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The Xenotransplantation Debate Continues...
 
QUIRKS AND QUARKS
Canadian Broadcasting Corporation National Radio
February 28, 1998


The following transcript is of a debate aired on Canadian Broadcasting Corporation (CBC) on Saturday, February 28, 1998.  For those of us who believe that our best hope for a near-term cure for diabetes is the xenotransplantation of encapsulated pig islets without immunosuppression, these issues will be of great interest.
 

BOB MCDONALD (CBC):In a recent article in Nature Medicine, a group of prominent scientists called for a stop to all experimental transplants from animals to humans. And that sparked heated discussion among researchers. Today we are going to continue that debate. Dr. Daniel Salomon opposes a moratorium. He is a transplant physician and scientist at the Scripps Research Institute in California. Dr. Fritz Bach is a xenotransplantation researcher at Harvard Medical School. He led the call for the moratorium. Dr. Bach and Dr. Salomon, welcome to Quirks and Quarks.

BOTH: Thank you.

MCDONALD (CBC): First of all, Dr. Bach, why did you call for a moratorium on this research?

DR. FRITZ BACH: There is an infectious risk that an organism, an infectious organism, would come from an organ transplanted from a pig, let us say, to a patient, infect that patient. But the real problem is that such an infection could then spread to the general population. Since the public is being put at risk it has to be the public in some way that both understands that risk, understands the procedures, and has the opportunity to have serious input about whether we should go ahead, and under what circumstances we should go ahead.

MCDONALD: Dr. Salomon, why are you against the moratorium?

DR. DANIEL SALOMON: Well, I think three quick points should be made, and then we can amplify them perhaps in the discussion that follows. First, public discussion of new fields in research is critical. I mean, it's a duty of all of us in medicine and science, and I'm here to do just that. However, you cross a line when you make regulatory approval, call for a regulatory approval halt based on the need for further discussion. There has been substantial discussion of xenotransplantation. The second issue that we should get into is risk. Risk is real. I've written about this in the New England Journal of Medicine and spoken, basically, around the world on it. However, it's very important to understand that the risk is low and that is the considered opinion of a broad spectrum of infectious disease experts from around the world. The most responsible decision now is to go forward with limited, highly supervised, very strict outcome-based research. The main point that we have to realize, this is not an academic exercise. Organ shortage results in the death of approximately 30,000 people in North America alone every year. These patients need to provide a direction for the future that will address this issue. I'm sure Dr. Bach agrees.

MCDONALD (CBC): Well, let's talk about that risk. Dr. Bach, how do you see it? How serious is the risk of transplanting organs, or even just tissues, from animals to humans?

BACH: I do not think we know what the risk is, and I've been very hesitant to call it low, minuscule, or certainly huge. We don't know what the risk is and the risk is there. Nobody questions that. A virus, and I take a virus only as an example, and it's not only the retroviruses. Any infectious particle that could infect the patient to his or her own close contacts, and from those close contacts to the general populations. We could have another AIDS like epidemic. This has to be presented to the public, they have to be educated, and I tell you they are not. Whatever has been...with all the massive amount of newspaper articles and TV, they're not educated. And get some actual feedback of decision making from the public, how they advise. They are the ones at risk.

MCDONALD (CBC): Dr. Salomon, how do you see this risk being managed?

SALOMON: I think first we have to make a couple of scientific points about the risk. Because at the moment we are just talking about our opinions. First of all, you have to understand that pigs have been a part of agriculture in the world - in the United States, North America, Europe, Asia - for decades and decades and the health of pig herds is something that literally thousands of hours of experimental work has been done, both clinically and in the laboratory. So pigs as potential donors and the infectious diseases of pigs is something that is extremely well characterized. Now, of course, do we know everything today that we will know tomorrow? No way. There is always going to be the possibility of discovering new things. A second issue is that there now already is significant clinical experience with xenotransplantation with pig tissues. There have been over 40 perfusions of patients with end stage liver disease. There has been a small group of patients who have gotten neural cells transplanted into their brain. About 10 people have gotten pig islets in Sweden. And in about half of these cases so far - and within the next few months all of them - will have been tested for the presence of endogenous virus and other pig contaminants. And so far the half that have been tested have been consistently negative. So I think that no one can say there is no risk. I said earlier, there is a risk. However, the level of risk - based on what we know and are rapidly learning - is low.

