NVR 3-778 Late-breaker at AASLD 2015

[StephenCastlecrag]

LB-10
Phase 1b Efficacy and Safety of NVR 3-778, a First-In-
Class HBV Core Inhibitor, in HBeAg-Positive Patients
with Chronic HBV Infection
Man-Fung Yuen3, Dong Joon Kim4, Frank Weilert5, Henry lik-Yuen Chan6, Jacob P. Lalezari7, Seong Gyu Hwang8
, Tuan T. Nguyen9, Sandy Liaw1, Nathaniel Brown1, Klaus Klumpp
1, Lalo Flores1, George D. Hartman1, Edward J. Gane2;
1Novira Therapeutics,Inc., Doylestown, PA;
2Auckland Clinical Studies, Auckland, New Zealand;
3Queen Mary Hospital, University of Hong Kong, Hong Kong, Hong Kong;
4Chuncheon Sacred Heart Hospital, Hallym University, Gangwon-do, Korea (the Republic of);
5Waikato Hospital, Hamilton, New Zealand;
6Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong, Hong Kong;
7Quest Clinical Research, San Francisco, CA;
8CHA Bundang Medical Center, Gyeonggi-do, Korea (the Republic of);
9Research and Education, Inc., San Diego, CA
Background: Current therapies for chronic hepatitis B (CHB)
can suppress HBV replication but long-term therapy is required
in most patients. HBV Core (capsid) protein plays multiple roles
in HBV persistence. NVR 3-778 is an HBV core inhibitor which
can potentially inhibit viral assembly, HBV genome replication,
cccDNA replenishment, and hepatic reinfection cycles. We
report clinical proof-of-concept data for NVR 3-778 from a
multicenter Phase 1b trial in patients with CHB.
Methods:
Safety and efficacy were assessed in 4 dosing cohorts of adults with chronic HBV infection. Patients were 18-65 yrs,, predominantly male, and HBeAg-positive with serum HBV DNA > 20,000 IU/mL . ALT levels could be normal or elevated to less than 7 times upper limit of normal. Patients were randomized to NVR
3-778 capsules (10 patients/cohort in first 2 cohorts, 8/cohort
in last 2 cohorts) or placebo (2 patients/cohort) for 28 days.
The first 3 cohorts received NVR 3-778 doses of 100, 200, or
400 mg QD, and the 4th cohort received 600 mg BD. Safety
evaluations included adverse events (AEs) and safety-related
clinical labs.
Results:
A total of 44 patients were enrolled in the 4 cohorts; 36 received active NVR 3-778 treatment. Safety and tolerability of NVR 3-778 were satisfactory for all cohorts, with no treatment-related discontinuations or serious adverse events (SAEs). AEs and lab abnormalities were generally mild and not related to study drug. A patient in the 100 mg cohort developed a rash involving the hands and feet that was considered to be serious. No other study patients developed a significant rash. Small HBV DNA reductions were apparent with 200 mg and 400 mg QD dose cohorts. With tripling of the daily dose to 1200 mg (600 mg BD) the mean 28-day reduction in serum HBV DNA levels increased substantially to 1.72 log10 (range 1.06-3.71 log10 IU/mL). PK results indicated multi-micromolar concentrations of NVR 3-778 supporting QD or BD dosing, with dose-related increases in drug levels. The study is advancing to evaluation of a combination of NVR 3-778 and peg-interferon. A higher dose will be tested to define a maximal-effect dose for NVR 3-778, and a nucleoside combination regimen will be tested later.
Conclusions:
NVR 3-778 was well-tolerated in patients with CHB. 600 mg BD dosing achieved significant reductions in HBV DNA. When used alone or in combination with current HBV antivirals, NVR 3-778 may contribute substantial efficacy by unique Core-related
mechanisms, toward a goal of increased durable response rates in HBV patients.
Disclosures:
Henry Lik-Yuen Chan - Advisory Committees or Review Panels: Gilead, MSD, Bristol-Myers Squibb, Roche, Novartis Pharmaceutical, Abbvie; Speaking and Teaching: Echosens
Sandy Liaw - Employment: Novira Therapeutics
Nathaniel Brown - Consulting: Presidio Pharmaceuticals; Employment: Novira Therapeutics
Klaus Klumpp - Board Membership: Riboscience LLC; Employment: Novira Therapeutics Inc
Lalo Flores - Employment: Novira Therapeutics
George D. Hartman - Management Position: Novira Therapeutics
Edward J. Gane - Advisory Committees or Review Panels: Novira, AbbVie, Janssen, Gilead Sciences, Janssen Cilag, Achillion, Merck, Tekmira; Speaking and Teaching: AbbVie, Gilead Sciences, Merck
The following people have nothing to disclose: Man-Fung Yuen, Dong Joon Kim, Frank Weilert, Jacob P. Lalezari, Seong Gyu Hwang, Tuan T. Nguyen

[StephenCastlecrag]

Well, it is not another NUC, it is a core inhibitor.

