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Since the coronavirus disease outbreak in 2019, several antibody therapeutics have been developed to treat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Antibody therapeutics are effective in neutralizing the virus and reducing hospitalization in patients with mild and moderate infections. These therapeutics target the spike protein of SARS-CoV-2; however, emerging mutations in this protein reduce their efficiency. In this study, we developed a universal SARS-CoV-2 neutralizing antibody. We generated a humanized monoclonal antibody, MG1141A, against the receptor-binding domain of the spike protein through traditional mouse immunization. We confirmed that MG1141A could effectively neutralize live viruses, with an EC50 of 92 pM, and that it exhibited effective Fc-mediated functions. Additionally, it retained its neutralizing activity against the alpha (UK), beta (South Africa), and gamma (Brazil) variants of SARS-CoV-2. Taken together, our study contributes to the development of a novel antibody therapeutic approach, which can effectively combat emerging SARS-CoV-2 mutations.

We cloned and sequenced the open reading frame (ORF) cDNA encoding myostatin from the muscle of abalone (Haliotis discus hannai). The ORF cDNA of the abalone myostatin is 1134 bp and encoded 377 amino acid residues that were 60-96% homologous with the amino acids of other organism myostatins. In addition, the ORF contained a conserved proteolytic cleavage site (RXRR) and nine conserved cysteine residues in the C-terminus. Semi-quantitative RT-PCR revealed the presence of myostatin mRNA in various tissues. The strongest expression was observed in the mantle of female abalone, and the gills and heart of male abalone.

Since the huge success of PD-1 blocking antibodies in clinical studies, anti-cancer therapy has changed its strategic gear to immunotherapy, which showed the strongest potential to eradicate cancer without detrimental side effects. Antibodies targeting similar immune checkpoint proteins with immunosuppressive functions have started to surge into clinical trials. CEACAM1 (CCM1) is also a potential target for anti-cancer immunotherapy because it is an ITIM-containing inhibitory molecule expressed on activated T cells and NK cells, on which it suppresses T/NK cell-mediated pro-inflammatory immune responses. CCM1-CCM1 homophilic interaction inhibits ZAP-70 phosphorylation in the TCR proximal signaling complex, thereby suppressing T cell activation. The anti-cancer therapeutic potential of CCM1-blockade has already been demonstrated in mouse models and one of the anti-human CCM1 antibodies entered into a phase I clinical trial once. As previously reported, our clone C25 (an anti-CCM1 monoclonal antibody) activated T cells and enhanced T/NK cell-mediated tumor cell-killing in a CCM1-dependent manner. The clone C25 was further engineered to have higher efficacies through mutagenesis within the variable regions of heavy and light chains. Here, we describe mutated variants of C25 with improved in vitro tumor-killing efficacies as well as higher binding affinities while maintaining fundamental characteristics of their parental clone C25. Most importantly, C25 and its variants exclusively bind to CCM1, but not to any other homologs of the CCM family. Such strong target-specificity will be a crucial point that distinguishes our clones from the other anti-CCM1 antibodies having off-target binding activities. We are currently investigating the CCM1-dependent anti-cancer therapeutic efficacy of our final clone on the patient-derived tumor xenografts implanted in a humanized mouse model. The target-ligand expression profiling on tumor tissues from lung cancer patients revealed strong clues for patient selection criteria and co-treatment options. Citation Format: So-Young Eun, Mijung Lee, Hye-Young Park, Miyoung Oh, Hye In Yum, Aerin Yoon, Eunhee Lee, Hyemi Nam, Sungtae Yun, Hyunjung Cho, Minkyu Hur, Jaehwan Kim, Byoung Chul Cho, Jonghwa Won. Enhanced anti-tumor efficacy of CEACAM1-targeting antibody after affinity maturation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-113.

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