Munir Pirmohamed: Thank you very much for the invitation.
So I’m talking to you as an academic in the UK, which is still part of Europe, just
to out --
[laughter]
-- but also as somebody who works with the International Serious Adverse Event Consortium.
So what I do is, as an academic, I direct the MRC Centre for Drug Safety Sciences.
For those of you who do not know, the MRC is the equivalent of the NIH in the U.S.,
except we have much less money --
[laughter]
-- of course, but we haven't been stopped from giving coffee to people.
[laughter]
So if you come to see us, we will give you some coffee.
[laughter]
This is -- this is the mission of the MRC Centre for Drug Safety Science, to really
undertake leading-edge science, train the next generation of drug safety scientists,
understand the mechanisms of the type of serious adverse drug reactions we’re looking at
today, and to develop strategies to improve the benefit to risk ratio of current new medicines.
That means developing diagnostic tests, predictive tests, but also using the chemistry of the
drug to be able to design new, safer drugs, as was suggested earlier on.
So we work with academics, other healthcare groups, plus also industry, and other types
of organizations.
And that was why we started working with the SAEC.
The SAEC, set up by Arthur Holden -- the mission is shown there, which very much aligns with
what we do with MRC Centre for Drug Safety Sciences; that is identify DNA variants useful
in understanding the risk of drug-induced serious adverse events.
That’s the iSAEC’s mission.
Now, the SAEC has been looking at various different phenotypes: serious cutaneous adverse
drug reactions, drug-induced liver injury, and also recently started the drug-induced
renal injury.
The important aspect over there is that because there are different patients being recruited
to all these different phenotypes, one can actually start looking across the phenotypes
to see where there are common genetic factors, so that common genetic factors, which leads
to skin versus liver with the same drug, and that is going to be very important as the
work of the SAEC, in terms of undertaking all the genome studies comes to fruition in
the next year or two.
Also within the same particular group, for example, within the serious cutaneous adverse
reactions, then you can -- we also have different phenotypes.
So I have been leading this serious cutaneous adverse reactions, but we called it ITCH --
[laughter]
-- International Consortium on Drug Hypersensitivity, for obvious reasons.
And this is what we have managed to do -- have 12 international centers, 50 UK centers, and
over the last four years have collected 1500 patients.
This includes Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis, but also DRESS, but
also some AGEP cases, but also we've been interested in type one hypersensitivity reactions:
anaphylaxis, where there’s been immunological testing done, and all of these cases are collected
to a specific phenotypic criteria, but also we have an independent adjudication of these
cases.
And Dr. Neil Shear, sitting in the front, and Peter Friedman [spelled phonetically]
in the UK are two dermatologists well known in this area, I think you are well known,
aren't you Neil?
[laughter]
So -- who then undertake the adjudication.
And they spend many hours on the telephone with us undertaking the adjudication after
having received the case reports.
So in terms of the SJS/TEN, so the data I'm going to show you is unpublished, and I'm
not going to show you some of the specific alleles that we've identified, largely because
we need to validate those alleles in some replication sets apart from the end case study
I'm going to show you.
But these are the SJS/TEN cases that we've collected in terms of the different drugs
the patients were exposed to.
And it includes many different ethnic groups, but if you just look at the Caucasian cases,
what we have are mainly northern European population, but also a Spanish and Italian
population, and if you look at the sort of clustering there, you can see that the clustering
all those Caucasian populations from Europe in association with the controls they've utilized
within the GWAS studies.
So the question that we've been asking is are there any drug-specific associations you
can identify, which is what everybody else is doing, but also, are there any disease-specific
associations we could identify.
You could hypothesize that the disease association with SJS/TEN in respect to the drug is probably
there but is going to be a much lower effect size, as in a complex disease, and therefore
you are going to need a much larger number of cases, for example, as in diet type II
diabetes.
And these are data which have just come out.
Now this is -- this is data which still needs further work on it, but what we're finding
when we actually look at all SJS -- Caucasian SJS cases, is that there is something appearing
in the H allele area, and it is very low-frequency HLA-B allele, but also in chromosome eight,
we’re finding a protein kinase.
Now we do need to validate this, but it is -- it is nevertheless interesting to be able
to show you that.
Now I don’t know whether this is -- not drug specific at the moment because there
are certain drugs which are appearing, but there are many other drugs also in their which
are showing the same allele in there, which is interesting.
