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Release date:2024/1/19 11:05:01

Katalin Karikó and Drew Weissman were jointly awarded the 2023 Nobel Prize in Physiology or Medicine for their work on mRNA vaccines. However, few people are aware of the unsung heroes behind mRNA vaccines—the lipid nanoparticles (LNPs) that play a crucial role in encapsulating and delivering mRNA safely and effectively into the cells of the body.

The use of mRNA-LNP for the treatment of cancer patients has been an ongoing research area that started before these versatile nanoparticles were successfully used as COVID-19 vaccines. Although there are no clinically marketed mRNA-LNP-based tumor vaccines or direct intra-tumor injections encoding pro-inflammatory cytokines, many pharmaceutical companies have already initiated the development of mRNA-LNP-related drugs in the field of oncology and a significant number of drugs have already entered clinical trials.

Components Of LNPs

The LNP technology can be considered as the most advanced non-viral gene delivery system in clinical practice. The approval of Onpattro® by the US FDA in 2018 marked a significant milestone for this technology.

LNP is a nanoscale particle system composed of multiple components, used for efficient delivery of nucleic acid drugs (such as mRNA, siRNA, or DNA) into cells. Here are the main components of LNPs:

Ionizable Cationic Lipids: They serve two key functions including facilitating nucleic acid encapsulation in LNPs and mediating endosomal membrane disruption to enable nucleic acid release to the cytosol.

PEGylated lipids: PEGylated lipids are another important component of LNP and serve multiple functions: 1) They prevent the aggregation of nanoparticles during storage and in the bloodstream; 2) Their content influences the particle size of LNP; 3) They prolong the circulation time in the body; 4) They enable surface functionalization, allowing for conjugation with ligands or other molecules.

Cholesterol: Cholesterol plays a role in enhancing the stability of LNP's structure. It can be inserted into the lipid bilayer, increasing membrane rigidity and stability while regulating membrane fluidity.

Saturated Phospholipids: Saturated phospholipids, usually phosphatidylcholine (DSPC), have good structural stability and biocompatibility, which helps maintain the integrity and structure of LNP.

LNP-COMPONENTS

Figure 1. Simplistic illustration of LNP and its individual components [2]

These components work together to form a stable LNP structure and provide functions such as encapsulation, protection, and targeted delivery of drugs.

mRNA-LNP Targeting Strategies

mRNA LNPs for systemic delivery to tissues and tumors could employ passive and active targeting strategies.

mRNA-LNP-targeting-strategy

Figure 2. mRNA-LNP targeting strategies [1]

Passive targeting takes advantage of the natural properties of tissues or tumors, such as the enhanced permeability and retention effect, to achieve accumulation without the need for specific surface modifications. This strategy is relatively simpler and can be effective in certain situations, especially when targeting accessible tumors or non-malignant tissues.

On the other hand, active targeting involves surface modifications using targeting ligands or antibodies, allowing for more precise delivery to specific cell types. This strategy offers the potential for enhanced selectivity and improved uptake by target cells. However, it requires the identification and validation of appropriate targeting ligands, which can be a complex and time-consuming process.

The selection of the targeting strategy should consider the specific application needs, the characteristics of the target tissue, and the balance between simplicity and specificity. In some cases, a combination of both passive and active targeting strategies may be employed to maximize the therapeutic efficacy and minimize off-target effects.

In general, passive and active targeting strategies each have their advantages and challenges. The choice of strategy depends on specific application requirements and the characteristics of the target tissue.

Clinical Applications of mRNA-LNPs

Ongoing oncology trials of mRNA–LNP-based therapies primarily focus on the local administration of cancer vaccines or intratumoral expression of immunostimulatory cytokine mixtures combined with checkpoint inhibitors (ICIs). Currently, over ten mRNA-LNP-based therapies are being tested in clinical trials, covering a range of cancer indications.

mRNA-LNPs-in-clinical-trails
Figure 3. Selected oncology clinical trials testing mRNA–LNPs [1]

Currently, mRNA-LNP therapies in clinical development primarily focus on cancer vaccines that can simultaneously encode multiple antigens. The development of such vaccines benefits from three major advantages of the mRNA therapeutic platform: its modularity, ability to incorporate numerous payloads and manufacturing efficiency. Given that most mRNA payloads differ only in nucleotide sequences, this enables rapid customization, offering new possibilities for personalized treatment in oncology.

