This may be explained by the fact that alefacept does not affect the naive T cell population.[39, 40] A range of inflammatory genes such as IFN-γ, STAT1, MIG (CXCL9) and iNOS are reduced.[41, 42] As the first biologic to be approved by the Food and Drug Administration (FDA) for moderate to severe psoriasis, alefacept has helped 70% of patients reach at least PASI 50, a clinically significant endpoint for psoriatic patients that indicates 50% improvement in PASI scores in a randomized controlled trial.[43]. Here, CXCL9 is linked to psoriasis.