Melanoma is often surrounded with regulatory T cells (Treg) due to its immunogenic nature, which express on their surface the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). This way the melanoma dampens the immune response in its microenviroment. Recent studies regarding the mode of action for the immunotherapeutic antibody ipilimumab, emphasize that the cellular death of Treg cells is the main mechanism behind the anticancerous effect. The constant (Fc) region of ipilimumab plays a crucial role in this strategy as it mediates the cytotoxic effect on Treg cells via binding to the fragment crystallizable gamma receptor (FcγR) found on immune effector cells. To achieve the best therapeutic efficacy subtypes of FcγRIIa and FcγRIIIa need to bind to the Fc region. The purpose of this work was to use molecular modeling techniqes to asses an antibody mutation, which was shown to increase binding affinity of FcγRIIa and FcγRIIIa and in turn could lead to greater efficacy of therapy. Using homology modeling we modeled the entire structure of ipilimumab. The binding affinity was assessed after molecular dynamics simulation using the program CHARMM. An important aspect to consider in the efficacy of such therapies is the genetic variability of the individual which is described by pharmacogenomics. This aspect of ipilimumab therapy was assessed using the web server GenProBiS, which predicts binding sites of proteins and outputs the corresponding documented variations. Our current results do not confirm our hypothesis of greater binding affinity of the mutated Fc region to FcγRIIa and FcγRIIIa. The work done contributes to understanding the importance of molecular dynamics simulations in potential improvments to pharmacological properties of biological drugs.
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