Regulatory T cell targeting in cancer: Emerging strategies in immunotherapy.

The adaptive immune system is modulated by an important subset of CD4+ T lymphocytes called Treg cells that function in maintaining immune homeostasis by preventing excessive immune activation. Both deficiency and overactivation of Treg cell function can result in disease pathology. While loss of Treg function can lead to autoimmunity, an overabundance of Treg activity can promote tumorigenesis. Blocking and/or depleting Tregs has emerged as a viable strategy to enhance antitumor immunity. A major limitation underlying the limited efficacy observed with Treg therapies in the clinic is lack of selective targeting, often attributed to concurrent depletion of antitumor effector T-cell populations. Novel approaches to improve the specificity of Treg targeting in the context of cancer include the use of T-cell receptor mimic antibodies, bispecific antibodies, and near-infrared photoimmunotherapy. Next-generation technology platforms and transcriptomic/computational-based screening methods have been recently developed to identify preferential Treg targets. Herein, we highlight key advancements and challenges pertaining to the development of novel Treg targeting cancer therapeutics and discuss ongoing clinical trials evaluating next-generation Treg therapies for solid tumors.

Preclinical efficacy of humanized, non-FcγR-binding anti-CD3 antibodies in T-cell acute lymphoblastic leukemia.

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy that accounts for ∼20% of ALL cases. Intensive chemotherapy regimens result in cure rates >85% in children and <50% in adults, warranting a search of novel therapeutic strategies. Although immune-based therapies have tremendously improved the treatment of B-ALL and other B-cell malignancies, they are not yet available for T-ALL. We report here that humanized, non-Fcγ receptor (FcγR)-binding monoclonal antibodies (mAbs) to CD3 have antileukemic properties in xenograft (PDX) models of CD3+ T-ALL, resulting in prolonged host survival. We also report that these antibodies cooperate with chemotherapy to enhance antileukemic effects and host survival. Because these antibodies show only minor, manageable adverse effects in humans, they offer a new therapeutic option for the treatment of T-ALL. Our results also show that the antileukemic properties of anti-CD3 mAbs are largely independent of FcγR-mediated pathways in T-ALL PDXs.

Design and characterization of Zweimab and Doppelmab, high affinity dual antagonistic anti-TSLP/IL13 bispecific antibodies.

Patients with severe Th2 type asthma often have a steroid resistant phenotype and are prone to acute exacerbations. Current novel therapies have only marginal therapeutic effects. One of the hypotheses for lack of major efficacy in most patients is targeting only one redundant pathway leaving others active. Hence, we have designed and developed novel highly potent bispecific anti-TSLP/IL13 antibodies called Zweimabs (monovalent bispecific) and Doppelmabs (bivalent bispecific) that concurrently inhibits the signaling by these two cytokines.

Efficient Qualitative and Quantitative Determination of Antigen-induced Immune Responses.

To determine the effectiveness of immunization strategies used in therapeutic antibody or vaccine development, it is critical to assess the quality of immunization-induced polyclonal antibody responses. Here, we developed a workflow that uses sensitive methods to quantitatively and qualitatively assess immune responses against foreign antigens with regard to antibody binding affinity and epitope diversity. The application of such detailed assessments throughout an immunization campaign can significantly reduce the resources required to generate highly specific antibodies. Our workflow consists of the following two steps: 1) the use of surface plasmon resonance to quantify antigen-specific antibodies and evaluate their apparent binding affinities, and 2) the recovery of serum IgGs using an automated small scale purification system, followed by the determination of their epitope diversity using hydrogen deuterium exchange coupled with mass spectrometry. We showed that these methods were sensitive enough to detect antigen-specific IgGs in the nanogram/µl range and that they provided information for differentiating the antibody responses of the various immunized animals that could not be obtained by conventional methods. We also showed that this workflow can guide the selection of an animal that produces high affinity antibodies with a desired epitope coverage profile, resulting in the generation of potential therapeutic monoclonal antibody clones with desirable functional profiles. We postulate that this workflow will be an important tool in the development of effective vaccines to combat the highly sophisticated evasion mechanisms of pathogens.

