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Arrowhead Presents Data Showing 99% Target Knockdown in ....
Exciting development:
Arrowhead Presents Data Showing 99% Target Knockdown in Monkeys Without Toxicity Using Subcutaneous Formulation of Dynamic Polyconjugate siRNA Delivery System
PASADENA, Calif.--(BUSINESS WIRE)-- Arrowhead Research Corporation (NAS: ARWR) , a targeted therapeutics company, announced that David Lewis, Ph.D., Vice President Biology and Site Head of its Madison, WI research and development facility will present data today at the 8th Annual Meeting of the Oligonucleotide Therapeutics Society in Boston. The oral presentation titled, "Dynamic PolyConjugate (DPC) technology for Targeted Delivery of siRNA," describes advancement of a new subcutaneous formulation of the company's DPC delivery system. Data from new studies in mice and non-human primates show high levels of target gene knockdown at very low doses with no toxicity. Dr. Lewis will also present data on the drug candidate ARC-520 against chronic hepatitis B virus (HBV) infection.
"The subcutaneous DPCs have shown striking levels of target gene knockdown, which we are pleased to have the opportunity to discuss at the OTS meeting," said Bruce D. Given, M.D., COO and Head of R&D for Arrowhead. "Subcutaneous delivery is preferable for some indications but the high doses of siRNA required to achieve meaningful knockdown have been prohibitive. We believe the unprecedented efficiency of this DPC formulation opens up many opportunities for Arrowhead and could represent a leap forward for the RNAi therapeutics field."
Dr. Lewis' presentation illustrates the efficacy of DPCs formulated for subcutaneous administration using Arrowhead's latest proprietary polymer masking technology. Using DPCs to deliver siRNA, high-level target gene knockdown is observed at low siRNA doses without toxicity in rodents and non-human primates. Arrowhead studies have shown knockdown of 99% in monkeys after a single injection of 1 mg/kg, >90% at 0.5 mg/kg, and 80% in mice at 0.05 mg/kg. PK and biodistribution studies indicate that the new masking technology is highly stable, allowing for maximal bioavailability and long circulation times. Arrowhead is developing this formulation for use in multiple therapeutic areas including oncology.
Dr. Lewis will also present data on Arrowhead's clinical candidate, ARC-520, for the treatment of chronic hepatitis B. According to the World Health Organization, some 360 million people, or 5% of the world's population, suffer from chronic hepatitis B and are at significant risk for development of liver cirrhosis and hepatocellular carcinoma. Existing drugs for the treatment of chronic hepatitis B seldom produce a functional cure and can cause significant side-effects.
In mouse models of HBV infection, a single injection of ARC-520 containing NAG-polymer and chol-siRNAs targeting conserved regions of the HBV transcripts resulted in multi-log reductions in circulating viral antigens and HBV DNA, and dramatically reduced HBV RNA and DNA replicative intermediates in the liver. The duration of effect is unprecedented, with HBsAg reduced >99% for one month following a single injection. These results suggest that ARC-520 holds great promise as a new therapeutic modality for patients chronically infected with HBV.
About Arrowhead Research Corporation
Arrowhead Research Corporation is a clinical stage targeted therapeutics company with development programs in oncology, obesity, and chronic hepatitis B virus infection. The company is leveraging its platform technologies to design and develop peptide-drug conjugates (PDCs) that specifically home to cell types of interest while sparing off-target tissues, create targeted drugs based on the gene silencing RNA interference (RNAi) mechanism, and work with partners to create improved versions of traditional small molecule drugs.
Arrowhead Presents Data Showing 99% Target Knockdown in Monkeys Without Toxicity Using Subcutaneous Formulation of Dynamic Polyconjugate siRNA Delivery System
PASADENA, Calif.--(BUSINESS WIRE)-- Arrowhead Research Corporation (NAS: ARWR) , a targeted therapeutics company, announced that David Lewis, Ph.D., Vice President Biology and Site Head of its Madison, WI research and development facility will present data today at the 8th Annual Meeting of the Oligonucleotide Therapeutics Society in Boston. The oral presentation titled, "Dynamic PolyConjugate (DPC) technology for Targeted Delivery of siRNA," describes advancement of a new subcutaneous formulation of the company's DPC delivery system. Data from new studies in mice and non-human primates show high levels of target gene knockdown at very low doses with no toxicity. Dr. Lewis will also present data on the drug candidate ARC-520 against chronic hepatitis B virus (HBV) infection.
"The subcutaneous DPCs have shown striking levels of target gene knockdown, which we are pleased to have the opportunity to discuss at the OTS meeting," said Bruce D. Given, M.D., COO and Head of R&D for Arrowhead. "Subcutaneous delivery is preferable for some indications but the high doses of siRNA required to achieve meaningful knockdown have been prohibitive. We believe the unprecedented efficiency of this DPC formulation opens up many opportunities for Arrowhead and could represent a leap forward for the RNAi therapeutics field."
