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ARC520 at EASL2016-Studyforhope's comment requested
The EASL2016 abstracts are now available for download at
http://ilc-congress.eu/ilc-2016-ebooks/
The following is an abstract on ARC520. Unfortunately it makes no sense to me, what is a HbsAg clearance profile? Where do the HBsAg/HBsAb complexes come from during ARC520 treatment? Hopefully Studyforhope can help out here.
N.B. The abstract is pretty high-powered with Locarnini, Ferrari, and Gish.
FRI-144
PREDICTING HBSAG CLEARANCE RESPONSES DURING ARC-520
RNA INTERFERENCE (RNAI) THERAPY BASED ON HBSAG EPITOPE
PROFILE ANALYSIS
R. Walsh1, R. Hammond1, L. Yuen1, J. Deerain1, B. Given2, T. Schluep2,
M.-F. Yuen3, H.L.-Y. Chan4, C.-L. Lai3, J. Hamilton2, J.Y. Lau5, C. Ferrari6,
R.G. Gish7, S.A. Locarnini1. 1Victorian Infectious Diseases Reference
Laboratory, Melbourne, Australia; 2Arrowhead Research Corporation,
Pasadena, California, United States; 3The University of Hong Kong; 4The
Chinese University of Hong Kong; 5Hong Kong Polytechnic University,
Hong Kong SAR, China; 6University of Parma, Parma, Italy; 7Hepatitis B
Foundation, Doylestown, United States
E-mail: tania.***@****
Background and Aims: Functional cure in chronic hepatitis B
requires HBV DNA negativity, HBsAg loss and anti-HBs
seroconversion. ARC-520 RNAi drug therapy targets cccDNA derived
mRNA, including the full-length HBsAg transcript. Using a 19plex
anti-HBs panel to map HBsAg epitopes, we have developed a
predictive algorithm of an HBsAg clearance profile in patients
undergoing HBsAg loss during tenofovir therapy, defined as
reduced recognition at loop 1 and loop 2 HBsAg “a” determinant
epitopes. Complimentary to this, we have developed assays to detect
co-existing complexed anti-HBs (with HBsAg), and analysed the ARC-
520 cohorts with the aim of evaluating the impact of RNAi therapy on
HBsAg loss, the identification of an HBsAg clearance profile and the
development of co-existing anti-HBs.
Methods: Analysis of HBsAg clearance profiles and concomitant anti-
HBs was performed for 40 ARC-520 study HBeAg-negative (n = 32)
and HBeAg-positive (n = 8) patients (under code: 30 ARC-520; 10
placebo), from pre-treatment to day 85, and then compared to the
quantitative HBsAg responses. All were entecavir suppressed prior to
(mean 5 years) and during ARC-520 therapy.
Results: ARC-520 therapy resulted in a dose response maximum
decline in HBsAg of 0.3 log IU/mL observed at 1 mg/kg vs 0.5 log at
4 mg/kg in the HBeAg-negative patients (n = 24), and 0.7 log at 4 mg/
kg in HBeAg-positive (n = 6) patients. Analysis of the treated group
identified that an HBsAg clearance profile preceded and/or coincided
with HBsAg decline. A significant association between HBsAg
clearance profile development and ARC-520 treatment emerged at
week1 (11/30, p = 0.038), and strengthened at week2 (12/30, p-value
0.019) and week3 (16/30, p = 0.003). A late HBsAg response at week6
was associated with development of an HBsAg clearance profile (14/
30, p = 0.007). Clearance profiles were not observed in the placebo
group. Complexed anti-HBs development coincided with HBsAg
decline and HBsAg clearance profile detection.
