Severe active local or systemic infections. Chronic kidney disease with an eGFR <30 mL/min/1.73 m2. Anemia with hemoglobin levels below 8 mg/dL, lymphopenia with an absolute lymphocyte count <500 cells/mm3. Pregnancy. Administration concurrently with OAT3 inhibitors and other DMARDS or JAK3 inhibitors. The gene discussed is SLC22A8; the disease is anemia (phenotype).