Monoclonal antibodies (MAbs) remain the dominant biopharmaceutical product class, but as biotechnologies have advanced in recent decades, developers have found ways to exploit their “magic-bullet” capabilities while putting aside their limitations. That has led to a new generation of antibody-related therapeutics created by cutting and pasting molecular domains. Researchers are mixing and matching functional moieties of antibodies and other molecules to create custom-designed proteins with powerful efficacy and tunable targeting. Many avenues have been pursued to improve on the monoclonal antibody paradigm, leading to development of new monoclonals and antibody-derived therapeutic proteins. Derivatives include modified intact antibodies with modulated effector functions, bispecific and multispecific antibodies, and antibody fragments. In this featured report, BPI contributes to the expanding literature of antibody fragments and fusions with a review of recent literature followed by a discussion of bispecifics in development and two technical reports related to fragments and fusion proteins. Additions from BioProcess Insider add perspectives from Zymeworks and Lonza.

Antibody-Derivative Biotherapeutics: Fragments and Fusions Define the Future
by Cheryl Scott
As biotechnologies have advanced in recent decades, developers have found numerous ways to exploit the “magic-bullet” capabilities of MAbs while putting aside some of their limitations. This brings to light a new generation of antibody-related therapeutics created by cutting and pasting molecular domains. Researchers are mixing and matching functional moieties of antibodies and other molecules to create custom-designed proteins with powerful efficacy and tunable targeting. A simple search at Taylor & Francis Online (the academic journal portal of BPI’s parent company) turns up hundreds of citations involving antibody fragments, conjugates, and bi-/multispecific molecules from the past year alone. Many articles are open-access and otherwise freely available for further research. Here, BPI’s senior technical editor reviews some of the latest developments in antibody engineering, product characterization and developability assessment, immunotherapy strategy, and solutions for cancer and the pandemic.

Development and Manufacture of Therapeutic Bispecific Antibodies
by Janice Reichert and Nick Hutchinson
Generating antibodies with two or more specificities has great potential for creating new treatments for patients with unmet medical needs. Bispecific antibody development is stimulating innovation in bioprocessing techniques from expression through upstream processing and downstream purification. Wherever possible, process-development engineers are borrowing techniques that were honed for MAb platforms, then applying those to bispecifics manufacturing. But the unique qualities of bispecifics make biomanufacturing strategies for them a still-emerging art form. Much remains to be done toward creating high-producing and high-yielding processes for this class of products, and challenges are likely to increase as product candidates become ever more sophisticated. Here, Janice Reichert and Nick Hutchinson of The Antibody Society review the state of bispecific antibody development and describe the manufacturing-related obstacles that drug companies are facing as their candidates progress through clinical trials.

Expression of Recombinant Antibody Fragments: High-Density Fermentation in Multiuse and Single-Use Systems
by Yongxue Ding, You Pan, Mark Gibson, Troy McSherry, and Steven P. Allen
Recombinant antigen-binding fragments (rFabs) are used increasingly in therapeutic programs, diagnostics, and fundamental academic research applications. But relatively low production yields are a major concern with expression of correctly folded, functional rFabs in Escherichia coli bacteria. Authors from Abbott Diagnostics report on their work to improve a low-expressing rFab process through high-density fermentation. After development work using a steam-in-place multiuse fermentor, they worked further to adapt the intensified process to run in a single-use fermentor instead. In both cases, rFab yield is influenced by not only the level of aeration, but also the method for control of optimal dissolved oxygen (DO) (10). Here, the authors report their findings and compare the performance of both systems.

Lymphocyte Activation Gene 3 in Immunooncology: A Soluble Protein Alternative
by Frédéric Triebel
The biopharmaceutical industry needs alternative immunotherapeutic approaches to boost T cells and reinitiate cancer immunosurveillance against poorly immunogenic tumors. With promising clinical results emerging from immunooncology studies, Immutep’s eftilagimod alpha (efti) product is a first-in-class soluble lymphocyte-activation protein that can work alone or be combined with other approaches. Here, the company’s chief scientific/medical officer describes how it can serve as a MAb fusion partner, a companion for chemotherapies and checkpoint inhibitors, and an adjuvant for cancer vaccines. In chemoimmunotherapy, efti induces maturation of antigen-presenting cells, facilitating transport of tumor antigenic debris to lymph nodes for presentation to T cells. With MAbs, it helps to activate cellular immune-response mechanisms to optimize tumor-cell recognition and killing. That could provide synergistic effects and increase the frequency of durable disease response. And as adjuvant to cancer vaccines or intratumoral injections, efti boosts the local immune response to specific tumor antigens.