So I'm going to start the program off with talking about the limitations of current antiviral therapy with nucleoside-nucleotide analogs.

 

[00:32:31]

 

Global Deaths From Viral Hepatitis Exceeds HIV Infection, Tuberculosis, or Malaria

 

Now, everyone here at this meeting, in this room, and online knows that viral hepatitis is an important global health problem. And I think this data is really compelling.

 

My colleague at Johns Hopkins, David Thomas, assembled this. And it really looks at mortality from viral hepatitis, combining B and C, compared to some really major infectious disease killers, including TB, HIV, and malaria. And what you'll see is it is projected that by 2040, deaths from viral hepatitis will exceed all of those combined, a major threat to public health.

 

[00:33:15]

 

WHO: Global Call for HBV Elimination

 

And not surprisingly, nearly 10 years ago, WHO called for the elimination of HBV. They said there are more than 254 million persons living with Hep B, and there are major gaps in care. 86% are unaware of their infection, have not been diagnosed, and 97% globally have not been treated.

 

Yet the ambitious goal set for 2030, which is now only 5 years away, is to eliminate viral hepatitis as a public health threat, reducing the number of new HIV infections by 90%, and reducing mortality by 65%. Very ambitious goals, and this 2030 is coming very quickly.

 

[00:34:02]

 

Patient With Active, Untreated HBV Infection

 

So I'm going to present a small case vignette.

 

A 32-year-old woman with chronic hepatitis B, HBeAg-positive, viral load is 165 million, HBsAg level is quite high, ALT is 35. We've done non-invasive testing: no liver disease.

 

[00:34:20]

 

HBV Treatment Outcomes

 

So I want to just think through as we look at treatment outcomes.

 

If we were to treat this individual, the goal would be to suppress viral DNA. Clinically, we'd also like to reduce her lifetime risk of liver fibrosis, preventing cirrhosis, hepatocellular carcinoma, and liver failure. We're going to normalize the ALT, and I'll ask you to think about it as 35, really a normal ALT for this individual. And then we want to minimize the risk of transmission to others.

 

I'm going to highlight a new section in the AASLD hep. B guidelines that address what's been known as horizontal transmission, sexual transmission, and transmission in other settings. And Dr. Feld is going to take us through quite a bit of time talking about functional cure, defined as hep. B, HBsAg loss with an individual, typically with persistence of silent cccDNA.

 

[00:35:18]

 

AASLD Guidelines: HBV Treatment Indications

 

So I mentioned the new guidelines. They have retained the more traditional focus on absolute treatment indications. So I can think of this as a continuum.

 

Everyone can be considered and should be considered for treatment. And at one end of the spectrum of continuum of care, some people require treatment, and there's not any debate about that based on the medical literature. And that is individuals with an elevated ALT, elevated DNA level, or liver disease by liver biopsy, or non-invasive testing like liver elastography or non-invasive blood tests.

 

Now, you'll note the AASLD 7 years ago defined normal for men at 35 and women at 25. So what's new? I'm not going to go through the whole guidelines. Dr. Turow did a wonderful job yesterday walking through the updates. But there were several questions asked, and one was about the so-called immune tolerant phase, HBeAg-positive, high DNA, and normal ALT. What they said was for individuals less than 40, shared clinical decision-making, sitting down with the patient, talking through their individual disease parameters.

 

So, for example, this patient is 35 really normal for her, or perhaps we would expect a lower ALT. And then this is new. Greater than 40 years old or significant liver inflammation or fibrosis, antiviral therapy is recommended. That is a new guidance from this panel.

 

They also, for the first time, talked about transmission other than mother-child transmission, the notion that this person may be worried that they could transmit hepatitis B to sexual partners or perhaps people in their household. And, yes, we stress vaccine, but not everybody is vaccinated, and there may be individuals at risk that it's unknown they're exposed to.

 

So these are 2 areas when I'm thinking about shared decision-making with that patient I'm going to think about.

 

[00:37:24]

 

Current Recommended Treatment Options for CHB: Peginterferon or NAs

 

So what am I going to use for treatment? We talked about being stuck in the status quo.

 

Well, lamivudine was approved in 1998. We're still using polymerase inhibitors. No new drug class approved since 1998. Now, yes, we have better nucleoside analogs like entecavir, better nucleotide analogs like tenofovir disoproxil fumarate and tenofovir alafenamide, but yet, they are still acting at the same place on the polymerase. We have interferon. I'm going to leave that one alone and not talk much about that.

 

So we haven't made progress. Now, this year, one of the exciting things at this year's Liver meeting is the progress that we're making.

 

[00:38:06]

 

Current NA Treatments: Mechanism of Action

 

I'm not going to walk you through the viral life cycle. I'll leave that to my colleagues, who will go in more detail. But I do want to highlight that the polymerase inhibition is occurring down here, and it's stopping the step of reverse transcription where viral RNA is reverse transcribed to viral DNA packaged into new virions and released. So it is effective at blocking DNA in the blood, but it doesn't block other issues that may be seen a bit earlier in the life cycle of this.

 

So we'll talk a bit more about this in other slides.

 

[00:38:45]

 

HBV DNA Suppression With NAs Is Incomplete in HBeAg-Positive HBV

 

So how well do these nucleoside-nucleotide analogs work? And I dug into the literature, and I went back to the entecavir registration trial, 2006.

 

Double-blind, Phase III trial, looking at HBeAg-positive patients using a DNA level of 300 copies per ml, not even the international units we're using today, and only 67% of people at 48 weeks of entecavir had achieved less than 300 copies per ml. When we look at tenofovir, there was a randomized controlled trial of tenofovir alafenamide (TAF) or tenofovir disoproxil fumarate (TDF). HBeAg-positive patients, 65% achieved suppression at less than 29 IU per ml during a 48-week treatment course.

 

So a third not getting to a suppressed viral DNA at 48 weeks.

 

[00:39:43]

 

Advancements in HBV DNA Assay Sensitivity

 

So as we look at where we're at now, we have even better assays. These studies were, in some cases, nearly 20 years old.

 

We're now using assays that are more sensitive with a lower limit of quantification of 10 IU/mL. If we reanalyze the tenofovir versus – TDF versus TAF data, you can see in the HBeAg-negative individuals, the number of people less than 10 at 48 weeks and 96 weeks remains relatively low. At 48 weeks, it's 20%, 21% or less.

 

HBeAg-positive at 48 weeks, nobody got less than 10 IU/mL. And you see that increasing as time goes on. So we do see suppression with nucs.

 

And I do want to emphasize they are our current standard of care and work well for clinical, but we're not seeing rapid suppression. So the question could be asked, does that matter that it took a long time to get negative?

 

[00:40:47]

 

Faster HBV DNA Suppression Improves Clinical Outcomes

 

Well, there are some data that really address this point.

 

In this retrospective cohort from Korea, they looked at 325 HBeAg-positive individuals, like my patient who started at 165 million, and they looked at how quickly they got to viral suppression. And you can see 1 year and 2 years. Individuals that got to viral suppression more quickly had a lower cumulative incidence of hepatocellular carcinoma than those that did not.

 

So this suggests that if you want to cut the risk of liver cancer, get the virus not detected and do it relatively quickly.

 

[00:41:26]

 

Incomplete HBV DNA Suppression Is Associated With HCC in HIV/HBV Coinfection

 

What about the effect of someone who has detectable virus? There's a really nice study done. Now, it's in people with HIV hep B. A couple things to know about that population in North America, and that's what the NA Accord stands for, it's North American cohort. Every person with HIV is recommended to be on tenofovir, with or without lamivudine or emtricitabine.

 

So they're all treated. And tenofovir treats both HIV and hep B. So, they're getting care as well. They're coming and getting lab tests. These researchers asked the question, what about liver cancer risk in this patient population? And they followed individuals over time, nearly 3,000.

 

And they found that if the HBV DNA was greater than 200, the risk of cancer was increased with an adjusted hazard ratio of 2.7. If it was above 2,000, it was 4.34. And when they looked at different combinations, there were people with HIV-negative, meaning they were taking their medications, hep B was not, and that had an adjusted hazard ratio of 1.77. So increased risk if they weren't suppressed of liver cancer. So this tells us that controlling viral replication is important.

 

[00:42:42]

 

Ongoing Global Disease Burden Despite Long-term NA Therapy

 

So it's not surprising, given that nucs are not perfect at suppressing viral replication, that there is ongoing burden of disease, even if you're taking a nuc. You can have decompensated cirrhosis, the numbers are relatively low. You can have hepatocellular carcinoma. And this is what I really worry about in my patients on nuc treatment. We are surveilling with ultrasound and AFP. And they are at risk, particularly as they grow older, of hepatocellular carcinoma. Transplant and liver-related deaths still occur.

