Pharmacokinetics and Tolerability of a Dual Variable Domain Immunoglobulin ABT-981 Against IL-1α and IL-1β in Healthy Subjects and Patients With Osteoarthritis of the Knee

Efficacy of Anti-Interleukin-1 Therapeutics in the Treatment of Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials from the Years 2000 to 2023

Objectives: This study aimed to evaluate the efficacy of anti-interleukin-1 therapeutics for treating knee osteoarthritis (KOA). Our research included interleukin-1 (IL-1) inhibitors, IL-1 antibodies and IL-1 receptor antagonists (IL-1 Ras). Methods: We systematically searched PubMed and Mendeley to find randomized control trials (RCTs) or clinical trials (CTs) of anti-interleukin-1 therapeutics in KOA from 2000 to 2023. The outcomes were changes in pain, function and stiffness scores. The research was conducted between November 2023 and January 2024. The risk of bias was assessed using Cochrane Risk of Bias tool RoB 2. Results: Analysis of the nine included studies showed a statistically significant difference in terms of the pain relief group (SMD = -0.20, 95% CI: -0.39 to -0.01, p = 0.0348), physical function improvement (SMD = -0.20, 95% CI: -0.39 to 0.00, p = 0.0479) and stiffness reduction (SMD = -0.22, 95% CI: -0.43 to 0.00, p = 0.0475) between anti-IL-1 therapeutics and placebo or nonsteroidal anti-inflammatory drugs (NSAIDs). However, when we separately analysed placebo and NSAIDs subgroups, the statistical significance was observed only in the placebo group. Our article was limited by the quality of the included RCTs. Two of the included trials were of poor methodological quality, and five showed selective reporting. Conclusions: The results of our study suggest that anti-IL-1 therapeutics might have better efficacy in KOA treatment than placebo or NSAIDs; yet, taking into account the limited availability of studies and data concerning anti-IL-1 in osteoarthritis treatment, we think that more high-quality RCTs on this subject are needed.

Efficacy and safety of anti-interleukin-1 therapeutics in the treatment of knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

We aimed to evaluate the efficacy and safety of anti-interleukin-1 therapeutics, including IL-1 antibodies, interleukin-1 receptor antagonists (IL-1 Ras) and IL-1 inhibitors, for knee osteoarthritis (KOA) treatment.

METHODS

Databases (Medline, Embase, Web of Science and CENTRAL) and ClinicalTrials.gov were systematically searched for randomized controlled trials (RCTs) of anti-interleukin-1 therapeutics from inception to August 31, 2022. The outcomes were the mean change in pain and function scores and the risk of adverse effects (AEs).

RESULTS

In the 12 studies included, anti-interleukin-1 therapeutics were superior to placebo in terms of pain relief (standardized mean difference [SMD] =  - 0.38, 95% confidence interval [CI] =  - 1.82 to - 0.40, p < 0.001, I2 = 77%) and functional improvement (SMD =  - 1.11, 95% CI =  - 1.82 to - 0.40, p = 0.002, I2 = 96%). The incidence of any AE (risk ratio [RR] = 1.02, 95% CI = 0.88-1.18, p < 0.001, I2 = 76%) was higher following treatment with anti-interleukin-1 therapeutics than placebo, while no significant difference was found in the incidence of serious AEs (SAEs) or discontinuations due to AEs. Subgroup analyses showed that IL-1 antibodies and the IL-1 inhibitor provided pain relief (IL-1 antibodies: SMD =  - 0.61, 95% CI =  - 0.92 to - 0.31, p < 0.001; IL-1 inhibitor: SMD =  - 0.39, 95% CI =  - 0.72 to - 0.06, p = 0.02, I2 = 74.0%) and functional improvement (IL-1 antibodies: SMD =  - 1.75, 95% CI =  - 2.10 to - 1.40, p < 0.001; IL-1 inhibitor: SMD =  - 0.28, 95% CI =  - 0.83 to 0.27, p = 0.31, I2 = 88%) superior to those of placebo, whereas IL-1 Ras did not. However, the IL-1 inhibitor increased the incidence of any AE (RR = 1.35, 95% CI = 0.92-1.98, p < 0.001, I2 = 85%) but not the risk of SAEs or discontinuations due to AEs. IL-1 antibodies and IL-1 Ras showed no difference in safety compared with placebo.