[StephenCastlecrag]

I wish I can say that I understand it all, but I don't. Many thanks again for the detailed explanations.

[studyforhope]

All membrane proteins are made and inserted directly into the ER membrane.
the translating ribosome in the cytosol is directed via adaptor proteins to the cytosolic side of the ER membrane, where it threads it's growing polypeptide chain directly through protein channels into the ER membrane, in and out four times in the case of the surface antigen protein monomer.

Thus the surface antigen is never present in the cytosol, it's monomer is a four pass (with four alpha helixes directly sitting in the lipid bilayer) transmembrane protein.

The monomers produced into the  ER membrane will then start to drift laterally until they touch each other and attach with some lipid bilayer left to fill the spatial gaps.
Because they are mildly pyramid shaped those monomers will now start to bend the ER membrane into a growing sphere, that eventually buds into the ER lumen, forming a mostly spherical hollow particle composed of many monomers, with the famous "a" loop protruding outwards.
Some L and M monomers are also typically included into this sphere and the hepatitis delta virus is able to insert itself inside the hollow center with its antigen and genomic RNA , in case of a coinfection, BTW.

By now we have the true subviral particle formed, that is then transported and secreted to the hepatocyte surface and released into the circulation.

THE NAPS BLOCK THE FORMATION OF THE PARTICLES FROM THE MONOMERS, with great efficiency, but will not interfere with the primary synthesis of the monomers into the ER membrane.
In contrast the interfering RNA will simply reduce messenger RNA that reaches the ribosomes, thus less hbsag monomers are made.

It is most important for the interactions with the surface antibody, to also see that not all monomers are used to form particles, but will rather be leaking out to the outer cell membrane, so that an infected or integrated hepatocyte is "studded" with surface antigen monomers.

These cells will greatly participate in the capturing and inactivation of antibody in the liver, in addition to the antibody that gets trapped in the circulation by the subviral surface antigen particles.

Your second paragraph describes the mechanism by which the epitope peptides are transferred from the immunoproteasomes into the ER lumen, where they are then loaded onto the MHC class I membrane proteins, for final transport to the outer cell membrane, for presentation to the t cell receptor.
It is no surprise that the proteasome locate closely to the ER membrane to facilitate the transfer process.
Nevertheless,  these proteasomes  must first process and digest a protein from the cytosol, thus the e antigen is much more available for this processing than the hbsag monomers.

[StephenCastlecrag]

Thanks. This is a bit above my understanding, why would HBsAg be produced in the ER membrane? I know it accumulates in the ER, but why is it produced (its mRNA translated) there?

I also find this:
http://eprints.qut.edu.au/50470/
"Immunoproteasomes were strongly enriched around the endoplasmic reticulum as judged by double-immuno¯uorescence experiments with anticalreticulin antibodies, but were also present in the nucleus and throughout the cytosol. In contrast, proteasome subunit C2, which is present in all proteasomes, was found to be evenly distributed throughout the cytoplasm and in the nucleus, as was the delta subunit, which is replaced by LMP2 in immunoproteasomes. c-Interferon increased the level of immunoproteasomes, but had no effect on their distribution. Our results provide the ®rst direct evidence that immunoproteasomes are strongly enriched at the endoplasmic reticulum, where they may be located close to the TAP transporter to provide efficient transport of peptides into the lumen of the endoplasmic recticulum for association with MHC class I molecules."

[studyforhope]

The cells with just integrated surface antigen production should indeed still be recognized by the class I epitopes located in the hbsag. There  are at least 3 class i epitopes of decent binding strength in the surface protein.
There are two problems however;

A. Due to the lack of extracellular infection signals the expression of immunoproteasomes will be much less than in regular infected cells.

B. The surface antigen is not a good antigen for class I presentation, since it is basically a membrane protein produced in the ER membrane and only by some mechanism shuttling back some of hbsag breakdown products from the ER lumen to the cytosol  a proper proteasome processing to the immunoactivating peptides will be possible which will then be transported to the cell membane fgastened to MHC class i complexes.

this is totally different for the e antigen that has a primary presence in the cytosol, just as the core peptides, except at a much higher concentration and therefore a higher final density of loaded MHC peptide complexes ready for presentation to the cognate cd8 Tcell receptor. Furthermore, an intact core 18 to 27 peptide has a much higher affinity for the Tcell receptor, making it the ideal Tcell attractor and activator. Thats how the acute cases get mainly cured, the single superpower core epitope, also  present on the e antigen at high levels in the cytosol.