Dr. Lewis' presentation illustrates the efficacy of DPCs formulated for subcutaneous administration using Arrowhead's latest proprietary polymer masking technology. Using DPCs to deliver siRNA, high-level target gene knockdown is observed at low siRNA doses without toxicity in rodents and non-human primates. Arrowhead studies have shown knockdown of 99% in monkeys after a single injection of 1 mg/kg, >90% at 0.5 mg/kg, and 80% in mice at 0.05 mg/kg. PK and biodistribution studies indicate that the new masking technology is highly stable, allowing for maximal bioavailability and long circulation times. Arrowhead is developing this formulation for use in multiple therapeutic areas including oncology.
Dr. Lewis will also present data on Arrowhead's clinical candidate, ARC-520, for the treatment of chronic hepatitis B. According to the World Health Organization, some 360 million people, or 5% of the world's population, suffer from chronic hepatitis B and are at significant risk for development of liver cirrhosis and hepatocellular carcinoma. Existing drugs for the treatment of chronic hepatitis B seldom produce a functional cure and can cause significant side-effects.
In mouse models of HBV infection, a single injection of ARC-520 containing NAG-polymer and chol-siRNAs targeting conserved regions of the HBV transcripts resulted in multi-log reductions in circulating viral antigens and HBV DNA, and dramatically reduced HBV RNA and DNA replicative intermediates in the liver. The duration of effect is unprecedented, with HBsAg reduced >99% for one month following a single injection. These results suggest that ARC-520 holds great promise as a new therapeutic modality for patients chronically infected with HBV.
About Arrowhead Research Corporation
Arrowhead Research Corporation is a clinical stage targeted therapeutics company with development programs in oncology, obesity, and chronic hepatitis B virus infection. The company is leveraging its platform technologies to design and develop peptide-drug conjugates (PDCs) that specifically home to cell types of interest while sparing off-target tissues, create targeted drugs based on the gene silencing RNA interference (RNAi) mechanism, and work with partners to create improved versions of traditional small molecule drugs.
Thank you first of all for you contribution to this community.
there is a theory that if ALT rises in CHB patients with undetectable DNA and low hbsAg quantity less than 2000 IU, it could be a sign of hbsag seroconversion and hbv resolution. This theory does not seem to correspond to what you have just explained. Could you please comment on this also?
there is a theory that if ALT rises in CHB patients with undetectable DNA and low hbsAg quantity less than 2000 IU, it could be a sign of hbsag seroconversion and hbv resolution. This theory does not seem to correspond to what you have just explained. Could you please comment on this also?
I would assume that Replicor just like all other companies that try to develop new therapies are simply bound and forced by the strict governmental regulations that confine every detail of such developments. If they would ignore these regulations, they would be stopped blocked and punished. Before you can even start a phase I trial in the USA or Canada you will have to obtain prior approval based on numerous criteria of eg animal model toxicity tests, proof on concept studies etc etc. Giving a drug to a patient outside of approved programs/trials is strictly forbidden and would result in the closure of the operation. The morals and ethics of these regulations are certainly up for discussion, but I do not see a pragmatical and useful outcome of these at this moment.
ALT elevations in e-Ag neg patients are the result of increased general inflammation in the liver, caused by the presence of an activated infiltrate of macrophages, dendritic cells, NK and NKT cell, mostly T-helper cells but also CTLs, B-cells and some more esoteric members.
The activation of this cellular infiltrate is fueled by the uptake and recognition of virions by local antigen presenting cells like dendritic cells and macrophages, that will in turn specifically activate class II recognizing T-cell receptors on the surface of T-helper cells. That will cause these antigen specific T-helper cells to proliferate and to secrete a variety of proinflammatory cytokines as well as activate other cellular components by direct cell to cell contact. This leads to a cascade of escalating inflammation with apoptosis and sometimes necrosis of non infected hepatocytes as well ( the so called bystander effect).
Thus class II epitopes do not cause a specific attack on infected cells as is the case with class I hepatocyte surface presented epitopes, but rather an inefficient general inflammatory state, that is unable to fully control the processes of viral transcription and replication and it will rarely result in the noncytolytic removal of cccDNA from an infected cell.
It also results in the collateral activation of stellate cells that transform to myofibroblasts and start to produce collagen fibers, hence fibrosis.
Dramatic reduction of vririon production will reduce this local immune activating effect of virions , will reduce ALT levels and curb and even reverse fibrosis. This is the main reason that antivirals broadly mitigate HBV liver disease.
An additional class II activating mechanism, besides virion production, is the phagocytosis and workup of cellular debris from dying hepatocytes, where the viral components contained in this debris will also be digested to peptides and presented/transported to the MHC class II presenting membrane protein complexes on the surface of dendritic cells and macrophages, activating epitope specific T-helper cells that participate in the above detailled scenario.
Moreover, independent of the presence of specific HBV epitopes, cellular debris activates innate responses, that will further contribute to the inflammation propagation. This is also the case in noninfectious metabolic stress hepatitis NAFLD and NASH and alcoholic hepatitis.
Generally only the epitopes contained in the core and surface antigen cause a major contribution in either class I or class II epitope presentation, since the absolute amounts of protein in the X and the polymerase expression is to small to matter. At best a minor contribution of these can be expected. Frank Chisaris experiments with the passive transfer of epitope specific T lymphocytes have shown this quite elegantly, where the transfer of polymerase specific CTLs had no or only minor impact on the infected liver in the target animals. Core specific CTLs on the other hand cause a massive increase in inflammation and apoptosis in the target liver.
