Preclinical Toxicological Assessment of A Novel siRNA, SLN360, Targeting Elevated Lipoprotein (a) in Cardiovascular Disease

Abstract

SLN360 is a liver-targeted N-acetyl galactosamine (GalNAc)-conjugated siRNA with a promising profile for addressing Lp(a)-related cardiovascular risk. Here we describe the findings from key pre-clinical safety studies. In vitro, SLN360 specifically reduced LPA expression in primary human hepatocytes with no relevant off-target effects. In rats, 10mg/kg subcutaneous SLN360 was distributed specifically to the liver and kidney (peak 126 or 246 mg/g tissue at 6h respectively), with <1% of peak liver levels observed in all other tested organs. In vitro, no genotoxicity and no effect on human Ether-a-go-go Related Gene currents or pro-inflammatory cytokine production was observed, while in vivo, no SLN360-specific antibodies were detected in rabbit serum. In rat and non-human primate 29-day toxicology studies, SLN360 was well tolerated at all doses. In both species, known GalNAc-conjugated siRNA-induced microscopic changes were observed in the kidney and liver, with small increases in alanine aminotransferase and alkaline phosphatase observed in the high dose rats. Findings were in line with previously described siRNA-GalNAc platform-related effects and all observations were reversible and considered non-adverse. In cynomolgus monkeys, liver LPA mRNA and serum Lp(a) were significantly reduced at day 30 and after an 8-week recovery period. No dose-related changes in safety assessment endpoints were noted. No SLN360 induced cytokine production, complement activation or micronucleus formation was observed in vivo. The toxicological profile of SLN360 presented here is restricted to known GalNAc siRNA effects and no other toxicity associated with SLN360 has been noted. The pre-clinical profile of SLN360 confirmed suitability for entry into clinical studies.

Targeted Treatment against Lipoprotein (a): The Coming Breakthrough in Lipid Lowering Therapy

“…In an in vivo study using cynomolgus monkeys, it was found that SLN360 caused up to 95% reduction in serum Lp(a) concentration and, importantly, this effect was long-lasting [63]. Toxicological analyzes, both in vitro and in vivo, showed satisfactory safety of using SLN360 [64].…”

Targeting Lipoprotein(a): Can RNA Therapeutics Provide the Next Step in the Prevention of Cardiovascular Disease?

“…This innovative siRNA targets the LPA mRNA and consequently lowers apo(a) expression [ 14 , 181 ]. It consists of a 19-mer siRNA modified with GalNAc [ 14 , 181 , 182 ].…”

Lipoprotein(a) and Atherosclerotic Cardiovascular Disease: Where Do We Stand?

“…Various subcutaneous doses ranging from 0.1 to 9.0 mg/kg were administered, with the minimally effective dose identified as 0.3 mg/kg. Importantly, no evidence of inflammation, cytokine production, complement stimulation, or micronucleus formation associated with SLN360 use, was found [ 244 , 245 ]. Toxicology studies in rats further supported the tolerability of SLN360 in all doses tested [ 245 ].…”

“…Importantly, no evidence of inflammation, cytokine production, complement stimulation, or micronucleus formation associated with SLN360 use, was found [ 244 , 245 ]. Toxicology studies in rats further supported the tolerability of SLN360 in all doses tested [ 245 ].…”

“…As a result, inhibition of the Lp(a) formation is observed ( D ). AAV facilitates the transfer of CRISPR in the liver, where CRISPR disrupts the LPA gene, resulting in the removal of Lp(a) particles from the plasma [ 236 , 237 , 238 , 239 , 240 , 241 , 242 , 243 , 244 , 245 , 246 , 247 , 248 , 249 , 250 , 251 , 252 , 253 , 254 ]. Abbreviations: AAV: adeno-associated virus; apo(a): apolipoprotein(a); ApoB100: apolipoproteinB100; ASGPR, Asialoglycoprotein receptor; ASO: antisense oligonucleotide; CRISPR: Clustered Regularly Interspaced Short Palindromic Repeat; GalNAc: N-Acetylgalactosamine; KIV: kringle IV; Lp(a): lipoprotein(a); mRNA, messenger RNA; RISC: RNA-induced silencing complex; RNAase: ribonuclease; siRNA: small-interfering RNA.…”