Structural characterization of a human Fc fragment engineered for lack of effector functions

In vivo delivery of engineered synthetic DNA-encoded SARS-CoV-2 monoclonal antibodies for pre-exposure prophylaxis in non-human primates

COVID-19 remains a major public health concern. Monoclonal antibodies have received emergency use authorization (EUA) for pre-exposure prophylaxis against COVID-19 among high-risk groups for treatment of mild to moderate COVID-19. In addition to recombinant biologics, engineered synthetic DNA-encoded antibodies (DMAb) are an important strategy for direct in vivo delivery of protective mAb. A DMAb cocktail was synthetically engineered to encode the immunoglobulin heavy and light chains of two different two different Fc-engineered anti-SARS-CoV-2 antibodies. The DMAbs were designed to enhance in vivo expression and delivered intramuscularly to cynomolgus and rhesus macaques with a modified in vivo delivery regimen. Serum levels were detected in macaques, along with specific binding to SARS-CoV-2 spike receptor binding domain protein and neutralization of multiple SARS-CoV-2 variants of concern in pseudovirus and authentic live virus assays. Prophylactic administration was protective in rhesus macaques against signs of SARS-CoV-2 (USA-WA1/2020) associated disease in the lungs. Overall, the data support further study of DNA-encoded antibodies as an additional delivery mode for prevention of COVID-19 severe disease. These data have implications for human translation of gene-encoded mAbs for emerging infectious diseases and low dose mAb delivery against COVID-19.

Antitumor activity of Z15-0-2, a bispecific nanobody targeting PD-1 and CTLA-4

The combination of programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA-4) antibodies has potential for enhancing clinical efficacy. We described the development and antitumor activity of Z15-0, a bispecific nanobody targeting both the PD-1 and CTLA-4 pathways simultaneously. We designed and optimized the mRNA sequence encoding Z15-0, referred to as Z15-0-2 and through a series of in vitro and in vivo experiments, we established that the optimized Z15-0-2 mRNA sequence significantly increased the expression of the bispecific nanobody. Administration of Z15-0-2 mRNA to tumor-bearing mice led to greater inhibition of tumor growth compared to controls. In aggregate, we introduced a novel bispecific nanobody and have re-engineered it to boost expression of mRNA, representing a new drug development paradigm.

Accelerating therapeutics development during a pandemic: population pharmacokinetics of the long-acting antibody combination AZD7442 (tixagevimab/cilgavimab) in the prophylaxis and treatment of COVID-19

AZD7442 is a combination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-neutralizing antibodies, tixagevimab and cilgavimab, developed for pre-exposure prophylaxis (PrEP) and treatment of coronavirus disease 2019 (COVID-19). Using data from eight clinical trials, we describe a population pharmacokinetic (popPK) model of AZD7442 and show how modeling of "interim" data accelerated decision-making during the COVID-19 pandemic. The final model was a two-compartmental distribution model with first-order absorption and elimination, including standard allometric exponents for the effect of body weight on clearance and volume. Other covariates included were as follows: sex, age >65 years, body mass index ≥30 kg/m2, and diabetes on absorption rate; diabetes on clearance; Black race on central volume; and intramuscular (IM) injection site on bioavailability. Simulations indicated that IM injection site and body weight had > 20% effects on AZD7442 exposure, but no covariates were considered to have a clinically relevant impact requiring dose adjustment. The pharmacokinetics of AZD7442, cilgavimab, and tixagevimab were comparable and followed linear kinetics with extended half-lives (median 78.6 days for AZD7442), affording prolonged protection against susceptible SARS-CoV-2 variants. Comparison of popPK simulations based on "interim data" with a target concentration based on 80% viral inhibition and assuming 1.81% partitioning into the nasal lining fluid supported a decision to double the PrEP dosage from 300 mg to 600 mg to prolong protection against Omicron variants. Serum AZD7442 concentrations in adolescents weighing 40-95 kg were predicted to be only marginally different from those observed in adults, supporting authorization for use in adolescents before clinical data were available. In these cases, popPK modeling enabled accelerated clinical decision-making.

Plant-derived Durvalumab variants show efficient PD-1/PD-L1 blockade and therapeutically favourable FcR binding

Immune checkpoint blocking therapy targeting the PD-1/PD-L1 inhibitory signalling pathway has produced encouraging results in the treatment of a variety of cancers. Durvalumab (Imfinzi®) targeting PD-L1 is currently used for immunotherapy of several tumour malignancies. The Fc region of this IgG1 antibody has been engineered to reduce FcγR interactions with the aim of enhancing blockade of PD-1/PD-L1 interactions without the depletion of PD-L1-expressing immune cells. Here, we used Nicotiana benthamiana to produce four variants of Durvalumab (DL): wild-type IgG1 and its 'Fc-effector-silent' variant (LALAPG) carrying further modifications to increase antibody half-life (YTE); IgG4S228P and its variant (PVA) with Fc mutations to decrease binding to FcγRI. In addition, DL variants were produced with two distinct glycosylation profiles: afucosylated and decorated with α1,6-core fucose. Plant-derived DL variants were compared to the therapeutic antibody regarding their ability to (i) bind to PD-L1, (ii) block PD-1/PD-L1 inhibitory signalling and (iii) engage with the neonatal Fc receptor (FcRn) and various Fcγ receptors. It was found that plant-derived DL variants bind to recombinant PD-L1 and to PD-L1 expressed in gastrointestinal cancer cells and are able to effectively block its interaction with PD-1 on T cells, thereby enhancing their activation. Furthermore, we show a positive impact of Fc amino acid mutations and core fucosylation on DL's therapeutic potential. Compared to Imfinzi®, DL-IgG1 (LALAPG) and DL-IgG4 (PVA)S228P show lower affinity to CD32B inhibitory receptor which can be therapeutically favourable. Importantly, DL-IgG1 (LALAPG) also shows enhanced binding to FcRn, a key determinant of serum half-life of IgGs.

Safety, Efficacy and Pharmacokinetics of AZD7442 (Tixagevimab/Cilgavimab) for Treatment of Mild-to-Moderate COVID-19: 15-Month Final Analysis of the TACKLE Trial

INTRODUCTION

In the phase 3 TACKLE study, outpatient treatment with AZD7442 (tixagevimab/cilgavimab) was well tolerated and significantly reduced progression to severe disease or death through day 29 in adults with mild-to-moderate coronavirus disease 2019 (COVID-19) at the primary analysis. Here, we report data from the final analysis of the TACKLE study, performed after approximately 15 months' follow-up.

METHODS

Eligible participants were randomized 1:1 and dosed within 7 days of symptom onset with 600 mg intramuscular AZD7442 (n = 456; 300 mg tixagevimab/300 mg cilgavimab) or placebo (n = 454).

RESULTS

Severe COVID-19 or death through day 29 occurred in 4.4% and 8.8% of participants who received AZD7442 or placebo, a relative risk reduction (RRR) of 50.4% [95% confidence interval (CI) 14.4, 71.3; p = 0.0096]; among participants dosed within 5 days of symptom onset, the RRR was 66.9% (95% CI 31.1, 84.1; p = 0.002). Death from any cause or hospitalization for COVID-19 complications or sequelae through day 169 occurred in 5.0% of participants receiving AZD7442 versus 9.7% receiving placebo, an RRR of 49.2% (95% CI 14.7, 69.8; p = 0.009). Adverse events occurred in 55.5% and 55.9% of participants who received AZD7442 or placebo, respectively, and were mostly mild or moderate in severity. Serious adverse events occurred in 10.2% and 14.4% of participants who received AZD7442 or placebo, respectively, and deaths occurred in 1.8% of participants in both groups. Serum concentration-time profiles recorded over 457 days were similar for AZD7442, tixagevimab, and cilgavimab, and were consistent with the extended half-life reported for AZD7442 (approx. 90 days).

CONCLUSIONS

AZD7442 reduced the risk of progression to severe COVID-19, hospitalization, and death, was well tolerated through 15 months, and exhibited predictable pharmacokinetics in outpatients with mild-to-moderate COVID-19. These data support the long-term safety of using long-acting monoclonal antibodies to treat COVID-19.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT04723394. ( https://clinicaltrials.gov/study/NCT04723394 .

Infusion-Related Reactions Subsequent to Avelumab, Durvalumab, and Atezolizumab Administration: A Retrospective Observational Study

BACKGROUND

Avelumab, durvalumab, and atezolizumab are anti-programmed death-ligand 1 (PD-L1) antibodies approved for clinical application in Japan. Despite targeting the same molecule, avelumab elicits a different frequency of infusion-related reactions (IRRs) compared with durvalumab and atezolizumab, leading to differences in premedication recommendations. This study aimed to collect information to verify the relationship during IRRs and the characteristics of antibody molecules, by investigating the frequency of IRRs caused by three types of antibodies and the actual status of prophylactic measures.

METHODS

This single-center, retrospective observational study collected the medical records of 73 patients who received avelumab, durvalumab, or atezolizumab at Osaka University Hospital.

