Expanding Delivery, Longer Durability, and Programmable RNA Modalities Reshaping Medicine

Since the first oligonucleotide therapy was approved in 1998, the pace of approvals has accelerated markedly, especially over the past decade. These medicines, once primarily associated with rare genetic diseases, conditions where the underlying biology was well understood but difficult to address with conventional modalities, are coming into their own as broadly applicable therapeutics. 

After establishing their value in diseases such as spinal muscular atrophy, transthyretin amyloidosis, acute hepatic porphyria, Duchenne muscular dystrophy, and SOD1-associated amyotrophic lateral sclerosis, oligonucleotide medicines are moving into far larger patient populations. As advances in molecular design and delivery are expanding the modality beyond its early mechanisms and tissue targets, programs are now targeting major cardiovascular risk factors, including elevated LDL cholesterol, lipoprotein(a), and severe hypertriglyceridemia, as well as retinal diseases such as geographic atrophy. 

This shift is raising a new question for the field: As the biological ambition of oligonucleotide medicines grows, can the development infrastructure around them—spanning delivery, durability, analytical characterization, and scalable manufacturing—advance quickly enough to turn that ambition into medicines that can reach patients reliably?

Expanding delivery: Moving oligonucleotides beyond the liver

Delivery has long defined the boundaries of oligonucleotide drug development. The modality can, in principle, address a wide range of disease-causing RNA targets, but only when sufficient drug amounts reach the right cells and escape intracellular compartments in an active form. In practice, advances in delivery have often determined which biological opportunities could become viable medicines.

The liver provides a clear example. Conjugating an oligonucleotide to N-acetylgalactosamine, or GalNAc, enables it to bind the Asialoglycoprotein receptor (ASGPR), which is highly expressed on hepatocytes, and enter the cells through receptor-mediated endocytosis. This approach has made subcutaneous delivery to hepatocytes efficient, reproducible and clinically validated, supporting multiple approved siRNA medicines and helping establish the liver as the modality’s most tractable systemic target.

The next challenge is to achieve comparable precision outside the liver. Many important targets are in skeletal and cardiac muscle, the central nervous system, the lungs, immune cells, adipose tissue and tumors—tissues that lack an immediately equivalent delivery pathway. Progress in these areas is therefore unlikely to come from a single universal platform. Instead, developers are tailoring conjugates, antibodies, peptides and nanoparticles to the biology of individual tissues and cell types.

Muscle is among the most advanced examples. Antibody–oligonucleotide conjugates (AOCs) use antibodies or antibody fragments to engage receptors involved in tissue uptake, carrying an siRNA or antisense payload into skeletal and, potentially, cardiac muscle. Programs targeting transferrin receptor 1 have entered clinical development and have demonstrated that receptor-mediated delivery can produce pharmacological activity in muscle, although the field is still working to establish the durability, safety and clinical benefit of these platforms across diseases.

Central nervous system delivery is following several paths. Existing oligonucleotide therapies can reach the brain and spinal cord through intrathecal administration, but systemic delivery across the blood–brain barrier remains considerably harder. Lipid and other hydrophobic conjugates can alter distribution and cellular uptake, while antibody-, peptide- and receptor-based transport systems are being engineered to exploit pathways such as transferrin receptor-mediated transcytosis. These approaches have produced encouraging preclinical results, including broader distribution of oligonucleotide payloads in the central nervous system, but most have not yet reached the level of clinical validation achieved by GalNAc in hepatocytes.

Lipid nanoparticles add a complementary strategy. First-generation intravenously administered LNPs tend to accumulate in the liver, a property that enabled the approval of the siRNA therapy patisiran but limits their use in many extrahepatic settings. Researchers are now modifying lipid composition, particle chemistry and surface ligands to redirect functional delivery toward tissues such as the lung, spleen, immune system and tumors. Some targeted LNPs are designed to engage cell-surface receptors, while others alter the particle’s interactions with serum proteins and biological membranes to change its organ distribution.

The goal is not simply to increase the amount of nanoparticle that accumulates in a tissue. Accumulation does not necessarily mean that the nucleic acid has entered the intended cell, escaped the endosome and reached its intracellular target. The more meaningful measure is functional delivery: whether an adequate proportion of the administered dose produces the intended biological effect in the relevant cells without creating unacceptable exposure elsewhere. Targeted LNPs may eventually improve that efficiency and reduce the dose required, but much of the evidence outside the liver remains preclinical.

