Grabbing the Bull by Both Horns: Bovine Ultralong CDR-H3 Paratopes Enable Engineering of ‘Almost Natural’ Common Light Chain Bispecific Antibodies Suitable For Effector Cell Redirection

A subset of antibodies found in cattle comprises ultralong CDR-H3 regions of up to 70 amino acids. Interestingly, this type of immunoglobulin usually pairs with the single germline VL gene, V30 that is typically very conserved in sequence. In this work, we have engineered ultralong CDR-H3 common light chain bispecific antibodies targeting Epidermal Growth Factor Receptor (EGFR) on tumor cells as well as Natural Cytotoxicity Receptor NKp30 on Natural Killer (NK) cells. Antigen-specific common light chain antibodies were isolated by yeast surface display by means of pairing CDR-H3 diversities following immunization with a single V30 light chain. After selection, EGFR-targeting paratopes as well as NKp30-specific binders were combined into common light chain bispecific antibodies by exploiting the strand-exchange engineered domain (SEED) technology for heavy chain heterodimerization. Biochemical characterization of resulting bispecifics revealed highly specific binding to the respective antigens as well as simultaneous binding to both targets. Most importantly, engineered cattle-derived bispecific common light chain molecules elicited potent NK cell redirection and consequently tumor cell lysis of EGFR-overexpressing cells as well as robust release of proinflammatory cytokine interferon-γ. Taken together, this data is giving clear evidence that bovine bispecific ultralong CDR-H3 common light chain antibodies are versatile for biotechnological applications.

A synthetic bispecific antibody capable of neutralizing SARS-CoV-2 Delta and Omicron

Bispecific antibodies have emerged as a promising strategy for curtailing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immune escape. This brief report highlights RBT-0813 (also known as TB493-04), a synthetic, humanized, receptor-binding domain (RBD)-targeted bispecific antibody that retains picomolar affinity to the Spike (S) trimers of all major variants of concern and neutralizes both SARS-CoV-2 Delta and Omicron in vitro.

Pharmacokinetic Developability and Disposition Profiles of Bispecific Antibodies: A Case Study with Two Molecules

Bispecific antibodies (BsAb) that engage multiple pathways are a promising therapeutic strategy to improve and prolong the efficacy of biologics in complex diseases. In the early stages of discovery, BsAbs often exhibit a broad range of pharmacokinetic (PK) behavior. Optimization of the neonatal Fc receptor (FcRn) interactions and removal of undesirable physiochemical properties have been used to improve the ‘pharmacokinetic developability’ for various monoclonal antibody (mAb) therapeutics, yet there is a sparsity of such information for BsAbs. The present work evaluated the influence of FcRn interactions and inherent physiochemical properties on the PK of two related single chain variable fragment (scFv)-based BsAbs. Despite their close relation, the two BsAbs exhibit disparate PK in cynomolgus monkeys with BsAb-1 having an aberrant clearance of ~2 mL/h/kg and BsAb-2 displaying a an ~10-fold slower clearance (~0.2 mL/h/kg). Evaluation of the physiochemical characteristics of the molecules, including charge, non-specific binding, thermal stability, and hydrophobic properties, as well as FcRn interactions showed some differences. In-depth drug disposition results revealed that a substantial disparity in the complete release from FcRn at a neutral pH is a primary factor contributing to the rapid clearance of the BsAb-1 while other biophysical characteristics were largely comparable between molecules.

Emerging immunological strategies: recent advances and future directions

Immunotherapy plays a compelling role in cancer treatment and has already made remarkable progress. However, many patients receiving immune checkpoint inhibitors fail to achieve clinical benefits, and the response rates vary among tumor types. New approaches that promote anti-tumor immunity have recently been developed, such as small molecules, bispecific antibodies, chimeric antigen receptor T cell products, and cancer vaccines. Small molecule drugs include agonists and inhibitors that can reach the intracellular or extracellular targets of immune cells participating in innate or adaptive immune pathways. Bispecific antibodies, which bind two different antigens or one antigen with two different epitopes, are of great interest. Chimeric antigen receptor T cell products and cancer vaccines have also been investigated. This review explores the recent progress and challenges of different forms of immunotherapy agents and provides an insight into future immunotherapeutic strategies.

