Host – Dan Keller
Hello, and welcome to Episode Eighty of Multiple Sclerosis Discovery, the podcast of the MS Discovery Forum. I’m Dan Keller.
Interferon beta is a well-known and long used treatment for relapsing-remitting MS, but it's not without potential problems for some patients. While at the ECTRIMS conference in Barcelona last fall, I spoke with Kaarina Kowalec, a post-doctoral fellow in the Division of Neurology at the University of British Columbia in Vancouver, Canada. We discussed interferon beta and other drugs and their potential for liver toxicity.
Interviewer – Dan Keller
In terms of liver toxicity of interferon beta, what's the problem?
Interviewee – Kaarina Kowalec
I would say that about 1 in 50 patients that are exposed to this drug will experience a side effect known as drug-induced liver injury, or liver toxicity, essentially; it's an abnormality in their blood work. Most times it'll just go back down to normal and everything is fine, but in the rare occurrence sometimes it can lead to more severe outcomes such as needing a liver transplant, sometimes even liver failure, and sometimes even death. That's definitely a very rare scenario, but it certainly is an issue, and it's definitely a worry for some patients and definitely for clinicians, as well.
Also, it's not only interferon, a lot of drugs have liver effects. Is that right, new drugs especially?
It's the number one reason that drugs are taken off the market, and it's usually one of the top concerns for any new drug that's entering into the market. Obviously, the liver has many different functions, but one being that it detoxify foreign components like drugs like interferon, like alcohol, food, many different things. So it definitely plays a major role, that's why it's usually effected so much.
What are some of the factors that affect both efficacy and toxicity of drugs in general?
You know, if you see it kind of a pie chart, the genetic component can be pretty variable. So from person to person, it could be anywhere from a few percent to up to 50 to 60%. But the rest of that pie, I guess, is made up of variation in how much of an enzyme we make that needs to detoxify the drug, as well as our age, our BMI—how much we weigh—how tall we are, whether or not we're male or female. There's a variety of different demographic-type factors that come into play, as well. It's definitely very difficult to predict who will have a safe and effective response to a drug.
Does polypharmacy play a role, especially you had mentioned enzymes; things that induce or suppress enzymes?
Yeah, definitely. So in the case of an interferon, there's some evidence to suggest that interferon might suppress some of the cytochrome, or drug-metabolizing enzymes. And in that case if they were taking any additional medications, such as like Tylenol (acetaminophen) or ibuprofen, that could create an issue because interferon is inhibiting the enzymes that are necessary to detoxify the acetaminophen, then obviously the body might have trouble with just acetaminophen on its own.
All interferon betas, do they vary in their effects?
Yes. The versions that people with MS get as a drug therapy, there is a few different variations. So I guess half of them are made in a Chinese hamster ovary cell line, and then the other half are made in an E. coli cell line. So there are differences in the immunogenicity of those two forms, so the ones that are made in the animal cell lines are more similar to the version that we would all make endogenously, whereas the versions that are made in the E. coli cell lines are different, they're slightly more immunogenic. They're just more foreign than what we would normally make.
Is it a difference in amino acid sequence, or glycosylation, or both?
Yeah, exactly. So the amino acid sequence is slightly different for the E. coli cell line versions, as well as the E. coli version is not glycosylated. So, again, that's why it's a little bit different than the human version.
Do you know some of the mechanisms by which interferon betas cause liver injury?
So how it causes liver injury exactly is certainly unknown, and that's definitely an area of which I'm trying to figure out. There's two sort of competing theories, I guess. One is that interferon, because we make it endogenously, but this version is obviously still different than the version we make, it might be that obviously in MS they have an aberrant immune system; they could be recognizing the interferon as being a foreign agent and its attacking it, and then some of the cytokines that are released might be targeting the liver. So that's one theory. The other theory is that once interferon is incorporated into the cell, it might have some sort of direct effect on the mitochondria, and so it might be that it's reducing the energy metabolism of the cell and causing harm into the liver. But which of those two, we're not sure yet.
Do you know risk factors for liver injury, and as they are picked up by aminotransferase elevations?
Yes. And some of the risk factors that we know for interferon-induced liver injury are related to gender, age. Sometimes it's polypharmacy, so whether or not they're taking acetaminophen or ibuprofen. One study will come out that'll say that there is an effect, one study comes out there's no effect, so it's still a little bit unclear. With gender, we know that for males they are more likely to have some of the more minor transient elevations in the aminotransferases, whereas females are more likely to be at risk for the more severe symptomatic hepatitis, or liver injury, I guess.
And is it equally prevalent, or there's different gender prevalences?
I would say that overall when we looked at all the genders together, it was about the same, about 1 in 50, or 2% or so. I would say that if you're looking at just severe injury, the effect that's more symptomatic, something that a patient would actually notice, it's likely that females are more susceptible.
What about duration of treatment, does that have an effect; early, late, how long?
