. Bystander EGFR-negative cells were efficiently lysed by BiTE®-activated T cells only when proximal to EGFR-positive cells. Our mechanistic analysis suggests that cytokines released by BiTE®-activated T-cells induced upregulation of ICAM-1 and FAS on EGFR-negative bystander cells, contributing to T cell-induced bystander cell lysis.

Clinical applications and safety evaluation of the new CD19 specific T-cell engager antibody construct blinatumomab

ABSTRACTIntroduction: Blinatumomab is a T-cell engager antibody construct with dual specificity for CD19 and CD3, inducing serial lysis of CD19 positive B cells by redirecting cytotoxic T cells. It has been approved for the indication of Ph chromosome negative relapsed or refractory B-acute lymphoblastic leukemia (ALL), but has also been tested in ALL with minimal residual disease, relapsed Ph/BCR-ABL positive ALL, relapsed ALL in pediatric patients and relapsed or refractory non-Hodgkin’s lymphoma (NHL). Adverse events have been mainly related to infection and hematological toxicities, as well as cytokine release syndrome and neurotoxicity.Areas covered: The review will discuss mechanisms of action, published literature on efficacy in ALL and NHL, specific aspects of administration, frequent adverse events and practical management.Expert opinion: Blinatumomab represents an effective new treatment for highly resistant relapsed/refractory B-precursor ALL. Practical handling bears challenges due to application as four week continous infusion and specific adverse effects which can be well handled by experienced centers. Most promising outcomes are reported for patients with resistant disease but lower tumor load such as MRD positive ALL patients. Future studies will focus on the use of blinatumomab during first-line therapy and the role of stem cell transplantation after blinatumomab treatment.

Tyrosine kinase inhibition increases the cell surface localization of FLT3-ITD and enhances FLT3-directed immunotherapy of acute myeloid leukemia

The fms-related tyrosine kinase 3 (FLT3) receptor has been extensively studied over the past two decades with regard to oncogenic alterations that do not only serve as prognostic markers but also as therapeutic targets in acute myeloid leukemia (AML). Internal tandem duplications (ITDs) became of special interest in this setting as they are associated with unfavorable prognosis. Because of sequence-dependent protein conformational changes FLT3-ITD tends to autophosphorylate and displays a constitutive intracellular localization. Here, we analyzed the effect of tyrosine kinase inhibitors (TKIs) on the localization of the FLT3 receptor and its mutants. TKI treatment increased the surface expression through upregulation of FLT3 and glycosylation of FLT3-ITD and FLT3-D835Y mutants. In T cell-mediated cytotoxicity (TCMC) assays, using a bispecific FLT3 × CD3 antibody construct, the combination with TKI treatment increased TCMC in the FLT3-ITD-positive AML cell lines MOLM-13 and MV4-11, patient-derived xenograft cells and primary patient samples. Our findings provide the basis for rational combination of TKI and FLT3-directed immunotherapy with potential benefit for FLT3-ITD-positive AML patients.

DMAb inoculation of synthetic cross reactive antibodies protects against lethal influenza A and B infections

Influenza virus remains a significant public health threat despite innovative vaccines and antiviral drugs. A major limitation to current vaccinations and therapies against influenza virus is pathogenic diversity generated by shift and drift. A simple, cost-effective passive immunization strategy via in vivo production of cross-protective antibody molecules may augment existing vaccines and antiviral drugs in seasonal and pandemic outbreaks. We engineered synthetic plasmid DNA to encode two novel and broadly cross-protective monoclonal antibodies targeting influenza A and B. We utilized enhanced in vivo delivery of these plasmid DNA-encoded monoclonal antibody (DMAb) constructs and show that this strategy induces robust levels of functional antibodies directed against influenza A and B viruses in mouse sera. Mice receiving a single inoculation with anti-influenza A DMAb survive lethal Group 1 H1 and Group 2 H3 influenza A challenges, while inoculation with anti-influenza B DMAb yields protection against lethal Victoria and Yamagata lineage influenza B morbidity and mortality. Furthermore, these two DMAbs can be delivered coordinately resulting in exceptionally broad protection against both influenza A and B. We demonstrate this protection is similar to that achieved by conventional protein antibody delivery. DMAbs warrant further investigation as a novel immune therapy platform with distinct advantages for sustained immunoprophylaxis against influenza.