 

And the fundamental problem is that there's low hepatitis B surface antigen loss and persistence of HBV DNA in some patients. But these drugs don't really lead to high rates of HBsAg loss. And they have other limitations.

 

[00:43:32]

 

Limitations of Current NA Treatments

 

So they clearly improve clinical outcomes. And again, I don't want to minimize the importance of these drugs. And in fact, more people need to be on them as we wait for future advances. But they do not eliminate cccDNA. They have really only a weak effect on HBsAg loss. When you follow people over time, as many of you do in your practice, it's estimated about a 1% per year on a nuc of losing HBsAg. And they really don't result in HBeAg seroconversion above the spontaneous rate.

 

So disappointing outcomes in this regard. And there's incomplete inhibition. So although they block that step of RNA to DNA, it's not turning the spigot off 100%. There's still some leakage. So given these limitations, they are suppressive therapy. And patients can remain at risk for complications.

 

[00:44:28]

 

Posttest 1: Evidence suggests that, in most people with CHB, nucleos(t)ide analogues are associated with:

 

Brings us back to the posttest question 1. I indicated we'd come back to these. So get ready to vote.

 

Evidence suggests that in most people with chronic hepatitis B, nucleos(t)ide analogs are associated with:

 

1. Control of viral replication only;
2. Control of replication plus elimination of cccDNA;
3. Control of replication and rapid suppression of HBsAg; or
4. Control of replication and HBeAg seroconversion above the spontaneous rate.

 

So go ahead and vote.

 

So great. The answer that we were discussing is really viral suppression. And at the top is the pre and the bottom is the post. So the voting, as you can see, has shifted.

 

[00:45:28]

 

So that is, I think, the right answer to this question. Looking here, nucleotide analogs, they suppress virus, but they don't eliminate cccDNA. And they have a weak effect on HBsAg loss. So A was the correct answer to this one.

 

Now, that concludes my comments in this section. We have some time for a panel discussion. So I'm going to take a seat, and we're going to ask Dr. Fell to join us on Zoom. And we're going to go through just a few points.

 

So I forgot to mention that all of you should be sending us, can send us questions. We would ask that you use the iPads at the tables in front of you. Or if you're at home, use the Zoom ability to ask questions.

 

We're happy. I've got an iPad here that will bring those questions up. So please send questions in, and we'll take those as they come.

 

[00:46:28]

 

Panel Discussion

 

So let me start. And maybe I'll ask a question to both Grace and Jordan. How often in your practice are you seeing that the nucs just aren't getting your patients – let's focus on HBeAg-positive first – not getting them fully suppressed. And how do you manage that? I'll start with Grace.

 

Dr. Grace Wong (The Chinese University of Hong Kong): Oh, thanks. Thanks, Mark. Yeah, so if you focus on patients with HBeAg-positive, I would say that maybe I can report some numbers by year.

 

The first year of nuc therapy, I think probably more than 20% or 30% not yet suppressed because they started with very high viral load. But with times go by, I think this number will change. Yeah, by 2 years, probably more than 80% will suppress. Another 15%, 20%, not yet. And times go on, maybe a few more percentage goes on. But like, for example, up to like 45 years, we still see a fraction, maybe 5% still have a low detectable level, a few hundred, yeah, so on.

 

So which, in fact, for high viral load to start with, yeah, it's a challenge among some patients that we may not really can suppress them fully, yeah.

 

Dr. Sulkowski: Great. And maybe, Jordan, I'll go to you. How are you, when you have a patient, let's say they've been on a nuc for 3 years and they're not fully suppressed, how do you manage that patient? How do you advise them? What do you tell them? And then what do you do?

 

Dr. Jordan Feld (University of Toronto): Yeah, that's a good question, Mark. I think this is always frustrating for patients, because when we start therapy, we're optimistic that we're going to get them to undetectable levels. That's what they expect to happen.

 

And I think Grace's numbers are sort of in line with our experience as well. We also treat a very large Asian population, so, similar demographic where you start with these younger HBeAg-positive patients. I think it's important to cover a few things and make sure there's no other reasons for not getting to undetectable.

 

So certainly got to talk to them about adherence, and especially in younger people, that can sometimes be a challenge. And it's probably more of an issue in the HBeAg-positive patients with higher replication that even intermittently poor adherence can lead to breakthrough. Viral resistance, fortunately, is not a major problem, especially if you're using a tenofovir-based therapy. With entecavir it's actually quite rare in people who are not lamivudine experienced. We do have some of those folks in our practice that were exposed to lamivudine in the past. And you occasionally will see primary entecavir resistance in people that start with very high levels.

 

So I think it's worth discussing those things and certainly then looking to also see if they're developing progressive liver disease, where you would think about trying to intensify therapy, which, frankly, is difficult in the current environment. But I think one of the questions for us is, what does it mean when someone's got low-level but persistently detectable HBV DNA? Is this actually leading to worsening liver outcomes?

 

I think the data you showed are concerning, and it's important to monitor these patients carefully.

 

Dr. Sulkowski: Yeah, I think that's really a good point. Well, let me ask maybe both of you, do you ever try to add, let's say they're on tenofovir or maybe they're on entecavir, do you try to add the other drug? Is that something you do in practice?

 

Dr. Wong: Yeah, maybe I go first. In fact, quite many years back then, my colleagues are back in the room, then we ran a small randomized control trial, that for those who have been put on entecavir for at least 2 years but not yet fully suppressed, we randomized them to just continue staying on entecavir versus switch to TDF by that time, it's 3 years back then. But we didn't have enough patients, so we didn't enroll, like, proud enough to compare.

 

But later on, we came across another study from Korea that, in fact, for this type of patient, we switched to tenofovir disoproxil fumarate at that time. In fact, the viral suppression, complete viral suppression, would be higher compared to stay on entecavir. So I think this is one of the options that we can consider.

 

Dr. Sulkowski: Jordan, how do you tackle that situation where you and your patient are not quite happy with where they are?

 

Dr. Feld: Yeah, I think it's a good question about whether to use 2 drugs versus 1. It's sort of tempting to do that, but I think, as you highlighted, these are both targeting the same step in the viral life cycle, inhibiting the reverse transcription step. And really pretty limited data showing that that actually has benefit.

 

I think where we've seen dual therapy being more useful is probably a slightly more rapid decline in the trial of comparing TDF plus FTC with emtricitabine versus TDF alone. We saw faster HBV DNA decline. But I think in patients with chronic HBV that are not suppressed, it's not that likely that adding a second drug is going to be effective. And it adds cost and complexity to the patient, so I'm not usually a big proponent of that.

 

Dr. Sulkowski: Yeah, and I think you highlight the point I was making on that slide with the linear arrow. We really haven't had innovations or new ways to treat hep B going back, a new target since 1998. So it really is that combining 2 drugs acting at the exact same site in the virus.

 

So that combination therapy, although studies have been done, hasn't always been very effective for some patients in that regard.

 

So we're at the end of our panel discussion time, so I'm going to thank Jordan for joining us. He will be back and talking at the third session, and we'll talk at the panel again.

 

But now I want to invite Grace to come to the podium, and she's going to talk to us about a very important topic, which is emerging HBV biomarkers. What do they mean, and how do we use them? So I'm going to turn the podium and the clicker over to Grace.

 

[00:52:14]

 

Emerging HBV Biomarkers: Why Do We Need Them?

 

Dr. Wong: Okay, thank you, Mark. Okay, once again, hi, Jordan. I hope you're feeling better now.

 

Okay, so good afternoon, ladies and gentlemen. Yeah, I think this symposium is very meaningful because we are really at the very critical time to bring HBV cure to our patients. So I think it would be nice to understand HBV biomarkers a bit more because we know this will be something very helpful for us to understand in the past natural history.

 

[00:52:40]

 

Novel Viral Markers as Surrogates for Clinically Important Endpoints

 

Now, like surrogate endpoint, patient selection, if you are going to put some of your patients on cure therapy. But I think more important, I would like to highlight that virus is important because it would be helpful to predict many things, but still, our patients are still the most important point that we need to really put into other aspects, like their risk factors, their clinical profiles, to predict something really important matters, like cancer, decompensation, and death.

 

[00:53:14]

 

HBV Life Cycle and Viral Markers

 

I have to say that hepatitis B virus is really a fascinating virus. It's so complex in terms of the life cycle. But in terms of the biomarkers, I think we can simply divide the pathway into 2 main part.

 

[00:53:27]

 

One is the replicating part, so that how fast the virus multiplying itself. So we would use a pure DNA, which we have been using for a couple decades. In more recent years, we also can measure HBV RNA. All these will reflect the replicating activities.

 

[00:53:46]

 

And other big parts would be the secretory pathway that secretory surface antigen and also other viral proteins. I think this also have raised a lot of interest in recent years, so I will go through some of these in my talk.

