CME Slides Forum - R.J. Quigg

A joint Congress by ERA-EDTA and ISN

COMPLEMENT COMPONENTS IN MEMBRANOUS NEPHROPATHY

Richard J. Quigg, Hinsdale, USA

Chair: Dontscho Kerjaschki, Vienna, Austria

Claudio Ponticelli, Milan, Italy

quigg

Prof. Richard J. Quigg
Section of Nephrology
University of Chicago
Chicago, IL, USA

That’s my title, that’s me. So, all I was given was a title and the time to show up and the rest was up to me I suppose.

So this is what I want to cover and it’s a bit of like multiple courses I suppose and absolutely I will touch on something that I think is an important thing to take away from at least what I can tell you. So I’ll go over some data from animals and a little bit of human stuff relating to why we feel the --- up here you know why Professor Ronco matter of factly said that it’s complement dependent disease. I mean I have invested interest in that and I’m not positive that that’s true. Because of the renaissance in some of the genetics and even animal studies that affect diseases that we as nephrologists deal with that aren’t directly membranous nephropathy but still are very illuminating, I want to touch on those, so that’ll be MGPN II you see it has a membranous so I feel justified and atypical haemolytic uremic syndrome. Then I will talk about disease-modifying biologicals that target the complement system. The reason is there are a lot of them.

Just like you know think back say 10 years ago with TNF or IL-1, I mean TNF has got what like 4, 5, 6 inhibitors now that you have to deal with or maybe next door where the rheumatologists are but they’re common, these are coming down the pipe and we as nephrologists if this is a complement-dependent disease, then we ought to know about this.

I will talk particularly about eculizumab because in the US we can buy it and use it and I’ll show you how it’s being used beyond PNH.
I’ll touch on this. I pray that Dick Glassock will maybe help about should we use these biologicals in our patients with membranous and if so, in what type of patient?

So I’m a complement expert, I’m a nephrologist. I deal with glomerular disease models in patients. Why complement in membranous nephropathy? Well I mean professor Ronco started it and this is not as nice a picture as his but you know the glomeruli are packed with immune deposits that they’re immunoglobulin and complement components, period. So that’s circumstantial evidence at least that it’s involved. You know I think probably it’s true it comes out in the urine perhaps in greater amounts than in nephrotics. There’s a kind of confounding aspect of complement activation on the tubular cells which I think it’s interesting. We may hear a little bit about that later.

So the dreaded complement slide, I actually start complicated I’m going to kind of reduce this down but if you basically believe what professor Ronco said that it’s a C5b-9-mediated disease and the antibody starts things, well it goes down this long pathway and it’s kind of like the more you know the less you know. There are factoids that help in the scheme and factoids that don’t. One of the bad ones is that IgG4 is predominantly found in these deposits and it doesn’t do anything with C1q. So it can activate the classical pathway of complement. I’ll talk about this and I’m going to simplify it a bit as I go along, so you don’t fall asleep.

So there are two studies that I love and in all apologies to Professor Kerjaschki these are from my mentor Dave Salant and Bill Couser back when I was just about getting into the lab. This is 1980. The beautiful thing about the next two studies that were published in JCI is that the entire study can be explained simply and this is the passive Heymann nephritis model of membranous nephropathy on which we based it, it’s the Holy Grail really and it’s a very simple model and the name is descriptive. There’s passive administration of an antibody, in this case it’s a heterologous antibody so it’s made in a species other than a rat. So in this case it’s sheep that binds to the kidney. So there are simply two groups in this study; one group was given saline as a control, the other one was given cobra venom factor which depletes complement. You can see actually that the C3 levels were depleted to very low in the cobra venom factor treated group and there was probably like an acute phase response in the Heymann nephritis animals. There were equivalent amounts of antibody because they both got anti-Fx1A and you know, Steele Belok was the guy who started all these studies and then he went to Israel and kind of got lost from sight. So none of these guys thought that this was worth doing but David finished it up and sure enough complement depleting reduced proteinuria, this is normal for a rat. You know this is an incredible study, it’s why I’m standing here to be honest with you.

6 years later this next study was done by Andrey Cybulsky in David’s lab and it’s a model of Heymann nephritis again and it’s actually nicely shown. Basically these are the fresh immune deposits, it’s 3 days prior that the animal, the rat was given anti-Fx1A. Now the trick here is that then the kidney was taken out and put into an isolated perfused kidney apparatus and Andrey was always kind of gruff when he was doing this because it’s a technical challenge but basically the isolated perfused kidney apparatus allows one to perfuse with whatever kind of plasma you want and it’s all free that was the trick.

