Therefore, we speculate that pathologic properties of MIF can be attributed to oxMIF, which reflects a druggable isoform of MIF in cancer (13). There is substantial scientific evidence that cancer cells utilize secreted MIF to evade immune cellCmediated antitumor responses in the tumor microenvironment (49). increased aggregation propensity, and an unfavorable pharmacokinetic profile. Here, we aimed to optimize imalumab by improving its physicochemical characteristics and boosting its effector functions. Point mutations introduced into the variable regions reduced hydrophobicity and the antibodies aggregation potential, and increased plasma half-life and tumor accumulation safety profile. experimental sepsis, contact hypersensitivity, colitis, prostate KC7F2 cancer and ovarian cancer xenograft mouse models, and glomerulonephritis rat models (10, 11, 16, 17). These effective mAbs bind to two regions of MIF, amino acids 50C68 [epitope of BaxB01 (RCSB PDB: 6FOE) sharing the same variable region with Bax69 = imalumab] or amino acids 86C102 (epitope of BaxG03 and BaxM159), that form a (17). Several and studies have demonstrated a crucial role of ADCC and antibody-dependent cellular phagocytosis (ADCP) in tumor elimination by immune cells (20C26). The antibody Fc region, specifically the CH2 domain, can be mutated to increase Fc affinity to the activatory human Fc FLJ12894 receptors (FcR), particularly FcRIIIA and FcRIIA (23, 26). Within the IgG subclass, human IgG1 is the most effective at inducing ADCC by natural killer (NK) cells (27). Panitumumab (anti-EGFR, IgG2) did not elicit any ADCC by NK cells, but it potently induced ADCC by myeloid cells (monocytes/macrophages and neutrophils) via their FcRIIA (27, 28). Several CH2 mutations combined with isotypic modifications (IgG1/2 hybrid) were shown to be particularly efficient in inducing ADCC (29, 30). Human IgG1 binds with greater affinity to the V158/V158 allotype of FcRIIIA than to F158/F158 (21, 25, 31). This difference in affinity and subsequent ADCC are significant determinants for efficacy of rituximab (anti-CD20, IgG1) therapy (21). Two recently approved Fc-engineered mAbs, margetuximab (anti-Her2) and tafasitamab (anti-CD19), are examples of successful ADCC enhancement against both allotypes of FcRIIIA (22, 32). Here, we describe the engineering and evaluation of second-generation anti-oxMIF mAbs with highly improved physicochemical and biological properties compared with imalumab. It is KC7F2 well known that controlling hydrophobicity and aggregation can improve antibody stability, manufacturability, formulation, and safety (33, 34). We identified residues in the variable domains of imalumab that contribute to a high surface hydrophobicity and aggregation propensity, which potentially led to the short half-life and limited efficacy. By introducing well-selected point mutations in the variable KC7F2 regions, we reduced hydrophobicity and aggregation propensity and improved the pharmacokinetic profile (i.e., extend plasma half-life and tumor accumulation) of the second-generation anti-oxMIF antibodies. Because imalumab, a fully human IgG1, was reported to be devoid of effector functions (17), we aimed to introduce potent effector functions via mutations in the heavy-chain constant domain name of imalumab. Novel variable domains combined with an IgG1/IgG2 hybrid heavy-chain constant region carrying two point mutations (S239D/I332E) in the CH2 domain name were intended to improve the manufacturability of the antibodies as well as enhance ADCC activity. The beneficial effects of the bioengineering efforts were confirmed by Peripheral blood mononuclear cell (PBMC)-mediated ADCC assays and by enhanced tumor growth inhibition in both prophylactic and therapeutic settings in prostate cancer KC7F2 (PC3) mouse xenograft models. Materials and Methods Expression and purification of human and mouse MIF SHuffle T7 Express lysY Qualified (New England BioLabs) were transfected with a Champion pET303/CT-His plasmid (Thermo Fisher Scientific, catalog no. K630203) made up of either human or mouse MIF cDNA. The cDNA sequences were taken from uniprot.org under accession number P14174 and P34884 for human and mouse MIF, respectively. MIF is usually expressed by an inducible T7 promoter under the control of a lac operator. The plasmid possesses the bacterial antibiotic KC7F2 resistance gene AmpR under the poor AmpR promoter for clone selection with ampicillin. LB low salt broth (LLG Labware) made according to the manufacturer’s instructions including 100 g/mL ampicillin (Sigma-Aldrich) was used for the start of the expression. The culture was incubated at 37C overnight shaking at 180 rpm. Super.