CONCLUSIONS

Anti-interleukin-1 therapeutics could relieve OA-related pain and improve function, but is probably associated with an increased risk of adverse events. Specially, IL-1 antibodies and an IL-1 inhibitor could relieve OA-related pain and improve function, whereas IL-1 Ras could not. IL-1 antibodies and IL-1 Ras were relatively safe options, but IL-1 inhibitors were associated with safety concerns.

Osteoarthritis Pain

Joint pain is the hallmark symptom of osteoarthritis (OA) and the main reason for patients to seek medical assistance. OA pain greatly contributes to functional limitations of joints and reduced quality of life. Although several pain-relieving medications are available for OA treatment, the current intervention strategy for OA pain cannot provide satisfactory pain relief, and the chronic use of the drugs for pain management is often associated with significant side effects and toxicities. These observations suggest that the mechanisms of OA-related pain remain undefined. The current review mainly focuses on the characteristics and mechanisms of OA pain. We evaluate pathways associated with OA pain, such as nerve growth factor (NGF)/tropomyosin receptor kinase A (TrkA), calcitonin gene-related peptide (CGRP), C–C motif chemokine ligands 2 (CCL2)/chemokine receptor 2 (CCR2) and tumor necrosis factor alpha (TNF-α), interleukin-1beta (IL-1β), the NOD-like receptor (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome, and the Wnt/β-catenin signaling pathway. In addition, animal models currently used for OA pain studies and emerging preclinical studies are discussed. Understanding the multifactorial components contributing to OA pain could provide novel insights into the development of more specific and effective drugs for OA pain management.

Collagen type II: From biosynthesis to advanced biomaterials for cartilage engineering

Collagen type II is the major constituent of cartilage tissue. Yet, cartilage engineering approaches are primarily based on collagen type I devices that are associated with suboptimal functional therapeutic outcomes. Herein, we briefly describe cartilage's development and cellular and extracellular composition and organisation. We also provide an overview of collagen type II biosynthesis and purification protocols from tissues of terrestrial and marine species and recombinant systems. We then advocate the use of collagen type II as a building block in cartilage engineering approaches, based on safety, efficiency and efficacy data that have been derived over the years from numerous in vitro and in vivo studies.

An engineered tetra-valent antibody fully activates the Tie2 receptor with comparable potency to its natural ligand angiopoietin-1

Activation of the tyrosine kinase with Ig and epidermal growth factor homology domain 2 (Tie2) receptor by angiopoietin-1 (Ang1) is critical for vascular stabilization: it promotes survival signal transduction via auto-phosphorylation and reduces vascular permeability by strengthening tight junctions between endothelial cells. Thus, Tie2/Ang1 signaling is a promising therapeutic target for vascular diseases. However, in vivo use of existing Tie2 signaling modulators, such as recombinant Ang1, is restricted by limitations in manufacturability and stability. Here, we present a novel engineered tetra-valent agonistic antibody, ASP4021, which can specifically and fully activate the Tie2 receptor in an equivalent manner to Ang1. ASP4021 induced Tie2 self-phosphorylation and inhibited apoptosis in a human primary endothelial cell line. Additionally, single administration of ASP4021 significantly suppressed mustard-oil-induced vascular permeability in rats. ASP4021 may thus be a potential therapeutic candidate for diseases associated with vascular weakness such as diabetic retinopathy, diabetic macular edema and critical limb ischemia.

A Novel Anti-HER2 Bispecific Antibody With Potent Tumor Inhibitory Effects In Vitro and In Vivo

Overexpression of HER2 has been reported in many types of cancer, making it a perfect candidate for targeted immunotherapy. The combination of two FDA approved monoclonal antibodies (mAbs), trastuzumab and pertuzumab, has more robust anti-tumor activity in patients with HER2-overexpressing breast cancer. We recently produced a new humanized anti-HER2 mAb, hersintuzumab, which recognizes a different epitope than trastuzumab and pertuzumab on HER2. This mAb, in combination with trastuzumab, exhibits more potent anti-tumor activity than each parental mAb alone. Here we have developed a novel bispecific anti-HER2 antibody (BsAb) designated as trasintuzumab, composed of trastuzumab and hersintuzumab, using dual variable domain immunoglobulin (DVD-Ig) technology. Both variable domains of trasintuzumab are fully functional and have similar affinities to the parental mAbs and are also able to bind to natural HER2 on the surface of several HER2-expressing cell lines. Trasintuzumab was found to inhibit the growth of different types of tumor cell lines through suppression of the AKT and ERK signaling pathways as efficiently as the combination of the parental mAbs. It also induced tumor regression as potently as the combination of the two mAbs in nude mice bearing ovarian and gastric cancer xenografts. Our data suggest that trasintuzumab may be a promising BsAb therapeutic candidate for the treatment of HER2-overexpressing cancers.

