Discrepancy in Claimed Injection Site Reaction Frequency with ISIS-ApoCIII

My fundamental believe as to why RNAi is fundamentally preferable over phosphorothioate (PS) antisense for therapeutic gene knockdown, is that PS antisense involves the saturation of various tissues in the body with a sticky chemistry that is associated with inflammation.  By contrast, with RNAi Therapeutics, you only need to transiently achieve relatively high tissue levels so that enough of the RNAi silencing machinery can be fed with the RNAi triggers.  Unincorporated oligonucleotides can, and usually are, then washed out without much or any loss of efficacy.

Especially in chronic settings and systemic administration, this persistent inflammatory herd raises the specter of multi-organ fibroses and other adverse immune effects, including vasculitis.  The mipomersen briefing docs showed that such concern is warranted, especially with the findings of vasculitis in non-human primates and frequent injection site reactions which, in contrast to ISIS management which routinely characterizes them as ‘cosmetic’ and ‘nuisance’ side effects, should be interpreted as indicators of what might be happening more systemically.

As you also know, I am equally wary of the reliability of ISIS’ forward and backward looking statements.

Obviously, when ISIS reported phase II data from theISIS-ApoCIII study showing a deep 88% knockdown of the target gene and impressive >70% reductions in serum triglycerides, the question of whether this is a real drug or another KYNAMRO/mipo-like dud hinges on its safety profile.  Unfortunately, no hard numbers were provided on this front in the initial press release.  Instead, there was much beating around the bush characterizing them as being very infrequent and mild in nature. 

However, in the conference call, one analyst apparently wasn’t satisfied with this and asked for a straightforward quantification of the injection site reactions (the following is an adaptation of the telcotranscript on Seeking Alpha):

Jim Birchenough – BMO Capital Markets

Yeah. Hi, guys. Congratulations on the data. A few questions…And then just final [third] question, if you could quantify injection site reaction profile and contrast it with KYNAMRO, I think that would be helpful…

Richard S Geary (ISIS Pharmaceuticals)

Good. This is Richard, and thank you for those questions...The third question, I don’t think I got.

Stanley T Crooke

Reactions compare and contrast to KYNAMRO.

Richard S Geary

So you will remember that in our Phase 1 experience we actually compared directly with three weeks study in normals and we saw almost a 90% reduction in the frequency of ISRs.

Stanley T Crooke

Compared to KYNAMRO.

Richard S Geary

Compared to KYNAMRO, and I would say that looking at these Phase 2 studies, this is being replicated very low frequency and much less severity. These are very mild and it’s almost all erythema that resolves very quickly.

Stanley T Crooke

So we’re seeing much more mild and much less frequent injection site reactions in this study as we saw in earlier work. Is that a fair way to say it, Richard?

Richard S Geary

Yes.

A 5-fold exaggeration of the reduction in injection site reactions

So while ISIS did not add much regarding the frequency of injection site reactions in the phase II study, at least a relative number was provided for ISIS-ApoCIIIRx.  Going back to the phase I trial for which the results were recently published (Graham et al. 2013), the following was said about the frequency of injection site reactions:

‘The most common adverse event was mild injection site reaction, a typical response to subcutaneously administered drugs.52 No subject dosed with placebo complained of injection site reactions, al- though 13 of 25 (52%) subjects dosed with ISIS 304801 experienced at least one. Approximately 1 of 6 injections (median, 17%) led to an injection site reaction, the majority of which resolved within an hour.’

To test the veracity of ISIS’ comments, you would then have to dig up the numbers for mipomersen.  In the FDA briefing docs, the following can be found about the frequency of injection site reactions:

‘ISRs were the most commonly reported AE in the clinical development program. In the pooled Phase 3 trials, 84.3% (220/261) of mipomersen-treated individuals experienced 3,683 ISR events and 33.3% (43/129) of individuals in the placebo group experienced 139 ISR events.’

Assuming for simplicity that the 261 subjects in the phase III studies received 52 injections minus X due to drop outs (note: this fudge factor actually favors ISIS’ numbers as it increases the injection site rate for mipo) we arrive at around 3683 injection site reactions from 10,000 injections, i.e. a rate of around 37%.  If ISIS’ comments on the 90% drop in injection site reaction frequency were then true, the rate for ApoCIII should be 3-4% and not 17% (according to ISIS the mipo injection site reaction rate would have to be 170% for the numbers to match up).  In a 13-week trial, a 17% injection site reaction rate also means that the majority of subjects will experience such reactions, some more often and severe than others.

