Systemic Characterization of Novel Lipidated siRNA Conjugates

PROJECT SUMMARYOligonucleotide therapeuticslike siRNAare attractive because they target messenger RNA and thuscan modulate the expression of protein targets that are inaccessible to small moleculesantibodies and peptidesChallenges identifying safe and effective ways to deliver siRNA therapeutics into cells outside of the liver have greatly limited the expansion of oligonucleotides as a therapeutic classDTx Pharma has identified a lipid motif that when covalently coupled to siRNA enables its activity in vivo in musclefatheartlung and liver following systemic administrationDTx lipidated siRNA is also highly efficacious ex vivo in primary cells such as musclefatstellateendothelial and neuronal cells and at least an order of magnitude more potent at repressing mRNA expression relative to conjugates of other fatty acids that have been previously describedThese preliminary data are highly encouraging and appear unique relative to other technologies reported to enable delivery of siRNA in vivohoweverwe have generated very limited in vivo data with DTx conjugated siRNAs and are yet to explore characteristics like mode of actionbioavailabilitysafety or relative activity compared to GalNAc and cholesterolthegold standardconjugation approaches for delivery of siRNA to and beyond the liverrespectivelyAdditionallywe are yet to apply learnings from the successful development of lipidated peptide therapeutics that are likely to enhance the activity of our original lead in tissues outside of the liverIn SAa novel lipid siRNA conjugateDTx EABwith enhanced affinity for albumin butsimilar activity in primary cells in the absence of albumin to the DTx conjugated siRNA described abovewill be evaluated in vivo in mice against the original conjugate for its ability to deliver siRNA beyond the liverThis novel conjugate was designed based on knowledge of half life extension from peptide biologics and is expected to be far more potent at repressing mRNA expression in tissues outside of the liver because its enhanced albumin binding affinity will prolong residence time in circulation and increase exposure to these tissuesIn SAwe will advance our knowledge of the mode of actionbioavailabilitysafety and relative activity of DTx EAB and the original DTx conjugated siRNA compared with GalNAc and cholesterolAn analytical PK assay will be developed to understand whether any increased activity of DTx EAB over cholesterol conjugates is likely due to half life extension in the circulationIn the final aimSAwe will test whether DTx EAB technology can be leveraged to improve outcomes in the mouse mdx model of muscular dystrophyTherapeutics targeting myostatinlike cholesterol conjugated myostatin siRNAenhance muscle mass in animal modelsDTx EAB and cholesterol myostatin siRNA conjugates will be compared in the mdx model with the goal of demonstrating that DTx technology is far more potent at improving outcomes and thusat delivering siRNA to muscleEvaluation of the mode of actionthe tissues to which DTxconjugates deliver siRNA toand the relative efficacy and safetyacross theseaims will allow us to select indications and siRNA targets where this delivery approach is likely to have a meaningful benefit NARRATIVEDespite enormous potential to access therapeutic targets that small moleculesantibodies and peptide biologics cannot reachthe success of oligonucleotide therapeutics as a class has been limited due to challenges delivering them into cells and tissues outside of the liverDTx Pharma has developed a technologybased on the covalent conjugation of long chain fatty acidsLCFAsto oligonucleotidesthat enables the delivery and activity of siRNA in vivo outside of the liver and ex vivo to multiple primary human cell types including T cellsmuscle cellsendothelial cellsadipocytesstellate cells and trabecular meshwork cellsIt is anticipated that this technology will expand the reach of oligonucleotide therapeutics beyond the liver and unlock this class of therapeutics for treatment of cardiovascularimmunemuscularneurodegenerative and ocular diseasesas well as other diseases where decreased expression of a gene target may be of benefite ggenetic disease driven by dominant gain of function mutations