4 Delivery Science Lessons For RNA Developers

By Sheryene Tejeda, MD, Ph.D., Medicinal Technologies

RNA therapeutics now include approved small interfering RNA (siRNA), antisense oligonucleotide (ASO), and messenger RNA (mRNA) medicines, yet RNA remains chemically and physically vulnerable, and mRNA most of all. Enzymes, water, heat, oxidation, and mechanical stress can each degrade these molecules, and any of those threats can surface between the synthesis suite and the clinic.

My work has centered on biopharmaceutical delivery systems designed to protect sensitive biologic cargo. Having led FDA engagement and manufacturing partnerships, I have found that many of the problems RNA teams face are not new. Delivery scientists have spent decades learning how cargo degrades, why lots drift apart, and when regulators expect to see the evidence.

What follows draws on published science, current guidance, and my own perspective, which I identify as such. Four lessons carry over most directly: understand how the cargo fails, layer its protection, define consistency before scale-up forces the question, and begin regulatory planning while the process is still flexible.

Lesson 1: Understand How The Cargo Fails

Every protection strategy begins with an honest map of degradation pathways. For mRNA, hydrolysis is the dominant chemical threat. The 2'-hydroxyl group on each ribose can attack the adjacent phosphodiester bond and break the strand, a reaction that alkaline pH and thermal stress accelerate.¹ A review of the first mRNA-lipid nanoparticle (LNP) COVID-19 vaccines identified mRNA hydrolysis as the determining factor in their instability, which helps explain the ultra-cold storage those products initially required.² Published descriptions of the two vaccines report storage at −60 °C to −80 °C for BNT162b2 and −15 °C to −20 °C for mRNA-1273.³

Oxidation is the second pathway, and it can originate in the delivery vehicle itself. Researchers studying mRNA-LNP formulations found that oxidation and subsequent hydrolysis of the ionizable lipid's tertiary amine generated electrophilic impurities that formed covalent adducts with mRNA. Those modifications rendered the mRNA untranslatable, and traditional purity methods typically failed to detect them.⁴ Physical instability is a third threat. Mechanical stress such as shaking or dropping vials can disintegrate mRNA-LNPs, and among in-use stresses, mechanical shear has caused immediate loss of mRNA integrity and aggregation.¹

The practical response is a forced-degradation program, started early, that deliberately stresses pH, temperature, light, oxidants, freeze-thaw cycles, and agitation. Its results should confirm that your analytical methods are genuinely stability-indicating. Raw-material quality belongs in the same plan, because trace metals can catalyze base oxidation,¹ and lipid impurities can inactivate cargo.⁴ The authors of one stability review argue that a test for lipid-mRNA adducts should now be part of every stability assessment,¹ and I consider that sound advice for any lipid-based program.

Lesson 2: Protection Works Best In Layers

The approved RNA products distribute protection across several tactics. Chemistry, encapsulation, and targeting each contribute, and I would argue that the most durable programs combine them.

Chemical modification is the first layer. A 2005 study showed that nucleoside modification suppresses recognition of RNA by Toll-like receptors,⁵ and N1-methylpseudouridine later became a key feature of the COVID-19 mRNA vaccines.⁶ For oligonucleotides, combinations of sugar, backbone, nucleobase, and terminal modifications have repeatedly turned small chemical changes into large clinical gains.⁷ In one well-documented series on N-acetylgalactosamine (GalNAc)-conjugated siRNA that carried 2'-O-methyl and 2'-fluoro sugar modifications, adding phosphorothioate linkages for exonuclease protection improved in vivo potency in mice roughly fivefold.⁸

Encapsulation is the second layer. LNPs typically pair an ionizable lipid with a phospholipid, cholesterol, and a polyethylene glycol (PEG)-lipid, and encapsulation shields mRNA from nuclease degradation.³ Patisiran, which the FDA approved in August 2018 as the first siRNA therapeutic, encases its siRNA in an LNP to deliver it to the liver.⁹

Targeting is the third. Triantennary GalNAc ligands bind the asialoglycoprotein receptor (ASGPR) on hepatocytes, and in mice this design supported subcutaneous dosing and sustained gene silencing.⁸ Givosiran, which the FDA approved in November 2019 for acute hepatic porphyria,¹⁰ carries a ligand with three GalNAc residues covalently linked to its siRNA; the ligand directs the drug to hepatocytes.¹¹

Each program should decide early which layer carries the most protective burden and document why. In my experience, teams that treat the delivery system as an afterthought to sequence design discover late that their formulation, not their sequence, limits shelf life. Each protective component also becomes a quality attribute that you must control, so every layer you add should earn its place.

Lesson 3: Define Consistency Before You Need It

Lot-to-lot consistency is where delivery science and quality systems meet. ICH Q8(R2) frames the principle plainly: quality cannot be tested into products and should be built in by design.¹² Quality by design (QbD) starts with a quality target product profile and works backward to the critical quality attributes (CQAs), the physical, chemical, biological, or microbiological properties that should stay within an appropriate limit, range, or distribution to ensure the desired product quality.¹²

For mRNA-LNP products, the European Medicines Agency (EMA) has begun to spell out what those attributes look like. Its draft guideline on mRNA vaccine quality expects release control of at least identity, 5' capping efficiency, poly(A) tail presence and length, mRNA content, and mRNA integrity for the active substance. For the finished product, it names LNP size and polydispersity index (PDI), encapsulation efficiency, individual lipid content, and impurities including RNA-lipid adducts and lipid degradation products. It also expects control of double-stranded RNA (dsRNA).¹³ Although the draft addresses vaccines against infectious diseases, it notes that relevant parts may apply to other mRNA products,¹³ and I would treat it as one of the most detailed public maps currently available.

