Tuesday January 22 6:28 PM ET
FDA OKs Drug to Fight Liver Disease
By LAURAN NEERGAARD, AP Medical Writer
WASHINGTON (AP) - Children born with a very rare but lethal liver disease - it often kills by their first birthday - have won the first drug that promises to help them live years longer.
The drug Orfadin amazingly is a failed weed killer that Swedish scientists discovered could fight a disease called hereditary tyrosinemia.
``This is a real breakthrough drug,'' said Dr. Marlene Haffner of the Food and Drug Administration (news - web sites), which just approved Orfadin's sale. She said scientists once referred to the drug as ``Lazarene, because these kids were so sick and then they were well.''
``This was an absolutely fatal disease until now,'' added Abbey Meyers, president of the National Organization for Rare Disorders, which is running a program for the drug's maker to ensure children who can't afford the super-expensive new therapy will get free or reduced-cost medicine.
Hereditary tyrosinemia type 1, or HT-1, is a genetic metabolic disorder that causes progressive liver failure and liver cancer in young children. It's very rare - fewer than 100 American children, and a few hundred more worldwide, are estimated to be living with the disease.
It is not among the metabolic diseases that all newborns are tested for at birth, so often infants die undiagnosed, Meyers said.
For babies who are diagnosed, the only treatment is a special low-protein diet. The reason: When the body breaks down the amino acid tyrosine, HT-1's genetic defect causes it to produce toxins that in turn cause liver cancer. Babies can't avoid all tyrosine or they'd never grow, so the diet helps but doesn't stop the disease.
Those who survive infancy rarely live into the 20s without a liver transplant.
Orfadin may significantly improve those dismal statistics: In an ongoing study of 180 patients who began the drug in infancy, 88 percent have survived four years and counting - far better than the normal 29 percent survival rate with diet alone.
It works by blocking formation of the liver-destroying toxins, Haffner said.
Orfadin didn't work for everyone and isn't a cure. Even in patients that the drug helped, no one yet knows if taking Orfadin for life could keep the disease at bay or if eventually they would need a liver transplant. Studies to determine that are continuing.
The drug's cost depends on the dose, which varies with the child's size: $12,000 a year for an infant, up to $60,000 a year for an older child, estimated Bo Allen, vice president of Orfadin's manufacturer, Rare Disease Therapeutics.
That's cheaper than a liver transplant, and thus many insurance companies are expected to pay for it, he said. But for families that can't afford the therapy, his company will provide it for free or at a lower cost in a program run by NORD. To enroll, families may call 1-800-999-NORD.
``We're not going to let any child go without the medication,'' Allen pledged.
About 10 years ago, scientists at Sweden's Gothenberg University discovered how HT-1 destroys the liver and began searching chemical databases for compounds that might block that disastrous action. They found a failed herbicide created by Zeneca Inc., which eventually donated the chemical for medical use, Allen said.
The tiny Nashville-based company won FDA approval under a special law that allows seven years of marketing exclusivity for products that treat rare diseases.
On the Net:
Food and Drug Administration: http://www.fda.gov
Rare Disease Therapeutics: http://www.raretx.com
National Organization for Rare Disorders: http://www.rarediseases.org
http://www.centerwatch.com/patient/drugs/dru765.html
Orfadin (nitisinone)
Mechanism of Action:
Nitisinone is a competitive inhibitor of 4-hydroxyphenyl-pyruvate dioxygenase, an enzyme upstream of FAH in the tyrosine catabolic pathway. By inhibiting the normal catabolism of tyrosine in patients with HT-1, nitisinone prevents the accumulation of the catabolic intermediates maleylacetoacetate and fumarylacetoacetate. In patients with HT-1, these catabolic intermediates are converted to the toxic metabolites succinylacetone and succinylacetoacetate, which are responsible for the observed liver and kidney toxicity. Succinylacetone can also inhibit the porphyrin synthesis pathway leading to the accumulation of 5-aminolevulinate, a neurotoxin responsible for the porphyric crises characteristic of HT-1. (from Orfadin Prescribing Information)
updated Janaury 20, 2007
