Episode 22: Advancing Research and Novel Therapies for C3G

What does the future of treatment for C3 Glomerulopathy (C3G) look like?

Dr. Nicole van de Kar (Radboud University Medical Center, The Netherlands) unpacks the pathophysiology of C3G, from genetic and autoantibody factors to the central role of the alternative pathway. She explores the limits of current C5 therapies and the potential of new strategies targeting C3 activation that could reshape patient care worldwide.

This episode is part of a four-part KDIGO Conversations in Nephrology series on complement-mediated kidney diseases, hosted by Dr. Carla Nester (University of Iowa Stead Family Children’s Hospital, United States).

This series was supported by Apellis and Sobi.

Episode Transcript

(00:01):
Welcome to KD GO Conversations in Nephrology.
This episode in our complement mediated kidney disease series
titled Advancing Research and Novel therapies for C3G is
provided by KD Go and supported by Apellis and Sobi.
Here's your host, Doctor Carla Nester.

(00:21):
Hello and welcome to K Deagle Conversations in Nephrology.
I'm Doctor Carlin Nester, professor of internal medicine
and Pediatrics, Stead Family Children's Hospital, University
of Iowa, and joining me to discuss advancing research and
novel therapies for C3G is Doctor Nicole Vandekar.
Dr. Vandekar is a pediatric nephologist at Rabud University

(00:44):
Medical Center 9 Megan, the Netherlands and her clinical and
research interests include thrombotic microangiopathy and
the complement mediated kidney diseases.
Dr. Vandekar, welcome to this podcast.
Thank you, Doctor Nestor, it's apleasure to be in this podcast.
Let's begin our discussion todaywith the first question.

(01:05):
Let's start with your view of what the next decade as compared
to the last decade of course in therapeutics will look like in
the treatment of C3G. Well, thank you for this
question. I think this will be really
exciting decade which you are going into because now we can
make diagnosed by kidney biopsy and C3G and we have already

(01:26):
supported the therapy which we know as far as blockades and low
salt diet. And we have already four years
the immune suppressive treatments as Prednisone an MMF.
But that is all non targeted treatment and you can read all
these protocols in the Kadigo guidelines for example.
But what is now intriguing is that we have now the first time

(01:47):
targeted treatment available forC3 gene and that's because of
those two new drugs which have now entered and then they ended
almost at clinical trials. And then for the first time we
have a targeted therapy which will talk the overactive
complement alternative pathway. As we know and we heard before,
this is the drug fiber of the disease.
So this next decades having these complement aminipeties

(02:09):
available for the treatment willbe exciting.
And I think it will lead to lesschronic renal damage, less end
stage kidney failure and hope for those C3G patients who need
a kidney transplant and hope fora better future for all C3
patients. So I think this next decade will
be really promising. I think you're exactly right.
This idea of targeted therapeutics for the first time

(02:31):
in our lives in this set of diseases is amazing.
A small question and and I don'twant that you to have to think
about too hard, but do you thinkthere are going to be issues
about how to use them? For instance, are you going to
consider primary therapy or are you going to consider whether
you have to do XY or Z first? I think for us as conditions, it
will be very important to draft good protocol when to use these

(02:54):
new drugs, for whom, on which conditions and how to follow
them up and how to monitoring them.
Because in the trials the patients were not mostly primary
having the disease for only a couple of weeks or months.
Some were already having them for years and entered the trial.
So I think there will be definitely people who can use it
in the first weeks of the disease, but then really well

(03:15):
guided by protocols, I guess it would be the criteria to use
for. Yeah, I think that's an
excellent approach, this idea ofdeveloping protocols.
So then the next question, whichis a little bit unfair, you
know, because obviously neither one of us are pharmaceutical
people. But when designing these trials,
you know, for these agents, what's your impression of how
the sponsors decided upon the endpoints that they decided

(03:38):
upon? Well, I was not involved
designing the clinical trials, but I participated as you as
well in an international workinggroup organized by the Kidney
Health Initiative in 2021 to address the challenges needed to
say what do we need from this trials and what outcome do we
need and what are the best endpoints.