Recent advances and challenges of bispecific antibodies in solid tumors

Cancer immunotherapy has made remarkable progress in the past decade. Bispecific antibodies (BsAbs) have acquired much attention as the next generation strategy of antibody-target cancer immunotherapy, which overwhelmingly focus on T cell recruitment and dual receptors blockade. So far, BsAb drugs have been proved clinically effective and approved for the treatment of hematologic malignancies, but no BsAb have been approved in solid tumors. Numerous designed BsAb drugs for solid tumors are now undergoing evaluation in clinical trials. In this review, we will introduce the formats of bispecific antibodies, and then update the latest preclinical studies and clinical trials in solid tumors of BsAbs targeting EpCAM, CEA, PMSA, ErbB family, and so on. Finally, we discuss the BsAb-related adverse effects and the alternative strategy for future study.

T Cell Bispecific Antibodies: An Antibody-Based Delivery System for Inducing Antitumor Immunity

As a breakthrough immunotherapy, T cell bispecific antibodies (T-BsAbs) are a promising antibody therapy for various kinds of cancer. In general, T-BsAbs have dual-binding specificity to a tumor-associated antigen and a CD3 subunit forming a complex with the TCR. This enables T-BsAbs to crosslink tumor cells and T cells, inducing T cell activation and subsequent tumor cell death. Unlike immune checkpoint inhibitors, which release the brake of the immune system, T-BsAbs serve as an accelerator of T cells by stimulating their immune response via CD3 engagement. Therefore, they can actively redirect host immunity toward tumors, including T cell recruitment from the periphery to the tumor site and immunological synapse formation between tumor cells and T cells. Although the low immunogenicity of solid tumors increases the challenge of cancer immunotherapy, T-BsAbs capable of immune redirection can greatly benefit patients with such tumors. To investigate the detailed relationship between T-BsAbs delivery and their T cell redirection activity, it is necessary to determine how T-BsAbs deliver antitumor immunity to the tumor site and bring about tumor cell death. This review article discusses T-BsAb properties, specifically their pharmacokinetics, redirection of anticancer immunity, and local mechanism of action within tumor tissues, and discuss further challenges to expediting T-BsAb development.

Multidisciplinary Provider Insights to Promote Adoption of Bispecific Antibodies to Treat Cancer in the Community