Together, these technologies are beginning to expand the therapeutic reach of oligonucleotides into neuromuscular, neurological, pulmonary, immunological and oncological diseases. But the transition beyond the liver is not one breakthrough replicated across tissues. It is a series of tissue-specific delivery problems, each requiring its own combination of molecular design, targeting biology, formulation and manufacturing.

“GalNAc showed the industry what becomes possible when oligonucleotide design is matched with a reliable, tissue-specific delivery pathway. The next phase will be more complex,” said Yu Lu, Senior Vice President, WuXi TIDES, part of WuXi AppTec.“ Moving beyond the liver will not depend on one universal solution, but on solving the distinct biological and delivery challenges of each tissue. The companies that can connect targeting biology, molecular design, analytics and scalable manufacturing will be best positioned to turn extrahepatic delivery from promising science into effective therapeutics.”

Increasing durability: Designing longer-lasting oligonucleotide medicines

Durability is becoming a deliberate design objective in oligonucleotide drug development, rather than simply a favorable pharmacokinetic outcome. Backbone and sugar modifications—including phosphorothioate linkages, 2′-O-methyl and 2′-O-methoxyethyl substitutions, and conformationally constrained nucleotides—can increase resistance to nuclease degradation, strengthen binding to the target RNA and shape tissue exposure. Their effects are not interchangeable, however: each modification must be selected in the context of the oligonucleotide’s mechanism, sequence, delivery route and safety profile.

The clinical impact is already visible. Vutrisiran, an approved GalNAc-conjugated siRNA targeting transthyretin, is administered once every 3 months, while inclisiran uses a maintenance schedule of two doses per year after its initial loading regimen. In cardiovascular development, investigational siRNAs targeting lipoprotein(a) have demonstrated target suppression lasting one year or longer after dosing. A Phase 2 study of lepodisiran, for example, reported substantial lipoprotein(a) lowering, with some patients sustaining reductions for nearly 1.5 years.

These dosing intervals are more than a convenience. In chronic diseases, where patients may otherwise need to take oral medicines every day or receive frequent injections, quarterly or semiannual treatment could reduce the number of opportunities for doses to be missed and shift more treatment delivery into the healthcare setting. But durable biomarker suppression should not automatically be equated with durable clinical benefit. Cardiovascular outcome trials are still needed to determine whether long-lasting reductions in targets such as lipoprotein(a) translate into fewer heart attacks, strokes or deaths.

The same persistence that makes these medicines attractive also raises the development bar. When pharmacological effects last for months, developers need a detailed understanding of tissue distribution, intracellular persistence, metabolite formation, duration of target engagement, off-target activity and the time required for an effect to reverse after treatment stops. Plasma pharmacokinetics alone may provide an incomplete picture because an oligonucleotide can clear rapidly from circulation while remaining active within tissues.

As dosing moves from weeks toward months, durability is becoming both one of the modality’s most valuable attributes and one of its most demanding development challenges. Small changes in monomer quality, conjugation chemistry, impurity profiles or stereochemical composition can influence the identity and performance of the final product. This requires analytical methods capable of resolving closely related sequence variants, truncated or extended products, conjugation-related impurities and degradation products, together with scalable processes that preserve product quality as demand grows. Longer-lasting oligonucleotide medicines therefore depend on the coordinated design of sequence, chemistry, delivery, pharmacology, analytics and manufacturing. 

Toward more precise and multifunctional oligonucleotide modalities

As developers learn to make oligonucleotide medicines last longer, they are also expanding what those medicines can be designed to do. For most of the field’s history, clinical success has come primarily from two mechanisms: reducing the abundance of a disease-related RNA through antisense or RNA interference and altering pre-mRNA splicing. A newer generation of technologies is beginning to move beyond this one-target, predominantly inhibitory model by combining targets, activating gene expression and modulating regulatory RNA networks.

Dual-targeting approaches are one example. Rather than administering two entirely separate molecules, researchers are designing oligonucleotide constructs or treatment combinations capable of suppressing two genes involved in the same disease. The rationale is particularly compelling in complex disorders driven by several interacting pathways, where changing a single target may produce an incomplete response. Preclinical studies have shown that engineered siRNA scaffolds can silence two genes simultaneously, including disease-relevant target pairs in neurological models.

