Mother’s heartbreaking fight to get her son, nine, the drugs manufacturer won’t give him

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Sebastian Hamilton likes to park near his home in south London, where his mother Severin picks him up after school every day.

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But there are moments—when she hesitates at the foot of the climbing frame, or can’t find a familiar word—when she wonders: Is this the beginning of the end?

Nine, for Sebastian, is a progressive genetic disorder called mucopolysaccharideosis type IIIB, or Sanfilippo syndrome, a devastatingly brutal condition that takes away first children’s language, then mobility, and finally the ability to swallow and breathe.


There is no cure or cure – most children with Sanfilippo syndrome do not survive past their teens.

“There have been terrifying moments over the years where we felt like we were losing him,” says Saverin.

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‘Every time he gets in a car, gets out of the shower, climbs the slide, runs and walks down the street and up the stairs, I’m relieved and grateful, because I’ve seen other kids With Sanfilippo syndrome his age everyone loses all of those skills.’

But there is hope. And hope is like rocket fuel for parents like Saverin and her partner Cole (both work in the film industry – though Saverin is now focusing on being a full-time mom).

Sebastian Hamilton likes to park near his home in south London, where his mother Severin picks him up after school every day. But there are moments—when she hesitates at the foot of the climbing frame, or can’t find a familiar word—when she wonders: Is this the beginning of the end?

Sebastian’s future, and the future of thousands of others, rests on the outcome of important clinical trials, where pharmaceutical companies test drugs on groups of patients in search of success.

Mucopolysaccharidoses (MPS) are a group of rare, inherited disorders where the body stores large chemical molecules in organs, rather than clearing them.

Patients with Sanfilippo syndrome lack an enzyme that breaks down and recycles a sugar molecule called heparan sulfate, which is used to build bones, cartilage, skin and other tissues. In their case it builds up in the cells, causing progressive damage.

Sanfilippo syndrome occurs when both parents are carriers of the affected gene; They themselves have no symptoms and often have no family history.

Patients usually appear healthy by the age of two years, when developmental delays – slowness in walking and talking – become apparent.

Other symptoms include chronic diarrhea, trouble sleeping, hyperactivity, and behavioral problems.

The decline is usually rapid. Often when they are eight or nine years old they are fed through a tube and are wheelchair dependent. This condition is often referred to as childhood dementia.

When he was two and a half years old, Sebastian, a patient at Great Ormond Street Hospital, was enrolled in a trial of an enzyme replacement therapy drug.

‘We saw incredible results,’ says Saverin. ‘Sebastian was awake every hour of the night. Suddenly he was sleeping. And the diarrhea disappeared.’

But the trial was abruptly stopped in 2017, when Sebastian was four years old, because the US manufacturer, BioMarin, decided to stop investing in the drug because its market is small – a decision Severin’ utterly heartbreaking and described as ‘disappointing’.

Although Sanfilippo syndrome is rare (affecting around 150 children in the UK), it is estimated that around 3.5 million will be affected by a rare disease.

This is a significant number of patients for whom there may be no targeted treatment.

Eurodis, a group that represents 1,000 rare disease patient organizations in 74 countries, says it is not unusual for tests to stop without warning.

“Genetic disorders typically receive little attention from large pharmaceutical companies because the numbers involved are too small to expect their return on investment,” says Yan le Cam, CEO of Euroradis. ‘But each person matters – we must not leave anyone behind.’

Yet just as the enzyme replacement therapy trial was ending, another was just beginning. In 2016, 20 children, including two patients at Great Ormond Street Hospital, were recruited to receive a promising new drug, tralacinidase alfa.

But Sebastian was excluded from participating because the eligibility criteria eliminated anyone who had previously been treated with enzyme replacement therapy (ERT).

Sebastian’s doctors say there is little scientific basis for this clause — known as washout time — because the time it takes for an ERT drug to leave the body is just two weeks.

Alivex, the small US company that ran this trial, says the results have been spectacular, with evidence that the drug eliminates the buildup of heparan sulfate, reduces enlarged livers (one of the main symptoms) and Prevents the brain from shrinking. It can also reverse some of the damage already done. Alivex reports on its website: ‘These results show that tralacinidase alfa has promise to become a first-in-class and best-in-class treatment for Sanfilippo syndrome type B.’ (That’s what Sebastian has: just 27 babies were born with it in the UK between 2000 and 2020.)

For five years, Severin has campaigned to allow Sebastian to be treated before it is too late. He’s still overcoming obstacles: By age nine, most of the children with his disorder are in wheelchairs, but time is running out.

His doctor, Spiros Batzios, a consultant in pediatric metabolic medicine at Great Ormond Street Hospital and a principal investigator for the Alivex trial in the UK, wrote and spoke to the firm’s CEO Tom Mathers, begging Sebastian to get involved.

In May, Great Ormond Street Hospital wrote to Alivex to advocate on Sebastian’s behalf — it needs the company’s permission to provide the drug.

Saverin shows me stacks of personal letters to Tom Mathers. He has told Saverin that there is not enough medicine available for the second child, but that his company will expand access to all children with Sanfilippo syndrome in the future.

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