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Rare Diseases

A Potential Breakthrough Treatment for Arginase 1 Deficiency Is on Its Way

Dr. Anthony Quinn

President and CEO, Aeglea

In 2016, Aeglea BioTherapeutics, Inc., a company that develops biotherapies that fight rare diseases, made a breakthrough discovery in the treatment of Arginase 1 Deficiency. Researchers have known for some time that patients with Arginase 1 Deficiency have a persistent increase in the levels of the amino acid arginine in the blood, which affects the nervous system and leads to premature death.

“The disease typically manifests around age 2 or 3,” said Dr. Anthony Quinn, president and CEO of Aeglea. “Parents may notice some muscle stiffness, they may notice spasms in the muscle, or they may notice the child’s walking has become a bit clumsy.”

Children suffering from Arginase 1 Deficiency may also show signs of slower development.

This discovery means a treatment that targets arginine in the patient’s blood could be effective.     

“Normally the arginase enzyme lives in the cell, it’s not normally in the blood,” Quinn explained. “The natural form of the enzyme, when in the blood, has got a very low ability to digest arginine, and also it’s very unstable, which means it hasn’t got the potential to be useful. Aeglea identified a way of making the human enzyme work much better.”         

Prior to Aeglea’s research, the options for patients suffering from Arginase 1 Deficiency were limited. One recommended treatment was to restrict the amount of protein in a patient’s diet.

“The rationale for that is that by reducing the amount of arginine or precursors of arginine  — amino acids in the diet that can actually form arginine — you may be able to reduce arginine level, and that may help disease manifestation,” Quinn said. “To make up for the missing essential amino acids, you may have to take essential amino acid supplements.

“The problem with those supplements is they don’t taste very nice, so it’s difficult sometimes for a parent to get a child to take essential amino acid supplements. Sometimes, because of the bad taste, you need to have a tube put down their nose into their stomach, or sometimes a tube directly into the stomach.”

Even these unpleasant treatments had very limited effects.

“Ninety percent of arginine in the body that’s in the blood is not coming from the diet. It’s actually coming from the normal breakdown of tissue that happens in people every day. That’s why diet has only a very limited effect on arginine levels.”

It often takes decades of research to make these kinds of major breakthroughs for treating rare diseases, which is why Aeglea is so pleased with its work on Arginase 1 Deficiency.     

“What we’re very excited by here,” Quinn said, “is that, for a disease of the nervous system like this, it’s very exciting that we’re at seeing evidence of clinical improvements in patients in a relatively short timeframe.”

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