RESULTS

The frequency of IRRs was 50.0% (12/24) for avelumab, 31.0% (8/27) for durvalumab, and 18.2% (4/22) for atezolizumab. The IRRs were grade 2 in seven patients and grade 1 in five patients treated with avelumab, grade 2 in six patients and grade 1 in two patients treated with durvalumab, and grade 1 in all patients treated with atezolizumab. Among patients in whom symptoms were observed during the first administration, measures were taken to prevent IRRs for the second administration, but cases were confirmed in which symptoms reappeared, especially in patients who received durvalumab.

CONCLUSION

Our findings indicate that the frequency of IRRs due to anti-PD-L1 antibodies is higher than that previously reported in clinical trials and different modifications in antibody molecules may affect the difference in IRR frequency.

Tissue factor overexpression promotes resistance to KRAS-G12C inhibition in non-small cell lung cancer

The recently approved KRASG12C mutation-specific inhibitors sotorasib and adagrasib (KRASG12C-I) represent a promising therapy for KRASG12C-driven non-small cell lung cancer (NSCLC). However, many eligible patients do not benefit due to intrinsic or acquired drug resistance. Tissue factor (TF) is overexpressed in KRAS-mutated (KRASmut) NSCLC and is the target of the FDA-approved ADC Tivdak. Here, we employed HuSC1-39, the parent antibody of a clinical stage TF-ADC (NCT04843709), to investigate the role of TF in KRASmut NSCLC. We found that patients with TF-overexpression had poor survival, elevated P-ERK/P-AKT activity levels and low immune effector cell infiltration in the tumor. In a panel of KRASG12C cell lines, KRASG12C-I response correlated with suppression of TF mRNA, which was not observed in resistant cells. In the drug resistant cells, TF-overexpression relied on an mTORC2-mediated and proteasome-dependent pathway. Combination treatment of HuSC1-39 or mTORC1/2 inhibitor MTI-31 with KRASG12C-I each produced synergistic antitumor efficacy in cell culture and in an orthotopic lung tumor model. TF-depletion in the resistant cells diminished epithelial mesenchymal transition, reduced tumor growth and greatly sensitized KRASG12C-I response. Moreover, employing immunohistochemistry and coculture studies, we demonstrated that HuSC1-39 or MTI-31 reset the tumor microenvironment and restore KRASG12C-I sensitivity by reshaping an M1-like macrophage profile with greatly enhanced phagocytic capacity toward tumor cell killing. Thus, we have identified the TF/mTORC2 axis as a critical new mechanism for triggering immunosuppression and KRASG12C-I resistance. We propose that targeting this axis with HuSC1-39 or MTI-31 will improve KRASG12C-I response in KRAS-driven NSCLC.

Impact of structural modifications of IgG antibodies on effector functions

Immunoglobulin G (IgG) antibodies are a critical component of the adaptive immune system, binding to and neutralizing pathogens and other foreign substances. Recent advances in molecular antibody biology and structural protein engineering enabled the modification of IgG antibodies to enhance their therapeutic potential. This review summarizes recent progress in both natural and engineered structural modifications of IgG antibodies, including allotypic variation, glycosylation, Fc engineering, and Fc gamma receptor binding optimization. We discuss the functional consequences of these modifications to highlight their potential for therapeutical applications.

Anifrolumab: first biologic approved in the EU not restricted to patients with a high degree of disease activity for the treatment of moderate to severe systemic lupus erythematosus

INTRODUCTION

Type 1 interferons (IFNs) play a crucial role in the pathogenesis of systemic lupus erythematosus (SLE) and various type I IFNs targeting therapeutic approaches have been developed. Anifrolumab, a monoclonal antibody that binds to the subunit 1 of the type I IFN receptor, has acquired considerable interest and has entered different clinical human trials willing to evaluate its efficacy and safety.

AREAS COVERED

This review summarizes the data obtained in phases 1, 2, and 3 clinical trials of anifrolumab for SLE patients. A focus is made on data of clinical efficacy and safety obtained in MUSE, TULIP-1 and TULIP-2 trials.

EXPERT OPINION/COMMENTARY

Anifrolumab is a promising therapeutic option for patients with SLE, currently authorized for moderate-to-severe SLE. Extensive real-world use is now going to generate data required to gain experience on the type of patients who benefit the most from the drug, and the exact positioning of anifrolumab in the therapeutic plan.

Conformation-selective rather than avidity-based binding to tumor associated antigen derived peptide-MHC enables targeting of WT1-pMHC low expressing cancer cells by anti-WT1-pMHC/CD3 T cell engagers

T cell engagers, a category of T cell-retargeting immunotherapy, are rapidly transforming clinical cancer care. However, the lack of tumor-specific targets poses a significant roadblock for broad adaptation of this therapeutic modality in many indications, often resulting in systemic on-target off-tumor toxicity. Though various tumor-derived intracellular mutations provide a massive pool of potential tumor-specific antigens, targeting them is extremely challenging, partly due to the low copy number of tumor associated antigen (TAA)-derived pMHC on tumor cell surface. Further, the interplay of binding geometry and format valency in relation to the capacity of a T cell engager to efficiently target low density cell-surface pMHC is not well understood. Using the Wilms' tumor 1 (WT1) oncoprotein as a proof-of-principle TAA, combined with an array of IgG-like T cell engager modalities that differ in their anti-TAA valency and binding geometry, we show that the ability to induce an immunological synapse formation, resulting in potent killing of WT1 positive cancer cell lines is primarily dependent on the distinct geometrical conformations between the Fab arms of anti-WT1-HLA-A*02:01 and anti-CD3. The augmented avidity conferred by the binding of two anti-WT1-HLA-A*02:01 Fab arms has only minimal influence on cell killing potency. These findings demonstrate the need for careful examination of key design parameters for the development of next-generation T cell engagers targeting low density TAA-pMHCs on tumor cells.

Siglec-7 glyco-immune binding mAbs or NK cell engager biologics induce potent antitumor immunity against ovarian cancers

Ovarian cancer (OC) is a lethal gynecologic malignancy, with modest responses to CPI. Engagement of additional immune arms, such as NK cells, may be of value. We focused on Siglec-7 as a surface antigen for engaging this population. Human antibodies against Siglec-7 were developed and characterized. Coculture of OC cells with PBMCs/NKs and Siglec-7 binding antibodies showed NK-mediated killing of OC lines. Anti-Siglec-7 mAb (DB7.2) enhanced survival in OC-challenged mice. In addition, the combination of DB7.2 and anti-PD-1 demonstrated further improved OC killing in vitro. To use Siglec-7 engagement as an OC-specific strategy, we engineered an NK cell engager (NKCE) to simultaneously engage NK cells through Siglec-7, and OC targets through FSHR. The NKCE demonstrated robust in vitro killing of FSHR+ OC, controlled tumors, and improved survival in OC-challenged mice. These studies support additional investigation of the Siglec-7 targeting approaches as important tools for OC and other recalcitrant cancers.

Profiling the Biophysical Developability Properties of Common IgG1 Fc Effector Silencing Variants

Therapeutic antibodies represent the most significant modality in biologics, with around 150 approved drugs on the market. In addition to specific target binding mediated by the variable fragments (Fvs) of the heavy and light chains, antibodies possess effector functions through binding of the constant region (Fc) to Fcγ receptors (FcγR), which allow immune cells to attack and kill target cells using a variety of mechanisms. However, for some applications, including T-cell-engaging bispecifics, this effector function is typically undesired. Mutations within the lower hinge and the second constant domain (CH2) of IgG1 that comprise the FcγR binding interface reduce or eliminate effector function ("Fc silencing") while retaining binding to the neonatal Fc receptor (FcRn), important for normal antibody pharmacokinetics (PKs). Comprehensive profiling of biophysical developability properties would benefit the choice of constant region variants for development. Here, we produce a large panel of representative mutations previously described in the literature and in many cases in clinical or approved molecules, generate select combinations thereof, and characterize their binding and biophysical properties. We find that some commonly used CH2 mutations, including D265A and P331S, are effective in reducing binding to FcγR but significantly reduce stability, promoting aggregation, particularly under acidic conditions commonly employed in manufacturing. We highlight mutation sets that are particularly effective for eliminating Fc effector function with the retention of WT-like stability, including L234A, L235A, and S267K (LALA-S267K), L234A, L235E, and S267K (LALE-S267K), L234A, L235A, and P329A (LALA-P329A), and L234A, L235E, and P329G (LALE-P329G).

