Bispecific Antibodies Lymphoma: Current Innovations in Therapy

Bispecific antibodies (BsAbs) are emerging as a promising therapy for lymphoma, offering targeted immune activation with potentially fewer side effects than traditional treatments. By binding to two different antigens, they enhance the immune system’s ability to recognize and attack cancer cells more effectively. Advances in biotechnology have led to improved designs that optimize efficacy and safety.

Research into BsAb therapy is evolving rapidly, bringing new options for patients who may not respond to conventional treatments. Understanding their function and development highlights their potential impact in lymphoma care.

Molecular Structures

Bispecific antibodies (BsAbs) are designed to recognize two distinct antigens while maintaining stability and efficacy. Unlike monoclonal antibodies, which have identical antigen-binding sites, BsAbs incorporate two different binding domains, enabling simultaneous engagement with separate targets. Various structural formats achieve this dual specificity, including fragment-based designs like bispecific T-cell engagers (BiTEs) and full-length immunoglobulin G (IgG)-like configurations that retain the Fc region for improved pharmacokinetics. Each format has advantages in stability, half-life, and manufacturability, influencing therapeutic potential in lymphoma treatment.

One widely studied BsAb format in lymphoma therapy is the IgG-like structure, which resembles natural antibodies but includes modifications for bispecificity. These molecules often use “knobs-into-holes” technology, a protein engineering approach that introduces complementary mutations in the heavy chains to promote heterodimerization while preventing homodimer formation. This design enhances stability in circulation. Fc region modifications can extend half-life by engaging neonatal Fc receptors (FcRn), reducing dosing frequency and improving patient compliance.

Alternative formats, such as BiTEs, lack the Fc region and consist of two single-chain variable fragments (scFvs) connected by a flexible linker. This structure improves tissue penetration and facilitates rapid target engagement but results in a shorter half-life, sometimes requiring continuous infusion. To address this, researchers have explored half-life extension strategies, including albumin-binding domains and PEGylation, which prolong systemic exposure without compromising efficacy.

Immune Cell Engagement

The effectiveness of bispecific antibodies (BsAbs) in lymphoma relies on their ability to direct immune cells toward malignant targets. By binding to a tumor-associated antigen and an immune effector cell receptor, BsAbs facilitate interactions that enhance cytotoxic activity. A well-studied mechanism involves T-cell engagement through the CD3 receptor, which activates cytotoxic T lymphocytes. This interaction bypasses the need for conventional antigen presentation, allowing T cells to target lymphoma cells independent of major histocompatibility complex (MHC) restrictions, a common immune evasion strategy in hematologic malignancies.

The efficiency of immune synapse formation depends on factors such as binding affinity, epitope selection, and spatial orientation. High-affinity interactions with CD3 enhance T-cell activation but can increase cytokine release, raising the risk of immune-related adverse events. To mitigate this, researchers have developed BsAbs with optimized CD3 binding affinities that maintain anti-lymphoma activity while reducing systemic toxicity. Clinical trials show that modifications in the Fc region or linker design can fine-tune immune engagement, balancing efficacy with safety. For example, a study in The Lancet Oncology evaluating glofitamab, a CD20xCD3 BsAb, demonstrated promising response rates in relapsed or refractory diffuse large B-cell lymphoma (DLBCL) while using a step-up dosing regimen to manage cytokine release syndrome (CRS).

Beyond T cells, BsAbs can engage natural killer (NK) cells and macrophages through receptors like CD16 or CD47. NK cell-engaging BsAbs leverage antibody-dependent cellular cytotoxicity (ADCC) to enhance tumor clearance, offering an alternative for patients with T-cell exhaustion. Preclinical models show that BsAbs targeting CD30 on lymphoma cells and CD16 on NK cells drive strong anti-tumor responses without excessive cytokine release, highlighting their potential as a safer immunotherapy. Similarly, macrophage-engaging BsAbs that block the CD47-SIRPα axis have been investigated for their ability to enhance phagocytosis of lymphoma cells while minimizing immune suppression.

Tumor Antigen Selection

Selecting effective tumor-associated antigens (TAAs) for bispecific antibody (BsAb) therapy in lymphoma requires balancing specificity and broad applicability. The ideal antigen should be highly expressed on malignant B or T cells while minimally present on normal tissues to reduce off-target effects. CD19, CD20, and CD22 are primary targets in B-cell lymphomas due to their consistent expression across subtypes, including diffuse large B-cell lymphoma (DLBCL), follicular lymphoma, and mantle cell lymphoma. CD19 is nearly universally expressed in B-cell malignancies, CD20 has a well-established therapeutic history, and CD22 provides an alternative for patients resistant to CD19-targeted therapies.

Antigen density and internalization rates influence BsAb binding efficiency and therapeutic durability. High antigen density, as seen with CD19, enhances BsAb engagement and tumor suppression. In contrast, rapid internalization, a feature of CD22, can reduce treatment efficacy by limiting surface antigen availability. To address this, researchers have explored dual-targeting strategies, such as CD19xCD22 BsAbs, to prevent antigen-negative relapse, a common resistance mechanism in lymphoma treatment. Preclinical models suggest that targeting two TAAs simultaneously reduces the likelihood of immune escape.

Beyond traditional B-cell markers, emerging targets such as ROR1 and CD79b are being investigated. ROR1 is expressed in mantle cell lymphoma and certain aggressive lymphomas but is largely absent in normal adult tissues, making it a promising candidate for reducing toxicity. CD79b, a component of the B-cell receptor signaling complex, has been successfully targeted by antibody-drug conjugates like polatuzumab vedotin, suggesting its potential for BsAb therapy. These novel antigens may provide additional options for patients who relapse after CD19- or CD20-directed therapies, addressing a critical unmet need in refractory lymphoma cases.

Laboratory Production

Manufacturing bispecific antibodies (BsAbs) for lymphoma treatment requires advanced biotechnological processes to ensure precision in molecular assembly, stability, and scalability. Unlike monoclonal antibodies, which are produced using single hybridoma or recombinant cell lines, BsAbs require complex engineering to generate two distinct antigen-binding domains within a single molecule. Genetic modifications in Chinese hamster ovary (CHO) cells, the most commonly used expression system, enable controlled production of heterodimeric heavy chains while minimizing mispairing. The “knobs-into-holes” approach facilitates correct heavy chain assembly by introducing complementary mutations that promote heterodimer formation, reducing the likelihood of unwanted homodimers that could affect therapeutic efficacy.

Purification presents challenges due to the structural heterogeneity of BsAbs. Standard protein A chromatography, widely used for monoclonal antibody purification, often requires additional steps such as ion-exchange or size-exclusion chromatography to isolate correctly assembled molecules. Ensuring batch-to-batch consistency is critical, as variations in glycosylation patterns or aggregation levels can impact pharmacokinetics and immunogenicity. Regulatory agencies, including the FDA and EMA, require extensive characterization studies using mass spectrometry and bioassays to confirm structural integrity and functional activity before clinical approval.