(03:58):
And we had a lot of discussions in working groups and it went
back and forth and we came actually at the end we came up
with three endpoints which mightfor C3G might be value valuable.
And those are also endpoints yousee in the trials.
And for me I think the most important one is proteinuria.
It's a risk marker for disease progression across various

(04:18):
glomerular disorders. So not only C3G and we know that
large treatment effects on proteinuria are believed to
predict treatment effects on disease progression.
If you then look at C3G, then wehave not that much data in time
how patients are doing on the treatments.
But we see that from cohorts in the United Kingdom and also from
Iowa that if, if we can reduce the proteinuria and if you can

(04:41):
reduce 50% or even more, I thinkthen it will at the end will
benefit also your EGFR, so your kidney function and it will at
the end will be of health for your kidney function.
The problem is for proteinuria that it's not really an end
point which is much used in clinical studies.
So is it then good, Is it a bad end point?
I think it's the best we have atthe moment and I think you would

(05:03):
expect an effect at six months at least.
So for that, I think it will be a good endpoint and the best we
have at the moment. Of course, if you ask in our
group as clinicians, we also know that proteinuria can be
difficult because we are aware that of course if you have
sclerotic regions in your kidney, you also have
proteinuria. And together with declining
kidney function, we know that this is different proteinuria,

(05:25):
this is proteinuria because of fibrosis.
And so this will always be an issue having proteinuria as an
endpoint. But I think looking at
creatinine function, at kidney function and looking probably
also at Histology, it might help.
So this I think proteinuria is agood one.
And next we have the EGFR. We discussed it as well in our
working group. And of course, you would expect

(05:47):
if the inflammation in your kidney caused by the overactive
compromise activation will decline by using these drugs,
you could imagine that your kidney function will in time
improve and the slope of your EGFR will then get less steep.
So your kidney function will improve.
We don't have data retrospectively data to see what

(06:07):
would be the best follow up time.
But I think also here six months, it's fair to mention
that you probably would not needa very deterioration of your
EGFR. Because if that's the case, if
your EGFR is derivating of goingbadly with the new drugs, you
might wonder if something is wrong and you have to rethink
again. So that's very important I

(06:29):
think. And then you have the Histology.
It's a rare disease and you onlydo your biopsy if you think
really it's needed. So we don't know what we have to
expect in kidney biopsies. You might think the new
complement blockers inhibit C3 activation.
So there might be a reduction inC3 deposits in the kidney and
you might think in time you willbe seeing that in US pathology.

(06:50):
But that means that you have to re biopsy patients again.
And I think this is something which we really need to think of
if we want to do it and what we want to see.
So I think what we see in the trials is that they looked at
histopathology and had that was mostly the secondary endpoint
and they had for example, they had an histological activity

(07:11):
index. But in this score there's also a
necrosis or fibrosis been mentioning.
So we have to define what do we want to see in histopathology,
which could improve the kidney health and probably the deposits
is one of the most important things, but less fibrosis if
there's already something there would be benefit as well.

(07:32):
Yeah, I think all of your pointsare very important.
I think we weren't as fortunate as, for instance, IGA to have
that proteinuria as already a selected surrogate endpoint for
our regulatory agencies. And when you think about the
GFR, you can't wait, you know, the years it takes for the GFR
to decline enough for you to getto dialysis, right.
So you have to think about, you know, what measure of the GFR

(07:55):
are you going to pay attention to?
And you kind of already brought run up the important part
because one of my questions was going to be if you rely on
Histology, which certainly the animal models would have
supported that if you stop the alternative or if you block the
alternative pathway that maybe the Histology goes away.
That means you have to go back to rebiopsy 2 small questions
about and they're actually not small questions, but so you've

(08:16):
already told me you would rebiopsy.
Are your patients in general going to agree that that's OK?
I think I would rebiopsy if I don't see enough improvement in
proteinuria or if I hardly see any improvement in proteinuria.
And I would also rebiopsy if I see the kidney function is
declining. This is really for me a must to

(08:37):
biopsy because it has consequences.
If everything is going well, then you might wonder are we
going to biopsy? And this is a difficult point
because we should in the ideal world if biopsies would not do
any harm, if it would be easy doing it, I think it would be
good to do because we could see what the effect is in time of
these new drugs on the histopathology.

