In 2017, two parents asked scientist Stanley Crooke to create treatments for their children's rare mutations. Years later, a custom drug cut one boy's seizures by 90% and helped him walk on his own for the first time

For most of his childhood, Connor Dalby could not walk without help. His life was shaped by seizures, developmental problems and constant medical care. Then an experimental custom drug changed what his family thought was possible. The treatment was designed around Connor's specific genetic mutation. It did not simply treat symptoms. It targeted the faulty copy of a gene involved in his epilepsy. Within months, his seizures had fallen by 90%. He also began taking steps without assistance for the first time. His story is now raising a bigger question about medicine: what if some drugs could be designed for one patient at a time?

How a custom drug began with two parents and an unusual idea

The story reaches back to 2017, when two parents approached scientist Stanley Crooke about their children's extremely rare mutations. Both children had mutations involving SCN2A, a gene that helps control sodium channels in nerve cells. Their request exposed a problem that traditional drug development was not built to solve.

A conventional drug can take years of laboratory work, testing and clinical trials. That model makes sense when thousands or millions of patients may eventually use the treatment. It becomes much harder when a mutation may exist in only a handful of people worldwide.


Crooke had spent decades working on antisense technology. The idea behind these medicines is surprisingly precise. Instead of changing a person's DNA, an antisense oligonucleotide can interact with RNA and alter how genetic information is used inside cells.

That distinction became crucial for Connor.

His condition was linked to a complicated SCN2A variant. The researchers needed to reduce the harmful activity from the mutated copy while preserving the healthy copy. This required an allele-selective approach rather than simply switching the entire gene off.

The result was not a mass-market medicine waiting on a pharmacy shelf. It was a custom drug built around one patient's biology.

That may sound like science fiction. Yet personalized antisense treatments are beginning to make the concept practical.

Why did this custom drug target only one version of Connor's gene?

Connor's disorder illustrates why rare genetic diseases can be so difficult to treat. SCN2A-related developmental and epileptic encephalopathy can cause severe seizures early in life. It can also affect development, movement and behavior. The precise consequences depend partly on the individual genetic variant.

Connor reportedly experienced dozens of seizures each day during his early years. His family tried numerous anti-seizure medicines, but the results were limited. By his teenage years, he still could not walk independently.

The researchers therefore had to think differently.

The custom drug was designed to recognize a molecular signature associated with the harmful version of SCN2A. Researchers used an antisense oligonucleotide to reduce production from that mutant transcript while leaving the normal copy available.

It is an important distinction. This was not gene editing.

The treatment did not rewrite Connor's DNA. Instead, it acted further downstream, at the RNA level. That makes the approach potentially more flexible, but it also means the treatment may need to be administered repeatedly.

The researchers described two parallel n-of-one clinical studies involving boys with SCN2A-related developmental and epileptic encephalopathy. One patient experienced a 26% reduction in seizure frequency. The other experienced a 90% reduction. Both showed improvements in neurodevelopmental measures, and neither experienced a serious adverse event attributed to the antisense treatment during the reported study period.

That difference matters.

The 90% figure belongs to the patient whose story has attracted widespread attention. It should not be interpreted as proof that every person with SCN2A-related disease would experience the same response.

What happened after the custom drug was given?

The most striking part of Connor's story was not a laboratory measurement.

It was movement.

According to reporting from KPBS, Connor received his first dose at age 14. About four months later, his mother noticed him trying to take steps without assistance. It was something she had never seen him do before.

Connor is now 17 and can reportedly walk around 50 to 60 steps independently.

His seizures have also fallen by about 90%. His family has reported better sleep, behavioral improvements and greater independence. For a teenager who spent much of his life dependent on caregivers, those changes carry a meaning that cannot easily be captured by a percentage.

There is another detail worth considering.

A reduction in seizures can itself change a child's daily life. Frequent seizures interrupt sleep, learning, movement and interaction. When that burden decreases, the brain may have more opportunities to develop and practice skills.

Researchers therefore assessed more than seizure counts. The Nature Medicine study used individualized developmental measures and predefined treatment goals. The investigators reported gains that exceeded expected developmental progress for the patients.

This is where the custom drug story becomes more interesting than a simple medical breakthrough headline.

The treatment was not merely about stopping seizures.

It was an attempt to alter the biological problem causing them.

Can a custom drug change the future of rare disease treatment?

The biggest question is whether a custom drug can move beyond extraordinary individual cases.

That challenge is enormous.

Traditional clinical trials depend on groups of patients. Researchers compare outcomes across enough people to determine whether a treatment works and whether its risks are acceptable. But some genetic mutations are so uncommon that finding enough patients for a conventional trial may be impossible.

Scientists call some of these conditions “nano-rare.” A 2023 paper co-authored by Crooke described such mutations as single-gene mutations with only one to 30 known patients carrying the same mutation worldwide.

That creates a strange problem.

A patient may have a mutation that is biologically important but commercially invisible.

There may be too few potential customers to justify the traditional cost of drug development. Yet the patient's disease can be devastating.

The n-Lorem Foundation, associated with Crooke, has pursued an alternative model based on individualized antisense medicines for patients with extremely rare genetic diseases. The approach tries to make a custom drug for a specific patient and potentially learn from that case for other patients with related mutations.

The new SCN2A research suggests one possible route from one patient to many.

Researchers performed haplotype analysis in a separate group of infants and found that 16% had compatible single-nucleotide polymorphisms for this type of allele-selective approach. That does not mean 16% are automatically candidates for treatment. It suggests, however, that the platform could potentially extend beyond the original individual cases.

That is the deeper scientific significance.

A medicine can begin as a one-person experiment and still teach researchers how to treat a larger population.

What does the custom drug story reveal about the limits of personalized medicine?

It would be easy to call Connor's experience a cure.

The researchers themselves are more cautious.

The study involved only two patients. It was open-label and individualized. Long-term follow-up is still needed to determine how durable the benefits will be and what risks could emerge with prolonged treatment. The researchers also note that early treatment may matter greatly in disorders where developmental changes become difficult to reverse.

That caution is important because rare disease medicine has a difficult balance.

Families need hope. Scientists need evidence.

Connor's improvement provides meaningful evidence, but it does not answer every question.

The custom drug also does not eliminate the underlying genetic mutation. Its effects depend on continued biological activity, meaning treatment is not equivalent to permanently correcting the DNA. That difference could matter enormously over a patient's lifetime.

Still, something fundamental has changed.

For decades, medicine often worked by asking which treatment fits a disease. Personalized genetics reverses that question. It asks which treatment fits this patient's exact biological problem.

Connor's case shows why that shift matters.

His mother once had to measure life in seizures, hospital visits and mobility limits. Now the family can measure it differently. In steps taken alone. In better sleep. In greater independence. In experiences that once seemed out of reach.

That is the part of the custom drug story that statistics cannot fully describe.

The remarkable achievement is not simply that scientists made a medicine for one child.

It is that they demonstrated a different way of thinking about who deserves a medicine.

For common diseases, medicine has long relied on scale. Rare genetic disease may require precision instead.

The future will not make every ultra-rare mutation easy to treat. It will not remove the cost, regulatory hurdles or biological uncertainty. But the emerging evidence suggests that the old assumption—one disease, one standard treatment—may no longer be the only path.

Connor's first independent steps therefore represent something larger than a personal milestone.