PlasmidFactory’s Minicircle DNA: Raising the Bar in Gene and Cell Therapy

Gene and cell therapy is moving fast – and in a clear direction. Programs are pushing toward more complex payloads, virus-free engineering, and manufacturing models that can scale from early research to late-stage clinical supply without exploding timelines or cost of goods. At the same time, the field is confronting familiar constraints: viral-vector bottlenecks, payload limits, and the risk that DNA elements that are useful for bacterial cloning can become unwanted baggage when the DNA is used as starting material for therapeutics.

Against this backdrop, one innovative DNA format is gaining momentum because it tackles several of these challenges at once: Minicircle (MC) DNA – a streamlined, bacterial backbone–free vector built for efficient gene expression and improved compatibility with sensitive cells and demanding downstream processes.

Figure 1 – Minicircle manufacturing principle

A “minimalistic” DNA vector – designed for performance and safety

In simple terms, a plasmid is a circular DNA molecule originally designed for bacteria. It typically carries not only the therapeutic expression cassette (promoter, gene of interest, regulatory elements), but also bacterial maintenance parts such as an origin of replication and antibiotic resistance markers. Minicircle DNA keeps what you need for expression in target cells – and removes what you don’t.

PlasmidFactory’s Minicircle technology starts with a customer’s gene of interest cloned into a parental plasmid, followed by an intramolecular recombination step that separates the expression cassette from the bacterial backbone. The resulting Minicircle is a minimalistic, circular, supercoiled DNA construct that consists almost exclusively of the expression cassette plus a short residual “SCAR” region (typically <150 bp) without functional bacterial sequences (see Fig. 1). This true bacterial backbone-free, "less-is-more“ format sets the Minicircle apart from concepts like “mini- or nanoplasmids“ that still carry bacterial sequences, and yields several proven, practical and biologically meaningful advantages (see Fig. 2):

• Lower immunogenicity risk (fewer CpG motifs; no functional bacterial backbone elements)
• Reduced DNA toxicity, which can matter in fragile primary cells (e.g., T cells, HSCs)
• Higher transfection and expression efficiency for equivalent expression cassettes, reported across multiple cell types and delivery methods
• Lower chance of unwanted carryover of bacterial sequences into downstream products (particularly relevant in viral vector production)

Figure 2 – Minicircle features & benefits

Who is PlasmidFactory – and why does it matter for Minicircles?

PlasmidFactory GmbH is an independent, Europe-based CDMO headquartered in Bielefeld (Germany), manufacturing plasmid and Minicircle DNA from research to clinical GMP-grade.
With 25+ years of DNA manufacturing experience and 3,500+ DNA constructs with a success rate of 99.9% delivered, the team combines hands-on process development with deep analytical know-how and GMP execution – run by scientists, for scientists, and supportive even for smaller, early-stage programs.

A key differentiator is its portfolio of specialized and innovative DNA formats and solutions, with GMP-grade Minicircles as a core focus. The offering also includes ITR-stabilized constructs for AAV workflows (i.e., ITRRESCUE® and ITRPROTECT®), MIDGE® vectors, and optimized mRNA templates, including POLY(A)RESCUE® technology – enabling smooth scale-up without changing vector formats mid-program.

For advanced therapies, the manufacturing setup is as critical as the DNA design itself. DNA products are available across Research, High Quality (HQ), and GMP grades, enabling programs to align material quality, analytical depth, and documentation with their specific development stage and regulatory context. In particular, PlasmidFactory’s GMP production is based on a dedicated, modern facility with end-to-end single-use workflows, strong segregation to prevent cross-contamination, and streamlined scale-up capabilities. This setup is supported by comprehensive quality control, including established release testing and high-resolution capillary gel electrophoresis (CGE) to quantify DNA topology (supercoiled, open circular, and linear forms), alongside complementary QC services and GMP-compliant storage. Together, this enables seamless progression from early research through clinical and commercial manufacturing.

Where Minicircles make the difference: key application areas

Minicircle DNA is not "just another vector option" – it’s increasingly used as an enabling format across modalities, especially where high transfection efficiency and payload flexibility support virus-free workflows, but also where starting material purity matters for viral vector and mRNA production (see Fig. 3).

