Tuesday, November 21, 2017

RNAi Therapeutics Stocks (Part 1)

According to the RNAi calendar, a calendar characterized by 3-year sentiment cycles, we are coming to the end of the first third of another RNAi Therapeutics stock bull market. 

The current cycle follows one (2014-7) that I had referred to as The Wait when the stock market had priced in the ability of RNAi to knock down genes in humans, yet still needed confirmation that this would translate into overall therapeutically beneficial drugs to justify a further increase in the valuation of RNAi companies.  As you know, the phase III APOLLO study of Patisiran in hATTR amyloidosis has provided us with just that.  Expectedly, this has not only lifted the stock price of Alnylam (+70% since results 1 ½ months ago), but positive sentiment has trickled down to 2nd tier companies like Arrowhead Research and Dicerna vying to be the next Alnylam.
The following blog entries will give you a quick run-down on my thoughts about the most bona fide, publicly-listed RNAi companies and stocks as well as the most interesting plays in the oligonucleotide therapeutics arena at large.

 
Alnylam (ALNY)

Love them or hate them, this company and management has stuck to their belief that RNAi is a major drug development platform to support the development of major biotech companies.  Such belief is shown by the fact that Alnylam has long chosen to retain main commercialization rights to their drug candidates while building 100 million $ manufacturing and sales operations around that.  Talk about planning for success!
While this company has recently received most recognition for the outstanding APOLLO data, it has another three (!) drug candidates (Fitusiran for hemophilia, Givosiran for Acute Hepatic Porphyria, and MDCO-partnered PCSK9 inhibitor Inclisiran) for which pivotal phase III data will read out over the next 2 years.

Nevertheless, I suspect that their share price will be largely driven by the launch of Patisiran in 2018. While the base case of ~10k patients on drug seems to be baked into its $13B market cap, there is an upside from the identification of more TTR amyloidosis patients which I feel is quite likely.  And if the amyloidosis, largely heart disease, from wild-type TTR becomes more widely recognized as a significant disease in the elderly along with diseases like Alzheimer’s, TTR amyloidosis alone should be able to support the $30-40B market caps enjoyed by similar niche players like Alexion (àsevere complement-related diseases) and Vertex Pharmaceuticals (àcystic fibrosis).
The main risk is that the competitor TTR drug Inotersen by Ionis will gain a larger market share than is currently widely anticipated, partly because patients prefer the convenience of a simple at-home injection to a day spent in an infusion center every 3 weeks.

I currently view ALNY as the RNAi stock in most need of a breather and am playing the stock from the short side as a hedge for temporary dips in the oligonucleotide and wider biotech stock market.

Dicerna (DRNA)
Long a neglected laggard in RNAi stocks, DRNA has been catching up with the competition with a solid ~200% increase over the last 3 months.

The bullish view of why you might want to ride up the stock further (note: unlike you constantly luck out on binary events, riding a stock up in bull markets is your best bet to make outsized stock market returns) is that DRNA sits now where Alnylam was in 2011/12 when it first demonstrated solid gene knockdown in humans.  It’s been a ~20x return since then. 
Actually, Dicerna’s technology is more advanced than Alnylam’s was back then.  On the other hand, there is now more competition for knocking down genes in the liver which is where Dicerna is focused on almost exclusively.  Still, I love Dicerna as they have a chance to bring two distinct, impactful drugs for severe orphan diseases towards marketing application by 2022 (for primary hyperoxaluria and an undisclosed one).  

A currently diluted market cap of slightly more than $300M is attractive given this realistic opportunity, and in hindsight their widely poo-poo’d March 2017 convertible stock offering now looks like genius as they keep hitting on all the milestones for lowering the inherent cost of the convertible. 
Some of the main 2018 potential catalysts will be (1) the conclusion of the litigation with Alnylam, (2) the disclosure of the second orphan drug candidate and subsequent IND/CTA filing, and (3) positive clinical biomarker data from the hyperoxaluria program.

DRNA is my second largest position along with IONS. 

Arrowhead Pharmaceuticals (ARWR)
While the discontinuation of their DPC-based pipeline was certainly a setback, for the long-term development of the company it wasn’t nearly as dramatic as its once ardent supporters, now harshest critics make it out to be. 
DPC, as illustrated by the cardiovascular deal with Amgen preceding the DPC fiasco, was on its way out and simpler conjugates on their way in as enhanced RNAi trigger stabilization chemistry has been able to close the potency gap with DPC and is now able to provide more sustained gene knockdown.
To play in that area, Arrowhead has been assembling an able, integrated drug development team with a proven track record of quickly advancing drug candidates towards the clinic using best RNAi practices.  Pair that with one, if not the industry’s most commanding IP estates and a proven ability to deal with Big Pharma (à partnering opportunities), I consider Arrowhead as the most likely ‘2nd tier’ company to achieve or even exceed Alnylam greatness.
Look for continued progress of them getting back into the clinic and advances of achieving robust gene knockdown outside the liver.
ARWR has been my largest position for the last few months.