(08:59):
But that might be difficult to get patients and also conditions
into re biopsy when things are going well.
Yeah, I think you're exactly right.
But you also make the point thatwe need the real world
experience to help us solve someof these issues.
So perhaps you can share a briefoverview of the clinical trial
results in general. I know some of that, like you've

(09:19):
said has been published and someof them are are waiting for
publication. But if you wanted to share just
a little capsule of that for ourlisteners.
Well, it already started a couple of years ago with I think
the first international trial oncomplement blockade in C3G was
the Avacupan trial and it was a phase two trial.
Avakopan, we know now because it's now implemented in
anchovasculitis treatment, but it's an oral blocker of the C5A

(09:43):
receptor blocking the effect of C5A and it was thought it might
have a role in C3G and it was designed really good, I mean
double-blind placebo-controlled.And the endpoint was that we
come to Histology. Again, the endpoint was an an
improvement in histological activity at six months of using

(10:04):
the product and this endpoint was not achieved.
I mean there was no significant difference between avacopon and
placebo, although there was reduction in proteinuria by
those who were treated by Avacopon in comparison with
those with placebo. But this trial did not made it
further on. And then we had I think mostly
at the same time actually there was a trial also a multicentral

(10:25):
international trial on the Nicopon and that's a small
molecule inhibitor of the complement factor D of the also
of the alternative pathway. I mean not also because Avacupon
is targeting the terminal pathway but the Nicopon is more
upstream and that Nicopon is cleaving factor being it
prevents cleavage of factor B and therefore it reduces the C3

(10:47):
confratase formation which is seen as the culprit of C3G.
And this trial was a phase two trial also double-blind,
placebo-controlled but the efficacy was found to be
limited. It was probably failing
achievement in complement inhibition and although there
were some patients showing a decline in proteinuria, I think

(11:07):
it was not showing good results.So it was stopped.
So and then I think where we allhave been waiting for and would
we see those results of two phase three trials of complement
inhibitors targeting at the level of C3.
So at the C3 confratase, those are the iptacupon and the
pexitacupon and both trials havereached down the occlusion rate

(11:28):
of patients and they are finalized or getting finalized
and are almost ready or far ready to publish their results.
And I think Iptacopan for example, an oral factor B
inhibitor selectively blocks theformation of the C3 comfortase
of the alternative pathway. This phase three trial has been
performed in adults and this is now already the drug which is

(11:50):
registered because of the results by the FDA and the EMA
in the treatment of C3G in adults.
And we have to await for the adolescence trial which is still
going on, but already very far ahead for their results.
So then we have Pexitacopun, it's AC three blocker activation
level of C3 and this drug actually acts at C3 and

(12:12):
therefore acts on all three complement pathways including
the alternative pathway. And that is a drug you need to
give subcutaneously twice weekly.
And for this, this phase three trial is in adolescence and in
adults. So they combine it and it's in
C3G, but they have also primary immune complex MPGN and they

(12:32):
have also included patients who are known with C3G and but have
already a renal transplants. And actually those drugs have
already shown good results as you're probably aware of.
And I think the design was for both trials was they all had a
six months, so 26 weeks or placebo or drug and then after

(12:55):
26 weeks all got the drug. And I think the results have
been published for the first sixmonths of both drugs.
Yeah, so thank you for that overview.
If you are just tuning in, you're listening to the K Deagle
podcast on advancing research and novel therapies in C3G.
I'm Doctor Carla Nester and I'm speaking with Professor Nicole

(13:15):
Vandekar, Pediatric Nephrology 9.
Megan, so I'm going to ask you and and I might be able to guess
since you're a pediatric nephrologist, can you share with
us some of the distinguishing features between the studies
that end up being important given what kind of patients
you're approaching? Well, I think what they did in
both studies, I think the trial design was at quite some