In addition to cancer vaccines, other explorations of mRNA-LNP in the field of cancer treatment include the use of pro-inflammatory cytokine cocktails, bispecific antibodies targeting specific immune stimulatory factors or tumor targets, expression of chimeric antigen receptors (CARs) in T cells from solid tumor patients, and expression of epigenetic modifiers. To ensure the accuracy and practicality of research findings, future studies need to explore the differences between animal models and human patients. Additionally, optimizing the translational effectiveness of mRNA-LNP research across different species is also important.

Challenges and Prospects

To translate the preclinical research achievements of mRNA-LNP into clinical applications, several challenges need to be addressed.

1. mRNA-LNP instability: mRNA-LNP is unstable at refrigerated temperatures, mainly due to the inherent instability of mRNA payloads rather than the instability of the LNP carrier itself.
2. Inflammatory response: LNPs themselves can increase cytokine levels in the host, leading to inflammation. This property can be beneficial for immunotherapy but may also cause unexpected pseudo-allergic reactions.
3. Presence of anti-PEG antibodies: PEG is a common component of LNPs, and in some patients receiving mRNA-LNP vaccines, anti-PEG antibodies have been observed. These antibodies may lead to the rapid clearance of mRNA-LNP in the body, thereby affecting efficacy. Researchers need to find alternative substances to PEG.
4. Clearance issues of mRNA-LNP: Some ionizable lipids in RNA-LNPs have a long half-life in the body, which may require special methods to improve their clearance rate and reduce potential adverse effects.
5. Specificity and off-target expression: The cell specificity of mRNA-LNPs still needs to be improved to reduce off-target expression.
6. Manufacturing complexity: The complexity of manufacturing processes is one of the bottlenecks hindering the clinical translation of active targeting strategies for mRNA-LNP. Therefore, new methods are needed to reduce manufacturing complexity and make it more cost-effective and feasible.

These challenges highlight the need for further research and resolution of issues in the practical application of mRNA-LNP therapy. Additionally, another emerging trend in the field of oncology is the use of gene editing tools such as CRISPR-Cas9 to apply mRNA-LNP for in vivo genome editing in target cells. The advantage of this approach is that the genome editing proteins encoded by mRNA can achieve transient expression, thereby reducing the risk of adverse events.

Although CRISPR-Cas9 holds potential in cancer research, its targeting ability relies on the capability to precisely deliver payloads to target cells. Therefore, future development in this field may focus on improving the cell-specific expression capability of mRNA-LNP to achieve more precise drug delivery and reduce off-target expression.

It is worth mentioning that to meet the industry's demand for LNP formulation development, Biopharma PEG provides customers with high-purity cholesterol (plant-derived), PEG lipids, DSPE, and other materials to assist in the synthesis of LNPs.

Conclusion

mRNA-LNP therapy has demonstrated tremendous potential in treating various malignant tumors. Its unique characteristics, such as the ability to induce immune responses and the potential for customized individualized treatment approaches, make it a popular choice in cancer therapy. However, to translate these preclinical research achievements into clinical applications, multiple challenges at biological, technical, and manufacturing levels need to be overcome. Importantly, addressing these challenges requires multidisciplinary collaboration, including close cooperation among researchers, clinicians, and industry partners. With continued advancements in this field, mRNA-LNP-based therapies will profoundly transform the landscape of cancer treatment, offering better prognoses for patients.

References:
[1] Kon E, Ad-El N, Hazan-Halevy I, Stotsky-Oterin L, Peer D. Targeting cancer with mRNA-lipid nanoparticles: key considerations and future prospects. Nat Rev Clin Oncol. 2023;20(11):739-754. doi:10.1038/s41571-023-00811-9
[2] Hald Albertsen C, Kulkarni JA, Witzigmann D, Lind M, Petersson K, Simonsen JB. The role of lipid components in lipid nanoparticles for vaccines and gene therapy. Adv Drug Deliv Rev. 2022 Sep;188:114416. doi: 10.1016/j.addr.2022.114416. Epub 2022 Jul 3. PMID: 35787388; PMCID: PMC9250827.

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