Enhancing Gene And Cell Therapies With Circular RNA-Based Gene Expression

A conversation with Erik Digman Wiklund, Ph.D., CEO, Circio

Delivery of nucleic acid therapeutics varies depending on disease, therapeutic target, and genetic payload. Circio Holding ASA has developed a circular RNA gene expression platform in which the delivery mechanism is engineered to match the need for increased or prolonged expression in a specific target indication of interest. Approaches such as adeno-associated viruses (AAVs), nonviral vectors, lipid nanoparticles (LNPs), and peptide-based strategies are all viable delivery options, each offering advantages and limitations.

In this Q&A, Life Science Connect’s Izzy Dininny sits down with Circio’s Erik Wiklund to discuss the benefits of circular RNA platforms, the strengths of different delivery strategies, and the current bottlenecks in gene delivery.

Circio’s novel circular RNA-based gene expression platform, circVec, has demonstrated the ability to deliver substantial gains in RNA half-life and therapeutic protein expression from viral and nonviral vectors. By what mechanism does circular RNA increase half-life? How do the delivery requirements for a circular RNA expression vector differ from those of conventional mRNA therapeutics?

The difference is very simple: circular RNA (circRNA) has no free ends. Linear mRNA has a 5' cap and a 3' poly-A tail that cellular enzymes recognize and degrade, while circRNA is covalently closed into a loop. This structural difference translates into a substantially prolonged RNA half-life in vivo, which in turn can translate to fiftyfold enhanced protein expression compared to conventional mRNA-based vectors.

circRNA is a common class of noncoding RNA that is present in virtually all human cells, including all the required biological systems for circRNA biogenesis. This means that we can use established viral and DNA delivery vectors to encode the circRNA instructions, and the host cell takes care of the rest through natural processes.

What makes Circio’s circVec technology different from other circRNA approaches is that the circRNA is not being delivered directly. Rather, the circRNA is produced in vivo through the delivery of DNA that encodes the genetic recipe for circRNA biogenesis. The circRNA biogenesis happens via normal transcription and takes advantage of the canonical intracellular splicing machinery via a mechanism known as back-splicing.

The circVec platform is versatile and can be deployed for several therapeutic applications. In the context of AAV gene therapy, we have demonstrated that circVec can increase payload expression by up to fiftyfold. This advantage can enable substantial dose reduction, improve the toxicity profile, and make AAVs relevant in novel indications where current approaches are not potent enough.

For in vivo cell therapy, LNP-delivered nonviral circVec vectors have shown up to six months’ durability on a single dose in vivo. This extended window of expression could make in vivo CAR-T therapy feasible in oncology with an approach that is non-integrating and repeat-dosable, which would offer a major advantage and a novel therapeutic window compared to current lentiviral and RNA-based strategies.

The industry has invested heavily in lipid nanoparticle technologies. Are there tissues where existing delivery technologies lead to adequate expression, but the safety profile remains unacceptable for chronic or repeated administration?

LNPs have a clear and proven role in vaccination and have a strong tendency to accumulate in the liver upon systemic delivery, which has complicated development in non-liver diseases. The inflammatory responses driven by ionizable lipids and innate immune sensing of RNA cargo are desired for vaccination or where stimulating the immune system is part of the treatment, e.g., for oncology. However, this feature is a major constraint for gene and cell therapies and chronic diseases where durability is critical.

Significant efforts are going into developing targeted LNPs that have reduced immunogenicity and traffic to specific tissues and cell types. To date, this has been most successful for T cells and is an integral part of current RNA-based in vivo CAR-T programs in autoimmune disease. However, these programs are all early, and the first have just entered the clinic. It will be very interesting to follow as clinical data matures to demonstrate specificity, efficacy and safety in patients.

What have been the biggest challenges related to toxicity, cost, or biological barriers when attempting to extend delivery beyond more accessible tissues?

Three things stand out. First, biodistribution. Most delivery systems default to the liver, and re-engineering tropism for muscle, heart, CNS, or immune cells is genuinely hard.

