Oligonucleotide therapies: the precision medicines that act on RNA, not proteins

Short, engineered strands of DNA or RNA, called oligonucleotides and distinct from mRNA vaccines, are redrawing the map of treatable disease by acting upstream of the proteins that pills and biologics have spent forty years trying to bind.

Most drugs in the modern pharmacopoeia, from statins to monoclonal antibodies, work by binding a protein that is already made, then changing what it does. Oligonucleotides do something more basic: they steer the cell's own RNA before it gets translated, either silencing a gene, fixing a splicing error, or dialing a transcript up or down. Two flavors dominate the clinic today. Antisense oligonucleotides, or ASOs, are short single strands that bind a complementary RNA and recruit the cell to destroy it or change how it is read. Small interfering RNAs, or siRNAs, work in pairs inside a protein complex called RISC and do similar work, often with longer-lasting effects. Both can be chemically modified to survive in the body long enough to be dosed every three to twelve months, closer to a vaccine schedule than to a daily pill.

A concrete marker of where that class sits today arrived on April 28, 2026, when the California Institute for Regenerative Medicine (CIRM) awarded AcuraStem $7.5 million in grant funding to advance its lead ASO candidate, AS-241, toward a first-in-human trial in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) (PR Newswire release; AcuraStem announcement).

AS-241 is built around a specific molecular accident. In roughly 97% of ALS patients, regardless of the underlying genetic cause, a protein called TDP-43 falls out of its normal place in the cell nucleus. That loss makes the cell mis-splice a gene called UNC13A, producing a broken version of a protein that nerve cells need to communicate at the synapse (Genetic Engineering & Biotechnology News overview). AS-241 is an ASO designed to mask the problematic stretch of UNC13A so the cell produces a working protein again. It is the kind of target that, ten years ago, would have been called undruggable, because no small molecule or antibody could touch the splicing defect itself. CIRM's award pages list both an earlier discovery project and a later, IND-enabling round for the same UNC13A-targeting program (earlier award; late-stage award).

That single program is one thread in a much larger shift. The GEN feature frames oligonucleotides as a precision-medicine class whose targets are chosen upstream, at the RNA layer, and whose dosing schedules can stretch to once or twice a year once a patient is stable (GEN feature). Human genetics has been pointing designers at new RNA-level targets for over a decade; AI and multiomics are now turning those targets into candidate sequences faster, which is one reason the pipeline of ASO and siRNA programs has widened into rare disease, metabolic disease, fibrosis, and neurodegeneration.

The honest scope is narrower than the headlines. Maintenance dosing measured in months is not a cure. Some of the chemistry that makes an oligonucleotide survive the body also has to be dosed carefully to avoid kidney and liver stress. Delivery into the right tissue, especially the brain, remains hard, which is one reason so many CNS programs still arrive by lumbar puncture. The cost of approved oligo drugs has run into the hundreds of thousands of dollars per patient per year, and most of the targets now being called "undruggable" sit at preclinical or early-clinical stages rather than at the FDA's door (ALS News Today coverage).

AcuraStem has also signaled that it is building a clinical-stage footprint beyond California. On April 16, 2026, the company incorporated a European subsidiary, AcuraStem P2 Ltd, in Nicosia, Cyprus, a base from which it plans to run European trial sites ahead of the first-in-human study (AcuraStem media page).

AS-241 has IND-enabling work to clear before its first human dose. The 2026–2028 readout window for ASO and siRNA programs in ALS, FTD, and a handful of other formerly untreatable diseases will determine whether the class's broader claim is being carried by durable data, or by language that has run ahead of it.