Regulatory Explainer: Everything You Need to Know About FDA’s Priority Review Vouchers

Posted 03 November 2016 By Alexander Gaffney, RAC, Michael Mezher

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Since 2007, the US Food and Drug Administration (FDA) has issued a handful of special "priority review" vouchers which allow its recipient to expedite the review of any one of its new drug products. What are these vouchers, why is FDA issuing them and what benefit might they have for society? Find out in our latest Regulatory Explainer on the Priority Review Voucher system.

Last updated on 3 November 2016 to include:

  • Priority review voucher granted to Sarepta Therapeutics for its Duchenne Muscular Dystrophy drug Exondys 51.
  • Pediatric priority review voucher program expires 31 December 2016.

Read all of our Regulatory Explainers here.

I Don't Know Much About Drug Development - What are we Talking About Here?

FDA's priority review voucher (PRV) programs are about drug development, and specifically the time and cost of drug development and the conditions a new drug is intended to treat.

Developing a new drug is a costly and time-intensive affair. The cost of developing a new drug can range from the tens of millions to billions of dollars—and that assumes the development program is successful. Only about one in 10 drug products which enter phase I testing are ever approved in the US. For some hard-to-treat indications, like conditions affecting the central nervous system, success rates can be even lower.

The time it takes to obtain that approval can also be a major factor. Companies often take years, sometimes decades, to develop a drug before sending it to regulatory officials for review. Once FDA begins its review, it takes more than a year on average for regulators to approve a drug.

Drug Development Failure and Success

Why Does the Time and Cost of Drug Development Matter?

Assume, for a minute, that you're a pharmaceutical or biopharmaceutical company hoping to develop a drug. The time and cost it takes to develop a drug means you're going to need funding, either from private investors or public shareholders. In return for their initial investment, investors usually want a return on their investment. Most companies generate this return by selling their approved products, either directly to consumers or to payers like health insurers and government healthcare systems.

But what happens if no market exists for a product to be sold?

That's the problem faced by companies developing drugs for two types of populations: Drugs intended to treat so-called "neglected" tropical diseases, and drugs intended for so-called "orphan" diseases affecting relatively few individuals. For the former, a market exists for the drugs, but can be too poor to allow the company to recoup its development costs. For the latter, a market exists, but it can sometimes number in the hundreds of patients, again making it too small to recoup development costs without charging exorbitant sums of money.

Best Selling Drugs

In other words, if a company is looking to make the most money it can, it's unlikely to be able to do so by developing products for rare or neglected diseases.

In addition, developing drugs for rare and neglected diseases can sometimes be disproportionately difficult. Most prominent diseases in western countries benefit from research conducted by government entities like the US National Institutes of Health (NIH) or public health foundations. Their research helps expedite drug development by better helping companies to understand the pathology of the diseases they hope to develop treatments or cures for. Companies hoping to develop treatments for rare or neglected diseases often have to conduct more, if not all, of this early-stage research.

Are There Ways to Incentivize Drug Development to Benefit Specific Diseases?

Actually, yes.

Since the 1984 passage of the Orphan Drug Act, the US has begun to recognize that incentives can help spur development of new drugs for historically underserved conditions. Under the Orphan Drug Act, companies are eligible for several extra years of marketing exclusivity, during which time FDA is not permitted to approve a generic, for getting a drug for a "rare" disease approved. This is meant to give companies an added incentive to produce drugs intended for rare diseases, as it allows the company extra time to recoup its development costs and likely turn a profit as well.

To date, these incentives have proven wildly popular. Prior to the passage of the Orphan Drug Act, few medicines were approved to treat rare conditions—defined as affecting fewer than 200,000 persons in the US. Just three "orphan" drugs were approved in 1984, for example. In 2014, 49 orphan drug products were approved.

Approved Orphan Products

Not all drugs are reviewed by FDA in the same way. Most drugs are reviewed by FDA under "standard" review times, meaning FDA has 10 months to review each product before it is supposed to render a decision. However, the review clock stops each time FDA requests additional information from a sponsor, adding several months to the review process.