MCDONALD (CBC): But how do you determine where that level is?

BACH: You can't determine where that level is really. An you know, the problem is, everything Dan says is correct, but we do not know when such a disease would manifest in the patients, and we certainly don't know when it would manifest in the general population. If this is the kind of disease which does not manifest for 20 years we may not have an outbreak for 20 years.

MCDONALD (CBC): Now, there is another issue that comes up here besides the risk, and this is the public acceptance. I mean, some people would find the whole concept of harvesting animals for their organs objectionable. How do you respond to that?

BACH: That is a part of the ethics. I mean, there are people who are desperately concerned with the whole concept of crossing the species barrier, of doing something in the medical profession that contradicts, almost, or it certainly invades what has been evolution over millennia and longer.

SALOMON: I think the issues here are potentially getting confused. What we are talking about on one hand is the nobility of public discussion. I think it's great. I started off by saying it's the critical duty of all of us in medicine and science to foster, participate in public discussion. What we are talking abut now is an official call for a moratorium on the early trials required to move this field forward. That is the part that I think is irresponsible.

The issue here is that everything that we do in medicine is fraught with risks. We need to put this into the context. Human transplantation, which is going on every day, has got all kinds of infectious risks. We've transmitted AIDS virus, Hepatitis B, Hepatitis C, Epstein-Barr virus - which causes, by the way, tumours, particularly in children. Cytomegalo virus, which has killed patients. We have transmitted all kinds of things with human/human transplantation. In fact, in some ways the public has to understand that by using pig donors, with high screening and ability to have complete control over the donor population, we could, ironically, reduce the risks. So we accept risks in medicine everyday. In every field. And so to blow xenotransplantation risks out of proportion, as a way of preventing the early clinical trials to forward, is wrong.

Now let me make one last additional point here. We have to move some of these trials forward into clinical practice in order to answer the very questions Dr. Bach is proposing to answer. The animal models and their ability to predict this risk that we keep hearing about, are extremely limited. A quick example is the idea that these pig viruses can jump to humans. Well, now that we're doing some more work, it's turning out that the pig viruses don't jump to monkeys very well, so a lot of these monkey models of pig organs into monkey - which everyone was all excited about -might be a model for human risk probably are going to turn out not to be predictive. So some of this is going to have to be worked out in humans.

BACH: It is not quite right to say that everything we do in medicine is fraught with risk. It is fraught with risk most of the time to the patient only. Now, allo-transplantation, the kind of transplantation we do now, does have the other risk. But, in fact, we don't know what's out there in xeno. And xeno is an unknown thing, and I come back that ethically we should involve the public. If we didn't do it with allo-transplantation enough that doesn't mean we shouldn't do it now. We should have them decide how they react to this whole thing.

SALOMON: Just not forget a key point here. Starting a small group of very highly regulated, very public trials in xenotransplantation doesn't do anything to restrict this noble process of further public education and ethical discussion.

MCDONALD (CBC): There is another element involved, and that is the commercial interest. This could become big business. How is that involved in this whole process?

BACH: It's very deeply involved. I don't think we could have moved forward in xenotransplantation as much as we have without the participation of both large pharmaceutical companies and small biotech companies. They have supported it. They are doing their own work on it, and you're quite right, the estimate of Solomon Brothers is that this could be a $6 billion a year industry by the year 2010 based on some assumptions that they made. There is also the other effect, that one of the people at the FDA meeting got up and said: if we have a moratorium then I, speaking for a small biotech company, will not be able to continue working, because my investors will just pull the money from us. So something which involves public ethical questions unfortunately also involves these very real issues for the biotechnology companies that have been working.