Conclusions: Development of the HBsAg clearance profile was
predictive of HBsAg decline due to ARC-520 therapy, with an
increasing significant association from week1-3 coinciding with or
preceding the HBsAg decline, and the detection of complexed anti-HBs,
reflective of recovery of the anti-HBs response. Further longitudinal and
multiple dose studies will assess the magnitude and persistence of
HBsAg loss on ARC-520 therapy, in the context of the predictive
potential of HBsAg clearance profile and anti-HBs response.
http://ilc-congress.eu/ilc-2016-ebooks/
The following is an abstract on ARC520. Unfortunately it makes no sense to me, what is a HbsAg clearance profile? Where do the HBsAg/HBsAb complexes come from during ARC520 treatment? Hopefully Studyforhope can help out here.
N.B. The abstract is pretty high-powered with Locarnini, Ferrari, and Gish.
FRI-144
PREDICTING HBSAG CLEARANCE RESPONSES DURING ARC-520
RNA INTERFERENCE (RNAI) THERAPY BASED ON HBSAG EPITOPE
PROFILE ANALYSIS
R. Walsh1, R. Hammond1, L. Yuen1, J. Deerain1, B. Given2, T. Schluep2,
M.-F. Yuen3, H.L.-Y. Chan4, C.-L. Lai3, J. Hamilton2, J.Y. Lau5, C. Ferrari6,
R.G. Gish7, S.A. Locarnini1. 1Victorian Infectious Diseases Reference
Laboratory, Melbourne, Australia; 2Arrowhead Research Corporation,
Pasadena, California, United States; 3The University of Hong Kong; 4The
Chinese University of Hong Kong; 5Hong Kong Polytechnic University,
Hong Kong SAR, China; 6University of Parma, Parma, Italy; 7Hepatitis B
Foundation, Doylestown, United States
E-mail: tania.***@****
Background and Aims: Functional cure in chronic hepatitis B
requires HBV DNA negativity, HBsAg loss and anti-HBs
seroconversion. ARC-520 RNAi drug therapy targets cccDNA derived
mRNA, including the full-length HBsAg transcript. Using a 19plex
anti-HBs panel to map HBsAg epitopes, we have developed a
predictive algorithm of an HBsAg clearance profile in patients
undergoing HBsAg loss during tenofovir therapy, defined as
reduced recognition at loop 1 and loop 2 HBsAg “a” determinant
epitopes. Complimentary to this, we have developed assays to detect
co-existing complexed anti-HBs (with HBsAg), and analysed the ARC-
520 cohorts with the aim of evaluating the impact of RNAi therapy on
HBsAg loss, the identification of an HBsAg clearance profile and the
development of co-existing anti-HBs.
Methods: Analysis of HBsAg clearance profiles and concomitant anti-
HBs was performed for 40 ARC-520 study HBeAg-negative (n = 32)
and HBeAg-positive (n = 8) patients (under code: 30 ARC-520; 10
placebo), from pre-treatment to day 85, and then compared to the
quantitative HBsAg responses. All were entecavir suppressed prior to
(mean 5 years) and during ARC-520 therapy.
Results: ARC-520 therapy resulted in a dose response maximum
decline in HBsAg of 0.3 log IU/mL observed at 1 mg/kg vs 0.5 log at
4 mg/kg in the HBeAg-negative patients (n = 24), and 0.7 log at 4 mg/
kg in HBeAg-positive (n = 6) patients. Analysis of the treated group
identified that an HBsAg clearance profile preceded and/or coincided
with HBsAg decline. A significant association between HBsAg
clearance profile development and ARC-520 treatment emerged at
week1 (11/30, p = 0.038), and strengthened at week2 (12/30, p-value
0.019) and week3 (16/30, p = 0.003). A late HBsAg response at week6
was associated with development of an HBsAg clearance profile (14/
30, p = 0.007). Clearance profiles were not observed in the placebo
group. Complexed anti-HBs development coincided with HBsAg
decline and HBsAg clearance profile detection.