Abstract 55: Generation of half-life extended anti-CD33 BiTE® antibody constructs compatible with once-weekly dosing

Abstract T cell engaging bispecific antibody constructs (BiTE®), such as blinatumomab which targets CD19-positive cells, have shown great promise for treating certain CD19-positive hematological malignancies. Blinatumomab comprises a single chain Fv (scFv) that binds CD19 and a scFv that targets the T cell CD3 protein. The molecular weight of this “canonical” BiTE® is ~ 55 kDa, making it susceptible to kidney-mediated clearance and resulting in a short serum half-life (~ 4 hours). To maintain effective serum concentrations, canonical BiTE® antibody constructs must be administered by continuous IV (cIV) infusion. While there are many advantages associated with cIV administration (e.g., safety and uniform PK profile), patient convenience could be enhanced if the BiTE® antibody construct were compatible with once-weekly administration. To achieve this, the serum half-life of the BiTE® antibody construct would need to be extended. A canonical BiTE® targeting CD33 (AMG 330) is currently being evaluated in a phase I clinical trial. Like blinatumomab, AMG 330 is dosed cIV. To extend the serum half-life of AMG 330 and enable once-weekly dosing, several approaches were evaluated including fusion of AMG 330 to human albumin and Fc-containing moieties. Each of these half-life extended (HLE) constructs was evaluated in vitro, in mouse xenograft models and in non-human primates. In vitro assays evaluated 1) binding to both human and cynomolgus CD33 and CD3 proteins, and 2) cytotoxicity using human and cynomolgus target and effector cells. In each of these assays the canonical and HLE BiTE® antibody constructs demonstrated similar activity: single-digit nM binding and single digit pM cytotoxicity. Canonical and HLE BiTE® antibody constructs were subsequently evaluated in an orthotopic mouse model in which MOLM13 cells were administered IV and activated human T cells were administered IP two days later. The Fc-based HLE BiTE® antibody constructs provided a similar survival advantage when administered Q4D or Q5D as the canonical BiTE® when administered QD. However, the albumin fusion–based HLE BiTE® was less efficacious when administered Q4D than the QD- administered canonical BiTE®. Lastly, the PK/PD relationship was evaluated for each of the constructs in non-human primates. The serum half-lives varied from 6 hours for the canonical BiTE® to 44-167 hours for the HLE BiTE® antibody constructs. Each of the HLE BiTE® antibody constructs showed on-target depletion of CD33-positive monocytes and neutrophils in the blood and depletion of CD33-positive cells in the bone marrow. These data demonstrate that half-life extended BiTE® antibody constructs can be generated that retain comparable in vitro and in vivo activity as a canonical BiTE® and achieve a serum half-life compatible with once weekly dosing. Citation Format: Tara L. Arvedson, Mercedesz Balazs, Pamela Bogner, Kurt Black, Kevin Graham, Anja Henn, Matthias Friedrich, Patrick Hoffmann, Roman Kischel, Peter Kufer, Ralf Lutterbuese, Markus Muenz, Tobias Raum, Benno Rattel, Karen Rex, Dan Rock, Oliver Thomas, Joachim Wahl, Andreas Wolf, Angela Coxon. Generation of half-life extended anti-CD33 BiTE® antibody constructs compatible with once-weekly dosing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 55. doi:10.1158/1538-7445.AM2017-55

Abstract 3630: Preclinical evaluation of a BiTE® antibody construct with extended half-life that targets the tumor differentiation marker mesothelin