Mutation of the TGN1412 anti-CD28 monoclonal antibody lower hinge confers specific FcγRIIb binding and retention of super-agonist activity

The agonistic action of several immunomodulatory monoclonal antibodies (mAbs) requires both target antigen binding and clustering of this mAb:target complex by the Fcs interacting with Fcγ receptors (FcγRs), in particular FcγRIIb, on neighboring bystander cells. Fc mutations were made in the immunoglobulin G4 (IgG4)-based TGN1412 anti-CD28 mAb to define the role of FcγR interactions in its "super-agonist" activity. The dual mutation, IgG4-ED269,270 AA, ablated interaction with all human FcγRs and agonistic action was consequentially lost, confirming the FcγR dependence on the action of TGN1412. The IgG4 lower hinge region (F234 L235 G236 G237 ) was modified by L235 E mutation (F234 E235 G236 G237 ), a mutation commonly used to ablate FcγR binding, including in approved therapeutic mAbs. However, rather than ablating all FcγR binding, IgG4-L235 E conferred specific binding to FcγRIIb, the inhibitory Fc receptor. Furthermore, in combination with the core hinge-stabilizing mutation (IgG4-S228 P, L235 E), this mutation increased affinity for FcγRIIb compared with wild-type IgG4. In addition to having FcγRIIb specificity, these engineered TGN1412 antibodies retained their super-agonistic ability, demonstrating that CD28- and FcγRIIb-specific binding are together sufficient for agonistic function. The FcγRIIb-specific nature of IgG4-L235 E has utility for mAb-mediated immune agonism therapies that are dependent on FcγRIIb interaction and of anti-inflammatory mAbs in allergy and autoimmunity that harness FcγRIIb inhibitory signaling.

Clinical Pharmacokinetics, Pharmacodynamics, and Immunogenicity of Anifrolumab

The type I interferon (IFN) signaling pathway is implicated in the pathogenesis of systemic lupus erythematosus (SLE). Anifrolumab is a monoclonal antibody that targets the type I IFN receptor subunit 1. Anifrolumab is approved in several countries for patients with moderate to severe SLE receiving standard therapy. The approved dosing regimen of anifrolumab is a 300-mg dose administered intravenously every 4 weeks; this was initially based on the results of the Phase 2b MUSE and further confirmed in the Phase 3 TULIP-1 and TULIP-2 trials, in which anifrolumab 300-mg treatment was associated with clinically meaningful improvements in disease activity with an acceptable safety profile. There have been several published analyses of the pharmacokinetic and pharmacodynamic profile of anifrolumab, including a population-pharmacokinetic analysis of 5 clinical studies of healthy volunteers and patients with SLE, in which body weight and type I IFN gene expression were significant covariates identified for anifrolumab exposure and clearance. Additionally, the pooled Phase 3 SLE population has been used to evaluate how serum exposure may be related to clinical responses, safety risks, and pharmacodynamic effects of the 21-gene type I IFN gene signature (21-IFNGS). The relevance of 21-IFNGS with regard to clinical efficacy outcomes has also been analyzed. Herein, the clinical pharmacokinetics, pharmacodynamics, and immunogenicity of anifrolumab as well as results of population-pharmacokinetics and exposure-response analyses are reviewed.

The Landscape of Neutralizing Monoclonal Antibodies (nAbs) for Treatment and Prevention of COVID-19

Purpose

After nearly 3 years of the COVID-19 pandemic, even though a vast body of knowledge and products (including vaccines and treatments) have been developed and disseminated, the virus is still evolving and new variants arising. Consequently, thousands of lives continue to be lost. Neutralizing monoclonal antibodies (nAbs) are promising drugs that emerged to treat SARS-CoV-2. In the uncertainty of the current situation, there is the question of whether organizations should continue to invest in this technology. To help decision-making in scientifical and pharmaceutical organizations, it is of major importance to monitor the development of products and technologies. Therefore, the aim of this study is analyze the landscape of nAbs for COVID-19.

Methods

The scenario of 473 biotherapeutics focusing on nAbs was evaluated using foresight techniques and a review of literature. Data were obtained from structured and semi-structured databases and processed for treatment, cleaning, consistency, validation, and enrichment.

Results

We identified 227 nAbs and performed an extensive literature review of 16 nAbs in late clinical development, including development technologies, responses to variants of concern (VOCs), manufacturing, and clinical aspects.

Conclusions

Even though the emergence of new VOCs is a threat to the effectiveness of this treatment, demanding constant genomic surveillance, the use of nAbs to treat and prevent COVID-19 will probably continue to be relevant due to excellent safety profiles and the possibility of immediate immunity transfer, especially in patients showing inadequate immunological response to vaccination. Therefore, we suggest that organizations should keep investing in improvements in this technology.

Developability profiling of a panel of Fc engineered SARS-CoV-2 neutralizing antibodies

To combat the COVID-19 pandemic, potential therapies have been developed and moved into clinical trials at an unprecedented pace. Some of the most promising therapies are neutralizing antibodies against SARS-CoV-2. In order to maximize the therapeutic effectiveness of such neutralizing antibodies, Fc engineering to modulate effector functions and to extend half-life is desirable. However, it is critical that Fc engineering does not negatively impact the developability properties of the antibodies, as these properties play a key role in ensuring rapid development, successful manufacturing, and improved overall chances of clinical success. In this study, we describe the biophysical characterization of a panel of Fc engineered ("TM-YTE") SARS-CoV-2 neutralizing antibodies, the same Fc modifications as those found in AstraZeneca's Evusheld (AZD7442; tixagevimab and cilgavimab), in which the TM modification (L234F/L235E/P331S) reduce binding to FcγR and C1q and the YTE modification (M252Y/S254T/T256E) extends serum half-life. We have previously shown that combining both the TM and YTE Fc modifications can reduce the thermal stability of the CH2 domain and possibly lead to developability challenges. Here we show, using a diverse panel of TM-YTE SARS-CoV-2 neutralizing antibodies, that despite lowering the thermal stability of the Fc CH2 domain, the TM-YTE platform does not have any inherent developability liabilities and shows an in vivo pharmacokinetic profile in human FcRn transgenic mice similar to the well-characterized YTE platform. The TM-YTE is therefore a developable, effector function reduced, half-life extended antibody platform.

Interplay of heavy chain introns influences efficient transcript splicing and affects product quality of recombinant biotherapeutic antibodies from CHO cells

Introns are included in genes encoding therapeutic proteins for their well-documented function of boosting expression. However, mis-splicing of introns in recombinant immunoglobulin (IgG) heavy chain (HC) transcripts can produce amino acid sequence product variants. These variants can affect product quality; therefore, purification process optimization may be needed to remove them, or if they cannot be removed, then in-depth characterization must be carried out to understand their effects on biological activity. In this study, HC transgene engineering approaches were investigated and were successful in significantly reducing the previously identified IgG HC splice variants to <0.5%. Subsequently, a comprehensive evaluation was conducted to understand the influence of the different introns in the HC genes on the expression of recombinant biotherapeutic antibodies. The data revealed an unexpected cooperation between specific introns for efficient splicing, where intron retention led to significant reductions in IgG expression of up to 75% for some intron combinations. Furthermore, it was shown that HC introns could be fully removed without significantly affecting productivity. This work paves the way for future biotherapeutic antibody transgene design with regard to inclusion of HC introns. By removing unnecessary introns, transgene mRNA transcript will no longer be mis-spliced, thereby eliminating HC splice variants and improving antibody product quality.

Tixagevimab/Cilgavimab in SARS-CoV-2 Prophylaxis and Therapy: A Comprehensive Review of Clinical Experience

Effective treatments and vaccines against COVID-19 used in clinical practice have made a positive impact on controlling the spread of the pandemic, where they are available. Nevertheless, even if fully vaccinated, immunocompromised patients still remain at high risk of adverse outcomes. This has driven the largely expanding field of monoclonal antibodies, with variable results. Tixagevimab/Cilgavimab (AZD7442), a long-acting antibody combination that inhibits the attachment of the SARS-CoV-2 spike protein to the surface of cells, has proved promising in reducing the incidence of symptomatic COVID-19 or death in high-risk individuals without major adverse events when given as prophylaxis, as well as early treatment. Real-world data confirm the antibody combination's prophylaxis efficacy in lowering the incidence, hospitalization, and mortality associated with COVID-19 in solid organ transplant recipients, patients with immune-mediated inflammatory diseases and hematological malignancies, and patients in B-cell-depleting therapies. Data suggest a difference in neutralization efficiency between the SARS-CoV-2 subtypes in favor of the BA.2 over the BA.1. In treating COVID-19, AZD7442 showed a significant reduction in severe COVID-19 cases and mortality when given early in the course of disease, and within 5 days of symptom onset, without being associated with severe adverse events, even when it is used in addition to standard care. The possibility of the development of spike-protein mutations that resist monoclonal antibodies has been reported; therefore, increased vigilance is required in view of the evolving variants. AZD7442 may be a powerful ally in preventing COVID-19 and the mortality associated with it in high-risk individuals. Further research is required to include more high-risk groups and assess the concerns limiting its use, along the SARS-CoV-2 evolutionary trajectory.

Tixagevimab/cilgavimab for prevention and treatment of COVID-19: a review

INTRODUCTION

There is a need to protect vulnerable individuals who do not respond to vaccination against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), particularly following the emergence of new variants. Tixagevimab/cilgavimab, the only monoclonal antibody combination authorized for pre-exposure prophylaxis of coronavirus disease 2019 (COVID-19), demonstrated efficacy in unvaccinated individuals in the PROVENT study.

