Achieving Targeted Delivery with Nanoscale Systems

Efficient and effective delivery of complex and challenging drug substances is an ongoing issue facing developers of modern medicines. Delivery systems must overcome poor solubility and bioavailability while achieving targeted delivery to achieve maximum efficacy with lower doses while also minimizing unwanted side effects. Nanoscale technology is proving to be an attractive solution on all accounts, particularly for realizing targeted delivery into specific types of cells and across biological barriers.

Many advantages of nanotechnology

Many of the unique properties of nanoscale delivery systems can be attributed to their small size (< 100 nanometers). At this scale, the surface area/volume ratio is high, leading to unique physical, chemical, and biologic properties. The ability to tune the surface properties of nanomaterials through functionalization further increases their utility for drug delivery, particularly with respect to their targeting capabilities. Nanoscale delivery systems can not only increase the bioavailability of poorly water-soluble drugs; they can also protect sensitive APIs from degradation and, when appropriately designed, remain stable in the bloodstream, allowing long-term sustained release and more consistent pharmacokinetics (1). The greater cellular uptake of nanoscale delivery systems also contributes to improved efficacy and reduced side effects.

Another important advantage of nanoscale delivery systems is the ability to deliver two or more APIs simultaneously. Nanoscale co-delivery systemsoffer improved performance for combination therapies because they deliver the different drug substances in a homogeneous manner (2). Ideal nanoscale carriers are stable, small, but able to support sufficient drug loading of both hydrophobic and hydrophilic APIs; protect the loaded drug from degradation; are suitably functionalized to exhibit a high binding affinity to target cells/ tissues; and have good biocompatibility.

Many different types of nanoscale delivery systems (e.g., lipidic, polymeric, inorganic, biomimetic) provide opportunities for designing solutions with high specificity for the particular API, disease target, and route of administration. In fact, they support the loading of most types of drug substances, including small molecules, proteins, nucleic acids, and diagnostic agents (1). They can also be customized in support of personalized medicines, and some have been developed that are capable of exhibiting both therapeutic and diagnostic activities (theranostics).

Several options

As more information is gained about the benefits of nanoscale delivery systems, researchers are exploring the applicability of a growing variety of nanoscale materials for this purpose (1–3). Nanoparticles have attracted particular attention, including those based on lipids, polymers (natural and synthetic), lipid-polymer hybrids, dendrimers, inorganic materials (metals, magnetic compounds, carbon nanotubes, silica-based systems, etc.). Other nanocarriers include nanocrystals; DNA-based systems; extracellular vesicles such as exosomes, microvesicles, apoptotic bodies, and phagosomes; nanoemulsions; and micelles.

A few disadvantages

Like any drug delivery technology, nanoscale systems are not perfect solutions and, depending on the particular nanotechnology, have different sets of limitations (1). Some of the nanomaterials used for drug delivery can, if the systems are not designed appropriately, pose toxicity and biocompatibility issues. One example is metallic nanoparticles if they accumulate in the body.

Similarly, while some nanoscale delivery systems can exhibit prolonged lifetimes in the bloodstream, others have short circulation times or can be viewed as foreign materials by the immune system and rapidly cleared. Some nanomaterials may also exhibit unexpected/unpredictable interactions with biological systems that lead to detrimental effects. These uncertainties and complexity of nanoscale drug delivery systems often lead to regulatory challenges.

The development of robust, predictable large-scale manufacturing processes can be a significant hurdle for some nanomaterials/nanoscale delivery systems. In addition, stability during storage can be an issue for some nanoscale systems, requiring careful formulation development. All these challenges tend to lead to high costs for therapeutics and vaccines leveraging nanoscale drug delivery systems.

Passive and active targeting

Highly targeted delivery with nanoscale systems can be achieved using passive or active mechanisms. Passive delivery involves accumulation of the nanoscale system in the targeted cell/ tissue through enhanced permeability and retention (EPR), which is dictated by the shape, size, charge, and other surface properties of the unfunctionalized nanomaterial (4). This approach does not, however, completely reduce delivery to healthy cells, which can result in off-target effects.

Active targeting, meanwhile, is realized through functionalization of the surface of the nanocarrier system to both increase cellular uptake and ensure delivery to specific cells/tissues (4). Ligands are attached to the surfaces of the nanocarriers that have high binding affinity to receptors specific to the target cells. These ligands can include a range of compounds, including antibodies, aptamers, peptides, small molecules, and biomimetic materials such as cell membranes, among others. As an example, nanoscale delivery systems can be functionalized with PD-L1 monoclonal antibodies in anticancer therapies.

A few disease highlights

The targeting ability of nanoscale systems can benefit treatments for all disease classes, but this capability is of even greater importance in certain applications. Targeting of cancer cells is a major goal in oncology, as traditional systemic treatment result in severe side effects. The ability of nanocarriers to selectively attack targeted tumor cells allows for delivery of higher doses to improve efficacy while reducing cytotoxicity (1).

Therapeutic hyperthermia is a unique treatment made possible by use of nanoparticle delivery systems (1). Once the nanoparticles are localized in the tumor, they are exposed to laser radiation or an applied magnetic field, leading to an increase in temperature sufficient to kill the cancer cells. The improved targeting capability of nanoscale delivery systems also leads to improved activation of immune cells in cancer vaccines.

