For the first six months of Christian Mumm's life, his family lived on high alert. Christian, who has a genetic disease that causes severe epilepsy, experienced frequent seizures - at his worst, one every 10 minutes - that left him depleted and jumpy. His three older brothers and sisters tiptoed around the house in New Hartford, Connecticut, afraid that if they breathed the wrong way or clinked a dish too loudly, it would set off a storm in his brain.
Christian's mother, Erica Mumm, recalled one heartbreaking day when her 9-year-old daughter came to her in tears.
"I kissed him, Mommy, and he had a seizure," her daughter said. "I can't kiss him anymore."
After a half-dozen drugs failed to help Christian, doctors suggested the family try one called Potiga.
The medicine has had a powerful effect. Seizures that once struck multiple times an hour now come once every five or six days. But the drug came with a deadline: At the end of June, GlaxoSmithKline, the British drug company that sells Potiga, pulled it off the market because of declining sales, forcing families to stockpile supplies or wean their children off a drug that dramatically improved their quality of life.
The dilemma faced by parents whose children benefited from Potiga - and future families who potentially may never have access to the drug - highlights the limitations of drug companies' business model.
Drug companies' investor-driven business model allows them to make risky research bets to develop innovative drugs. But at the end of the day, it means products that are essential to sick people are being made by businesses.
That may leave few options to small patient populations who depend on a drug.
"There are people who've already been taking the drug, and based on their perceptions, it's helping. I actually find this one more heart-wrenching," said Alison Bateman-House, an assistant professor in the division of medical ethics at NYU Langone Health. "Yes, we realize you were getting benefits, but because of financial realities, and just what we choose to do with our business, we're not going to make the drug anymore."
GlaxoSmithKline said it has recently been in touch with two families, including the Mumms, to find a way to make the drug available. But the company is not presently making commitments to future patients, and its ability to supply the drug is not indefinite, because the remaining supply will eventually expire.
"We care deeply about patients and realize that any time a medicine is removed from the market it can be challenging," GSK spokeswoman Sarah Spencer said in an email. "At this time, our focus is on the very small number of patients who are currently receiving the product."
Christian's severe form of epilepsy stems from a mutation in a gene called KCNQ2. That mutation causes electrical signaling in Christian's brain to go haywire, and Potiga - though it was approved as a general seizure drug for adults - had a unique mechanism among epilepsy medications. It worked by targeting the precise biological defect that was at the root of Christian's disease.
Christian still suffers developmental delays, but his quality of life is vastly improved. On the drug, he can interact with his siblings. He babbles and can learn and build on simple abilities, such as eating by mouth and smiling.
Physicians who treat and study patients like Christian say Potiga is a quintessential example of how 21st-century medicine is supposed to work. As scientists learn more about the biological causes of disease, they will be able to design drugs or rediscover old ones that treat not just symptoms but also the root causes of illness. Potiga was developed and approved to control seizures in adults with epilepsy, but it came with a bonus - it worked in a new way, by targeting potassium channels in the brain.
"Here we have 30 years of NIH-sponsored and industry-sponsored research leading to the specific understanding of a catastrophic illness. We have a drug that acts on that mechanism," said Edward Cooper, an associate professor of neurology and neuroscience at Baylor College of Medicine. Taking it off the market "goes exactly against what our policymakers are explicitly trying to do, which is make available precision medicines to address unmet medical need."
According to a 2011 study in Pharmacoepidemiology and Drug Safety, 118 novel drugs were withdrawn from the market between 1980 and 2009. Only a fifth of them were withdrawn primarily because of safety issues.
The plight of families who depend on Potiga is far from common, but it could become more so with the increasing recognition that a medicine that fails one group of people may be critical for another subgroup. There's a major push in medicine toward using science to identify the set of people for whom a drug works.
But when drugs live or die depending on commercial viability, mass-market drugs that don't fulfill their initial purpose may not be available.
From another point of view, Potiga is simply not a very good drug - an epilepsy medicine that was only ever approved for adults and turned out to have a big safety downside.
After it was approved in 2011, a scary side effect that caused blue-tinged skin and possible vision problems was uncovered, leading to a severe "black box warning" on the drug's label. The safety problems made Potiga considerably less attractive than the other options available to the people it was approved to treat - adults with epilepsy. The drug was never tested in children because of the safety concerns and a hold on trials by federal regulators, according to Spencer, the GlaxoSmithKline spokeswoman.
"No neurologist has become dehydrated for weeping tears over the removal of a drug with so much promise and so little performance!" Robert Clancy, a professor of neurology at the Children's Hospital of Philadelphia, wrote in an email.
Potiga sales peaked in 2013, at $14 million in U.S. sales, according to data from QuintilesIMS, a company that tracks health-care data - far from analysts' original estimates that it could reach more than $200 million per year. When GSK announced it would discontinue the drug last summer, there were fewer than 500 prescriptions per month.
The Mumms have stockpiled as much of the drug as they could, spending about $1,200. They have about three months left. In late July, they finally got word that the company would help them get access to the medicine, but they have no idea how long the commitment will last.
"If they can do this to my kid, they can pull any other drug off the shelf of your medicine cabinet and do this to anyone else, without a second glance," Erica Mumm said. "These companies have great power, and they shouldn't be driven solely by profit. They do have an ethical responsibility to the patient."
Spencer said that GSK is open to discussions with other companies that may want to acquire Potiga but has not seen significant interest in the drug. She also noted that if a company acquires the rights to Potiga, it would still be approved only for use in adults.
Doctors can prescribe drugs for off-label use as they see fit, but if the company wanted to market Potiga specifically for a rare disease, it would need to conduct a trial to get approval. It would have to get the hold on pediatric research lifted.
Other than selling the drug to another company, there may be other options.
"There are these really niche markets in the corners of the pharmaceutical marketplace that need extra attention," said Aaron Kesselheim, an associate professor of medicine at Harvard Medical School. "If there was a nonprofit pharmaceutical manufacturer that wanted to jump in, this is the sort of place that could be a good possibility."
The current solution is a piecemeal approach.
Amy Buches has been told the company will find a way to provide the drug to her son, Stephen. The Bucheses are one of the two families that GSK has agreed to help get the drug.
Buches said that she is personally satisfied. "Yet, it is unsettling to know that there could be an infant born in the world this very moment that would benefit from Potiga, but will not be able to use it," she said in an email.
Mumm knows firsthand what it would mean to lose access to the drug.
In May, the Mumms - having heard that the company would not be making the drug available - began to wean Christian off Potiga. His seizures started up right away, multiple times an hour.
Mumm was in despair. Without the ability to control his seizures, the doctors were sedating her son. She emailed his palliative-care doctor. What was she supposed to do? Bring her son home in a fog of medicine and watch him disintegrate?
Just a few weeks earlier, Mumm had been hopeful, thinking about starting a new kind of therapy that could aid Christian's development, thanks to the improvements she had seen while he was on the drug.
Instead, she found herself asking if there would be a way to ensure her son had a peaceful death.
"I want to get all my ducks in a row with knowing options," Mumm wrote.
Mumm demanded that the doctors stop tapering his medicine, and her family went about securing as much of the drug as they could stockpile.
In July, company representatives got on a conference call with the family and Christian's medical team to find a way to give him access to the drug.