IFN-α has been extensively used for the treatment of various malignancies during the last two decades, demonstrating an improved clinical outcome of hematological malignancies (chronic myeloid leukemia (CML), cutaneous T cell lymphoma, hairy-cell leukemia (HCL), multiple myeloma, solid tumors including malignant melanoma, RCC, AIDS-related Kaposi’s sarcoma, and viral syndromes (hepatitis C, hepatitis B, severe acute respiratory syndrome, and COVID-19) [196,197]. This evidence concerns the gene IFNA1 and hairy cell leukemia.