MCDONALD (CBC): We heard earlier in the program from Jeff Getty, who received an experimental bone marrow transplant from a baboon. He says that the experience was well worth it for him; that it was worth taking that risk. What's your response to that?

BACH: He was a man who was dying, and who is doing very well now for reasons that I don't think any of us understand because that bone marrow never took, it never really started to function as we think of it when we transplant bone marrows. And that is wonderful. And for the individual, I think most of them, if it's a chance to save their lives, and everybody is equally concerned about that, delivering health care to people who are in desperate need, that is not the issue for the moratorium. The issue for the moratorium is that it puts people who have no say in the matter at risk, and that is where my co-authors and I felt we needed to bring them in.

MCDONALD (CBC): Dr. Salomon, last word to you.

SALOMON: Well, this is the point where obviously Dr. Bach and part ways. Perhaps dramatically. Dr. Bach made a point earlier that it might take 50 years - I think that was the number he gave - to find out that if these risks are real. I made a point that the animal models and certainly the in vitro cell/cell culture models are extremely limited and therefore there are increasing doubts on many of us as scientists that they truly will predict any of these kind of risks. Moreover, even if they did - and I just said they don't - you're talking about putting the pig kidney in the monkey and let him live for 30 years and then we're still 20 years short of Dr. Bach's criteria.

BACH: Wait, Dan, I've got to interrupt you. This is not at all what I'm saying.

SALOMON: Well, that's what I heard, and that's...

BACH: No.

SALOMON: And the point here is, right at this moment it is important for us to move forward in a limited way with clinical trials in xenotransplantation in order to determine the future of this field. It may work, it won't necessarily work. And certainly it'll never work if we don't move it forward.

BACH: The issue is it may take 20 years for infection to manifest, but the review process, under this moratorium, should take no where near that length of time. It should take very little time to let the public ...

SALOMON: The big problem here has been that the idea is noble, but the outcome parameters for this public discussion don't exist.

BACH: Then we disagree.

SALOMON: You want to have a national vote.

BACH: No no no.

SALOMON: You want to have a consensus.

BACH: No no no.

SALOMON: You just want to have a bunch of people talking to each other and they'll feel better.

BACH: (Laughs)...

MCDONALD (CBC): Well, gentlemen, obviously this is a topic for great discussion. Thank you both for giving us your time.

BACH: Right, thank you.

SALOMON: Thank you.

BACH: Bye bye.



MCDONALD (CBC): Dr. Fritz Bach is a xeno-transplantation researcher at Harvard Medical School; and Dr. Daniel Salomon is a transplant physician and scientist at the Scripp's Research Institute near San Diego. Late in January the Food and Drug Administration in the United States gave the go-ahead for limited clinical trials of xeno-transplants. Here at home, Health Canada is considering requests for experiments involving animal tissue transplants on a case by case basis. The Canadian government is in the process of developing a xeno-transplant policy and will soon be asking for feedback from the public. Our final words on this subject today go to Jeff Getty, the recipient of the baboon marrow transplant. From his perspective, one of the key issues is our acceptance of people who may cross the species boundary.

JEFF GETTY: What I'm hearing is that they are not quite ready yet to have humans part animal and vice versa. And that... we're talking about the myth of ... like centaurs, or something mythological from ancient times. Something very deep rooted. But we must remember that there was similar concerns around all of this - early allo transplantation and bone marrow transplantation - that wouldn't we take on the attributes of our donor. If, for example, a criminal donated bone marrow to a priest, wouldn't the priest then become a criminal? I think we just are all going to have to get used to this, but I'm worried that those deep-rooted feelings are actually tainting the debate to magnify and over-emphasize the risk of disease, and that that's really covering up a much deeper concern, that we are going to somehow create a new species of animal-humans.


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