Safety and Tolerability of GalNAc3-Conjugated Antisense Drugs Compared to the Same-Sequence 2'-O-Methoxyethyl-Modified Antisense Drugs: Results from an Integrated Assessment of Phase 1 Clinical Trial Data.

The triantennary N-acetylgalactosamine (GalNAc3) cluster has demonstrated the utility of receptor-mediated uptake of ligand-conjugated antisense drugs targeting RNA expressed by hepatocytes. GalNAc3-conjugated 2'-O-methoxyethyl (2'MOE) modified antisense oligonucleotides (ASOs) have demonstrated a higher potency than the unconjugated form to support lower doses for an equivalent pharmacological effect. We utilized the Ionis integrated safety database to compare four GalNAc3-conjugated and four same-sequence unconjugated 2'MOE ASOs. This assessment evaluated data from eight randomized placebo-controlled dose-ranging phase 1 studies involving 195 healthy volunteers (79 GalNAc3 ASO, 24 placebo; 71 ASO, 21 placebo). No safety signals were identified by the incidence of abnormal threshold values in clinical laboratory tests for either ASO group. However, there was a significant increase in mean alanine transaminase levels compared with placebo in the upper dose range of the unconjugated 2'MOE ASO group. The mean percentage of subcutaneous injections leading to local cutaneous reaction was 30-fold lower in the GalNAc3-conjugated ASO group compared with the unconjugated ASO group (0.9% vs. 28.6%), with no incidence of flu-like reactions (0.0% vs. 0.7%). Three subjects (4.2%) in the unconjugated ASO group discontinued dosing. An improvement in the overall safety and tolerability profile of GalNAc3-conjugated 2'MOE ASOs is evident in this comparison of short-term clinical data in healthy volunteers.

Integrated Assessment of Phase 2 Data on GalNAc3-Conjugated 2'-O-Methoxyethyl-Modified Antisense Oligonucleotides.

Receptor-mediated delivery of an antisense oligonucleotide (ASO) using the ligand-conjugated antisense technology is establishing a new benchmark for antisense therapeutics. The triantennary N-acetylgalactosamine (GalNAc3) cluster is the first conjugated ligand to yield a marked increase in ASO potency for RNA targets expressed by hepatocytes, compared to the unconjugated form. In this study, we present an integrated safety assessment of data available from randomized, placebo-controlled, phase 2 studies for six GalNAc3-conjugated 2'-O-methoxyethyl (2'MOE)-modified ASOs. The total study population included 642 participants (130 placebo; 512 ASO) with up to 1 year of exposure. The primary measures were the incidence of signals from standardized laboratory tests and the mean test results over time. The GalNAc3-conjugated ASOs were well tolerated with no class effect identified across all doses tested compared to placebo. These results extend prior observations from phase 1 studies, now with treatment up to 1 year.

Integrated Assessment of the Clinical Performance of GalNAc3-Conjugated 2'-O-Methoxyethyl Chimeric Antisense Oligonucleotides: I. Human Volunteer Experience.

Advances in medicinal chemistry have produced new chemical classes of antisense oligonucleotides (ASOs) with enhanced therapeutic properties. Conjugation of the triantennary N-acetylgalactosamine (GalNAc3) moiety to the extensively characterized phosphorothioate (PS)-modified 2'-O-methoxyethyl (2'MOE) ASO exemplifies such an advance. This structure-activity optimized moiety effects receptor-mediated uptake of the ASO prodrug through the asialoglycoprotein receptor 1 to support selective targeting of RNAs expressed by hepatocytes. In this study we report the integrated assessment of data available from randomized placebo-controlled dose-ranging studies of this chemical class of ASOs administered systemically to healthy human volunteers. First, we compare the pharmacokinetic and pharmacodynamic profiles of a subset of the GalNAc3-conjugated PS-modified 2'MOE ASOs to the parent PS-modified 2'MOE ASOs for which plasma analytes are available. We then evaluate the safety profile of the full set of GalNAc3-conjugated PS-modified 2'MOE ASO conjugates by the incidence of signals in standardized laboratory tests and by the mean laboratory test results as a function of dose level over time. With hepatocyte targeted delivery, the ED50 for the GalNAc3-conjugated PS-modified 2'MOE ASO subset ranges from 4 to 10 mg/week, up to 30-fold more potent than the parent PS-modified 2'MOE ASO. No GalNAc3-conjugated PS-modified 2'MOE ASO class effects were identified from the assessment of the integrated laboratory test data across all doses tested with either single or multidose regimens. The increase in potency supports an increase in the safety margin for this new chemical class of ASOs now under broad investigation in the clinic. Although the total exposure is limited in the initial phase 1 trials, ongoing and future investigations in patient populations will support evaluation of the effects of long-term exposure.

Integrated Safety Assessment of 2'-O-Methoxyethyl Chimeric Antisense Oligonucleotides in NonHuman Primates and Healthy Human Volunteers.

The common chemical and biological properties of antisense oligonucleotides provide the opportunity to identify and characterize chemical class effects across species. The chemical class that has proven to be the most versatile and best characterized is the 2'-O-methoxyethyl chimeric antisense oligonucleotides. In this report we present an integrated safety assessment of data obtained from controlled dose-ranging studies in nonhuman primates (macaques) and healthy human volunteers for 12 unique 2'-O-methoxyethyl chimeric antisense oligonucleotides. Safety was assessed by the incidence of safety signals in standardized laboratory tests for kidney and liver function, hematology, and complement activation; as well as by the mean test results as a function of dose level over time. At high doses a number of toxicities were observed in nonhuman primates. However, no class safety effects were identified in healthy human volunteers from this integrated data analysis. Effects on complement in nonhuman primates were not observed in humans. Nonhuman primates predicted safe doses in humans, but over predicted risk of complement activation and effects on platelets. Although limited to a single chemical class, comparisons from this analysis are considered valid and accurate based on the carefully controlled setting for the specified study populations and within the total exposures studied.