intravenous immunoglobulin + leflunomide

**Intravenous immunoglobulin + leflunomide** is a combination therapy consisting of intravenous immunoglobulin (IVIG), a purified polyclonal immunoglobulin G (IgG) preparation derived from pooled human plasma, and leflunomide, a synthetic small molecule immunomodulator that acts primarily as a pyrimidine synthesis inhibitor. IVIG is typically used for immune modulation in various autoimmune, inflammatory, and immunodeficiency states, exerting effects via mechanisms such as Fc receptor blockade, modulation of complement activation, and interference with pathogenic autoantibodies. Leflunomide is orally administered in standard use but, when used in combination, retains its mechanism as a prodrug rapidly converted to the active metabolite A77 1726, which inhibits dihydroorotate dehydrogenase. This enzyme inhibition reduces pyrimidine synthesis, resulting in cytostatic effects on proliferating lymphocytes. The combination has been investigated for the treatment of polyomavirus (BK virus) nephropathy post-transplant, where both immunomodulatory and antiviral effects may contribute. The addition of leflunomide to IVIG appears to enhance reduction of BK viral load in kidney transplant recipients compared to IVIG alone[1].