Establishing Reproducible Polymer Nanoparticle (PNP) Manufacturing

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Polymer nanoparticles (PNPs) could be the key to unlocking safer, more effective, and more affordable gene therapies. Battelle’s HIT SCAN™ platform seeks to tackle the final hurdles: precision design, robust manufacturing, and proven reproducibility. With HIT SCAN™, PNP-based therapies are closer than ever to becoming a clinical reality.

The Promise of PNPs for Gene Therapy

Gene therapy holds incredible promise to treat and even cure diseases ranging from genetic disorders to cancer, but delivery challenges have limited gene therapy success in the clinic for many diseases. PNPs offer game-changing potential to overcome these challenges due to their versatility and high payload capacity.

In gene therapy, genetic material, such as DNA or RNA, is introduced into cells to fix or replace faulty genes or direct cells to make a specific protein. Modified viruses, such as adeno-associated viruses (AAVs), were the first delivery option for gene therapies and are still widely used. However, viruses have a limited payload capacity of about 5 kilobases (5,000 base pairs of DNA or RNA), which limits the cargo types that AAVs can deliver. In addition, AAVs can trigger undesirable and potentially dangerous immune responses, are complex and expensive to manufacture, and require strict temperature control across the supply chain.

More recently, lipid nanoparticles (LNPs) have been used to deliver genetic payloads, in particular mRNA. While LNPs have a larger payload capacity (10-15 kilobases), they are limited in their ability to deliver the largest DNA molecules, mainly apply to only liver delivery, lack the expansive design space and tunability of PNPs, and have similar cold storage requirements as AAVs.

In contrast to AAVs or LNPs, PNPs possess expansive versatility and design capabilities that dramatically unveil a vast new universe for gene therapy and other targeted therapies. PNPs are payload-agnostic, meaning they can be engineered to carry different cargo types, including small molecule drugs, nutrients, proteins and peptides, and genetic material. In addition, PNPs offer:

Larger payload capacity, up to 50 kilobases or more, allowing them to deliver entire genes and other large, complex payloads.
Lower immunogenicity, meaning they are less likely to produce an immune response, even when patients need multiple treatments.
Active targeting capabilities to enable precise gene, drug, or protein delivery to specific cell types or organ systems.
Straightforward, cell-free, and cost-effective manufacturing, particularly compared to virus-based therapy manufacturing processes.
Shelf stability, simplifying logistics and storage, especially in areas without cold-chain infrastructure.

The Infinite Design Space for PNPs

Virtually endless possible structures exist for PNPs, depending on reagents and ratios, reaction times and temperatures, and other parameters. This design flexibility allows for high customizable PNP structures, surface chemistries, and payload capacities. Each slight modification in these variables influences particle behavior in terms of stability, targeting, drug release, and immune compatibility. For example:

Changing the core size within the PNP structure may improve drug loading, accommodating large DNA molecules or multiple drug types for combination therapies.
Adjusting surface charge or shell structure can increase PNP uptake by certain cells, enhancing targeted delivery to specific tissues and reducing off-target effects.
Modifying polymer recipes to alter degradation rates allows for finely controlled drug release and enables sustained delivery over days or weeks.
This “infinite design space” creates endless opportunities for new and innovative PNP delivery vehicles. The trick is discovering which new variations work best for a particular purpose and then recreating that structure precisely and repeatedly.

The Reproducibility Problem

Despite their potential, PNPs still lag far behind other delivery approaches in the clinic. To date, AAVs, LNPs and more traditional drug delivery methods, such as aerosols, transdermal patches, and oral preparations, have shown more clinical success. So far, only a small number of polymer-based nanoparticles have made it through the U.S. Food and Drug Administration (FDA) approval process.

A lack of standardized, reproducible manufacturing and characterization processes has been a major barrier to the adoption of PNP-based therapies. To make PNPs a medically and commercially viable solution, chemists have three big problems to solve:

Identifying candidate PNPs that will work for a given payload and target.
Screening PNP candidates to determine which are safe and efficacious for the intended purpose.
Controlling manufacturing to limit variability in the final product.

The reproducibility problem has been a particular challenge and has slowed the clinical translation of PNPs. Even slight variations in the polymerization process can lead to significant differences in particle characteristics, including size, charge, and stability. Thus, process variability often results in inconsistent PNP batches, which makes it difficult to ensure uniform drug delivery and reliable therapeutic outcomes.

Moving from small-scale lab production to larger-scale manufacturing amplifies these reproducibility issues. Processes that work at a small scale can become difficult to replicate precisely in larger batches, thereby affecting quality control and the ability to consistently produce PNPs with desired characteristics. Without reliable, reproducible methods, PNPs struggle to meet the stringent standards needed for regulatory approval and widespread therapeutic use.

HIT SCAN™: Advancing PNP Reproducibility and Scale-Up

Battelle addresses this reproducibility issue with the HIT SCAN™ (High-Throughput Synthesis, Characterization, and Assessment of Nanoparticles) non-viral gene delivery vehicle discovery and development platform. This platform enables researchers to systematically synthesize, evaluate, and test large quantities of PNPs efficiently. By integrating high-throughput synthesis, biological characterization, and advanced machine learning, HIT SCAN™ facilitates the development of engineered PNPs with consistent and predictable performance.

HIT SCAN™ incorporates three advanced technologies:

Automated polymer library synthesis for rapid and consistent manufacturing of PNPs using reversible addition-fragmentation chain transfer (RAFT) polymerization.
High-throughput in vitro/in vivo screening methods to quickly identify which PNPs have the best performance.
Machine learning modeling to identify successful designs and predict functional performance.

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Together, these three components make HIT SCAN™ a powerful tool for developing consistent, reliable PNPs, reducing variability, and enabling scale-up production for clinical applications. In a series of experiments, HIT SCAN™ demonstrated significantly improved results in terms of consistency and reproducibility, with much tighter design tolerances for PNPs produced using improved HIT SCAN™ processes compared to traditional synthesis methods.

“The results, some of which highlight the dramatic improvement from Process #1 to Process #2 below (Figure # A-B), were presented at the Controlled Release Society (CRS) Annual Meeting in July 2024. Moreover, the CRS presentation also included results demonstrating tight control over monomer composition within a polymer (Figure # C). The research team also examined biodistribution for various PNPs to gain insights into how polymer design impacts where they end up in the body.

This iterative, AI-enabled design process allows Battelle to speed up the process of tailoring PNPs for specific payload characteristics and therapeutic targets as well as identifying and screening promising candidates while controlling process parameters to reduce variability.

The experiments described here are part of Battelle’s ongoing efforts to advance delivery technologies for gene therapy. At Battelle, we are uniquely positioned to tackle these kinds of challenges due to our non-profit status and breadth of expertise. Battelle’s non-viral drug delivery team* pulls together expertise in material science, immunology, molecular biology, biomedical engineering, mechanical engineering, data science and other related fields.

With HIT SCAN™, Battelle is unlocking the true potential of PNPs to deliver safe, effective and accessible therapies for conditions once thought untreatable. The insights gained during these experiments lay the foundation for the next steps of translating polymer nanoparticle production into clinical use.

*This project was completed as part of Battelle’s Internal Research and Development (IRAD) program. Special thanks to: