Safe administration of a humanized murine antibody after anaphylaxis to a chimeric murine antibody

Background. Basiliximab and daclizumab are potent and relatively safe immunosuppressive induction agents used in transplantation. These chimeric or humanized monoclonal antibodies, respectively, act by binding to the a chain of interleukin-2 receptors on activated T lymphocytes. Herein, the authors describe successful transplant induction therapy with a humanized murine antibody in a patient with a history of anaphylaxis to a chimeric murine antibody. Methods. The authors report a 42-year-old woman who received a dose of basiliximab without adverse reaction before an anticipated renal transplant that was canceled. Two weeks later, she received a second dose of basiliximab. Within 10 min of receiving the second dose, she developed chest tightness, shortness of breath, tongue swelling, diffuse pruritic rash, and skin flushing. Results. The authors hypothesized that her anaphylaxis was mediated by immunoglobulin (Ig) E antibodies to basiliximab. Consistent with this hypothesis, intradermal administration of a 1: 100 dilution of basiliximab induced a 10 × 10-mm flare. The authors sought to find an alternative immunosuppressive agent for this patient. The patient elicited prick and intradermal skin testing responses to horse and rabbit polyclonal antithymocyte antibody preparations. However, she mounted neither a prick nor an intradermal response to daclizumab. The patient was administered daclizumab without any adverse effects. Conclusions. The negative skin test and safe administration of daclizumab is surprising because the similarity of these hybrid antibodies would have predicted similar IgE responsiveness and clinical outcome. The authors propose that patients who develop anaphylaxis to basiliximab or other chimeric antibodies may be candidates for treatment with a humanized antibody preparation such as daclizumab in the presence of a negative skin test to the humanized agent.