In the formulation of mRNA-based vaccines and therapeutics, the lipids used to encapsulate mRNA molecules in lipid nanoparticles (LNPs) for protection from degradation and assurance of appropriate delivery must be both of the highest purity and designed to meet the specific requirements of each nucleotide sequence. Partnering with a lipid supplier that is also a true solution provider is essential to ensure the development of optimal proprietary lipids and the highest-performing nucleotide vaccines and therapeutics.
Many Applications for Lipid Excipients
The evolution of the pharmaceutical industry continues to accelerate. For over 50 years, synthetic small molecules were the only drug substances available. Over the last three decades, biologics — recombinant proteins and antibodies — have been steadily capturing a larger share of the market. In the last decade, significant progress has been made in the area of cell and gene therapies, modalities that proved elusive for decades, as well as other nucleotide-based therapies.
The COVID-19 pandemic rapidly propelled the field of mRNA vaccines and therapeutics forward. Unlike traditional biologics, RNA-based products cause the body to produce active proteins encoded by the RNA sequence, which can overcome the absence of an endogenous protein, in the case of a therapeutic or allow the body to establish an immune response to an appropriate viral (or other) epitope, as in vaccines. As a result, this technology is applicable to a broad array of diseases, disorders, and infectious agents. Indeed, mRNA vaccines are in development to fight influenza, HIV, malaria, and many other harmful viruses, as well as numerous cancers. Some candidates include not only mRNA, but siRNA as well.
There are approximately 1,000 preclinical and clinical studies of RNA therapeutics and vaccines currently underway. Many of these studies were initiated in 2022 alone. This rapid growth of clinical research reflects the potential for RNA and the rising confidence that both emerging and big pharma have in RNA technologies.
Lipids used to encapsulate the RNA molecules in lipid nanoparticles (LNPs) are a crucial component of novel mRNA products. They provide the right cargo for delivery of intact RNA, which is highly unstable in the circulatory system, to the right organ(s) and into target cells.
Enabled by a Wide Range of Functionality
LNPs are generated using several different lipids. Cholesterol is used for stabilization of the nanoparticles. An ionizable cationic lipid, which accounts for approximately 50% of an LNP, is needed to form a complex with the mRNA and to release the payload under specific pH conditions. A pegylated (PEG) lipid, used in small amounts, imparts stability as well as controls the particle size. A phospholipid is also necessary for stabilization.
Formulating Lipid Nanoparticles
Each mRNA molecule has a unique sequence and unique requirements with respect to the optimal lipid nanoparticle formulation that will provide the best protection and optimal delivery. It is therefore necessary to have specialized knowledge and expertise in LNP generation and the interactions of LNPs with RNA and other nucleotide sequences. The nature of the drug substance determines what must be done to make it as stable as possible with respect to the amount and the structure of cationic lipid needed, the ratios of the different lipid components, and other critical factors.
Focus on Ionizable Lipids
The ionizable cationic lipids used to form LNPs are able to complex with mRNA because of their negatively charged backbones. Since they account for half of the lipid content of the LNP, their purity is critical. The manufacture of these specialized lipids, however, can be very difficult. As a result, while a few standard lipids are available on the market, most formulations use proprietary ionizable cationic lipids.
When a contract development and manufacturing organization (CDMO) like Evonik develops a process to produce a proprietary lipid for a customer, a paper exercise is first conducted, in which a team of chemists considers the structure of the lipid and proposes a synthetic route. A key component of the route-scouting activities is considering the availability and quality of key starting materials. The lipid synthesis is then performed in the R&D lab, with a few gram-scale experiments performed to evaluate the yield and purity, by-product formation, and other potential critical issues. If the route looks promising, it is performed at pilot scale (anywhere from a few grams to kilograms, depending on customer requirements). Once a successful pilot run has been completed, the process can be transferred to the manufacturing plant for GMP production.
Running parallel to all these activities is analytical method development to ensure that analytical targets (purity and other specifications) are met. Quality assurance activities are also performed to ensure that GMP regulations are followed. When required by either the customer or the development stage, Evonik performs process validation campaigns.