Conclusions: Development of the HBsAg clearance profile was
predictive of HBsAg decline due to ARC-520 therapy, with an
increasing significant association from week1-3 coinciding with or
preceding the HBsAg decline, and the detection of complexed anti-HBs,
reflective of recovery of the anti-HBs response. Further longitudinal and
multiple dose studies will assess the magnitude and persistence of
HBsAg loss on ARC-520 therapy, in the context of the predictive
potential of HBsAg clearance profile and anti-HBs response.
Best Answer
There are several articles lately that seem to confirm that excessive viral antigens, such as HBsAg, promote tolerance. However, it still remains to be determined the depth and length of time required to kick-start the immune system with vaccines, INFN, and whatever. There is no reason why ARC521 should not work.
I don't know the planned time line for the development of arc521.
It is obviously highly interesting to see to what extent the hbsag suppressing power in e antigen neg patient will be boosted by the use of arc521.
It can be expected however that it will achieve at best a 2 log reduction, which will make the resulting hbsag levels for most patients not low enough to go below the magic 1u/ml that replicors study has found to be the threshold for a more permanent effect.
Nevertheless, there is the additional effect of suppressing the other proteins of hbv, which might result in reduced replication and virion output in particular if combined with an antiviral with the additional potential effect to further dry up cccDNA replenisment.
It is obviously highly interesting to see to what extent the hbsag suppressing power in e antigen neg patient will be boosted by the use of arc521.
It can be expected however that it will achieve at best a 2 log reduction, which will make the resulting hbsag levels for most patients not low enough to go below the magic 1u/ml that replicors study has found to be the threshold for a more permanent effect.
Nevertheless, there is the additional effect of suppressing the other proteins of hbv, which might result in reduced replication and virion output in particular if combined with an antiviral with the additional potential effect to further dry up cccDNA replenisment.
Thank you very much for that clear explanation. The abstract makes some sense to me now. It occurs to me that the tools developed by Locarnini and his team at the Victorian Infectious Diseases Reference Laboratory, Melbourne, Australia may be very useful to test the appearance of "invisible" HBsAb.
Thank you, once again.
Thank you, once again.
Stephen...provided currently running ARC-520 + ETV + Pegasys trial turns out not to have major sides, I think we could expect ARC-521 to be clinically tried in Australia...as Arrowhead seems to be pushing strong with clinical trials in OZ....
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The protruding loops of the hbsag outside of the surface antigen particle membrane contain apprantly several different bcell epitopes . The monoclonals are specific for these separate epitopes and bind selectively to them.
These binding sites have various strength and dissociation constants. Some bind very forcefully, others rather weak.
When probing a sample of a patient with no hidden hbsag antibody, a certain binding profile to each of the monoclonal will be obtained and can be expressed quantitatively.
Once the natural spontaneous polyclonal antibodies Start developing in a patient, they will tend to complex and remove and block the hbsag epitopes to an increasing extent.
But the binding will lead preferentially to complexing of the strong sticky epitopes since antibody clones develop best against stronger binding epitopes.
Thus the reactivity profile of locarninis monoclonal panel will change, since the best binders are reduced first, showing diminished reactivity.
Quantification of this phenomenon will lead to an "altered hbsag profile", and indicate the formation of endogenous antibody even in the absence of measurable surface antibody.
Simultaneously you expect the appearance of hbsag specific immuncomplexes, which they seem to have a method for measuring.
One reason that the antibodies, even the invisible ones, seem to appear only after lowering of the hbsag level is likely that the critical cd4 tcell helper response to drive bcell development can only start below that level. Above that level the massive amount of antigen leads to tcell tolerance also on the cd4 level, abrogating bcell stimulation and antibody development. That's probably what Carlo ferrari was contributing in this context.
For arrowhead this study is meant to encourage the view that something in the direction of antibody development is starting under IRNA treatment, proven both by suspect monoclonal profile change as well as by the appearance of specific immune complexes. This is good for the stock. ..a step in the right direction, so to speak, with the hope of further intensification after multiple rounds. ..
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