Cardiovascular disease illustrates the potential of this approach. A dual-targeting construct could address two independent risk factors with one treatment for example, LDL cholesterol and triglycerides. That could simplify combination therapy and produce complementary biological effects. But the scientific challenge is greater than fitting two sequences into one molecule: developers must establish that each component retains sufficient potency, reaches the relevant cells, has an appropriate duration of action and does not create unanticipated interactions in efficacy or safety.

Small activating RNAs, or saRNAs, extend the modality in a different direction. Instead of degrading RNA or preventing its translation, these short double-stranded oligonucleotides are designed to increase transcription of a selected gene. The precise mechanism is still being characterized and may depend on the target and cellular context, but it is generally understood to involve sequence-specific interactions near a gene’s regulatory region and recruitment of transcriptional machinery. This creates a potential strategy for diseases in which restoring the expression of a protective, regulatory or insufficiently expressed protein could be beneficial.

AntimiRs offer a third way to reshape gene regulation. MicroRNAs normally bind multiple messenger RNAs and reduce their stability or translation, allowing a single microRNA to influence an interconnected network of genes. An antimiR is designed to bind and inhibit a selected microRNA, thereby releasing some of its downstream transcripts from repression. In diseases where a microRNA is pathologically overactive, this could help rebalance a broader gene-expression program rather than changing only one messenger RNA.

Together, dual-targeting oligonucleotides, saRNAs, and antimiRs point toward a broader future for oligonucleotide medicines. The modality is evolving from a set of tools used mainly to silence individual genes into a more diverse platform capable of coordinating multiple targets, increasing selected gene expression and modulating regulatory networks.

That expansion also raises the development bar. Each mechanism requires its own evidence that the molecule reaches the intended cells, produces the expected direction and magnitude of gene regulation, and translates molecular activity into a meaningful functional outcome. The promise is greater biological control; the corresponding requirement is a more integrated understanding of biology, chemistry, delivery, pharmacology, and long-term safety.

Development infrastructure is becoming part of the innovation process

The future of oligonucleotide medicines will not be determined by sequence design alone. As the field moves beyond established antisense and siRNA mechanisms, expands delivery outside hepatocytes, and pursues longer lasting and multifunctional constructs, development is becoming a multidimensional engineering challenge.

An extrahepatic program must align sequence and chemical modification with its targeting ligand or formulation, route of administration, tissue-distribution profile and bioanalytical strategy. A long-acting molecule requires an understanding not only of plasma pharmacokinetics, but also of tissue exposure, intracellular persistence, metabolite formation, duration of pharmacological activity and reversibility. Newer mechanisms such as saRNA add another layer: developers must show that the molecule reaches the relevant cells and produces the intended increase in gene expression, and that this molecular effect leads to a meaningful biological or clinical outcome.

These questions cannot be answered independently. A decision made in one part of the program can reshape almost every other part. The delivery technology influences tissue and cell exposure, route and frequency of administration, safety margins, formulation requirements and manufacturing complexity. The pattern of backbone and sugar modifications can affect potency, nuclease stability, protein binding, tissue retention, innate immune activation and the types of impurities that must be controlled. Conjugating an oligonucleotide to a ligand, peptide, antibody or lipid can improve targeting, but it also creates new questions around construct characterization, linker stability, product heterogeneity and process scalability.

Development infrastructure is therefore becoming part of the innovation itself. Progress increasingly depends on connecting several capabilities within one coordinated strategy:

• Oligonucleotide design, chemistry and conjugation, to optimize potency, stability, delivery and duration while considering safety and manufacturability from the outset.
• Formulation and drug-product development, including nanoparticle engineering where appropriate, to protect the payload, control administration and enable functional delivery to the intended cells.
• DMPK, bioanalysis and biomarker development, to characterize exposure in relevant tissues, quantify parent molecules and metabolites, and connect molecular target engagement with downstream pharmacology.
• Analytical development and impurity characterization, to establish identity, purity, sequence integrity, conjugate quality, degradation pathways and appropriate control strategies for both drug substance and drug product.
• Process development and scalable manufacturing, to translate increasingly complex chemistries and conjugates into reproducible processes that can support clinical development and, ultimately, commercial demand.

