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KIDNEY XENOTRANSPLANTATION - THE NEXT GREAT BREAKTHROUGH IN NEPHROLOGY? David K.C. Cooper MD, PhD, FRCS Thomas E. Starzl Transplantation Institute University of Pittsburgh
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COMPETING INTERESTS I am Chairman of the Scientific Advisory Board of Revivicor, Inc., Blacksburg, VA, but I have no financial interest in the company and do not receive any remuneration whatsoever.
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REVIVICOR Small biotechnology company (25 staff) that concentrates its effort on the genetic engineering of pigs for medical purposes: 1. Xenotransplantation 2. Human immunoglobulin (also for biodefense)
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ACKNOWLEDGEMENTS Many colleagues at STI, Allegheny General Hospital, and Revivicor
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HISTORY OF XENOTRANSPLANTATION
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XENOTRANSPLANTATION: THE PIG AS THE ORGAN-SOURCE
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XENOTRANSPLANTATION Advantages 1: 1. Unlimited supply of donor organs. 2. Organs available electively. 3. Avoids effects of brain death. 4. Infection-free donors.
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XENOTRANSPLANTATION Advantages 2: 1. Borderline candidates 2. “Cultural” barriers to deceased donation (e.g. Japan) 3. Diabetes mellitus/cell transplants
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CLINICAL PIG-TO-HUMAN XENOTRANSPLANTATION Organs (kidney, heart, liver, lung) Islets Corneas Neuronal cells Hepatocytes Skin Red blood cells
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XENOTRANSPLANTATION: BARRIERS
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BARRIERS TO XENOTRANSPLANTATION IMMUNOLOGIC Physiologic Safety (risk of infection) Ethical Regulatory / Legal
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BARRIERS TO XENOTRANSPLANTATION “Immunologic” includes: 1. Innate immune response (e.g., antibody, complement, macrophages) 2. Adaptive immune response (e.g., T and B cells) 3. Coagulation dysfunction (e.g., thrombin, platelets) 4. Inflammation
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PIG ORGAN XENOTRANSPLANTATION IN NONHUMAN PRIMATES
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PIG-TO-BABOON KIDNEY TX (DAY 0)
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PIG-TO-BABOON KIDNEY TX (HAR)
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PORCINE HUMAN αGal NeuGc ß4GalNT2 ABH NeuAc
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XENOTRANSPLANTATION: EXPERIMENTAL PROGRESS
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Solution 1 Gene-knockout of known antigenic targets for human anti-pig antibodies, e.g., αGal, NeuGc, ß4GalNT2
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Human antibody binding to the AECs *p<0.05 (n=6) * * * * * * IgMIgG
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Solution 2 Pigs transgenic for a human protein, e.g., complement- regulatory, coagulation- regulatory, anti-inflammatory, immunosuppressive agent
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Isotype GE pig AECs Human AECs Surface expression on genetically-engineered (GE) pig and human aortic endothelial cells (AECs) CD55 (DAF)CD141 (TBM)CD46CD55 (DAF)CD141 (TBM)CD46
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GENETICALLY-ENGINEERED PIGS CURRENTLY AVAILABLE Revivicor has produced pigs with 20 different genetic manipulations Some pigs have 7 modifications Worldwide, 40 different manipulations
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ELICITED ANTI-PIG ANTIBODIES Unless prevented by immunosuppressive therapy, after exposure to a pig organ or cells, anti-pig antibodies can increase >10-fold
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PROGRESS IN PIG-TO-NHP KIDNEY TX Progress in immunosuppressive therapy: Conventional (e.g., tacrolimus, steroids) Costimulation blockade (Genetically-engineered pigs)
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PROGRESS IN PIG-TO-NHP KIDNEY TX The Emory group had one monkey surviving >10 months with a life- supporting pig kidney graft (The NIH group had two baboons surviving >1 year after a heterotopic heart graft)
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PIG-TO-NHP RENAL XENOTX GTKO/hDAFRhesus macaque: T cell depletion, anti-CD154, MMF/steroids
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BARRIERS TO XENOTRANSPLANTATION Immunologic PHYSIOLOGIC Safety (risk of infection) Ethical Regulatory / Legal
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B9313 - INCREASE IN SIZE OF KIDNEY
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BARRIERS TO XENOTRANSPLANTATION Immunologic Physiologic SAFETY (RISK OF INFECTION) Ethical Regulatory / Legal
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SAFETY OF XENOTRANSPLANTATION Concern regarding potential transfer of infectious microorganisms to (1) recipient, (2) public
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SAFETY OF XENOTRANSPLANTATION ‘Remaining’ potential risk: Porcine endogenous retroviruses (PERVs)
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BARRIERS TO XENOTRANSPLANTATION Immunologic Physiologic Safety (risk of infection) ETHICAL REGULATORY / LEGAL
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GENETICALLY-ENGINEERED PIGS 1. No unacceptable implications for the health and welfare of the pig 2. No serious ethical objections to the genetic procedure - brain (pig or human) - reproduction of one species by the other The Netherlands
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“There are many ways of losing money. Women are the most fun. Gambling is the fastest. Research is the most certain.” Lord Hives Chairman of Rolls Royce
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GENETICALLY-ENGINEERED PIGS Recent new technologies, e.g., Zinc finger nucleases TALENS CRISPR/Cas9 will facilitate the production of pigs with multiple genetic modifications
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History tells us that procedures that were inconceivable yesterday, and are barely achievable today, often become routine tomorrow. Thomas E. Starzl, 1982
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POTENTIAL ALTERNATIVES TO XENOTRANSPLANTATION 1. Human stem cells 2. Regenerative medicine 3. Cell-based mechanical devices
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FIRST CLINICAL TRIAL ? Patients highly-sensitized to alloantigens (high PRA) ? Patients with problems of vascular access for dialysis
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“It is often sufficient to know, in the large, that a thing may be possible” Littre, 1710 Royal Academy of Science Paris
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One day “making a pig of yourself” could have a whole new meaning
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THANK YOU
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