Tuning Relative Polypeptide Expression to Optimize Assembly, Yield and Downstream Processing of Bispecific Antibodies

Identification of Mispairing Omic Signatures in Chinese Hamster Ovary (CHO) Cells Producing a Tri-Specific Antibody

Monoclonal antibody-based therapy has shown efficacy against cancer, autoimmune, infectious, and inflammatory diseases. Multispecific antibodies (MsAbs), including trispecifics (tsAbs), offer enhanced therapeutic potential by targeting different epitopes. However, when co-expressed from three or more different polypeptide chains, MsAb production can lead to incorrect chain assembly and co-production of mispaired species with impaired biological activity. Moreover, mispairing carries significant challenges for downstream purification, decreasing yields and increasing the cost of bioprocess development. In this study, quantitative transcriptomics and proteomics analyses were employed to investigate which signaling pathways correlated with low and high mispairing clone signatures. Gene and protein expression profiles of Chinese hamster ovary (CHO) clones producing an tsAb were analyzed in the exponential growth and stationary (tsAb production) phase of fed-batch culture. Functional analysis revealed activated endoplasmic reticulum stress in high mispairing clones in both culture phases, while low mispairing clones exhibited expression profiles indicative of activated protein translation, as well as higher endocytosis and target protein degradation, suggesting the clearance of unfolded proteins through ubiquitin-mediated mechanisms. In addition, through transcriptomic profiling, we identified a group of genes that have the potential to be used as a biomarker panel tool for identifying high mispairing levels in the early stages of bioprocess development.

Vector design for enhancing expression level and assembly of knob-into-hole based FabscFv-Fc bispecific antibodies in CHO cells

BACKGROUND

Two-armed FabscFv-Fc is a favoured bispecific antibody (BsAb) format due to its advantages of the conventional IgG structure. Production of FabscFv-Fc requires expression of three polypeptide chains, one light chain (LC), one heavy chain (HC) and a scFv fused to the Fc (scFvFc) at optimal ratios.

METHODS

We designed a set of internal ribosome entry site (IRES)-mediated multi-cistronic vectors tailoring to various expression ratios of the three polypeptides to study how the chain ratios affect the FabscFv-Fc production.

RESULTS

Expression of HC and scFvFc chains at 1:1 ratio and excess LC gave the highest yield of correctly assembled product. Compared to the use of IRES and multiple promoters, using 2A peptides for co-expression of the three polypeptides gave the highest titre and correctly assembled product.

CONCLUSION

The results obtained in this work provide insights to the impacts of hetero-chain ratios on the BsAb production.

The manufacturing considerations of bispecific antibodies

INTRODUCTION

Antibody therapies have made huge strides in providing safe and efficacious drugs for autoimmune, cancer and infectious disease. These bispecific antibodies can be assembled from the basic building blocks of IgGs, resulting in dozens of formats.

AREAS COVERED

It is important to consider the manufacturability of these formats early in the antibody discovery phases. Broadly categorizing bispecific antibodies into IgG-like, fragment-based, appended and hybrid formats can help in looking at early manufacturability considerations.

EXPERT OPINION

Ideally, bispecific antibody manufacturing should contain a minimal number of steps, with processes that give high yields of protein with no contaminants. Many of these have been determined for the fragment-based bispecific blinatumomab and the IgG-like bispecifics from hybridomas. However, for new formats, these need to be considered early in the research and development pipeline. The hybrid formats offer an unusual alternative in generating high pure yields of bispecific molecules if the engineering challenges can be deciphered.

Expression liabilities in a four-chain bispecific molecule

Multispecific antibodies, often composed of three to five polypeptide chains, have become increasingly relevant in the development of biotherapeutics. These molecules have mechanisms of action that include redirecting T cells to tumors and blocking multiple pathogenic mediators simultaneously. One of the major challenges for asymmetric multispecific antibodies is generating a high proportion of the correctly paired antibody during production. To understand the causes and effects of chain mispairing impurities in a difficult to express multispecific hetero-IgG, we investigated consequences of individual and pairwise chain expression in mammalian transient expression hosts. We found that one of the two light chains (LC) was not secretion competent when transfected individually or cotransfected with the noncognate heavy chain (HC). Overexpression of this secretion impaired LC reduced cell growth while inducing endoplasmic reticulum stress and CCAAT/enhancer-binding protein homologous protein (CHOP) expression. The majority of this LC was observed as monomer with incomplete intrachain disulfide bonds when expressed individually. Russell bodies (RB) were induced when this LC was co-expressed with the cognate HC. Moreover, one HC paired promiscuously with noncognate LC. These results identify the causes for the low product quality observed from stable cell lines expressing this heteroIgG and suggest mitigation strategies to improve overall process productivity of the correctly paired multispecific antibody. The approach described here provides a general strategy for identifying the molecular and cellular liabilities associated with difficult to express multispecific antibodies.

The Confluence of Innovation in Therapeutics and Regulation: Recent CMC Considerations

The field of human therapeutics has expanded tremendously from small molecules to complex biological modalities, and this trend has accelerated in the last two decades with a greater diversity in the types and applications of novel modalities, accompanied by increasing sophistication in drug delivery technology. These innovations have led to a corresponding increase in the number of therapies seeking regulatory approval, and as the industry continues to evolve regulations will need to adapt to the ever-changing landscape. The growth in this field thus represents a challenge for regulatory authorities as well as for sponsors. This review provides a brief description of novel biologics, including innovative antibody therapeutics, genetic modification technologies, new developments in vaccines, and multifunctional modalities. It also describes a few pertinent drug delivery mechanisms such as nanoparticles, liposomes, coformulation, recombinant human hyaluronidase for subcutaneous delivery, pulmonary delivery, and 3D printing. In addition, it provides an overview of the current CMC regulatory challenges and discusses potential methods of accelerating regulatory mechanisms for more efficient approvals. Finally, we look at the future of biotherapeutics and emphasize the need to bring these modalities to the forefront of patient care from a global perspective as effectively as possible.