To be continued…

Thursday, November 16, 2017

Artificial Intelligence for RNAi Gene Target Discovery Still Early

It’s not every day that you can see a person like chess playing legend Gary Kasparov at a biotech company’s Investors Day.  And if you did, you might wonder whether this was  some kind of stunt.

I was therefore pleasantly surprised to find that Kasparov was indeed a very fitting appearance investor event by Silence Therapeutics this week (for presentation here).  In the 80s, Kasparov apparently gained an edge over the competition by analyzing opponents’ playing habits using ‘big data’ at a time that personal computers were only about to take off.  As a former professional chess player himself, the CEO of Silence (Ali Mortazavi) therefore believes that there similarly must be ways to more efficiently take advantage of the realms of genomic data being generated to gain an edge over the pharmaceutical competition in finding attractive targets and indications for RNAi gene silencing.

Herd mentality

One of the main reasons I used to look down at Big Pharma  with disdain was their herd mentality especially with regard to the targets and indications they are pursuing.  You can bet that if there is general hype around a certain target, or that once a target has been validated for a commercially attractive indication in a clinical proof-of-concept study, almost all Big Pharma companies will be pursuing corresponding programs.
Unfortunately, such herd mentality is not restricted to Big Pharma, but can also be observed in the biotech space (see PD/PD-L1 for cancer etc etc), even in the subsector dearest to my heart: oligonucleotide therapeutics.  Be it TTR, AAT, DMD, or HBV: once there is a compelling therapeutic rationale for pursuing a gene target, multiple companies will be on its case.
It is for this reason, particularly the fear that an Alnylam or Ionis will scorch the earth around these targets, that many companies now delay disclosing the nature of their most promising preclinical programs.  This is remarkable since small biotechs like Dicerna typically rely on disclosure of their of these programs to garner the necessary investor interest.

Target scarcity?
The fact that the lead programs of RNAi therapeutics companies frequently overlap also beckons the question of whether there is a biological scarcity of targets available.  This would be in contrast to Alnylam which have limited themselves to GalNAc-RNAi trigger conjugates for gene knockdown in the liver, claiming- in the flowery languish of its CEO- to be ‘drinking from a firehose of opportunities’ in just the hepatocyte.
To Alnylam’s credit, it has not only duplicated some of the programs initiated by antisense competitor Ionis Pharmaceuticals and that of its smaller RNAi competitors, they have done some of the heavy lifting themselves.  It was e.g. Alnylam that realized the true value of going after transthyretin for TTR amyloidosis and it was Alnylam that selected a target as unorthodox, but promising as antithrombin for the treatment of a protein deficiency: hemophilia (à ALN-AT3/Fitusiran). 
Other companies like Dicerna and Arrowhead Research can also be complimented for unearthing gene target nuggets for orphan indications like primary hyperoxaluria and liver disease due to certain mutations underlying alpha-1-antitrypsin disease.

Mining for targets
I am not concerned about a dearth of suitable targets that could inhibit the continued growth of RNAi Therapeutics.  This is because there are thousands of rare and severe diseases for which there should be straight-forward genetic solutions and because genetic/genomic information continues to explode.  Still, there is certainly tremendous value if you are the first to gain high conviction around a new target and it was the CEO of Silence who bemoaned what seemed to him like an archaic, manual process of sifting through the genetic ideas one by one.

The panel discussion largely cautioned that human curation will remain dominant for the foreseeable future.  I am slightly more optimistic (or pessimistic, depending on your attitude towards AI) and give AI 5 years or so until it will become a more and more compelling means for driving gene target discovery.  This delay relative to areas like the internet is largely explained by the fact that whereas genomic information has exploded, databases that link them to careful, systematic medical phenotyping are still in their infancy. 
In the meantime, some low-hanging fodder for oligonucleotide drug development may come as a by-product of genetically diagnosing rare diseases when often the last hope for getting a grip on a condition is to genome sequence the patient.
There are beneficiaries already from the recognition of the importance of pairing phenotype with genotype databases such as 23andMe which is said to be getting quite a bit interest from pharmaceutical companies and investors. This comes after the pioneer of sifting through genomic/phenomic data for target discovery, deCODE of Iceland, was acquired by Amgen in 2012.  deCODE rose to fame by linking population-wide genetic information to national health-record databases.  I would think that we will see quite a few more similar endeavors linking existing (à nations with a high level of social bureaucracy such as the Nordic countries) or IT-driven newly generated (à Google, wearables) health records to genome and transcriptome databases. 