 

[00:54:02]

 

Low HBsAg as a Marker for Immune Activation

 

But I will first, before I dive deeper into surface antigen, I want to use this particular slide to echo Mark's patient that he just shared.

 

That most of the time, we think that viral load higher would be the worst. But for surface antigen level is somewhat different, we also need to interpret the results together with the HBeAg status. Because as Mark's patience illustrated, in fact, that particular patient, young, super high viral load, very high surface antigen level, but in fact, no fibrosis at all.

 

In fact, this type of patient would be in the immunotolerant phase. But more often in our practice, most of our patients would be HBeAg-negative. So for this type of patient, obviously, lower surface antigen would be better because this predict low risk of HCC.

 

More likely, they would be in the inactive phase as well. If you plan to stop treatment, then, also would be higher risk, higher probability of surface antigen loss or even develop unnaturally.

 

[00:55:02]

 

So which means that among patient with HBeAg-positive hepatitis B, in fact, higher the surface antigen is better. The reverse is lower the surface antigen will reflect immune pathology. While for HBeAg-negative, obviously, low surface antigen would be a nice thing.

 

[00:55:20]

 

Posttest 2: Your patient with HBeAg negative CHB has a quantitative HBsAg (qHBsAg) result of 50 IU/mL. What can you tell them about this result?

 

So now, let's have this posttest.

 

Okay, so you have this question just now, right? So I would like to give you maybe a 10 to 15 seconds to go on that. So your patients with HBeAg-negative chronic hepatitis B, and also the surface antigen is low, 50 IU/mL. So what can you tell them about this result?

 

1. Currently there's no guidance on how to interpret the less antigen level;
2. The results is only prognostic in patient with HBeAg-positive chronic hepatitis B;
3. You would like to have a confirmatory cccDNA test before you can interpret; or
4. Indicate a high probability of surface antigen zero clearance.

 

Okay, please vote. Either with your iPad or QR code. Yeah. Yeah, okay.

 

Great job. So even before that, you guys are doing great. Now it's even better. Yeah, so okay.

 

[00:56:27]

 

Yeah, correct. So, D should be the correct answer because quantitative surface antigen below 100 would indicate a high probability of spontaneous surface antigen zero clearance.

 

[00:56:42]

 

Limitations of Current Biomarkers

 

Nice. Okay, so this is a very simple slide, but I just want to highlight that, in fact, these are the markers that we check every single day in our practice. We're using this regularly. I think it's fine, yeah. But we also need to understand the limitation. For example, we check surface antigen status regularly, but most of us use the qualitative test, which means we in fact have missed a big part of the dynamic changes over time.

 

HBV DNA, yeah, a big part, yes, but many of our patients would have been put on mute, so all these patients would be well-suppressed. So I think probably for these type of patients, the only role would be whether they are taking the drugs, complying to it or not. And for ALT, I would like to highlight that just now Mark mentioned about the most updated AASLD guideline, stick to men should be using 35 and female 25.

 

Yeah, I think that reasonable, but one thing I'd like to highlight, that the units of ALT is unit per liter. It's not international units, which means that in fact there's still some lab variability, and in fact one of the factors we need to consider is what's the temperature of your assay or ALT? There would be some variation, in fact, the result also vary slightly differently.

 

So in fact, like in my lab in Hong Kong, in fact, we use a very high cutoff, 50-something for men, 40-something for females, which means that is it really a hard cutoff, 35, 25, it's really debatable.

 

[00:58:12]

 

HBsAg: Old Tool, New Purpose

 

HBV DNA vs HBsAg

 

Okay, so let's dive into this. In fact, our old friend, but, in fact, we have understand this marker a bit more in recent decades, and we know that in the past we mostly check it qualitatively, so positive for 6-month chronic hepatitis B, that's simple. But now in past decades we find that in fact the level tells us a lot of things. For example, in fact, it also correlate with the cccDNA transcription activity, so in fact it reflect what is happening inside the hepatocyte.

 

[00:58:46]

 

Quantification of HBsAg in Patients With HBV DNA <20,000 IU/mL to Predict HCC

 

This elegant study from Taiwan, which in fact tells us a lot. In fact, I think during the days of my, still being a medical student, we already know the doctrine that higher the HBV DNA level, higher the accuracy risk. I think the wonderful review cohort from Taiwan told us this, and this also, is the foundation of guidelines that HBV DNA above 2,000 IU/mL is the reason, one of the reasons why we treat our patients.

 

But in fact, about a decade ago, Dr. T.C. Zhang and his team also showed very elegantly, for the low HBV DNA part, we can further stratify them with surface antigen level. So for the very far-right end, you will see that the surface antigen level below 100 together with serum HBV DNA below 2,000 add up together, that would be really the genuine lowest risk of HCC, so the true inactive carrier. I think this would be very helpful if you really want to accurately predict the HCC risk.

 

In particular, you want to identify some patient they are really inactive, you want to refer them to your primary care setting, I think that is very reasonable.

 

[00:59:55]

 

Meta-Analysis of HBsAg Thresholds for Stopping NA Therapy

 

Another thing is the surface antigen level for stopping nucs. I have to say that in my practice, I rarely stop nucs, unless some patients, they have some reason they want to do that.

 

But I have to say that, in fact, over the last few years, many enthusiasm on this topic because some also feel that it's okay if the surface antigen is low enough, then we stop the nuc, they would be fine. I think there's quite some study focused on that. But I want to highlight that ethnicity also matters a lot because many studies from the West, they find that surface antigen below 1,000 IU/mL is something that is okay because if you stop the treatment, on one hand, even some patients can really achieve surface antigen loss. You can see the right panel would be up to 38%, and so on. And in fact, the risk of having biochemical relapse is relatively low.

 

But on the other hand, Asian is somehow different. Yeah, it's really ethnicity or original type. And we find that we probably need a much lower cutoff. Many study will support that maybe 100 IU/mL for the surface antigen level is something that we should target for.

 

So I would say that for me, probably it's the other way around. So if someone come to me and say, "Oh, I want to stop nuc," then, probably, I would check the surface antigen level. If it is still above 100, then I would say that, "Oh, please don't."

 

Stay on the treatment until it below 100, then come back to re-discuss. That's probably how to use this marker.

 

[01:01:27]

 

GOLDEN Model for Prediction of HBsAg Loss

 

I would like to share this quite updated studies that I published in Gut last year. In fact, it's Multisense Study in Mainland China. They tried to put together the zero surface antigen together with other parameters to predict, like the surface antigen loss over long-term nuc treatment. I would say that it's very clearly, they can define a model to predict, and you would see that those in favorable group, in fact, up to almost 30% of chance of losing surface antigen in 5 years’ time.

 

And the dynamic of the surface antigen would be most telling, that the red lines see very clear decline. Again, I will interpret this result, that I will focus on the blue line more. So if someone that your surface antigen remain almost the same over the years, then okay, stay on treatment because you are unlikely to lose your surface antigen.

 

[01:02:20]

 

Ultrasensitive HBsAg Can Be Used to Predict HBsAg Loss at End of Therapy More Effectively

 

In recent years, we also have another ultrasensitive surface antigen quantification. Usually, our assay will have the sensitivity of the cutoff is 0.05 IU/mL, but for this ultrasensitive one, would be 0.005 IU/mL, really sensitive. And this is helpful because we can further confirm whether this patient will be at risk of having light surface antigen or seroconversion after we start the treatment.

 

In this particular analysis, they put together a peg with or without nuc. And if this ultrasensitive surface antigen is negative, then the chance of having seroconversion would be super low. It's only 10%.

 

In comparison to the other arm that is detectable, which means their surface antigen is between 0.005 to 0.05 IU/mL, very low detectable level, but still the chance of having seroconversion is up to a third. Yeah, so if we have this ultrasensitive test, it would be even safer to tell the patient whether you will be fine after light stopping nuc and any surface antigen reversion.

 

[01:03:24]

 

HBsAg Seroclearance Is Durable

 

But I really love this study. In fact, it's led by Dr. Terry here at the back of the room. In fact, in my practice, if someone they are lucky enough to lose their surface antigen being naturally or with nucs, I usually will start by congratulating him or her that, oh, it's something that's uncommon, but you're so lucky to have that. I think this is something nice because it would be very durable, like up to 90% 5 years down the line.

 

But also, I want to highlight if it is like the patient have to put on nucs, I would not stop nuc right away. I would put the patient on nuc for another year as a consulting therapy to minimize the risk of surface antigen reversion. That's point number 1.

 

Point number 2 is, in fact, if this can happen early in their life, like before 50 years old, especially among women, then, in fact, the risk of having HCC would be very, very low. In our analysis, it's 0%. So I think this is very important. Yeah, so we want to achieve surface antigen early in our patient's life.