Of course, I am just a molecular biologist and know little math. I therefore look forward to the ISIS bulls or even the company itself to point out where I went wrong in my calculations.

ApoC III Confirmed as High Potential Gene Knockdown Target

Small molecules, monoclonal antibodies, and fish oils move out!  Combining the power of genetics and therapeutic gene knockdown, ISIS Pharmaceuticals presented last night by far the most profound reduction in serum triglycerides which are thought to be an important risk factor in cardiovascular disease and other less common conditions such as pancreatitis: a 72% reduction of serum triglycerides following an 88% gene knockdown of ApoC III with a bonus 40% elevation of the good HDL cholesterol in a phase II study of ISIS-ApoCIIIRx presented at the Amercian Diabetes Association. This confirms in Man that ApoC III antagonizes the metabolism of triglycerides.

The ApoC III knockdown results were not unexpected.  In the preceding phase I study, 71% and 78% ApoC knockdowns were seen at the 200mg/week and 400mg/week dose levels, respectively.  The enhanced, 88% knockdown seen in this phase II study at the 300mg/week level can be explained by the fact that the study drug in the first study was only given for 4 weeks, at which point the phosphorothioate oligonucleotide may not have reached saturation in the liver, whereas in this study it was given for 13 weeks.  

More surprising was the deep 72% reduction in serum triglycerides.  In the phase I studies, 'merely' 43-44% reductions were observed, although this to my knowledge is still superior to e.g. Amarin’s glorified and controversial fish oil.  It is possible that this result is due to a non-linear relationship between ApoC III and serum triglyceride lowering.

Obviously, questions remain unanswered following this small and still early-stage study.  I was surprised to learn that data were reported for only 11 patients with 200 and 500 mg/dL serum triglycerides and type 2 diabetes (the enrolment criteria) although the clinicaltrials.gov entry indicates that 24 was the originally planned number for the blinded, placebo-controlled study.

Secondly, it will be important to learn about the safety and tolerability profile of ISIS-ApoC IIIRx, also in light of the clinical trial experience with the ApoB-targeting, LDL cholesterol-lowering mipomersen (aka KYNAMRO).  To wit, ‘nuisance’ side effects such as injection site reactions and flu-like symptoms contributed to frequent discontinuations in the trials and likely explain what appears to be a very slow uptake after marketing approval.  Of course, Dr. Stan Crooke, the ever-so optimistic CEO of ISIS Pharmaceuticals is convinced that ISIS-ApoCIIIRx has no such issues due to improved screening  methods.  As a reminder, in the phase I study with ISIS-ApoCIIIRx, one out of six injections were associated with injection site reactions.

Thirdly, the link between ApoC III and cardiovascular risk is still debated.  Moreover, similar to ApoB, ApoCIII is thought to contribute to VLDL efflux and inhibiting it may lead to an elevation of liver triglycerides.  This is particularly problematic given that the target patient population is already at an increased risk of hepatosteatosis.

While phosphorothioate antisense company ISIS Pharmaceuticals clearly has a head-start on ApoC III, given the ability of various RNAi technologies to potently knock down genes in the liver, ApoC III is an attractive target for the RNAi Therapeutics industry.  Such a candidate could either be positioned as a best-in-class alternative (à safety; I particularly like here the prospect of a subQ DPC version) or possibly as part of a multi-targeting cocktail against cardiovascular disease (attractive for SNALPs).  It is also one with an attractive partnering potential for some of the smaller companies in the space (early clinical POC, maybe partnering even before clinical development). 

Silence Therapeutics First to Advance Systemic Cancer RNAi Therapeutics into Phase II

Among the first crop of systemic RNAi Therapeutics for cancer (see also CALAA01 by Arrowhead and ALN-VSP02 by Alnylam), Atu027 has become the first to officially enter phase II clinical development.  Following the completion of a bridging phase Ib study testing the safety of Atu027 in combination with chemotherapeutic gemcitabine for a treatment cycle of 28 days, Silence Therapeutics announced this week that safety and efficacy of the RNAi-chemo combo will now be more rigorously tested in an expanded phase II study for the treatment of pancreatic cancer.

The bridging study became necessary since in the initialphase I study, the safety of Atu027 was assessed in isolation only.   The press release by the company now suggests that the bridging study testing 0.253mg/kg of Atu027 along with 1000mg/m2 gemcitabine was uneventful since no expansion of cohorts was deemed necessary.  Such an expansion would have become necessary if a dose-limiting toxicity had been observed.   Accordingly, the results are in line with the phase I studies where a dose limiting toxicity was only observed at the 0.336mg/kg dose of this AtuRNAi-lipoplex formulation.