AREAS COVERED

This review focuses predominantly on real-world evidence examining the effectiveness and safety of tixagevimab/cilgavimab in populations who are immunocompromised and otherwise vulnerable. The ability of tixagevimab/cilgavimab to neutralize Omicron subvariants, the appropriate dosage in vulnerable populations, and the impact of prior vaccination on tixagevimab/cilgavimab effectiveness are also discussed.

EXPERT OPINION

The tixagevimab/cilgavimab combination is important in providing protection in people who either cannot have a full vaccination or respond poorly to COVID-19 vaccines. Abundant clinical data have emerged to inform clinical use in adults in need, although some additional data-formal pediatric and adolescent studies, plus information on optimal doses required to protect against emerging variants, and the ideal interval between tixagevimab/cilgavimab dosing and vaccination-would be welcomed. Importantly, despite the current effectiveness of tixagevimab/cilgavimab, we must recognize the possibility that resistant SARS-CoV-2 variants could emerge in the future.

DNA-delivered antibody cocktail exhibits improved pharmacokinetics and confers prophylactic protection against SARS-CoV-2

Monoclonal antibody therapy has played an important role against SARS-CoV-2. Strategies to deliver functional, antibody-based therapeutics with improved in vivo durability are needed to supplement current efforts and reach underserved populations. Here, we compare recombinant mAbs COV2-2196 and COV2-2130, which compromise clinical cocktail Tixagevimab/Cilgavimab, with optimized nucleic acid-launched forms. Functional profiling of in vivo-expressed, DNA-encoded monoclonal antibodies (DMAbs) demonstrated similar specificity, broad antiviral potency and equivalent protective efficacy in multiple animal challenge models of SARS-CoV-2 prophylaxis compared to protein delivery. In PK studies, DNA-delivery drove significant serum antibody titers that were better maintained compared to protein administration. Furthermore, cryo-EM studies performed on serum-derived DMAbs provide the first high-resolution visualization of in vivo-launched antibodies, revealing new interactions that may promote cooperative binding to trimeric antigen and broad activity against VoC including Omicron lineages. These data support the further study of DMAb technology in the development and delivery of valuable biologics.

Tixagevimab-cilgavimab for treatment of patients hospitalised with COVID-19: a randomised, double-blind, phase 3 trial

BACKGROUND

Tixagevimab-cilgavimab is a neutralising monoclonal antibody combination hypothesised to improve outcomes for patients hospitalised with COVID-19. We aimed to compare tixagevimab-cilgavimab versus placebo, in patients receiving remdesivir and other standard care.

METHODS

In a randomised, double-blind, phase 3, placebo-controlled trial, adults with symptoms for up to 12 days and hospitalised for COVID-19 at 81 sites in the USA, Europe, Uganda, and Singapore were randomly assigned in a 1:1 ratio to receive intravenous tixagevimab 300 mg-cilgavimab 300 mg or placebo, in addition to remdesivir and other standard care. Patients were excluded if they had acute organ failure including receipt of invasive mechanical ventilation, extracorporeal membrane oxygenation, vasopressor therapy, mechanical circulatory support, or new renal replacement therapy. The study drug was prepared by an unmasked pharmacist; study participants, site study staff, investigators, and clinical providers were masked to study assignment. The primary outcome was time to sustained recovery up to day 90, defined as 14 consecutive days at home after hospital discharge, with co-primary analyses for the full cohort and for participants who were neutralising antibody-negative at baseline. Efficacy and safety analyses were done in the modified intention-to-treat population, defined as participants who received a complete or partial infusion of tixagevimab-cilgavimab or placebo. This study is registered with ClinicalTrials.gov, NCT04501978 and the participant follow-up is ongoing.

FINDINGS

From Feb 10 to Sept 30, 2021, 1455 patients were randomly assigned and 1417 in the primary modified intention-to-treat population were infused with tixagevimab-cilgavimab (n=710) or placebo (n=707). The estimated cumulative incidence of sustained recovery was 89% for tixagevimab-cilgavimab and 86% for placebo group participants at day 90 in the full cohort (recovery rate ratio [RRR] 1·08 [95% CI 0·97-1·20]; p=0·21). Results were similar in the seronegative subgroup (RRR 1·14 [0·97-1·34]; p=0·13). Mortality was lower in the tixagevimab-cilgavimab group (61 [9%]) versus placebo group (86 [12%]; hazard ratio [HR] 0·70 [95% CI 0·50-0·97]; p=0·032). The composite safety outcome occurred in 178 (25%) tixagevimab-cilgavimab and 212 (30%) placebo group participants (HR 0·83 [0·68-1·01]; p=0·059). Serious adverse events occurred in 34 (5%) participants in the tixagevimab-cilgavimab group and 38 (5%) in the placebo group.

INTERPRETATION

Among patients hospitalised with COVID-19 receiving remdesivir and other standard care, tixagevimab-cilgavimab did not improve the primary outcome of time to sustained recovery but was safe and mortality was lower.

FUNDING

US National Institutes of Health (NIH) and Operation Warp Speed.

A critical overview of current progress for COVID-19: development of vaccines, antiviral drugs, and therapeutic antibodies

The novel coronavirus disease (COVID-19) pandemic remains a global public health crisis, presenting a broad range of challenges. To help address some of the main problems, the scientific community has designed vaccines, diagnostic tools and therapeutics for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The rapid pace of technology development, especially with regard to vaccines, represents a stunning and historic scientific achievement. Nevertheless, many challenges remain to be overcome, such as improving vaccine and drug treatment efficacies for emergent mutant strains of SARS-CoV-2. Outbreaks of more infectious variants continue to diminish the utility of available vaccines and drugs. Thus, the effectiveness of vaccines and drugs against the most current variants is a primary consideration in the continual analyses of clinical data that supports updated regulatory decisions. The first two vaccines granted Emergency Use Authorizations (EUAs), BNT162b2 and mRNA-1273, still show more than 60% protection efficacy against the most widespread current SARS-CoV-2 variant, Omicron. This variant carries more than 30 mutations in the spike protein, which has largely abrogated the neutralizing effects of therapeutic antibodies. Fortunately, some neutralizing antibodies and antiviral COVID-19 drugs treatments have shown continued clinical benefits. In this review, we provide a framework for understanding the ongoing development efforts for different types of vaccines and therapeutics, including small molecule and antibody drugs. The ripple effects of newly emergent variants, including updates to vaccines and drug repurposing efforts, are summarized. In addition, we summarize the clinical trials supporting the development and distribution of vaccines, small molecule drugs, and therapeutic antibodies with broad-spectrum activity against SARS-CoV-2 strains.

Affinity capillary electrophoresis – mass spectrometry permits direct binding assessment of IgG and FcγRIIa in a glycoform-resolved manner

The impact of antibody glycoforms on FcγRIIa activation and immune responses is poorly understood. Yet, glycoform binding assessment remains one of the major analytical challenges requiring long enrichment or glycoengineering steps. Here, we developed and applied an affinity capillary electrophoresis-mass spectrometry approach to selectively assess the binding of different antibody glycoforms to the FcγIIa receptor without the need of glycoengineering. The approach required only low microgram amounts of antibody and receptor and enables assessing the binding of high and low-abundance glycoforms. The approach indicated clear differences in binging between doubly-, hemi-glycosylated and non-glycosylated antibodies as well as for mutated (Leu234Ala, Leu235Ala – Pro329-Gly (LALA-PG)) IgG1 antibodies silenced for Fcγ binding. The LALA-PG mutated antibody showed no binding to the FcγIIa receptor (excluding potential non-specific binding effects) while the non-glycosylated IgG1 showed a strongly reduced, but still minor binding. The highest binding affinity was for the antibody carrying two complex-type glycans. Man5 glycans resulted in decreased binding compared to complex-type glycans, with the lowest binding for the IgG containing two Man5. For complex-type glycans, galactosylation showed a subtle increase in binding to the FcγIIa receptor, and sialylation showed an increase in binding for lower sialylated species. Fucosylation did not influence binding to the FcγIIa receptor. Finally, the assay was evaluated for the two variants of the FcγRIIa receptor (allotypes H131 and R131) showing highly comparable glycoform selectivity. Overall, the proposed approach allows the direct comparison of binding affinities of different antibody species in mixtures promising a fast establishment of their structure-function relationships.

Finding the Right Heavy Chains for Immunostimulatory Antibodies

For twelve years, the oncology field has been revolutionized by antibodies targeting immune checkpoints. They must be considered as a heterogenous family of immunostimulatory antibodies displaying very different mechanisms of action, not only depending on the target or on the cells expressing it, but also on the IgG subclass or IgG variant that has been chosen. To dissect this complex landscape, the clinical experience has been confronted with a precise analysis of the heavy chain isotypes, referred as new Ge nomenclature. For antibodies targeting inhibitory receptors, anti-CTLA-4 antibodies (whose main effect is to kill regulatory T cells) will be distinguished from anti-PD-1 antibodies and other true antagonistic antibodies. Antibodies targeting ligands of inhibitory receptors (PD-L1, CD47) represent another different category, due to the antigen expression on tumors and a possible beneficial killing effect. The case of agonistic antibodies targeting lymphocyte activatory receptors, such as CD40 or 4-1BB, is still another “under construction” category because these products are less advanced in their clinical development. Altogether, it appears that choosing the right heavy chain is crucial to obtain the desired pharmacological effect in patients.