And as these databases grow and become more intelligent, it will be those that first understand to harness them that will gain a Kasparov-style edge over the competition.  But don’t be afraid: AI should not make human gene target discoverers/evaluators redundant any time soon and their cost relative to the cost of developing drugs is too low.  If anything, they will be needed to make the ultimate decision of whether to pursue a proposed target as each disease is unique and it will take a long time until enough billion-$ clinical experiments will have been run to provide sufficient feedback for the AI to improve.

 Silence Therapeutics: Ready for Take-off
I usually do not attend biotech companies’ Investors Days, but since London is not too far away from home, I took advantage of the proximity to get a feel for how the company has matured. 
Silence Therapeutics has long been a player in the area of RNAi trigger design and IP (see also their claim on Alnylam products), but has struggled to come up with compelling therapeutic programs.  It was as if they never really tried.  This can probably be attributed to them having lacked the personnel with the experience of taking an idea through the clinic and onto the market.
It now seems as if they not only got the technology (à focus on GalNAc-RNAi) to the point of clinical maturity, but also have assembled the management with the skill and will to succeed in developing game-changing RNAi drugs.  First up will be SLN124 targeting TMPRSS6 for iron overload disorders with a projected CTA/IND filing in Q4 2018.

Friday, November 3, 2017

RNAi Drug Trounces Antisense Rival in Paris ATTR Showdown

The audience gasped when Alnylam finally revealed the full dataset from the APOLLO trial in ATTR amyloidosis.  For the first time, patients and docs will have access to a drug that not only delays or just barely halts, but starts to actually reverse disease manifestation in a majority of patients afflicted by this debilitating, multi-systemic disease. 

Efficacy: reversal versus slow progression

A few minutes before the Patisiran RNAi data presentation, Dr. Benson, the lead investigator from the corresponding NEURO-TTR with rival antisense drug Inotersen was not met with nearly as much awe.  Yes, Inotersen did delay disease progression and was quite a bit better than the placebo control.  However, unlike Patisiran (-6 at 18 months), the mean change from baseline in the critical mNIS+7 score was well in positive territory (+5 at 15 months) indicating disease progression.
As such, Inotersen does not appear to be much better than TTR tetramer stabilizer diflusinal (given off-label in the US) which registered a +9.2 score in a trial over 24 months compared to +29.6 in the control.

Patisiran similarly came out ahead in the quality of life (QoL) assessment (improvement versus in this case a halt for Inotersen), although this was not a primary endpoint in the APOLLO trial. 
The NEURO-TTR trial could score some brownie points here as it not only made QoL a co-primary endpoint, it also scored positively in another patient-reported health score, SF-36.  Although investigators seem to prefer ‘hard’ outcomes measures such as the mNIS+7 and biomarkers, regulators and payors seem to prefer QoL endpoints according to comments at the meeting.

That the efficacy was better for Patisiran should probably not have surprised too much given that its knockdown was slightly better (82% mean median in APOLLO) than that of Inotersen (according to Benson: 75-79%, although I am a bit skeptical here as I do not understand what this range means).
As a side note and although everybody likes to see Patisiran versus Inotersen as an either-or issue, if you combined them both, you would easily exceed the 90% amyloid source protein reductions that amyloid researchers believe is necessary to allow tissue clearance exceed fresh amyloid deposition.

Safety: Patisiran once again exceeds, Inotersen disappoints expectations
If you still had difficulty deciding whether to take a drug that likely makes you better or a drug on which you will likely progress, the relative safety profiles should remove any remaining doubt.  Contrary to suggestions by the ‘counter-detailers’ at Ionis, Alnylam could not find any evidence that the steroid treatments to prevent untoward reactions around the time of infusion had any measurable adverse impact on patient health. 

Maybe this should not come as a surprise either given that immune suppression is given only transiently, every 3 weeks.  To make it clear, none of the many cardiologists in the audience voiced any concerns throughout the two days of the conference (where Patisiran was the star) about steroids in patients with cardiac disease manifestations.
If anything, the Patisiran group suffered from less adverse events compared to the placebo group, probably the result of addressing the disease.

The same, namely exceeding expectations, could unfortunately not be said for Inotersen: in addition to the previously disclosed renal and platelet SAEs, there was a 5:0 death imbalance against the drug candidate.  While the drug-related thrombocytopenia case had already been known and the 4 other deaths were attributed to disease progression, one cannot but notice that strangely, when it comes to safety, all the disease-related, random events always end up going against the Ionis drugs. What a coincidence!  And given that Ionis partner GSK had abandoned Inotersen even before the APOLLO trial were announced, I am wondering what other safety findings (in addition to thrombocytopenia, renal AEs, pyrexia, chills, and nausea) will come to light with the FDA briefing documents next year.