Figure 3 – Main application areas of the Minicircle

1) Virus-free cell therapy: from ex vivo manufacturing towards novel in vivo approaches

One of the most active areas is virus-free genetic engineering of immune cells and stem cells, typically using electroporation/nucleofection, and often combined with transposon systems such as Sleeping Beauty or PiggyBac. In these workflows, using Minicircle DNA – without bacterial backbone sequences – can reduce DNA-related toxicity and innate immune activation while improving transfection and expression (see Fig. 4). That performance advantage is particularly relevant for sensitive primary cells under clinically realistic manufacturing constraints. Several peer-reviewed studies support this direction (e.g., Monjezi et al., 2016; Holstein et al., 2018; Bexte et al., 2024; Diez et al., 2025): Minicircle-based Sleeping Beauty approaches have been shown to enable efficient, scalable engineering of CAR-T cells, CAR-NK cells, and HSPCs, and align with a workflow that is simpler, faster, and more cost-efficient than viral-vector routes – an approach that is also relevant for other receptor-engineered T-cell modalities such as TCR-T cells. Importantly, Minicircle-based Sleeping Beauty gene transfer has already moved into clinical testing, including programs such as TranspoCART19, CARAMBA and LION-1. In addition, Minicircle formats are increasingly discussed in the context of CRISPR workflows, for example as compact DNA payloads and as HDR donor templates in genome editing strategies (e.g., Tennant et al., 2020). Looking ahead, Minicircle DNA is also being evaluated as a payload for nanoparticle-based delivery, which fits the broader industry push to move beyond ex vivo processing and enable more direct, in vivo genetic engineering – where high-performance, high-purity starting material becomes a key enabler.

Figure 4 – Transfection data (luc): plasmids vs. Minicircle

2) AAV vector production: cleaner starting material, higher functional yield

AAV manufacturing places exceptional demands on DNA starting material, as even small amounts of bacterial backbone sequences can be unintentionally encapsidated during vector assembly – a well-described safety concern known as retro-packaging. By replacing conventional plasmids with Minicircle DNA, which lacks functional bacterial backbone elements, this risk can be effectively eliminated, resulting in higher vector purity and improved product consistency (Schnödt et al., 2016).

Beyond purity, Minicircle-based AAV production has been shown to deliver substantial gains in functional vector output. Published data report increases in functional virus titers, typically in the range of three- to four-fold, together with a higher proportion of genome-filled capsids compared with plasmid-based systems (Schnödt et al., 2016). In addition, these studies indicate strongly improved transduction efficiency, reaching up to a 30-fold increase. Together, these effects point to a more efficient use of production capacity and a reduction in downstream processing burden and cost per functional dose.

These Minicircle-specific advantages can be further extended when combined with streamlined AAV production strategies such as 2-vector systems, and with approaches designed to preserve ITR integrity, a key determinant of AAV genome replication and packaging efficiency (Grimm et al., 2003). In combination, this integrated portfolio addresses central AAV manufacturing challenges – safety, yield, consistency, and cost efficiency – without adding process complexity and while remaining compatible with GMP-grade production.

3) mRNA synthesis and vaccine development: cleaner templates, more robust workflows

Beyond cell and viral vector manufacturing, Minicircle DNA might serve as a cleaner DNA template for in vitro transcription (IVT)-based mRNA production – reducing unwanted backbone-derived sequences and supporting reproducibility, especially when paired with controlled DNA linearization prior to transcription. To support this step, PlasmidFactory offers linearized plasmid and Minicircle DNA as a dedicated service e.g. for starting material in mRNA production, with application-aligned documentation options depending on program needs.

A second, often underestimated lever sits inside the template itself: the poly(A) design. PlasmidFactory’s POLYARESCUE® concept helps stabilize and optimize poly(A) elements in template constructs – aiming to improve robustness of template performances, especially when moving from exploratory design to more standardized manufacturing.

What founder and CEO have to say about PlasmidFactory’s vision

“When we founded PlasmidFactory, our goal was simple: to provide DNA that truly works in real-world therapeutic development. Seeing technologies like Minicircle DNA support clinical programs today confirms that long-term scientific focus and quality-driven innovation can make a real difference for advanced therapies.” Dr. Martin Schleef, Founder

“Building on this foundation, we are continuously expanding our capabilities in GMP plasmid and Minicircle DNA manufacturing. Minicircle DNA in particular is becoming an important enabling technology for advanced therapies, and we are committed to supporting customers with reliable, scalable DNA solutions from early development to clinical and commercial supply.”
Dr. Dirk Winnemöller, CEO

Voices from the field – highlighting strong gene transfer performance in gene and cell therapy

For many teams, the appeal of Minicircle DNA is not just conceptual – it shows up in day-to-day engineering performance and manufacturing outcomes. Dr. Ram Shankar, Chief Scientific Officer at PlasmidFactory, describes Minicircles as “the logical next step in non-viral gene transfer,” emphasizing that removing bacterial backbone sequences leaves “only the therapeutic expression cassette in a small, supercoiled DNA molecule” – a design he links to higher transfection efficiency, more stable expression, and lower cytotoxicity in sensitive cells.

