1. Immunosuppression Withdrawal in Adult and Pediatric Liver Transplant Recipients What do we know? What do we not know? Where should we go? Sandy Feng, MD, PhD University of California San Francisco 11 th Banff Meeting on Allograft Pathology

2. What do we know? A (substantial) proportion of (highly) selected adult and pediatric liver transplant recipients can successfully withdraw from immunosuppression – the definition of operational tolerance  Historically, reports have described single center experiences rather than trials  Patients have been varied Non-compliant Contraindication to ongoing immunosuppression Elective withdrawal  Success has typically been defined as maintaining normal allograft function for one year Allograft function has been typically assessed by liver tests

3. What do we know? Recently, clinical trials of immunosuppression withdrawal have been undertaken  Enrollment of a more homogeneous population  Defined algorithm for withdrawal  Typically accompanied by mechanistic studies to identify biomarker of operational tolerance Some trials have attempted early withdrawal after induction with a depleting antibody preparation  Thymoglobulin  Alemtuzumab Other trials have focused on stable long-term adult and pediatric recipients

4. Tolerance Induction Trials Alemtuzumab / Tacrolimus Thymoglobulin / Sirolimus Thymoglobulin / Tacrolimus

5. ITN024: Alemtuzumab / Tacrolimus Monotherapy Tx Month 0 - 3 Month 4 - 12 Month 12 - 24 Corticosteroids Alemtuzumab 30 mg days 0 & 4 Tacrolimus 8 - 12 ng/mL 5 - 10 ng/mL Withdrawal

6. ITN024: Alemtuzumab / Tacrolimus Monotherapy Outcome of Immunosuppression Withdrawal 27 enrolled 10 initiated withdrawal

7. Thymoglobulin / Sirolimus Monotherapy Donckier et al., Transplantation 2009 Tx Month 1 Month 2 Month 3 Month 4 - 6 Corticosteroids Discontinue by end of Month 1 ATG 3.75 mg/kg days 1-5 SRL 8-12 ng/mL Withdrawal to discontinue SRL between months 4 - 6

8. Thymoglobulin / Sirolimus Monotherapy Outcome of Immunosuppression Withdrawal D140 D206D124 D280 D246 D163 Donckier et al., Transplantation 2009

9. Thymoglobulin / Low Dose Tacrolimus Monotherapy vs. Standard Tacrolimus ATG 9mg/kg Tac 5 – 12 ng/mL Months 0 - 3 Assess for IS withdrawal; 10 qualified Tac 10–15ng/mL Months 0 - 3 Tac 7–12ng/mL Months 4 - 12 Benitez et al., AJT, 2010

10. Thymoglobulin / Low Dose Tacrolimus Monotherapy Acute Rejection Rates ATG-FControlP value Intention-to-treat analysis Overall67%31%0.033 Months 0 - 352%25%0.09 Months 4 - 1262%6%0.001 Ad hoc / per protocol analysis Overall83%31%0.008 Months 0 - 350%23%ns Months 4 - 1283%8%< 0.001 Benitez et al., AJT, 2010

11. Thymoglobulin / Low Dose Tacrolimus Monotherapy Acute Rejection Rates 123456123456 7 8 9 10

12. Spontaneous Operational Tolerance

13. ITN030: Tacrolimus ± Mycophenolate Month 1 - 3 Month 4 - 12 Month 13 - 24 Withdrawal Corticosteroids d/c by end of month 3 Tacrolimus 8 - 12 ng/mL 5 - 10 ng/mL Withdrawal MMF If started, d/c 3 mos before withdrawal Eligibility

14. Prospective Study of Immunosuppression Withdrawal Immunosuppression withdrawal 6-9 months Withdrawal Failure Rejection (Non-TOL) 57 Stable liver function (TOL) 40 97 stable liver Recipient >3 years Liver Transplantation 12 month follow-up PBMC immunophenotyping PBMC/Whole blood/Liver tissue gene expression 6-9 months weaning 12 months follow-up Participating centers: Hospital Clinic Barcelona, University Tor Vergata Rome, University Hospitals Leuven

15. ITN029: Immunosuppression Withdrawal for Pediatric Parental Living Donor Liver Transplant Recipients Single arm, three center pilot trial of 20 patients Sandy Feng, M.D., Ph.D. Phil Rosenthal, M.D. John Roberts, M.D. Udeme Ekong, M.D., Ph.D. Estella Alonso, M.D. Peter Whitington, M.D. Steven Lobritto, M.D. Jean Emond, M.D.

16. 12 of 20 Participants Met the Primary Endpoint: Off Immunosuppression for 30.0 – 50.7 Months

17. 8 of 20 Participants Did Not Meet the Primary Endpoint I/E Violation During Withdrawal After Withdrawal

18. What do we NOT know? Who are the appropriate patients to withdraw from immunosuppression?  Demographic factors  Clinical characteristics  Allograft histology When should immunosuppression be withdrawn?  Minimize risk / maximize withdrawal When should immunosuppression be re-initiated?  Development of alloantibodies  Allograft histology  Other parameters

19. Where do we go from here? Rigorously designed, adequately powered clinical trials to answer critical questions Sufficiently long follow-up to critically assess evolution of alloantibodies and allograft histology Intensive effort to derive biomarker(s) of and / or mechanistic insight into operational tolerance  Demonstration that immunosuppression withdrawal is beneficial will be difficult and potentially impossible  Risk reduction will enhance equipoise in favor of withdrawal Facilitate withdrawal earlier after transplantation

20. Where do we go from here? Novel approaches to induce tolerance should be pursued in the liver transplant arena.  Chimerism approaches utilized in (Iiving donor) kidney transplantation are impractical and perhaps excessively toxic for the liver transplant population  Regulatory T cells may, however, offer the opportunity to modulate the allo-immune response. Enhance frequency of tolerance Accelerate the development of tolerance

21. Conclusions (1) Immunosuppression withdrawal has been undertaken in both adult and children Results have been particularly encouraging for stable, long-term recipients  Attempts at immunosuppression withdrawal early after transplantation, with or without an induction regimen have met with modest success In the short term, immunosuppression withdrawal appears to be reasonably safe  Acute rejection has occurred frequently  Chronic rejection has occurred rarely  Allograft histology appears stable Tolerance has been durable

22. Conclusions (2) In spite of an intuitive appeal, there is no evidence that immunosuppression withdrawal is beneficial. There is substantial concern regarding the long-term safety of withdrawal, particularly relating to allograft histology and the development of alloantibodies. Therefore, current equipoise does not favor withdrawal for the majority of liver transplant recipients. Future efforts must focus on  Mitigating short-term risk by identifying a biomarker predictive of operational tolerance  Studying long-term risk

23. Acknowledgements for ITN029 ITN TADA Group Vicki Seyfert-Margolis Deborah Phippard Mark Mueller Adam Asare Jason (Zhugong) Liu Mary Carmelle-Philogene Zhong Gao Larry Turka A. Jake Demetris Site Coordinators Sharon Blaschka Therese Hess Jonah Zaretsky ITN CTG Nadia Tchao Peter Sayre Nariman Nasser Ross Jamison Doug Norman NIAID Nancy Bridges Melissa DePaulis Rho David Ikle Katie Poole Alberto Sanchez-Fueyo