However, for certain drugs, FDA accelerates its regulatory review in the hopes of getting products to market more quickly.

Drugs intended for use in "serious conditions," or which "demonstrate the potential to be a significant improvement in safety or effectiveness," are permitted to be reviewed under FDA's Priority Review Designation pathway. As explained in an FDA guidance document, the pathway allows FDA to review a drug in just six months instead of the standard 10.

For companies and patients alike, FDA's priority review process can be extremely beneficial. For patients with serious conditions, the expedited review means they have access to a potentially life-saving or -changing treatment. For companies, it means they can market their product more quickly and begin recouping their often considerable development costs.

What Does all This Have to do with a Priority Review Voucher?

FDA's priority review vouchers (there are two types) are incentives meant to spur the development of new treatments for diseases that would otherwise not attract development interest from companies due to the cost of development and the lack of market opportunities.

To do this, companies are given a special voucher which allows them to have any one of their drugs reviewed under FDA's priority review system.

Priority Voucher System Figure

That Sounds Interesting. What is the History of the PRV Programs?

The priority review voucher system was first proposed in a March 2006 paper published in the journal Health Affairs, and written by Duke University's David Ridley, Henry Grabowski and Jeffery Moe.

In their paper, "Developing Drugs for Developing Countries," they proposed the creation of a priority voucher system specifically targeted at neglected tropical diseases, which the authors argued lacked sufficient development incentives to produce.

This "prize," as they called it, could be used in one of two ways: Either it could be redeemed by its recipient, or it could be sold to another company, which might want to have its own drug reviewed in a six-month timeframe.

The initiative later caught the attention of Sen. Sam Brownback (R-KS), who worked to introduce the first voucher system into a bill known as the Food and Drug Administration Revitalization Act, which was eventually renamed and passed as the Food and Drug Administration Amendments Act (FDAAA) of 2007.

What did the FDAAA do for the Priority Voucher System?

Section 1102 of FDAAA, "Priority Review to Encourage Treatments for Tropical Diseases," created the Neglected Tropical Disease Priority Review Voucher system.

As explained in the law and subsequent guidance documents, any new drug intended to treat the following list of tropical diseases is eligible to receive a transferrable voucher for priority review:

Eligible Diseases Under the Tropical Disease Priority Review Voucher System
MalariaBlinding trachoma
Buruli UlcerCholera
Dengue/Dengue haemorrhagic feverDracunculiasis (guinea-worm disease)
FascioliasisHuman African trypanosomiasis
LeishmaniasisLeprosy
Lymphatic filariasisOnchocerciasis
SchistosomiasisSoil transmitted helminthiasis
YawsTuberculosis
Added by Congress
Cueva virusEbola virus
Marburg virusZika virus
Added by FDA Order
ChagasNeurocysticercosis

FDAAA also gave FDA the regulatory authority to add "any other infectious disease for which there is no significant market in developed nations and that disproportionately affects poor and marginalized populations."

In December 2014, legislators added several new viruses to the list of diseases eligible for a voucher including Cuevavirus, five strains of Ebolavirus and two strains of Marburgvirus (more on that below). In August 2015, FDA exercised its authority to add to the list of eligible neglected tropical diseases for the first time, adding, Chagas disease and neurocysticercosis to the list.

Are There any Limitations on How Tropical Disease Priority Review Vouchers Can be Used?

Yes, though subsequent legislation eliminated some of those limitations.

For example, FDAAA originally required a drug sponsor to alert FDA at least 365 days before it planned to apply a voucher to the submission of a new product. That limited the usefulness of the voucher for many companies, as it slowed down the drug development process. Some companies do not know if they plan to file a new drug application until they receive the results of late-stage (Phase III) clinical testing.

Another limitation contained in FDAAA was the number of times a voucher could be sold: only once. While a 2008 guidance by FDA allowed companies to buy and sell options on vouchers, once a company purchased a voucher, it could not be resold—a major risk for the purchaser. For example, if a company's sole drug product failed before it could use the voucher, it would have been effectively useless.