Bispecific antibodies (BsAbs) are an emerging class of novel immunotherapy agents that have led to major breakthroughs in the treatment of hematologic malignancies. By targeting two separate antigens at the same time, BsAbs can bridge tumor cells to cytotoxic immune cells and bypass several limitations of conventional monoclonal antibody treatment (Wang et al., 2019). In 2020, the Association of Community Cancer Centers (ACCC) launched an ongoing education program to identify and address barriers to awareness, preparedness, adoption, and use of BsAbs to treat cancer. As part of this program, ACCC developed a survey with an expert Advisory Committee to gain an understanding of multidisciplinary cancer providers' experiences with BsAbs. The survey primarily assessed experiences with blinatumomab, the first FDA-approved bispecific antibody for the treatment of malignancy (Newman & Benani, 2016). One hundred and twenty-nine individuals responded to the survey. Sixty percent of these respondents reported prescribing, dispensing, and administering blinatumomab and/or caring for patients being treated with blinatumomab. Of those respondents, 44% were medical oncologists/hematologists, 8% were advanced practice providers (APPs), 17% were nurses, 23% were pharmacists, and 9% fell into an 'Other' category of various other disciplines. Interestingly, the provider experience with blinatumomab varied greatly. Ninety-two percent of oncologists indicated having experience with blinatumomab while only 35% of nurses reported so. Regarding how blinatumomab is used in the community, respondents indicated that 59% of their institutions use it to treat relapsed or refractory acute lymphoblastic leukemia (ALL) while 41% use it to treat ALL with MRD positivity. Additionally, 74% of oncologists use blinatumomab before CAR-T therapy when considering both therapies for patients with ALL. Survey results also showed that although 79% of providers felt comfortable caring for patients being treated with blinatumomab, 59% identified barriers when caring for these patients. Some of the common challenges include transitioning patients from the inpatient to outpatient setting (41%), managing patients in remote areas (33%), securing insurance coverage (28%), managing side effects (27%), assisting patients with costs (24%), and lacking in-house expertise with the drug (22%). Another reported obstacle was the management neurotoxicity and cytokine release syndrome (CRS). In the survey, less than half of oncologists reported experience with managing neurotoxicity or CRS and only 6-9% of APPs reported the same. In general, more oncologists described feeling comfortable with using blinatumomab compared to APPs or nurses. Notably, 23% of nurses did not feel they had all the information needed to safely administer blinatumomab. In terms of opportunities to promote smooth adoption of blinatumomab, 86% of respondents indicated that written guidelines, best practices, and care recommendations would be helpful when caring for patients. Specific desired resources include a list of home health pharmacies and agencies familiar with the drug, care coordinators or navigators, best practices on transitioning from inpatient to outpatient administration, information on how to address problems that may occur with outpatient administration, and in-house or onsite expertise from either the drug manufacturer or someone within the organization. Respondents noted direct patient education as another significant area of need. Eighty-two percent felt that educational resources for patients and caregivers on transitioning from inpatient to outpatient care would be beneficial, and 70% thought that peer support services for patients would also be helpful. Multiple BsAbs are in various stages of development for hematologic malignancies. Using blinatumomab as an example, this survey highlighted challenges to the use of BsAbs and identified opportunities to overcome these obstacles. Translation of best practices for use in the community must be established to reach all eligible patients with cancer who may benefit from these therapies. With this survey data, ACCC is positioned to offer this support. Through its education program, ACCC will build on the survey results to develop content and resources that prepare multidisciplinary providers to welcome BsAbs into the community to treat cancer. Disclosures Atembina: Amgen: Research Funding. Boehmer: Pfizer, Inc: Other: paid consultant within the past 12 months; Amgen: Research Funding. Terrell: Amgen: Honoraria. Koka: Amgen: Honoraria. Janakiram: Amgen: Honoraria. Grothey: Amgen: Honoraria. Morris: Amgen: Honoraria. Rogers: Coherus BioSciences: Speakers Bureau; Astra Zeneca: Speakers Bureau. Kelly: Amgen: Honoraria. Berdeja: Poseida: Research Funding; Acetylon: Research Funding; Lilly: Research Funding; Kite Pharma: Consultancy; Genentech: Research Funding; CRISPR Therapeutics: Consultancy, Research Funding; Celularity: Research Funding; Celgene: Consultancy, Research Funding; Teva: Research Funding; EMD Serono: Research Funding; GlaxoSmithKline: Research Funding; SecuraBio: Consultancy; Legend Biotech: Consultancy; Janssen: Consultancy, Research Funding; Novartis: Research Funding; Incyte: Research Funding; Ichnos Sciences: Research Funding; Abbvie: Research Funding; Amgen: Research Funding; Astex Pharmaceuticals: Research Funding; Bluebird bio: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Takeda: Consultancy; Sanofi: Research Funding. El Chaer: Amgen: Honoraria, Research Funding.

Clinical Outcomes of Relapsed/Refractory Multiple Myeloma Patients Following Treatment with Bispecific Antibodies (BiAbs)