[StephenCastlecrag]

There were high hopes that core inhibitor can be a monotherapy for HBV, not only because of its ability to inhibit production of new Dane particles in the manner you describe, but also due to core protein's ability to influence cccDNA. However, BAY 41-4109 was discontinued, its successor, GLS4 went to a phase II in China but results were never announced. NVR 3-778 is prpgressing, but  Assembly Bioscience, whose  Dr. Zlotnick, is the leading expert on CpAMs, has yet to announce a CpAM drug candidate.

It is hoped that CpAMs mono or in combination of existing NUCs can reduce HBV replication to "zero", stopping both internal and external sourced refurbishment of the cccDNA pool. As Arrowhead argued that natural depletion of cccDNA due to liver cells turnover should be significant, it should then be a race to the bottom, of cccDNA pool.
Now this seems to me to be almost a cure, despite integrated hbvdna (extent in human  is yet to be proven) producing HBsAg which is just a protein, even it though it may prevent the use of HBsAb as a means of viral control.
As HBsAg is still being produced in liver cells with integrated hbvdna, shouldn't these cells still be recognised by T cells with the appropriate epitope?

[studyforhope]

No, nucs never dry up the production of new virions to completion, that would actually be a very good thing, because then there would be no more internal reinfection, just like with a perfect entry inhibitor and the infection would slowly heal by elimination of infected cells.
But the new paradigm of integrated hbsag DNA causes this idea to be even less likely to be of realistic content. These integrated cells will not slowly die off, but participate in the liver replenishment and this way the surface antigen levels will not go to zero, making seroconversion to an effective anti hbs antibody impossible.  Without a good anti hbsag level, therapy has to be continued, since otherwise any tiny remnant of the infection will spread again.

[needadvicewithhep]

On some level it makes nucs sound like a poisoned challice.

If lets say for example someone had taken nucs for 3years you reckon it may force them to completely dry up?

[studyforhope]

By reducing the amount of Dane particles - virions - produced, the local dendritic cells in the liver will see less of these and this is an important part of the immune and Tcell activating mechanism. With high viral loads, there is to much activation, so much, that the constant overactivation exhaust the available Tcell clones and this leads to tolerance.

it is well known in immunology that the antigen levels has to be within a certain range to elicit effective responses. To much causes exhaustion ( thats why the long term nucs can help to restore a certain Tcell reactivity)  too little causes lack of activating incidents at the dendritic cell level.
On nucs there are still some virions produced, but if they dry up almost completely in the combo with capsid inhibitors, we might just see too little activity. Good for the liver in the short run, but maybe no more effective real removal of infected cells and no stopping of therapy is possible.

[needadvicewithhep]

Just to clarify on part of what you said

NUCS block immune removal process??

[studyforhope]

Inhibiting capsid formation is indeed a fascinating approach. It is the potential for full synergy with antivirals to block de novo virion formaton that makes this quite interesting.

Formed capsids are a prerequisit to begin the synthesis iof the DNA minus strand onthe inside of the still partially open capsids, later upon complete closure, the plus strand is synthesized by the same viral polymerase. At this stage the intracapsid supply of nucleotide presursors typically becomes too low to complete the plus strand, thus we have the famous gap in the plus strand of mature HBV virions.

But the important point here is that any log capsid reduction will directly synergize with an inhibitory synthesis constant generated by the action of the polymerase inhibitors. So we can basically multiply the synthesis reduction factor by the capsids with synthesis reduction by the polymerase inhibitors.

So if the reduction is 100 fold by the capsid inhibitors as in this study with the high dose then in combo with eg tenofovir we will have another factor of approx 300 in the output of virions from that cell, for a total of about 30000 fold synthesis reduction.

Note that this will not directly reduce the surface antigen production, maybe after a while as a secondary effect of preventing the cccDNA replenishment by the internal core to nucleus pathway.
Also reinfection might be reduced to such an extent so as to limit the daily respreading of the virus, but that is still a big if, since so little reinfection is necessary to replenish removed cells. A combination of tenofovir and Myrcludex, even at higher dose, was not capable of blocking a slow repopulation of the liver with infected cells.

Like any virus component blocking therapy, we might see a reduction in inflammation but  also in the immune removal mechanism that depend on the availability of signals from the presence of viral products, at the cell and from secreted virions.

What remains to be seen is what true side effects the required high daily dose of 1200mg might have once this is applied over longer periods of time. There  are little clues as to what class of compounds are used for this Novira drug.