Yeah, typically it's quite quick that they would experience this. So the median time is about the first 3 months is the greatest risk period—I guess probably 3 to 6 months – but it certainly can still occur later on, say even 2 to 5 years, or even 7 years later on, so that's why it's still really necessary to remain diligent on testing their liver aminotransferase levels even later on, even like I said, 5 to 7 years after being on treatment. The effect doesn't seem to go away, for some people anyways.
I suppose while you're taking it you're getting older, and also you probably have different medications coming in and out.
Yeah, and it's not even just the other pharmaceutical therapies that you're taking, it could also be your diet, how much you exercise. There's a lot of things that can affect the liver aminotransferases, unfortunately, so sometimes it can be difficult to determine whether or not it's actually interferon beta that's the causative agent.
What should patients be looking for?
You know, I think just staying up with a healthy lifestyle; not drinking excessively, eating the right foods, making sure that whatever therapies that you are taking are compatible with interferon. Your neurologist or your clinician will advise you on those areas anyways, and also keeping an open dialog with your neurologist in that you know exactly what the risks are with taking any medication. And most times your clinician will be able to tell you everything that'll be possible side effects, so just keeping an open dialog with the clinicians, I think, is great.
Are there symptoms which might raise concern?
You know, I mean sort of the typical things that we think of with liver issues, like jaundice, abdominal pain—they're really like, I mean, abdominal pain that can be a symptom from many different things, right? Malaise, same thing. Really I would say jaundice is probably one of the things that would stick out in my mind to most people as having an issue with your liver, right? By the time you notice symptoms, it certainly is in the more severe end, so usually you have something else that would precede that, like the abnormal blood work. So most people don't get to that stage, which is good.
Is there something physicians should be doing or looking out for?
No, I would say they're doing a really great job with just monitoring the blood work. They know that once typically patients get to 5 times the upper limit of normal for ALT, or the liver aminotransferase, that's when it's recommended that they stop the drug. So normally because they are tested quite often for the blood work abnormalities, the clinicians are really going to go about monitoring by lowering the dose of the drug or just stopping them, and then slowly titrating them back on again. They still have many options if they experience the side effects, so they're doing a great job with monitoring.
Is this becoming less of a problem with new drugs, vis-à-vis, interferon beta itself?
I believe almost all of the new oral medications have all had some case reports of having liver injury associated with them, which is unfortunate. But, again, like I said, most drugs will use the liver in order to be detoxified, it's not, I guess, surprising that this is happening. So I think that we definitely need to study the theory. And that's sort of why we're studying interferon beta, because there's so many people that have taken it, there's enough people that we can study, whereas the new medications, they haven't reached sort of that level yet; they don't have 20 years of data yet. So that's why interferon beta really represents a really great way to study this type of side effect, because now hopefully maybe some of these findings we can apply to the new medications that are going to be more relevant in the future.
Have you been able to see whether a history of interferon beta affects susceptibility to liver injury with any of the newer drugs?
I've seen a few patients that have had liver toxicity from interferon, and then gone on to take, say, glatiramer, and they have had that same reaction, or Copaxone. Individual clinic, they've seen it, but they just haven't had many publications on that, so it's sort of unclear, I guess, right now. I guess I should still say in the wider literature in other liver toxicity from, say, like antibiotics, there are some common mechanisms. It seems like that some people, that if they have it to one drug, they have it to multiple drugs. So there could be some underlying, I guess, common mechanisms between all of them.
It would be hard to separate out whether it's a function of the patient being susceptible liver to liver injury from almost anything, versus having a history specifically of beta-interferon.
Yeah, we don't know the long-term effects of interferon beta, we don't know really what happens to them in the long run. We can only really follow the ones that have had the really severe outcomes, like liver transplant, for example. But people that experience the more minor elevations, or even the level that we study, most often we see that the liver enzymes go back down to normal. But, you know, we're only looking at this for maybe 5 to 7 years, and then after that we don't know what happens. And then, of course, then once they get older, you would expect that things might go downhill and they might have more issues.
Have we missed anything important?
This is an area that with respect to toxicity with the MS medications, it's definitely an area that is not as well studied, because, of course, the overall goal is to have an effective treatment. If we have an effective and safe treatment, that's the end goal, but that's not always what happens, because we can't sort of have everything that we really need. And so I think studying these areas is definitely really important, because although patients want their disability to be prevented, they're willing to take a lot of risk. And they shouldn't have to, they should be able to have an effective treatment that is safe, as well. So I think by studying these adverse drug reactions more often, I think we'll hopefully get to that end goal eventually.
Very good, thank you.
Thank you for listening to Episode Eighty of Multiple Sclerosis Discovery. This podcast was produced by the MS Discovery Forum, MSDF, the premier source of independent news and information on MS research. MSDF’s executive editor is Carol Cruzan Morton. Msdiscovery.org is part of the nonprofit Accelerated Cure Project for Multiple Sclerosis. Robert McBurney is our President and CEO, and Hollie Schmidt is Vice President of Scientific Operations.
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For Multiple Sclerosis Discovery, I'm Dan Keller.