 

[01:04:26]

 

Key Takeaways: HBsAg Is a Key HBV Viral Marker

 

So, yeah, a very small summary about this old friend of us, the surface antigen level quantification that if it happen, it's sustained, it's good. It happen early in their life, especially among women, and the risk of HCC would be very minimal.

 

For patients with low HBV DNA level, be it 2,000-20,000, I think low surface antigen level would be very helpful to further define the low risk of HCC. So I think with this small summary, I also want to advocate we should bring surface antigen clearance functional cure to our patient in early in their life.

 

[01:05:00]

 

Other HBV Biomarkers

 

Okay, so very quickly, in other biomarkers.

 

[01:05:04]

 

HBcrAg

 

Just a couple of slide on core-related antigen or some call it CrAg. So core-related antigen, in fact, cover a few things, like HBeAg and other proteins. It also is very useful because it's related to the, again, cccDNA level, which reflect something inside the hepatocyte, the transcription, and so on.

 

[01:05:24]

 

HBcrAg Predictive Treatment Endpoints

 

So in recent years, again, quite some enthusiasm to use this to predict different endpoints, be it HBs loss, HBeAg seroconversion, and so on. And I would say among all these, probably HBeAg seroconversion is the most helpful and most accurate because the AUROC is well above 0.8, which is good. But you may also say it's kind of using the same thing predict itself because core-related antigen contain HBeAg, right? Yeah, so but at least I think it would be helpful if you want to predict particular endpoint listed here.

 

[01:05:57]

 

HBcrAg as a Marker for HCC

 

Another one would be predicting HCC. This is a study from our group that, in fact, the surface at the CrAg level among HBeAg-negative patient is predictive of HCC. All these patients have been put on nucs, so in fact, they have been well suppressed.

 

We can use HBV DNA to predict the HCC risk, but the core-related antigen level among HBeAg-negative patient would be predictive. But not exactly among HBeAg-positive patient because, in fact, a part of core-related antigen is HBeAg-positive itself, so it's not as predictive.

 

[01:06:29]

 

Limitations of qHBsAg and HBcrAg as Biomarkers

 

Okay, so I would like to have a little comparison of these 2 biomarkers, viral markers, that we can use these markers. Yeah, they are helpful, but we need to understand their limitations. So for surface antigen level, in fact, we cannot differentiate whether it's come from cccDNA or the integrated HBV DNA. And also, ultrasensitive test is good, but we may not have that.

 

And for the core-related antigen, again, the assay is not perfect at this moment, quite some false-positive, false-negative. As well, the test we have, in fact, the sensitivity is rather low. So like the study I just report last slide, the cutoff is 2.5 log, so it's quite high. Some other center can down to 2 logs, but still a lot of room of improvement, and hopefully we can have a better assay very soon.

 

[01:07:19]

 

HBV RNA

 

Again, very quickly, HBV RNA, so this viral protein also is coming from the cccDNA by transcription, a few protein listed here.

 

[01:07:29]

 

HBV RNA as a Biomarker for Safe Antiviral Discontinuation

 

And recent years, again, HBV RNA have been used in different setting, and would be quite a lot of study covering like stopping nucs.

 

So there are a few nice study, but I want to highlight this because it's coming from America, from the Hepatitis B Research Network led by Dr. Nora Terrault. So this is a very protocol-driven treatment and assessment, so it's very nice to see the role of all these biomarkers. So patient will receive TDF for almost 4 years with or without peg, so they stop the treatment if they fulfill certain criteria, and then they wish to understand who of these patient will either develop ALT flare-up to 5 time, quite similar biochemical flare, or the other thing would be they can remain on a sustained partial cure.

 

So these are the very clear predictors. In fact, HBV RNA have role at both sides, so I think like the ALT flare, obviously, if RNA remain detectable at the end of a treatment, in fact, it will predict flare. On the other hand, if it's not detectable, then it's good. The patient can maintain a partial cure.

 

[01:08:37]

 

HBV RNA as a Biomarker to Predict Sustained Partial Cure

 

And this flowchart is very helpful. So let's focus on the blue bubble first and talk about maintain a partial cure.

 

So from one end, you will see that for young patient, in fact, it happens very rarely, so the probability is very low. But for the other far end, for those with undetectable HBV RNA at the end of treatment, together with very low surface antigen, below 100, in fact, the probability is quite good. It's more than 70%.

 

It's a quite good chance that you can stop the nuc, and the patient will be at least maintain at partial cure. They will be quite stable. Now let's look at the orange or red bubbles, and these are talking about the flare.

 

So in terms of flare, if the patient are older, older than 35, and as well, the HBV RNA is detectable, in fact, the risk of having flare is 5 times of the normal limit is, in fact, quite high, which means that these patient probably we should not stop the nuc. We just keep them on the treatment. So I think this flowchart is quite helpful.

 

[01:09:40]

 

Key Takeaways: HBV Biomarkers – HBsAg and Beyond

 

So just a table to summarize all these biomarkers. So again, surface antigen, we can measure the level. I think it's helpful to develop the different phases of the CE, HCC risk, as well as treatment endpoint.

 

HBV DNA, yeah, we use it every single day, but most of time, well suppressed. For cccDNA, because it's need liver biopsy, so we may not use it that common in our practice. It's mostly in clinical programs.

 

And for core antigen, yeah, correlated with cccDNA. In fact, the role is somehow quite similar with HBV RNA, that we can use it to predict if after stopping nuc, then whether they can either maintain impartial cure, or whether the risk of ALT flat. But I have to say that I rarely stop nuc for my patients.

 

So with that, I thank you very much. Let's move on to the panel discussion. Thank you.

 

[01:10:33]

 

Panel Discussion

 

Dr. Sulkowski: Well, great. Fantastic. That was just a wonderful overview of these markers.

 

Now we're going to ask Jordan how he uses these in practice, because I think that's the big question. You gave us a great overview of the data. I'll start by saying, at least in my practice, I have routine access to quantitative hepatitis B surface antigen, but I do not have access to RNA and core-related antigen testing.

 

But Jordan, tell me, how would you use these assays in your routine clinical practice today, as opposed to a research study?

 

Dr. Feld: Yeah, so we're fortunate also to have access to quantitative surface antigen, and I've had it for a number of years. And I actually find it very useful. As Grace said, that often in patients that have been on long-term nuc therapy, their HBV DNA is suppressed, and patients come in, and every time we see them, their DNA is suppressed, liver tests are normal, and there's not much to tell them.

 

But the use of quantitative surface antigen can really be a guide to show them what I describe it as, is this is how much hep B is still in your liver. So if they can see that there's still a high level of quantitative surface antigen, it's kind of the reservoir of hepatitis B, and it really makes it easier for patients to understand, A, that they're not cured just because the DNA is undetectable, and B, that if we stop the treatment, they're very likely to have a relapse when they've got a high quantitative surface antigen. I also tend not to stop patients very frequently, but in patients who really want to stop, this is a must-have.

 

I feel pretty strongly that you shouldn't be stopping patients without access to quantitative surface antigen testing to guide that therapy. And unfortunately, at least currently, we don't have access to those other markers in clinical practice yet either.

 

Dr. Sulkowski: You raise a really good point. I think I had one about showing individual patients kind of the likelihood that stopping would be a problem, because I do think people grow weary of being on daily nucleoside-nucleotide analog therapy, and with those other biomarkers, ALT and DNA being not detected, it can lead to this kind of false sense of security, but the virus is still there, and HBsAg's a window into that.

 

Grace, is your practice similar? You mentioned that you use HBsAg in your talk, but how often do you repeat it? You measure it once, so you have that first conversation. Do you repeat it, and if so, how often?

 

Dr. Wong: Oh, yes, that's a good point. I would say that, first of all, I have to say that in Hong Kong, it's not a reimbursed assay. In fact, patients pay out of their pocket, so we mostly check for our private patients. It's not a very expensive test. It's less than 100 US dollars per assay. It's acceptable.

 

Usually, we probably, for those put on nucs, we know it would change very slowly, so probably we check it maybe every couple years, and we see if they stay on almost the same for the 2 to 3 assay, maybe we can space out a little bit, but somehow in the support of patients, they change quite a bit, then maybe I can check it every year.

 

Dr. Sulkowski: So every new person, when you can get it, you'll order that, and then maybe once every year or several years.

 

Jordan, how about you? You're doing it on all your new patients. You're establishing their baseline. Then how often do you repeat?

 

Dr. Feld: Yeah, so we're fortunate to have pretty good access to it, and patients don't pay out of pocket, which is helpful. So we're typically doing it annually, so with their annual follow-up, they'll get a quantum surface antigen, and I think it's one of those things that, as we've fortunately had access to it for a number of years now, it's become almost really an integral part of our practice. It really helps us see the trajectory of a patient over time. And I think Grace highlighted that golden rule, which is a very nice study, but really one of the things that's important about it is it does require serial surface antigen tests to see that trajectory, and I think that having access to that is going to be critical as we move into the newer therapies.