Take-home
Alnylam and the RNAi field could not have hoped for better outcomes from the high-profile APOLLO trial.  If anything, the full results presented at this first European combined patient-doc ATTR conference are more impressive than first indicated by the topline data a month ago.

And regarding the competitive profile compared to the antisense rival, it makes me wonder about the magic of feeding into a biological mechanism that has evolved to do just that: gene silencing.
There are still some questions around the label that these data will support.  Importantly, how much credit will be given to the positive cardiac outcomes since these were not the primary focus of the studies?  But since this is a multi-systemic disease and given the totality of the data, a number of doc presenters made it clear that they will be looking hard for polyneuropathy manifestations in ATTR patients to justify (to payors) treating them with the new agents.

Disclosure: I am short ALNY since the stock may be gasping for air up here, at least in the short-term; long IONS since this public humiliation by the fiercest rival may make them realize that in the orphan drug age, commercialization is a must.

Thursday, November 2, 2017

Two Promising RNA Therapeutics to Face Off in Paris ATTR Amyloidosis Meeting

I’m en route a high-speed train to Paris to witness how RNA Therapeutics are starting to revolutionize the care of patients afflicted by ATTR amyloidosis.  Towards that end, the presentations on pivotal trials with Patisiran (APOLLO; RNAi) and Inotersen (NEURO-TTR; ASO) to an audience of key opinion leaders and patients at the inaugural European ATTR meeting will critically inform the adoption of these medicines.

Top-line data for these agents in the polyneuropathy-leaning form of the disease (FAP) have been disclosed previously (here and here).

This will only be the beginning though, with more potent, safe, and better tolerated follow-up RNA Therapeutics being developed and patient identification becoming more sophisticated.  Ultimately, I envision a world where, for the inherited version of the disease, patient identification based on genetics will be possible such that TTR lowering therapies can be initiated before organ damage through TTR deposition occur.

Patisiran seen leading

When Alnylam disclosed a month ago that intravenously infused Patisiran not only halted disease progression as had been reported for Ionis’ subQ Inotersen, but apparently improved symptoms compared to baseline, the stock shot up ~60% while Ionis stock dived ~15%. Furthermore, safety and tolerability looked solid with much less treatment discontinuations (7.4% vs 37.7%) and nominally less deaths observed in the Patisiran treatment arm versus placebo control (4.7% vs 7.8%). By contrast, Inotersen has been living under a safety shadow ever since deaths due to phosphorothioate ASO-dependent thrombocyte lowering wereseen in addition to renal toxicity.

Can Inotersen stage a comeback?

So even before Patisiran data were presented, the Big Pharma partner for Inotersen, GSK, dumped the drug (by not exercising the option).  Obviously, Ionis wants this to be seen as an act of Dumb Pharma throwing away highly valuable drugs under the directive of bean counters and smartly dressed corporate overhaulers (here: GSK leaving orphan drugs).  Nevertheless, it is difficult to believe that GSK gave rights to Inotersen back for free when it saw Inotersen competitive with Patisiran which easily accounts for roughly half of Alnylam’s  $11B market cap.

Still, while to many it is a foregone conclusion that today’s presentations won’t change much in the competitive dynamics between Patisiran and Inotersen, there are a few scenarios which could change it.

Firstly on efficacy, we still have to learn whether the disease improvement over baseline as reported for Patisiran by Alnylam is medically meaningful over the disease halt reported for Inotersen.  As such, it is possible that the (mean and median) mNIS+7 scores were barely negative (i.e. nominal improvement) as the phase II open-label extension trial results with Patisiran would have predicted.  And who knows, mNIS+7 values for Inotersen could actually be nominally negativ!

Somewhat complicating mNIS+7 matters is that the two companies are using slightly different scales, but I don’t expect this to have much impact on the discussion.

In addition to closing the gap on absolute efficacy, Inotersen could emerge as the winner in terms of treatment efficacy versus placebo.  Importantly, the placebo group in the Patisiran study received steroid treatment around the time of infusion since Patisiran treatment entails this to manage potentially dangerous reactions around the time of infusion and subsequent hours.  Although Patisiran clearly outperformed placebo, steroids, albeit given intermittently, should have some impact on perceived disease symptoms and I found it notable that while Inotersen was statistically better than placebo (no drug at all) at an intermediate time-point 9 months, Patisiran wasn’t yet at 8 months.

