Dand et al. conducted a study to test if the HLA-C*06:02 allele is a predictive biomarker of biological treatment response for two drug agents commonly prescribed to patients with moderate to severe psoriasis resistant to conventional therapeutic protocols: Adalimumab, an anti-TNF-α drug, and Ustekinumab, a monoclonal antibody binding the p40 subunit, shared by IL-12 and IL-23. This evidence concerns the gene IL23A and psoriasis.