RNAi is the Future of Cardiovascular Disease

At least, this is what Big Pharma and Biotech is saying right now following deals between pure-play RNAi companies Arrowhead Pharmaceuticals and Dicerna with Amgen and Eli Lilly, respectively, and the sale of The Medicines Company with its lead PCSK9 RNAi asset really being only a matter of timing.  Besides its new relationship with Eli Lilly announced yesterday, Dicerna has an ongoin CVD-related NASH/NAFLD collaboration with Boehringer-Ingelheim.  In addition, Wave Life Sciences and Akcea, the commercial Ionis spin-out, have been pursuing cardiovascular targets along with Pfizer and Novartis, respectively, using the competitive RNaseH antisense gene knockdown technology.

Drugging the undruggable

Part of the attraction of RNAi for CVD for the pharmaceutical industry is because the targets that come from large genetic studies (e.g. ApoCIII, Apo(a), ANGPTL3) based on chance alone are not readily druggable.  To make matters worse, amorphous lipid macromolecular aggregates are particularly difficult to target with either small molecules or antibodies.

Infrequent dosing

What a difference 10 years can make.  When Protiva (now Arbutus) was one of the first to enter a systemically administered RNAi therapeutic against LDLc-related ApoB into the clinic a decade ago, it often found itself ridiculed for using RNAi in such an indication.  Systemic RNAi back then required relatively frequent (1-3 weeks) intravenous administration which would make it an unlikely modality for widespread diseases that ideally require decade-long preventive treatment strategies.

Fast-forward to the present and now we have subcutaneously delivered RNAi with potential dosing frequencies of up to once-a-year as evidenced by the lead candidate of this crop, phase III asset Inclisiran by The Medicines Company.  If the remarkable safety profile holds up following about 2000 patient years of clinical experience, such a drug should be very widely prescribed, not least because it should enjoy great adherence, one of the major impediments of treatment success in cardiovascular disease.   

Undoubtedly, it has been the Inclisiran performance so far that has attracted the attention of players like Eli Lilly and Amgen, the latter of which, of course, should know particularly well about the competitive threat from RNAi having an antibody-based PCSK9 agent on the market (Repatha).  Beyond the upcoming slew of phase III read-outs with Inclisiran, it will equally be interesting to see the types of new targets being pursued and the clinical validation of targets like Apo(a) by the antisense competition.

AASLD Abstract Continues to Support Promise of ARO-HBV, but with a Twist

Yesterday, Arrowhead revealed the abstract for data on its new HBV RNAi drug candidate to be presented at the big annual Liver Meeting in November (AASLD).  The data continue to support highly potent knockdown of not only the surface antigen (HBsAg), but also other HBV components.

Dose response issues

When Arrowhead announced initial first-in-patient knockdown data from its 3^rd generation HBV RNAi candidate ARO-HBV, I found it suspicious for them to only reveal data for the 100mg and 200mg cohorts although more data was available at the time.  Curiously, the new data seem to suggest that there was no apparent benefit from going higher than 100mg in dose, at least when dosed with the current monthly frequency. 

Whether there is significantly worsening safety with increasing dose remains to be seen.

HBeAg positive/negative dichotomy

Similarly (but not as earth-shattering for sure) to the history of a prior HBV RNAi candidate by the company before, ARC-520, however, Arrowhead was able to learn more about its drug candidate as they went along in the study.  In particular, the first dose escalation cohorts (100, 200, 300, and 400mg monthly x3) encompassed a mix of HBeAg positive and negative patients, with 13 out of 16 being HBeAg negative.    

When Arrowhead then decided the last 2 cohorts to be just HBeAg positive, a remarkable increase in drug response was observed: whereas it took the predominantly HBeAg-negative patients 70-90 days to achieve 1.5log reductions in HBsAg, it looks like the pure HBeAg-positive patients only take 30-40 days to achieve the same.

Ergo, the reason why no clean dose response had been seen in the first cohorts is best explained by the fact that they were mixed and at that small cohorts.

Trigger choice likely explanation

ARO-HBV comprises 2 RNAi triggers: one that targets all (intact) HBV mRNA (X trigger) and one that makes sure the surface antigen is hit (S trigger) even in those patients with integrated HBV.  These typically lose the corresponding DNA element targeted by the X trigger during integration.

In the early days of RNAi, there was some controversy about the usefulness of using 2 or more triggers against the same target in terms of knockdown potency and specificity.  When I first started to practice RNAi in the lab in 2003, it was my experience that when you combined a very potent trigger with a less potent one, the knockdown was less than with the highly potent one alone.  As a result, I am a firm believer in the concept of RNAi trigger competition.

In the case of ARO-HBV it means that in HBeAg negative patients that have lost the X-trigger DNA, there will be one sterile/inactive trigger somewhat blunting the potency of the active one.

HBV biology is certainly complex and downstream events could also account for final knockdown differences.  Accordingly, in the HBeAg-only cohorts  it appears from the early observations that the nuc-experienced patients that in previous studies corresponded to patients that had lost the X-trigger-targeted elements by study enrollment not only responded as well, but in fact slightly better than the nuc-naïve patients.  It will therefore be important to learn more about their HBV integration status at AASLD to confirm or disprove the competition theory.