 

Dr. Sulkowski: Maybe if I could take that a step further. So I actually measure them on all my patients, and I repeat yearly. I think it is an important window into what's happening inside the liver and the hepatocyte, but then I run into a bit of a problem.

 

I repeat it, and it's staying flat or stable, so in that golden rule slide, they're in that blue color, not coming down, or some come down, and I guess I want to talk through with each of you how you would talk to that patient who's on a suppressive nuc about that, they're not moving. What do you tell them?

 

Dr. Wong: I tell them it's not moving. So stay on the treatment, yeah.

 

Dr. Sulkowski: And new treatments are coming, so stay tuned. And how do you, Jordan, I assume it's the same thing. You sort of tell them, look, look, there are things in clinical trials, and someday.

 

Dr. Feld: I think it is actually a window to say, really this is a time to think about clinical trials because really it's very unlikely, and I must admit I've not shown them the golden rule slide in clinic, but I think to show them that there's really been minimal change in the surface antigen over time really does make people understand that they're going to be on therapy long term, and at least they should be open to the notion of considering some of the novel treatments.

 

Dr. Sulkowski: So great, and then, I think, what about if it's coming down? I'll make up some numbers, but let's say it was 5,000, and now it's come down a couple times, and now it's 1,000. How would you tell that patient they're starting on that good curve, down, but what would you tell them about the likelihood of getting to the functional cure? Because I find that a little bit hard to predict, but I'm curious how you would message that.

 

Grace, go ahead.

 

Dr. Wong: Oh, me first. Oh, okay, thanks.

 

Yeah, to me, from 5,000 to 1,000, I would say, oh, nice, you have your surface antigen drop, but it's still very high, so please stay on treatment, because as I mentioned, probably for my patients, at least go down below 100, then start discussing, or, in fact, I would not initiate to start talking about any discontinuation, yeah.

 

Dr. Sulkowski: Jordan, how do you talk to it?

 

Dr. Feld: Yeah, I agree entirely, and I think it can actually be very confusing for patients when it's come from 5,000 down to 700, and I'm saying, well, that's good, but actually, it's not that good, because obviously, most people are not that familiar with log changes, and you really have to explain to them that it's got to get down to 0.05 for them to understand that there's still a really long way to go when you're still up in the many hundreds, and certainly wouldn't consider stopping therapy unless they're under 100.

 

Dr. Sulkowski: Yeah, so take a small win, but ensure that they know there's still a long road ahead, and perhaps they won't get there. Well, we've run short on time for this section, so we do have, we want to shift over to our final segment of a lecture, and I'm going to keep Dr. Feld on camera, and ask him to walk us through the emerging therapeutic agents and strategies, and Jordan, I'll turn it over to you.

 

[01:17:43]

 

Beyond the Status Quo: Emerging Therapeutic Agents and Strategies

 

Dr. Feld: Great. Well, thank you, Mark, and a big thanks to the CCO team for making it possible for me to participate virtually, as you can probably see. I've had, unfortunately, sustained an injury, but I'm fortunately on the mend, so thanks for all the good wishes that I received from many people, but unfortunately, can't be with you, but still can participate today.

 

So I have the formidable task of going through all of the emerging agents and strategies that we're going to, that are in the pipeline for hepatitis B.

 

[01:18:10]

 

HBV Treatment Pipeline

 

And Mark showed you this slide previously of the viral life cycle, and what we've added here are the places where people have tried to interfere with this viral life cycle, and I'll try to highlight this, and we're going to go through some, but not all of these. I should apologize in advance that we won't cover every agent in development.

 

But you can start from the right and aim to block viral entry. You can then, once you go and really go to the source here and target cccDNA, either by targeting it for destruction or silencing it, so preventing transcription of cccDNA, and this can be really an important strategy, and I'll briefly discuss that.

 

Once you've got transcription of HBV RNA, this can be the next target, and there are a few strategies to target the viral transcripts, and these viral transcripts are then packaged, so we can go to the packaging inhibition or the capsid assembly modulators as a strategy to prevent replication, and then our nucs, as Mark nicely highlighted, really act quite late in the viral life cycle by blocking this reverse transcription step of replenishment of HBV DNA, and finally, we can think about blocking assembly and export of the intact virions, and although not shown here, there's a lot of interest in activating both the innate and adaptive immune system as a strategy to augment these antiviral strategies to get to HBV cure.

 

Now, let's start with focusing right by going to the holy grail here of targeting cccDNA.

 

[01:19:46]

 

Gene Editing or Epigenetic Silencing

 

And people have taken different approaches to this, and I think it's exciting in the last year, we've seen a number of strategies for either gene editing directly or epigenetic silencing, so silencing cccDNA have moved into Phase I trials, and this is pretty exciting because I think this would give us an opportunity to really turn off where the virus is coming from, and this has been done with a few different strategies, the CRISPR-Cas gene editing approach or other gene editors, ARCUS being another nuclease that also directly targets cccDNA and can silence integrated HBV DNA, and then a number of different epigenetic silencing strategies that both can target the cccDNA and the integrated DNA. And I think the real key here is that it's really only with these types of therapies that we think that a so-called complete cure where you could get rid of or at least inactivate all of the HBV DNA in an infected individual is really likely possible, and the fact that this is now moving into humans is really exciting.

 

I think there's still a lot of questions here. We don't know if these therapies are going to be adequate. Safety is for sure the biggest concern whenever we're getting and starting to tinker with the genome, and then I think it's also an important question that we ask ourselves, both as providers and for the patients themselves, is even if we believe it to be safe based on whatever analysis we can do, will it be safe enough that people will be comfortable taking these therapies? So certainly exciting days, but it's still pretty early along the path.

 

[01:21:18]

 

HBV Treatment Pipeline

 

So if we move next along in the life cycle to targeting the HBV RNA –

 

[01:21:24]

 

Small Interfering RNA and Antisense Oligonucleotide

 

– there's been a lot of interest in doing this, and the 2 major strategies that have focused here are the small interfering RNA and the antisense oligonucleotides, and they are similar, but there are important differences between these strategies.

 

The siRNAs, one of the nice things is because of the conserved genome of HBV and the overlapping open reading frames of the viral transcripts, you can have a single siRNA target trigger that will cover all of the HBV transcripts, and the nice thing about this is there's the potential to actually block 2 aspects of the viral life cycle. One is that you directly can target pregenomic RNA, which is the template for DNA replication, so you directly block replication, but also this brings down the protein level, surface antigen, core antigen, HBeAg, and that potentially restores immune function, so you may get sort of 2 for 1 here by reinvigorating the immune response.

 

The antisense oligonucleotides, a similar concept, it also targets HBV RNA species, but this is done using a different approach. Instead of the microRNA processing that the siRNA uses, this is using RNase H, and it's done in a different part of the cell, so you have a different approach to these, and we've seen different outcomes with these different therapies.

 

[01:22:46]

 

siRNA Monotherapy: Common Themes

 

So a number of different siRNAs have been evaluated, and I've just shown a few here just to illustrate that there are a few common themes. What you see is this initial very rapid decline in the quantitative surface antigen level when people start siRNA therapy, and then we see this plateau, this slower second phase decline, and then really a pretty solid plateau where very few people, if any, will actually clear surface antigen with siRNA therapy alone.

 

Now, interestingly, if you stop therapy, some patients will rebound, but about 40% or so will maintain a lower baseline, lower HBsAg level than they started at before treatment, and it's unclear exactly what that indicates, but so, these have certainly emerged as an important part of therapeutic combinations, but as a monotherapy are probably not enough.

 

[01:23:36]

 

B-Clear: Bepirovirsen Added to NA

 

The other real advance has been with the antisense oligos, and I think most people are familiar with bepirovirsen, which has been studied in large Phase II trials and now is in a Phase III trial, and here you see the be clear data where patients were either starting on a nuc, they were either suppressed on nuc therapy or had a nuc therapy added at the time of starting the bepirovirsen. And what you see is there were different strategies here of giving the therapy, primarily whether it was given for 24 or 12 weeks.

 

And what you can see is in the dark green bars is you can see that up to about 30% of patients cleared surface antigen on treatment, and then when they came off the bepirovirsen 24 weeks off therapy, you can see that unfortunately a number of people had surface antigen reemerge so that now we're getting only about 10% of people who achieve HBsAg loss that persists off therapy with this therapy, and it does require the 24 weeks of treatment.

 

[01:24:35]

 

B-Clear: Primary Outcome by Baseline HBsAg and HBeAg Status

 

However, you can potentially identify predictors of response to try to enrich your population, and the biggest predictor here was the baseline surface antigen level. So you can see in both the antigen-negative, and although much less common among the antigen-positive patients, if they were fortunate enough to have a surface antigen level less than 3,000, they were much more likely to end up with clearance of surface antigen with the bepirovirsen therapy.

