Inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9) reduce low-density lipoprotein (LDL) cholesterol and are used for treatment of dyslipidemia. Current PCSK9 inhibitors are administered via subcutaneous injection. We present a highly potent, chemically modified PCSK9 antisense oligonucleotide (ASO) with potential for oral delivery. Past attempts at oral delivery using earlier-generation ASO chemistries and transient permeation enhancers provided encouraging data, suggesting that improving potency of the ASO could make oral delivery a reality. The constrained ethyl chemistry and liver targeting enabled by N-acetylgalactosamine conjugation make this ASO highly potent. A single subcutaneous dose of 90 mg reduced PCSK9 by >90% in humans with elevated LDL cholesterol and a monthly subcutaneous dose of around 25 mg is predicted to reduce PCSK9 by 80% at steady state. To investigate the feasibility of oral administration, the ASO was coformulated in a tablet with sodium caprate as permeation enhancer. Repeated oral daily dosing in dogs resulted in a bioavailability of 7% in the liver (target organ), about fivefold greater than the plasma bioavailability. Target engagement after oral administration was confirmed by intrajejunal administration of a rat-specific surrogate ASO in solution with the enhancer to rats and by plasma PCSK9 and LDL cholesterol lowering in cynomolgus monkey after tablet administration. On the basis of an assumption of 5% liver bioavailability after oral administration in humans, a daily dose of 15 mg is predicted to reduce circulating PCSK9 by 80% at steady state, supporting the development of the compound for oral administration to treat dyslipidemia.

Current PCSK9 inhibitors are administered via subcutaneous (SC) injection. Here, we present a highly potent, chemically modified PCSK9 antisense oligonucleotide (ASO) with potential for oral delivery. Past attempts at oral delivery using earlier ASO chemistries and intestinal permeation enhancers provided encouraging data, suggesting that improving potency of the ASO could make oral delivery a reality. The constrained ethyl chemistry and liver targeting enabled by tri-antennary N -acetyl galactosamine (GalNAc) conjugation make this ASO highly potent. A single SC dose of 90 mg reduces PCSK9 by >90% in humans with elevated LDL-C (A), and a once monthly SC dose of 25 mg ([20, 30], 90% CI) is predicted to reduce PCKS9 by 80% at steady-state. To investigate the feasibility of oral administration, we developed an oral solid tablet wherein the ASO is co-formulated with a transient permeation enhancer. Repeated oral daily dosing of tablets to dogs resulted in a bioavailability of 7% in the liver (target organ), approximately 5-fold greater than the plasma bioavailability (B). Favourable liver uptake following oral administration is supported by similar bioavailability in plasma and kidney. Since the ASO is not active in rodents or dogs, we used a rat-specific GalNAc- Malat-1 ASO with the same chemistry to confirm target engagement. Intrajejunal administration resulted in ≥78% mRNA knockdown in the liver for single doses of 3-40 mg/kg. A monkey tolerability study of the PCSK9 ASO further supports oral feasibility with all tested doses (28-56 mg/day) significantly reducing LDL-C already after 7 days of daily oral dosing. Based on available animal and human data, and an assumption of 5% oral bioavailability in humans, a daily dose of 15 mg ([10, 20], 90% CI) in man is predicted to reduce PCSK9 in plasma by 80% at steady-state. This supports the development of the compound for subcutaneous and oral administration to treat dyslipidemia.