Abstract Bispecific T cell engager (BiTE®) antibody constructs redirect T cells to induce lysis of tumor cells. The anti-CD19/CD3 BiTE® Blincyto® can deplete target cells in both the blood and tissue compartment in B cell malignancies, suggesting that the BiTE® mechanism of action will also be effective against solid tumors. The tumor differentiation antigen mesothelin (MSLN) is an attractive target for the BiTE® approach. MSLN is highly expressed in >80% of ovarian and pancreatic tumors and mesothelioma. Expression of MSLN in normal tissues appears restricted to mesothelial cell surfaces such as the pleural, pericardial, and peritoneal layer. Here, we report the preclinical characterization of an anti-MSLN/CD3 BiTE® antibody construct with extended half-life. The BiTE® antibody construct binds MSLN and CD3 with low nM affinity and has low pM cytotoxic activity against MSLN-positive ovarian, pancreatic and lung cancer cell lines in vitro. Activity of the anti-MSLN/CD3 BiTE® antibody construct is observed at low effector to target cell ratios, and in cancer cells that express low levels of MSLN. This BiTE® antibody construct is also cytotoxic to cell lines that are resistant to chemotherapy. In mice, significant tumor growth inhibition of an established ovarian tumor xenograft model was achieved by IV dosing of the anti-MSLN/CD3 BiTE® antibody construct every 5 days. Pharmacokinetic evaluation of the anti-MSLN/CD3 BiTE® antibody construct in non-human primates demonstrated a half-life of 4-10 days. The potency and specificity of the anti-MSLN/CD3 BiTE® antibody construct, together with projected ability to dose once a week IV in humans, supports development of this BiTE® for treatment of MSLN-positive tumors. Citation Format: Alexander Sternjak, Fei Lee, Joachim Wahl, Dan Rock, Oliver Thomas, Sabine Stienen, Ralf Lutterbuese, Patrick Hoffmann, Tobias Raum, Peter Kufer, Benno Rattel, Angela Coxon, Matthias Friedrich, Julie Bailis. Preclinical evaluation of a BiTE® antibody construct with extended half-life that targets the tumor differentiation marker mesothelin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3630. doi:10.1158/1538-7445.AM2017-3630

Abstract 3632: BiTE® antibody constructs for the treatment of SCLC

Abstract Small cell lung cancer (SCLC) is a highly aggressive neuroendocrine tumor with a poor prognosis and limited therapeutic options. Most patients present with extensive stage disease, where recent advances in immunotherapies, including bi-specific T cell engager (BiTE®) antibody constructs, represent a promising new therapeutic approach. BiTE® molecules have demonstrated durable complete responses in the clinic in hematological malignancies. Similar to hematological malignancies, SCLC is also a widely-disseminated malignancy that shows very high response rate to first line therapies with high rates of disease recurrence, features which may support efficacy of the BiTE® modality. Next generation sequencing (NGS) identified Delta-like Ligand 3 (DLL3) as a highly specific tumor associated antigen for SCLC, with consistent expression in tumors and very low expression in normal tissues. Tumor expression of DLL3 protein was confirmed by IHC, with 30 of 35 SCLC tumors staining positive for DLL3. DLL3 BiTE® antibody constructs showed low pM potency in vitro and also demonstrated significant inhibition of tumor growth in vivo in an orthotopic model of SCLC. A half-life extended (HLE) BiTE® targeting DLL3 demonstrated antibody-like pharmacokinetic properties in single-dose studies in non-human primates (NHP), with a half-life of 11 days. This is predicted to support every other week dosing in humans. The combination of high potency and excellent PK properties suggests that HLE BiTE® molecules may provide a useful tool for targeting residual disease in SCLC patients whose tumors express DLL3. Citation Format: Michael J. Giffin, Ed K. Lobenhofer, Keegan Cooke, Tobias Raum, Jennitte Stevens, Pedro J. Beltran, Angela Coxon, Paul E. Hughes. BiTE® antibody constructs for the treatment of SCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3632. doi:10.1158/1538-7445.AM2017-3632

Immunotargeting relapsed or refractory precursor B-cell acute lymphoblastic leukemia - role of blinatumomab.

