The first ultra-personalized drug — made for one patient, the only one who will ever take it — is raising all kinds of new questions about how to handle a scenario that's likely to only become more common, the New York Times reports.

Driving the news: The drug, described yesterday in the New England Journal of Medicine, treats the neurological disorder of an 8-year-old girl.

The genetic presentation of her disease is unique, but one of her doctors had an idea about how to treat it, which was eventually successful.

It's unclear how much developing the drug cost, but the girl's mother and doctor raised $3 million through a foundation and on GoFundMe.

The big picture: This raises huge questions about how to regulate this kind of extreme precision medicine, who should get it and who should pay for it.

Researchers will have to decide which of the tens of thousands of patients with rare diseases to prioritize when creating custom drugs.

Families would likely end up on the hook to pay for such custom drugs, automatically limiting who has access to them.

It's also unclear how much evidence the FDA needs of such a drug's safety and how to evaluate its efficacy.

The bottom line: We now have no choice but to answer these kinds of questions as they play out in real life. Ultra-precision medicine is no longer only theoretical.

Go deeper: The struggle to evaluate drugs