The Nonclinical Safety Profile of GalNAc-conjugated RNAi Therapeutics in Subacute Studies

Abstract

Short interfering RNAs (siRNAs) and antisense oligonucleotides (ASOs) are the most clinically advanced oligonucleotide-based platforms. A number of N-acetylgalactosamine (GalNAc)-conjugated siRNAs (GalNAc-siRNAs), also referred to as RNA interference (RNAi) therapeutics, are currently in various stages of development, though none is yet approved. While the safety of ASOs has been the subject of extensive review, the nonclinical safety profiles of GalNAc-siRNAs have not been reported. With the exception of sequence differences that confer target RNA specificity, GalNAc-siRNAs are largely chemically uniform, containing limited number of phosphorothioate linkages, and 2’-O-methyl and 2’-deoxy-2’-fluoro ribose modifications. Here, we present the outcomes of short-term (3–5 week) rat and monkey weekly repeat-dose toxicology studies of six Enhanced Stabilization Chemistry GalNAc-siRNAs currently in clinical development. In nonclinical studies at supratherapeutic doses, these molecules share similar safety signals, with histologic findings in the organ of pharmacodynamic effect (liver), the organ of elimination (kidney), and the reticuloendothelial system (lymph nodes). The majority of these changes are nonadverse, partially to completely reversible, correlate well with pharmacokinetic parameters and tissue distribution, and often reflect drug accumulation. Furthermore, all GalNAc-siRNAs tested to date have been negative in genotoxicity and safety pharmacology studies.

Nonclinical Safety Profile of Revusiran, a 1st-Generation GalNAc-siRNA Conjugate for Treatment of Hereditary Transthyretin-Mediated Amyloidosis

“…The minimal necrosis and vacuolation in spleen observed acutely were not observed in subsequent repeat-dose toxicity studies in rats. The spleen is not typically a target organ of toxicity for GalNAc-siRNA conjugates [25]. The injection site findings in rats were recapitulated in subsequent repeat-dose toxicity studies in rats.…”

“…Revusiran-related findings were present in liver, lymph nodes, kidney (rats only), and injection sites. Most of these findings (eg, lipid-filled hepatocellular vacuoles [rats only] and vacuolated and/or pigmented Kupffer cells in liver, vacuolated macrophages in lymph nodes, basophilic granules in renal proximal tubules, and vacuolated macrophages and inflammatory infiltrates at SC injection sites) are considered to be class effects associated with SC administration of siRNA-GalNAc conjugates to nonclinical species [25].…”

Silencing hepatic MCJ attenuates non-alcoholic fatty liver disease (NAFLD) by increasing mitochondrial fatty acid oxidation

“…1), silencing MCJ in hepatocytes is most likely the main mechanism for the siMCJ/Invivofectamine effect in vivo. Nevertheless, to further verify the beneficial therapeutic effect of silencing MCJ in hepatocytes, as an alternative to LNP, we examined the use of N-Acetylgalactosamine (GalNAc) as a delivery system for siRNA specifically to hepatocytes 17,28,29 . GalNAc is the preferred method of siRNA delivery for treatment of liver diseases that require extended periods of treatment and it has been recently approved by the FDA as a delivery system for siRNA in a liver rare disease.…”

2019 FDA TIDES (Peptides and Oligonucleotides) Harvest

“…Givosiran is the second small interfering RNA (siRNA) drug to be approved by FDA [13] (the first one was patisiran (Onpattro TM ), which was authorized in 2018 for the treatment of hereditary transthyretin-mediated amyloidosis and targets hepatic cells [14,15]). Additionally, givosiran is the first approved drug that demonstrates the enhanced stabilization chemistry (ESC)-GalNAc-siRNA conjugate technology.…”

“…The other three terminals (5′ of the sense strand, and 3′,5′ of the antisense strand) have thiophosphate linkages in the last two subunits for each side. This conjugation (ESC-GalNAc-siRNA) confers enhanced stability upon subcutaneous administration of the siRNA and offers a 10-fold increased potency of the drug over the standard template chemistry (STC) [13,17]. Givosiran is Golodirsen was developed for the treatment of Duchenne's muscular dystrophy (DMD), which is a progressive muscle deterioration that starts in early childhood and in most cases ends up crippling patients before adolescence.…”