Patients with refractory or relapsed (R/R) acute lymphoblastic leukemia (ALL) have a dismal prognosis of around 5% long-term survival when treated with cytotoxic chemotherapy and allogenic stem cell transplantation. T-cell immunobased strategies open up new therapeutic perspectives. Blinatumomab is the first of a new class of antibody constructs that was labeled bispecific T-cell engager (BiTE): it consists of two single chain variable fragment connected with a flexible linker, one side binding CD3, the other CD19. The tight binding and the close proximity to the CD19-positive B-cells and leukemic cells leads to non-major histocompatibility complex-restricted T-cell activation, polyclonal T-cell expansion and direct target cell killing. Applied by continuous infusion, blinatumomab achieves morphological complete response rates ranging from 39% to 69% in R/R ALL patients (compared to 25% after second-line chemotherapy) with prolonged overall survival (blinatumomab median overall survival, 7.7 months vs chemotherapy, 4.0 months). In comparison to conventional cytotoxic second-line protocols blinatumomab has a favorable safety profile. The main adverse event is related to the mode of action of blinatumomab: the induction of a cytokine-release syndrome that can be managed by interruption and/or the application of steroids or tocilizumab. Another typical complication is the occurrence of neurological side effects, such as seizures and encephalopathy. This neurotoxicity is reversible after application of steroids and/or withdrawal of blinatumomab. Blinatumomab has proven to be a powerful therapeutic option in R/R ALL patients both adult and pediatric because of its efficacy and limited toxicity.

Exposure-adjusted adverse events (AEs) comparing blinatumomab to standard of care (SOC) chemotherapy in patients (pts) with relapsed/refractory B-precursor acute lymphoblastic leukemia (r/r ALL) from a randomized phase III study.

7032 Background: Blinatumomab (blin), a bispecific T-cell engaging antibody construct, has shown improved overall survival vs SOC in pts with r/r ALL in a randomized phase 3 study ( Haematologica 2016;101:S129). To better evaluate safety, we compared AEs of blin vs SOC after adjusting for varying treatment exposure times. Methods: Adults ≥ 18 yrs with r/r ALL (refractory, 1st relapse < 1 yr, ≥ 2 relapses or relapse after transplant) were randomized to receive blin or SOC (1 of 4 predefined regimens). Blin was dosed by continuous infusion (4 wks on/2 wks off) for up to 5 cycles (9 µg/d on d1−7 in cycle 1, then 28 µg/d); up to 4 maintenance cycles (4 wks on/8 wks off) were allowed for ≤ 12 mo. Exposure-adjusted (exp-adj) event rates were calculated as no. of events*100/total exposure time (Table). Results: Median (range) no. of cycles were 1 (1−4) for SOC and 2 (1−9) for blin. The highest exp-adj rates (per 100 pt-yrs) were for pyrexia (507 SOC vs 376 blin), anemia (987 vs 229), thrombocytopenia (750 vs 126) and neutropenia (351 vs 121), all lower in blin. Febrile neutropenia (365 vs 93) and infections (1216 vs 436) were also both lower in blin (p < 0.0001). Exp-adj rates for neurologic events were 743 SOC vs 472 blin, with median time (range) to onset of 7 (1−43) d and 7 (1−190) d, respectively, and gr ≥ 3 cytokine release syndrome (CRS) rates were 0 SOC vs 10 blin. The most frequent AEs in both cycles 1 and 2 were pyrexia, nausea and anemia in both arms; CRS events decreased in the blin arm between cycles 1 and 2 (14% vs 2%). Most fatal AEs were related to infection in both arms. Conclusions: Here blin showed an AE profile consistent with that previously reported for r/r ALL, including similar rates of manageable CRS and neurologic events. Exp-adj AE rates were generally higher in SOC vs blin, including for cytopenias and infections. Clinical trial information: NCT02013167. [Table: see text]

Blinatumomab use in pediatric patients (pts) with relapsed/refractory B-precursor acute lymphoblastic leukemia (r/r ALL) from an open-label, multicenter, expanded access study.