Endoscopic Endonasal Dacryocystorhinostomy under Local Anesthesia or Assisted Local Anesthesia.

INTRODUCTION: Endoscopic Endonasal Dacryocystorhinostomy (EENDCR) is effective, safe and less time consuming procedure and scar free to manage patients with epiphora. Traditionally, EENDCR is performed under general anesthesia. Limited general anesthesia facility in our country has made EENDCR surgery limited to the hospitals with GA facilities. EENDCR surgery under local or assisted local anesthesia could be an alternative solution. The aim of the study was to study the pain tolerability of the patient undergoing EENDCR under local anesthesia (LA) or assisted local anesthesia (ALA). To the best of our knowledge, there is a lack of similar studies in Nepal. MATERIALS AND METHODS: This was a prospective, nonrandomized, interventional study done at a tertiary eye care center. After sample collection the study was aimed to evaluate the pain tolerability of patients undergoing EENDCR under LA or ALA. The case collection and the surgery were done by a single surgeon from 2018 Jan- 2019 April and followed for 6 to 24 months. All consecutive cases were enrolled in the study. Informed consent was obtained from all the patients. Inclusion criteria included chronic dacryocystitis with NLDO (Nasolacrimal duct obstruction), lacrimal sac mucocele and lacrimal sac pyocele. Previously failed DCR surgery was not included in the study. Total of 100 patients of EENDCR with a tube who completed a minimum 6 months follow up postoperatively were included in the study. Verbal rating scale (VRS) was used to report response to pain during different steps of surgery. RESULTS: There were 100 patients within the age range of 13-41 years of age. One hundred and six EENDCR were performed on 100 patients. Eighty-seven patients were adult (19-41) years and 13 patients were of pediatrics age group (13-18) years. There were 74 female and 26 male patients. Thirty-seven were RE (right eye), 57 were LE (Left eye) and 6 were BL (bilateral). Duration of illness was less than 6 months in 9 patients and more than 6 months in 91 patients. Ninety-two eyes were operated under LA and fourteen eyes of 11 patients asked for sedation in addition to local anesthesia (ALA). Patients reported pain during the creation of the bony ostium with Keryson's rounger (24 eyes, VRS 3-4) and while using the drill (19 eyes, VRS 5-6). On pain scoring, there was no pain (0-2) in patients who underwent EENDCR under ALA. Pain scoring in patients who underwent EENDCR under LA showed no pain (0-2) in 51.08%, mild pain (3-4) in 26.08%, and moderate pain (5-6) in 20.65%. Duration of surgery ranged from 15 to 45 minutes. Duration of follow up was 6- 24 months. There was a 96.2% success rate in this study. CONCLUSION: EENDCR can be done under LA or ALA depending on the indication and demand of the patient.

Conduit CAR: Redirecting CAR T-Cell Specificity with A Universal and Adaptable Bispecific Antibody Platform.

The success of chimeric antigen receptor (CAR) T-cell therapy against hematologic malignancies has altered the treatment paradigm for patients with these diseases. Nevertheless, the occurrence of relapse due to antigen escape or heterogeneous antigen expression on tumors remains a challenge for first-generation CAR T-cell therapies as only a single tumor antigen can be targeted. To address this limitation and to add a further level of tunability and control to CAR T-cell therapies, adapter or universal CAR T-cell approaches use a soluble mediator to bridge CAR T cells with tumor cells. Adapter CARs allow simultaneous or sequential targeting of multiple tumor antigens, control of immune synapse geometry, dose control, and the potential for improved safety. Herein, we described a novel CAR T-cell adapter platform that relies on a bispecific antibody (BsAb) targeting both a tumor antigen and the GGGGS (G4S) linker commonly used in single-chain Fv (ScFv) domains expressed on CAR T-cell surfaces. We demonstrated that the BsAb can bridge CAR T cells to tumor cells and potentiate CAR T-cell activation, proliferation, and tumor cell cytolysis. The cytolytic activity of CAR T-cells was redirected to different tumor antigens by changing the BsAb in a dose-dependent manner. This study highlights the potential of G4S-displaying CAR T cells to be redirected to engage alternative tumor-associated antigens (TAA). Significance: New approaches are needed to address relapsed/refractory disease and manage potential toxicities associated with CAR T-cell therapy. We describe an adapter CAR approach to redirect CAR T cells to engage novel TAA-expressing cells via a BsAb targeting a linker present on many clinical CAR T-cell therapeutics. We anticipate the use of such adapters could increase CAR T-cell efficacy and reduce potential CAR-associated toxicities.