Note that the both the class I and II surface epitopes do not participate in these processes simply because the overwhelming decoy production of this antigen overactivates surface antigen specific Tcells at bodywide locations and leads to dramatic exhaustion and therefore "tolerance".This is the strategy of HBV to specifically eliminate the combined T-cell responses to all of the potential epitopes selectively to this most abundant viral protein. For HLA A2 patients there are up to 5 class I epitopes in the surface protein, of varying effectiveness once presented. A mutation in critical amino acids in these epitopes will partly or completely deactivate this epitopes. Thus caution is required once these epitopes become the major attack points, to avoid breeding an unresponsive HBV population for this last resort and reserve of specific immunological attack.
The activation of this cellular infiltrate is fueled by the uptake and recognition of virions by local antigen presenting cells like dendritic cells and macrophages, that will in turn specifically activate class II recognizing T-cell receptors on the surface of T-helper cells. That will cause these antigen specific T-helper cells to proliferate and to secrete a variety of proinflammatory cytokines as well as activate other cellular components by direct cell to cell contact. This leads to a cascade of escalating inflammation with apoptosis and sometimes necrosis of non infected hepatocytes as well ( the so called bystander effect).
Thus class II epitopes do not cause a specific attack on infected cells as is the case with class I hepatocyte surface presented epitopes, but rather an inefficient general inflammatory state, that is unable to fully control the processes of viral transcription and replication and it will rarely result in the noncytolytic removal of cccDNA from an infected cell.
It also results in the collateral activation of stellate cells that transform to myofibroblasts and start to produce collagen fibers, hence fibrosis.
Dramatic reduction of vririon production will reduce this local immune activating effect of virions , will reduce ALT levels and curb and even reverse fibrosis. This is the main reason that antivirals broadly mitigate HBV liver disease.
An additional class II activating mechanism, besides virion production, is the phagocytosis and workup of cellular debris from dying hepatocytes, where the viral components contained in this debris will also be digested to peptides and presented/transported to the MHC class II presenting membrane protein complexes on the surface of dendritic cells and macrophages, activating epitope specific T-helper cells that participate in the above detailled scenario.
Moreover, independent of the presence of specific HBV epitopes, cellular debris activates innate responses, that will further contribute to the inflammation propagation. This is also the case in noninfectious metabolic stress hepatitis NAFLD and NASH and alcoholic hepatitis.
Generally only the epitopes contained in the core and surface antigen cause a major contribution in either class I or class II epitope presentation, since the absolute amounts of protein in the X and the polymerase expression is to small to matter. At best a minor contribution of these can be expected. Frank Chisaris experiments with the passive transfer of epitope specific T lymphocytes have shown this quite elegantly, where the transfer of polymerase specific CTLs had no or only minor impact on the infected liver in the target animals. Core specific CTLs on the other hand cause a massive increase in inflammation and apoptosis in the target liver.
Note that the both the class I and II surface epitopes do not participate in these processes simply because the overwhelming decoy production of this antigen overactivates surface antigen specific Tcells at bodywide locations and leads to dramatic exhaustion and therefore "tolerance".This is the strategy of HBV to specifically eliminate the combined T-cell responses to all of the potential epitopes selectively to this most abundant viral protein. For HLA A2 patients there are up to 5 class I epitopes in the surface protein, of varying effectiveness once presented. A mutation in critical amino acids in these epitopes will partly or completely deactivate this epitopes. Thus caution is required once these epitopes become the major attack points, to avoid breeding an unresponsive HBV population for this last resort and reserve of specific immunological attack.
For a better understanding, can you shed some light on what causes elevated ALT levels in e-negative patients CHB? Since the surface antigen keeps Tcells busy, is it the virions that the immune system attacks? And is that the reason why antivirals are effective in reduction of ALT, inflammation, etc?
I know you mentioned it one of the above posts, but I wanted to link to stephencastlecrag point regarding the core and x epitopes. Or is it a combo of all the above that essentially light up the "tree" but only as weaker class II epitopes that you mentioned are prone to produce lots of inflamation?
I know you mentioned it one of the above posts, but I wanted to link to stephencastlecrag point regarding the core and x epitopes. Or is it a combo of all the above that essentially light up the "tree" but only as weaker class II epitopes that you mentioned are prone to produce lots of inflamation?
"a financial sponser powerful to move this incredible promising approach along will be found"
It will be found, if they are willing to work with people... If that is the only reason that is stopping them then this can be fixed.
It would be interesting to hear a number $ on what it takes per patient they think to get this project going.
It will be found, if they are willing to work with people... If that is the only reason that is stopping them then this can be fixed.
It would be interesting to hear a number $ on what it takes per patient they think to get this project going.
"An intravenous infusion lasting many hours once a week is not very feasable for a larger patient population, most doctors or hospitals would charge substantially for this service."
