Baby with ornithine transcarbamylase (OTC) deficiency responds well to gene therapy trial

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A baby boy with a rare genetic disorder is making “incredible” progress after he became the first infant to receive a groundbreaking new gene therapy.

Fourteen-month-old Tomas was diagnosed with ornithine transcarbamylase (OTC) deficiency when he was a few weeks old – becoming just one of 15 each year diagnosed with the rare genetic disease.

An OTC deficiency is when ammonia, a waste product that is generated when the body breaks down proteins, builds up in a person’s blood.

Ammonia is usually processed in the liver and removed through urine but patients with the condition have a genetic deficiency in the protein in the liver which is responsible for detoxifying ammonia, allowing ammonia to build up, which can be toxic.

It can cause life-threatening complications including brain damage, coma or seizures, if left untreated.

Treatment can include removing protein from the diet and medication known as “scavenger therapy” – but in severe cases, this is not enough. Some patients, especially baby boys with the condition, sometimes require a liver transplant.

The 14-month-old has become the first ever patient to receive a new gene therapy (Handout/PA Wire)

It was thought that a transplant would be the only option for Tomas, until he was enrolled on to the groundbreaking gene therapy trial at Great Ormond Street Hospital (GOSH) in London.

Symptoms of the condition typically start to show shortly after birth, including extreme tiredness, inability to feed and vomiting.

Tomas’s parents noticed something was wrong when he was just one week old.

“Tomas became unresponsive at home and wouldn’t open his eyes which was really scary

“We called an ambulance, and we were taken to our local hospital. When we first arrived, the doctors couldn’t determine what was wrong with Tomas.

“We spent the whole day there, from morning until evening, while they suspected an infection but were not certain. Tomas was getting worse, and unfortunately, the hospital couldn’t help us. That’s when we were transferred by ambulance to GOSH.

“When we arrived at GOSH, within an hour or two, they told us that Tomas’s ammonia level was too high.”

Tomas was diagnosed with ornithine transcarbamylase (OTC) deficiency when he was a few weeks old (Handout/PA Wire)

Medics at the world-renowned children’s hospital diagnosed him with OTC deficiency and asked if he wanted to be enrolled on the OTC-HOPE trial.

The trial is examining the gene therapy which is delivered via an infusion to reach the patient’s liver cells and has been designed to restore the damaged OTC gene with a functioning copy.

Researchers said the new therapy, called ECUR-506, uses a new way of inserting a gene – the functioning OTC gene copy is designed to be inserted very precisely at a specified location in one of the chromosomes.

It is hoped that the treatment will be comparable to the results seen in a liver transplant among OTC deficient patients – but using a one-time treatment instead.

Tomas received the treatment last summer.

Mariana said: “Six months later and he no longer needs the steroids and is making good progress – he no longer needs a special diet and scavenger medications.

“We’re extremely grateful for the help and support we’ve had from the doctors and nurses at GOSH.

“We thought a liver transplant would be Tomas’s only option and this would be tricky. We’re so pleased he was able to have the gene therapy – it’s been incredible. We recently celebrated his first birthday.”

Principal investigator for the study, Julien Baruteau, consultant in metabolic medicine at GOSH and clinician scientist fellow at University College London Great Ormond Street Institute of Child Health, said: “We’re pleased to see Tomas’s progress since having the gene therapy.

“He no longer needs the standard treatment of ammonia scavengers and is eating age-appropriate levels of protein for a baby of his age.

“Standard of care for babies with neonatal OTC deficiency relies on liver transplantation in infancy, a procedure with significant risk of complications.

“This novel gene therapy approach might enable babies with the condition to avoid this.

“I’m hopeful that Tomas will continue along this encouraging trajectory and that other babies who enrol in this study will have similar experiences.

“To our knowledge this is the first time a baby has received a liver-directed gene editing therapy. This novel technology may herald new avenues to treat babies with severe liver genetic diseases.”

Dr Baruteau is presenting initial data to the Annual Clinical Genetics Meeting in Los Angeles on Friday.