Enhanced delivery of antibodies across the blood-brain barrier via TEMs with inherent receptor-mediated phagocytosis.

BACKGROUND: The near impermeability of the blood-brain barrier (BBB) and the unique neuroimmune environment of the CNS prevents the effective use of antibodies in neurological diseases. Delivery of biotherapeutics to the brain can be enabled through receptor-mediated transcytosis via proteins such as the transferrin receptor, although limitations such as the ability to use Fc-mediated effector function to clear pathogenic targets can introduce safety liabilities. Hence, novel delivery approaches with alternative clearance mechanisms are warranted. METHODS: Binders that optimized transport across the BBB, known as transcytosis-enabling modules (TEMs), were identified using a combination of antibody discovery techniques and pharmacokinetic analyses. Functional activity of TEMs were subsequently evaluated by imaging for the ability of myeloid cells to phagocytose target proteins and cells. FINDINGS: We demonstrated significantly enhanced brain exposure of therapeutic antibodies using optimal transferrin receptor or CD98 TEMs. We found that these modules also mediated efficient clearance of tau aggregates and HER2+ tumor cells via a non-classical phagocytosis mechanism through direct engagement of myeloid cells. This mode of clearance potentially avoids the known drawbacks of FcγR-mediated antibody mechanisms in the brain such as the neurotoxic release of proinflammatory cytokines and immune cell exhaustion. CONCLUSIONS: Our study reports a new brain delivery platform that harnesses receptor-mediated transcytosis to maximize brain uptake and uses a non-classical phagocytosis mechanism to efficiently clear pathologic proteins and cells. We believe these findings will transform therapeutic approaches to treat CNS diseases. FUNDING: This research was funded by Janssen, Pharmaceutical Companies of Johnson & Johnson.

Innate and Innate-Like Cells: The Future of Chimeric Antigen Receptor (CAR) Cell Therapy.

Conventional αß CAR-T cell-based approaches have revolutionized the field of cancer immunotherapy, but hurdles remain, especially for solid tumors. Novel strategies in conjunction with alternative cell types are therefore required for effective CAR-based therapies. In this respect, innate and innate-like cells with unique immune properties, such as natural killer (NK) cells, NKT cells, γδ T cells, and macrophages, are promising alternatives to αß CAR-T adoptive therapy. We review the applicability of these cells in the context of CAR therapy, focusing on therapies under development, the advantages of these approaches relative to conventional CAR-T cells, and their potential in allogeneic therapies. We also discuss the inherent limitations of these cell types and approaches, and outline numerous strategies to overcome the associated obstacles.

Bispecific Antibodies for Triple Negative Breast Cancer.

Triple negative breast cancer (TNBC), an aggressive breast cancer subtype lacking estrogen receptor (ER), progesterone receptor, and human epidermal growth factor receptor 2 (HER2) expression, is associated with heightened metastatic potential and poor prognosis. While systemic chemotherapy, radiation, and surgical excision remain the current treatment modalities for patients with TNBC, the immunogenic nature of this aggressive disease has presented opportunity for the development of TNBC-targeting immunotherapies. Bispecific antibody-based therapeutics for the treatment of TNBC have gained recent attention in the scientific community. Clinical precedent has been previously established for the FDA-approved bispecific T cell engager, blinatumomab, for acute lymphoblastic leukemia. The present review discusses novel bispecific antibodies for TNBC and emerging TNBC targets for future bispecific antibody development.

Harnessing SLE Autoantibodies for Intracellular Delivery of Biologic Therapeutics.