Resilience of S309 and AZD7442 monoclonal antibody treatments against infection by SARS-CoV-2 Omicron lineage strains

Omicron variant strains encode large numbers of changes in the spike protein compared to historical SARS-CoV-2 isolates. Although in vitro studies have suggested that several monoclonal antibody therapies lose neutralizing activity against Omicron variants, the effects in vivo remain largely unknown. Here, we report on the protective efficacy against three SARS-CoV-2 Omicron lineage strains (BA.1, BA.1.1, and BA.2) of two monoclonal antibody therapeutics (S309 [Vir Biotechnology] monotherapy and AZD7442 [AstraZeneca] combination), which correspond to ones used to treat or prevent SARS-CoV-2 infections in humans. Despite losses in neutralization potency in cell culture, S309 or AZD7442 treatments reduced BA.1, BA.1.1, and BA.2 lung infection in susceptible mice that express human ACE2 (K18-hACE2) in prophylactic and therapeutic settings. Correlation analyses between in vitro neutralizing activity and reductions in viral burden in K18-hACE2 or human FcγR transgenic mice suggest that S309 and AZD7442 have different mechanisms of protection against Omicron variants, with S309 utilizing Fc effector function interactions and AZD7442 acting principally by direct neutralization. Our data in mice demonstrate the resilience of S309 and AZD7442 mAbs against emerging SARS-CoV-2 variant strains and provide insight into the relationship between loss of antibody neutralization potency and retained protection in vivo.

Tixagevimab + Cilgavimab: First Approval

Tixagevimab 150 mg and cilgavimab 150 mg (EVUSHELD^TM 150 mg + 150 mg solution for injection; tixagevimab + cilgavimab) is an intramuscular (IM) long-acting monoclonal antibody combination developed by AstraZeneca for the prevention and treatment of COVID-19. In March 2022, tixagevimab + cilgavimab was approved in the UK for pre-exposure prophylaxis of COVID-19 in adults who are not currently infected with SARS-CoV-2 and who have not had a known recent exposure to an individual infected with SARS-CoV-2 and who are unlikely to mount an adequate immune response to COVID-19 vaccination or for whom COVID-19 vaccination is not recommended, and in the EU for the prevention of COVID-19 in adults and adolescents aged ≥ 12 years and weighing ≥40 kg. In December 2021, tixagevimab + cilgavimab was granted Emergency Use Authorization by the US FDA for the pre-exposure prophylaxis of COVID-19 in adults and paediatric individuals (≥ 12 years of age and weighing ≥ 40 kg). This article summarizes the milestones in the development of tixagevimab + cilgavimab leading to this first approval for pre-exposure prophylaxis of COVID-19 in individuals who are not currently infected with SARS-CoV-2.

Antibodies to combat viral infections: development strategies and progress

Monoclonal antibodies (mAbs) are appealing as potential therapeutics and prophylactics for viral infections owing to characteristics such as their high specificity and their ability to enhance immune responses. Furthermore, antibody engineering can be used to strengthen effector function and prolong mAb half-life, and advances in structural biology have enabled the selection and optimization of potent neutralizing mAbs through identification of vulnerable regions in viral proteins, which can also be relevant for vaccine design. The COVID-19 pandemic has stimulated extensive efforts to develop neutralizing mAbs against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with several mAbs now having received authorization for emergency use, providing not just an important component of strategies to combat COVID-19 but also a boost to efforts to harness mAbs in therapeutic and preventive settings for other infectious diseases. Here, we describe advances in antibody discovery and engineering that have led to the development of mAbs for use against infections caused by viruses including SARS-CoV-2, respiratory syncytial virus (RSV), Ebola virus (EBOV), human cytomegalovirus (HCMV) and influenza. We also discuss the rationale for moving from empirical to structure-guided strategies in vaccine development, based on identifying optimal candidate antigens and vulnerable regions within them that can be targeted by antibodies to result in a strong protective immune response.

Monoclonal antibodies (mAbs) are appealing as potential therapeutics and prophylactics for viral infections. This Review describes advances in antibody discovery and engineering that have led to the development of mAbs that target viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respiratory syncytial virus and Ebola virus, and also considers the implications for vaccine development.

Therapeutic efficacy of monoclonal antibodies and antivirals against SARS-CoV-2 Omicron BA.1 in Syrian hamsters

The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the major antigen stimulating the host's protective immune response. Here we assessed the efficacy of therapeutic monoclonal antibodies (mAbs) against Omicron variant (B.1.1.529) sublineage BA.1 variants in Syrian hamsters. Of the FDA-approved therapeutic mAbs tested (that is, REGN10987/REGN10933, COV2-2196/COV2-2130 and S309), only COV2-2196/COV2-2130 efficiently inhibited BA.1 replication in the lungs of hamsters, and this effect was diminished against a BA.1.1 variant possessing the S-R346K substitution. In addition, treatment of BA.1-infected hamsters with molnupiravir (a SARS-CoV-2 RNA-dependent RNA polymerase inhibitor) or S-217622 (a SARS-CoV-2 protease inhibitor) strongly reduced virus replication in the lungs. These findings suggest that the use of therapeutic mAbs in Omicron-infected patients should be carefully considered due to mutations that affect efficacy, and demonstrate that the antiviral compounds molnupiravir and S-217622 are effective against Omicron BA.1 variants.

Rapid Response of Refractory Systemic Lupus Erythematosus Skin Manifestations to Anifrolumab-A Case-Based Review of Clinical Trial Data Suggesting a Domain-Based Therapeutic Approach

Systemic lupus erythematosus (SLE) is a clinically heterogeneous autoimmune disease, and organ manifestations, such as lupus nephritis (LN) or skin disease, may be refractory to standard treatment. Therefore, new agents are required to allow for a more personalized therapeutic approach. Recently, several new therapies have been approved internationally, including voclosporine for LN and anifrolumab for moderately to severely active SLE. Here, we report a case of SLE with a predominant and refractory cutaneous manifestation despite combination treatment with glucocorticoids, hydroxychloroquine, mycophenolate mofetil, and belimumab, which had been present for more than 12 months. Belimumab was switched to anifrolumab, and the patient responded quickly after two infusions (eight weeks) with a reduction in the Cutaneous Lupus Assessment and Severity Index (CLASI) from 17 to 7. In addition, we review the available clinical trial data for anifrolumab with a focus on cutaneous outcomes. Based on phase II and III clinical trials investigating the intravenous administration, a consistent CLASI improvement was observed at 12 weeks. Interestingly, in a phase II trial of subcutaneous anifrolumab application, CLASI response was not different from placebo at 12 weeks but numerically different at 24 and 52 weeks, respectively. Thus, anifrolumab emerges as an attractive new therapeutic option suggesting a possible domain-based approach.

Intramuscular AZD7442 (Tixagevimab-Cilgavimab) for Prevention of Covid-19

BACKGROUND

The monoclonal-antibody combination AZD7442 is composed of tixagevimab and cilgavimab, two neutralizing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that have an extended half-life and have been shown to have prophylactic and therapeutic effects in animal models. Pharmacokinetic data in humans indicate that AZD7442 has an extended half-life of approximately 90 days.

METHODS

In an ongoing phase 3 trial, we enrolled adults (≥18 years of age) who had an increased risk of an inadequate response to vaccination against coronavirus disease 2019 (Covid-19), an increased risk of exposure to SARS-CoV-2, or both. Participants were randomly assigned in a 2:1 ratio to receive a single dose (two consecutive intramuscular injections, one containing tixagevimab and the other containing cilgavimab) of either 300 mg of AZD7442 or saline placebo, and they were followed for up to 183 days in the primary analysis. The primary safety end point was the incidence of adverse events after a single dose of AZD7442. The primary efficacy end point was symptomatic Covid-19 (SARS-CoV-2 infection confirmed by means of reverse-transcriptase-polymerase-chain-reaction assay) occurring after administration of AZD7442 or placebo and on or before day 183.

RESULTS

A total of 5197 participants underwent randomization and received one dose of AZD7442 or placebo (3460 in the AZD7442 group and 1737 in the placebo group). The primary analysis was conducted after 30% of the participants had become aware of their randomized assignment. In total, 1221 of 3461 participants (35.3%) in the AZD7442 group and 593 of 1736 participants (34.2%) in the placebo group reported having at least one adverse event, most of which were mild or moderate in severity. Symptomatic Covid-19 occurred in 8 of 3441 participants (0.2%) in the AZD7442 group and in 17 of 1731 participants (1.0%) in the placebo group (relative risk reduction, 76.7%; 95% confidence interval [CI], 46.0 to 90.0; P<0.001); extended follow-up at a median of 6 months showed a relative risk reduction of 82.8% (95% CI, 65.8 to 91.4). Five cases of severe or critical Covid-19 and two Covid-19-related deaths occurred, all in the placebo group.

