Circular RNA Therapeutics for Sustained Production of Therapeutic Proteins Without Repeated Dosing

Abstract

Circular RNA (circRNA) therapeutics have emerged as a promising platform for the sustained production of therapeutic proteins, offering a novel solution to the limitations of conventional protein replacement therapies that require frequent dosing. This review examines the scientific foundation, clinical potential, and translational progress of circRNA-based treatments, focusing on their capacity to enable prolonged protein expression in vivo. Emphasis is placed on mechanism-based advantages, recent advances in synthesis and delivery technologies, and practical considerations for clinical translation, making it relevant for clinicians and researchers interested in innovative biotherapeutics.

Introduction

The advent of RNA-based therapeutics has revolutionized multiple aspects of modern medicine, spanning from vaccines to gene modulation technologies. Among these, circular RNA (circRNA) therapeutics represent a paradigm shift, particularly for applications requiring sustained protein production without frequent administration. Unlike linear mRNA, circRNAs form covalently closed loops conferring remarkable stability against exonucleases, which translates into extended half-life and prolonged translational competency. This review evaluates the scientific rationale, clinical evidence, and translational readiness of circRNA therapeutics, with emphasis on their unique ability to address unmet clinical needs in chronic and rare diseases.

Epidemiology / Disease Burden

Many chronic illnesses and inherited disorders, including hemophilia, lysosomal storage diseases, and endocrine deficiencies, necessitate lifelong replacement therapies. These conditions affect millions globally and impose significant burden on patients and healthcare systems due to frequent injections, variable therapeutic levels, and poor adherence. Limitations in maintaining stable protein concentrations often result in suboptimal disease control, increased risk of complications, and reduced quality of life. The unmet demand for therapies that enable sustained therapeutic protein production, minimize dosing frequency, and improve patient outcomes is substantial and growing, particularly with the rising prevalence of chronic diseases in aging populations.

Pathophysiology

Many target diseases for protein replacement therapies arise from genetic mutations or acquired defects leading to absent or dysfunctional proteins. Current treatments rely on exogenous protein administration, which is limited by rapid degradation, immune responses, and fluctuating pharmacokinetics. CircRNA therapeutics aim to overcome these challenges by introducing synthetic or engineered circRNAs encoding the desired therapeutic protein. Due to their circular structure, these molecules evade typical RNA degradation pathways, allowing them to persist longer within cells and continuously drive protein synthesis using the host\'s translational machinery. This mechanism provides a closer approximation to physiological protein production as opposed to erratic peaks and troughs associated with periodic dosing.

Risk Factors

Patients with genetic diseases requiring protein replacement face increased risk of complications from treatment interruptions, immunogenicity, and infusion-related reactions. Additional risk factors include variable pharmacokinetics due to renal or hepatic impairment, development of neutralizing antibodies, and challenges related to venous access or injection site reactions. Furthermore, populations with poor healthcare access, pediatric patients, and those with comorbidities are particularly vulnerable to the limitations of conventional therapies. CircRNA strategies may mitigate some of these risk factors by reducing the frequency of interventions and potentially lowering immunogenic exposure due to less frequent administration.

Clinical Features

Clinical manifestations of diseases amenable to circRNA therapeutics vary widely. For example, hemophilia presents with spontaneous bleeding and joint damage, while enzyme deficiencies may manifest as multi-organ involvement, neurocognitive decline, or metabolic derangements. Inadequate or fluctuating protein replacement worsens clinical outcomes and increases morbidity. The ideal therapy would provide consistent, physiologically relevant protein levels to prevent acute and chronic complications, reduce hospitalizations, and improve patient quality of life. CircRNA-based approaches strive to fulfill these clinical imperatives by ensuring durable protein expression after a single or infrequent administration.

Diagnosis

Diagnosis of candidate diseases for circRNA therapeutics typically involves clinical assessment, genetic testing, and biochemical measurements of protein activity or substrate accumulation. Early and accurate diagnosis is critical for timely initiation of replacement therapy and prevention of irreversible sequelae. In future clinical applications, diagnostic algorithms may also incorporate patient-specific factors such as immunogenic risk, pharmacogenomics, and baseline protein levels to individualize circRNA therapy and optimize outcomes.

Treatment & Management

Conventional treatment options for protein-deficiency disorders include recombinant protein infusions, enzyme replacement therapies, and, in some cases, gene therapy. While these approaches have improved survival and quality of life, they are hindered by short protein half-lives, frequent dosing requirements, and logistical challenges. CircRNA therapeutics represent a new class of medicines designed to be delivered via lipid nanoparticles or other vehicles, whereupon they enter target cells and persistently direct synthesis of the therapeutic protein. Preclinical models have demonstrated robust, durable protein production lasting weeks to months after a single administration, significantly outlasting linear mRNA analogs. Management with circRNA therapies would ideally reduce treatment burden and enhance adherence, particularly in pediatric and resource-limited settings.

Recent Advances / Emerging Therapies

Recent years have witnessed rapid progress in circRNA engineering, chemical modification, and delivery systems. Advances in in vitro ligation and autocatalytic ribozyme-based synthesis enable scalable production of high-purity circRNAs. Modifications such as N6-methyladenosine (m6A) incorporation, optimization of internal ribosome entry sites (IRES), and codon optimization further enhance translational efficiency. Lipid nanoparticle formulations protect circRNAs from degradation and facilitate targeted delivery to specific tissues, as demonstrated in preclinical models of hemophilia, metabolic disorders, and cancer immunotherapy. Early-phase clinical studies are underway, evaluating safety, pharmacokinetics, and efficacy of circRNA therapeutics in humans. These developments position circRNA as a frontrunner among next-generation biotherapeutics.

Guideline Recommendations

While formal guideline recommendations for circRNA therapeutics are pending, translational research and regulatory agencies emphasize rigorous preclinical evaluation, standardized manufacturing, and comprehensive safety monitoring. Key considerations include immunogenicity, biodistribution, off-target effects, and long-term persistence of circRNA and its protein products. Multidisciplinary collaboration across molecular biology, clinical pharmacology, and regulatory science is essential to establish best practices for clinical development and integration of circRNA therapies into standard care pathways. As clinical data matures, professional societies are expected to issue evidence-based guidelines on patient selection, dosing regimens, and monitoring protocols for circRNA-based treatments.

Conclusion

Circular RNA therapeutics offer a transformative approach to sustained protein production, addressing major challenges associated with conventional protein replacement strategies. By leveraging the inherent stability and translational capacity of circRNAs, these therapies hold promise for reducing dosing frequency, improving patient adherence, and delivering clinically meaningful benefits in a range of protein-deficiency disorders. Ongoing research continues to optimize circRNA design, delivery, and safety, paving the way for their integration into mainstream clinical practice. As the field advances, multidisciplinary collaboration and evidence-based guidelines will be vital to realize the full potential of circRNA therapeutics in improving patient outcomes.