Daclizumab (Zenapax) is a murine-human chimaerised monoclonal antibody to the IL-2Rα receptor of T cells. It is used to prevent rejection in organ transplantation, especially in kidney transplants.

It is given in multiple doses, the first 1 hour before the transplant operation and 5 further doses given at two week intervals after the transplant. These saturate the receptors and prevent T cell activation and thus prevent formation of antibodies against the transplant.

Like the similar drug basiliximab, daclizumab reduces the incidence and severity of acute rejection in kidney transplantation without increasing the incidence of opportunistic infections.