Given that Atu027 is not thought to have a strong effect in terms of directly killing cancer cells, but instead is expected to inhibit metastatic spread, the company believes that it will be clinically most useful in combination with an antineoplastic agent such as gemcitabine in pancreatic cancer.  The choice of pancreatic cancer was probably driven by the high unmet medical need in this indication and it is possible that additional combinations will be explored for a range of other cancers.  Such an expansion of the Atu027 franchise will have to be balanced by the advancement of other RNAi Therapeutic candidates with more straightforward mechanisms of actions to put the company on a more balanced financial footing.

* In addition to the systemically delivered Atu027, two other RNAi Therapeutics for cancer have entered phase II development.  These are the implanted RNAi trigger-eluting siG12D LODER from Silenseed, also for pancreatic cancer, and ex vivo ddRNAi-GMCSF gene therapy combo bi-shRNAfurin by Gradalis for a variety of cancers.

Biotech IPOs Show Wall Street Likes New Toys

The biotech sector is white hot these days, and as a result, the IPO window is wide open.  This is illustrated by the fact that preclinical companies like gene therapy outfit Bluebird Bio and Agios Pharmaceuticals have either just slipped through the window or are about to.   This is also illustrated by the fact that Duchenne Muscular Dystrophy (DMD) exon skipping company Prosensa is aiming at a valuation of $400M at its IPO despite the uncertainties around the approvability of its only product candidate that matters (endpoints and safety issues) and for which it has given away much of the financial potential to a Big Pharma (GSK). And the ticker: RNA.

As it relates to gene therapy and RNA Therapeutics companies IPOeing- in addition to Prosensa, small molecule RNA processing modulation Co. PTC Therapeutics and aptamer company Regado- a gap between the valuations of already public companies and those emerging from the obscurity of the private sector is becoming apparent.  Without meaning to talk down on Bluebird Bio or gene therapy, I am scratching my head as to why this early-stage company sports a $150-200M market cap (it priced above its guided range and popped 50% on the open) whereas a much more proven and clinically advanced lentivirus-based gene therapy company, Oxford Biomedica, is not valued at even a quarter of that.  

Given that Oxford Biomedica is developing drugs for medically important indications, especially for those affecting the eye and can be proud of a remarkable preclinical literature record, just as Bluebird Bio can, the difference cannot be product versus platform focus.  Or take for comparison preclinical microRNA Therapeutics company Regulus Therapeutics (2012 IPO) with a market cap of $350M and clinically slightly more advanced Arrowhead Research with a market cap of around $60M (disclosure: I own Arrowhead).   

Instead, I believe it shows the benefit of being able to stay out of the spotlight when valuations are severely depressed as they were in the wake of the housing crisis when research and having a pipeline were actually assumed to be liabilities, not assets.  Companies like Oxford Biomedica and Arrowhead Research may thus be viewed as damaged goods.  Only supposed best-in-class companies in the RNA Therapeutics space with a halo like Alnylam and ISIS Pharmaceuticals were able to decisively spring back from low valuations as sentiments improved.

By contrast, biotech networks such as the one around Third Rock have understood to wrap up biotech companies as exciting new toys for Wall Street to buy.   Orphan drugs anybody?  Of interest, Alnylam’s CEO John Maraganore has had an involvement with both Agios and Bluebird.  I give these individuals full credit for promoting innovation.   By the same token, the depressed valuations of some of the existing innovators are another example of the inefficiency of the public markets.

ALN-TTR02 Phase II Results Preview

Although the phase I results for ALN-TTR01 in late 2011 and ALN-PCS02 in first half of 2012 should have caught the attention of the diligent biotechnology investor, it was the highly potent knockdown (>90%) reported for ALN-TTR02 in July of last year that put the spotlight back on RNAi Therapeutics. The results for the TTR amyloidosis drug candidate not only benefited Alnylam, they were a blessing to the entire field of RNAi Therapeutics allowing it to raise ~$300M over the ensuing 12 months.  It is therefore an understatement that the phase II results for ALN-TTR02 to be disclosed in about two weeks will be closely watched across the industry and investors.

Possibly hoping to relieve some of the tension around the event, Alnylam has long telegraphed what we should expect the results from this open-label study to be: just look at the multi-dose non-human primate data and this is what you will see repeated in humans.  Nevertheless, I doubt that the generalists are buying the argument that non-human primates studies are highly predictive of clinical results, at least in terms of gene knockdown.   Just witness the valuations of other RNAi Therapeutics companies that have reported impressive non-human primate data (one could call that a buying opportunity).

