New trends in transplantation: the use of Thymoglobulin®

A review on comparing two commonly used rabbit anti-thymocyte globulins as induction therapy in solid organ transplantation

INTRODUCTION

Two rabbit anti-thymocyte globulins (ATGs) (Thymoglobulin™ and ATG-Fresenius (ATG-F)™) have been used commonly for induction immunosuppression and treatment of acute rejection in solid organ transplantation. Therefore, literature review on comparative efficacy and side-effect profile of them would be of clinical interest.

AREAS COVERED

This review evaluated all comparative studies in English language, focusing on the solid organ transplant patients who received Thymoglobulin or ATG-F as induction therapy. This review concluded that compared to ATG-F, Thymoglobulin possibly provides better protection against acute rejection and improves patient and graft survival but may result in more cytomegalovirus infection and post-transplant malignancy. Thymoglobulin produced more leukocyte depletion with a greater delay to recover, while ATG-F had more reduction effects on platelet and erythrocyte counts with an increased need to erythropoiesis-stimulating agent.

EXPERT OPINION

The benefits of induction therapy with ATGs must be weighed against the costs and post-transplant complications. It is suggest that there is no substantial clinical difference between these two rabbit ATGs and each may be considered as induction therapy for solid organ transplantation based on availability and drug cost. Of special importance is adding antiviral therapy to the treatment regimen of patients who receive ATGs as induction therapy.

Induction immunosuppression improves long-term graft and patient outcome in organ transplantation: an analysis of United Network for Organ Sharing registry data

BACKGROUND

Induction agents have been shown to reduce the rate of acute rejection. They have not been clearly shown to improve graft and patient survival.

METHODS

United Network for Organ Sharing registry data were analyzed to show the status of induction therapy in the United States and to determine the effect of induction therapy on long-term graft and patient survival.

RESULTS

Since establishment of the United Network for Organ Sharing renal transplant registry, there have been three distinct eras of induction regimen: (1) the low-induction, old antibody era, 1987 to 1993, when antilymphocyte globulin and muromonab-CD3 were the major agents; (2) a high-induction, transitional era, 1994 to 2002, when basiliximab (1998), daclizumab (1998), and rabbit antithymocyte globulin (rATG; 1999) replaced antilymphocyte globulin and muromonab-CD3, with maintenance agents also used; (3) the high-induction, modern antibody era, 2003 to present, with most patients receiving rATG, basiliximab, daclizumab, or alemtuzumab (2003). Induction recipients had higher graft and patient survival rates than nonrecipients in all categories of organ transplant. The improvement was statistically significant in kidney, liver, and lung transplants, although liver and lung recipients had a lower percentage of patients receiving induction than did kidney patients. Kidney transplant recipients on alemtuzumab with steroids had the lowest risk of graft failure, followed by those on alemtuzumab alone, rATG with steroids, rATG alone, and then basiliximab with steroids. Improvement was not statistically significant with daclizumab (alone or with steroids), basiliximab alone, or steroids alone.

CONCLUSION

Induction immunosuppression improved graft and patient outcome for most organ transplants. Depleting agents (alemtuzumab and rATG)--especially in combination with steroids--seem to be more efficient in preventing renal graft failure than nondepleting agents (basiliximab and daclizumab).

Intensive pharmacological immunosuppression allows for repetitive liver gene transfer with recombinant adenovirus in nonhuman primates

Repeated administration of gene therapies is hampered by host immunity toward vectors and transgenes. Attempts to circumvent antivector immunity include pharmacological immunosuppression or alternating different vectors and vector serotypes with the same transgene. Our studies show that B-cell depletion with anti-CD20 monoclonal antibody and concomitant T-cell inhibition with clinically available drugs permits repeated liver gene transfer to a limited number of nonhuman primates with recombinant adenovirus. Adenoviral vector-mediated transfer of the herpes simplex virus type 1 thymidine kinase (HSV1-tk) reporter gene was visualized in vivo with a semiquantitative transgene-specific positron emission tomography (PET) technique, liver immunohistochemistry, and immunoblot for the reporter transgene in needle biopsies. Neutralizing antibody and T cell-mediated responses toward the viral capsids were sequentially monitored and found to be repressed by the drug combinations tested. Repeated liver transfer of the HSV1-tk reporter gene with the same recombinant adenoviral vector was achieved in macaques undergoing a clinically feasible immunosuppressive treatment that ablated humoral and cellular immune responses. This strategy allows measurable gene retransfer to the liver as late as 15 months following the first adenoviral exposure in a macaque, which has undergone a total of four treatments with the same adenoviral vector.