Overcoming Quality Issues
One of the biggest challenges with the manufacture of ionizable cationic lipids is the reduction of a certain impurity class in the final product. Recently, it has been revealed that aldehyde impurities, which can be derived from a N-oxide degradation, can lead to reductions in the transcription and translation activity of the mRNA cargo and thus reduced efficacy. These by-products can originate from the starting materials, and thus the quality of the starting materials plays a huge role in determining the quality of intermediates and final lipid products. Some by-products form under process conditions, highlighting the importance of the purification step in the manufacturing process. Chromatography is widely used for the purification of ionizable lipids.
For lipid purification, extensive experience and expertise in chromatographic purification ensure that such problematic impurities are removed. Indeed, the approach at Evonik is to start by screening different mobile and stationary phases and applying chromatographic theory to deliver best-in-class processes to our customers as early as possible in the development process.
Scaling
Scaling of processes for the production of lipids used for formulation with LNPs typically depends on the type of lipid and the end-use application. Evonik has the capability to produce quantities ranging from tens of grams to hundreds of kilos. As processes move from the lab to manufacturing scale, some challenges inevitably arise, which is why performing lab- and pilot-scale tests is so important.
Evonik takes a holistic view of process design and development. Using a quality-by-design (QbD) approach during process development helps to ensure comprehensive understanding of the design space and successful scale-up. QbD is particularly valuable for chromatography process development, as it is an efficient way to explore mechanistic models and facilitate smooth scale-up. With this approach, Evonik is able to anticipate potential challenges and even impurities that might be formed when larger quantities of starting materials are used in larger-scale reactions and have a strategy already in place to manage them.
Long-Term Lipid Development and Manufacturing at Evonik
Evonik has decades of experience in process development and optimization for APIs, as well as purification, isolation, and backward integration. Our scientists are well-versed in developing and implementing complicated synthetic routes and handling various different reaction conditions and purification (chromatographic separation) procedures. This expertise in manufacturing APIs is directly transferrable to lipid manufacturing.
For more than 30 years, Evonik has been offering liposome and LNP formulation development and manufacturing services and has also produced PEGs for many years, developing comprehensive understanding of lipid requirements. All this expertise is now being applied to the development and production of lipids specifically for use in LNP formulations.
Differentiated by Plug-and-Play Services
The lipid-related services offered by Evonik cover the range from lab scale to commercial production, including all ancillary services, such as analytical method development; in-house analytical testing; regulatory support, including preparation and filing of the drug master file; and ongoing assistance from our in-house process engineering department.
Underlying all of these activities is a strong emphasis on achieving the highest levels of purity for all lipid products. That is made possible by our deep experience and strong R&D capabilities. Furthermore, Evonik not only produces custom lipids; it also supplies a non-animal-derived cholesterol (PhytoChol®) for use in LNPs. In the past, most cholesterol products on the market were animal-derived, which can suffer from batch variation, purity, and quality issues.
Customers can benefit from partnering with Evonik at any stage of their development projects. We can perform route scouting, initial lab-scale process development, transfer to the pilot plant in a range of scales for further optimization, and of course commercial production. All these services are pursued with a quality-driven approach that enables streamlined scaling. Customers also benefit from the experience that Evonik has with many different types of lipids, which facilitates innovative and flexible thinking. Combined, these attributes make Evonik much more than a lipid supplier; we are a fully integrated solutions provider.
It is also worth noting that — separate from its support of customers looking for LNPs — Evonik is developing alternative delivery vehicles for nucleic acid active ingredients. Charge-altering releasable transporters (CARTs) are polymeric delivery vehicles initially developed by researchers at Stanford University. CARTs are oligomers of 10–20 repeating monomer units consisting of polycarbonate and poly(amino acid) segments. They are an exciting example of the next generation of delivery solutions for mRNA and other nucleic acids.
New Lipid Facilities Under Construction
To better support customers advancing RNA therapies formulated as LNPs, Evonik is expanding its lipid production capabilities. Beginning early in 2023, additional lipid development and manufacturing services will come onstream in Hanau, Germany. In 2025, an additional manufacturing plant at the Tippecanoe site in Indiana will come online.