Study primarily designed for safety…

The phase II study for ALN-TTR02 is primarily one of safety for repeat administration of ALN-TTR02.  The initial two-dose study design seems an overly cautious approach given that products enabled by Tekmira’s SNALP delivery technology have already been dosed for several months in patients with cancer.  This could be due to differences in how the different divisions within the FDA view the safety of SNALP and/or RNAi product candidates. 

With regard to hypersensitivity reactions, which are probably the most critical hurdle ALN-TTR02 needs to overcome, multi-dosing should actually the lower the incidence of infusion reactions (desensitization) which were the major safety issue in the phase I single-dose study.  With regard to spleen toxicity, multi-dosing is predicted to increase risk (cumulative).

Overall, given the dose (study geared towards the 0.3mg/kg dose) and history of ALN-TTR02, I am quite optimistic that no nasty surprises will emerge on the safety front.  This would also be consistent with plans by Alnylam to reduce the use of immune suppressants in the extension phase of the study.

…but efficacy could drive volatility

Although we have already been told what the efficacy results should look like and that Alnylam is aiming for an 80% knockdown, I expect analysts to pay close attention to efficacy given that Alnylam is in an arms race with ISIS/GSK.  As a reminder, in the 300mg/week regimen that has been chosen for the ongoing phase II/III study, a ~70% knockdown was reported with the ISIS/GSK antisense compound.  However, while a phosphorothioate antisense compound for liver-targeted gene knockdown given weekly has a sustained knockdown effect over time, there are wider fluctuations between peak and trough knockdowns for a SNALP-delivered RNAi Therapeutics administered only once a month.  In other words, watch the time-course of the knockdown, especially after Alnylam announced that it is considering a once-every-3-weeks regimen for the extension phase of the study.

Wall Street ascribes most of Alnylam’s value to TTR amyloidosis program

The reason, of course, why the TTR amyloidosis data is expected to cause major volatility is because two thirds if not more of Alnylam’s market value is based on a discounted cashflow analysis for ALN-TTR02 and ALN-TTRsc in the polyneuropathy and cardiomyopathy markets, respectively.  It is estimated that with premium orphan pricing (you will be surprised how precisely Alnylam’s pharmacoeconomic models will arrive at a fair price of $300,000 per patient year), peak sales revenues for Alnylam’s TTR products will be somewhere between $1.3-$2.0 billion.

I am optimistic that the TTR product candidates will make it to market and dominate over any phosphorothioate-based antisense competitor.  However, there remain important uncertainties as it relates to pricing and reimbursement, especially in some of the European markets where many of the FAP patients reside.  Furthermore, there is always an element of chance when it comes to avoiding prohibitive toxicities from sequence-specific off-targeting in a chronic treatment setting.

Over time, however, it does look like the rest of Alnylam’s pipeline is finally gathering steam.  With the porphyria and AAT deficiency candidates ALN-AS1 and ALN-AAT, respectively, and the intriguing complement inhibitor program, additional differentiated, high-value orphan opportunities are emerging.  It remains to be seen, however, whether the GalNAc-siRNAs are potent enough to exploit the potential of RNAi Therapeutics for these diseases or whether other delivery technologies enabling deeper knockdowns would have been appropriate.  This concern e.g. applies to the hemophilia program where my feeling is that only deep knockdowns will allow you to see clinically meaningful improvements in clotting times.  Unfortunately, I am still trying to find results from clotting assays (which are standard in the field) and not just the thrombin measurements that Alnylam is providing.

Trading the event

As Alnylam's share price has tripled since last year's announcement of phase I results and given that the two-dose design won't do that much for additional de-risking, I am speculating that only in a very bullish, confident biotech market that seizes on every news opportunity there is much upside from the phase II top-line results.  Because of the nervousness that has been creeping into the markets the last two weeks, I am taking a small bearish position ahead of the event, in a way hedged by much larger long positions in other RNAi Therapeutics companies (Arrowhead Research, Tekmira, RXi Pharmaceuticals) which are more attractively valued on a relative basis and should benefit from renewed RNAi Therapeutics investor interest as a result of the data release.

Last reminder that the GTC RNAi Therapeutics conference will start this week.  Don't forget to mention 'RNABLG13' for 20% discount on registration.

RXi Reports Dose-Related Knockdown Three Months Following Single Injection

RXi Pharmaceuticals today reported top-line results from the first of two phase I studies with RXi-109 in dermal scarring.  Intriguingly, the company claims to observe target gene knockdown three months following a single intradermal injection of their self-deliverable RNAi trigger (p=0.02) in a manner that was apparently dose-related. 

