Host – Dan Keller
Hello, and welcome to Episode Eighty-one of Multiple Sclerosis Discovery, the podcast of the MS Discovery Forum. I’m Dan Keller.
The science of pharmacogenomics can help identify those genetic variants that are associated with a high or low risk for experiencing an adverse drug reaction or a beneficial therapeutic response. While at the ECTRIMS conference in Barcelona last fall, I spoke with Kaarina Kowalec, a postdoctoral fellow in the Pharmacoepidemiology in MS research group at the University of British Columbia in Vancouver, Canada. We discussed the potential for using pharmacogenomics to optimize the risk/benefit profile in a patient's favor, focusing first on the risk of liver injury with interferon-beta.
Interviewer – Dan Keller
How are you using pharmacogenomics to assess the risk for interferon-beta-induced liver injury?
Interviewee – Kaarina Kowalec
Yes, essentially we have two groups of patients. We have ones that have had the drug reaction and then the other ones that have been exposed to the same drug, but do not have the drug reaction. And so we take a saliva sample from all of them, and then we’re basically looking for genetic markers that would either increase or decrease the risk of having the drug reaction. And so by recruiting all these patients, we can use their saliva or their DNA to study whether or not they have some kind of genetic variant or genetic marker that would protect them from having the drug reaction.
Are you doing genome-wide association studies or looking for specific markers?
Yes, we’re doing two-fold actually. So the first one is a candidate gene study. So this is looking at a more targeted approach to looking for genes that, based on previous literature, would be likely to be involved in the mechanism of predisposing to liver injury from interferon. So either this is related to interferon the way that it’s degraded in the body, the response towards interferon is regulated, or it can be related to the liver toxicity side. So there’s a lot of other studies that have been done looking at the genetic basis of liver toxicity from, say, flucloxacillin, amoxicillin clavulanates, a few other thrombin inhibitors, and some other cancer therapies. And so from that information we can look at those genes in our cohort. So that’s sort of the targeted approach.
And then secondly, we’re doing more of a hypothesis-free type of approach, which is a general genome-wide association study. So this is where you look at every gene in the human genome, so over 20,000 genes. In each gene, you would look at, say, a few different markers within each gene. So we have a total of 1.7 million different markers that we’re looking at to see if they modify the risk of experiencing liver toxicity.
Are you also doing the basic investigation, essentially heat maps, to see what genes are induced or suppressed when interferon is given?
No, so that would be, I guess, more microarray or gene expression. I think that would be sort of the next stage. If we could isolate one gene that would be involved, then we could I think then look at the expression of the gene, because, of course, that would be also important to see if interferon has any direct effect on turning on or turning off or reducing or increasing the level of a certain gene. But that would be probably for the next project, I think.
Are you trying to develop a risk assessment model?
Yes, so essentially kind of like a test. So it would be once a new patient would come into clinic and, say, they were going to start one of the interferons, we could take their clinical and demographic information, like whether or not they were female, whether or not they were within a certain age group, whether or not they drinked, whether or not they took different concomitant medications; and then, as well, take a spit sample from them. And then, hopefully, within a few hours or a day or so we could tell them whether or not they would fit into a low risk or a high risk of having the drug reactions. So then the clinical decision by the neurologist or the nurses could then decide what medications they should go on. Of course, if they were in the low risk category, put them on that drug. And then if they were in the high risk, then maybe suggest something else, or still go on the medication and maybe just have more blood work done to monitor them a little more closely.
Where does this stand? Developing a model is a long process. Has it started yet?
We’re in the discovery phase, so I’m going to be presenting the discovery phase where we’re initially trying to find the markers. And so we’ll finish this up within the next few months, and then the validation phase, which is basically where we would want to replicate these findings in an independent international cohort. So we have another cohort of patients that are from the US, as from Europe. That will probably take about a year or so. And then from there you could maybe implement it into the clinic, but likely the goal with looking at interferon-induced liver injury might be that we would use this information to study drug reaction with the newer medications. Because the new oral medications come into being used more, interferon might be used less, and so this just might provide some pilot work, I guess, for some of the newer oral medications.
Will all this focus always on liver, or are there other toxicities that you would look at?
There’s definitely quite a few areas that I would want to look at. One, of course, is probably in the mind of most clinicians and patients as well would be PML or progressive multifocal leukoencephalopathy with natalizumab and then also with some of the newer medications as well. That would be probably the one, you know, stands out in most people’s mind that would be the likely area to study to see if we can reduce the incidence of that type of more severe drug reaction for sure. Some of the new medications definitely suppress the levels of white blood cells quite a bit, but that still kind of also ties in with PML. Mitoxantrone is not used quite as much, but it’s got a limited amount of use, because it’s associated with not only leukemia but also with inducing heart toxicity. That’s another area that would be frightening, obviously, for a lot of people. But I think those would be sort of how you could kind of round out what areas would be next likely drug reactions that would be needed to be studied.
