Oligonucleotide drugs have limited ability to cross the cell membrane and are often trapped in the endosome, sequestered from their targets. Cell penetrating peptides (CPP) are intended to overcome this limitation and improve oligonucleotide delivery to muscle. First generation CPPs, such as the poly-arginine peptides (R6G) and Pip (PNA/PMO internalization peptide) peptides, demonstrate superior muscle delivery of PMOs (phosphorodiamidate morpholino oligonucleotide), compared to “naked” PMOs, however they also demonstrate safety liabilities at higher doses limiting their therapeutic potential. PepGen’s enhanced delivery oligonucleotide (EDO) technology consists of extensively evolved next-generation CPPs, empirically designed to address these challenges.
Effective parenteral delivery of oligonucleotide drugs to muscle and other cells requires improved plasma stability, increased cellular uptake and effective endosomal escape. Further, these should be achieved at therapeutic dose levels that are well tolerated to permit the repeat dosing required of a chronic therapy. The EDO CPPs were designed to include two short, positively charged poly-arginine sequences, stabilized with non-natural, non-immunogenic amino acids, flanking a short, engineered hydrophobic core to improve these properties.
We show here that the EDO CPPs are indeed superior in all these key attributes and showed higher efficacy compared to naked PMOs and R6G-PMOs. With the EDO technology, we have previously demonstrated up to 25-fold higher (vs naked PMO) nuclear delivery in myotubes. This reflected superior cellular uptake and endosomal escape in cells. In vivo, this translated into higher nuclear delivery in non-human primates and healthy volunteers (HV). In a post-hoc analysis of our PGN-EDO51 Phase 1 HV single ascending dose (SAD) study of bicep biopsies, we observed up to approximately 50% of muscle cell nuclei positive with EDO51 oligonucleotide. We previously reported that following this single dose of EDO51 in HV, we observed up to 2% exon skipping in biceps.
Based on these and other studies, the EDO technology is being employed in investigational treatments for Duchenne muscular dystrophy (DMD) targeting exon 51 skippable mutations (PGN-EDO51) now in Phase 2 clinical studies in patients, myotonic dystrophy type 1 (PGN-EDODM1) currently in a Phase 1 clinical trial in patients and DMD targeting exon 53 skippable patients (PGN-EDO53) in preclinical development.