Yes but they could start giving it to people first that are willing to pay all those fees. Then those that become cured, share this info, and get governments and the public media to realize what is available. It can take off like a wild fire. This will perhaps get another company somewhere to work with them and develop injectable delivery of this drug.
treatment cost should not be an issue here. It is to bad that human life now measured in terms of money.. Besides fees for infusion therapy they charge in the US for example differs greatly with other countries. Especially with those that are not in the west. So why not set up camp there...
Yes but they could start giving it to people first that are willing to pay all those fees. Then those that become cured, share this info, and get governments and the public media to realize what is available. It can take off like a wild fire. This will perhaps get another company somewhere to work with them and develop injectable delivery of this drug.
treatment cost should not be an issue here. It is to bad that human life now measured in terms of money.. Besides fees for infusion therapy they charge in the US for example differs greatly with other countries. Especially with those that are not in the west. So why not set up camp there...
"You have got to be more positive dude! They are all moving, but they are limitations because it take time to determine toxicity and all the other stuff that can happen. GS-9620 is in phase I (or II since they are treating infected subjects), Myrcludex B is in being tried on HBV patients. Rep 9AC' is being tried on patients in combination with other drugs as presented the other day. ARC-520 is moving to IND next year and clinical trials after that. Trials will be coming and you'll have an opportunity to participate if you intend to do so. We're all in the same boat, but we got to make sure that the drugs work first in a statistically significant way. Until thorough studies are done, we can’t be sure"
I am trying to be positive but there is nothing to be positive about other then the Myrcludex attempt for wider clinical trials on a more or less good schedule.. I just hope they approve it in Russia next week so everyone can get help.
GS9620 trial did not take me :(. Turns out in the end I was on the wrong drug. Although they promised. And I waited. When it came to it I was told I have to be 3 months on TDF in order to enter. Now, what do you call this? Responsible people other there, good doctors? I say it *****!!!
next Replicor people.. Did they come to this forum, did they reply to us as to how we can get the drug? Again NO.. So what is all this secrecy about these medications? HBV treatment is what a classified military project now?
So now I am supposed to be excited about ARC-520... which is what years away? Of course it is something to look forward to.. but till these companies start acting more responsibly and think that there are 300 million people some of which with are in advance stages of liver disease and are in need of an immediate help. Till then all this info can be treated as marketing.
HBV is a hurricane that destroys the liver. It is a human disaster. And these companies have all these agents available now, and they say legally they can't use them. Does that makes sense? Staying alive with hbv for 3-5 years is a challenge. Most of us live in 6 months increments. Do they know what it is it like?
it is goes kinda like this in comparison. If people that were damaged by the hurricane on the east coast of the US, were told > but Oh well you have to wait 3-4 years while we sort things out here legally and see if it really works. Replicor stuff cleared HBV in 10 of 12 people in 7-12 weeks. And that is still cannot be called a cure. Or an unfinished drug.
Toxicity they worry about your say? What about toxicity from taking antivirals indefinitely, anybody worries about this? They don't even look at available HIV treatment data what nucs do.. why antivirals cause high blood pressure and what can be done to reverse it?
The way I see it all the info they release about new drugs does not make us infected warm until these companies take a moral responsibility and start doing something that can save people now. Until they come here, their CEO's or press managers and have a dialog with the people. So red tape they face today in western countries can be lifted. And it can be lifted. Once there are enough voices.
There is 300 million of us, if we start making our voices heard on the internet - the public will force companies to makes changes. And make make doctors act more responsibly. I think we need the media to get involved in this. So they start paying attention to us.
Some people come here to collect info for their research teams it is obvious. But we the patients can't wait. If these companies don't even bother to come here and talk to us openly that means they are don't hold us in a very high regard.
The way I see it clinical trials for us, should be done on a military type schedule. And it is doable, to conduct clinical trials, on patients making adjustment as they go along.
That is why I raise these issues... because their good is really not good enough.
I am trying to be positive but there is nothing to be positive about other then the Myrcludex attempt for wider clinical trials on a more or less good schedule.. I just hope they approve it in Russia next week so everyone can get help.
GS9620 trial did not take me :(. Turns out in the end I was on the wrong drug. Although they promised. And I waited. When it came to it I was told I have to be 3 months on TDF in order to enter. Now, what do you call this? Responsible people other there, good doctors? I say it *****!!!
next Replicor people.. Did they come to this forum, did they reply to us as to how we can get the drug? Again NO.. So what is all this secrecy about these medications? HBV treatment is what a classified military project now?
So now I am supposed to be excited about ARC-520... which is what years away? Of course it is something to look forward to.. but till these companies start acting more responsibly and think that there are 300 million people some of which with are in advance stages of liver disease and are in need of an immediate help. Till then all this info can be treated as marketing.
HBV is a hurricane that destroys the liver. It is a human disaster. And these companies have all these agents available now, and they say legally they can't use them. Does that makes sense? Staying alive with hbv for 3-5 years is a challenge. Most of us live in 6 months increments. Do they know what it is it like?
it is goes kinda like this in comparison. If people that were damaged by the hurricane on the east coast of the US, were told > but Oh well you have to wait 3-4 years while we sort things out here legally and see if it really works. Replicor stuff cleared HBV in 10 of 12 people in 7-12 weeks. And that is still cannot be called a cure. Or an unfinished drug.