Nanoscale delivery systems are improving treatments for infectious diseases including human immunodeficiency virus (HIV) due to their targeting ability. Patient adherence with traditional medications is often low due to the high incidence of side effects. The high on-target bioavailability of nanoscale drugs thus has a measurable, positive impact.

Finally, nanoscale delivery systems are also improving the effectiveness of treatments for autoimmune diseases due to their improved targeting capability (1). Nanoparticles have been shown to deliver antigens and immunomodulators to antigen-presenting cells and lymphocytes with high specificity, and thus more efficiency, inducing antigen-specific tolerance in vivo.

Moving beyond lipid nanoparticles

Lipid nanoparticles (LNPs) have received significant attention in recent years as attractive systems for the delivery of nucleic acids for vaccine applications. Their success was clearly demonstrated with the approval of the two messenger RNA vaccines against COVID-19, according to McDavid Stilwell, CFO with CPTx. He notes, however, that some of the properties that make LNPs useful for vaccine applications (inflammatory behavior) also present substantial hurdles for systemic therapeutic delivery applications that require higher doses and for which adverse inflammation is undesirable.

There are also issues with targeting LNPs away from the liver, Stilwell observes. The field is working hard to overcome cell targeting challenges, but solutions are not expected soon. Stilwell notes that LNPs have now been successfully engineered to target immune cells, and CPTx is using this approach to deliver single-stranded DNA for its in vivo chimeric antigen receptor (CAR)-T development program.

In addition to ensuring targeted specificity and minimal off-target effects, key challenges with LNPs— and nanoscale delivery systems in general—include achieving consistent manufacturing scalability, controlling batch-to-batch variability, overcoming biological barriers (immune recognition, clearance, endosomal escape), and demonstrating robust safety profiles, adds CPTx’s CEO Hendrik Dietz. “Achieving reliable, reproducible, and cost-effective large-scale production remains critical, especially for transitioning from preclinical validation to clinical and commercial stages,” he says.

CPTx believes that DNA nanostructures presenting an immune-silent vector are a better alternative to currently available gene delivery technologies. “These nanocarriers are optimal for precision targeting, programmable drug release, and transient genetic expression, making them valuable for controlled gene editing and transient immunotherapies,” Stilwell contends. The goal, he adds, is to present a delivery solution that is not only technically superior, but that can also be manufactured in a cost-effective fashion.

Programmable DNA nanocarriers for in vivo gene delivery

The single-stranded DNA nanocarriers CPTx is developing are intended to enable direct, targeted in-vivo gene delivery. Scalable, high-purity DNA single- strand synthesis platforms, both for the gene encoding components of the nanoparticles and the helper material needed to build the nanocarriers, have been an important initial focus to ensure manufacturing challenges are not an issue, according to Dietz.

These new DNA nanostructures are precision engineered from therapeutic immune-silent DNA single-strands using a technique known as programmable DNA nanofabrication, uniquely combining precise control over composition and 3D shape, as well as delivery functionality. “The result is precise cell targeting without external carriers, bypassing issues associated with existing delivery technologies such as viral vectors and lipid nanoparticles, including manufacturing hurdles, immunogenicity (in the case of viral vectors), and targeting challenges,” Dietz states.

The DNA nanocarriers “integrate therapeutic payloads and delivery functionality into rationally engineered particles designed to realize episomal, non-integrated gene expression in target cells or tissues with minimal side effects,” Dietz explains. Functionalization in a site-specific fashion with molecular targeting motifs promotes highly selective binding to specific cells or tissues and efficient cellular uptake, he says.

The modular approach also allows for simultaneous delivery of multiple therapeutic gene payloads and/or simultaneous targeting of multiple tissues or cell types, enhancing effectiveness, safety, and control compared to traditional approaches, according to Dietz.

CPTx is currently working to improve the delivery efficiency in various prototypes while also validating safety and efficacy in animal models with the goal of licensing this DNA nanocarrier delivery solution to drug developers with established payload genes and target tissues.

References

1. Tenchov, R. et al. Transforming Medicine: Cutting-Edge Applications of Nanoscale Materials in Drug Delivery. ACS Nano. 2025 19 (4). https://pubs.acs.org/ doi/10.1021/acsnano.4c09566

2. Sun, L. et al. Better Together: Nanoscale Co-Delivery Systems of Therapeutic Agents for High-Performance Cancer Therapy. Front. Pharmacol., Sec. Pharmacol. Anti-Cancer Drugs. 2024 Vol. 15. DOI: 10.3389/fphar.2024.1389922.

3. Li, Y.; et al. A Nanoscale Natural Drug Delivery System For Targeted Drug Delivery Against Ovarian Cancer: Action Mechanism, Application Enlightenment And Future Potential. Front. Immunol., Sec. Canc. Immun. & Immunother., 2024 Vol. 15. https://doi.org/10.3389/\ fimmu.2024.1427573

4. Fan, L.; Wang, A.; and Shi, D. Targeted Nanoscale Drug Delivery Systems For Melanoma Therapy. J. Drug Del. Sci. & Tech. 2023 Vol. 86, 104724. https://doi. org/10.1016/j.jddst.2023.104724