Review of Recent RNAi-Related Developments

The last 2 weeks have been busy ones in the lands of RNAi Therapeutics.  Here, I would therefore like to offer my take on the most important developments.

Alnylam’s Primary Hyperoxaluria Drug Breezes Through Clinic

With 20 subjects on Lumasiran, a GalNAc-RNAi targeting glycolate oxidase, for a median of 7 months, the investigational treatment for type I primary hyperoxaluria (PH1) ismore and more looking like a solid drug.  If the data presented last week at a Paediatric meeting in Turkey hold up in another 30 patients, it should fly through approval onto the market by the end of 2019.

While the relatively small numbers in each cohort has caused a bit statistical noise, it seemed like 3mg/kg monthly gives you an advantage over 1mg/kg monthly or 3mg/kg monthly in terms of the key biomarker urinary oxalate.  Interestingly, the company has chosen 3 times 3mg/kg monthly as the loading dose regimen in the now ongoing pivotal ILLUMINATE-A trial to be followed by dosing every 3 months. , the initiation of which the company has just announced.    

The core double-blind portion of the trial runs for only 6 months, so I am a bit puzzled how much the trial can inform on the value of the loading dose regimen and whether quarterly maintenance doses are sufficiently effective.   In any case, the trial design apparently was blessed by the FDA (incl. the urinary oxalate lowering primary endpoint), so surely they will know (e.g. based on preclinical animal data).

Regarding the competition with the primary hyperoxaluria drug candidate from Dicerna, the approximately 2/3 lowering of urinary oxalate and essentially all patients getting into a range considered safe and an unremarkable safety profile sets a high hurdle for the upcoming data presentation of DCR-PHXC at ASN later this month.

Arbutus HBV-RNAi Drug About to Die   

Yesterday, Arbutus provided an update on its LNP-enabled RNAi drug candidate for the treatment of chronic HBV (ARB-1467) and it does not bode well.  Similar to most other drug candidates attempted and barely tried, ARB-1467 should be canned in the not-too-distant future. 

In a combination study testing ARB-1467 in chronic HBV patients on nucleoside reverse transcriptase inhibitor tenofovir, probably only 1 in 6 patients hit a pre-defined criteria in terms of HBsAg lowering that would allow the patient to then receive immune booster PEG-Interferon.  The not very forthcoming revelation and the fact that the data was mentioned even after dropping another shoe that its small molecule HBV RNA destabilizer is also biting the dust makes it clear that not even the company sees much value in ARB-1467.

What an utter disaster this company has been since its inception as a HBV solutions entity.

Arrowhead Early HBV Deal Further Validates

Last week, shareholders in Arrowhead Pharmaceuticals got a lesson in biotech investing as it shares have given up ~1/3 of its value following a nice deal with Johnson&Johnson for the leading HBV knockdown asset in the space, ARO-HBV.

The deal gives Arrowhead a solid $250M in financing, including a $175M upfront fee and a $75M investment in company stock at a premium of ~50% to current trading.  While this avoids an imminent dilutive secondary share issuance- the company had been running low of cash- the ‘up to 15%’ in royalties from future sales of early phase II-stage ARO-HBV is clearly disappointing.  The relatively low royalty despite of it having confirmed strong HBsAg knockdown in patients can be explained with the fact that Arrowhead has avoided bearing the full risk of having to show proof-of-concept of HBV control.  This despite of having earlier paraded results obtained with an earlier DPC-based RNAi candidate (ARC-520) as strong evidence that RNAi can achieve such immune control.

While Arrowhead got punished for playing it safely, it can now focus on commercial home-run indications with highly validated targets and transition to being a broad platform company with a wholly owned attractive lead candidate in ARO-AAT.  Indeed, Arrowhead may emerge as the leading RNAi company as Alnylam, with a market cap ~8x that of Arrowhead, is still burdened by late-stage RNAi drugs with suboptimal specificity.

While humiliating, this serves Alnylam as a good reminder to also value innovation by the direct competition (note: specificity-enhancing technology now adopted by Alnylam has been available for a decade and could have been had for peanuts, e.g. from now defunct RNAi play mdRNA/Nastech).  Fittingly, today long-time archrival Silence Therapeutics issued a press release indicating that Alnylam is playing hard-ball with regard to Silence-owned IP purportedly covering ONPATTRO.

My guess is that Alnylam would rather risk an injunction and deprive patients of a very good medicine than to submit to what appear to me legitimate demands of a competitor.

Akcea’s antisense drug for TTR amyloidosis gets FDA nod

Last Friday, Akcea’s TTR drug TEGSEDI (licensed from Ionis) finally got FDA marketing approval for patients suffering from TTR-related polyneuropathy.  As expected from the delay in the approval process, TEGSEDI’s approval is accompanied by hefty black box warnings highlighting thrombocytopenia and renal risks of the (non-GalNAc) phosphorothioate oligonucleotide.  

Furthermore, the REMS program calls for frequent blood monitoring, essentially negating the claimed at-your-home convenience advantage over competing RNAi drug ONPATTRO.  Add to the poor safety profile clear efficacy disadvantages and pricing at parity with ONPATTRO, ONPATTRO should clearly win out in the marketplace.

Having said that, the TTR community is relatively small and key opinion leaders with relationships to a given drug company tend to support the drugs from the same company.