Toxicity they worry about your say? What about toxicity from taking antivirals indefinitely, anybody worries about this? They don't even look at available HIV treatment data what nucs do.. why antivirals cause high blood pressure and what can be done to reverse it?
The way I see it all the info they release about new drugs does not make us infected warm until these companies take a moral responsibility and start doing something that can save people now. Until they come here, their CEO's or press managers and have a dialog with the people. So red tape they face today in western countries can be lifted. And it can be lifted. Once there are enough voices.
There is 300 million of us, if we start making our voices heard on the internet - the public will force companies to makes changes. And make make doctors act more responsibly. I think we need the media to get involved in this. So they start paying attention to us.
Some people come here to collect info for their research teams it is obvious. But we the patients can't wait. If these companies don't even bother to come here and talk to us openly that means they are don't hold us in a very high regard.
The way I see it clinical trials for us, should be done on a military type schedule. And it is doable, to conduct clinical trials, on patients making adjustment as they go along.
That is why I raise these issues... because their good is really not good enough.
This concept has some chance to work. Provided enough suppression time is given, T cell recovery is possible, initially without sufficient targets to find.
Once you let the full synthesis start again, the targets become visible. There is one big problem however: the newly formed surface antigen will flood the body again and will be presented by all the macrophages and dendritic cells all over, leading to a new distraction, exhaustion and tolerization of the specific T cells. Remember the removal of infected cells takes time, 30 to 40 weeks with rep9ac.
At the start it might be better to have a viral load, btw, since virions are the best immune stimulators. Thus pretreating rep9ac with an antiviral might reduce immun vigor. On the other hand, starting with a high viral load might also lead to surface antigen epitope specific escape mutations, leaving behind a resistant population. The perfect answer to this dilemma is to simultaneously start rep9ac and Myrcludex, then existing mutations cannot spread and you can follow the vl as a clean indicator of infected cell removal.
Once you let the full synthesis start again, the targets become visible. There is one big problem however: the newly formed surface antigen will flood the body again and will be presented by all the macrophages and dendritic cells all over, leading to a new distraction, exhaustion and tolerization of the specific T cells. Remember the removal of infected cells takes time, 30 to 40 weeks with rep9ac.
At the start it might be better to have a viral load, btw, since virions are the best immune stimulators. Thus pretreating rep9ac with an antiviral might reduce immun vigor. On the other hand, starting with a high viral load might also lead to surface antigen epitope specific escape mutations, leaving behind a resistant population. The perfect answer to this dilemma is to simultaneously start rep9ac and Myrcludex, then existing mutations cannot spread and you can follow the vl as a clean indicator of infected cell removal.
Make sense to me. I wonder how the X protein is made available to the antigen presenting cells?
Well this leaves one final try. So ARC-520 can behave like oral antivirals in reducing viral load to undetectable with the added bonus that it can also reduce serum HBsAg. This will remove tolerance and restore HBV specific Tcells to full functionality. To overcome the problem of lack of Xmass tree lights on the surface of infected hepatocytes as these lights have been switched off, we can stop all treatments, thus allowing the virus to replicate again and turning on the Xmas tree lights again. But this tine, our Tcells are ready to strike back? Will this work? [This concept is being tested in a clinical trial in patients long term suppression of viral replication by Tenofovir]
Well this leaves one final try. So ARC-520 can behave like oral antivirals in reducing viral load to undetectable with the added bonus that it can also reduce serum HBsAg. This will remove tolerance and restore HBV specific Tcells to full functionality. To overcome the problem of lack of Xmass tree lights on the surface of infected hepatocytes as these lights have been switched off, we can stop all treatments, thus allowing the virus to replicate again and turning on the Xmas tree lights again. But this tine, our Tcells are ready to strike back? Will this work? [This concept is being tested in a clinical trial in patients long term suppression of viral replication by Tenofovir]
The display of the x gene epitopes are expected to be of low efficiency, since the x protein is produced only in small amounts. Speculations of x directed Tcell responses are floating around from time to time however , in low quality publications.
The spontaneous and antiviral induced small number of surface antigen converters might well be converted due to the virtue of a remnant anti core Tcell response, possibly also due to variant HLA types that can use other classI core/eAg epitopes.
. As long as the surface antigen itself is high or even moderately high there is no way it can contribute to the Tcell response, due to its tolerizing effect. Thus these types of rare conversions are NOT a model for the replicor effect, where the surface antigen is drastically reduced to zero or almost zero by the drugs effect in the hepatocyte. Then the above mentioned effects will start up.
I want to add, that the surface antigen due to its ubiquitous engagement of dendritic cells and macrophages, also has an unspecific inhibitory effect on the immune response against unrelated HBV antigens. To put it simple, it keeps the presenting cells busy with crap. The respective papers typically show, that a relatively high concentration of surface antigen is needed to show this effect convincingly, thus the famous below 1000iU might be a threshold where this effect will substantially diminish, since it seems to be a mass effect, maybe coupled with a downregulatory effect of a more specific kind. Such an effect was more convincingly shown for the e-antigen.