Background: Bispecific antibodies (BiAbs) are a novel off-the-shelf class of drugs currently being investigated in clinical trials for patients with relapsed/refractory multiple myeloma (RRMM) with promising efficacy in heavily pretreated patients. BiAbs simultaneously bind two antigens, thereby engaging CD3+ T cells with myeloma cells expressing specific antigens such as BCMA, GPRC5D, FcRH5 or CD38. However, the outcome of myeloma patients after relapse on BiAbs is unknown and effective approaches for salvage therapy are needed. Methods: Demographics, disease characteristics and post-clinical trial outcomes were collected retrospectively on RRMM patients who relapsed after BiAb therapy at the Tisch Cancer Institute (The Mount Sinai Hospital, New York). We identified a total of 116 patients who were enrolled on trials with BiAbs targeting either BCMA or GPRC5D. Of these, 69 patients were no longer enrolled on the trials due to disease progression (including 5 patients who died on the trial). Clinical data was collected up until July of 2021. This retrospective study was approved by the institutional review board (IRB) and follows the Declaration of Helsinki and International Conference on Harmonization Guidelines for Good Clinical Practice (IRB: GCO#: 11-1433). Survival and response duration were calculated by Kaplan-Meier estimation. Results: The 64 RRMM patients had a median age of 58.5 years (range: 46-82) at time of disease progression following BiAbs therapy, and 48% were male. Median time from diagnosis to initiation of BiAbs therapy was 5 years (range: 1.6-16.3) and patients had a median follow-up of 24.9 months from time of relapse from BiAb therapy. Fifty patients (78%) had high-risk cytogenetics, including gain1q21, del17p, t(4;14), t(14;16) and t(14;20). Most patients were highly pretreated with a median of 7 prior lines (range: 3-17) and 54 patients (84%) had received an autologous stem cell transplant (ASCT) prior to receiving BiAbs. Three patients were treated with chimeric antigen receptor (CAR) T cell therapy prior to BiAb and 5 patients were exposed to a BCMA antibody-drug conjugate prior to the BiAb. Furthermore, 89% of patients were triple-class refractory while 44% were penta-refractory. Following treatment with a BiAb, 2 patients were lost to follow up, 1 patient decided to be monitored off treatment and 61 patients received a median of 2 lines of therapy (range: 1-8). Most common therapies included a second BiAb (n=20; 33%), CAR T cells (n=15; 26%) or intensive chemotherapy (n=36; 59%) such as melphalan, carmustine or VDPACE with stem cell rescue (n=13) or DCEP (n=23). Best response to initial treatment following the BiAb varied widely and included 12 complete responses, 5 very good partial responses, 17 partial responses, 2 minimal responses, 10 stable disease and 13 progressed disease for an overall response rate (ORR) of 58%. Encouraging responses were seen in 10 patients who directly transitioned from one BiAb to another and 8 patients who directly transitioned to CAR T cell therapy. The progression-free survival of those 18 patients who directly transitioned to a T cell directed therapy was 28.9 months (95% CI: 21.6-NE) and their median overall survival was not reached. Furthermore, the overall survival for the whole cohort of patients was 17.6 months (95% CI: 12.0-NE). Conclusion: Our data suggests that heavily pretreated, predominantly triple-class refractory, patients relapsing after BiAbs may still have good outcomes when sequentially treating with other immunological/T cell-directed therapeutics such as BiAbs and CAR T cells. Studying the appropriate sequence of these treatments is of paramount importance as BiAbs are expected to become part of the standard of care for RRMM patients. Disclosures Richard: Karyopharm, Janssen: Honoraria. Richter: Celgene: Speakers Bureau; Adaptive Biotechnologies: Speakers Bureau; Celgene: Consultancy; Janssen: Consultancy; BMS: Consultancy; Karyopharm: Consultancy; Antengene: Consultancy; Sanofi: Consultancy; X4 Pharmaceuticals: Consultancy; Oncopeptides: Consultancy; Adaptive Biotechnologies: Consultancy; Janssen: Speakers Bureau; Secura Bio: Consultancy; Astra Zeneca: Consultancy. Chari: Janssen Pharmaceuticals: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Novartis Pharmaceuticals: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Pharmacyclics: Research Funding; Seattle Genetics: Consultancy, Research Funding; Takeda Pharmaceutical Company: Consultancy, Research Funding; Karyopharm: Consultancy; Sanofi Genzyme: Consultancy; Oncopeptides: Consultancy; Antegene: Consultancy; Glaxosmithkline: Consultancy; Secura Bio: Consultancy. Parekh: Foundation Medicine Inc: Consultancy; Amgen: Research Funding; PFIZER: Research Funding; CELGENE: Research Funding; Karyopharm Inv: Research Funding.