The chimaeric monoclonal antibody basiliximab specifically binds the alpha subunit of the interleukin-2 (IL-2) receptor on activated T lymphocytes. Through competitive antagonism of IL-2, basiliximab supplements standard immunosuppressive therapy after renal transplantation. < or =24 Hours after a single intravenous dose of basiliximab 2.5 to 25 mg, approximately 90% of available IL-2 receptors on T lymphocytes were complexed with the drug. This level of basiliximab binding was maintained for 4 to 6 weeks when renal transplant patients received basiliximab 20 mg 2 hours before and then 4 days after transplantation surgery. In 2 large, well-designed trials, the percentage of patients with biopsy-confirmed acute rejection episodes after renal transplantation was significantly lower with basiliximab 20 mg (administered 2 hours before and then 4 days after transplantation surgery; 30 or 33%, respectively) than placebo (44 or 46%) at 6 months after surgery. Basiliximab was well tolerated during clinical trials. The incidence of infections (including active cytomegalovirus infection) and post-transplant lymphoproliferative disorders was similar with basiliximab and placebo. Cytokine release syndrome was not observed in patients who received basiliximab.