Do these kinds of investigations require networks of collaborating centers or databases?
One center definitely can’t do it all. In order to get the number of cases that you need of the drug reaction, you probably get maybe 5 to 10 per center, and so you probably need somewhere in the range of 60 to 100. And so what we did was, because of the really strong network that we have in Canada of the Canadian MS Clinics, we use that, as well as we capitalized on another drug reaction surveillance network called the Canadian Pharmacogenomics Network for Drug Safety. Using those two different networks, we were able to recruit enough patients to form our discovery cohort. And then for the replication cohort, we used some of our connections in the US and then abroad. But definitely it’s a multicenter type of study, for sure.
Can these sorts of models be used also for predicting who will respond best to a drug, not only worst? Some drugs are taken from the market, because you get adverse reactions, but they work for some people who don’t have adverse reactions, and that’s a loss.
Yes, it’s definitely unfortunate, and even in the case of natalizumab, where it was taken off market because of PML, there were obviously patients who were so passionate about having this drug available to them that they were able to get that decision reversed and just released on a more stringent, I guess, criteria. I’ve never heard of a drug being put back on the market because of pharmacogenetic findings or because someone was able to find a marker that would prevent people from having a drug reaction. I think that, for example, the FDA or Health Canada or any of the European agencies I don’t believe that they would feel comfortable enough with letting a drug back out there knowing that, even if they found some kind of genetic marker.
Two drugs, ximelagatran (7:17) and one other cancer therapy, they were taken off the market because of liver toxicity concerns. And what’s interesting is that it was about a similar incidence as what interferon-beta-induced liver injury was. But, of course, with MS there wasn’t many medications, so that’s probably why interferon was probably allowed to stay on the market. But those drugs were taken off the market, and then they found some genetic markers, but they weren’t quite as strong, I guess, as they were hoping. And so it was not going to work as a predictive risk model or as a predictive genetic test, so they weren’t going to be allowed back on the market.
But I think the ideal time to look at these types of genetic markers would be probably in some of the final stages of, say, clinical trial testing. And maybe pharmaceutical companies might be doing this, I’m not sure, but to look at these types of genetic markers in those stages would be really beneficial, because if you see them as they’re developing them, you could offer them as kind of like a companion diagnostic type of test, so whenever they would release the drug. Usually these drug reactions don’t actually occur until you’ve treated probably ten to fifteen thousand people, so that’s the other difficulty. So maybe another stage would be to just do sort of like an active surveillance to sort of recruit patients as they’re on the drug and just monitor all of them. But, of course, that takes a lot of money and takes a lot of time, so you need the funding for that type of study.
This would be like a Phase 4 post-marketing study.
Yes, exactly. And they do that, right. They do a lot of active surveillance for drug reactions whenever a new drug comes onto market. But to actually develop some kind of predictive biomarker test at the same time, is not really done pretty readily, at least to my knowledge. So it would be great, because if you see how much money goes into developing every drug, you know, and if we want to keep it on the market, then maybe that’s what you have to do.
People are developing in vitro liver assays. I guess that’s an early stage sort of thing before they go through a whole development process.
Yes, exactly. And that will definitely help as our technology certainly gets a lot better in the future, and we can study the liver much more readily, especially in people with MS. Just studying MS as a disease on its own is really difficult, and so studying the liver is very low down the list. And so we don’t even know really if MS affects the liver on its own, so that could be another entire study.
Anything important to add?
You know, I really hope that we eventually get to a day where patients can take a drug that’s really effective. We’re definitely getting there. We’re definitely getting drugs that are more effective, but at the caveat that they definitely are more toxic. That’s definitely unfortunate, because the patients are scared, right? These side effects are fatal sometimes and are really very worrisome.
And I can give one anecdotal experience that I had with a patient that experienced liver injury from interferon. And I’ve certainly had a lot of people that didn’t really believe that this drug reaction was all that important sometimes to study. And I met this one patient that experienced it, and she said, you know, I’m not really worried about this drug reaction itself. It’s just I don’t know what has happened to my liver. I know this one instance is over, but now for the rest of my life, I’m scared of every drink that I have or every time I want to take an acetaminophen pill for a headache or a fever or whatnot. If they don’t have to worry about one additional thing, you know, they’re already worried about how MS is going to affect their life. If we can maybe eliminate something like this, it’ll help some patients.
Very good, thank you.
Thank you for listening to Episode Eighty-one 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.