Simple Approach to Accurately Predict Pharmacokinetics of Therapeutic Monoclonal Antibodies after Subcutaneous Injection in Humans

BACKGROUND AND OBJECTIVE

The subcutaneous injection of therapeutic monoclonal antibodies is increasingly used in the treatment of several diseases because of its convenience. Thus, a simple and accurate method of predicting the pharmacokinetics of monoclonal antibodies after a subcutaneous injection in humans would be a valuable tool for preclinical/clinical development. In this study, we investigated whether the pharmacokinetics of monoclonal antibodies after a subcutaneous injection in humans can be predicted using only pharmacokinetic data after a subcutaneous injection in cynomolgus monkeys.

METHODS

First, we compared the accuracy of three approaches to predict the apparent clearance (CL/F) and apparent volume of distribution (V_d/F) for 15 monoclonal antibodies in humans (1) allometric scaling from cynomolgus monkeys; (2) geometric mean of reported values in humans; (3) estimation from a regression line based on CL/F in humans [only V_d/F]). Then, using the predicted CL/F and V_d/F, and the geometric mean of reported absorption rate constant of mAbs the plasma concentration-time profiles of 13 monoclonal antibodies after subcutaneous injections in humans were simulated.

RESULTS

In a comparison of approaches, the first approach showed the best prediction accuracy for CL/F with an exponent of 0.9 (100% and 73% prediction accuracy within 2- and 1.5-fold of the observed value),and the third approach was the best for V_d/F (100% prediction accuracy within 1.5-fold of the observed value). Next, using the first approach for CL/F and the third approach for V_d/F, we accurately predicted the plasma concentration-time profiles of 13 monoclonal antibodies after subcutaneous injections in humans.

CONCLUSION

This simple approach can be applied in preclinical and clinical settings to predict the pharmacokinetics of monoclonal antibodies after subcutaneous injections in humans. Further, this approach requires only CL/F after a subcutaneous injection in cynomolgus monkeys, contributing to animal welfare and reducing costs.

Emerging therapeutic agents in osteoarthritis

Osteoarthritis (OA) is the most common joint disorder and a leading cause of disability. Current treatments for OA can improve symptoms but do not delay the progression of disease. In the last years, much effort has been devoted to developing new treatments for OA focused on pain control, inflammatory mediators or degradation of articular tissues. Although promising results have been obtained in ex vivo studies and animal models of OA, few of these agents have completed clinical trials. Available clinical data support the interest of nerve growth factor as a target in pain control as well as the disease-modifying potential of inhibitors of Wnt signaling or catabolic enzymes such as aggrecanases and cathepsin K, and anabolic strategies like fibroblast growth factor-18 or cellular therapies. Carefully controlled studies in patients selected according to OA phenotypes and with a long follow-up will help to confirm the relevance of these new approaches as emerging therapeutic treatments in OA.

Immunoglobulin Gamma-Like Therapeutic Bispecific Antibody Formats for Tumor Therapy

Bispecific antibodies (BsAbs) are a sort of dual functional proteins with specific binding to two distinct targets, which have become a focus of interest in antibody engineering and drug development research and have a promising future for wide applications in cancer immunotherapy and autoimmune disease. The key of clinical application and commercial-scale manufacturing of BsAbs is the amenability to assembly and purification of desired heterodimers. Advances in genetic engineering technology had resulted in the development of diverse BsAbs. Multiple recombinant strategies have been used to solve the mispairing problem between light and heavy chains, as well as to enforce accurate dimerization of heterologous heavy chains. There are 23 platforms available to generate 62 BsAbs which can be further divided into IgG-like ones and fragment-based ones, and more than 50 molecules are undergoing clinical trials currently. BsAbs with IgG-like architecture exhibit superior advantages in structure (similar to natural antibodies), pharmacokinetics, half-life, FcR-mediated function, and biological activity. This review considers various IgG-like BsAb generation approaches, summarizes the clinical applications of promising new BsAbs, and describes the mechanism of BsAbs in tumor therapy.