CONCLUSIONS

A single dose of AZD7442 had efficacy for the prevention of Covid-19, without evident safety concerns. (Funded by AstraZeneca and the U.S. government; PROVENT ClinicalTrials.gov number, NCT04625725.).

Passive Immunotherapy Against SARS-CoV-2: From Plasma-Based Therapy to Single Potent Antibodies in the Race to Stay Ahead of the Variants

The COVID-19 pandemic is now approaching 2 years old, with more than 440 million people infected and nearly six million dead worldwide, making it the most significant pandemic since the 1918 influenza pandemic. The severity and significance of SARS-CoV-2 was recognized immediately upon discovery, leading to innumerable companies and institutes designing and generating vaccines and therapeutic antibodies literally as soon as recombinant SARS-CoV-2 spike protein sequence was available. Within months of the pandemic start, several antibodies had been generated, tested, and moved into clinical trials, including Eli Lilly's bamlanivimab and etesevimab, Regeneron's mixture of imdevimab and casirivimab, Vir's sotrovimab, Celltrion's regdanvimab, and Lilly's bebtelovimab. These antibodies all have now received at least Emergency Use Authorizations (EUAs) and some have received full approval in select countries. To date, more than three dozen antibodies or antibody combinations have been forwarded into clinical trials. These antibodies to SARS-CoV-2 all target the receptor-binding domain (RBD), with some blocking the ability of the RBD to bind human ACE2, while others bind core regions of the RBD to modulate spike stability or ability to fuse to host cell membranes. While these antibodies were being discovered and developed, new variants of SARS-CoV-2 have cropped up in real time, altering the antibody landscape on a moving basis. Over the past year, the search has widened to find antibodies capable of neutralizing the wide array of variants that have arisen, including Alpha, Beta, Gamma, Delta, and Omicron. The recent rise and dominance of the Omicron family of variants, including the rather disparate BA.1 and BA.2 variants, demonstrate the need to continue to find new approaches to neutralize the rapidly evolving SARS-CoV-2 virus. This review highlights both convalescent plasma- and polyclonal antibody-based approaches as well as the top approximately 50 antibodies to SARS-CoV-2, their epitopes, their ability to bind to SARS-CoV-2 variants, and how they are delivered. New approaches to antibody constructs, including single domain antibodies, bispecific antibodies, IgA- and IgM-based antibodies, and modified ACE2-Fc fusion proteins, are also described. Finally, antibodies being developed for palliative care of COVID-19 disease, including the ramifications of cytokine release syndrome (CRS) and acute respiratory distress syndrome (ARDS), are described.

Improving Antibody Therapeutics by Manipulating the Fc Domain: Immunological and Structural Considerations

Interactions between the crystallizable fragment (Fc) domain of antibodies and a plethora of cellular Fc receptors (FcRs) or soluble proteins form a critical link between humoral and innate immunity. In particular, the immunoglobulin G Fc domain is critical for the clearance of target cells by processes that include (a) cytotoxicity, phagocytosis, or complement lysis; (b) modulation of inflammation; (c) antigen presentation; (d) antibody-mediated receptor clustering; and (e) cytokine release. More than 30 Fc-engineered antibodies aimed primarily at tailoring these effects for optimal therapeutic outcomes are in clinical evaluation or have already been approved. Nonetheless, our understanding of how FcR engagement impacts various immune cell phenotypes is still largely incomplete. Recent insights into FcR biology coupled with advances in Fc:FcR structural analysis, Fc engineering, and mouse models that recapitulate human biology are helping to fill in existing knowledge gaps. These advances will provide a blueprint on how to fine-tune the Fc domain to achieve optimal therapeutic efficacy. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The SARS-CoV-2 monoclonal antibody combination, AZD7442, is protective in nonhuman primates and has an extended half-life in humans

Despite the success of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines, there remains a need for more prevention and treatment options for individuals remaining at risk of coronavirus disease 2019 (COVID-19). Monoclonal antibodies (mAbs) against the viral spike protein have potential to both prevent and treat COVID-19 and reduce the risk of severe disease and death. Here, we describe AZD7442, a combination of two mAbs, AZD8895 (tixagevimab) and AZD1061 (cilgavimab), that simultaneously bind to distinct, nonoverlapping epitopes on the spike protein receptor binding domain to neutralize SARS-CoV-2. Initially isolated from individuals with prior SARS-CoV-2 infection, the two mAbs were designed to extend their half-lives and reduce effector functions. The AZD7442 mAbs individually prevent the spike protein from binding to angiotensin-converting enzyme 2 receptor, blocking virus cell entry, and neutralize all tested SARS-CoV-2 variants of concern. In a nonhuman primate model of SARS-CoV-2 infection, prophylactic AZD7442 administration prevented infection, whereas therapeutic administration accelerated virus clearance from the lung. In an ongoing phase 1 study in healthy participants (NCT04507256), a 300-mg intramuscular injection of AZD7442 provided SARS-CoV-2 serum geometric mean neutralizing titers greater than 10-fold above those of convalescent serum for at least 3 months, which remained threefold above those of convalescent serum at 9 months after AZD7442 administration. About 1 to 2% of serum AZD7442 was detected in nasal mucosa, a site of SARS-CoV-2 infection. Extrapolation of the time course of serum AZD7442 concentration suggests AZD7442 may provide up to 12 months of protection and benefit individuals at high-risk of COVID-19.

Monoclonal antibodies for COVID-19 therapy and SARS-CoV-2 detection

The coronavirus disease 2019 (COVID-19) pandemic is an exceptional public health crisis that demands the timely creation of new therapeutics and viral detection. Owing to their high specificity and reliability, monoclonal antibodies (mAbs) have emerged as powerful tools to treat and detect numerous diseases. Hence, many researchers have begun to urgently develop Ab-based kits for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Ab drugs for use as COVID-19 therapeutic agents. The detailed structure of the SARS-CoV-2 spike protein is known, and since this protein is key for viral infection, its receptor-binding domain (RBD) has become a major target for therapeutic Ab development. Because SARS-CoV-2 is an RNA virus with a high mutation rate, especially under the selective pressure of aggressively deployed prophylactic vaccines and neutralizing Abs, the use of Ab cocktails is expected to be an important strategy for effective COVID-19 treatment. Moreover, SARS-CoV-2 infection may stimulate an overactive immune response, resulting in a cytokine storm that drives severe disease progression. Abs to combat cytokine storms have also been under intense development as treatments for COVID-19. In addition to their use as drugs, Abs are currently being utilized in SARS-CoV-2 detection tests, including antigen and immunoglobulin tests. Such Ab-based detection tests are crucial surveillance tools that can be used to prevent the spread of COVID-19. Herein, we highlight some key points regarding mAb-based detection tests and treatments for the COVID-19 pandemic.

Full-length recombinant antibodies from Escherichia coli: production, characterization, effector function (Fc) engineering, and clinical evaluation