10530 Background:Blinatumomab (blin), a bispecific T-cell engaging antibody construct, has shown antileukemia activity and tolerability in pts with r/r ALL. We further evaluated safety and efficacy of blin in the first 40 pediatric pts with r/r ALL enrolled in an expanded access study (NCT02187354). Methods: Eligible pts (28 d to < 18 yrs) had ≥ 5% blasts and r/r ALL (refractory, ≥ 2 relapses or relapse after transplant [HCT]). Blin was dosed by continuous infusion (4 wks on/2 wks off) for up to 5 cycles (≥ 5 to < 25% blasts: 15 µg/m2/d; ≥ 25% blasts: 5 µg/m2/d on d1−7 in cycle 1, then 15 µg/m2/d). The primary endpoint was incidence of treatment-emergent (TE) and treatment-related (TR) adverse events (AEs); key efficacy endpoints were complete response (CR) and minimal residual disease (MRD, by PCR or flow cytometry) in the first 2 cycles, relapse-free survival, overall survival and HCT rate. Results: Of the first40 treated pts (median age, 9 [range, 1−17] yrs), 24 (60%) had ≥ 2 relapses, 20 (50%) relapsed after HCT and 5 (13%) were primary refractory; 18 (45%) had ≥ 50% blasts and 21 (53%) had prior HCT. Safety and key efficacy outcomes are shown in the table, including 63% CR in the first 2 cycles. There were 8 relapses and 20 deaths after treatment. Regardless of causality, the most frequent TEAEs were pyrexia (78%), cytokine release syndrome (CRS; 23%) vomiting (23%) and anemia (20%); all 9 CRS events were grade (gr) 1 or 2 and 1 tumor lysis syndrome was gr 3. 10 (25%) pts interrupted treatment and 2 (5%) discontinued due to TRAEs; 13 (33%) pts had gr ≥ 3 TRAEs, including 2 of 3 neurologic events (depressed level of consciousness and headache; both gr 3); 2 fatal AEs were considered unrelated to blin. Conclusions:Here single-agent blin showed antileukemia activity in pediatric pts with high-risk r/r ALL including t(17;19) and AEs consistent with those previously reported for r/r ALL. Clinical trial information: NCT02187354. [Table: see text]

Translation and Clinical Development of Bispecific T-cell Engaging Antibodies for Cancer Treatment.

Bispecific T‐cell Engagers (BiTE®) antibody constructs enable a polyclonal T‐cell response to cell‐surface tumor‐associated antigens, bypassing the narrow specificities of T‐cell receptors and the need for antigen presentation through the major histocompatibility complex pathways. Blinatumomab, a CD19xCD3 BiTE® antibody construct, received accelerated approval for the treatment of relapsed/refractory Philadelphia chromosome negative acute lymphoblastic leukemia. Herein we review the pharmacology, safety, and efficacy observed in studies of blinatumomab and other BiTE® antibody constructs. Quantitative systems pharmacology is envisioned as a means to optimize dosing decisions for trials in which BiTE® antibody constructs are administered as monotherapy or in combination with other immunotherapies.

Reconstruction of 3D structures of MET antibodies from electron microscopy 2D class averages.

Dynamics of three MET antibody constructs (IgG1, IgG2, and IgG4) and the IgG4-MET antigen complex was investigated by creating their atomic models with an integrative experimental and computational approach. In particular, we used two-dimensional (2D) Electron Microscopy (EM) images, image class averaging, homology modeling, Rapidly exploring Random Tree (RRT) structure sampling, and fitting of models to images, to find the relative orientations of antibody domains that are consistent with the EM images. We revealed that the conformational preferences of the constructs depend on the extent of the hinge flexibility. We also quantified how the MET antigen impacts on the conformational dynamics of IgG4. These observations allow to create testable hypothesis to investigate MET biology. Our protocol may also help describe structural diversity of other antigen systems at approximately 5 Å precision, as quantified by Root-Mean-Square Deviation (RMSD) among good-scoring models.

Clinical Pharmacology and Translational Aspects of Bispecific Antibodies.

Clinical Pharmacology and Translational Aspects of Bispecific Antibodies.

Targeting CD157 in AML using a novel, Fc-engineered antibody construct.

