The process of receiving approval from the U.S Food and Drug Administration (FDA) is long and expensive. Critics in the pharmaceutical industry complain the process deters advances in medicine – and for its part, the FDA has devised several manufacturer incentives designed to address this concern.

In 2007, Congress created a program to encourage the development of drugs to treat tropical diseases and later expanded the program to cover rare pediatric disorders. Under the program, companies can apply for a voucher that can be used for a fast-track review of a drug. Under a normal application, review of a drug can take up to 10 months; but with a priority review voucher the FDA is required to decide on an application within six months.

The four-month time difference might not seem like much, but in today’s competitive market, it can mean the difference between patent protection for your blockbuster new drug or losing out entirely.

Some critics of the priority review voucher believe the shortened timeline is not long enough to make an informed decision about a new drug. Many applications are incredibly complex and regulators at the FDA must comb through mountains of data to understand the safety and efficacy of new drugs, and the priority review voucher gives them a shorter amount of time to do it.

However, a shortened timeframe isn’t the only thing FDA regulators are worried about with priority review vouchers. When vouchers are awarded to companies, they are allowed to do with it whatever they choose. This means companies can sell vouchers for top dollars. Just last year, a priority review voucher sold for a whopping $350 million. Whoever buys the voucher is allowed to use it on any type of drug not just drugs that treat rare diseases.

While the FDA believes in incentivizing the development of drugs for rare diseases, a spokeswomen for the agency has stated, the “FDA has not seen evidence that the program is effective.” The program granting priority review vouchers has been extended through the end of the year, but its fate seems to hinge upon critics and the FDA striking the appropriate balance between regulation and innovation.