Will Priority Review Vouchers Encourage Orphan Disease Research?

In September 2007, the US Congress created an incentive as part of the FDA reforms, in which companies that obtain approval for an orphan drug recieve a voucher for a priority review of a second drug. The value of the voucher is in the speed at which priority reviews are performed as opposed to the standard review process. The former generally takes 6 months while the latter can take up to 18 months. My question is this: Given the amount of time it takes to produce ANY drug, is it worth the years of research and diversion of resources to focus on and keep an orphan drug in the pipeline, to save maybe a year on the FDA approval process, for something else that will, in the long run, probably earn much more money in return?

Read more about balancing orphan disease research in an article by Donna Young at BioWorld Today.