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SPECIALTY TOPICS · GUIDE

Investigational Gene and RNA Applications

What investigational means for gene and RNA therapies, with worked examples from published early trials, what a registry record can and cannot show, and the warning signs of unregulated offers.

Content last updated . This page has not been medically reviewed.

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Quick answer
Investigational means a treatment is still being tested and has not been approved for the use being studied. For gene and RNA medicines, early human studies mostly ask whether a method is safe and whether it changes a lab measure, not whether people live better or longer. This page explains the status, walks through two published examples, and lists warning signs of unregulated offers.

Example 1: in vivo gene editing in a small phase 1 study

What: NTLA-2001, a gene-editing therapy for transthyretin (ATTR) amyloidosis, made of messenger RNA for a gene-editing enzyme and a guide RNA, carried in a lipid nanoparticle. [3]

Who and how: six patients with hereditary ATTR amyloidosis with nerve damage, in the first two dose groups of an ongoing phase 1 study, after preclinical work in cells and animals. [3]

What was measured: safety over 28 days and the level of transthyretin protein in blood. At day 28 the mean reduction was 52% in one group and 87% in the other, and adverse events in that period were few and mild. [3]

What it does not show: whether patients feel or live better, whether the effect lasts, or what happens beyond 28 days. The report states that the study was funded by the companies developing the product. [3] Label: investigational, promising but limited. The same technology, delivered with a lipid carrier, is explained in Lipid Nanoparticles and Non-Viral Delivery and Gene Editing and CRISPR Explained.

Example 2: a one-patient customized therapy

A 2025 report describes a newborn diagnosed with severe carbamoyl-phosphate synthetase 1 deficiency, for whom a customized base-editing therapy in a lipid nanoparticle was developed; regulatory approval for that single use was obtained, and the child received two infusions at about 7 and 8 months. [4] In the 7 weeks after the first infusion, the infant tolerated more dietary protein and needed a reduced dose of a nitrogen-scavenger medication, with no serious adverse events, and the authors say longer follow-up is needed to assess safety and efficacy. [4] This is one patient, with no comparison group and short follow-up; the report states funding from the National Institutes of Health and others. [4] Label: insufficient evidence about general benefit. It does show that tailored editing is technically possible; it does not show that it can be offered widely. See Base Editing and Prime Editing.

Where research is still early

  • Reaching tissues beyond the liver. Reviews describe LNP engineering for lungs, spleen, brain and other organs, and list species differences, immune reactions and manufacturing as bottlenecks. [5] No human results are described in that abstract.
  • The brain. A 2021 review said several strategies for improving AAV delivery to the brain were tested only in preclinical models, none in clinical trials at that time. [6] Check newer sources for changes.
  • Immune reactions to vectors. For hemophilia gene therapy, strategies to overcome AAV immune responses are encouraging but more efficient approaches are needed. [7]
  • Non-viral carriers other than LNPs. Polymer particles and cell-derived vesicles are described as having toxicity, reproducibility and manufacturing challenges. [8]

Delayed effects and follow-up

The FDA notes that gene therapy products may produce long-lasting changes, so study participants may face an increased risk of unpredictable delayed adverse events, which is why long-term follow-up studies are recommended to sponsors. [9] See Off-Target Effects, Durability and Long-Term Monitoring.

Frequently asked questions

Does "in a clinical trial" mean a treatment is proven?

No. A registry record shows a study exists, and a phase 1 record is about early safety and dose questions. [2] Evidence comes from published results. See the linked guide on registered trials.

Is gene editing available to the public?

Apart from FDA-listed approved products for specific diseases, gene editing in the examples here was given in studies or under a single-patient regulatory pathway. [3][4] Approved products are listed on the approved-therapies page.

What does a drop in a blood protein prove?

It is a biomarker change. In the NTLA-2001 report, the blood transthyretin protein level fell at day 28, but the short report did not show clinical benefit. [3] See Surrogate vs Patient-Important Outcomes.

