The 13th Annual Meeting of the Oligonucleotide Therapeutics Society was held at the gorgeous 18th century Palais de la Bourse in Bordeaux, France and was immediately preceded by the “Aptamers in Bordeaux” meeting. The palace made a wonderful backdrop for presentations on the impressive progress that has been made in the field of oligonucleotide therapeutics over the last year.
As with the last few annual meetings, there was a Preconference Oligonucleotide Therapeutics Education Workshop entitled Designing Oligo Therapeutics and Understanding Their PK, sponsored by the Korea Institute of Toxicology. The Education Workshop was videotaped and is available for viewing on the OTS website. The main meeting got off to a great start with the keynote lecture “A Worms Tale: Oligonucleotide-Guided Gene Regulation and Secrets of Inheritance and Immortality” by Nobel Laureate Craig C. Mello, PhD of the RNA Therapeutics Institute at the University of Massachusetts Medical School. The keynote lecture and the awards session were also videotaped and are available for viewing on the website.

A particular highlight of the meeting was the session on delivery. Shalini Andersson from AstraZeneca (in collaboration with Ionis) introduced the concept of conjugating glucagon-like peptide-1 (GLP1) to antisense oligonucleotides for targeted delivery to pancreatic islet beta-cells. Compared to an un-conjugated MALAT1 ASO, a GLP1 conjugated MALAT1 ASO showed a 40-fold increase in potency in GLP1 receptor overexpressing HEK293 cells. In mice, both the MALAT1 and a FOXO1 GLP1-conjugated ASO down-regulated their target mRNAs in beta islet cells with no significant changes in hepatocytes. Targeting of GLP1-conjugated ASO was specific as there was no such down-regulation in GLP1 knockout mice.

Next up, Tom Kirchhausen from Harvard Medical School amazed the audience with a visually stunning talk about the use of lattice light-sheet microscopy to track and quantify the intracellular delivery of siRNA and ASOs. He kindly made a short movie of siRNA endosomal escape into the cytoplasm available to accompany this article. He is in the process of updating his website, so more of the movies will be available to the public soon.

The session continued with a talk from Vadim Dudkin from Janssen Pharmaceuticals (in collaboration with Alnylam) on designed fibronectin type III (FN3) domains, called centyrins, for extrahepatic delivery of siRNA. Centyrins are ~10 kDa protein scaffolds based on a consensus FN3 sequence from human tenascin which can be easily engineered to bind to cell-surface receptors with sub-nanomolar affinities.¹ Anti-EGFR centyrin-conjugated siRNAs resulted in specific mRNA downregulation with IC50 between 0.2 and 1 nM in EGFR+ tumour mouse xenografts and apparently centyrins targeting PSMA and BCMA are equally effective (data not shown).

Marco Passini from Sarepta Therapeutics concluded the session with his talk on cell-penetrating peptide-conjugated morpholino oligomers (PPMO) for the treatment of Duchenne Muscular Dystrophy. In the mdx mouse model a single IV injection of 120 mg/kg of PPMO resulted in ~150% wildtype dystrophin levels in quadriceps, ~40% in diaphragm and ~20% in heart 30 days later. This compared very favorably with <10% using the unconjugated PMO. In non-human primates, 4 weekly doses of 80 mg/kg resulted in up to 90% exon skipping in skeletal muscle and around 60% in cardiac muscle as well as smooth muscle. A phase I trial of an exon 51-PPMO is expected to start by the end of the year.

Another highpoint of the meeting was the session on immune effects and safety of nucleic acids, specifically the talk by Robert Coffman from Dynavax Technologies on CpG oligonucleotides. Although CpG oligonucleotides have long languished in limbo due to early trial failures, this subset of therapeutic oligonucleotides is finally entering the limelight. Dynavax Technologies presented striking data on CpG oligonucleotides for immunotherapy of cancer; when directly injected into tumours of metastatic melanoma patients treated with pembrolizumab, the two agents synergize to increase tumour infiltration of functional T cells.² Notably, seven of seven pembrolizumab naïve patients treated by this approach showed partial or complete tumor regression, with abscopal effects on non-injected lesions. Inhaled CpG oligonucleotides in combination with anti-PD-1 also completely cleared lung tumours and controlled metastases in multiple tissues in 60% of treated mice compared to ~15% with pembrolizumab only.