Investigational drugs for the treatment of osteoarthritis, an update on recent developments

INTRODUCTION

Osteoarthritis (OA) is the leading cause of pain, loss of function, and disability among elderly, with the knee the most affected joint. It is a heterogeneous condition characterized by complex and multifactorial etiologies which contribute to the broad variation in symptoms presentation and treatment responses that OA patients present. This poses a challenge for the development of effective treatment on OA.

AREAS COVERED

This review will discuss recent development of agents for the treatment of OA, updating our previous narrative review published in 2015. They include drugs for controlling local and systemic inflammation, regulating articular cartilage, targeting subchondral bone, and relieving pain.

EXPERT OPINION

Although new OA drugs such as monoclonal antibodies have shown marked effects and favorable tolerance, current treatment options for OA remain limited. The authors believe there is no miracle drug that can be used for all OA patients'; treatment and disease stage is crucial for the effectiveness of drugs. Therefore, early diagnosis, phenotyping OA patients and precise therapy would expedite the development of investigational drugs targeting at symptoms and disease progression of OA.

Expanding the Boundaries of Biotherapeutics with Bispecific Antibodies

Bispecific antibodies have moved from being an academic curiosity with therapeutic promise to reality, with two molecules being currently commercialized (Hemlibra® and Blincyto®) and many more in clinical trials. The success of bispecific antibodies is mainly due to the continuously growing number of mechanisms of actions (MOA) they enable that are not accessible to monoclonal antibodies. One of the earliest MOA of bispecific antibodies and currently the one with the largest number of clinical trials is the redirecting of the cytotoxic activity of T-cells for oncology applications, now extending its use in infective diseases. The use of bispecific antibodies for crossing the blood-brain barrier is another important application because of its potential to advance the therapeutic options for neurological diseases. Another noteworthy application due to its growing trend is enabling a more tissue-specific delivery or activity of antibodies. The different molecular solutions to the initial hurdles that limited the development of bispecific antibodies have led to the current diverse set of bispecific or multispecific antibody formats that can be grouped into three main categories: IgG-like formats, antibody fragment-based formats, or appended IgG formats. The expanded applications of bispecific antibodies come at the price of additional challenges for clinical development. The rising complexity in their structure may increase the risk of immunogenicity and the multiple antigen specificity complicates the selection of relevant species for safety assessment.

Therapeutic bispecific antibody formats: a patent applications review (1994-2017)

INTRODUCTION

Bispecific antibodies have become increasingly of interest by enabling new therapeutic applications such as retargeting cellular immunity towards tumor cells. About 23 bispecific antibody platforms have therefore been developed, generating about 62 molecules which are currently being evaluated for potential treatment of a variety of indications, such as cancer and inflammatory diseases, among which three molecules were approved. This class of drugs will represent a multi-million-dollar market over the coming years. Many companies have consequently invested in the development of bispecific antibody platforms, creating an important patent activity in this field.

AREAS COVERED

The present review gives an overview of the patent literature over the period 1994-2017 of different immunoglobulin gamma-based bispecific antibody platforms and the molecules approved or in clinical trials.

EXPERT OPINION

Bispecific antibodies are progressively accepted as potentially superior therapeutic molecules in a broad range of diseases. This frantic activity creates a maze of hundreds of patents that pose considerable legal risks for both newcomers and established companies. It can consecutively be anticipated that the number of patent conflicts will increase. Nevertheless, it can be expected that patents related to the use of a bispecific antibody will have tremendous commercial value.

Bispecific antibodies: design, therapy, perspectives

Antibodies (Abs) containing two different antigen-binding sites in one molecule are called bispecific. Bispecific Abs (BsAbs) were first described in the 1960s, the first monoclonal BsAbs were generated in the 1980s by hybridoma technology, and the first article describing the therapeutic use of BsAbs was published in 1992, but the number of papers devoted to BsAbs has increased significantly in the last 10 years. Particular interest in BsAbs is due to their therapeutic use. In the last decade, two BsAbs - catumaxomab in 2009 and blinatumomab in 2014, were approved for therapeutic use. Papers published in recent years have been devoted to various methods of BsAb generation by genetic engineering and chemical conjugation, and describe preclinical and clinical trials of these drugs in a variety of diseases. This review considers diverse BsAb-production methods, describes features of therapeutic BsAbs approved for medical use, and summarizes the prospects of practical application of promising new BsAbs.