“The next chapter of oligonucleotide therapeutics will not be defined by one chemistry, one delivery technology or one mechanism of action. It will be shaped by how effectively the industry connects sequence design with delivery, pharmacology, analytics, safety and manufacturing. As these medicines become more durable, more tissue-selective and more functionally diverse, development infrastructure is no longer simply supporting innovation—it is helping determine which innovations can become viable medicines,” Yu Lu concluded.

The trends that may reshape oligonucleotide drug discovery in the coming decade

Will new delivery technologies move oligonucleotides decisively beyond the liver?

Liver-directed delivery established the first broadly reproducible foundation for systemically administered oligonucleotide medicines. GalNAc conjugation, in particular, demonstrated how a well-matched receptor pathway can make tissue-selective delivery clinically practical.

The next challenge is to achieve comparable functional delivery in skeletal and cardiac muscle, the central nervous system, the lung, immune cells, adipose tissue, and tumors. Antibody–oligonucleotide conjugates, peptides, lipid conjugates, and targeted nanoparticles are beginning to expand access to these tissues, but their maturity varies considerably. The central question is whether they can deliver sufficient drug into the right cells, support intracellular release and activity, and do so with consistent safety across very different biological environments.

Can durability become a defining therapeutic feature?

Durability is already becoming an important product attribute. Chemical modifications, tissue-targeting conjugates, and optimized molecular designs can sustain pharmacological activity for months after dosing. Approved and investigational programs are evaluating quarterly and semiannual regimens, while some candidates have shown biological effects that persist for a year or longer.

In chronic diseases, extended dosing intervals may reduce the burden of frequent treatment and limit the number of opportunities for missed doses. But long-lasting target suppression must still translate into meaningful clinical benefit. Developers also need to understand tissue persistence, metabolite formation, reversibility, cumulative exposure, and long-term safety, particularly when pharmacological activity continues well after circulating drug levels decline.

How far will programmable RNA modalities expand what oligonucleotides can do?

Oligonucleotide medicines are moving beyond conventional single-target gene silencing. Dual-targeting constructs aim to regulate two genes or pathways with one therapeutic strategy. Small activating RNAs are designed to increase expression of selected genes, while antimiRs inhibit regulatory microRNAs and can influence broader gene-expression networks.

These approaches could expand the modality into diseases where restoring gene expression or coordinating multiple pathways is more useful than suppressing a single target. However, most remain less clinically mature than established antisense and siRNA platforms. Their development will require clear evidence of functional gene regulation, careful control of sequence-dependent and network-level off-target effects, and a deeper understanding of delivery, immune activation, dose response, and reversibility.

Is development infrastructure becoming a scientific differentiator?

Yes. As oligonucleotide programs become more tissue-selective, durable, and mechanistically diverse, scientific and development decisions are becoming increasingly interdependent.

Sequence and chemical modifications influence potency, stability, immune recognition, tissue retention, impurity profiles, and analytical requirements. Delivery technologies affect biodistribution, dose, safety margin, formulation, and manufacturing complexity. Longer-lasting pharmacology changes the requirements for DMPK, safety assessment, biomarker strategy, and dose reversibility.

The ability to connect biology, chemistry, conjugation, formulation, bioanalysis, pharmacology, safety, analytical development, and manufacturing within one coordinated development strategy may increasingly determine whether a promising molecular concept can become a viable medicine.

What could define the next era of oligonucleotide drug discovery?

The next era will likely be defined by progress across three connected dimensions: where oligonucleotides can go, how long they can act, and what biological functions they can perform.

The decisive test, however, will be translation. The field must turn increasingly sophisticated molecular designs into medicines that can be characterized precisely, delivered to the intended cells, manufactured reproducibly, scaled efficiently, and used safely in patients.

Oligonucleotide therapeutics are entering a period of greater biological and technological ambition. They can already silence genes, alter RNA splicing, and reduce the production of disease-associated proteins; emerging approaches may add gene activation and coordinated pathway regulation to that repertoire.

That breadth is what makes the field so promising, but it also makes execution more demanding. As delivery expands, durability improves, and new RNA mechanisms mature, the next phase of innovation will depend not only on what oligonucleotides can be designed to do, but on whether the surrounding development infrastructure can translate programmable biology into reliable, scalable medicines for patients.