-MALAT1-ASO. (A) Schematic structure of the Cy3-labeled eGLP1-MALAT1-ASO conjugate. (B) Fluorescence imaging of (a) wild-type and (b and c) GLP1R-HEK293 cells treated with 100 nM BODIPY–labeled (green) eGLP1 peptide for 15 min (b) or 60 min (a and c) at 37°C. (C) Fluorescence imaging of (a) wild-type and (b and c) GLP1R-HEK293 cells treated with 33 nM Cy3–labeled (red) eGLP1-MALAT1-ASO for 15 min at 0°C (b) or for 60 min at 37°C (a and c). Cells were stained, fixed, and imaged on an ImageXpress fluorescence microscope. Nuclei were stained with Hoechst 32585 (blue). Scale bars, 10 μm.

Antisense oligonucleotides (ASOs) hold incredible potential to be used as effective therapies for a wide range of diseases. One challenge in moving them from bench to bedside has been their limited ability to be taken up by target cells. A collaboration by AstraZeneca and Ionis Pharmaceuticals has made a huge advance in this area by exploiting a receptor and providing a new approach to delivering ASOs into pancreatic β-cells—cells that are notoriously recalcitrant to ASO uptake. The work is published in Science Advances in a paper titled, “Targeted delivery of antisense oligonucleotides to pancreatic β-cells.”

ASOs are short (14–20 nucleotides), synthetic, single-stranded oligodeoxynucleotides that can alter RNA and modify protein expression. Recent advances have been made to improve their potency, efficacy, stability, and pharmacokinetic properties. In this study, researchers have exploited a receptor to design a new approach to deliver ASOs to pancreatic β-cells. They combined ribonuclease H1- dependent ASOs with an engineered glucagon-like peptide-1 receptor (eGLP1R)—a receptor known for its internalization—to productively deliver ASO cargo to pancreatic β-cells both in vitro and in vivo.

GLP1R-dependent uptake of ASO and knockdown of gene expression in mice treated with eGLP1-ASO conjugates in vivo. (A) Representative pancreatic sections stained for ASO by IHC and MALAT1 RNA by ISH from mice treated for 2 weeks with three subcutaneous injections of (a) saline, (b) MALAT1-ASO (1 µmol/kg), or (c) eGLP1-MALAT1-ASO (1 µmol/kg). (B) ASO uptake by IHC and MALAT1 RNA levels by ISH in pancreatic sections from mice treated for 2 weeks with three intravenous injections of (a) saline or (b) eGLP1-MALAT1-ASO (1 µmol/kg). (C) MALAT1 gene expression by ISH in (a) wild-type (WT) and (b) GLP1R knockout (KO) mice 72 hours after a single subcutaneous dose of saline or eGLP1-MALAT1-ASO (1 µmol/kg). (D) Pancreatic section from wild-type mice stained using fluorescence in situ probes for MALAT1 (purple, arrows), insulin (green), and glucagon (red). Pancreatic sections were collected 72 hours after one subcutaneous administration of (a) saline or (b) MALAT1-ASO and (c) eGLP1-control-ASO or (d) eGLP1-MALAT1-ASO, and all compounds were dosed at 1 µmol/kg. Scale bars, 200 µm. Islets are circled in blue in (A) to (C). Credit: Ämmälä et al., Sci. Adv. 2018; 4 : eaat3386

The team used quantitative real-time polymerase chain reaction that targeted metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), a noncoding RNA transcript expressed in many tissues, to determine that eGLP1-MALAT1-ASO conjugation enhanced the uptake of ASOs in vitro in human islets compared to MALAT1-ASO.

The ability of eGLP1-conjugated ASOs to target insulin-secreting β-cells within the pancreas was investigated in mice treated twice a week with skin injections of saline, MALAT1-ASO, or eGLP1-MALAT1-ASO and intravenous injections of MALAT1-ASO or eGLP1-MALAT1-ASO. Mice treated with eGLP1-MALAT1-ASO experienced ASO uptake and reduced MALAT1 gene expression in the pancreatic islets. The researchers also targeted the forkhead box protein O1 (FOXO1) transcript and found that eGLP1-FOXO1-ASO increased productive uptake in isolated mouse islets. Additionally, the doses used did not affect target gene expression in liver or other tissues, indicating enhanced tissue and cell type specificity.

First discovered over two decades ago, ASOs have developed as extremely promising therapies. ASOs are particularly exciting because of their ability to target genes coding for proteins linked to human diseases that are considered undruggable by more traditional methods such as small molecules. Indeed, two ASO-mediated therapies have received approval from the FDA for the treatment of two diseases that had extremely limited options in their therapeutic arsenal; Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA). The researchers who developed the SMA therapy were announced as recipients of the 2019 Breakthrough Prize in Life Sciences earlier this week.

The authors write that “the findings presented in this paper have the potential to broaden the use of ASO technology, opening up novel therapeutic opportunities, and presents an innovative approach for targeted delivery of ASOs to additional cell types.” With the rapid development of improved delivery methods of ASOs, this technology may have a dramatic effect on the treatment of many conditions in the near future.

NewsAdenocarcinomaAntisense oligonucleotidesDuchenne muscular dystrophyMiceSmall moleculesSpinal muscular atrophyAstraZenecaeGLP1-MALAT1-ASO
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