It’s therefore possible that Inotersen has the delta advantage over Inotersen which, of course, would influence how docs regard the inherent efficacy of Patisiran alone.

Finally, the placebo issue could also negate another apparent advantage of Patisiran over Inotersen: safety and tolerability. Notably, there was a ~40% SAE rate in both the Patisiran and placebo groups which are historically high for TTR amyloidosis clinical trials.  For example, an 18 month trial with TTR tetramer stabilizer Tafamidis had SAEs of less than 10%.  Is it therefore possible that steroid treatment accounts for the high SAE rate and that the overall SAE rate for Inotersen (to be disclosed) is much lower? 

 With the presentations being less than 8 hours away, we shall find out any time now as my train reaches the outskirts of Paris…



Friday, October 20, 2017

RNAi Companies Ought to Look Beyond Their Platform

This week, Alnylam announced in their roundabout way that it has discontinued the development of ALN-HBV for the treatment of chronic HBV infection.  Instead, it has come to an agreement with well-funded start-up Vir Biotechnology to select a new GalNAc-based RNAi compound, ALN-HBV02, which Vir will largely take control over clinical development.  Alnylam meanwhile retains considerable back-end loaded opt-in rights, milestones and royalties.  

As alluded to in a post last week, ALN-HBV seemed always doomed to fail due to target site selection issues. Also, Alnylam’s heart never really was into ALN-HBV with project leader Sepp-Lorenzino functioning as a one-woman show while competitor Arrowhead mobilized considerable internal and external resources.  She’s, of course, left the company not long ago.

We may never find out the real reasons for their decision although Alnylam would like us to believe that it was a specificity issue since ALN-HBV02 will now be ESCplus-based. Please don't fall into that trap.

My expectation is that ALN-GO1 for primary hyperoxaluria (PH) will suffer the same fate as the initial biomarker data from clinical studies have indicated that likely prohibitively high doses would be necessary to achieve robust oxalate lowering (a modest ~2x increase in glycolate biomarker at a single dose of 6mg/kg).

Once again, a much smaller competitor, Dicerna, has been running circles around RNAi juggernaut Alnylam.  Importantly, it has conducted detailed work on the biochemical pathway of oxalate metabolism and closely studied the natural history of the disease.  The reward was the discovery that the lactate dehydrogenase A (LDHA) is in all likelihood a much better target.

In hindsight it is quite clear that both HBV and PH were only chosen by Alnylam to scare investors away from their competition to cement RNAi dominance.  Not only that, it then filed a frivolous lawsuit against Dicerna alleging trade secret violations.

Will RNAi platform companies have to broaden their tech base?

Given the need to immerse oneself into individual diseases, and also as RNAi is about to open the commercialization chapter, frequently developing drugs for entirely new disease categories served by medicines, a new question arises for the industry: do I remain a platform company or do I have to open my technology base to best serve patient communities and shareholders?

While I do like to criticize Alnylam for shamelessly behaving like the industry's big bully, TTR amyloidosis is one of the diseases they deeply care about.  With 10-20k TTR amyloidosis patients in developed markets, a number that should grow due to increased disease awareness, better diagnosis tools and access, and hopefully prolonged lives, this could well develop into a $5B+ annual market over the next decade.

As the company behind what promises to be the first dominant drug for this disease and a next generation product candidate (ALN-TTRsc02) that should remove any doubt who owns TTR gene knockdown following on its heels, Alnylam would be irresponsible not to try and control the whole patient experience, including complementary non-RNAi treatment options.  In other words, Alnylam would cease to be a pure-play RNAi Therapeutics company while continuing to rely on RNAi for conquering new markets.

This evolution of corporate strategy, of course, is not new to biotechnology and has played out at companies like Vertex Pharmaceuticals (small molecules à cystic fibrosis focus), Biogen (recombinant proteins à multiple sclerosis/CNS focus), and indeed in the Oligonucleotide Therapeutics space before.

Sarepta, once singularly based on morpholino antisense technology, for example has been on a Duchenne muscular dystrophy (DMD) business development spree as their first antisense drug (EXONDYS51) was getting approved.  Sarepta sports a solid >$3B market capitalization illustrating that the financial markets reward such commitment to commercialization and category dominance.

On the other end of the spectrum is Ionis Pharmaceuticals.  

This company is happy to cease control over its groundbreaking compounds and disease insight quite early in their drugs' development paths. Consequently, it finds itself in situations where it either only gets a pittance from breathtaking medical and commercial successes such as SPINRAZA (for spinal muscular atrophy) or it gets caught with their pants down when a partner returns a compound late in the game as has just happened with IONS-TTR/Inotersen and GSK.