Second, the dose-toxicity relationship in AAV gene therapy. We've seen tragic outcomes in trials of systemically delivered high-dose AAV, as the doses required to achieve therapeutic expression with conventional vectors leave little to no safety margin. Circio’s ASGCT 2026 data showed up to fortyfold greater expression in heart tissue and fiftyfold in the eye for circVec-based AAVs compared to standard approaches. If you can achieve the same therapeutic effect at a fraction of the dose, the therapeutic window for gene therapy gets much wider and the toxicity profile will be improved.

Third, cost. Gene and cell therapies are among the most expensive medicines, and the need for a high viral dose is a major driver of manufacturing cost. The prolonged half-life of circRNA can enable significantly increased gene expression and thus reduction of the required therapeutic dose – that’s not just a safety benefit but also a path to treatments that are more affordable and accessible to the patients who need them.

You have recently partnered with TraffikGene to explore nonviral delivery of circular RNA expression vectors. What delivery limitations have you encountered with existing viral and nonviral systems that peptide-based carriers may be able to address?

The standard way to deliver nucleic acid cargo today is by LNP. The collaboration between Circio and TraffikGene is about asking whether peptide amphiphile carriers can be a safer and more precise alternative for delivery of synthetic DNA vectors. Delivery of DNA leads to strong inflammatory responses, which must be overcome if nonviral synthetic DNA therapeutics are to be viable as future treatments.

The hypothesis we are exploring is whether the combination of targeted delivery by the TraffikGene peptides, combined with circVec-enhanced and prolonged expression, can act synergistically to generate safe, precise, and re-dosable DNA-format therapies for genetic diseases. In addition, peptides can potentially engage specific surface receptors and trigger active internalization in a different manner than targeted LNPs. As such, with this approach DNA vectors can potentially reach into tissues and cell types that can't efficiently be reached by currently available LNP technology.

If another company were developing a next-generation RNA platform today, what advice would you give them about avoiding delivery bottlenecks in development?

Don't treat delivery as a downstream problem – it is currently the main bottleneck and most important problem to solve. Unfortunately, several sophisticated nucleic acid and vector technologies have failed to translate into viable therapeutics because of a lack of viable therapeutic delivery systems. If this is not dealt with from the beginning, you risk spending significant time and capital trying to retrofit a delivery solution onto a payload it wasn't designed for.

Also, I would advise initiating collaborations broadly and early. No one company can solve all of the challenges required to create safe, efficient, and commercially viable gene and cell therapies. Build relationships with the best delivery groups from the start, because access to cutting-edge carriers will be a competitive differentiator for nucleic acid therapeutic platforms over the next decade. This is the main reason you are seeing Circio enter into so many early-stage R&D collaborations.

In parallel, look at what clinically validated delivery systems exist today, and design a lead program around that. This is why Circio is starting with AAVs. AAVs have been proved in the clinic and GMP manufacturing and regulatory pathways are established. For all its caveats, this clear line of sight reduces technology risk, cost, and timelines, which is critical for a viable biotech strategy based on finite resources. Simply put, in our experience, AAV delivery is the fastest and lowest-risk path to clinical proof of concept for the circVec technology platform.

Having said that, we are very excited about the prospect of nonviral, repeat-dosable DNA-format gene and cell therapies. However, the technology required for efficient and safe delivery remains unproved. We are convinced that these challenges can be resolved, but it remains unclear how long it will take and which vector and delivery systems will win out in the clinic and commercially.

About The Expert:

Erik Wiklund, CEO of Circio, has deep scientific knowledge in RNA biology and was the co-discoverer of human circular RNA. He has 15 years of pharma and biotech industry experience in a variety of functions including R&D, finance, and business development. He previously worked for the radiopharmaceutical company Algeta, which was acquired by Bayer in 2014, and as a consultant in the Pharma & Health Care practice of McKinsey & Company. Wiklund holds a Ph.D. in molecular biology from Aarhus University, Denmark, and the Garvan Institute of Medical Research, Sydney, Australia.