(13:37):
similarities. Adolescents need to be above 12
years. So we don't have data on below
12 years. And you and I know that we see
children which are younger than 12 years as well.
They all wanted to have an active disease.
They all wanted to EGFR above 30ML per minute.
They all want to have more than 1g per gram proteinuria and 24

(14:00):
hours or in first morning urine,so more than 1g per gram.
So that makes it you already have an exclusion of patients
who have less than this 1g or don't have the age of 12.
You need the mandatory vaccination.
I think that's very, very important.
We are aware of that for the other diseases, Atos and PNH

(14:20):
that you need vaccinations against the menococcal
primococcal bacteria and hemophilus influenza.
So that was all in both, all of them.
So that was one thing and I think the exclusive criteria
were almost all the same as well.
So you were excluded if you had more than 50% sclerosis in your
kidney biopsy secondary forms ofC3G, so mostly post infectious

(14:43):
and the monoclonal gammopathy were excluded.
And you need to not have to havean exposure to other complement
inhibitors, but you were allowedto have ACE or AOP inhibition or
SLG 2. These were adults we're not
allowed to use in Europe for children.
And you, you were allowed to have Prednisone or
corticosteroids and MMF, but youneed to be on a stable regimen

(15:03):
for those drugs. So those were actually having
somehow the same results, the same inclusion or exclusion
criteria. But of course, the way of action
is different. One attacks factor B, the other
attacks C3 itacupon orally, back, sitacupon subcutaneously.
And that means that you have already have some differences

(15:25):
between those drugs. If we look at the results, I
mean the results for both studies look good.
Iptocopon at a 35% reduction in proteinuria, change in
proteinuria compared to the baseline and versus the placebo,
it had a stabilization on the EGFR in 12 months.
So that's very good. The pepsitopon where C3G and

(15:46):
immune complex MPGN is included showed a reduction from 67%
reduction in proteinuria compared to the baseline as
compared to placebo. And they could show a small
improvement on EGFR at six months.
And they had already looked at more biopsies than Iptacopon at
this time and they could show inless staining or in a lot of 0

(16:09):
staining or C3G in kidney biopsies.
So both drugs do really work as it looks on the complement over
activation we found in C3 glomeropathy.
So that's very good. Thank you.
That's a very good representation of the trials.
And I agree, you know they both work very well.
I'm curious and I recognize we don't have data for this, but
you mentioned they both requireda 1g of urine protein, somewhat

(16:34):
like the IGA world these days. Do you think once we get to real
world we'll be interested in using it before a gram or do you
think most of us will stick to the gram?
Depends. I think if you have a new
patients and it's above the 1G, I think always you start with
ACE or OP and probably you will get already quite some patients
having reduced Putinorium even maybe even below 0.5g a day.

(16:59):
And then becomes the questions and are we going to give those
then already immediately a complement inhibition?
Are we doing it instead of Prednisone and MMF, which is at
the moment standard therapy or we add first with the ACE and
the ARP, we add Prednisone and MMF and together with complement
inhibition. So I think this is really stuff

(17:20):
to have good thinking about about what we are going to do.
It's also, I mean those drugs are cost lots of money and if we
want to have it available for a good treatment in our C3D
patients, probably we should notuse those complement inhibition
drugs in those who have less than 1.5g a day and maybe even
not with 1G. We should start with Azinarp and

(17:43):
see what comes out and then progress with maybe Prednisone
and MMF. But I know there are also
colleagues who would like and love to start with the
complement inhibition by the way.
But depends if attacking of the over activated complement system
would be enough in the first weeks of your disease.
If there is such an inflammationalready there which is broader

(18:06):
than only the over activation ofthe complement, should we then
still need immune suppressive drugs for example for a short
while? What would be the best protocol?
I think you're exactly right. I think at the end of the day,
we still have some thinking to do on this.
We still have to figure out, youknow, is attacking inflammation
critical? Is targeting the complement
system critical, Is targeting the protein critical or even for