Such a drug-dependent and dose-related knockdown would exceed my expectations from this trial as stated in a recent preview here.  The reason why I merely expected to see a correlation between CTGF levels and phenotypic effect on dermal scarring being reported today is that I did not have high confidence that the tissue residence time of RXI109 would be prolonged enough to observe a bona fide RNAi knockdown. 

To wit, the tissue biopsy on which this data rests was obtained during a tummy tuck three months after the intradermal injection of the RNAi.  To assess whether there was an RNAi knockdown in such a single-dose study, I would have thought that an early time-point such as two weeks after injection would have been more appropriate, also because it is likely that some of the CTGF-producing cells might be proliferating in this setting (RNAi duration inversely correlated to proliferation status).

The notion that a correlation between CTGF levels and wound healing would be observed was based on CTGF reflecting tissue inflammation.  So regardless of whether there was an RNAi effect or not, you might expect to see such a correlation.  It is difficult, however, to explain a drug-dependent and dose-related target gene knockdown with this notion, except for by a rare coincidence.

These results then bode well for the multi-dose phase I studies from which results will be reported in time for the Investor and Analyst Symposium on July 12.  While safety was the primary focus of the first study (no adverse event on the early wound healing process confirmed), the effect of RXi-109 on wound healing will be the focus of the second study.  It should be added though that given the small size of the trials and the patient population which is not predisposed to scarring, spotting the difference will be tough.

Disclosure: long RXII.

Nitto Denko Brings RNAi Therapeutics to Clinic as New Star Rises on RNA(i) Therapeutics Firmament

There is more evidence from the San Diego biotech scene that investment is flocking back to RNAi Therapeutics, from all sorts of sources.  Following successful public offerings by the likes of Arrowhead Research and Alnylam and multi-million dollar VC rounds in two smaller RNAi Therapeutics companies earlier this year, the investment this time is coming from a large diversified company and private investors.

Nitto Denko Tackles Fibrosis

With the initiation of clinical development for an RNAi Therapeutics in fibrosis, not Merck, not Novartis or Takeda, but Japanese materials manufacturer Nitto Denko has become the largest company yet to enter an RNAi Therapeutics into the clinic which originated from internal R&D.  The newest addition to the RNAi Therapeutics pipeline is based on research from Prof. Niitsu’s laboratory at Sapporo Medical University and involves a vitamin A-targeted liposome for gene knockdown of a collagen-specific chaperone (Hsp47) in fibrogenic cells.  Subsequent to the seminal Nature Biotech publication on gene knockdown in hepatic stellate cells for not just the stabilization, but even the reversal of liver fibrosis (Sato et al. 2008), a more recent publication applying the same formulation in pancreatic fibrosis indicates that Nitto Denko is considering ND-L02-s0201 for fibroses beyond the liver.  

Of note, the RNAi trigger design came from Quark Pharmaceuticals (Tuschl workarounds with lots of non-canonical modifications) and Nitto Denko itself has become the world’s largest clinical supplier of oligonucleotides following its 2011 acquisition of Avecia.

Fibrosis is becoming a hot area in Oligonucleotide Therapeutics with a number of companies (RXi Pharmaceuticals, Excaliard/Pfizer, Sirnaomics, BMT etc) chasing fibroses in the skin, eye, liver, and beyond.  As fibrosis is a complication, often the most debilitating consequence of  many diseases involving inflammation (think fatal diseases such as idiopathic pulmonary fibrosis), and little progress has been made in reversing it, the expanded target space available to oligonucleotide therapeutics could bring unique opportunities at changing the way we think about the disease.

RNAi Start-up Arcturus Therapeutics Raises $1.3M in Private Investor Round

Coincidental with the Nitto Denko trial initiation, San Diego-based Arcturus Therapeutics announced that it has raised $1.3M in a private investor round.  Arcturus Therapeutics, curiously founded by former Nitto Denko employees, is said to be developing a liver-targeted RNAi Therapeutics for an unnamed rare/orphan disease indication.  It appears that the value of Arcturus is based on a nanoparticle delivery technology.  Although the nature of the formulation is yet to be disclosed, my impression is that it is a liposomal one given the background of the company founders and the liver indication.

It is very good seeing examples like that where the RNAi Therapeutics appetite is reaching down to the grass-roots levels, unfathomable even just 1 ½ years ago.  While I once worried that the RNAi Therapeutics dry spell (2008-2011) could prove disastrous to innovation in the industry, some seeds were able to survive.  I look forward to following the progress of these technologies and companies as they grow.