Natalizumab is a humanized monoclonal antibody to α4β1 integrin and is approved for the treatment of Multiple Sclerosis. In patients there is a great variation in drug response and there is much evidence that genetic contributors play an important role in defining an individual's susceptibility. Natalizumab binds to α4-residues Gln-152, Lys-201, Lys256, and these seem to be essential for its activity. Studies on a range of species in disease model have showed a loss of reactivity when any one of those three residues were different to human. Based on these animal studies, we thought that the single nucleotide polymorphism in the ITGA4 human gene causing a lysine to arginine transversion at amino acid position 256 require further investigations in the context of individual drug susceptibility. So, the aim of our study was to investigate the association between this genetic polymorphism and the resistance to natalizumab. We had applied molecular dynamics simulation to study the possible conformational changes induced by Lys256Arg transversion on the overall structure of integrin and we have analyzed the binding affinities of natalizumab in the non-mutated and mutated structures through HINT score. We found that this SNP does not affect the VLA4-natalizumab interaction. Instead, the binding affinities are slightly higher in the mutated complex than in the wild-type. We reported one of the first work in which MD simulation was applied in the pharmacogenetic context, and this approach is rapid and cost effective, since a population survey is carried out only after the positive prediction of simulation.