Pre-clinical data show that RNAi effectively knocks down lipid metabolism targets

Pre-clinical data of investigational RNAi directed at genetically validated targets in development for the treatment of cardiovascular metabolic diseases have been presented at the AHA Scientific Sessions last November. The data include results of phase I studies with ALN-PCSsc targeting PCSK9 for the treatment of hypercholesterolemia; ALN-AC3 targeting apolipoprotein C3 (apoC3) for the treatment of hypertriglyceridemia; and ALN-ANG targeting angiopoietin-like 3 (ANGPTL3) for the treatment of genetic forms of mixed hyperlipidemia and severe hypertriglyceridemia.

Multi-dose data in non-human primates (NHPs) with over six months of dosing for ALN-PCSsc showed robust and clamped knockdown of PCSK9 of up to 92% and reductions in LDL-C of up to 77% with a once-monthly subcutaneous dosing regimen. Recently, the RNAi therapeutics company Alnylam filed and received approval for a Clinical Trial Application (CTA) for ALN-PCSsc, and now expects to start the Phase 1 trial before year's end with initial clinical data expected in mid-2015.

"ALN-PCSsc is a first-in-class PCSK9 synthesis inhibitor that we believe represents an innovative, differentiated, and well-validated approach for the treatment of hypercholesterolemia. Our new non-human primate studies confirm the potential for a once-monthly, and possibly once-quarterly, low volume subcutaneous dose regimen. Further, the mechanism of action for ALN-PCSsc enables LDL-C lowering independent of baseline PCSK9 plasma levels, which we believe could result in additive or even synergistic activity in combination with statins." said Rachel Meyers, Ph.D., Vice President, Research and RNAi Lead Development at Alnylam.

ALN-PCSsc is a subcutaneously administered RNAi therapeutic that utilizes Alnylam's proprietary Enhanced Stabilization Chemistry (ESC)-GalNAc-siRNA conjugate delivery platform. ESC-GalNAc-siRNA conjugates are designed to achieve targeted delivery of RNAi therapeutics to hepatocytes through uptake by the asialoglycoprotein receptor, and enable subcutaneous dosing with increased potency and durability and a wide therapeutic index. The new pre-clinical NHP studies showed that monthly subcutaneous administration of ALN-PCSsc resulted in PCSK9 knockdown of up to 92% and LDL-C lowering, in the absence of statin co-administration, of up to 77%; mean maximum knockdown of PCSK9 was 83.2% +/- 7.2%, and mean maximum LDL-C reduction was 59.0% +/- 13.3%. As a PCSK9 synthesis inhibitor, ALN-PCSsc showed rapid, durable, and clamped knockdown of PCSK9 and reduction of LDL-C.

The Phase 1 trial of ALN-PCSsc will be conducted as a randomized, single-blind, placebo-controlled, single- and multi-dose, dose-escalation study. The study is designed to enroll up to 76 healthy volunteer subjects with elevated baseline LDL-C (≥ 100 mg/dL), with subjects randomized 3:1, drug:placebo. The study will be performed in two phases: a single ascending dose (SAD) phase and a multiple dose (MD) phase. In the MD phase, subjects will receive two doses of either ALN-PCSsc or placebo administered four weeks apart. The MD phase will also include subjects both on and off statin co-medication. The primary objective of the Phase 1 study is to evaluate the safety and tolerability of ALN-PCSsc. Secondary objectives include assessment of clinical activity as determined by knockdown of plasma PCSK9 levels and serum LDL-C levels, as well as pharmacokinetics of ALN-PCSsc. In support of the approved CTA, Alnylam has completed toxicology studies in rodents and NHPs. In both species, the no observed adverse effect level (NOAEL) was determined to exceed 250 mg/kg, the top dose in both studies, with no adverse findings in clinical, hematology, laboratory chemistry, and histopathology assessments.

ALN-AC3 is a subcutaneously administered investigational RNAi therapeutic targeting apoC3 for the treatment of hypertriglyceridemia. ApoC3 is a component of lipoprotein particles in the blood; it inhibits lipoprotein lipase and hepatic lipase, reducing hepatic uptake of triglyceride-rich particles. Polymorphisms in apoC3 have been associated with hypertriglyceridemia; specifically, a gain-of function phenotype leads to higher apoC3 and triglyceride levels, and reduced triglyceride clearance. In contrast, loss-of-function mutations in apoC3 result in greater triglyceride hydrolysis into free fatty acids and increased triglyceride clearance; heterozygous individuals have lower triglycerides and lower levels of very low density lipoprotein (VLDL).
The new data presented were from studies conducted in mouse models that match human genetics. Specifically, a single 3 mg/kg dose of a GalNAc-conjugated siRNA targeting apoC3 resulted in knockdown of apoC3 levels of up to 94%, with more than 60% knockdown sustained for at least 30 days. In a multi-dose study, results showed that dosing of 3 mg/kg every other week resulted in 96% knockdown of human apoC3 through day 35, the last time point in the study.

In addition to ALN-PCSsc and ALN-AC3, Alnylam is also advancing ALN-ANG, an investigational RNAi therapeutic targeting ANGPTL3 for the treatment of genetic forms of mixed hyperlipidemia and severe hypertriglyceridemia. ANGPTL3 is an inhibitor of cellular lipases involved in the metabolism of lipoproteins. New data presented at AHA demonstrated that a single dose of a GalNAc-siRNA targeting ANGPTL3 led to robust, dose-dependent knockdown of serum ANGPTL3 protein of up to 99%, with a single dose ED₉₀ of approximately 1 mg/kg. In studies performed in an "ob/ob" mouse model of obesity and mixed hyperlipidemia, ALN-ANG treatment as a single 3 mg/kg dose resulted in a greater than 80% reduction in levels of triglycerides and LDL-C. In addition, total cholesterol was reduced up to 68%.
Press release Alnylam Pharmaceuticals November 17 2014