Rare diseases can be described in terms of incidence, etiology, morbidity, and survival. Incidence can vary, however, from rare (e.g., Gaucher disease, cystic fibrosis) to epidemic proportions (e.g., HIV, malaria, cholera). The incidence of less frequently occurring cancers (e.g., pancreatic and renal cell carcinoma, myeloma, and glioma), although more common in relation to other rare diseases, meet most regulatory requirements for orphan designation.
In a report of the top 200 brand drugs by retail dollars in 2007, 17 top brands (retailing from $144.7 million to $1.837 billion) had an approved orphan use. Six of these 17 top drugs, in terms of retail dollars, were indicated solely (USA) for an orphan use: opioid dependence, organ transplant rejection, relapsing multiple sclerosis, and cystic fibrosis. Eleven of the top 17 brands had an additional 2-9 approved uses, which likely factored favorably into their retail sales volume.
Blockbusters can get their start in rare diseases. Botox (botulinum toxin type A) was first approved in 1989 as an orphan drug for a rare eye movement disorder (blepharospasm) associated with dystonia before seeking approval for cosmetic use. ClinicalTrials.gov and the Pharmaceutical Research and Manufacturers of America (PhRMA) reported that over 80% of clinical research trials for rare diseases were not industry sponsored.
In regard to the misuse of the Orphan Drug Act, attempts to further subdivide diseases to achieve questionable subsets small enough to qualify for orphan designation seem unlikely to succeed given the requirement to provide support that a condition is a recognized disease with documented incidence. There are valid and appropriate ways to target subset populations (e.g., pediatrics, refractory patients, severe forms of a more common disease, specific genotype).
The 2007 FDA Amendments Act (FDAAA) priority review (transferable) voucher incentive program and the 2008 common application form agreement between the USA and EU regulatory bodies demonstrate further global support for rare diseases. The outlook going forward is that orphan indication exclusivity can be one aspect of a profitable drug’s overall product life cycle, including non-orphan uses, and can contribute to its profitability.
Source: Drug Information Journal