So back then if the kidney, which had these immune deposits, was perfused with normal human serum, there was massive proteinuria and Helmut Rennke actually read these CMs and said, well the podocytes have gone and we had a patient who was C8 deficient who willingly let us plasmpherese him for money and if the kidneys instead were perfused with C8 deficient plasma, there was absolutely no proteinuria above baseline and the morphology was totally normal and if it was reconstituted with a source of C8, there was massive epithelial cell injury. This is what 23 years now? This may seem matter of fact but back then it was almost harassing because the thought was that in membranous and in experimental membranous we had just missed the inflammatory cells. If it’s complement, then it’s going to because of these anaphyl toxins and no one ever really thought about C5b-9 as being that relevant but this really showed it because if there’s no C8, the only thing that C8 can really do, the only thing it does is to make C5b-9. So this is really an important study and it set forward a lot of the work of Doncho when Bill Cowser moved out to Seattle and a whole lot of work from people like Patty Backer. So that’s kind of the premise for why we collectively think complement is relevant.
So I’m just going to switch gears just a bit because there’s a circulatory to what I’m going to try and talk about, so bear with me.

So MPGN II very rare, Patrick Walker would have us call it dense deposit disease and I think that’s going to happen. It’s a rare disease but I think most people in the audience will know of it and certainly the dense deposits.

The reason why I bring it up is because there’s another complement protein factor H, complement factor H that is very relevant to it. I love this molecule, it has kind of restored my faith in the complement system to the extent you care but it’s a boring molecule in so far as it’s basically just as if it was beads on a string. It’s like a necklace of 20 beads, they’re all pretty much the same. They’re short consensus repeats but it does an amazing job, it has no other domains other than these short consensus repeats but what it does with those is pretty dramatic. It basically has ligand binding ability for the complement proteins, as well as C-reactive protein which is actually pretty relevant in certain inflammatory diseases and also can stick to --- endothelial cells.

So factor H, now I’ve colour coded this a little bit differently. Why I’ve colour coded it is to make it clear what the effectors are because I think that’s really important when talking about the complement system because there are a lot of proteins, this isn’t interleukins I think there are 85 or something interleukins. There are only 9 complement proteins plus a few other letters but it’s in numeric order other than up here but you can see that there are not that many effectors. There are the C3 and C5 proteins and also C5b-9. What’s in blue is where factor H regulates this pathway and you can see it’s got a strangle hold on the whole thing because the complement system bottlenecks at C3 and C5 and because factor H has affinity for C3 it basically strangles the whole pathway and that’s why it’s a very effective regulator.

This just shows the relevance is that complement regulation is critical and that it occurs on the cells surface, it occurs in the fluid phase and it’s an interesting process and partly it’s because C3 is constantly activated. We need to have something to inactivate it, so actually this is very interesting.

The structure of C3 is known and I just drew this cartoon up because we are in 200, the structure of this protein is known all the domains, some like factor H, it’s got a whole bunch of different ones but when it’s activated, it’s extremely cool and actually there’s a model of this in real time but this thing it’s like it bends over and it attaches covalently anywhere, any carbohydrate, any amino group. These little tethers are what can be inactivated by factor I with factor H as a co-factor releasing the C3c and just leaving this little C3d.

So this inactivation is critical and it occurs both in the fluid phase and on the cell surface. As you know, the association now with not just factor H but also hyper functional factor B, dysfunctional membrane co-factor protein or CD46 are all associated with a typical HUS and in some regards dense deposit disease.

So, when talking about inhibiting the complement system and I think that that’s what all the remainder of my talk is going to deal with is you know, if a disease is truly complement-dependent, how do we inhibit it? So this is just another kind of colour coded view of the complement system that lists the regulators, the natural regulators in colour next to them. Finally, after I don’t know how many years I finally tried to simplify things and to think about what is it that we’re really trying to do? And what we’re really trying to do is affect these effectors. I mean these are really the things that do the damage from the complement system. So C3b is bound covalently to a surface. It binds the complement receptors 1-4. The anaphyl toxins cleaved off of C3 or C3a and off of C5 or C5a. They bind their cognate G protein coupled receptors and C5b-9 binds to the membrane and the colour code just shows you the enzymes are C1r, C1s, C2. These are all serine esterases. C2 the MASP, CfD, CfB they are actually quite related. So really the inhibition can occur anywhere here but the downstream effects need to be considered as well as the negatives.

So just like with say TNF inhibitors and IL inhibitors whenever you mess with the immune system, there’s the problem with either autoimmunity like happens with TNF inhibitors and infections and that’s certainly the case with the complement system. It is an important limb of the innate immune system.

So just to go back here. You know these things are coming down the pipe. For us it’s like what will we pick, what will we use? Ideally there are controlled studies for this. I’ll just talk about one that did have a controlled study and that’s the answer to the gentleman’s question previously. What about C5? What about eculizumab that now we can get? I could treat a patient tomorrow if I wanted to, maybe Wednesday. It blocks C5 and so it’s taking out these proteins. It’s leaving these alone and you know the main issues are infectious complications.

