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.