Intracellular delivery of therapeutic antibodies is highly desirable but remains a challenge for biomedical research and the pharmaceutical industry. Approximately two-thirds of disease-associated targets are found inside the cell. Difficulty blocking these targets with available drugs creates a need for technology to deliver highly specific therapeutic antibodies intracellularly. Historically, antibodies have not been believed to traverse the cell membrane and neutralize intracellular targets. Emerging evidence has revealed that anti-DNA autoantibodies found in systemic lupus erythematosus (SLE) patients can penetrate inside the cell. Harnessing this technology has the potential to accelerate the development of drugs against intracellular targets. Here, we dissect the mechanisms of the intracellular localization of SLE antibodies and discuss how to apply these insights to engineer successful cell-penetrating antibody drugs.

Selective recruitment of γδ T cells by a bispecific antibody for the treatment of acute myeloid leukemia.

Despite significant progress over the last few decades in the treatment of acute myeloid leukemia (AML), there still remains a major unmet medical need for this disease. Immunotherapy approaches for redirecting pan CD3+ T cells to target leukemia blasts have shown limited efficacy in clinical trials and often accompanied with severe toxicity in AML patients. We designed an alternative engager molecule (Anti-TRGV9/anti-CD123), a bispecific antibody that can simultaneously bind to the Vγ9 chain of the Vγ9Vδ2+ γδ T cell receptor and to AML target antigen, CD123, to selectively recruit Vγ9+ γδ T cells rather than pan T cells to target AML blasts. Our results suggest that prototypic bispecific antibodies (a) selectively activate Vγ9+ γδ T cells as judged by CD69 and CD25 surface expression, and intracellular Granzyme B expression, (b) selectively recruit Vγ9+ γδ T cells into cell-cell conjugate formation of γδ T cells with tumor cells indicating selective and effective engagement of effector and target tumor cells, and (c) mediate γδ T cell cytotoxicity (in vitro and in vivo) against tumor antigen-expressing cells. Collectively, these findings suggest that selectively redirecting Vγ9+ γδ T cells to target AML blasts has a potential for immunotherapy for AML patients and favors further exploration of this concept.

An optimally designed anti-human CD40 antibody with potent B cell suppression for the treatment of autoimmune diseases.

Antibodies targeting the CD40-CD40L pathway have great potential for treating autoimmune diseases like rheumatoid arthritis, systemic lupus erythematosus (SLE), lupus nephritis (LN), and inflammatory bowel diseases (IBD). However, in addition to the known difficulty in generating a purely antagonistic CD40 antibody, the presence of CD40 and CD40L on platelets creates additional unique challenges for the safety, target coverage, and clearance of antibodies targeting this pathway. Previously described therapeutic antibodies targeting this pathway have various shortcomings, and the full therapeutic potential of this axis has yet to be realized. Herein, we describe the generation and characterization of BI 655064, a novel, purely antagonistic anti-CD40 antibody that potently neutralizes CD40-CD40L-dependent B-cell stimulation without evidence of impacting platelet functions. This uniquely optimized antibody targeting a highly challenging pathway was obtained by applying stringent functional and biophysical criteria during the lead selection process. BI 655064 has favorable target-mediated drug disposition (TMDD)-saturation pharmacokinetics, consistent with that of a high-quality therapeutic monoclonal antibody.

Emerging CAR-T Cell Therapy for the Treatment of Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC), a highly aggressive breast cancer subtype that lacks estrogen receptor, progesterone receptor, and HER2 expression, does not respond to traditional endocrine and anti-HER2-targeted therapies. Current treatment options for patients with TNBC include a combination of surgery, radiotherapy, and/or systemic chemotherapy. FDA-approved therapies that target DNA damage repair mechanisms in TNBC, such as PARP inhibitors, only provide marginal clinical benefit. The immunogenic nature of TNBC has prompted researchers to harness the body's natural immune system to treat this aggressive breast cancer. Clinical precedent has been recently established with the FDA approval of two TNBC immunotherapies, including an antibody-drug conjugate and an anti-programmed death-ligand 1 monoclonal antibody. Chimeric antigen receptor (CAR)-T cell therapy, a type of adoptive cell therapy that combines the antigen specificity of an antibody with the effector functions of a T cell, has emerged as a promising immunotherapeutic strategy to improve the survival rates of patients with TNBC. Unlike the remarkable clinical success of CAR-T cell therapies in hematologic cancers with Kymriah and Yescarta, the development of CAR-T cell therapies for solid tumors has been much slower and is associated with unique challenges, including a hostile tumor microenvironment. The aim of the present review is to discuss novel approaches and inherent challenges pertaining to CAR-T cell therapy for the treatment of TNBC.

