Simulect 20 mg injection Simulect contains Basiliximab, a chimeric murine/human monoclonal antibody (IgG1κ) directed against the alpha chain of the interleukin-2 (IL-2) receptor (CD25 antigen), which is expressed on the surface of T-lymphocytes in response to antigenic activation. By binding specifically to CD25, Basiliximab competitively inhibits IL-2-mediated activation and proliferation of T-lymphocytes, a key pathway in cellular immune response to allografts. It is indicated for the prophylaxis of acute organ rejection in patients receiving renal transplantation, as part of an immunosuppressive regimen that includes cyclosporine and corticosteroids.