How can I spot an unregulated therapy?

The EMA says unregulated advanced therapies are often sold online or through social media as a last hope, and lists warning signs such as a product called experimental but used outside an authorised trial. [10]

More details: evidence, limits and cautions

The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.

How to read the evidence labels

Labels used on this page: investigational, promising but limited, insufficient evidence, preclinical (cells/animals only), marketing claim. See How We Label Evidence in Specialty Topics.

What investigational means in the United States

The FDA states that human studies of a gene therapy need an investigational new drug (IND) application before they start in the United States, and that marketing a gene therapy requires approval of a biologics license application. [1] Until then, the product is not approved for sale for that use. For products that are approved, see Approved Gene and RNA Therapies.

Registry records

Trial registries such as ClinicalTrials.gov show that a study exists, its phase and its status. They do not show that the treatment works. For example, the registry record for the NTLA-2001 study lists it as a phase 1 study with the status COMPLETED, verified January 2026. [2] A registered trial proves nothing about effectiveness, and a published result must be read for what was actually measured. See Registered Trials vs Published Results and Clinical-Trial Phases Explained.

Proper evidence not found: a verified, current list of ongoing gene and RNA therapy trials. The ClinicalTrials.gov record above was read, but no search of the whole registry was completed, so no counts or lists are given here.

Warning signs of unregulated offers
The European Medicines Agency (EMA) warns that unregulated advanced therapies may put patients at risk of serious side effects without proven benefits, and that they are often sold online or through social media as a last hope. [10] Its warning signs include providers who call a product experimental but use it outside an authorised clinical trial, providers who cannot confirm that the product has been approved, and claims of benefits that exceed those of approved treatments without supporting medical literature. [10] The EMA advises checking with your national competent authority and seeking a second opinion before proceeding. [10] Those statements are the EMA's, for the European Union; in the United States, compare any offer against the FDA's list of approved products and ask for the registry number of any study. See DIY Gene-Therapy Claims and Unapproved Clinics and Medical Tourism for Cell Therapies.
Safety note
Joining a trial is a medical decision with risks, including unknown long-term ones. Talk with your own doctor and the trial team about eligibility and consent. This page cannot say whether any trial is right for anyone.
References
  1. US FDA, What is Gene Therapy?. Read 2026-10-22.
  2. ClinicalTrials.gov, record NCT04601051 (NTLA-2001 in hereditary transthyretin amyloidosis). Read 2026-10-22.
  3. Gillmore JD et al. CRISPR-Cas9 in vivo gene editing for transthyretin amyloidosis. N Engl J Med 2021. PubMed 34215024. Read 2026-10-22.
  4. Musunuru K et al. Patient-specific in vivo gene editing to treat a rare genetic disease. N Engl J Med 2025. PubMed 40373211. Read 2026-10-22.
  5. Liu Y et al. Overcoming hepatic tropism: precision engineering of lipid nanoparticles for extrahepatic RNA delivery. Mater Today Bio 2026. PubMed 42677161. Read 2026-10-22.
  6. Fischell JM, Fishman PS. A multifaceted approach to optimizing AAV delivery to the brain for the treatment of neurodegenerative diseases. Front Neurosci 2021. PubMed 34630029. Read 2026-10-22.
  7. Monahan PE et al. Emerging immunogenicity and genotoxicity considerations of adeno-associated virus vector gene therapy for hemophilia. J Clin Med 2021. PubMed 34199563. Read 2026-10-22.
  8. Yang Y et al. Recent advances in non-viral vectors for gene therapy and gene delivery: from lipid nanoparticles to engineered extracellular vesicles. Pharmaceutics 2026. PubMed 42797269. Read 2026-10-22.
  9. US FDA, Long Term Follow-Up After Administration of Human Gene Therapy Products (guidance). Read 2026-10-22.
  10. EMA, Advanced therapy medicinal products: Overview. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.