The market cap of Ionis, a company that shames $100B+ Big Pharma in terms of its pipeline and which will have close to a dozen compounds on the market and/or in pivotal clinical trials in a year or two, is comparatively paltry: $8B.

And the reason for this?  They are considering themselves a scientific company with a mindset of ‘we are better than organizations with corrupt sales departments’ that is difficult to find even in academia nowadays.  OK, management keeps drawing nice salaries and humongous stock/options rewards, so its really only shareholders that suffer.  

So as much as it hurts me as an RNAi scientists, when it comes to maximizing shareholder returns, the platform serves the purpose of capturing dominant footholds in new disease categories of high unmet needs, but this position has to be fortified by deep relationships with the patient community and an equally deep understanding of disease pathology.  And if necessary, develop and/or license complementary non-RNAi compounds.  

A word on the Arcturus-Janssen HBV deal

In addition to the Alnylam-Vir deal, another HBV RNAi-related deal was announced this week, namely between newly public Arcturus and Big Pharma player Janssen, a unit of Johnson & Johnson.

According to the agreement, Arcturus will work together with Janssen to develop an RNAi drug for HBV utilizing Arcturus’ intravenously administered RNAi triggers formulated in LNPs.   Arcturus uses fancy names for these components, but this is what's behind 'LUNAR' and 'UNA Oligomer Chemistry'. 

Given the availability of potent, but subcutaneous GalNAc-conjugation options in the industry, this interest by Janssen may come as a surprise to some and will serve Arbutus bulls as ammunition in claiming that Arbutus’ HBV RNAi LNP formulation has a future.  A Big Pharma deal after all is a knighthood in the industry.  

Still, I highly doubt it.


It is more likely that similar to Merck which had used LNPs internally as a disease interrogation and target validation tool, but not for commercial development before- even before GalNAc had come to prominence- J&J may view LUNAR-RNAi as a relatively speedy, but inexpensive way to test RNAi for its potential as a backbone therapy in HBV.  If it likes what it sees, watch out for the real deal with Dicerna or Arrowhead.  

Wednesday, October 18, 2017

Can Transient RNAi Augment Cell Therapy-based Immune Oncology?

Unlike all the major RNAi pure plays (Alnylam, Arrowhead, Dicerna, and Silence Therapeutics), RXi Pharmaceuticals is not pursuing GalNAc-based gene knockdown in the liver.  Instead, it applies its self-delivering RNAi (sdRNAi) triggers to local and, more recently, ex vivo gene suppression.

Its ex vivo efforts involve the addition of the silencing triggers to immune cells in the absence of extraneous transfection reagents with the goal of enhancing the performance of cell therapy-based immune oncology.  Immune oncology, of course, is a hot area in drug development.  Notable clinical successes mechanistically aim at immunologically unmasking tumor cells (à checkpoint inhibitors) or sending T-cell killers after them (à CAR-T).

Transient RNAi non-obvious application to cell therapy

When sdRNAi licensee MirImmune, now part of RXi came forward with the idea of applying transient RNAi strategies to cell therapy, I was very skeptical.  Cell therapies after all suggest that long-lived pharmacodynamics are desired, whereas RNAi gene silencing in dividing cells is known to be limited in duration, maybe a week or so.  Wouldn’t therefore gene therapy and in particular genome editing for gene ablation be much more useful?  Or what about that half-forgotten DNA-directed RNAi?  

Certainly, for gene silencing effects that ideally should last throughout the active life of the adopted cells in the patient, transient RNAi is not attractive given all the alternative technologies out there such as genome editing and of monoclonal antibodies.

On closer inspection, however, transient RNAi may be able to uniquely achieve a number of goals that could uniquely enhance adoptive cell therapy for cancer and potentially other applications, too.  One of them is to simply increase the number of cells with the desired phenotype.  After all, the patient-derived cells used for adoptive cell transfer are a precious resource and manufacturing issues could result in cell numbers too low to be useful.  Accordingly, self-delivering RNAi triggers may increase the number of useful cells either by expanding them, e.g. by targeting cell cycle-related genes, or by more effectively directing them to the desired phenotype (e.g. tumor-attacking vs protecting/tolerogenic cells).   

Importantly, as sdRNAi does not require electroporation or transfection reagents, there is less risk that the procedure itself reduces cell numbers or has undesirable effects on the cell phenotype. 

Out of the test tube and into patients, transient RNAi could also be useful in helping in the early tasks of the adopted cells.  One such early step is infiltrating the tumor which is thought to have a major impact on immune oncology treatment success.  While tumor infiltration can be expected to be largely guided by proteins interacting on the cell surface and would seem a suitable application of monoclonal antibodies, monoclonal antibodies often have difficulties getting into tumors.  