The spontaneous and antiviral induced small number of surface antigen converters might well be converted due to the virtue of a remnant anti core Tcell response, possibly also due to variant HLA types that can use other classI core/eAg epitopes.
. As long as the surface antigen itself is high or even moderately high there is no way it can contribute to the Tcell response, due to its tolerizing effect. Thus these types of rare conversions are NOT a model for the replicor effect, where the surface antigen is drastically reduced to zero or almost zero by the drugs effect in the hepatocyte. Then the above mentioned effects will start up.
I want to add, that the surface antigen due to its ubiquitous engagement of dendritic cells and macrophages, also has an unspecific inhibitory effect on the immune response against unrelated HBV antigens. To put it simple, it keeps the presenting cells busy with crap. The respective papers typically show, that a relatively high concentration of surface antigen is needed to show this effect convincingly, thus the famous below 1000iU might be a threshold where this effect will substantially diminish, since it seems to be a mass effect, maybe coupled with a downregulatory effect of a more specific kind. Such an effect was more convincingly shown for the e-antigen.
I think that replicor tries to advance to a subcutaneous formulation, away from the intravenous infusions that they needed to use up to this point with both generations of their DNA preparations. An intravenous infusion lasting many hours once a week is not very feasable for a larger patient population, most doctors or hospitals would charge substantially for this service. The second contribution at the above oligonucleotide conference that stephencastlecrag saw might be a further important step in the direction of easier application, since the CaCl preparation will likely remove many of the unpleasant side effects hat make thus far multihours infusions necessary. Thus the final mode of application and subtype of the antigen release blocker to be used with greatest ease needs to be determined first, before larger scale trials and the huge capital investment for a larger phase II trial can be done. Hopefully, once the formulation has been optimized, a financial sponser powerful to move this incredible promising approach along will be found.
What a bummer. LOL. Thanks for the lesson..
I read that HBV specific Tcells response to HBV core, envelope, and X proteins. So how good is the display of X protein epitope by MHC Class I molecules.
In a paper by some Chinese scientists, they observed that "however the T cell responses in the seroclearance[S seroconversion in a group of 14 Chinese patients following antiviral treatment] group were almost exclusively to core antigens. Only a small number of low level response to envelope gene antigens were detected." So the scientists stated; "Thus our data did not provide clues to the cause of HBsAg seroconversion in this group of subjects." So surface antigen specific Tcells may not be that important in clearing the virus, casting doubt at the same time in understanding how REP9AC actually work.
Just my opinion as someone who does not know what he is talking about.
I read that HBV specific Tcells response to HBV core, envelope, and X proteins. So how good is the display of X protein epitope by MHC Class I molecules.
In a paper by some Chinese scientists, they observed that "however the T cell responses in the seroclearance[S seroconversion in a group of 14 Chinese patients following antiviral treatment] group were almost exclusively to core antigens. Only a small number of low level response to envelope gene antigens were detected." So the scientists stated; "Thus our data did not provide clues to the cause of HBsAg seroconversion in this group of subjects." So surface antigen specific Tcells may not be that important in clearing the virus, casting doubt at the same time in understanding how REP9AC actually work.
Just my opinion as someone who does not know what he is talking about.
Your knowledge on the subject is immense. Thanks for your time again. Your explanation makes sense logical sense, although I don't know much about this stuff. It seems that Replicor has the perfect model.
If I can ask you one additional question/opinion. Do you know of any technical reasons/flaws why they aren't going full speed on a phase II or similar? Obviously clinical trial time aside, it seems that their approach/agent has been around since 2010. Enough time to go further I would think, although their studies seem to be in very small groups.
If I can ask you one additional question/opinion. Do you know of any technical reasons/flaws why they aren't going full speed on a phase II or similar? Obviously clinical trial time aside, it seems that their approach/agent has been around since 2010. Enough time to go further I would think, although their studies seem to be in very small groups.
Chimpanzes can rarely be used for this. If they use chimeric mice, which are in general a good model with the human liver partially present in the mouse liver, that can indeed be infected with HBV, there is no immune response and these aspects. like eg immune escape epitope adaptation can not be tested in these models.
I am afraid that the iRNA concept might lead only to a lowering of the surface antigen without the rapid DNA clearance that we see with rep9ac.And that this lack of the truly desired effect will only come out in the human studies.
This is the beauty of the Replicor model: The surface antigen is produced at full swing, but does not get out of the cell, since the delicate particle formation is inhibited by the amphipathic phoshorothioate DNA stretch.
Thus the immune system is not awash with surface antigen, releasing the state of tolerance , but the infected hepatic cells are lighting up like christmas trees with surface antigen epitopes...
It also warrants mentioning, that the hepatocytes with partial integration of the surface antigen gene only, into the human hepatocyte genome, will also be eliminated this way. This is important, because these integrated clones are often the precursor cells for later hepatocellular carcinoma.