Although several antibody fragments and antibody fragment-fusion proteins produced in Escherichia coli (E. coli) are approved as therapeutics for various human diseases, a full-length monoclonal or a bispecific antibody produced in E. coli has not yet been approved. The past decade witnessed substantial progress in expression of full-length antibodies in the E. coli cytoplasm and periplasm, as well as in cell-free expression systems. The equivalency of E. coli-produced aglycosylated antibodies and their mammalian cell-produced counterparts, with respect to biochemical and biophysical properties, including antigen binding, in vitro and in vivo serum stability, pharmacokinetics, and in vivo serum half-life, has been demonstrated. Extensive engineering of the Fc domain of aglycosylated antibodies enables recruitment of various effector functions, despite the lack of N-linked glycans. This review summarizes recent research, preclinical advancements, and clinical development of E. coli-produced aglycosylated therapeutic antibodies as monoclonal, bispecific, and antibody-drug conjugates for use in autoimmune, oncology, and immuno-oncology areas.Abbreviations: ADA Anti-drug antibody; ADCC Antibody-dependent cellular cytotoxicity; ADCP Antibody-dependent cellular phagocytosis; ADC Antibody-drug conjugate; aFc Aglycosylated Fc; AMD Age-related macular degeneration aTTP Acquired thrombotic thrombocytopenic purpura; BCMA B-cell maturation antigen; BLA Biologics license application; BsAb Bispecific antibody; C1q Complement protein C1q; CDC Complement-dependent cytotoxicity; CDCC Complement-dependent cellular cytotoxicity; CDCP Complement-dependent cellular phagocytosis; CEX Cation exchange chromatography; CFPS Cell-free protein expression; CHO Chinese Hamster Ovary; CH1-3 Constant heavy chain 1-3; CL Constant light chain; DLBCL Diffuse large B-cell lymphoma; DAR Drug antibody ratio; DC Dendritic cell; dsFv Disulfide-stabilized Fv; EU European Union; EGFR Epidermal growth factor receptor; E. coli Escherichia coli; EpCAM Epithelial cell adhesion molecule; Fab Fragment antigen binding; FACS Fluorescence activated cell sorting; Fc Fragment crystallizable; FcRn Neonatal Fc receptor; FcɣRs Fc gamma receptors; FDA Food and Drug Administration; FL-IgG Full-length immunoglobulin; Fv Fragment variable; FolRαa Folate receptor alpha; gFc Glycosylated Fc; GM-CSF Granulocyte macrophage-colony stimulating factor; GPx7 Human peroxidase 7; HCL Hairy cell leukemia; HIV Human immunodeficiency virusl; HER2 Human epidermal growth factor receptor 2; HGF Hepatocyte growth factor; HIC Hydrophobic interaction chromatography; HLA Human leukocyte antigen; IBs Inclusion bodies; IgG1-4 Immunoglobulin 1-4; IP Intraperitoneal; ITC Isothermal titration calorimetry; ITP Immune thrombocytopenia; IV Intravenous; kDa Kilodalton; KiH Knob-into-Hole; mAb Monoclonal antibody; MAC Membrane-attack complex; mCRC Metastatic colorectal cancer; MM Multipl myeloma; MOA Mechanism of action; MS Mass spectrometry; MUC1 Mucin 1; MG Myasthenia gravis; NB Nanobody; NK Natural killer; nsAA Nonstandard amino acid; NSCLC Non-small cell lung cancer; P. aeruginosa Pseudomonas aeruginosa; PD-1 Programmed cell death 1; PD-L1 Programmed cell death-ligand 1; PDI Protein disulfide isomerase; PECS Periplasmic expression cytometric screening; PK Pharmacokinetics; P. pastoris Pichia pastoris; PTM Post-translational modification; Rg Radius of gyration; RA Rheumatoid arthritis; RT-PCR Reverse transcription polymerase chain reaction; SAXS Small angle X-ray scattering; scF Single chain Fv; SCLC Small cell lung cancer; SDS-PAGE Sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SEC Size exclusion chromatography; SEED Strand-exchange engineered domain; sRNA Small regulatory RNA; SRP Signal recognition particle; T1/2 Half-life; Tagg Aggregation temperature; TCR T cell receptor; TDB T cell-dependent bispecific; TF Tissue factor; TIR Translation initiation region; Tm Melting temperature; TNBC Triple-negative breast cancer; TNF Tumor necrosis factor; TPO Thrombopoietin; VEGF Vascular endothelial growth factor; vH Variable heavy chain; vL Variable light chain; vWF von Willebrand factor; WT Wild type.

Fc-engineered antibodies with immune effector functions completely abolished

Elimination of the binding of immunoglobulin Fc to Fc gamma receptors (FcγR) is highly desirable for the avoidance of unwanted inflammatory responses to therapeutic antibodies and fusion proteins. Many different approaches have been described in the literature but none of them completely eliminates binding to all of the Fcγ receptors. Here we describe a set of novel variants having specific amino acid substitutions in the Fc region at L234 and L235 combined with the substitution G236R. They show no detectable binding to Fcγ receptors or to C1q, are inactive in functional cell-based assays and do not elicit inflammatory cytokine responses. Meanwhile, binding to FcRn, manufacturability, stability and potential for immunogenicity are unaffected. These variants have the potential to improve the safety and efficacy of therapeutic antibodies and Fc fusion proteins.

Safety and efficacy of durvalumab with R-CHOP or R2-CHOP in untreated, high-risk DLBCL: a phase 2, open-label trial

Patients with high-risk diffuse large B-cell lymphoma (DLBCL) have poor outcomes following first-line cyclophosphamide, doxorubicin, vincristine, prednisone, and rituximab (R-CHOP). Evidence shows chemotherapy and immune checkpoint blockade can increase antitumor efficacy. This study investigated durvalumab, a programmed death-ligand 1 inhibitor, combined with R-CHOP or lenalidomide + R-CHOP (R²-CHOP) in newly diagnosed high-risk DLBCL. Patients received durvalumab 1125 mg every 21 days for 2-8 cycles + R-CHOP (non-activated B-cell [ABC] subtype) or R²-CHOP (ABC), then durvalumab consolidation (1500 mg every 28 days). Of 46 patients, 43 received R-CHOP and three R²-CHOP. All patients had the high-risk disease; 14 (30.4%) and eight (17.4%) had double- or triple-hit DLBCL, respectively. Following induction, 20/37 (54.1%) patients receiving durvalumab + R-CHOP achieved complete response (CR), and seven (18.9%) partial response (PR); 25 (67.6% [95% CI 50.2-82.0]) continued to consolidation and were progression-free at 12 months. Among efficacy-evaluable patients with double- or triple-hit DLBCL (n = 12), five achieved CR and five PR. Adverse events were generally consistent with R-CHOP. Correlative analyses did not identify conclusive biomarkers of response. Durvalumab + R-CHOP is feasible in DLBCL with no new safety signals, but the combination provided no greater benefit than R-CHOP.

Identification of a CE-SDS shoulder peak as disulfide-linked fragments from common CH2 cleavages in IgGs and IgG-like bispecific antibodies

Fragmentation is a well-characterized degradation pathway of therapeutic antibodies and is usually monitored by capillary electrophoresis–sodium dodecyl sulfate (CE-SDS). Although fragments due to cleavage in C_H2 domains linked by intrachain disulfide bonds are common and can be detected by reduced reversed-phase – liquid chromatography mass spectrometry (RP-LCMS) and reduced CE-SDS methods, their separation in nonreduced CE-SDS (nrCE-SDS) has not been reported but speculated as comigrating with intact IgG. A shoulder peak in nrCE-SDS was observed in the stability samples of an IgG-like bispecific antibody and was determined to be mainly caused by fragments from clipping at the C-terminus of leucine (L)306 or L309 (EU numbering) in the C_H2 domain of both heavy chains (HCs) and, to a lesser degree, at the C-terminus of L182 in the C_H1 domain of the knob HC. Subunit LCMS analysis verified that the crystallizable fragment contained variants with one or multiple mass additions of ~18 Da due to clipping. Further investigation revealed that C_H2 clippings at L306 and L309 were largely due to proteolytic activity, and cleavages were present at various levels in all in-house IgG1 and IgG4 molecules studied. Our study shows that C_H2 domain cleavages, with complementary fragments still linked by intrachain disulfide, can be electrophoretically resolved as a front shoulder of the main peak in nrCE-SDS. Given the high occurrence of C_H2 cleavages in antibodies, these findings will have broad applicability and could help manufacturers of therapeutic antibodies in process improvement, product characterization, investigations, formulation stability, and stability comparability studies.

Depleting plasmacytoid dendritic cells reduces local type I interferon responses and disease activity in patients with cutaneous lupus

Plasmacytoid dendritic cells (pDCs) not only are specialized in their capacity to secrete large amounts of type I interferon (IFN) but also serve to enable both innate and adaptive immune responses through expression of additional proinflammatory cytokines, chemokines, and costimulatory molecules. Persistent activation of pDCs has been demonstrated in a number of autoimmune diseases. To evaluate the potential benefit of depleting pDCs in autoimmunity, a monoclonal antibody targeting the pDC-specific marker immunoglobulin-like transcript 7 was generated. This antibody, known as VIB7734, which was engineered for enhanced effector function, mediated rapid and potent depletion of pDCs through antibody-dependent cellular cytotoxicity. In cynomolgus monkeys, treatment with VIB7734 reduced pDCs in blood below the lower limit of normal by day 1 after the first dose. In two phase 1 studies in patients with autoimmune diseases, VIB7734 demonstrated an acceptable safety profile, comparable to that of placebo. In individuals with cutaneous lupus, VIB7734 profoundly reduced both circulating and tissue-resident pDCs, with a 97.6% median reduction in skin pDCs at study day 85 in VIB7734-treated participants. Reductions in pDCs in the skin correlated with a decrease in local type I IFN activity as well as improvements in clinical disease activity. Biomarker analysis suggests that responsiveness to pDC depletion therapy may be greater among individuals with high baseline type I IFN activity, supporting a central role for pDCs in type I IFN production in autoimmunity and further development of VIB7734 in IFN-associated diseases.

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.

Engineered Fc-glycosylation switch to eliminate antibody effector function

Antibodies mediate effector functions through Fcγ receptor (FcγR) interactions and complement activation, causing cytokine release, degranulation, phagocytosis, and cell death. They are often undesired for development of therapeutic antibodies where only antigen binding or neutralization would be ideal. Effector elimination has been successful with extensive mutagenesis, but these approaches can potentially lead to manufacturability and immunogenicity issues. By switching the native glycosylation site from position 297 to 298, we created alternative antibody glycosylation variants in the receptor interaction interface as a novel strategy to eliminate the effector functions. The engineered glycosylation site at Asn298 was confirmed by SDS-PAGE, mass spectrometry, and X-ray crystallography (PDB code 6X3I). The lead NNAS mutant (S298N/T299A/Y300S) shows no detectable binding to mouse or human FcγRs by surface plasmon resonance analyses. The effector functions of the mutant are completely eliminated when measured in antibody-dependent cell-meditated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) assays. In vivo, the NNAS mutant made on an antibody against a human lymphocyte antigen does not deplete T cells or B cells in transgenic mice, in contrast to wild-type antibody. Structural study confirms the successful glycosylation switch to the engineered Asn298 site. The engineered glycosylation would clash with approaching FcγRs based on reported Fc-FcγR co-crystal structures. In addition, the NNAS mutants of multiple antibodies retain binding to antigens and neonatal Fc receptor, exhibit comparable purification yields and thermal stability, and display normal circulation half-life in mice and non-human primate. Our work provides a novel approach for generating therapeutic antibodies devoid of any ADCC and CDC activities with potentially lower immunogenicity.