Antibody-based immunotherapy represents a promising strategy to eliminate chemorefractory leukemic cells in acute myeloid leukemia (AML). In this study, we evaluated a novel Fc-engineered antibody against CD157 (MEN1112) for its suitability as immunotherapy in AML. CD157 was expressed in 97% of primary AML patient samples. A significant, albeit lower expression level of CD157 was observed within the compartment of leukemia-initiating cells, which are supposed to be the major source of relapse. In healthy donor bone marrow, CD157 was expressed on CD34+ cells. In ex vivo assays, MEN1112 triggered natural killer (NK) cell-mediated cytotoxicity against AML cell lines and primary AML cells. Compared to its parental analogue, the Fc-engineered antibody exhibited higher antibody dependent cellular cytotoxicity responses. Using NK cells from AML patients, we observed heterogeneous MEN1112-mediated cytotoxicity against AML cells, most likely due to well-documented defects in AML-NK cells and corresponding inter-patient variations in NK cell function. Cytotoxicity could not be correlated to the time after completion of chemotherapy. In summary, we could demonstrate that CD157 is strongly expressed in AML. MEN1112 is a promising antibody construct that showed high cytotoxicity against AML cells and warrants further clinical testing. Due to variability in NK-cell function of AML patients, the time of application during the course of the disease as well as combinatorial strategies might influence treatment results.

Blinatumomab versus Chemotherapy for Advanced Acute Lymphoblastic Leukemia

BackgroundBlinatumomab, a bispecific monoclonal antibody construct that enables CD3-positive T cells to recognize and eliminate CD19-positive acute lymphoblastic leukemia (ALL) blasts, was approved for use in patients with relapsed or refractory B-cell precursor ALL on the basis of single-group trials that showed efficacy and manageable toxic effects.MethodsIn this multi-institutional phase 3 trial, we randomly assigned adults with heavily pretreated B-cell precursor ALL, in a 2:1 ratio, to receive either blinatumomab or standard-of-care chemotherapy. The primary end point was overall survival.ResultsOf the 405 patients who were randomly assigned to receive blinatumomab (271 patients) or chemotherapy (134 patients), 376 patients received at least one dose. Overall survival was significantly longer in the blinatumomab group than in the chemotherapy group. The median overall survival was 7.7 months in the blinatumomab group and 4.0 months in the chemotherapy group (hazard ratio for death with blinatumomab vs. chemotherapy, 0.71; 95% confidence interval [CI], 0.55 to 0.93; P=0.01). Remission rates within 12 weeks after treatment initiation were significantly higher in the blinatumomab group than in the chemotherapy group, both with respect to complete remission with full hematologic recovery (34% vs. 16%, P<0.001) and with respect to complete remission with full, partial, or incomplete hematologic recovery (44% vs. 25%, P<0.001). Treatment with blinatumomab resulted in a higher rate of event-free survival than that with chemotherapy (6-month estimates, 31% vs. 12%; hazard ratio for an event of relapse after achieving a complete remission with full, partial, or incomplete hematologic recovery, or death, 0.55; 95% CI, 0.43 to 0.71; P<0.001), as well as a longer median duration of remission (7.3 vs. 4.6 months). A total of 24% of the patients in each treatment group underwent allogeneic stem-cell transplantation. Adverse events of grade 3 or higher were reported in 87% of the patients in the blinatumomab group and in 92% of the patients in the chemotherapy group.ConclusionsTreatment with blinatumomab resulted in significantly longer overall survival than chemotherapy among adult patients with relapsed or refractory B-cell precursor ALL. (Funded by Amgen; TOWER ClinicalTrials.gov number, NCT02013167.)

Bispecific T cell engaging antibody constructs targeting a universally conserved part of the viral M2 ectodomain cure and prevent influenza A virus infection

The ectodomain of the influenza A matrix protein 2 (M2e) is highly conserved amongst all influenza virus A subtypes. M2e is present on the surface of influenza A virus-infected cells, and therefore a suitable target for broadly protective therapies. We designed bispecific T cell engaging (BiTE®) antibody constructs specific for M2e by genetically fusing a single chain variable fragment (scFv) derived from an M2e-specific murine monoclonal antibody with a CD3ɛ-specific scFv. These so-called FLU BiTE® antibody constructs selectively mediate T cell dependent lysis of M2-expressing and influenza A virus infected cells and protect BALB/c mice against challenge with different influenza A virus subtypes. By humanizing the M2e-binding scFv, we generated human-like FLU BiTE® antibody constructs, with increased in vitro cytotoxic activity and in vivo protective capacity against influenza A virus infection. FLU BiTE® antibody constructs represent a promising new curative and prophylactic treatment option for influenza disease.

