Hep B Blog

Tag Archives: RNAi

Alnylam Discloses HBV Program, Shows 2 Log HBSAG Knockdown with Research-Grade SNALP Tech


Harnessing the Power of RNAi Gene Silencing in Quest of a Cure for Chronic Hepatitis B, and the HBV KnockDown blog written by Dirk Haussecker, who believes it’s about time everyone got serious about a functional cure for hepatitis B. 

Following cryptic remarks during a conference call earlier this year, Alnylam today officially announced its entry into the cure-HBV race.  In impressive data presented at the ongoing TIDES meeting, the company showed that up to 0.5mg/kg SNALP-siRNA was able to knock down HBsAg by ~2 log (99% knockdown) in infected chimpanzees.  The data had been generated by Merck from which Alnylam acquired the RNAi assets in January.  The goal is now to apply some of the learnings generated with Merck’s research-grade SNALP LNP technology and come up with a new candidate based on Alnylam’s GalNAc delivery platform (IND to be filed end of 2015).
In addition to the impressive HBsAg knockdowns, 3-4log knockdowns of viral DNA in serum were seen in the 4 chimpanzees.  In the most viremic chimp, the 4log lowering of viral load was able to normalize liver enzyme (ALT) levels that had been elevated by ~5x ULN.  Intriguingly, in 2 chimps with normal ALTs at the time of treatment, liver enzymes started to increase after dosing had finished (ruling out SNALP LNP as the culprit) and in 1 case also well after viral DNA had started to recover following cessation of RNAi dosing.
Intriguingly, while viral DNA recovered in this short study involving the administration of 3 doses (for every chimp 0.125mg/kg, then 0.25mg/kg, then 0.5mg/kg) over a span of 40 days, there were indications of a desired immunological response similar to that seen withARC520 in the chimp study, most notably an elevation of interferon gamma accompanied by ~2x increases in ALT in 2 of the chimps.
The competition
With Tekmira, ISIS/GSK and now Alnylam (and possibly more to come) following on the heels of Arrowhead Research and ARC520, the competitive landscape is starting to look quite complex.  How it will play out will likely depend on the degree of HBsAg knockdown required (in relative and absolute terms) and who will run the right combination studies with other HBV agents, especially immune boosters such as interferon and possibly RT inhibitors (note: Alnylam speculates that RT inhibitor co-treatment will be beneficial and thereby justified its use of a single RNAi trigger).
If a deep multi-log HBsAg knockdown were required, it would favor Tekmira’s candidate which will be based on a 3rd gen SNALP LNP which can be considered superior to what came out of Merck’s copy-cat efforts subject of today’s presentation.  If lesser knockdowns were able to achieve comparable cure rates, then the power would shift to the subcutaneous versions by Alnylam and ISIS/GSK (esp. the likely GalNAc-based follow-up version).
For ARC520, especially at 2mg/kg and Tekmira probably just 6 months behind, the competition may prove too much, not least because in the 2-dose study in the chimpanzee, the HBsAg knockdown was less than a log (80%).  Granted it was an extremely viremic chimp and one of the RNAi triggers was a mismatch, but still.  If Arrowhead and/or Tekmira demonstrate increased cure rates in 2015, Arrowhead should waste no time and push a single-molecule DPC into development to potentially once again take the lead.
The big question is how far along the way to clinical translation is single-molecule DPC?  Tomorrow may provide an answer.

ISIS/GSK and Tekmira Come Out with HBV Knockdown Plans

Harnessing the Power of RNAi Gene Silencing in Quest of a Cure for Chronic Hepatitis B, and the HBV KnockDown blog written by Dirk Haussecker, who believes it’s about time everyone got serious about a functional cure for hepatitis B. 

If you did not appreciate the value the pharmaceutical industry has come to place on the HBsAg knockdown concept for achieving a functional cure for chronic Hepatitis B (HBV) infection, the last two days will have woken you up.

Yesterday, ISIS Pharmaceuticals reported that it had received a $7M milestone payment related to the development of an antiviral RNaseH development candidate (ISIS-GSK3Rx, aka ISIS-HBVRx) which, although undisclosed for competitive reasons, has got to be for HBV.  And today, Tekmira publicly announced that they will file an IND for an HBV-RNAi candidate in 2014 while hinting at the partnering potential of such a treatment candidate.

Arrowhead Research is thus not alone in their efforts any more.  Coincidentally, Arrowhead reported today the completion of their enrollment of the phase I single-dose, healthy volunteer study with ARC520, their DPC-delivered candidate for chronic HBV.  Accordingly, the dose escalation was able to run through all the pre-planned 6 dose cohorts up to the top dose of 2.0mg/kg.

Apparently, there were no signs of significant dose-related toxicities.  The only finding of concern among the 36 volunteers, 24 of which received drug, was 2 cases of lightheadedness of uncertain clinical relevance.  As these occurred at the highest dose, it seems that the company suspects that it could have been drug-related although the study remains blinded for follow-up.

A dose of 2mg/kg without any serious adverse events or dose-limiting toxicities is a great start for DPC delivery technology.  This is especially the case when one considers that the single-molecule subQ version of DPC that I hope will form the basis for the upcoming pipeline candidates, except for the next one perhaps, will be much more potent than the two-molecule version of intravenously delivered ARC520 based on the non-human primate data presented at last year’s OTS meeting.

With 2mg/kg of ARC520, I further believe that HBsAg knockdowns of over 90% are likely.  The biggest challenge going forward with this program will be setting a knockdown goal and getting the dose and dose frequency right.