N-of-1 Therapy Explained: What are the steps and timelines?
Key Takeaways:
• N-of-1 therapy is a personalized treatment designed for a single patient's unique genetic mutation. Several dozen patients have received individualized therapies since 2018.
• This article covers the steps and timelines to develop a custom medicine, including examples of prior programs that have reached patients; programs can move from start to dosing a patient in under a year for the right patients.
• Nome provides free evaluations to help families determine whether their child is a candidate and navigate the development process.
The Origins
In 2018, doctors at Boston Children's Hospital did something that had never
been done before. They designed, manufactured, and administered a brand-new drug for a single patient: a six-year-old girl named Mila who had a fatal form of Batten disease.
The drug, called milasen, was an antisense oligonucleotide (ASO) custom-built to target the specific mutation in Mila's CLN7 gene. It was developed in under a year, from diagnosis to first dose. It did not cure Mila, but it reduced her seizures and improved her quality of life during the time she had left.
That case, led by Dr. Timothy Yu, became the founding proof of concept for what is now called n-of-1 therapy: a treatment designed and manufactured for a single patient, based on their unique genetic mutation.
Since then, several dozen patients have received custom-built therapies through similar work.
This article explains how n-of-1 therapy works, who it is for, what the FDA pathways look like, and what families need to understand before pursuing one.
Which Patients Have Already Received N-of-1 Therapy?
Milasen was the beginning, but it was not an isolated event. Several landmark cases have since expanded the model and demonstrated that n-of-1 therapy is replicable:
Mila (2018): The first individualized ASO, developed by Dr. Timothy Yu's lab at Boston Children's Hospital for CLN7 Batten disease. Milasen reduced seizure frequency and was administered under an emergency IND.
Ipsen/Atipeksen (2020-2021): Additional patients treated by the Yu lab with individualized ASOs for different forms of Batten disease and other neurological conditions, refining the development and regulatory model.
Broader Programs (2023-present): Multiple academic and nonprofit groups, including the N=1 Collaborative, n-Lorem and foundations supporting individualized therapies, are now running parallel programs for different genetic conditions. The infrastructure is expanding.
Each of these cases advanced both the science and the regulatory precedent. The FDA has shown willingness to work with developers on these programs, and the pathway is becoming more defined with each new case.
How Does N-of-1 Therapy Work Step by Step?
The process of developing an n-of-1 therapy follows a general sequence, though timelines and specifics vary depending on the modality (ASO, gene therapy, etc.) and the regulatory pathway used:
Step 1: Genetic Diagnosis and Variant Identification
The process begins with a confirmed genetic diagnosis, ideally through whole genome or whole exome sequencing. The specific mutation must be identified at the DNA level, and its effect on protein function must be understood or predictable. Not every mutation is targetable, and part of the early assessment involves determining whether the variant is amenable to therapeutic intervention.
Step 2: Therapeutic Design
For ASO-based therapies, researchers design a short synthetic nucleotide sequence that binds to the patient's RNA to correct or compensate for the mutation's effect. For gene therapy approaches, the design may involve packaging a functional copy of the gene into a viral vector (such as AAV) or using gene editing tools (such as CRISPR/Cas9 or base editors) to correct the mutation directly. The design phase typically takes weeks to months.
Step 3: In Vitro Testing
The candidate therapy is tested in patient-derived cells (often fibroblasts or iPSC-derived neurons) to verify that it engages the target and produces the expected biological effect. This step provides early evidence of efficacy and helps refine the therapeutic design.
Step 4: Manufacturing
The therapy is manufactured under appropriate quality standards. For ASOs, this is often done at specialized compounding or GMP-lite facilities. For gene therapies, viral vector production is required, which involves more complex manufacturing and quality control processes. Manufacturing timelines range from weeks (for ASOs) to several months (for AAV gene therapies).
Step 5: Preclinical Safety Assessment
Depending on the regulatory pathway, different levels of preclinical toxicology testing is required. For ASOs with a well-characterized chemical class, this may involve abbreviated studies. For novel gene therapies, more extensive animal studies may be needed. The FDA has shown flexibility in scaling preclinical requirements based on the urgency of the patient's condition and the existing safety data for the platform.
Step 6: Regulatory Filing and IRB Submission
The development team files the appropriate regulatory submission with the FDA. This could be an IND (Investigational New Drug) application, an Expanded Access request, or a submission under the newer n-of-1 framework. Pre-IND meetings with the FDA are common and help align expectations on what data will be required. In parallel, it is important to engage the health system where the treatment will be administered to submit to their ethics and standards reviews to ensure they approve treating a patient at their facility.
Step 7: Treatment Administration and Monitoring
Once authorized, the therapy is administered to the patient, typically at an academic medical center with experience in gene therapy or rare disease treatment. Long-term monitoring follows, including safety assessments and biomarker tracking to evaluate whether the therapy is producing the intended effect.
Understand the realistic timeline. N-of-1 therapies are not instant. Even with the fastest pathways with very clear science, the process still takes 6-12 months; most treatments take longer, often 2-4 years. Still, this represents meaningful speed improvements over traditional biopharma development cycles of 10-14 years for an approved therapy.
Nome exists to help families navigate this landscape. We translate complex genetic information into actionable roadmaps, connect families with the right experts, and help coordinate the steps needed to pursue personalized treatment options.
What Is Nome Therapeutics?
Nome transforms complex genetic pictures into clear, actionable roadmaps that guide rare disease families to treatments. Our expert-reviewed reports help families understand their child's genetic diagnosis, identify potential therapeutic pathways, and connect with the clinical and research infrastructure needed to pursue them.
If your child has been diagnosed with a rare genetic condition and you want to understand what options may be available, take our 2-minute screener at nome.bio.
References
2. Yu Lab, Boston Children's Hospital. Published case series on individualized ASO therapies.
3. U.S. Food and Drug Administration. Expanded Access (Compassionate Use) guidance documents.
4. U.S. Food and Drug Administration. IND Application guidance for individualized therapies.
5. N=1 Collaborative. Program documentation and published outcomes.
7. Genetic Alliance. Resources on patient advocacy and access to investigational therapies.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Families should consult with qualified healthcare providers and genetic counselors before making treatment decisions. Regulatory pathways and requirements are subject to change.