Engineers have devised a new approach to enhance the delivery of mRNA, creating the ideal ‘formula’ for ionizable lipids—essential components in lipid nanoparticles (LNPs), which are crucial for the COVID-19 vaccines and other novel therapies. This method resembles the creative process of crafting a culinary dish and could result in mRNA vaccines and therapies that are both safer and more effective.
Engineers at Penn have developed a fresh strategy to enhance mRNA delivery by creating an optimal “formula” for ionizable lipids—critical components in lipid nanoparticles (LNPs), the building blocks of COVID-19 vaccines and other groundbreaking therapies. This technique, discussed in Nature Biomedical Engineering, reflects the iterative nature of cooking and has the potential to lead to mRNA vaccines and treatments that are safer and more effective.
Much like how chefs refine a dish by experimenting with different flavors and textures, the research team employed an iterative approach, testing different variations to find the best configuration for ionizable lipids. The structure of these lipids significantly affects the effectiveness of LNPs in delivering their contents, which is crucial for the advancement of mRNA therapies aimed at vaccines and gene editing.
An Innovative Step in LNP Development
Nanoparticles have revolutionized the delivery of mRNA vaccines and therapies by enabling safe movement through the body, targeting specific cells, and efficiently releasing their contents. Without this protective delivery method, RNA is delicate and would easily break down before reaching its destination.
Central to these nanoparticles are ionizable lipids, unique molecules capable of shifting between charged and neutral states depending on their environment. This transformation is vital for the nanoparticle’s journey: in the bloodstream, these lipids remain neutral to avoid toxicity but turn positively charged upon entering target cells, instigating the release of the mRNA content.
Under the leadership of Michael J. Mitchell, an Associate Professor in Bioengineering, the team enhanced this delivery method by refining the structural properties of ionizable lipids. By moving beyond traditional approaches that often require compromises between speed and precision, the researchers formulated a systematic, “directed chemical evolution” method. Over five cycles of refinement, they produced numerous high-performing, biodegradable lipids—some even exceeding existing industry benchmarks.
The Key Ingredient: Directed Chemical Evolution
To create safer and more effective ionizable lipids, the Penn Engineers utilized an innovative strategy combining two established methodologies: medicinal chemistry—which is a slow, meticulous process involving stepwise molecule design—and combinatorial chemistry, which allows for rapid generation of various molecules through straightforward reactions. Medicinal chemistry offers high precision but lacks speed, while combinatorial chemistry achieves the opposite.
“We believed it might be possible to get the best of both approaches,” explains Xuexiang Han, the first author of the study and a recent postdoctoral fellow in the Mitchell Lab. “We aimed for both high speed and high precision, but we needed to break away from conventional boundaries in our field.”
By adapting the concept of directed evolution, a technique prevalent in both chemistry and biology that imitates natural selection, the researchers merged careful selection with rapid production to perfect their lipid “formula.”
The process initiates with creating a varied array of molecules, which are then evaluated for their ability to successfully deliver mRNA. The top-performing lipids serve as the foundation for generating subsequent rounds of molecular variants until only the best candidates remain.
A Game-Changing Component: A3 Coupling
A vital element contributing to the improved ionizable lipids is A3 coupling, a three-component reaction named after its chemical constituents: an amine, an aldehyde, and an alkyne.
This reaction, which has never been previously used to synthesize ionizable lipids for LNPs, relies on affordable, readily accessible ingredients and generates only water as a byproduct, making it both environmentally friendly and cost-effective for generating the necessary varieties of ionizable lipids for directed evolution quickly.
“We discovered that the A3 coupling reaction wasn’t just efficient; it was also adaptable enough for precise adjustments to the lipids’ molecular structures,” states Mitchell. This adaptability was crucial for optimizing the properties of ionizable lipids to ensure the safe and effective delivery of mRNA.
The Importance of This Development
This new technique for designing ionizable lipids is believed to have significant implications for mRNA-based vaccines and therapies, which are expected to address a wide range of conditions, from genetic diseases to infectious ailments.
In this research, the improved lipids enhanced mRNA delivery in preclinical trials targeting two high-priority applications: gene editing for hereditary amyloidosis, a rare condition characterized by abnormal protein deposits in the body, and optimizing the delivery of the COVID-19 mRNA vaccine. In both cases, the engineered lipids demonstrated superior performance compared to conventional industry-standard lipids.
Beyond these specific instances, this approach could expedite the overall development of mRNA therapies. While traditional methods can take years to produce an effective lipid, the researchers’ directed evolution technique could shrink this timeline to mere months or even weeks.
“We hope that this will speed up the pipeline for mRNA treatments and vaccines, delivering new solutions to patients faster than ever before,” adds Mitchell.
A New Era for mRNA Delivery
LNPs offer a reliable and adaptable method for genetic material delivery, but their effectiveness relies heavily on the characteristics of the ionizable lipids involved. The iterative design process from Penn Engineers empowers researchers to enhance these lipids with remarkable speed and accuracy, paving the way for the next generation of mRNA therapies.
With this groundbreaking recipe for LNPs, Penn Engineers have made significant strides in furthering mRNA technology, creating hope for a quicker and more efficient route to transformative treatments.
This research was conducted at the University of Pennsylvania’s School of Engineering and Applied Science, supported by various grants, including a U.S. National Institutes of Health (NIH) Director’s New Innovator Award (DP2 TR002776), a Burroughs Wellcome Fund Career Award at the Scientific Interface (CASI), a US National Science Foundation CAREER Award (CBET-2145491), an American Cancer Society Research Scholar Grant (RSG-22-122-01-ET), and iECURE.
Other co-authors include Kelsey L. Swingle, Junchao Xu, Ningqiang Gong, Lulu Xue, Giangqiang Shi, and Il-Chul Yoon from Penn Engineering; Rohan Palanki from Penn Medicine and Penn Engineering; and Mohamad-Gabriel Alameh, Rakan El-Mayta, Garima Dwivedi, James M. Wilson, Drew Weissman from Penn Medicine; along with Claude C. Warzecha from Gemma Therapeutics.