Discovery and characterization of single-domain antibodies for polymeric Ig receptor-mediated mucosal delivery of biologics.

Mucosal immunity is dominated by secretory IgA and IgM, although these are less favorable compared to IgG molecules for therapeutic development. Polymeric IgA and IgM are actively transported across the epithelial barrier via engagement of the polymeric Ig receptor (pIgR), but IgG molecules lack a lumen-targeted active transport mechanism, resulting in poor biodistribution of IgG therapeutics in mucosal tissues. In this work, we describe the discovery and characterization of single-domain antibodies (VHH) that engage pIgR and undergo transepithelial transport across the mucosal epithelium. The anti-pIgR VHH panel displayed a broad range of biophysical characteristics, epitope diversity, IgA competition profiles and transcytosis activity in cell and human primary lung tissue models. Making use of this diverse VHH panel, we studied the relationship between biophysical and functional properties of anti-pIgR binders targeting different domains and epitopes of pIgR. These VHH molecules will serve as excellent tools for studying pIgR-mediated transport of biologics and for delivering multispecific IgG antibodies into mucosal lumen, where they can target and neutralize mucosal antigens.

In Pursuit of Stability Enhancement of a Prostate Cancer Targeting Antibody Derived from a Transgenic Animal Platform.

Accelerated timelines necessitate the discovery of fully human antibodies as biotherapeutics using transgenic animals with a notion that such mAbs bypass humanization. A transgenic animal derived mAb (PCa75) targeted against a prostate cancer antigen had several 'unusual residues' (rare somatic hypermutations, rSHM, with positional frequency of <1%) that resulted in compromised biophysical properties (Tm = 61 °C and intrinsic stability ΔGu = 24.3 kJ/mol) and a sub-optimal immunogenicity profile. In our quest for quality medicine, we pursued antibody engineering strategies to enhance the stability of PCa75. PCa62, an engineered variant of PCa75, retained function while significantly improving the drug-like attributes of the molecule (Tm = 75 °C and intrinsic stability ΔGu = 63.5 kJ/mol). rSHM is rather prevalent, 18 out the 21 approved transgenic animal-derived antibodies have at least one 'unusual residue'. Thus, engineering of rSHM remains critical to enhance the stability and minimize immunogenicity risk of biotherapeutics.

High-Throughput Generation of Bipod (Fab × scFv) Bispecific Antibodies Exploits Differential Chain Expression and Affinity Capture.

Generation of bispecific antibodies (BsAbs) having two unique Fab domains requires heterodimerization of the two heavy chains and pairing of each heavy chain with its cognate light chain. An alternative bispecific scaffold (Bipod) comprising an scFv and a Fab on a heterodimeric Fc eliminates the possibility of light chain mispairing. However, unpredictable levels of chain expression and scFv-induced aggregation can complicate purification and reduce the yield of desired Bipod. Here, we describe a high-throughput method for generation of Bipods based on protein A and CH1 domain affinity capture. This method exploits over-expression of the scFv chain to maximize heterodimer yield. Bipods purified by this method have purity suitable for cell-based functional assays and in vivo studies.

VHH antibody targeting the chemokine receptor CX3CR1 inhibits progression of atherosclerosis.