It is also conceivable that an early performance provided by transient RNAi may have a lasting effect on eventual therapeutic outcome, e.g. by hitting the cancer hard initially so that the risk of immunologic escape by mutation is minimized.  This is similar to how early reductions in pathogens predict the treatment success of most infectious diseases such as HCV.

Finally, RNAi may be applied to multiple genes at once.  This is more difficult to do with systemically administered monoclonal antibodies, and unlike monoclonal antibodies, RNAi can also inhibit proteins not accessible to monoclonal antibodies; multi-targeting is also less effective with genome editing.

Looking ahead

Transient RNAi for adoptive (immune) cell therapy is in its early stages.  Given some of its unique characteristics, it could be a useful addition to the gene toolbox next to genome editing, DNA-directed RNAi, or simple gene addition.  While RXi is planning to plod along with preclinical proof-of-concept studies, as a non-immune oncology person and given the poor capitalization of the company, I particularly look towards clinical collaborations and corporate partnerships to judge just how compelling a tool transient RNAi really is here.


RXi as an investment or trade

RXi Pharmaceuticals is a small biotech company with a tiny market cap of ~$13M and I would be remiss not to mention that I currently own somewhat more than 2% of the outstanding shares (ticker: RXII).  This is a relatively small gamble on my part, but certainly enough to keep me interested and engaged. 

Right now, it is probably not much more than a gamble given that RXi’s management has displayed an extraordinary degree of naivete about the capital markets.  Accordingly, their continued operations currently largely rely on an ATM-type arrangement with Lincoln Park Capital Fund which appears to only have accelerated putting down the stock, and possibly eventually the company down a death spiral. 


Near-term, RXII is therefore a bet that management will finally stop this nonsense and instead rely on the upcoming multiple (!) clinical trial outcomes catalysts by year-end from at least 3 (dermal scarring, cutaneous warts, consumer skin products) of its non-immune oncology portfolio to create some excitement about the stock.  Results from a retinal scarring trial are expected in early 2018.  Considering the tiny market cap of ~$13M, the sheer number of upcoming data read-outs alone could result in mouth-watering stock returns if the stock gets discovered.  Such a run-up would of course also provide financing opportunities to feed its immune oncology ambitions, so please management: don't put a lid on it by activating the ATM.

Monday, October 9, 2017

HBV RNAi 2.0


Gene knockdown, in particular RNAi and RNaseH antisense, holds great promise in the treatment of hepatitis B viral infection.  It is currently the only practical means to potently inhibit all viral gene products*.  It therefore is poised to become a cornerstone of future treatment regimens aiming at functionally curing HBV, an infection predisposing more than 200 million patients worldwide currently to liver failure and cancer.

Arrowhead- lessons learned

Unfortunately, the field took a big hit last year when HBV RNAi trailblazer Arrowhead Pharmaceuticals had to abandon its efforts due to preclinical toxicity resulting from its particular approach to releasing the RNAi triggers into the target cell cytoplasm (monkey deaths due to the DPC).
Nonetheless, after more than a dozen trials in WoMan, the company had learned a great deal about HBV and how to best tackle it by RNAi.  Chief among those lessons were the observations that RNAi can suppress viral genes, most notably the surface antigens HBsAg by sometimes more than 2-3 logs.  Moreover, in HBe-antigen negative and those HBe-antigen positive patients previously exposed to polymerase inhibitors (‘nukes’), Arrowhead painfully found that most HBsAg is derived from host genomically integrated HBV.  Consequently, RNAi trigger target sites placed downstream of the HBsAg ORF may be lost and RNAi rendered futile (ARC520àARC521 transition). 
Finally, consistent with the experience with nukes and interferons, it appears that RNAi treatment success (functional cure) should follow complex viral and host immune dynamics and while intriguing changes were observed in the clinic with ARC520/1 (e.g. new lower baselines following treatment cessation), it remains unclear how long an RNAi agent would have to be given.  This has implications for whether intravenous routes of administrations are practical or not.

The competition
Arrowhead Pharmaceuticals, however, has not been the only RNAi game in town developing HBV therapeutics.  Its main competitor in terms of scientific prowess has been Arbutus Biopharma (renamed from Tekmira after biotech wonder boy Vivek Ramaswamy of Axovant fame spectacularly raided the company in 2015).  Its lead RNAi candidate ARB-1467 comprises of 3 RNAi triggers which are formulated in lipids (LNP) and is given intravenously alongside steroids.