 

[01:25:01]

 

B-Clear: ALT Flares

 

Now the treatment has an interesting trajectory. What you see is that the surface antigen level goes down, and really in concert with this, there's a rise in ALT where the liver enzymes go up really almost at exactly the same time as the surface antigen decline, and this has led to a lot of question about whether this is actually driving an immune response rather than just targeting the viral transcripts themselves, is this actually an immune-mediated mechanism where you're getting immune activation that's leading to viral clearance. And one of the arguments for that, particularly, is that the form of the antisense oligo specifically with bepirovirsen that's been active is the version that is not conjugated to GalNAc, so it's not targeted to go into hepatocytes, and much of it actually gets taken up by other cells, particularly non-parenchymal cells like macrophages in the liver, which then may trigger an immune response and drive surface antigen decline.

 

[01:25:57]

 

B-Well 1 and B-Well 2: Bepirovirsen Added to NA

 

Now this is exciting because these Phase II data have led to these Phase III trials which are currently ongoing, and we're expected to have data from these very soon, and these are enrolling patients with surface antigen level less than 3,000 based on trying to enrich for a response, and hopefully with 6 months of therapy we're going to see high rates of HBsAg loss and functional cure, which would be a real advance. This is the first Phase III trial in many years in HBV.

 

[01:26:28]

 

Another ASO: AHB-137

 

In addition to bepirovirsen, we also have another antisense, which has been evaluated so far in China, and the data have looked quite exciting. Enrolling patients learning from the bepirovirsen experience with surface antigen levels less than 3,000 but above 100. And what you can see given for 6 months, a similar sort of approach that you see a high proportion of patients clearing surface antigen, and you can see that that actually gets up to as high as around 70%, so really impressive HBsAg loss on therapy, and at least data presented earlier this year at EASL suggested that much of that is durable off therapy. Also see ALT elevations very similarly, and it'll be exciting to see more data as this compound is further developed.

 

[01:27:14]

 

Investigational HBV Treatment Approaches: ASO and siRNA

 

So to contrast these 2 approaches to targeting HBV RNA, they use different targets, so the RNase H for ASOs versus the mRNA processing in the cell, the risk complex for the siRNAs. I mentioned that ASOs use the non-GalNAc conjugated form, so that's really going into primarily not into hepatocytes, whereas the siRNA are GalNAc conjugated, so really, going only into hepatocytes and that may distinguish how these compounds work differently. The ASOs are given more frequently, whereas the siRNAs can be given monthly or even less frequently.

 

It's unknown how they differ in their control of cccDNA versus integrated DNA, but siRNA seems to target both and it's less clear for the ASOs. The effect of the ASOs, you get a potent surface antigen decline in some and surface antigen clearance in some, whereas in siRNAs it's more predictable that everyone has a decline, but most people will then plateau, and few will clear.

 

ALT flare is common with ASOs, uncommon with siRNAs, and then off treatment we get the prolonged effect in some on the ASO and the siRNAs. I mentioned that some patients have a lower surface antigen level after treatment. Unclear whether these lead to the immune restoration that we hope with lowering HBsAg levels. And the surface antigen loss rates have really varied quite differently between the ASOs that have been studied so far, and at least with monotherapy with siRNA seem to be quite rare.

 

[01:28:42]

 

HBV Treatment Pipeline

 

So let's move back to the viral life cycle and go to the next step in the viral life cycle, and you can see here that after the RNA is generated, it needs to be packaged prior to DNA synthesis.

 

[01:28:56]

 

Capsid Assembly Modulators (CAMS)

 

And so this has led to the development of capsid assembly modulators, which interrupt with this process. And I'm going to try to show that these capsid assembly modulators really have 2 mechanisms of action. You can see that the primary thing is that they block this encapsulation step that's shown here on the right, and what that will do is it will reduce the number of DNA-containing viral particles so inhibit viral replication. It will also inhibit the amount of RNA-containing particles. So all of the RNA we detect in the [inaudible]

 

Dr. Sulkowski: We'll see if we can't –

 

Dr. Feld: The involvement in the –

 

Dr. Sulkowski: Sorry, are you – Jordan, you froze for a minute, just so you know. You've got a –

 

Dr. Feld: Oh, okay. Where was I?

 

Dr. Sulkowski: You were telling us about RNA-containing particles and left us hanging there. But yeah, maybe we'll stop your video and – oh, boy. Okay. Well, we'll see if we can fill in for Jordan here. Let's see if we can get it back. So technology is really great when it works, and we'll work on getting Jordan back. It's wonderful he could join us.

 

So what he was walking through here on this slide is that the primary mechanism of action is really blocking this encapsulation step. So in the blood that will lead both to no DNA or what's depicted here is Dane particles, intact virions, but also no RNA containing particles. So, HBV RNA falls with CAMs.

 

But there's also this secondary mechanism of action, which is this arrow that kind of circles back, and this is a replenishment step, which is some of the RcccDNA goes back into the nucleus and replenishes the cccDNA, and it really keeps that potentially that cell as a factory, if you will, producing particles.

 

[01:31:08]

 

JADE: Capsid Assembly Modulator

 

So there have been several capsid assembly modulators in clinical trials. This was one of the very early ones, a randomized partially-blinded clinical trial with a drug at the time that was known as JJ379, and here they enrolled individuals who were antigen-positive not currently on treatment.

 

So what you can see – Jordan, feel free to jump in. I was walking him through the JADE particle, but I am more than happy to turn it back over to you.

 

You good? Jordan, yeah, you're good to go. I don't know if you can see me or what you're doing.

 

Dr. Feld: Yeah, I can see you back there. Okay, so hopefully – okay, so now we're back up there. Okay, good. Sorry about that. I apologize for the interruption.

 

So I don't know if you heard that, the CAM-A/CAM-E, aberrant versus empty capsids, but the CAMs are similar in what they do. And what this shows here is this is just an example of one where you see very potent suppression of HBV DNA similar to what we see with nucs. But a real distinction between the nucs and the CAMs is that here you also see this decline in HBV RNA with the CAMs, something that doesn't happen with the nucs. So that's a change, but it's important to remember that HBV RNA is a marker of cccDNA transcriptional activity. And so when you see declines in HBV RNA, we get excited, that means maybe cccDNA is eliminated or silenced.

 

With a CAM, it really just means target engagement because it means that you're interrupting this formation or encapsidation of the HBV RNA, so you don't measure it in the serum. So it's important to distinguish what a decline in HBV RNA means, but it is something that you reliably see with CAMs.

 

[01:33:02]

 

Pevifoscorvir: Antigen Declines

 

Now one thing that's interesting is that the first-generation CAMs did that, but they didn't have any effect on surface antigens. So with more potent CAMs, we're starting to see the potential to actually have this secondary mechanism of action and influence cccDNA, and this agent that formerly was known as 1A4 but now is pevifoscorvir, if I'm pronouncing it correctly, is a potent CAM. And you can see here that this is the first time that we've seen a surface antigen and other antigen declines using this mechanism of action, and you can see here with the surface antigen in blue and the HBeAg and core-related antigen going down on therapy. But interestingly, the effect was seen much more so in HBeAg-positive and HBeAg-negative patients.

 

There did seem to be a plateau in this surface antigen decline, and it raises the question of whether this is really blocking only surface antigen decline that's coming from cccDNA, as you might expect, and not having an effect on HBsAg that comes from integrated HBV DNA.

 

[01:34:06]

 

Key Points: Capsid Assembly Modulators

 

So some key points to summarize the CAMs. These are potent small molecule inhibitors of viral replication. And the newer CAMs may have 2 mechanisms of action: blocking replication by blocking encapsidation, sort of mopping up that leak that Mark mentioned that we see with nucleoside analogs, and then the second mechanism of affecting cccDNA establishment or replenishment. But I think it's important to think about if you're going to use this approach, long-term therapy really may be required if you're going to actually get to functional cure, but it raises another question of whether that should be the only thing we're aiming for.

 

We'd certainly like to see a functional cure, but would we ever accept something like chronic viral suppression as an alternative goal?

 

[01:34:47]

 

Redefining Therapeutic Goals: 2 Potential Strategies

 

And I think it's important when we think about our strategies, we've really focused on the idea of moving away from suppressive therapy and getting to finite therapy, and I think we really hope that we'd get to complete cure.

 

That's proving very challenging with our current therapies. Even a functional cure has proven really a pretty high bar with the therapies that have been under development, and that's sort of opened the door of this idea of partial cure, or a term I prefer, sustained control, where patients may have a low level of surface antigen and no markers of cccDNA transcriptional activity and have a long-term good outcome, but I think we're really uncertain about what that looks like and whether it's a stable position.