CX3CR1 has been identified as a highly attractive target for several therapeutic interventions. Despite this potential, no potent antagonists, either small molecule or monoclonal antibody, have been identified. Here we describe the lead finding and engineering approach that lead to the identification of BI 655088, a potent biotherapeutic antagonist to CX3CR1. BI 655088 is a potent CX3CR1 antagonist that, upon therapeutic dosing, significantly inhibits plaque progression in the standard mouse model of atherosclerosis. BI 655088 represents a novel and highly selective biotherapeutic that could reduce inflammation in the atherosclerotic plaque when added to standard of care treatment including statins, which could result in a significant decrease in atherothrombotic events in patients with existing cardiovascular disease.

IgG Charge: Practical and Biological Implications.

Practically, IgG charge can contribute significantly to thermodynamic nonideality, and hence to solubility and viscosity. Biologically, IgG charge isomers exhibit differences in clearance and potency. It has been known since the 1930s that all immunoglobulins carry a weak negative charge in physiological solvents. However, there has been no systematic exploration of this fundamental property. Accurate charge measurements have been made using membrane confined electrophoresis in two solvents (pH 5.0 and pH 7.4) on a panel of twelve mAb IgGs, as well as their F(ab')2 and Fc fragments. The following observations were made at pH 5.0: (1) the measured charge differs from the calculated charge by ~40 for the intact IgGs, and by ~20 for the Fcs; (2) the intact IgG charge depends on both Fv and Fc sequences, but does not equal the sum of the F(ab)'2 and Fc charge; (3) the Fc charge is consistent within a class. In phosphate buffered saline, pH 7.4: (1) the intact IgG charges ranged from 0 to -13; (2) the F(ab')2 fragments are nearly neutral for IgG1s and IgG2s, and about -5 for some of the IgG4s; (3) all Fc fragments are weakly anionic, with IgG1 < IgG2 < IgG4; (4) the charge on the intact IgGs does not equal the sum of the F(ab')2 and Fc charge. In no case is the calculated charge, based solely on H+ binding, remotely close to the measured charge. Some mAbs carried a charge in physiological salt that was outside the range observed for serum-purified human poly IgG. To best match physiological properties, a therapeutic mAb should have a measured charge that falls within the range observed for serum-derived human IgGs. A thermodynamically rigorous, concentration-dependent protein-protein interaction parameter is introduced. Based on readily measured properties, interaction curves may be generated to aid in the selection of proteins and solvent conditions. Example curves are provided.

Non-neutralizing antibodies increase endogenous circulating Ang1 levels.

Ang1 is a soluble ligand to receptor Tie2, and increasing the circulating Ang1 level may improve vascular stabilization under certain disease conditions. Here, we found that the circulating Ang1 level was significantly increased in cynomolgus monkeys treated with non-neutralizing anti-Ang1 antibodies. Improving the antibodies' pharmacokinetic properties by IgG Fc mutations further increased the circulating Ang1 level. However, the mutations decreased the thermal stability of the molecules, which may limit their use as therapeutic antibodies. Nevertheless, we showed that non-neutralizing antibodies may have therapeutic potential by increasing the level of a target molecule in the circulation.

Weak IgG self- and hetero-association characterized by fluorescence analytical ultracentrifugation.

Weak protein-protein interactions may be important to binding cooperativity. A panel of seven fluorescently labeled tracer monoclonal IgG antibodies, differing in variable (V) and constant (C) region sequences, were sedimented in increasing concentrations of unlabeled IgGs of identical, similar, and different backgrounds. Weak IgG::IgG attractive interactions were detected and characterized by global analysis of the hydrodynamic nonideality coefficient, ks . The effects of salt concentration and temperature on ks suggest the interactions are predominantly enthalpic in origin. The interactions were found to be variable in strength, affected by both the variable and constant regions, but indiscriminate with respect to IgG subclass. Furthermore, weak attractive interactions were observed for all the mAbs with freshly purified human poly-IgG. The universality of the weak interactions suggest that they may contribute to effector function cooperativity in the normal immune response, and we postulate that the generality of the interactions allows for a broader range of epitope spacing for complement activation. These studies demonstrate the utility of analytical ultracentrifuge fluorescence detection in measuring weak protein-protein interactions. It also shows the strength of global analysis of sedimentation velocity data by SEDANAL to extract hydrodynamic nonideality ks to characterize weak macromolecular interactions.