Now when we actually start then stratifying by the different self-report ethnic groups,
we find that this is mostly driven by Italian SJS/TEN cases, with 40 cases, and the HLA-B
allele, which is a rare allele, is appearing with an odds ratio of 133, with the 95 percent
confidence intervals, as shown, and a P value, as you can see there.
And then when we actually exclude the Italian cases and look at the northern Europeans,
and then look at the Spanish populations, there is no other population-specific signal
appearing.
So it has been driven by the Italian cases and that is why it is also important to look
at this ethnicity when you do these kind of analysis.
But again, we need to be able to do further work whether it has been driven by one particular
drug or a couple of drugs in that population.
Now, in terms of drug-specific associations, we are -- obviously there are associations
we’re finding which were already well-known.
For example, with the Allopurinol, there are only nine cases -- Caucasian cases -- we are
beginning to see again 58 to one associated with Allopurinol.
But then there are other drug-specific studies we have done.
I only have time to show you one particular example to show you, and that's with trimethoprim/sulfamethoxazole.
Again, 17 SJS cases, again 500 -- 5000 controls.
We're finding some genome-wide associations with a nice stack on the Manhattan plots,
as you can see, on chromosome three, chromosome six, 13, and also on 20 and 21 and 22.
And again, these need to be looked at in more detail and validated or replicated in other
populations and what we need to do is now find some replication cases.
And obviously when you are looking at something that rare, it is important to be able to collaborate
globally to be able to identify new cases so you can replicate.
These could still be positives, despite the fact -- these could still be false positives,
despite the fact that they are above genome-wide significance.
And so, just to give an example of how we tried to do this with Nevirapine in an African
population, we undertook a prospective study in Malawi, where we identified individuals
prospectively who had had some degree of hypersensitivity, as either maculopapular erythematous eruption,
DRESS, SJS/TEN, or drug-induced liver injury, undertook GWAS studies, but also been undertaking
some proteomic studies -- and I don't have time to be able to show you that.
But although our mission has been to identify predictive biomarkers, what we are also interested
in looking at prognostic and diagnostic biomarkers.
And we’ll be looking at this particular protein called HMGB1, high mobility group
box protein one, where you can look at the total levels which mature by an Eliza test,
but much more important is to actually look at the isoforms that stratify -- which stratify
populations according to both mechanism and release [unintelligible] status of HMGB1,
but also functioning, in terms of radoc [spelled phonetically] status, and there's some very
interesting data which are coming out with HMGB1.
So here's the sort of in just an SJS/TEN, 51 SJS/TEN patients and 182 torrent controls
and only, so far, association that we get is on HLA-C.
We’ve undertaken sequence-based typing, and we see that this is HLA-C*0401, associated
here with the Nevirapine.
And obviously, what we wanted to do from this was to go and replicate it, so we started
identifying cases, again in African population, some in Malawi, but also some in Uganda and
some in Mozambique.
And when you put it all together and do -- for this particular hit -- RS hit which is RS
number up there you find it is genome by significance with an odds ratio of 5.17.
Now, so we think that the HLA-C*0401 in the African population does increase the risk
of SJS/TEN in that African population.
So what we want to go on to do is to undertake sequence-based -- next-gen sequencing of these
particular HLA region in a subset of patients with SJS/TEN, and what we identify is that
there is a non-synonymous variant -- which is incomplete LD with the RS number I showed
you before -- so this is incomplete LD, and this non-synonymous variant leads to an amino
acid substitution which is present in the alpha-1 subunit of the peptide recognition
site of HLA-C*0401.
And we're just undertaking some molecular docking studies to see how Nevirapine or potentially
its metabolites might be able to fit in there and how they lead to the SJS/TEN.
Although we've talked about the parent drug being responsible, it is also important to
note that metabolism may still be important.
And this is done in such patients whereby we've been actually looking at whether patients
bio-activate Nevirapine to toxic metabolites, and we've done that with various other drugs
by looking at whether there is binding going on to human serum albumin and using a mass
spectrometric methods.
And you can see that Nevirapine does form adepts in patients who have taken Nevirapine
chronically and the binding occurs, particularly on histidine 146 and the [unintelligible]
molecule.
So that just gives you a flavor of the work that's been going on with the SAEC.
