Big Pharma Investments in RNA Editing

When it comes to new platform technologies, investors generally like to see their belief validated by large pharmaceutical companies.  In addition to confirming the soundness of the scientific approach, in times when access to capital is constrained, such partnerships also provide an important financing source.

In RNA Editing, Venture Capital certainly has taken the charge (and risk) by investing close to $600M in Series As and Bs spread between Korro Bio, Shape Therapeutics, EdiGene and ADARx (the last two are not pure-plays) largely in 2020-1.  There have, however, been two notable Big Pharma deals that materialized in the second half of 2021.

 

Shape Therapeutics-Roche

In August 2021, Shape Therapeutics announced its first Big Pharma partnership.  Shape apparently has been working on the DNA-directed expression of editing RNAs harnessing endogenous ADARs, especially in the CNS.  Their favourite delivery vehicle is AAV viral delivery.

It is an interesting approach, since despite of going through the trouble of gene therapy-type delivery, they choose not to bring exogenous ADARs along for the ride.  This makes sense since overexpression of ADARs is linked to widespread off-targeting and the molecular size of ADAR may be a vector capacity issue, too.  As it would have involved essentially naturally occurring ADARs (plus/minus a few optimizing mutations), the cost in terms of immunogenicity though may have been tolerable.  This is in stark contrast to genome editing technologies like CRISPR where, because of delivery in the CNS, you would likely have to deal with the extended expression of entirely foreign proteins.

Shape and Roche will tackle a number of neuronal diseases together, likely Alzheimer’s, Parkinson’s and more rare indications like Rett Syndrome.  Of note, Roche has suffered a major setback in oligonucleotide-based neurodegenerative drug development when efficacy and tox issues derailed a late-stage Huntington’s disease drug candidate based on the intrathecal administration of phosphorothioate antisense molecules.  So for them opting for AAV-based expression of targeting RNAs is worth taking note of.

Rett Syndrome is a truly intriguing indication highlighting a few of the unique advantages of RNA Editing.  Rett Syndrome affects ~1 in 10-15k female births.  It is a severe, early onset neurodevelopmental disorder caused by too little MeCP2 expression due to mostly spontaneous (as opposed to inherited) mutations.  Nevertheless, persons suffering from this X-linked gene condition can still live into their 40s and 50s- with severe disabilities. There are no drugs approved specifically addressing Rett Syndrome. 

Rett Syndrome would seem like an ideal candidate for the development of gene therapy.  What makes, however, gene therapy particularly challenging in this setting is that while too little of the master epigenetic regulator that MeCP2 is gives you Rett Syndrome, too much of it is neurotoxic.  Add X chromosome inactivation mosaicism into the mix and the therapeutic window of MeCP2 expression narrows dramatically:

for each (neuronal) cell just enough to give you MeCP2 function, but not more, certainly not >2x normal MeCP2 expression.

As a technology that does not change the rate of gene transcription, RNA Editing is ideally suited for Rett Syndrome and it is estimated that 40-50% of cases can be addressed by the technology.  The downside is that in order to address all of those mutations, similar to Duchenne’s and exon skipping, a number of RNA editing molecules would have to be developed.

 

ProQR-Eli Lilly

A month following the Shape deal, ProQR announced a partnership with Eli Lilly for up to 5 targets in the liver and CNS. This was accompanied by a $20M upfront consideration and a $30M equity investment.

Unlike Shape, ProQR (pronounced ‘Procure’) is pursuing a more traditional approach to drug development in the form of synthetic oligonucleotides for A-to-I editing.  Eli Lilly has shown great commitment to RNA Therapeutics for a while now with for example two RNAi compounds licensed from Dicerna (now part of Novo Nordisk) in clinical development for two cardiometabolic indications and a recent whopping $700M investment into a Genetic Medicine research site for RNA- and DNA-based drug development.  In the CNS, Eli Lilly will be interested in applying the new platform to the usual suspects including Alzheimer’s and pain.

 

As RNA Editing is moving into the clinic (Wave Life Sciences, alpha-1-antitrypsin) and more people hear about the platform and come up with great ideas of where to apply it, but also as oligonucleotide therapeutics more and more becomes part of the mainstream pharma mindset, I expect additional Big Pharma deals to materialize soon.