High levels of macrophage migration inhibitory factor (MIF) in patients with cancer are associated with poor prognosis. Its redox-dependent conformational isoform, termed oxidized MIF (oxMIF), is a promising tumor target due to its selective occurrence in tumor lesions and at inflammatory sites. A first-generation anti-oxMIF mAb, imalumab, was investigated in clinical trials in patients with advanced solid tumors, where it was well tolerated and showed signs of efficacy. However, imalumab has a short half-life in humans, 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 in vivo, while retaining affinity and specificity to oxMIF. The introduction of mutations into the Fc region known to increase antibody-dependent cellular cytotoxicity resulted in enhanced effector functions of the novel antibodies in vitro, whereas reduced cytokine release from human peripheral blood mononuclear cells in the absence of target antigen by the engineered anti-oxMIF mAb ON203 versus imalumab reveals a favorable in vitro safety profile. In vivo, ON203 mAb demonstrated superior efficacy over imalumab in both prophylactic and established prostate cancer (PC3) mouse xenograft models. In summary, our data highlight the potential of the second-generation anti-oxMIF mAb ON203 as a promising immunotherapy for patients with solid tumors, warranting clinical evaluation.