Targeting Anti-TGF-β Therapy to Fibrotic Kidneys with a Dual Specificity Antibody Approach

Targeted delivery of a therapeutic agent to a site of pathology to ameliorate disease while limiting exposure at undesired tissues is an aspirational treatment scenario. Targeting diseased kidneys for pharmacologic treatment has had limited success. We designed an approach to target an extracellular matrix protein, the fibronectin extra domain A isoform (FnEDA), which is relatively restricted in distribution to sites of tissue injury. In a mouse unilateral ureteral obstruction (UUO) model of renal fibrosis, injury induced significant upregulation of FnEDA in the obstructed kidney. Using dual variable domain Ig (DVD-Ig) technology, we constructed a molecule with a moiety to target FnEDA and a second moiety to neutralize TGF-β After systemic injection of the bispecific TGF-β + FnEDA DVD-Ig or an FnEDA mAb, chemiluminescent detection and imaging with whole-body single-photon emission computed tomography (SPECT) revealed significantly higher levels of each molecule in the obstructed kidney than in the nonobstructed kidney, the ipsilateral kidney of sham animals, and other tissues. In comparison, a systemically administered TGF-β mAb accumulated at lower concentrations in the obstructed kidney and exhibited a more diffuse whole-body distribution. Systemic administration of the bispecific DVD-Ig or the TGF-β mAb (1-10 mg/kg) but not the FnEDA mAb attenuated the injury-induced collagen deposition detected by immunohistochemistry and elevation in Col1a1, FnEDA, and TIMP1 mRNA expression in the obstructed kidney. Overall, systemic delivery of a bispecific molecule targeting an extracellular matrix protein and delivering a TGF-β mAb resulted in a relatively focal uptake in the fibrotic kidney and reduced renal fibrosis.

Safety, tolerability, and pharmacodynamics of an anti-interleukin-1α/β dual variable domain immunoglobulin in patients with osteoarthritis of the knee: a randomized phase 1 study

OBJECTIVE

To investigate the safety, tolerability, pharmacokinetics, and pharmacodynamics of ABT-981, a human dual variable domain immunoglobulin simultaneously targeting interleukin (IL)-1α and IL-1β, in patients with knee osteoarthritis (OA).

METHOD

This was a randomized, double-blind, placebo-controlled, single-center study of multiple subcutaneous (SC) injections of ABT-981 in patients with mild-to-moderate OA of the knee (NCT01668511). Three cohorts received ABT-981 (0.3, 1, or 3 mg/kg) or placebo every other week for a total of four SC injections, and one cohort received ABT-981 (3 mg/kg) or placebo every 4 weeks for a total of three SC injections. Assessment of safety and tolerability were the primary objectives. A panel of serum and urine biomarkers of inflammation and joint degradation were evaluated.

RESULTS

A total of 36 patients were randomized (ABT-981, n = 28; placebo, n = 8); 31 (86%) completed the study. Adverse event (AE) rates were comparable between ABT-981 and placebo (54% vs 63%). The most common AE reported with ABT-981 vs placebo was injection site erythema (14% vs 0%). ABT-981 significantly reduced absolute neutrophil count and serum concentrations of IL-1α/IL-1β, high-sensitivity C-reactive protein, and matrix metalloproteinase (MMP)-derived type 1 collagen. Serum concentrations of MMP-derived type 3 collagen and MMP-degraded C-reactive protein demonstrated decreasing trends with ABT-981. Antidrug antibodies were found in 37% of patients but were not associated with the incidence or severity of AEs.

CONCLUSION

ABT-981 was generally well tolerated in patients with knee OA and engaged relevant tissue targets, eliciting an anti-inflammatory response. Consequently, ABT-981 may provide clinical benefit to patients with inflammation-driven OA.

