Shire drug gets FDA approval

Federal regulators yesterday approved a drug made in Cambridge that is expected to be one of the world's most expensive medical treatments, at about $300,000 per patient per year.

Elaprase is the first-ever treatment for Hunter syndrome, an inherited and potentially fatal disorder in children that causes bulging features, growth problems, swollen organs, and eventual breakdown of the lungs. Only 500 patients in the United States are believed to have the disease, which affects mostly boys and can cause mental retardation.

A spokeswoman for manufacturer Shire PLC said about 100 people are taking the drug as part of its human clinical testing.

Elaprase joins a handful of highly specialized drugs called enzyme-replacement therapies, in which a crucial protein missing in patients' bodies is engineered in a lab and infused regularly into their bloodstreams. The global leader in such treatments is Genzyme Corp. of Cambridge, which has become a multibillion dollar business by selling a handful of drugs that treat fewer than 5,000 people each.

Drug companies' interest in such rare-disease treatments has grown dramatically in recent years as firms have shown they can reap large profits treating small groups of patients. They are protected by the 1983 Orphan Drug Act, which rewards companies that develop drugs for rare diseases by giving them seven years to sell each new treatment without competition from other manufacturers.

Cambridge has emerged as a capital for such ``ultra-orphan" drugs. Genzyme's success is built on Cerezyme, an enzyme replacement for a genetic disorder called Gaucher disease. It costs $200,000 or more annually for each patient. Cerezyme is used by about 4,500 patients worldwide and is expected to notch $1 billion in sales this year. Genzyme makes two related drugs for even rarer diseases, and sells a fourth developed by the California company BioMarin Pharmaceutical Inc . All are sold at similar prices, which vary by the patient's weight.

The drug approved yesterday, Elaprase, was developed by Transkaryotic Therapies Inc. , a Cambridge biotech firm. TKT also developed a similar drug, Replagal , which treats Fabry disease and is sold in Europe but not the United States.

Shire, a British company that focuses on specialized drugs, bought TKT for $1.6 billion last year, triggering a dispute by some stockholders who said the company should have brought a higher price. TKT's chief executive at the time, Michael Astrue , resigned to protest the merger, saying the company would be more valuable if it could have continued developing its drugs independently.

The firm is now known as Shire Human Genetic Therapies Inc. , with 425 employees and local headquarters in Kendall Square. Elaprase will be manufactured in the Alewife neighborhood of North Cambridge. Shire expects to begin selling it next month, and is simultaneously launching a program to help patients and doctors win insurance reimbursement to pay for their treatment.

The drug is administered in weekly infusions of one to three hours. In tests in 96 patients between age 5 and 31, Elaprase improved patients' walking and breathing ability, compared to a placebo. A small percentage suffered serious reactions to the substance .

Kyle Barrett , a 13-year-old Hunter patient who lives in Ayer, was one of the first to be given the drug in human trials. He and his parents flew to North Carolina every other week for infusions that his father, Bill Plunkett , said had a noticeable effect on Kyle's stamina.

``We had to traipse through Logan, through central parking, all the way to Terminal B, and he was running ahead of us -- that was a big change," he said.

Kyle likened the experience to the energizing bite that turns Peter Parker into a superhero in the movie Spider-Man.

``I kind of felt like I had the energy to do anything, to climb a wall," he said.

Ken Cacciatore , a pharmaceutical analyst for Cowen & Co. , estimated the drug could be a significant product for Shire, eventually selling as much as $250 million per year. He did not foresee the price causing problems for insurance reimbursement.

``Even though it's so expensive, there's really nowhere else to turn," he said.

Stephen Heuser can be reached at sheuser@globe.com.