Cancer immunotherapy by NC410, a LAIR-2 Fc protein blocking human LAIR-collagen interaction

Collagens are a primary component of the extracellular matrix and are functional ligands for the inhibitory immune receptor leukocyte-associated immunoglobulin-like receptor (LAIR)-1. LAIR-2 is a secreted protein that can act as a decoy receptor by binding collagen with higher affinity than LAIR-1. We propose that collagens promote immune evasion by interacting with LAIR-1 expressed on immune cells, and that LAIR-2 releases LAIR-1-mediated immune suppression. Analysis of public human datasets shows that collagens, LAIR-1 and LAIR-2 have unique and overlapping associations with survival in certain tumors. We designed a dimeric LAIR-2 with a functional IgG1 Fc tail, NC410, and showed that NC410 increases human T cell expansion and effector function in vivo in a mouse xenogeneic-graft versus-host disease model. In humanized mouse tumor models, NC410 reduces tumor growth that is dependent on T cells. Immunohistochemical analysis of human tumors shows that NC410 binds to collagen-rich areas where LAIR-1⁺ immune cells are localized. Our findings show that NC410 might be a novel strategy for cancer immunotherapy for immune-excluded tumors.

Tackling COVID-19 with neutralizing monoclonal antibodies

Monoclonal antibodies (mAbs) have revolutionized the treatment of several human diseases, including cancer and autoimmunity and inflammatory conditions, and represent a new frontier for the treatment of infectious diseases. In the last 20 years, innovative methods have allowed the rapid isolation of mAbs from convalescent subjects, humanized mice, or libraries assembled in vitro and have proven that mAbs can be effective countermeasures against emerging pathogens. During the past year, an unprecedentedly large number of mAbs have been developed to fight coronavirus disease 2019 (COVID-19). Lessons learned from this pandemic will pave the way for the development of more mAb-based therapeutics for other infectious diseases. Here, we provide an overview of SARS-CoV-2-neutralizing mAbs, including their origin, specificity, structure, antiviral and immunological mechanisms of action, and resistance to circulating variants, as well as a snapshot of the clinical trials of approved or late-stage mAb therapeutics.

Optimization of therapeutic antibodies

In this review, we have summarized the current landscape of therapeutic antibody optimization for successful development. By engineering antibodies with display technology, computer-aided design and site mutagenesis, various properties of the therapeutic antibody candidates can be improved with the purpose of enhancing their safety, efficacy and developability. These properties include antigen binding affinity and specificity, biological efficacy, pharmacokinetics and pharmacodynamics, immunogenicity and physicochemical developability features. A best-in-class strategy may require the optimization of all these properties to generate a good therapeutic antibody.

Regulation of antibody-mediated complement-dependent cytotoxicity by modulating the intrinsic affinity and binding valency of IgG for target antigen

Complement-dependent cytotoxicity (CDC) is a potent effector mechanism, engaging both innate and adaptive immunity. Although strategies to improve the CDC activity of antibody therapeutics have primarily focused on enhancing the interaction between the antibody crystallizable fragment (Fc) and the first subcomponent of the C1 complement complex (C1q), the relative importance of intrinsic affinity and binding valency of an antibody to the target antigen is poorly understood. Here we show that antibody binding affinity to a cell surface target antigen evidently affects the extent and efficacy of antibody-mediated complement activation. We further report the fundamental role of antibody binding valency in the capacity to recruit C1q and regulate CDC. More specifically, an array of affinity-modulated variants and functionally monovalent bispecific derivatives of high-affinity anti-epidermal growth factor receptor (EGFR) and anti-human epidermal growth factor receptor 2 (HER2) therapeutic immunoglobulin Gs (IgGs), previously reported to be deficient in mediating complement activation, were tested for their ability to bind C1q by biolayer interferometry using antigen-loaded biosensors and to exert CDC against a panel of EGFR and HER2 tumor cells of various histological origins. Significantly, affinity-reduced variants or monovalent derivatives, but not their high-affinity bivalent IgG counterparts, induced near-complete cell cytotoxicity in tumor cell lines that had formerly been shown to be resistant to complement-mediated attack. Our findings suggest that monovalent target engagement may contribute to an optimal geometrical positioning of the antibody Fc to engage C1q and deploy the complement pathway.

Design and Efficacy of a Monovalent Bispecific PD-1/CTLA4 Antibody That Enhances CTLA4 Blockade on PD-1+ Activated T Cells

The clinical benefit of PD-1 blockade can be improved by combination with CTLA4 inhibition but is commensurate with significant immune-related adverse events suboptimally limiting the doses of anti-CTLA4 mAb that can be used. MEDI5752 is a monovalent bispecific antibody designed to suppress the PD-1 pathway and provide modulated CTLA4 inhibition favoring enhanced blockade on PD-1⁺ activated T cells. We show that MEDI5752 preferentially saturates CTLA4 on PD-1⁺ T cells versus PD-1^- T cells, reducing the dose required to elicit IL2 secretion. Unlike conventional PD-1/CTLA4 mAbs, MEDI5752 leads to the rapid internalization and degradation of PD-1. Moreover, we show that MEDI5752 preferentially localizes and accumulates in tumors providing enhanced activity when compared with a combination of mAbs targeting PD-1 and CTLA4 in vivo. Following treatment with MEDI5752, robust partial responses were observed in two patients with advanced solid tumors. MEDI5752 represents a novel immunotherapy engineered to preferentially inhibit CTLA4 on PD-1⁺ T cells. SIGNIFICANCE: The unique characteristics of MEDI5752 represent a novel immunotherapy engineered to direct CTLA4 inhibition to PD-1⁺ T cells with the potential for differentiated activity when compared with current conventional mAb combination strategies targeting PD-1 and CTLA4. This molecule therefore represents a step forward in the rational design of cancer immunotherapy.See related commentary by Burton and Tawbi, p. 1008.This article is highlighted in the In This Issue feature, p. 995.

Activity of murine surrogate antibodies for durvalumab and tremelimumab lacking effector function and the ability to deplete regulatory T cells in mouse models of cancer

Preclinical studies of PD-L1 and CTLA-4 blockade have relied heavily on mouse syngeneic tumor models with intact immune systems, which facilitate dissection of immunosuppressive mechanisms in the tumor microenvironment. Commercially developed monoclonal antibodies (mAbs) targeting human PD-L1, PD-1, and CTLA-4 may not demonstrate cross-reactive binding to their mouse orthologs, and surrogate anti-mouse antibodies are often used in their place to inhibit these immune checkpoints. In each case, multiple choices exist for surrogate antibodies, which differ with respect to species of origin, affinity, and effector function. To develop relevant murine surrogate antibodies for the anti-human PD-L1 mAb durvalumab and the anti-human CTLA-4 mAb tremelimumab, rat/mouse chimeric or fully murine mAbs engineered for reduced effector function were developed and compared with durvalumab and tremelimumab. Characterization included determination of target affinity, in vivo effector function, pharmacokinetic profile, and anti-tumor efficacy in mouse syngeneic tumor models. Results showed that anti-PD-L1 and anti-CTLA-4 murine surrogates with pharmacologic properties similar to those of durvalumab and tremelimumab demonstrated anti-tumor activity in a subset of commonly used mouse syngeneic tumor models. This activity was not entirely dependent on antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis effector function, or regulatory T-cell depletion, as antibodies engineered to lack these features showed activity in models historically sensitive to checkpoint inhibition, albeit at a significantly lower level than antibodies with intact effector function.

Fc-Engineering for Modulated Effector Functions-Improving Antibodies for Cancer Treatment

The majority of monoclonal antibody (mAb) therapeutics possess the ability to engage innate immune effectors through interactions mediated by their fragment crystallizable (Fc) domain. By delivering Fc-Fc gamma receptor (FcγR) and Fc-C1q interactions, mAb are able to link exquisite specificity to powerful cellular and complement-mediated effector functions. Fc interactions can also facilitate enhanced target clustering to evoke potent receptor signaling. These observations have driven decades-long research to delineate the properties within the Fc that elicit these various activities, identifying key amino acid residues and elucidating the important role of glycosylation. They have also fostered a growing interest in Fc-engineering whereby this knowledge is exploited to modulate Fc effector function to suit specific mechanisms of action and therapeutic purposes. In this review, we document the insight that has been generated through the study of the Fc domain; revealing the underpinning structure-function relationships and how the Fc has been engineered to produce an increasing number of antibodies that are appearing in the clinic with augmented abilities to treat cancer.