Continuing the theme of emerging fields, Moderna Therapeutics presented data on how they have overcome the limitations of mRNA therapeutics by optimizing mRNA chemistry and lipid nanoparticle delivery. The 1-methyl-pseudouridine and 5-methoxy uridine chemistries slow accelerated blood clearance mediated by IgM and B cell activation, thus enabling successful repeat administration. Their proprietary amino lipid formulations increased expression of an erythropoietin mRNA 6x after a single 1 mg/kg IV injection in rats and protein expression was not attenuated during chronic weekly dosing with 0.2 m g/kg in non-human primates. Administration of 0.2 mg/kg mRNA-3704 coding for functional methylmalonyl CoA mutase resulted in rescue of the phenotype in mouse models of methylmalonic acidemia, a fatal autosomal recessive metabolic disorder. A second talk focused on the influence of mRNA sequence and changes in secondary structure resulting from modified chemistry on the expression of the encoded protein. An unstructured ribosomal landing pad around the start codon combined with a highly structured coding sequence appear to aid high expression levels.

Equally impressive is the progress made in advancing CRISPR/Cas9 into the clinic. Amy Rhoden Smith from Intellia Therapeutics showed that lipid nanoparticle delivery of 3 mg/kg CRISPR/Cas9 mRNA and transthyretin (TTR)-targeted sgRNA mediated gene editing of up to 70%. This effect persisted for 12 months after a single injection in CD-1 mice and caused a near total reduction in serum TTR levels during the whole time suggesting that liver progenitor cells were successfully gene edited. Guide sequence selection, guide RNA chemical modification and mRNA optimization were critical in achieving high potency.

Naturally, the awards presentations and talk were not to be missed with great talks by all the winners. These have been taped and will be available on the website.

Richard Finkel, the winner of the paper of the year award, additionally gave a talk as part of the clinical session on the final trial outcomes from nusinersen (Spinraza) for the treatment of spinal muscular atrophy. He also included an update on the ongoing NURTURE trial in pre-symptomatic newborns which showed normal development for all type 2 children in the study (SMN2 copy number =3) and about ½ of type 1 (SMN=2), with the remainder also achieving motor milestones and continuing to improve, albeit at a slower rate. Truly impressive results that herald what is to come in the next few years.

Presentations on clinical data from Ionis and Alnylam finished off the meeting. Ionis highlighted volanesorsen, an ApoC-III antisense oligonucleotide for severe hypertriglyceridemia and familial chylomicronemia syndrome that is awaiting FDA approval and inotersen for hereditary TTR amyloidosis with phase III trial completed and detailed results expected in November. Alnylam emphasized patisiran, a lipid nanoparticle formulated siRNA also for hereditary TTR amyloidosis with a successfully completed phase III trial and details to be presented in November, and givosiran, a GalNAc-conjugated siRNA for the treatment of acute hepatic porphyrias.

Together with the expected approval of the CpG oligonucleotide adjuvanted hepatitis B vaccine Heplisav-B from Dynavax, this should make for an interesting two weeks at the start of November. However, the ample clinical (19 phase III trials, 69 phase II, 73 phase I) and pre-clinical pipelines – and not just of the companies mentioned here – promise an exciting annual meeting of the Society in 2018. Please reserve September 30 – October 3 in your calendar. We hope to see you there!

1. Engineering a targeted delivery platform using Centyrins.
   Goldberg SD, Cardoso RM, Lin T, Spinka-Doms T, Klein D, Jacobs SA, Dudkin V, Gilliland G, O’Neil KT.
   Protein Eng Des Sel. 2016 Dec;29(12):563-572.
2. Intratumoral injection of a CpG oligonucleotide reverts resistance to PD-1 blockade by expanding multifunctional CD8+ T cells.
   Wang S, Campos J, Gallotta M, Gong M, Crain C, Naik E, Coffman RL, Guiducci C.
   Proc Natl Acad Sci U S A. 2016 Nov 15;113(46):E7240-E7249.