Integrated Assessment of the Clinical Performance of GalNAc 3 -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.