Increasing stability of antibody via antibody engineering: stability engineering on an anti-hVEGF.

Antibody stability is very important for expression, activity, specificity, and storage. This knowledge of antibody structure has made it possible for a computer-aided molecule design to be used to optimize and increase antibody stability. Many computational methods have been built based on knowledge or structure, however, a good integrated engineering system has yet to be developed that combines these methods. In the current study, we designed an integrated computer-aided engineering protocol, which included several successful methods. Mutants were designed considering factors that affected stability and multiwall filter screening was used to improve the design accuracy. Using this protocol, the thermo-stability of an anti-hVEGF antibody was significantly improved. Nearly 40% of the single-point mutants proved to be more stable than the parent antibody and most of the mutations could be stacked effectively. The T50 also improved about 7°C by combinational mutation of seven sites in the light chain and three sites in the heavy chain. Data indicate that the protocol is an effective method for optimization of antibody structure, especially for improving thermo-stability. This protocol could also be used to enhance the stability of other antibodies.

Establishment of a novel cell-based assay for screening small molecule antagonists of human interleukin-6 receptor.

AIM: Blockade of interleukin-6 (IL-6) or its receptor (IL-6R) is effective in preventing the progression of autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. In the present study, we established a novel cell-based assay for identifying small molecule IL-6R antagonists. METHODS: HEK293A cells were transfected with recombinant plasmids pTaglite-SNAP-IL6R and pABhFc-IL6 to obtain membrane-bound IL-6R and recombinant human IL-6 coupled with human Fc fragment (rhIL-6), respectively. A novel screening assay based on the interaction between IL-6R and rhIL-6 was established, optimized and validated. The stability of the assay was also assessed by calculating the Z'-factor. RESULTS: RhIL-6 dose-dependently bound to IL-6R expressed at HEK293A cell surface. The IC50 value of the known antagonist ab47215 was 0.38±0.08 µg/mL, which was consistent with that obtained using the traditional method (0.36±0.14 µg/mL). The value of Z'-factor was 0.68, suggesting that the novel assay was stable for high throughput screening. A total of 474 compounds were screened using the novel screening assay, and 3 compounds exhibited antagonistic activities (IC50=8.73±0.28, 32.32±9.08, 57.83±4.24 µg/mL). Furthermore, the active compounds dose-dependently inhibited IL-6-induced proliferation of 7TD1 cells, and reduced IL-6-induced STAT3 phosphorylation in U937 cells. CONCLUSION: A novel cell-based screening assay for identifying small molecule IL-6R antagonists was established, which simplifies the procedures in traditional cellular ELISA screening and profiling and reduces the costs.

Characterization of MW06, a human monoclonal antibody with cross-neutralization activity against both SARS-CoV-2 and SARS-CoV.

The global pandemic of COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in widespread social and economic disruption. Effective interventions are urgently needed for the prevention and treatment of COVID-19. Neutralizing monoclonal antibodies (mAbs) have demonstrated their prophylactic and therapeutic efficacy against SARS-CoV-2, and several have been granted authorization for emergency use. Here, we discover and characterize a fully human cross-reactive mAb, MW06, which binds to both SARS-CoV-2 and SARS-CoV spike receptor-binding domain (RBD) and disrupts their interaction with angiotensin-converting enzyme 2 (ACE2) receptors. Potential neutralization activity of MW06 was observed against both SARS-CoV-2 and SARS-CoV in different assays. The complex structure determination and epitope alignment of SARS-CoV-2 RBD/MW06 revealed that the epitope recognized by MW06 is highly conserved among SARS-related coronavirus strains, indicating the potential broad neutralization activity of MW06. In in vitro assays, no antibody-dependent enhancement (ADE) of SARS-CoV-2 infection was observed for MW06. In addition, MW06 recognizes a different epitope from MW05, which shows high neutralization activity and has been in a Phase 2 clinical trial, supporting the development of the cocktail of MW05 and MW06 to prevent against future escaping variants. MW06 alone and the cocktail show good effects in preventing escape mutations, including a series of variants of concern, B.1.1.7, P.1, B.1.351, and B.1.617.1. These findings suggest that MW06 recognizes a conserved epitope on SARS-CoV-2, which provides insights for the development of a universal antibody-based therapy against SARS-related coronavirus and emerging variant strains, and may be an effective anti-SARS-CoV-2 agent.