So I think SAEC is a private-public partnership that has worked well and has written managed
to recruit well phenotype patients, genome-wide approaches, and is now beginning to bear fruit,
and there will be much more coming out.
We're furthest ahead with type I hypersensitivity reactions and we've got some very interesting
hits coming up, hopefully going to be published in the near future.
Global corroboration I think is very important to be able to further some of these findings,
but I think, although we are looking in genomic data mostly and that's where we’re mostly
looked at today, I think it is important to identify diagnostic and prognostic biomarkers.
And some acknowledgments there to -- and to many others who are not mentioned on this
slide.
Thank you for your attention.
[applause]
Steven Katz: We have time for a couple questions.
Yes?
Female Speaker: So I may have missed this, and I'm sorry if
I did, but in the Italian SJS/TEN, did you say what B allele that was?
Munir Pirmohamed: I didn't, because we need to validate it.
Female Speaker: Okay.
Munir Pirmohamed: It's a rare variant.
Rare, rarely occurring at less than 2 percent.
Female Speaker: In Italians?
Munir Pirmohamed: In Italians.
Female Speaker: Thank you.
Male Speaker: Are there common alleles for -- that cross
over from SJS to some of the other skin reactions which are more common or more frequent where
you -- where the defining of this equilibrium or defining the signal would actually also
imply that SJS could also be included?
That is -- or are these allele markers always specific for the particular disease?
You mentioned one slide where you actually pull different kinds of skin reactions.
So I was wondering whether you found certain markers which actually cross over to different
kinds of serious reactions.
Munir Pirmohamed: So I -- that is further work that needs to
be done, and with 1502 and Flucloxacillin -- sorry 5701 and Flucloxacillin, we've not
only identified with liver injury, but we're also identifying some patients with 57-1 who
have type I reactions: anaphylaxis, as well as AGEP as well.
So there is some crossover between alleles and their current or different phenotypes,
but with 1502 and Carbamazepine, that does seem to be very specific for SJS/TEN.
So I think it does vary with drug and the kind of phenotypes you're looking at.
So I don't think there is a one specific rule for everything, and certainly with -- if you
look at 5801, with the Allopurinol, there is an association with SJS/TEN, but also with
DRESS as well.
Male Speaker: So if you were developing a drug and you saw
a signal, let's say, with even maculopapular erythema, and would you -- would that be for
you a cause of concern for this particular disease or usually not?
Given the point, the problem that powering is what is so --
Munir Pirmohamed: Sure.
Male Speaker: -- challenging for this disease, I mean, really
a lot of post-market exposure before you really see something.
Munir Pirmohamed: Yeah.
I guess your question is does maculopapular erythema act as a kind of signal for the currents
of more severe reactions and whether the same HLA association.
The problem is that there's not enough been done on the maculopapular exanthems and the
genome-wide association studies, and part of the problem there also is the causality
assessment, because getting a maculopapular exanthem may be not entirely drug-related.
There may be other factors there, and the causality association is much more difficult
to assess in maculopapular exanthem than it is in SJS/TEN.
Steven Katz: We can have two more short questions, and
two more short answers.
Male Speaker: How much of your case finding has been amenable
to structured queries of electronic health record data as opposed to manual?
Munir Pirmohamed: All of this was manual.
I did do some work on electronic health records.
I looked at the phenotype, and I won't tell you which country it was; I won't tell you
which particular provider it was, but I did 150 records and not one of them fit in with
the criteria that we had.
Steven Katz: David?
David Marcos: Hi.
David Marcus, University of Pennsylvania.
When you’re grouping people as Italian and Spanish and English, is it all based on the
location of origin or is it genetic ancestral markers, or self-reported ancestry --
Munir Pirmohamed: Okay.
So when we’re classing them as Italian, Spanish, et cetera, it’s self-reported ethnicity,
including the grandparental background.
However, what we have also done is obviously, the GWAS, we've done some population stratification
analysis, and I showed you that data in terms of the plots on there, and those are of northern
Europeans, Spanish, and Italians, according to the principle components analysis.
Male Speaker: Okay.
Steven Katz: Thank you very much.
Interesting acronym you picked, since itching doesn't come along with Stevens-Johnson or
TEN, at least in my limited experience.
[laugher]
Now, we're going to hear from Thailand, Dr. Chantratita from the -- from the Ramathibodi
Hospital in Mahidol, the University in Thailand.
[end of transcript]