Lipid nanoparticles are tiny particles made of lipids, which are molecules that can form biological membranes. They can be used to deliver genetic material, such as DNA or RNA, into cells for gene therapy. Gene therapy is a technique that aims to treat or prevent diseases by modifying the genes of cells.
Why Use Lipid Nanoparticles For Gene Therapy?
Gene therapy has great potential for treating various diseases, such as infectious diseases, cancer and genetic disorders. Delivering genetic material into cells is the hard part, because it can be degraded by enzymes, rejected by the immune system, or trapped inside endosomes, the membrane-bound compartments inside cells. Genetic material therefore needs a delivery system that carries it past those barriers rather than merely mixing with it.
Lipid nanoparticles are one of the most promising delivery systems for gene therapy, because they have several advantages:
- They can protect genetic material from degradation and immune recognition.
- They can fuse with cell membranes and release genetic material into the cytoplasm.
- They can be designed to target specific cells or tissues by modifying their surface properties.
- They can be easily produced and scaled up for clinical use.
- They have low toxicity and immunogenicity compared to viral vectors, which are another common delivery system for gene therapy.
The comparison with viral vectors decides many programs. A virus enters cells efficiently, and the immune response it provokes is the price; that trade-off is set out in The Role of AAV in Gene Therapy: Immune Responses and Toxicity. A lipid nanoparticle is a chemical assembly, so its potency can be tuned by changing its composition.
How Do Lipid Nanoparticles Work For Gene Therapy?
Lipid nanoparticles are composed of different types of lipids, such as cationic lipids, helper lipids, fusogenic lipids and PEGylated lipids. Cationic lipids have a positive charge that can bind to the negative charge of genetic material, forming a complex called lipoplex. Helper lipids help to stabilize the lipoplex and enhance its delivery efficiency. Fusogenic lipids help to fuse the lipid nanoparticle with the cell membrane and release the genetic material into the cytoplasm. PEGylated lipids have a polyethylene glycol (PEG) chain attached to them, which can shield the lipid nanoparticle from the immune system and prolong its circulation time in the blood.
Each component is a compromise. The charge that binds cargo also binds serum proteins, and the PEG that prolongs circulation also limits how freely the particle interacts with the target cell.
Lipid nanoparticles can be administered by different routes, such as intravenous injection, intramuscular injection, inhalation or topical application. Once they reach the target site, they interact with the cell membrane and deliver the genetic material into the cell. The genetic material then enters the nucleus and either replaces or repairs a defective gene, or expresses a therapeutic protein.
What Are Some Examples Of Lipid Nanoparticles For Gene Therapy?
Lipid nanoparticles have been successfully used for delivering different types of genetic material, such as mRNA, siRNA, plasmid DNA and CRISPR-Cas9. Some examples of lipid nanoparticles for gene therapy are:
- Onpattro. This is the first FDA-approved lipid nanoparticle-based drug for treating hereditary transthyretin-mediated amyloidosis (hATTR), a rare genetic disease that causes nerve damage and heart failure. Onpattro delivers siRNA that silences the mutant transthyretin (TTR) gene, reducing the production of abnormal TTR protein that forms amyloid deposits in tissues.
- BNT162b2. This is one of the COVID-19 vaccines developed by Pfizer and BioNTech, which uses lipid nanoparticles to deliver mRNA that encodes the spike protein of SARS-CoV-2, the virus that causes COVID-19. The mRNA instructs the cells to produce the spike protein, which triggers an immune response against the virus.
- CTX001. This is an experimental gene-editing therapy for treating beta-thalassemia and sickle cell disease, which are inherited blood disorders that affect hemoglobin production and function. CTX001 uses lipid nanoparticles to deliver CRISPR-Cas9, a molecular tool that can cut and edit DNA. The CRISPR-Cas9 targets and corrects a gene that regulates fetal hemoglobin expression, increasing its levels and reducing the symptoms of the diseases.
Read together, the three cases cover the main cargo types: a silencing RNA, a messenger RNA, and a gene-editing payload. The formulation work behind each one is different, and so is the question a preclinical package has to answer.
What Are Some Challenges And Future Directions For Lipid Nanoparticles For Gene Therapy?
Lipid nanoparticles have shown great promise for gene therapy, but they also face some challenges and limitations, such as:
- Optimizing their size, shape, charge and composition to achieve high delivery efficiency and specificity.
- Controlling their biodistribution, pharmacokinetics and pharmacodynamics to avoid off-target effects and toxicity.
- Understanding their interactions with biological fluids, cells and tissues to minimize undesired immune responses and side effects.
- Developing standardized methods for their characterization, formulation and quality control to ensure their safety and efficacy.
- Expanding their applications beyond liver-targeted therapies to other organs and diseases.
To overcome these challenges and advance lipid nanoparticles for gene therapy, more research is needed to:
- Explore new types of lipids and lipid-like materials that can improve the stability, functionality and biocompatibility of lipid nanoparticles.
- Investigate the mechanisms and factors that influence the formation, delivery and release of lipid nanoparticles and their genetic cargo.
- Exploit the biomolecular corona of lipid nanoparticles, which is the layer of proteins and other molecules that adsorb to their surface in biological environments, to modulate their targeting and performance.
- Design smart and responsive lipid nanoparticles that can sense and adapt to different stimuli, such as pH, temperature, enzymes or light.
- Combine lipid nanoparticles with other technologies, such as nanomachines, biosensors or artificial intelligence, to create novel gene therapy platforms.
The biodistribution item on that list is the one that preclinical work can answer first. Where a particle ends up, how long it stays, and which organ takes the dose are measurable questions. Prisys Biotech supports that stage in nonhuman primates: NHP Pharmacology studies underpin the pharmacology read-out, Biodistribution Imaging Service tracks where the dose goes, and LCMS Preclinical Bioanalysis Of LNP-based Gene Therapy Drugs covers the bioanalytical side. Pharmacodynamic (PD) Evaluation Of Gene Therapy answers the separate question of whether the cargo did anything once it arrived.
Lipid nanoparticles are a novel and versatile gene delivery technique for clinical applications. Addressing the challenges above is what turns that versatility into therapies that reach the right tissue at a dose the patient can tolerate.
