Why this matters. Overcoming the liver barrier is the next frontier for genetic medicines. While first-generation LNPs revolutionized siRNA and mRNA delivery, most remain confined to the liver – limiting access to tumors, immune compartments, and stem cell niches.

The bottleneck enabling next generation nucleic acid therapeutics

For more than a decade, the story of lipid nanoparticles (LNPs) has revolved around the liver. The LNP composition developed for the first-ever siRNA drug Onpattro® has been tuned to favor hepatic uptake through ApoE binding and LDL receptor interactions. That design made sense: the liver was the origin of the disease (hATTR amyloidosis). But the same traits that enabled success in the liver also block access to almost every other tissue.

When ~90 % of a systemically injected LNP dose is eliminated via the liver, extrahepatic nucleic acid delivery becomes a challenge, and new genetic medicines remain out of reach. To enable new therapies, scientists must answer a simple but urgent question: Can we prevent hepatic uptake and extend the blood circulation of LNPs, long enough to reach tissues beyond the liver?

Figure 1 - LNP: Delivery Beyond the Liver

From surface modifications to differentiated morphologies: Strategies to extend blood circulation

Conventional Onpattro-like LNPs follow a well-established recipe:

≈50mol% ionizable lipid, 10mol% phospholipid, 38.5mol% cholesterol, 1.5mol% PEG-lipid.

Structurally, these LNPs contain a lipophilic core wrapped (mostly) in a lipid monolayer. This design supports efficient RNA encapsulation but the inclusion of PEG-lipids with short C14 lipid anchors (e.g., PEG-DMG or PEG-DMPE) predisposes the system to rapid opsonization and clearance. LNPs quickly attract Apolipoprotein E (ApoE) from the bloodstream on the LNP surface that targets low-density lipoprotein receptors (LDLR) on hepatocytes.

This design was ideal when the liver was the target (e.g., TTR silencing), but the same features become a bottleneck for other tissues. The limited circulation time, with conventional LNPs clearing from the bloodstreams of mice within 30 minutes, is not enough for effectively delivering nucleic acid payloads to tissues such as the bone marrow, tumors, or lymphoid organs.

Traditional workarounds: The PEG dilemma

To extend the blood circulation of LNPs, researchers have long turned to PEG lipids with C18 anchors, such as PEG-DSG or PEG-DSPE, which decrease the PEG-lipid dissociation from the LNP, thus lowering ApoE binding and extending the systemic circulation time. But this “solution” introduces a new set of problems:

• Uptake & potency trade-off: Persistent PEG shields the LNP surface, reducing cellular uptake and endosomal release.
• Immunogenicity: Persistent PEG can drive hypersensitivity and anti-PEG antibody responses.
• Re-dosing risk: Immune recognition can cap dose intensity and frequency.

This phenomenon is often referred to as the PEG dilemma -  another barrier to expanding LNP-nucleic acid drugs beyond the liver.

Rethinking LNP design: The importance of lipid bilayers

Several groups are exploring LNP charge modulation or ionizable lipid architectures to redirect LNPs beyond the liver. These approaches, however, often trade a change in biodistribution for increased toxicity or complex manufacturability. Rather than adding new components, the rational design to shape LNP morphology can be leveraged to influence the pharmacokinetic profile of LNPs - and in turn, performance.

Clinically approved liposomal anticancer drugs like Myocet (egg phosphatidylcholine / cholesterol) and Marqibo (sphingomyelin / cholesterol) demonstrate that lipid bilayer structures can lead to long circulation times without the need of a C18 PEG-lipid. Bilayer architectures lower the recruitment of opsonins like ApoE and complement proteins reducing hepatic clearance and preserving systemic exposure - without resorting to persistent PEG.

Figure 2 - Comparison between Conventional Lipid Nanoparticles (LNPs) (left) and Next-Generation Liposomal LNP Designs (right), illustrating their respective Protein Corona layers (shown as small surface dots, simplified for clarity).

By applying these structure–function insights to nucleic acid delivery, NanoVation has developed the so called long-circulating LNP (lcLNP™) technology. Raising the ratio of bilayer-forming lipids to ionizable lipids creates a “fried-egg” or “fish-eye” liposomal-like structure: a bilayer shell surrounding a dense lipid core. This morphology isn’t just cosmetic – it imparts new characteristics:

• Reduced non-specific protein adsorption, which otherwise accelerates liver clearance
• Extended circulation time (hours vs. minutes)
• Avoiding reliance on C18 PEG-lipids for increasing systemic circulation
• Enabling  extrahepatic biodistribution (e.g., to the bone marrow, lymphoid organs, and beyond)

Endosomal escape reimagined

How do these liposomal LNP systems still release their RNA cargo efficiently? Cryo-TEM studies suggest a unique pH-triggered mechanism. As the endosomal pH drops, the ionizable lipid becomes protonated (positively charged) and migrates toward the outer bilayer. This migration destabilizes the symmetry between the inner and outer leaflets, driving the core outward. This may increase interactions with the endosomal membrane finally releasing the nucleic acid payload into the cytosol. This process preserves delivery potency without relying on high ionizable-lipid content.

Quality by Design for extrahepatic delivery

As outlined in our previous article on LNP characterization, morphological aspects represent a potential critical quality attribute (pCQA). Formulation teams should integrate morphology and corona analytics within their Quality by Design (QbD) frameworks.