Harnessing a catalytic lysine residue for the one-step preparation of homogeneous antibody-drug conjugates

Current strategies to produce homogeneous antibody-drug conjugates (ADCs) rely on mutations or inefficient conjugation chemistries. Here we present a strategy to produce site-specific ADCs using a highly reactive natural buried lysine embedded in a dual variable domain (DVD) format. This approach is mutation free and drug conjugation proceeds rapidly at neutral pH in a single step without removing any charges. The conjugation chemistry is highly robust, enabling the use of crude DVD for ADC preparation. In addition, this strategy affords the ability to precisely monitor the efficiency of drug conjugation with a catalytic assay. ADCs targeting HER2 were prepared and demonstrated to be highly potent and specific in vitro and in vivo. Furthermore, the modular DVD platform was used to prepare potent and specific ADCs targeting CD138 and CD79B, two clinically established targets overexpressed in multiple myeloma and non-Hodgkin lymphoma, respectively.

Current strategies for producing antibody-drug conjugates often rely on inefficient conjugation chemistry or on generating mutations in the antibody sequence. Here the authors demonstrate a mutation-free, single-step conjugation platform utilizing a buried lysine residue.

Regenerative approaches for cartilage repair in the treatment of osteoarthritis

Osteoarthritis (OA) as a debilitating affliction of joints currently affects millions of people and remains an unsolved problem. The disease involves multiple cellular and molecular pathways that converge on the progressive destruction of cartilage. Activation of cartilage regenerative potential and specific targeting pathogenic mediators have been the major focus of research efforts aimed at slowing the progression of cartilage degeneration and preserve joint function. This review will summarize recent key discoveries toward better understanding of the complex mechanisms behind OA development and highlight the latest advances in basic and clinical research in the approach for cartilage regeneration. Prospectively, more potent therapeutic strategies against progressive cartilage deterioration may use a combination of cytotherapy, pharmacotherapy, and bioscaffoldings for improved chondrogenic differentiation and stem/progenitor cell homing as well as the concomitant reduced enzymatic matrix degradation and inflammation. Further, treatments need to be provided with increased preciseness of targeted therapy. One might expect that the regenerative therapies could potentially control or even possibly cure OA if performed at early stages of the disease.

Cytokines of the IL-1 family: recognized targets in chronic inflammation underrated in organ transplantations

Interleukin 1 (IL-1) family is a group of cytokines with multiple local and systemic effects, which regulates both innate and adaptive immune responses. Generally, most IL-1 family cytokines express prevailing pro-inflammatory activities (IL-1α, IL-1β, IL-18, IL-33, IL-36 α, β, γ), whereas others are anti-inflammatory (IL-1Ra (IL-1 receptor antagonist), IL-36Ra, IL-38, IL-37). In addition to their immunomodulatory roles, some of them are also involved in the physiological modulation of homeostatic processes and directly affect mRNA transcription. IL-1 family cytokines bind to specific receptors composed of a ligand-binding chain and an accessory chain. The pro-inflammatory effects of IL-1 family cytokines are regulated on the level of transcription, enzymatic processing of precursors, release of soluble antagonists, and expression of decoy receptors. Members of the IL-1 family regulate the recruitment and activation of effector cells involved in innate and adaptive immunity, but they are also involved in the pathogenesis of chronic disorders, including inflammatory bowel disease, rheumatoid arthritis, and various autoimmune and autoinflammatory diseases. There are only limited data regarding the role of IL-1 cytokines in transplantation. In recent years, targeted therapeutics affecting IL-1 have been used in multiple clinical studies. In addition to the recombinant IL-1Ra, anakinra (highly effective in autoinflammatory diseases and tested for other chronic diseases), the monoclonal antibodies canakinumab, gevokizumab, and rilonacept (a long-acting IL-1 receptor fusion protein) provide further options to block IL-1 activity. Furthermore, new inhibitors of IL-18 (GSK 1070806, ABT-325, rIL-18BP (IL-18 binding protein)) and IL-33 (CNTO-7160) are presently under clinical studies and other molecules are being developed to target IL-1 family cytokines.

Engineering bispecific antibodies with defined chain pairing

Bispecific IgG-like antibodies can simultaneously interact with two epitopes on the same or on different antigens. Therefore, these molecules facilitate novel modes of action, which cannot be addressed by conventional monospecific IgGs. However, the generation of such antibodies still appears to be demanding due to their specific architecture comprising four different polypeptide chains that need to assemble correctly. This review focusses on different strategies to circumvent this issue or to enforce a correct chain association with a focus on common-chain bispecific antibodies.