That practical impact is echoed by collaborators in virus-free cell therapy. Prof. Dr. Michael Hudecek (Universitätsklinikum Würzburg & Fraunhofer IZI) highlights strong gene transfer performance in primary human T cells, reporting rates “in excess of 50–60%,” described as “5 to 6-fold higher than with plasmid DNA,” and notes a long-standing scientific collaboration with PlasmidFactory spanning more than a decade.

On the viral vector side, Dr. Katrin Teschner (Sartorius Xcell) points to measurable manufacturing benefits, stating that when Minicircles were used for AAV manufacture they observed “an increase of the genomic titer between 300–400%” and “an increase of the yield per cell.”

This emphasis on translational readiness and manufacturing robustness also shows up at the partnership level: in the context of PlasmidFactory’s collaboration with Fraunhofer IZI, Prof. Hudecek underscores the fit between high-quality DNA supply and advanced process development, while PlasmidFactory leadership frames the shared goal as streamlining virus-free workflows to bring promising therapies forward more efficiently.

Cost, scalability, and GMP readiness: making advanced therapies manufacturable

In many gene and cell therapy programs, DNA is not the primary cost driver – until it becomes a bottleneck for scale, quality, or regulatory progression. Minicircle DNA helps address this challenge by combining a streamlined molecular design with manufacturing concepts that support speed, safety, and efficiency across applications.

At the process level, Minicircles can reduce the DNA burden per application: their compact, backbone-free structure supports strong expression with lower DNA input, which can translate into reduced transfection stress, improved reproducibility, and lower downstream variability. In addition, simplified DNA architectures – particularly in workflows such as virus-free cell therapy or AAV production – streamline processes and ease analytical and QC demands, contributing to more efficient and cost-conscious manufacturing.

Equally important is the ability to scale without changing the underlying DNA format. PlasmidFactory positions Minicircle production within a quality-grade framework that spans Research, High Quality (HQ), and GMP, allowing programs to progress from early feasibility studies through clinical trials and toward commercialization while maintaining continuity in vector design and analytics. This grade alignment is especially relevant for later-stage therapies, where changes in DNA source or format can introduce regulatory and comparability challenges.

On the GMP side, Minicircle manufacturing is supported by a dedicated, modern production environment, designed to meet the needs of advanced therapies. Key elements include end-to-end single-use equipment, strong segregation concepts to prevent cross-contamination, controlled cleanroom operations, and pharmaceutical-grade utilities such as qualified water systems. Together, these features support consistent quality, regulatory compliance, and suitability for late clinical and commercial supply.

Figure 5A and B – PlasmidFactory’s dedicated GMP facility

Outlook: Minicircle DNA as a future-ready gene delivery technology

Taken together, Minicircle DNA is more than a minimized vector format. By removing non-essential bacterial elements while preserving full functional flexibility, it enables virus-free and hybrid engineering strategies, shortens development timelines, and supports cleaner, safer, and more efficient manufacturing across cell therapy, viral vector production, and mRNA-based applications – from early research through to GMP-grade supply.

As gene and cell therapy moves beyond viral workflows, the role of DNA across therapeutic manufacturing is being redefined. Depending on the application, DNA may function as a starting material or as a directly acting therapeutic component, with consistently high expectations around quality, safety, and process control. Beyond its formal regulatory classification, DNA has increasingly become a quality-, safety-, and process-defining element that can shape regulatory pathways, manufacturing robustness, and long-term scalability.

Minicircle DNA sits squarely at this transition point: its streamlined sequence architecture aligns with rising expectations around purity and safety, while its performance advantages support increasingly complex payloads and delivery strategies.

Looking ahead, Minicircle DNA is well positioned for future therapeutic approaches – including non-viral in vivo delivery, advanced genome editing, and next-generation vector systems – where flexibility, consistency, and regulatory readiness will matter as much as biological efficacy.

Further information is available at www.plasmidfactory.com

PlasmidFactory GmbH, based in Bielefeld, Germany, is a specialized CDMO for plasmid and Minicircle DNA, supporting projects from research through clinical phases to commercialization in cell and gene therapy, vaccine development, and beyond. With over 25 years of experience, the company provides scalable custom DNA production up to GMP grade.

For further information you can contact:

Dr. Marcello Stein (Senior Director Commercial)

PlasmidFactory GmbH

Meisenstraße 96

33607 Bielefeld, Germany

+49 521 2997 350

presse@plasmidfactory.com

www.plasmidfactory.com