A Novel Anti-EGFR mAb Ame55 with Lower Toxicity and Better Efficacy than Cetuximab When Combined with Irinotecan.

To improve efficacy and minimize toxicity of EGFR inhibition treatment, we developed Ame55, a novel anti-EGFR IgG1 with lower affinity to EGFR than cetuximab (C225) from a human phage library. Ame55 had lower bioactivity than cetuximab in vitro but similar antitumor efficacy as cetuximab in vivo. Moreover, Ame55 was more efficacious than cetuximab in a Lovo cell xenograft tumor model when combined with irinotecan (CPT-11). Ame55 concentrates in the mouse xenograft tumor and has less toxicity than cetuximab in cynomolgus monkeys in an overdose study.

A novel fully human anti-CD47 antibody as a potential therapy for human neoplasms with good safety.

Strategies for targeting CD47 are becoming a hot spot of cancer immunotherapy. However the ubiquitous expression of CD47, especially on the RBC, makes the targeted therapy facing safety risk issues. So, how to balance the safety and efficacy during CD47 inhibition is currently a major question. We had reported an anti-CD47 antibody ZF1 with potent anti-tumor effect. In this study, we further developed and assessed a novel fully human anti-CD47 antibody, AMMS4-G4, derived from ZF1 using affinity maturation. AMMS4-G4 exhibited equivalent anticancer effects with Hu5F9-G4, a humanized anti-CD47 antibody in clinical trial, on the potential of inducing significant phagocytosis of tumor cells in vitro and prolonging the survival of leukemia xenografted mice. Additionally, AMMS4-G4 significantly inhibited the growth of grafted solid tumors by enhancing macrophage infiltration and modestly enhanced the anti-tumor activity of opsonizing antibody and antiangiogenic therapy. In cynomolgus monkeys, AMMS4-G4 was safely administered, was well tolerated at doses of 30 and 60 mg/kg, and did not produce serious adverse events, except for the reversible anemia, which was observed after 3 days and started to recover from 9 days later. Remarkably, it was proved by in vitro assay that Hu5F9-G4 induced RBC hemagglutination which wasn't observed in AMMS4-G4. On the whole, AMMS4-G4 was demonstrated to be a promising candidate with great potential and safe profile for cancer immunotherapy.

A fully human anti-CD47 blocking antibody with therapeutic potential for cancer.

CD47/SIRPα interaction serves as an immune checkpoint for macrophage-mediated phagocytosis. Mouse anti-CD47 blocking antibodies had demonstrated potent efficacy in the treatment of both leukemic and solid tumors in preclinical experimentations, and therefore had moved forward rapidly into clinical trials. However, a fully human blocking antibody, which meets clinical purpose better, has not been reported for CD47 up to date. In this study, we reported the isolation of a fully human anti-CD47 blocking antibody, ZF1, from a phage display library. ZF1 displayed high specificity and affinity for CD47 protein, which were comparable to those for humanized anti-CD47 blocking antibody B6H12. Importantly, ZF1 treatment could induce robust, or even stronger than B6H12, phagocytosis of leukemic cancer cells by macrophage in vitro, and protect BALB/c nude mice from cancer killing by engrafted leukemic cells (CCRF and U937) to a similar extent as B6H12 did. Thus, these data provide primary early pre-clinical support for the development of ZF1 as a fully human blocking antibody to treat human leukemia by targeting CD47 molecule.

A fully human monoclonal antibody with novel binding epitope and excellent neutralizing activity to multiple human IFN-α subtypes: A candidate therapy for systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a chronic, heterogeneous autoimmune disease short of effective therapeutic agents. A multitude of studies of SLE in the last decade have accentuated a central role of the interferon alpha (IFN-α) pathway in SLE pathogenesis. We report here a candidate therapeutic neutralizing antibody, AIA22, with a different binding epitope and discrepant neutralizing profile from the anti-multiple IFN-α subtype antibodies currently in clinical trials. AIA22 specifically interacts with multiple IFN-α subtypes, binds to the type I IFN receptor 2 (IFNAR2) recognition region of IFN-α (considered a novel antigen epitope), and effectively neutralizes the activity of almost all of the IFN-α subtypes (with the exception of IFN-α7) both in vitro and in vivo. Concurrently, structural modeling and computational design yielded a mutational antibody of AIA22, AIAmut, which exhibited substantially improved neutralizing activity to multiple IFN-α subtypes.