The number of orphan drug designations in the US more than doubled in the last decade, growing from 208 during 2000-02 to 425 in 2006-08, says a new study.

Since the US Orphan Drug Act of 1983 was signed into law, more than 2,000 products in development have been designated as orphan drugs, while the Food and Drug Administration (FDA) has granted market approval to 350 drugs and biologics, according to the study, which was conducted by the Tufts Center for the Study of Drug Development (CSDD).

“The Orphan Drug Act, without question, can be considered a success. It has been emulated throughout the world, and today Japan and Europe have similar programmes, while Singapore and Australia give special allowance for the importation and marketing approval of orphan products approved in the US,” said Tufts CSDD associate director Christopher-Paul Milne, who conducted the study.

Orphan drugs are products developed for a rare disease or condition affecting fewer than 200,000 people in the US, while in the European Union (EU) they are defined as treatments for diseases or conditions affecting five people out of every 10,000, or fewer.

The new analysis, reported in the January/February Tufts CSDD Impact Report, also found that, during the 2000s, orphan products comprised 22% of all new molecular entities (NMEs) and 31% of all significant biologics (SBs) receiving US marketing approval. The percentage of orphan products receiving priority review status rose from 35% of all orphan NMEs in 2000-02 to 50% in 2006-08, while during the same period the share of orphan SBs receiving priority review status rose from 17% to 67%.

During the last decade, biotechnology companies received about one-third of all orphan drug approvals but only just over 50% of orphan drug designations, the study adds, also noting that sponsors engaged in clinical development funded through orphan grants reported that 22% of their programmes led to approvals, compared to a clinical approval success rate of 16% among mainstream drug developers.

The National Institutes of Health (NIH) estimates that 25 million Americans have a rare disease. Because of the relatively small number of patients affected by these rare diseases, many have been historically under-treated but, “as the Tufts report demonstrates, hope is on the horizon,” commented Billy Tauzin, president of the Pharmaceutical Research and Manufacturers of America (PhRMA).

According to a recent PhRMA survey, some of the medicines currently in development for rare diseases include: a monoclonal antibody for the immune system disorder chronic sarcoidosis; a treatment for Lennox-Gastaut syndrome - a severe form of epilepsy; a gene therapy for cystic fibrosis; and a medicine for the genetic disorder Friedreich’s ataxia._

”We find hope for the future of rare disease treatment by remembering the successes of the past," said Mr Tauzin. "In a 2006 report on rare diseases - conducted with the National Organization for Rare Diseases - we found that more than 160 new medicines for these illnesses had been approved in the decade between 1995 and 2005, compared with 108 such approvals in the decade prior, and fewer than 10 in the 1970s. Many of the new medicines were the first approved to treat a particular disease - that’s why this work is so important,” he added.