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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
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.
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)
ACKNOWLEDGEMENTS
Many colleagues at STI, Allegheny GeneralHospital, and Revivicor
HISTORY OF XENOTRANSPLANTATION
XENOTRANSPLANTATION:
THE PIG AS THE ORGAN-SOURCE
XENOTRANSPLANTATION
Advantages 1:
1. Unlimited supply of donor organs.
2. Organs available electively.
3. Avoids effects of brain death.
4. Infection-free donors.
XENOTRANSPLANTATION
Advantages 2:
1. Borderline candidates
2. “Cultural” barriers to deceased donation (e.g. Japan)
3. Diabetes mellitus/cell transplants
CLINICAL PIG-TO-HUMAN XENOTRANSPLANTATION
Organs (kidney, heart, liver, lung)IsletsCorneas Neuronal cellsHepatocytesSkinRed blood cells
XENOTRANSPLANTATION:
BARRIERS
BARRIERS TO XENOTRANSPLANTATION
IMMUNOLOGIC Physiologic Safety (risk of infection) Ethical Regulatory / Legal
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
PIG ORGAN XENOTRANSPLANTATION
IN NONHUMAN PRIMATES
PIG-TO-BABOON KIDNEY TX (DAY 0)
PIG-TO-BABOON KIDNEY TX (HAR)
PORCINE HUMAN
αGal
NeuGc
ß4GalNT2
ABH
NeuAc
XENOTRANSPLANTATION:
EXPERIMENTAL PROGRESS
Solution 1
Gene-knockout of known antigenic targets for human anti-pig antibodies, e.g., αGal, NeuGc, ß4GalNT2
WT
GTKO/CD46
GTKO/CD46
/Neu
GcKO
Human
0
2
4
6
8
Rel
ativ
e M
FI
Human antibody binding to the AECs
*p<0.05 (n=6)
WT
GTKO/CD46
GTKO/CD46
/Neu
GcKO
Human
0
10
20
30
40
50
Rel
ativ
e M
FI
* *
*
*
**
IgM IgG
Solution 2
Pigs transgenic for a human protein, e.g., complement-
regulatory, coagulation-regulatory, anti-inflammatory, immunosuppressive agent
IsotypeGE pig AECs
Human AECs
Surface expression on genetically-engineered (GE) pig and human aortic endothelial cells (AECs)
CD55 (DAF) CD141 (TBM)CD46
CD55 (DAF) CD141 (TBM)CD46
GENETICALLY-ENGINEERED PIGS CURRENTLY AVAILABLE
Revivicor has produced pigs with 20 different genetic manipulations
Some pigs have 7 modifications
Worldwide, 40 different manipulations
ELICITED ANTI-PIG ANTIBODIES
Unless prevented by
immunosuppressive therapy, after
exposure to a pig organ or cells,
anti-pig antibodies can increase
>10-fold
PROGRESS IN PIG-TO-NHP KIDNEY TX
Progress in immunosuppressive therapy:Conventional (e.g., tacrolimus, steroids)Costimulation blockade(Genetically-engineered pigs)
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)
PIG-TO-NHP RENAL XENOTX
GTKO/hDAF Rhesus macaque:
T cell depletion,
anti-CD154, MMF/steroids
BARRIERS TO XENOTRANSPLANTATION
Immunologic PHYSIOLOGIC Safety (risk of infection) Ethical Regulatory / Legal
B9313 - INCREASE IN SIZE OF KIDNEY
BARRIERS TO XENOTRANSPLANTATION
Immunologic Physiologic SAFETY (RISK OF
INFECTION) Ethical Regulatory / Legal
SAFETY OF XENOTRANSPLANTATION
Concern regarding potential transfer of infectious microorganisms to (1) recipient, (2) public
SAFETY OF XENOTRANSPLANTATION
‘Remaining’ potential risk:
Porcine endogenous retroviruses (PERVs)
BARRIERS TO XENOTRANSPLANTATION
Immunologic Physiologic Safety (risk of infection) ETHICAL REGULATORY / LEGAL
GENETICALLY-ENGINEERED PIGS
1. No unacceptable implications for the health and welfare of the pig2. No serious ethical objections to the genetic procedure
- brain (pig or human)- reproduction of one species by
the otherThe Netherlands
“There are many ways of losing money.
Women are the most fun. Gambling is the fastest. Research is the most certain.”
Lord HivesChairman of Rolls Royce
GENETICALLY-ENGINEERED PIGS
Recent new technologies, e.g., Zinc finger nucleasesTALENSCRISPR/Cas9
will facilitate the production of pigs with multiple genetic modifications
History tells us that procedures that were inconceivable yesterday, and are barely achievable today, often become routine tomorrow.
Thomas E. Starzl, 1982
POTENTIAL ALTERNATIVES TO XENOTRANSPLANTATION
1. Human stem cells2. Regenerative medicine3. Cell-based mechanical devices
FIRST CLINICAL TRIAL
? Patients highly-sensitized to alloantigens (high PRA)
? Patients with problems of vascular access for dialysis
“It is often sufficient to know, in the large, that
a thing may be possible”
Littre, 1710Royal Academy of
ScienceParis
One day “making a pig of yourself” could have a whole new meaning
THANK YOU