(18:26):
that matter the CKD aspects. As you've kind of indicated,
there's a number of supportive cares.
So the final point on that mightbe that will the standard of
care change? I mean, we know what has been
set by KD GO currently we have to decide what happens next,
don't we? And more to come, I'm sure.
But then maybe one of the final questions I'll have for you is
that if you could pick one or two or maybe just a very few,

(18:47):
what are the biggest challenges you think that we're going to
face? And we started this discussion
about what's the next decade look like?
Well, what's the next decade look like when it comes to
challenges in this setting? I think I want to play out for
all the clinicians treating patients with C3G.
Unite yourself to gain more dataon C3 patients and that

(19:08):
treatment, whatever treatment itis, I mean if it's ACE, if it's
AAP, if it's Prednisone corticides and we really need
good well thought of treatment protocols.
We have to collaborate with eachother to make those protocols.
And I think there are initiativealready going on, which I really
encourage and I really think they're very important.
And we really have to work together on an international way

(19:31):
to make this collaborative databases because then we can
see what the landscape looks like and what the drugs will do.
I clearly think that the standard treatment care will
change for C3G and complement inhibition will find its place
somewhere in those protocols as well.
But then we'll be very that likewe discussed when to start,
which complement inhibitor use, is there a moment to stop?

(19:54):
Can we stop? Do we have to treat those with
auto antibodies against the C3 convertase, Do they need the
same treatment as those with genetic variation for example?
And I'm very curious can we get complete remission in all C3G
treated patients with complementinhibition for example.
And this is more important challenges for us as conditions

(20:15):
we have clearly have to monitoring the efficacy I think
as well and the side effects. And that's what I told earlier,
if you don't see a benefit, let's say in 3-6 months of your
therapy, the thing we consider maybe you need to rebiopsy
again, you mean to think if thisdrug is effective enough.
And also if you think of complement inhibition in a long

(20:37):
time, is it safe in your growingchild in an adolescent?
I still don't know. I mean we have just started with
AIDS book age of course on B&H and we are still figuring out
and I think we are very lucky and for seeing these results of
this new therapies. But it doesn't change anything
on the presence of the auto antibodies against the C3
comprotase. So at the over activation of the

(20:59):
complement system, we can act with those blockers, but we can
do not do anything on those autoantibodies.
So that might be a challenge forfuture trials maybe in
combination with complement inhibition to see if we can get
rid of this and to auto antibodies as well.
Some will disappear by themselves in time, but some
will stay there for a long time and will continue to over

(21:22):
activate the complement system and possibly ongoing C3
glamopathy. So I think, well, it's really an
interesting decade which we are going into as clinicians and as
patients, but promising, very promising.
That's exciting. Even hearing you talk, it gets
very exciting. So what I hear you say is for
one thing that's going to be important is this idea of global

(21:42):
teamwork, this idea of all of uscollaborating to get the answers
that we need. But also, I think you make a
very good point of, you know, just surveillance of what
happens and what do we need to do next.
So those are all fantastic points, and I thank you very
much for identifying all of those challenges.
We are about to wrap up. So before we wrap up completely,
Doctor Vandekar, I thought I would ask you very quickly, do

(22:04):
you have any final messages thatyou want to share with us?
Perhaps you've said most of them, but if you have a few that
you'd like to add, please do. I think if you, those who are
listening have patients with C3Gin your practice and you're
looking, clearly you're looking out for this new, promising new
treatment options. But please try to contact your
colleagues in expertise centre or reach out to other colleagues

(22:25):
who treat CTJ patients and try to do it in a protocoled way,
whatever protocol, but make one and stick to that or look for
it. And then I think make sure that
your patients is somewhere in a national, international database
because we have to learn from now on how to use these
treatments and this learning hasjust begun.
Yeah, I think that's an excellent message.

(22:46):
So thank you, Doctor Vandekar, for joining me for this session.
It was really great having you here, and you clearly have a
number of wonderful insights into what this new decade will
look like for us. Thank you for joining us.
Thank you, It was a pleasure. Thank you for having me.
I'm Doctor Carla Nester, To access this and other episodes
in our series, visit kdgo.org/podcast.

(23:11):
Thank you for listening.