 

An alternative would be chronic suppressive therapy, which of course we can do with the nucs to a fairly reasonable degree, but the question is if we can't get people completely suppressed as we previously discussed with nucs, then would something like another potent antiviral like a CAM get us to more persistent suppression, which might ultimately lead to those strategies that might lead to finite therapy.

 

[01:35:53]

 

What About Chronic Suppressive Therapy?

 

And this at least gives you a question. We looked at similar data earlier where we saw that if you take HBeAg-positive patients with very high HBV DNA levels, you can see that whether they get TDF alone or TDF with emtricitabine, you can see that a significant minority of patients, even with long-term therapy, never get to complete HBV DNA suppression.

 

Now a question that we don't know the answer to is: does this matter when you take these very highly viremic patients, with getting rid of these last little bits of HBV DNA actually change their clinical course? We don't really know, but as Mark highlighted, one of the things that's new in the guidelines is this idea about transmission risk, and it's almost certainly true that the lower the HBV DNA, the lower the transmission risk. So this would be one reason why getting to complete suppression would be helpful.

 

[01:36:42]

 

Chronic Suppressive Therapy: Would a CAM Help?

 

Now when you look again, coming back to the CAMs, you can see that actually maybe they are getting to more significant viral suppression. So you can see here, this is a very small study with only 10 HBeAg-positive and 9 HBeAg-negative patients, but what you see is that these patients actually get to HBV DNA levels down that are very quickly below the lower limit of quantification, and actually most getting to the lower limit of detection even when they start with very high levels of HBV DNA that you see in HBV HBeAg-positive patients.

 

So this at least gives us promise that this type of more potent therapy might be able to suppress even highly viremic patients.

 

[01:37:25]

 

Posttest 3: Evidence suggests that, in most cases, capsid assembly modulators for CHB treatment are associated with:

 

So I'm going to come back to the question we asked you previously. Evidence suggests that in most cases, capsid assembly modulators for chronic hepatitis B treatment are associated with:

 

1. Control of viral replication with finite therapy;
2. Decrease of HBV DNA and RNA below the lower limit of quantification;
3. Rapid surface antigen decline but not complete surface antigen loss; and
4. Achievement of surface antigen loss.

 

So we'll ask you to answer the question.

 

Great. Well, if I'm looking at the, if I'm looking at the screen correctly, it looks like we've seen a nice shift in the answers, and most people recognizing, that indeed the CAMs will bring down HBV DNA, and unlike nucs, will also bring down HBV RNA, and most people, both HBeAg-positive and negative, will get down below the lower limit of quantifications, which really shows the potency of these agents.

 

[01:38:31]

 

And although we have seen some surface antigen declines, the decline really plateaued. There was minimal effect in the HBeAg-negative patients and so far no one losing HBsAg with these therapies alone.

 

[01:38:44]

 

Pros and Cons of Chronic Suppressive Therapy

 

So if we sort of think of the pros and cons of thinking about chronic suppressive therapy, the pros, if you bring down suppression to below the lower limit of detection, you may really be getting too close to blocking all the replication that's going on in the liver, not just what we measure in the blood. So that reduces infection of new cells, potentially reduces new integration events, which we think are carcinogenic, and it certainly reduces the risk of infectivity. It may eventually lead to more sustained control, and actually functional cure.

 

And this would give us the option of potentially expanding treatment to immune-tolerant or highly viremic populations or those with very high surface antigen levels for whom our current therapies are not likely to be adequate. The downsides, of course, it's a much lower bar than a functional cure. It's still going to require long-term therapy, and I think it's really probably the biggest question is it's unclear if it's truly a benefit over our current new therapy, even in people with low-level replication.

 

Does that actually matter? So we clearly need outcome data to understand whether this is an important benefit.

 

[01:39:46]

 

Immunotherapies

 

Now, the other side of the strategy for achieving HBV cure is on the immune system side, the immunotherapies, and there have been approaches to look at the innate side and the adaptive immune system to try to control HBV from cytokine therapy with our old friend interferon.

 

Toll-like receptor agonists, RIG-I agonists were tried. On the adaptive side, monoclonal antibodies, a lot of interest in therapeutic vaccines, and also using checkpoint inhibitors. I think the other notion, at least, is that by reducing viral antigens, that we may reinvigorate the immune system, and that has some potential, but it's actually been hard to demonstrate that that's been true so far. And at least so far of the immunotherapies that have been studied, interferon is making a bit of a comeback.

 

[01:40:32]

 

Potential Treatment Combinations

 

And then, of course, we can think about putting these viral strategies together with the immune strategies, and many of you have seen some variation of this slide where we're going to think about blocking viral replication, bringing down protein levels, and then bringing in the knockout punch with some type of immune target, but thinking about how to combine these therapies, which combinations, which order, whether they need to be in sequence or together is really quite challenging.

 

[01:41:00]

 

Combinations Under Investigation

 

To date, there's been a number of combinations that have been investigated. Lots of things looking at combinations with siRNAs, many others in combination, and so far, I would say, relatively early days with the combinations, and unfortunately, it's been a little bit underwhelming. There's not a clear winner yet, and interferon has clearly made somewhat of a comeback.

 

We've actually seen some higher HBsAg loss rates with interferon combined with siRNAs as well as with some of these other strategies, particularly some of the therapeutic vaccine or vaccine analogs.

 

[01:41:36]

 

Conclusions

 

To conclude, we do have many targets for HBV functional cure. I touched on some of them.

 

Gene editing could really be a game-changer, but I think we're still really early in the development. It's exciting to see those move into the clinic. siRNAs, lower surface antigen level, but rarely lead to functional cure on their own. That said, they may be a useful backbone in combination therapy.

 

The antisense oligos are clearly effective for patients with low HBsAg levels, and it's exciting to see them moving into Phase III trials. Talked a fair bit about the CAMs, these potent replication inhibitors, which could have a potential role, especially in highly viremic patients, to get to really undetectable levels and really be important if we looked at chronic suppressive therapy. And the immunotherapies, many interesting options, although interferon seems to be somewhat leading the pack so far.

 

I think we may have to think about tempering our expectations a little bit and think about something a little bit less than functional cure as an interim. But ultimately, I hope we will be able to get to functional cure and maybe even complete cure one day down the road.

 

And with that, I'll turn it back to Mark to bring back the panel.

 

[01:42:46]

 

Panel Discussion

 

Dr. Sulkowski: Well, great. Thanks, Jordan. That was a wonderful overview of the really dynamic and ever-changing landscape. And certainly, this meeting has been exciting for a lot of new modalities coming forward. So a lot to discuss as we get into the rest of the meeting here today and tomorrow. But I wanted to sort of come back to a point and maybe have a discussion.

 

We do have about 15 minutes for panel discussion, which is fantastic. So, Jordan, one thing I've thought about, and it's a bit risky to put this idea out here in public, but I've really thought about viral suppression. Antivirals is the backbone for any curative regimen.

 

If you don't have someone suppressed, they're going to continue to reinfect new hepatocytes and you'll be chasing yourself. So would you agree that getting the virus shut off as much as possible before you do any of these things or while you're doing any of these things, whether it be a different MOA, is that the right way to think about it?

 

Dr. Feld: I mean, I think it makes a lot of sense. I mean, I must admit, I tend to be more on the virology side. I like targeting the virus rather than the host.

 

Just targeting the host makes me a little bit nervous, although the immunologist won't like me for saying that. But I think what you're saying makes a lot of sense. The one caveat to it would be that when you combine immunotherapy with antiviral targets, there's at least some idea that perhaps you need at least some antigen around, maybe not nucleic acid, but antigen around for the immune system to target.

 

And at least some work from Adam Gehring's lab showed that if you knock the antigen levels down too low, you may not actually be able to trigger a functional immune response to control replication. But in principle, I think the notion that you bring up makes a lot of sense, that blocking infection of new cells is really critical, and we've got to shut off the leak that we still have with nucs.

 

Dr. Sulkowski: So Grace, any thoughts on viral suppression? As you bring patients into potential cure trials, what are your thoughts about viral suppression?

 

Dr. Wong: Right, yeah. I think currently the field is still dominated by recruiting new suppressed. I think probably because at early-phase development we prefer something safe, that they have a stable, and you kind of add something, hopefully can make it better.

 

The worst might be status quo. But I think there's still a lot of rooms that for those naive patients, be it they fulfill or do not fulfill treatment indications, I think there are so many of them. So I think they also need some novel therapy to help them.

 

So I would say that if we do have something work well as safe for patients who are not new suppressed, in fact, that would be also very helpful.

 

Dr. Sulkowski: Great, let me think about it another time. Both of you addressed HBsAg in the blood, which the current assays we use don't distinguish where it's coming from. And Jordan, you brought up a really interesting sort of possibility that you could eliminate cccDNA as a source for HBsAg, and then what's left is coming from integrins, which, of course, a CAM or other antivirals won't work against.

