From ZZ to SZ to MZ to potentially MM! The New State of Play for RNA Editing in Alpha-1 Antitrypsin Disease

The last few days and weeks delivered critical datapoints in the race to develop RNA Editing oligonucleotides for the treatment of AATD.  The prize in the form of serving an inadequately addressed rare disease with low single digit hundred thousand ZZ patients in the US, Europe, and Japan is enormous, thus spurring the development of increasingly better RNA Editing candidates.  Capitalism at its best. 

Getting close to the RNA Editing endgame

The picture that emerges shows Wave Life Sciences leading the pack with a clinical profile that could match the less severe SZ genotype (in terms of serum AAT abundance).  This should provide protection against progression of lung (but not liver) disease.  It has an about 2 years headstart in clinical development over competitor AiRNA which has a more realistic shot at replicating the more protective MZ genotype based on comparative mouse studies; and another year over Korro Bio’s AATD encore KRRO-111.  If what they claim is true, they may be getting close to the endgame with near complete Z-correction (MM-like), in the process surpassing what genome editing can do as well.

WVE-006

Wave Life Sciences’  WVE-006 has been discussed a lot on this blog.  I feel like I am slowly getting a handle on the true efficacy of this compound in the clinic- which has been made difficult by the company not broadly providing total serum AAT values.  Instead, it relied on revealing isolated serum M-AAT, the percent reduction of Z-AAT, and somewhat meaningless mean max numbers for total AAT.  Somewhat meaningless, because AAT fluctuates and just capturing the maximum values ever observed clearly introduces a significant bias to the upside.  

Considering that their reported ‘mean max’ barely matches what they say their assay measures for the mean (not even mean max) in ZZ natural history (13.1uM), it cannot be concluded that WVE-006 will achieve protection from progression of lung disease as expected from a MZ-like genotype and will likewise not be potent against AAT liver disease.  Accordingly, the case study they report on where a subject experiences an acute response shows total (Z) AAT serum levels to be similar, if not higher pre-treatment.  So if we wanted to analogize, something more akin to introducing a SZ-type genotype into a ZZ carrier should be the expectation.

AIR-001

Privately-held, pure-play RNA Editing company AiRNA announced having dosed their first clinical trial subject with AIR-001 last month.  AIR-001 is also a GalNAc-conjugated oligonucleotide and its preclinical mouse results have just been presented at the annual ASGCT conference in Boston.

In the same NSG-piz mouse model that Wave Life Sciences is using, and for the same 10mg/kg biweekly subcutaneous dosing regime, AIR-001 appears to achieve somewhat increased levels of RNA editing which in turn translated to somewhat increased serum M-AAT fractions (both up from ~50% to 60%).  Based on the prolonged stability of AIR-001 in monkey over mouse livers, AiRNA predicts a dosing frequency every 2 or 3 months which would be an improvement from Wave’s potential monthly dosing.

AIR-001 is just preclinical and WVE-006 has cleared a number of clinical safety and efficacy hurdles.  Getting closer to having a true MZ-genotype impact could be a best case scenario for AIR-001.

KRRO-111

To rain on everybody’s parade, Korro Bio then PR’d stunning headline results for its new AATD RNA Editing candidate.  KRRO-111 is its GalNAc oligonucleotide version after its LNP-based KRRO-110 seemed to do nothing in the clinic and the company may have to climb a mountain of investor skepticism before they all come onboard.

Still, by reporting near complete Z-AAT elimination and almost full M-AAT reconstitution with repeat-dosing of 3mg/kg in mice, and at one third the dose of the competition at that, one truly has to wonder whether we are closing in on the endgame for RNA Editing in AATD: from ZZ to MM.  The numbers also sound to be better than a single-shot of genome editing ever will be.  Beam Therapeutics conservatively itself bills BEAM-302 as MZ, though I myself believe that based on the >9:1 serum M:Z ratio, they are approaching something more like MM.

Unlike many biotech investors right now which can be grouped into CRISPR haters and lovers, I myself welcome the emerging choice for AATD patients.  Let us not forget that as alveolar damage from too little alpha-1 antitrypsin is not reversible (liver fibrosis may be) and gradual suffocation is an awful way to die (trust me).  The true AATD medical endgame would therefore also involve treating ZZ carriers as early as possible, certainly before symptoms emerge.  A genome editor would have to have an LNP delivery safety profile such that a person in her early 20s could be routinely administered; an RNA Editor convenient and sufficiently tolerated such that a carrier would be willing to repeatedly inject himself despite having no symptoms.

Disclosure: I am currently long Beam Therapeutics and Korro Bio.  No position in Wave Life Sciences as I want to sit out the feedback they will receive from the FDA on the development path for WVE-006.  Not investment advice.