Wave Life Sciences researchers have published positive preclinical proof-of-concept data showing the company’s adenosine deaminase acting on RNA (ADAR)-mediated RNA base editing technology to deliver potent, durable, and specific edits in non-human primates (NHPs)—as well as a broader potential for therapeutic applications in the liver.
The publication marks what the researchers reported was the first time that RNA base editing in NHPs has been achieved through a simplified oligonucleotide approach.
In results published in Nature Biotechnology, the Wave researchers reported that the company’s GalNAc-conjugated adenine (A)-to-inosine (I) RNA base editing oligonucleotides or “AIMers” were able to edit up to 50% of ACTB (Beta-actin) transcript in the livers of NHPs, with levels of editing remaining as high as 40% for more than one month.
AIMers are designed to avoid the permanent changes to the genome that occur with DNA-targeting approaches by correcting single base mutations in an RNA transcript. Instead of applying an exogenous editing enzyme, AIMers use ADAR enzymes, proteins that exist in the body and possess the natural ability to change an A to an I,s which cells read as guanine (G).
That approach, Wave asserted, avoids the risk of irreversible off-target effects of DNA-targeting approaches and enables simplified delivery.
Because I is read as G translational machinery, Wave reasons, sequence-directed editing with ADAR has the potential to revert transcripts with single G-to-A point mutations that cause genetic diseases.
It is estimated that there are more than 32,000 pathogenic single nucleotide polymorphisms, of which about 50% may be ADAR amenable. In addition, A-to-I(G) editing could potentially address non-genetic diseases through modulation of post-translational modifications or protein-protein interactions, the company added.
AIMers are short, fully chemically modified, and use novel chemistry—including proprietary PN backbone modifications and chiral control—that make them distinct from other ADAR-mediated editing approaches. According to the researchers, AIMers can be taken up by several cell types with high editing efficiency under gymnotic conditions in vitro and are amenable to GalNAc conjugation, a validated ligand for clinical delivery to the liver.
Sufficient ADAR activity exists in cells to support therapeutic use without disrupting the natural functions of ADAR enzymes in the body, the Wave researchers added.
“Significant step”
“Efficient in vivo DNA or RNA base editing has historically relied on co-administration of engineered exogenous enzymes such as CRISPR/Cas9 with lipid nanoparticles or viral vectors, complicating delivery and specificity. Our approach does not, and therefore this publication represents a significant step forward for the genetic medicines field,” said Chandra Vargeese, PhD, CTO at Wave Life Sciences.
The paper also summarized foundational design principles that enabled Wave to achieve potent, durable editing with high specificity and exposure through short chemically modified oligonucleotides with simplified delivery.
“Since the generation of these data, we have continued to evolve our AIMer designs, allowing us to further optimize editing efficiencies across multiple targets, cell types, and tissues, and establish versatile therapeutic platform technology,” Vargeese added.
The researchers also showed AIMers to be highly specific in vitro and in vivo, based on transcriptome-wide analyses. In the in vivo study on NHPs, no signs were seen of hepatoxicity at two days post-dose, when AIMer levels in the liver were high. All animals exhibited ALT and AST levels within or below the historical data range.
Early-generation AIMers designed to correct the Z mutation in SERPINA1 transcript—the most common cause of alpha-1 antitrypsin deficiency (AATD)—supported high levels of RNA editing, which increased the amount of functional alpha-1 antitrypsin (AAT) protein secreted from primary hepatocytes in vitro.
“We are rapidly working towards selecting our first AIMer development candidate for AATD, with IND-enabling toxicology studies planned to initiate in the third quarter of this year,” Paul Bolno, MD, Wave’s president and CEO, said in a statement. “We also are expanding our discovery work in the CNS and liver, and we expect AIMers to become a significant component of our pipeline in the future.”
“The vast potential therapeutic applications for AIMers, enabled by unique chemistry modifications and the creativity of Wave’s scientists, and these compelling proof-of-concept data underscore the many reasons we are excited about this new therapeutic modality,” Bolno added.
Wave has separately shared in vivo data for its AATD program, where AIMer treatment in a transgenic mouse model resulted in approximately 60% editing of SERPINA1 transcript and circulating AAT serum levels (18.5 uM) approximately five-fold greater than PBS-treated controls at 19 weeks. Wave has also shared histological analyses that indicate reduction of liver aggregates in a transgenic mouse model at 19 weeks with AIMer treatment.
Guiding principles
In their paper, the Wave researchers shared a set of guiding principles for the design of AIMers by analyzing the relationship between chemical modifications and editing activity. They said control of backbone stereochemistry and the use of judiciously placed PN backbone modifications can improve editing activity—both features of Wave’s PRISM™ discovery and drug development platform.
PRISM is designed to enable genetically defined diseases to be targeted with stereopure oligonucleotides across multiple therapeutic modalities, including silencing, splicing, and editing. PRISM combines the company’s ability to construct stereopure oligonucleotides with insight into how oligonucleotide sequence, chemistry, and backbone stereochemistry impact key pharmacological properties.
In earlier preclinical studies, Wave researchers showed that AIMers do not need complex delivery vehicles such as viral vectors or lipid nanoparticles to achieve durable editing in the liver, central nervous system (CNS), and other tissues.
Beyond targeting the transcriptome to correct point mutations, Wave said it is also exploring the use of AIMers to treat non-genetic diseases through modulation of protein-protein interactions. The company recently provided proof-of-concept in vitro at the Deaminet 2022 conference.
“RNA base editing represents the next frontier of precision medicine and we have only begun to realize its potential. We look forward to contributing additional publications in the future as we continue driving this science,” Bolno added.