Again, the surface antigen supression as such is just the prelude for the truly important process of Tcell awakening and attack, most importantly of the class I cytotoxic Tcell kind, that lyses infected hepatocytes directly and at the same time produces very high very local gamma Interferon bursts that are able to clear neighboring cells of the HBV minichromosome without cell lysis. This noncytolytic clearance is likely the more important process. Furthermore this local gamma interferon effect works without a high degree of collateral inflammation. The rep9ac patients have only mild ALT spikes.
I am afraid that the iRNA concept might lead only to a lowering of the surface antigen without the rapid DNA clearance that we see with rep9ac.And that this lack of the truly desired effect will only come out in the human studies.
This is the beauty of the Replicor model: The surface antigen is produced at full swing, but does not get out of the cell, since the delicate particle formation is inhibited by the amphipathic phoshorothioate DNA stretch.
Thus the immune system is not awash with surface antigen, releasing the state of tolerance , but the infected hepatic cells are lighting up like christmas trees with surface antigen epitopes...
It also warrants mentioning, that the hepatocytes with partial integration of the surface antigen gene only, into the human hepatocyte genome, will also be eliminated this way. This is important, because these integrated clones are often the precursor cells for later hepatocellular carcinoma.
Again, the surface antigen supression as such is just the prelude for the truly important process of Tcell awakening and attack, most importantly of the class I cytotoxic Tcell kind, that lyses infected hepatocytes directly and at the same time produces very high very local gamma Interferon bursts that are able to clear neighboring cells of the HBV minichromosome without cell lysis. This noncytolytic clearance is likely the more important process. Furthermore this local gamma interferon effect works without a high degree of collateral inflammation. The rep9ac patients have only mild ALT spikes.
Very, very interesting. Thanks again. Tough little bugger this HBV is. Basically, if I got this correctly, the virus goes into a "stealth" mode and the immune system has no/very little chance of clearing it. I wonder if they have published their studies on mice/primates and if they showed a relapse after the injection stopped? That may be able to confirm your fears and the Achilles heel for the approach.
The problem with the core antigen epitopes "visibility" is twofold;
1. It is mainly the cytosolic e-antigen that produces the critical "core epitopes". Core itself is not produced in numbers large enough to supply the epitope presentation on the hepatocyte MHCs.
Thats why the virus makes all the effort ( precore and core promotor mutations) to remove/reduce the e-antigen expression once the e-antigen became to small to block the Tcells in the periphery and the war starts to hit home for HBV. A total change in strategy indeed and thats why we have e-antigen negative hepatitis B.
2. The core has one single lousy, but as such very potent, classI epitope, the 18 -27 AA position, in HLA A2 patients. It has indeed a super high affinity to MHC and the Tcell receptor and is the reason that most acute HBV cures quickly. The "Cytel therapeutic vaccine" was based on that insight. It did not work very well, however.
The reason is that this epitope adaptively mutates and then only class II Tcell epitopes are available from the core, way less effective and prone to produce a lot of inflammation with little true anti cccDNA effect.
Also it generates that effect as a result of dendritic and macrophage uptake of virions containing the core, not directly on the infected cell. Thats why supressing viral production by antivirals is effective in reducing the ALt and inflammation and fibrosis.
Thus there is not to much hope that core epitopes will substantially contribute to clearance in e-antigen negative patients, no class I contribution can be expected. Maybe a few low affinity HLA allele epitopes might jump in. (the affinity coefficients are different by huge factors).
All the burden is on the surface class I epitopes. They are unmutated, unaltered, since the virus never needed to do that, thre was no pressure to do so.
Now with a surface antigen particle formation suppressor, that attack on a limited functional epitope reperatoire comes in play, for the first time. This is the big unharvested reserve. If you let that mutate it will be over for final success, so care is needed to not let that happen.
Also, a high surface epitope presence on the surface of the hepatocytes will help the dynamic of this process almost linearly. Thats why I am afraid that the Arrowhead approach might fail, since it cuts the production of the surface protein at the transcription level.
1. It is mainly the cytosolic e-antigen that produces the critical "core epitopes". Core itself is not produced in numbers large enough to supply the epitope presentation on the hepatocyte MHCs.
Thats why the virus makes all the effort ( precore and core promotor mutations) to remove/reduce the e-antigen expression once the e-antigen became to small to block the Tcells in the periphery and the war starts to hit home for HBV. A total change in strategy indeed and thats why we have e-antigen negative hepatitis B.
2. The core has one single lousy, but as such very potent, classI epitope, the 18 -27 AA position, in HLA A2 patients. It has indeed a super high affinity to MHC and the Tcell receptor and is the reason that most acute HBV cures quickly. The "Cytel therapeutic vaccine" was based on that insight. It did not work very well, however.
The reason is that this epitope adaptively mutates and then only class II Tcell epitopes are available from the core, way less effective and prone to produce a lot of inflammation with little true anti cccDNA effect.
Also it generates that effect as a result of dendritic and macrophage uptake of virions containing the core, not directly on the infected cell. Thats why supressing viral production by antivirals is effective in reducing the ALt and inflammation and fibrosis.
Thus there is not to much hope that core epitopes will substantially contribute to clearance in e-antigen negative patients, no class I contribution can be expected. Maybe a few low affinity HLA allele epitopes might jump in. (the affinity coefficients are different by huge factors).
