Antisense Oligonucleotide Therapies

Abstract

Many antisense oligonucleotides (ASOs) from several classes of molecules are currently in drug development. Despite over 20 years of pharmaceutical research, few ASOs have been marketed due to problems with clinical efficacy or preclinical toxicologic challenges. However, a number of recent developments have renewed interest in this class including the registration of mipomersen, the advent of successful screening strategies to eliminate more toxic molecules, and new understanding of the risks of off-target nucleotide binding and mitigation of potential off-target effects. Recent advances in backbone chemistries, conjugation to other moieties, and new delivery systems have allowed better tissue penetration, enhanced intracellular targeting, and less frequent dosing, resulting in fewer toxicities. While these new developments provide invigorated interest in these platforms, a few lingering challenges and preclinical/clinical toxicity issues remain to be completely resolved, including: (1) proinflammatory effects (vasculitis/inflammatory infiltrates); (2) nephrotoxicity and hepatotoxicity unrelated to lysosomal accumulation; and (3) thrombocytopenia. Recent investigative work by several laboratories have helped elucidate mechanisms for these issues, allowing a better understanding of the clinical relevance and implications of particular toxicities. It is important for toxicologists, pathologists, and regulatory reviewers to be familiar with new developments in the ASO field and their implications, as a greater number of new types of antisense molecules undergo preclinical toxicity testing.

Efficacy and Safety Profile of Tricyclo-DNA Antisense Oligonucleotides in Duchenne Muscular Dystrophy Mouse Model

“…In this regard, we carried out a detailed toxicity evaluation in mdx mice treated with 200 mg/kg/week of 13-mer tcDNA for 12 weeks. PS AONs are well-recognized for their immunostimulatory effects 30 by activating the alternative pathway of complement among others 31, 32. Subsequently, proinflammatory cytokines are released, resulting in enhancement of innate immune responses.…”

The Minipig is a Suitable Non-Rodent Model in the Safety Assessment of Single Stranded Oligonucleotides

“…After repeated dosing, they tend to accumulate in tissues, with the highest levels found in the kidney and liver, followed by lymphoid and other tissues, a characteristic observed across different mammalian species (Geary et al , 2015). SSO-mediated toxicities are categorized into Watson/Crick hybridization-dependent effects, caused by on-target effect (exaggerated pharmacology) or off-target (secondary) pharmacology, and potential non-hybridization related toxicities (Frazier, 2015). SSO accumulation-related effects, pro-inflammatory effects or protein binding of the SSO may be examples of those hybridization-independent toxicities.…”

“…In plasma, they may manifest as an acute and transient prolongation of coagulation and/or activation of the alternative complement system, particularly following intravenous administration in the non-human primate (NHP), upon reaching high plasma exposures (Crooke et al , 2016). In addition, renal tubular cell degeneration, glomerulonephritis, hepatic toxicity with increased serum aminotransferase activities, single cell necrosis of hepatocytes, as well as thrombocytopenia and injection site reactions (ISRs) after subcutaneous administration may be identified during preclinical and/or clinical investigations (Burdick et al , 2014; Engelhardt et al , 2015; Frazier, 2015; Henry et al , 1997; van Meer et al , 2016). These toxic effects may be hybridization-dependent or -independent and are generally sequence-specific and related to tissue exposures.…”

Androgen receptor in cancer-associated fibroblasts influences stemness in cancer cells

“…Although siRNA is widely used in transient assays to suppress gene expression in cell culture, the short half-life and instability of siRNA make this technique difficult to study for longer-term exposures in vitro. Also, siRNA molecules are double-stranded and require lipid mediated transfection agents to deliver them into cells, which can cause non-specific effects on cells growing in culture and are poorly suited for use as a therapeutic agent in vivo (Frazier 2015). To address these issues, we utilized ASO with 2′–4′-constrained ethyl (cEt)- modifications, which have demonstrated significant pharmacological activities in both preclinical and clinical studies without the need for complex lipid delivery modalities (Hong, et al 2015; Yamamoto, et al 2015).…”