 

So maybe we could talk a little bit. There's been a push to try to, how can we figure out that question, the HBsAg we're measuring, where it's coming from? Grace talked about some other markers, but maybe we could just talk through about how you think about that particular question.

 

Jordan, go ahead.

 

Dr. Feld: Yeah, I mean, I think it's a really important question for the field, is just figuring out where HBsAg is coming from. Because I think we would be very happy if we could get a therapy that eliminated or silenced all the cccDNA in the liver, and yet that person could remain HBsAg‑positive, not meet our definition of functional cure, not have the other benefits for the person about stigma and other things that go along with HBsAg clearance that we would anticipate because of this source of integrated DNA. And we really don't know if that actually matters.

 

I mean, whether the integration is producing surface antigen or not, it may be the integration event itself may predispose to cancer, but I'm not sure whether or not the production of surface antigen changes that risk in true. So it would be really nice to have an assay that distinguished this. And there are some research assays, as you know, from your colleagues at Johns Hopkins, from Ashwin Vallagopal and Chloe Teo, have developed some nice tools to potentially be able to distinguish this.

 

But I think it's really an unanswered question in the field. Some question about the size, the type, whether it's the large, middle, or small surface antigen and the ratio between those that could distinguish those. But I think right now we're still stuck where we can't tell where it's coming from.

 

And that's why potentially developing this idea of sustained control or partial cure where you get a low surface antigen level, we don't know where it's coming from, but we know it's very low, no markers of active transcriptional activity, so core-related antigen, HBV RNA undetectable, that might be a durable state that's associated with very good clinical outcomes even though someone remains HBsAg-positive.

 

Dr. Sulkowski: So let me pick up on that, Grace. You showed data showing that in the stop nucs studies, and I'll pause there to say that the updated AASLD guidelines, like you, don't recommend stopping nucs routinely. But what you suggested is if you could interrogate cccDNA transcriptional activity using RNA and core-related antigen, which are markers of that, although imperfect, so you're using those in those studies.

 

What they're suggesting is for those patients who are negative in the blood, most of that HBsAg may not be cccDNA. Do you think they're good enough? Should we be using those in clinical practice? I recognize they're not available, but one of the questions we got was: should they be available, and will they be available? Maybe we can talk through that.

 

Dr. Wong: Yeah, yeah, I think that would be very helpful to have all these markers in our practice because some nice study from Life of Crack, for example, in Japan, in fact, they have been using that almost routinely. It's quite helpful to predict all the outcomes that I mentioned. I think there have been quite good evidence showing that if you really want to stop, then HBV, RNA, core-related antigen, if they are low enough, I think it's safe to stop.

 

But it's still, at most, partial cure, you may say, so it's still not functional cure. Another point I would like to make is all these assays at this moment are not perfect, be it the sensitivity or accuracy. I would love to have more sensitive tests. If these biomarkers are really negative with sensitive tests, I think it would be safer or closer to functional cure to stop a nuc.

 

Dr. Sulkowski: That's great. Maybe we can just push this a little bit further. Jordan, you kind of suggested that potent viral inhibition with a CAM or other agents might, over time, lead to this loss of cccDNA activity, and you sort of implied that would take a long time.

 

So I'm taking a bit of a question we got asked. What is the lifespan of the hepatocyte, and how long would you have to wait? I know that's a bit of a difficult question, so that's why I'm giving it to you.

 

Dr. Feld: Thank you. Yeah, that is a challenging one, and people have speculated for a long time on what is the half-life of cccDNA, and clearly, cccDNA persists probably as long as the hepatocyte survives. Most data suggests that it generally does not survive cell division, but at least there have been some speculation that at least on occasion can even survive cell division, which makes it even more challenging.

 

And, of course, hepatocyte turnover is driven by a lot of things. So with more inflammation, there's more hepatocyte turnover, whereas when you really have things in a quiescent state, there's much less hepatocyte turnover. But the estimates that have used, have modeled out the amount of time you'd have to take to clear all the infected hepatocytes suggest, at least with nucs, based on the trajectories, that it would take many, many years, and in fact, potentially decades, to get to S-loss. But that, I think it's important to highlight, that's in the presence of this leak.

 

Now, if you could get to a true turning off, as you said, turn off the spigot, so there's no more leak, then potentially you could accelerate that quite a lot. I mean, I think it's hard to say what that looks like, and it's hard to design clinical trials that take 3 or 4 years, but it's not inconceivable to me that with very potent suppression, you could start to get HBsAg loss within a couple of years of treatment.

 

Dr. Sulkowski: So that interesting concept, and maybe I'll pick up on another theme that came in from some of our questions that popped in. So when you get to functional cure, the general understanding is that those individuals who are HBsAg-negative will retain some replication-competent cccDNA that is presumably silenced or held in check. How does that persist, and what do we know about the risk of reactivation?

 

And Jordan, I'll give you a break, and start with, I know it's another difficult question, but I'll start with Grace.

 

Dr. Wong: Wow, yeah, that's a good question. I think at least from what we have, the data at this moment, in fact, the risk of reactivation in general is low. Yeah, that's in general.

 

Yeah, but it will happen in some situation, obviously, more suppression, or like the data I showed, in fact, the durability is up to 90% in 5 years, which means that there will be 10% of some patient, they may have several reversions, surface antigen, seroreversions, but most of these case, in fact, the surface antigen would be at very low level, and HBV DNA either undetectable or again, very low level, which means that even they still have some replication, but usually would be at very low level, and most of the time, most people may not need retreatment unless the HBV DNA become detectable again.

 

Dr. Sulkowski: So Jordan, I'm going to just push this a little bit for you, and you talked about the half-life of cccDNA in a potential model, yet there have been examples of patients who are core-antibody-positive, S-antibody-positive, antigen-negative, DNA-negative for many years, if not decades, they receive something like rituximab or some other type of therapy, and after decades, the hep B DNA reactivates. The question is, what biology happened there in the liver that that cccDNA persisted? Grace suggested kind of low-grade replication occurring to sustain it, or is there some other biology that we just don't understand yet?

 

Dr. Feld: I mean, it's a great question, and I definitely don't have any kind of conclusive answer to that. I mean, I think the notion that the DNA comes back implies that it really is coming from cccDNA, so this is not just integrins that are producing virus. We don't get HBV DNA coming off of the integrins because of the way the integration events occur.

 

So this really does presumably mean that you've got, and I think this is probably the strongest evidence for using immunotherapy, is that we know that immune control, when done naturally, is A, quite potent and really good at keeping the cccDNA transcriptionally silent, even when it still persists. But I think it probably just gives us this small word of caution that even when we get to functional cure, and I think that's an important consideration for the whole field, is that we're going to have to understand what that risk looks like, especially when we use new modalities that target the HBsAg directly to get it to undetectable levels.

 

Will this persist in the same way that we see clearance occurring with either nucs or with spontaneous S-loss? And I can't give more hand-wavy an answer than that, so I'll stop.

 

Dr. Sulkowski: Yeah, that's great. I'll give you guys both one more question. So we talked a lot about the new antiviral that a CAM-E might be, so let's say that were available today.

 

We talked about some scenarios of angio-positive patients, difficult to suppress those individual nucs, people are persistent. So Jordan, if I gave you a CAM-E today, how would you use it in practice? Where do you think it's going to fit?

 

Dr. Feld: Yeah, I mean, I think for me, it's really the groups of people who are not going to be ideal for some of the other therapies that are coming along that are looking like they're targeting predominantly low S-level populations, so like the ASOs look like they're great, and someone who comes in with an S-level of 600 or something, that person has a pretty high chance of responding to an ASO, and it's going to do well, or maybe to one of the other therapies that are further along in development. But a person that comes in with 7 logs of virus, or to say 9 logs of virus, HBsAg levels of 50,000 or beyond the level, you can't measure it, you got to dilute it too many times to measure it. I don't, with anything we have, you're not going to get them suppressed on a nuc, and they're certainly not going to respond to most of the therapies that are in development, but they may say, "Look, I want to be treated because I am very worried about infecting household members, a partner, other risks," despite vaccination efforts and all the things you pointed out about the vaccine caveats, that that would be a population where we might want to say, "Let's treat you."

 

And I guess, sort of coming back to the point about really potent viral suppression for a few years, that might be really important in someone who's young, so you have a 25-year-old that takes treatment for 3 or 4 years, and if that got them to clear surface antigen, we don't obviously know that that would happen, but if it did, and either make them eligible for some of those other therapies, or get them to S-loss on its own, that saves them a whole lifetime of hep B, whereas some of these other therapies are going to be more useful in older patients who are already starting with lower S-levels, and may already be actually at lower risk of bad outcomes.

 

[01:56:44]

 

[END OF TRANSCRIPT]