From rational design to therapeutic opportunities

Preclinical PK/BD (pharmacokinetic/biodistribution) studies with lcLNP™ demonstrate that both the LNP carrier as well as the nucleic acid payload circulate in the blood for an extended period allowing a significantly increased accumulation in tissues beyond the liver compared to traditional compositions. The implications are substantial. Expanding the tropism of LNPs can unlock a wide range of non-liver indications, from gene-editing in stem cells to in vivo CAR immunotherapies. Achieving this requires rethinking old assumptions.

The lcLNP™ technology shows that with a differentiated morphology and lipid composition, it is possible to:

• Break free from liver-restricted delivery
• Avoid the PEG dilemma
• Enable safer and tunable delivery platforms.

Extrahepatic delivery is not just a formulation tweak. As the field moves toward tissue-specific applications, morphology-informed design could be the lever that changes what is possible in nucleic acid therapeutics.

Strategic lens: where business meets biology

Differentiated LNP systems, such as the lcLNP™, reframe the value proposition of platform technologies:

• New indications. Stem cell editing, in vivo CAR, cancer vaccines, or immuno-oncology.

• Extended IP space. Architectural patents around lipid compositions and bilayered LNPs.

• Partnership opportunity. New delivery systems open up new therapeutic applications.

• Therapeutic index. Bilayer lipid compositions with increased helper lipid content demonstrate improved safety profiles.

• Synergies with payload. Optimization of the LNP carrier as well as the nucleic acid payload offers opportunities for improved specificity.

LNPs are no longer confined to the liver by viewing extrahepatic delivery as an engineering problem: one solved not by trial-and-error chemistry, but through rational, morphology-guided design. Liposomal-like LNPs, such as lcLNP™, achieve both longer circulation and broader organ access, translating lipid organization into predictable pharmacokinetic behavior. Such rational design principles offer a route to extrahepatic delivery, a milestone that transforms how we think about LNP technologies. The future will demonstrate how far we can go - beyond the liver.

Key takeaways

• Conventional LNPs are liver-tropic due to ApoE/LDLR interactions and short circulation.
• The PEG dilemma extends PK but can trade off potency, safety, and re-dosing.
• Bilayer morphology (e.g., lcLNP™) extends circulation and supports extrahepatic access without persistent PEG.
• Morphology can be used as a design lever within QbD for extrahepatic programs.

Coming in December: The regulatory framework for LNP-nucleic acid therapeutics. Stay tuned!

Download a full article here.

Written by

Dr. Dominik Witzigmann 

Dominik is an entrepreneurial scientist with deep expertise in nanomedicines and nucleic acid delivery. In 2024, he was named Highly Cited Researcher, recognizing him among the world’s most influential researchers in the field. Dominik obtained his Ph.D. in Pharmaceutical Technology from the University of Basel in Switzerland, and held research positions at leading institutions including University College London (safety/tox), German Cancer Research Center (RNAi & cancer), University of Basel (targeted nanomedicines & DNA delivery) and the University of Zurich (mRNA-based genome editing). To focus on extrahepatic RNA delivery, he later joined the team of Prof. Pieter Cullis at the University of British Columbia. Dominik has held leadership roles in Canada’s NanoMedicines Innovation Network (NMIN) and served on the Board of the CRS Gene Delivery and Genome Editing Focus Group. To translate next-generation LNP technologies into the clinic, Dominik co-founded and leads the LNP-nucleic acid company NanoVation Therapeutics. 

Dr. Jayesh Kulkarni

Dr. Kulkarni obtained his PhD from the University of British Columbia and has over 15 years experience in the nanoparticle drug delivery field. He has published over 40 peer-reviewed articles and is a co-inventor on numerous patents. Dr. Kulkarni’s research has focused on the role of the various lipid components in LNP and the biophysics that governs particle formation. His work has contributed to clinical translation, including scale-up and manufacturing of LNP systems in accordance with GLP and GMP regulations. Dr. Kulkarni is a leader in the design and development of lipid nanoparticle (LNP) formulations of small molecule and nucleic acid therapeutics. He currently serves as the Chief Scientific Officer of NanoVation Therapeutics, an LNP-RNA formulation developer.

Nicola Pett, MSc

Nicola holds a BSc in Biomedical Science from the University of Queensland, Australia, where she first developed an interest in translational research while studying cancer immunotherapy. After relocating to Canada, she worked as a research technician at the University of Calgary, investigating the gut microbiome in inflammatory and metabolic diseases, including IBD, cancer, and diabetes. She later earned an MSc in Microbiology and Immunology from the University of British Columbia, focusing on host–microbiome interactions. At NanoVation Therapeutics™, her work bridges immunology and RNA delivery technologies to better understand how immune environments shape therapeutic outcomes.

Dr. Marija Petrovic 

Marija is a pharmacist with a PhD in Biopharmacy from the University of Geneva, and a cancer research (ISREC)–trained professional through EPFL, with over seven years of experience in nanomedicine. During her PhD, she worked on miRNA and STING ligand nanocomplexes for cancer immunotherapy, gaining deep expertise in nanoparticle characterization and translational workflows. Certified by the EU-NCL in nanobiotechnology and awarded by Innosuisse (Swiss Innovation Agency) with two prizes (jury and public) for the best life science project, she also earned support from FONGIT, Geneva’s leading deep-tech incubator. As the founder of NanoSphere and an active contributor to the Controlled Release Society (Communication Chair for the Gene Delivery and Editing Group (GDGE), and Industry representative at Nanomedicine and Nanoscale Delivery (NND)), Marija focuses on making next-gen medicine scientific advances more visible, understandable, and useful to the communities that can turn them into impact.