While I like the 3-trigger strategy for pangenotypic coverage and for minimizing the risk of the virus developing drug resistance (including by genomic integration), the more cumbersome intravenous route of administration- now reduced to short 2-week intervals in an effort to increase potency- and the steroids makes ARB-1467 uncompetitive in a world of more potent and less frequent simple subcutaneous competition.  The use of immune suppressive steroids, of course, in HBV patients is a dicey proposition and would also seem to run counter to the ultimate aim of achieving immune control of the virus.
Unless it turns out to promote a functional cure along with other agents in short order, say less than 6-12 months, ARB-1467 will likely end up as a science project without much clinical impact.

RNAi powerhouse Alnylam Pharmaceuticals meanwhile is the third RNAi company that has begun clinical development of an HBV RNAi agent.  Importantly, it has been the first company using a simple subcutaneous GalNAc-conjugate format, therefore positioning it to be useful even when more prolonged treatment will turn out to be necessary.
After review of the program, however, it appears that the company prematurely rushed the single trigger ALN-HBV into the clinic without thinking too much about resistance issues.  To start with, ~2% of tested HBV genotypes have mismatches with the trigger that mitigate targeting efficiency.  As a single trigger candidate, ALN-HBV will also have to be given alongside highly potent replication inhibitors (nukes) as one can easily see how ALN-HBV resistant genotypes would otherwise eventually take over.

ALN-HBV moreover targets a site downstream of the HBsAg ORF, around the DR2 repeat element with marks the integration hotspot that has bedeviled ARC-520 before.  While Alnylam has been going around claiming ALN-HBV doesn’t suffer from ARC-520-type issues, I would challenge them with two points:

1)     under selection pressure by ALN-HBV to maintain HBsAg expression and thus evade host immune detection, the virus may ‘choose’ to break up upstream the ALN-HBV target site without affecting the HBsAg ORF; 

2)      more troublesome, closer inspection of the very paper Alnylam points to for making its claim (Jiang et al. Genome Research 22: 593) and which analyzes HBV integration hotspots, shows that ~40% of DNA break points appear to be upstream of the ALN-HBV target site (compare ‘position 1600’ below).      


One can therefore easily see why the project leader behind ALN-HBV, Laura Sepp-Lorenzino, has recently left the company to join Vertex Pharmaceuticals.  One has to get the impression that ALN-HBV, just like ALN-GO1 have only been rushed to the fore as a front in order to keep a lid on their competition by creating doubt about the ability of Arrowhead Pharmaceuticals and Dicerna, respectively, to compete with juggernaut Alnylam. 





 
It is yet another lesson that in drug development, a detailed understanding of the disease is as important as the technology used to tackle it.  Half-hearted side projects typically lead nowhere.

Lastly, I would be remiss if I did not mention the RNaseH antisense efforts by Ionis along with partner GSK, and those of Roche.  Ionis/GSK are not only developing an unconjugated fully phosphorothioated antisense molecule, which I believe has little chance of competing in the market due to predictable safety and potency issues, but also a more interesting GalNAc-conjugate version (IONIS-HBV-LRx).  Although I currently see RNAi ahead of antisense in gene knockdown in hepatocytes (potency, frequency of administration, and safety), the GalNAc-conjugate version potentially has the advantage of also being able to access the pregenomic RNA directly, while direct pgRNA cleavage by RNAi of this non-mRNA remains to be shown.  My prediction is that  while RNAi can to some degree access pgRNA, this is not as effective compared to its cleaving mRNA.  What all of this means biologically remains to be seen.

Arrowhead HBV RNAi 2.0

Therefore, after all the drama and competitive noise, Arrowhead is poised to recapture the HBV RNAi lead with its new GalNAc-based candidate.  ARO-HBV is poised to enter the clinic in the first half of 2018.   It is subcutaneously administered and involves 2 RNAi triggers that are claimed to cover the viral resistance bases, including HBsAg derived from genomically integrated HBV.
The company expects the agent to be used once a month or less frequently, an attribute valuable should functional cures take longer to emerge.

Given knowledge leadership in HBV gene knockdown and prior practical experience, Arrowhead should also be able to navigate through the HBV clinical development maze faster than its competition.  As can be seen from its resurging stock price, this view is also shared by an increasing number of investors. 
Arrowhead has paid for taking some short-cuts when it was compelled to push ARC-520 into the clinic to give it a shot of becoming a serious player in RNAi before it ran out of capital.  It took some risks and failed, but that failure could well be the soil from which future success will emerge. 

Disclosure: long Arrowhead Pharmaceuticals

 

 

 

 

 

 

* it is unclear whether RNAi can directly cleave pregenomic RNA, whereas RNaseH antisense should be able to do that.
By Dirk Haussecker. All rights reserved.

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