It’s simply an antibody that was raised to human C5, so it’s a mouse antibody that is then humanised so all the domains that are not relevant to antigen binding are swapped out to be human. It doesn’t mean there’s not going to be an alloimmune response to it because it’s not totally autologous. It is available.

It is FDA approved for PNH, a disease that is due to the lack of the GPI, the glycosylphosphatidylinositol linked to the red cell membrane. It’s a clonal disorder but affecting CD59 --- main complement regulators but it’s not cheap. Of course, I think I think as physicians we say look you know drastic measures call for drastic measures for HUS.

But it didn’t surprise me that there is a letter out from Germany and Austria about the use of eculizumab in atypical HUS. I’m not sure if it would have been my first line therapy knowing what I know about the disease but who can argue a success, you know HUS is a consumptive thrombocytopenia with a haemolytic anaemia so haptoglobins are undetectable. The platelets went up and the renal function got better, haptaglobin went up as haemolysis. So are we blind? To this it’s like amazingly not. There was a study I was involved in and it was a multicentre study that looked at eculizumab, it wasn’t eculizumab but it was close enough. It was their version of it at the time. To give the company credit it had its good design parts.

So there were 122 patients with idiopathic membranous, they were studied in a randomised double blind placebo controlled study. As is the case with most membranous studies the outcome is proteinuria as primary variable. Unfortunately, there was no difference among groups after 16 weeks of treatment.

When I first saw the study design, I was like ‘oh my god I can’t believe it’s going to be that short because this is a disease that lasts years’. I think even some of the longer studies have criticisms of ‘gee was that long enough?’ I will say and it’s all I can say I had two patients that were really wickedly nephrotic. One was on placebo, one got 8 doses. The company allowed 1 year of open-labelled drug use and I swear to god both patients completely remitted. Now, whether that’s just luck or whether it’s the drug I don’t know I’m just telling you the way I see it. So we’re kind of stuck.

In the interest of time I was wondering whether I’d get to this just to say this is from my friend Steve Tomlinson with whom we’ve worked upon targeting complement inhibitors but just to say another thing in the pipeline is targeting complement. Targeting anything, the oncologists use it all the time, we should and it actually works. A beautiful study. So the concept is basically to target a complement inhibitor which is Crry in this with anything, it could be an antibody which I’ve done before, or with CR2 which is complement receptor 2 or CD21 that binds to C3d and it really worked nicely in the lupus mouse model. As I said, the more you know, the less you know.

The podocyte and the local area around it is a very interesting area and there are a lot of immune events going on. I think to say that the kidney’s kind of passive is not fair. It’s a very active organ and I’m impressed with that.

So in summary, the complement system is clearly relevant in rare diseases that face us such as dense deposit disease and atypical haemolytic uremic syndrome. There are considerable data to support the relevance of complement in membranous nephropathy and becoming available are complement inhibitors targeting specific portions of the complement activating pathway or pathways.

Unfortunately, a well-performed but with design flaws randomized controlled study with anti-C5, Eculizumab, in membranous nephropathy was negative. So, even though Eculizumab is very expensive, the option of its off-label use in idiopathic membranous nephropathy, plus anything, maybe lupus nephritis which is another story all together, is a consideration for prudent physicians faced with high-risk in troublesome patients. With that I’ll end.

Question: I ask you a question. Is there any good evidence that factor H may be transiently decreased in membranous nephropathy and in this case is it due to autoantibodies or to partial deficiency of factor H?

Prof. Quigg: I always had a hard time figuring out how factor H got across the membrane because it’s like a hot dog. Although the stuff that Peter -- shows that it’s not like an omega so I suppose it can squeeze through. I honestly think that the intrinsic cellular complement regulators are very important in all cells. I think the endothelium and the fluid phase plasma relies on factor H quite a bit. I don’t think that other cells besides endothelia rely on factor H so much. I think they must have their own complement of complement regulators if you will. So I’m not that hot on factor H.

Question: Just one more question. How was the drug tolerated? What about side effects?

Prof. Quigg: Oh the side effects. Well of eculizumab, I alluded to infection. I had a side bar with Dick Glassock before this talk and there was one patient in that study who got a meningococcus. That’s the clear issue and all patients have throat swabs for Nyceria Meningitis and if they are entering the study, they get immunised. I think that what happened with their study is they were interested in doing it better, doing it right but they were concerned and the PNH stuff was coming out. This is kind of drug company posturing at this point. They were concerned about 3 patients in the PNH literature and the PMNH studies that got meningococcus and I think perhaps to have it marketed for something and then to have off-label use but as far as I’m aware the main complication is going to be infection and not just anything it’s the Nycerial bacteria. C5b-9 is big for them.