Limitations of polyethylene glycol-induced precipitation as predictive tool for protein solubility during formulation development.

Polyethylene glycol (PEG)-induced protein precipitation is often used to extrapolate apparent protein solubility at specific formulation compositions. The procedure was used for several fields of application such as protein crystal growth but also protein formulation development. Nevertheless, most studies focused on applicability in protein crystal growth. In contrast, this study focuses on applicability of PEG-induced precipitation during high-concentration protein formulation development. In this study, solubility of three different model proteins was investigated over a broad range of pH. Solubility values predicted by PEG-induced precipitation were compared to real solubility behaviour determined by either turbidity or content measurements. Predicted solubility by PEG-induced precipitation was confirmed for an Fc fusion protein and a monoclonal antibody. In contrast, PEG-induced precipitation failed to predict solubility of a single-domain antibody construct. Applicability of PEG-induced precipitation as indicator of protein solubility during formulation development was found to be not valid for one of three model molecules. Under certain conditions, PEG-induced protein precipitation is not valid for prediction of real protein solubility behaviour. The procedure should be used carefully as tool for formulation development, and the results obtained should be validated by additional investigations.

Strategies for Bispecific Single Chain Antibody in Cancer Immunotherapy.

Genetic engineering has resulted in more than 50 recombinant bispecific antibody formats over the past two decades. Bispecific scFv antibodies represent a successful and promising immunotherapy platform that retargets cytotoxic T cells to tumor cells, with one scFv directed to tumor-associated antigens and the other to T cells. Based on this antibody construct, strategies for both specific tumor targeting and T cell activation are reviewed here. Three distinct types of tumor antigens are considered to optimize specificity and safety in bispecific scFv based treatment: cancer-testis antigens, neo-antigens and virus-associated antigens. In terms of T cell activation, although CD3 has been widely applied in bispecific scFvs being developed, CD28 and CD137 among co-stimulatory signals are also ideal candidates to be evaluated. Besides, LIGHT and HIV-Tat101 have drawn much attention as their potential roles in modulating antitumor responses.

An optical probe of synaptic plasticity.

An endogenous protein in the mouse brain is inactivated using a light-sensitive antibody construct.

Redirecting T cells to eradicate B-cell acute lymphoblastic leukemia: bispecific T-cell engagers and chimeric antigen receptors

Recent advances in antibody technology to harness T cells for cancer immunotherapy, particularly in the difficult-to-treat setting of relapsed/refractory acute lymphoblastic leukemia (r/r ALL), have led to innovative methods for directing cytotoxic T cells to specific surface antigens on cancer cells. One approach involves administration of soluble bispecific (or dual-affinity) antibody-based constructs that temporarily bridge T cells and cancer cells. Another approach infuses ex vivo-engineered T cells that express a surface plasma membrane-inserted antibody construct called a chimeric antigen receptor (CAR). Both bispecific antibodies and CARs circumvent natural target cell recognition by creating a physical connection between cytotoxic T cells and target cancer cells to activate a cytolysis signaling pathway; this connection allows essentially all cytotoxic T cells in a patient to be engaged because typical tumor cell resistance mechanisms (such as T-cell receptor specificity, antigen processing and presentation, and major histocompatibility complex context) are bypassed. Both the bispecific T-cell engager (BiTE) antibody construct blinatumomab and CD19-CARs are immunotherapies that have yielded encouraging remission rates in CD19-positive r/r ALL, suggesting that they might serve as definitive treatments or bridging therapies to allogeneic hematopoietic cell transplantation. With the introduction of these immunotherapies, new challenges arise related to unique toxicities and distinctive pathways of resistance. An increasing body of knowledge is being accumulated on how to predict, prevent, and manage such toxicities, which will help to better stratify patient risk and tailor treatments to minimize severe adverse events. A deeper understanding of the precise mechanisms of action and immune resistance, interaction with other novel agents in potential combinations, and optimization in the manufacturing process will help to advance immunotherapy outcomes in the r/r ALL setting.