For synthetic oligonucleotides, EMA released a separate draft guideline for consultation in July 2024. It covers development, manufacture, and control, including conjugates such as GalNAc, and it explicitly excludes mRNA.¹⁴ Public consultation on both EMA documents has closed, yet neither had been finalized at the time of writing.^13,14

Manufacturing changes test consistency hardest. ICH Q5E defines comparability as highly similar quality attributes before and after a process change, with no adverse impact on safety or efficacy, and it allows that conclusion to rest on quality data alone when the evidence is strong enough.¹⁵ Its formal scope covers proteins and polypeptides,¹⁵ so applying it to RNA products is an extrapolation. Even so, its logic of pre- and post-change analytical comparison is, in my view, the right discipline for any complex biologic.

Before the first scale-up or technology transfer, lock a characterization panel. Retain reference material from early lots so you can compare later lots side by side. ICH Q9(R1) risk tools¹⁶ can rank which CQAs are most sensitive to mixing conditions, lipid sourcing, and fill/finish; give your manufacturing partner those rankings in writing. When I have managed transfers between partners, the batch record and specification mattered, yet the greatest value came from a shared, written understanding of which attributes the product could not afford to lose. ICH Q10 describes a model for an effective pharmaceutical quality system that can carry that knowledge from one site to the next.¹⁷

Lesson 4: Build Regulatory Strategy In From The Start

Stability expectations are in transition. In April 2025, ICH released a consolidated Q1 draft for consultation that includes a new annex on advanced therapy medicinal products.¹⁸ The FDA published it as draft guidance in June 2025, describing a single document that consolidates Q1A(R2), Q1B, Q1C, Q1D, Q1E, and Q5C and adds recommendations for vaccines and other complex biological products.¹⁹ Its scope names chemically synthesized oligonucleotides among the synthetic drug substances it covers.¹⁹ At the time of writing, the revision had not yet reached Step 4. The ICH work plan targets adoption in November 2026,²⁰ so teams should confirm final status before relying on any specific provision.

Oligonucleotide developers will also find useful context in the FDA's December 2021 draft guidance on chemistry, manufacturing, and controls (CMC) for individualized ASO IND applications, which remains a draft.²¹ I found no FDA guidance devoted specifically to mRNA CMC, which makes early dialogue with the agency more valuable. In July 2026, the FDA also released a strategy document describing its actions and plans to help drug and biologic programs on accelerated clinical timelines reach CMC readiness.²²

In August 2026, the FDA's Center for Drug Evaluation and Research (CDER) and Center for Biologics Evaluation and Research (CBER) finalized joint guidance on formal meetings with sponsors.²³ That guidance positions Initial Targeted Engagement for Regulatory Advice on CDER and CBER ProducTs (INTERACT) meetings as a route to resolve novel issues that could otherwise delay first-in-human testing. Eligible topics include CMC issues and the testing strategies needed to support first-in-human safety. INTERACT meetings are typically held before a pre-IND meeting and are not appropriate once a sponsor has held a pre-IND meeting or filed an IND. The guidance sets target scheduling of 75 days from request for INTERACT and 60 days for Type B meetings, which include pre-IND meetings.²³

Map your CMC uncertainties against these meeting types. If your delivery system or analytical strategy has no regulatory precedent, an INTERACT meeting may be the right first conversation. Otherwise, arrive at the pre-IND meeting with forced-degradation data, a draft CQA list, and a stability protocol already in hand. Specific questions grounded in data tend to earn specific answers, while open-ended requests rarely do.

Acting On These Lessons Now

Teams advancing RNA programs toward the clinic can act on several points now. Characterize degradation pathways, including lipid-derived adducts, before formulation decisions harden. Layer chemistry, encapsulation, and targeting deliberately, and document the rationale for each. Define CQAs, retain reference material, and rank risks before the first technology transfer. Monitor the ICH Q1 revision and the EMA drafts closely. Finally, use INTERACT or pre-IND meetings to test your CMC assumptions while change remains inexpensive.

Delivery science has learned, often at real cost, that fragile cargo rewards early discipline. RNA developers have the advantage of inheriting those lessons rather than relearning them.

References

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About The Author:

Sheryene Tejeda, MD, Ph.D., is a physician-scientist and the founder, CEO, and lead medical scientist of Medicinal Technologies. Formerly in private practice, she has developed medications across reproductive, hormonal, metabolic, cardiovascular, ocular, and musculoskeletal health, and has published peer-reviewed research across multiple indications. She also founded the Tejeda Foundation, a nonprofit dedicated to low-cost healthcare. She speaks on these conditions and their treatment, women's and men's health, healthcare access, and the science behind new medications.