All the burden is on the surface class I epitopes. They are unmutated, unaltered, since the virus never needed to do that, thre was no pressure to do so.
Now with a surface antigen particle formation suppressor, that attack on a limited functional epitope reperatoire comes in play, for the first time. This is the big unharvested reserve. If you let that mutate it will be over for final success, so care is needed to not let that happen.
Also, a high surface epitope presence on the surface of the hepatocytes will help the dynamic of this process almost linearly. Thats why I am afraid that the Arrowhead approach might fail, since it cuts the production of the surface protein at the transcription level.
Thank you. That was a great explanation and very informative. Hopefully, all will be flushed out in the clinical trials.
"So the target stays visible, which might make all the difference."
Of course! Maybe the HBcAg still being produced and its epitopes still available?
Of course! Maybe the HBcAg still being produced and its epitopes still available?
It appears that ARC-520 also reduces HBsAg >99% so there may be similarities in the immune response in absence of surface antigens? Don't know. Will find out soon enough I guess. Good to know that the use of INTFN and other boosters can help to immune control as evidenced in the Replicor study.
The supression of HbSAg down 99% by the interfering RNA construct sounds promising and could, similarly like Rep9ac, lead to a reawakening of the supressed Tcell response to the surface antigen epitopes with consequent removal of infected cells/cccDNA.
I hope it is obvious that it is not the artificial reduction of the surface antigen that matters with these treatments, This is not the same as spontaneous or IFN induced surface antigen reduction, which represent basically a reduction in cccDNA and also some immune induced transcription/translation inhibition inside infected hepatocytes (likely induced by IFN gamma and additional cytokines from the innate side).
What matters is that the blocking effect of the vast amount of secreted surface antigen is removed and opens up an unused target against HBV. Restoration of the blunted response might take some time, that might also be why replicors treatment is about 40 weeks towards a strong reduction of HBV DNA as a consequence of said mechanisms.
There is however an important difference in the Arrowhead iRNA approach and the replicor mechanism that deserves critical attention. With the iRNA, the production of the surface antigen protein is itself inhibited, leading possibly to a very low intracellular surface antigen level, with consequent low grade presentation of the epitopes derived from that limited source.
With Rep9ac the protein production is not inhibited, it is the formation of the spheric 22nm particles that is inhibited, leaving plenty, if not to much surface antigen inside the hepatocyte for MHC class1 epitope workup and presentation. So the target stays visible, which might make all the difference.
Remember why the virus activates the precore mutation; to reduce the intracellular presence of an epitope generating viral protein ( the e-antigen) to escape cd8/ CTL detection.
I hope it is obvious that it is not the artificial reduction of the surface antigen that matters with these treatments, This is not the same as spontaneous or IFN induced surface antigen reduction, which represent basically a reduction in cccDNA and also some immune induced transcription/translation inhibition inside infected hepatocytes (likely induced by IFN gamma and additional cytokines from the innate side).
What matters is that the blocking effect of the vast amount of secreted surface antigen is removed and opens up an unused target against HBV. Restoration of the blunted response might take some time, that might also be why replicors treatment is about 40 weeks towards a strong reduction of HBV DNA as a consequence of said mechanisms.
There is however an important difference in the Arrowhead iRNA approach and the replicor mechanism that deserves critical attention. With the iRNA, the production of the surface antigen protein is itself inhibited, leading possibly to a very low intracellular surface antigen level, with consequent low grade presentation of the epitopes derived from that limited source.
With Rep9ac the protein production is not inhibited, it is the formation of the spheric 22nm particles that is inhibited, leaving plenty, if not to much surface antigen inside the hepatocyte for MHC class1 epitope workup and presentation. So the target stays visible, which might make all the difference.
Remember why the virus activates the precore mutation; to reduce the intracellular presence of an epitope generating viral protein ( the e-antigen) to escape cd8/ CTL detection.
I think as HBV DNA and HBsAg are reduced, cccDNA will eventually go down, as less hepatocytes will be infected. Eventually, there should be viral clearance with sustained remission and Ab levels that are able to maintain this suppression.
I have no idea, I guess it will be by injections. I think ARC520 targets hbv antigens gene transcription and therefore should reduce viral load (and may also reduce production of HBsAg). As the cccDNA is not removed, long term treatment may be required. REP9AC' relies on the assumption that by inhibiting the release of HBsAg VSP (viral subparticles) into the blood, it will remove the suppression of our immune response which should then be able to control the virus. The use of INTFN/Thymosin to elicit production of s-antibodies may be their way to further strengthen the immune control?
You have got to be more positive dude! They are all moving, but they are limitations because it take time to determine toxicity and all the other stuff that can happen. GS-9620 is in phase I (or II since they are treating infected subjects), Myrcludex B is in being tried on HBV patients. Rep 9AC' is being tried on patients in combination with other drugs as presented the other day. ARC-520 is moving to IND next year and clinical trials after that. Trials will be coming and you'll have an opportunity to participate if you intend to do so. We're all in the same boat, but we got to make sure that the drugs work first in a statistically significant way. Until thorough studies are done, we can’t be sure.
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