A third limitation (if you can call it that) is the cost to redeem the voucher. Under FDAAA, FDA is permitted to charge a company redeeming a voucher the added cost of conducting a priority review in addition to the normal new drug user fee.

Since the priority voucher user fee was first established in FY 2011, the cost to use it has ranged as high as $5.28 million (2012) and as low as $2.32 million (2014).

Tropical Disease Priority Review Voucher User Fee
Fiscal YearVoucher Fee
FY 2011$4,582,000
FY 2012$5,280,000
FY 2013$3,559,000
FY 2014$2,325,000
FY 2015$2,562,000
FY 2016$2,727,000

What Other Types of Vouchers Exist?

To date, only one other type of voucher exists: The Rare Pediatric Disease Priority Review Voucher.

The rare pediatric voucher was created in 2012 under the Food and Drug Administration Safety and Innovation Act (FDASIA), and specifically targets the need for additional therapies for rare pediatric subsets of other diseases.

Section 908 of FDASIA defines a "rare pediatric disease" as one which "primarily affects individuals aged from birth to 18 years, including age groups often called neonates, infants, children and adolescents," and is a rare disease according to federal statute (200,000 persons in the US or fewer).

The rare pediatric voucher system is closely modeled off the tropical disease voucher system, with several exceptions. Perhaps the most notable difference at the time of the pediatric voucher's initial passing was its relative ease of use. Unlike the tropical voucher, which required FDA to be notified 365 days prior to its use, the rare pediatric voucher could be used just 90 days prior to its use.

Another key difference: The rare pediatric voucher could be transferred (i.e. sold) an unlimited number of times, unlike the tropical disease voucher which could only be sold once.

However, as of December 2014, both of these differences have been erased under the Adding Ebola to the FDA Priority Review Voucher Program Act, which eliminated the disparity between the two vouchers. Tropical vouchers may now be redeemed in just 90 days, and may be resold an unlimited number of times.

FDA has also indicated that the vouchers will require the same user fee.

Rare Pediatric Disease Priority Review Voucher User Fee
Fiscal YearVoucher Fee
FY 2014$2,325,000
FY 2015$2,562,000
FY 2016$2,727,000

How Many Vouchers Have Been Awarded so Far?

FDA has awarded a total of nine priority review vouchers, six for rare pediatric indications and three for tropical disease treatments:

Priority Review Vouchers Awarded to Date
Date Voucher AwardedVoucher TypeCompany Voucher Awarded to:
2009Tropical DiseaseNovartis
2012Tropical DiseaseJanssen
2014Rare Pediatric DiseaseBioMarin
2014Tropical DiseaseKnight Therapeutics
2015Rare Pediatric DiseaseUnited Therapeutics
2015Rare Pediatric DiseaseAsklepion Pharmaceuticals
2015Rare Pediatric DiseaseWellstat Therapeutics
2015Rare Pediatric DiseaseAlexion Pharmaceuticals
2015Rare Pediatric DiseaseAlexion Pharmaceuticals
2016 Tropical Disease PaxVax Bermuda
2016Rare Pediatric DiseaseSarepta Therapeutics 

Have any Vouchers Been Used or Sold so Far?

Just as interesting as who obtained the vouchers is what has happened to those vouchers.

Status of Existing Priority Review Vouchers
CompanyVoucher TypeStatus of Voucher
NovartisTropical DiseaseUnsuccessfully used by Novartis to accelerate the review of its Biologics Licensing Application (BLA) for Ilaris (canakinumab).
JanssenTropical DiseaseUnused.
BioMarinRare Pediatric DiseaseSold to Sanofi and Regeneron for $67 million. Used successfully to speed the approval of Praluent.
KnightTropical DiseaseSold to Gilead Sciences for $125 million. Gilead announced it had used the voucher in support of its NDA filing for its HIV drug Odefsey. FDA approved the drug in six months on 1 March 2016.
United TherapeuticsRare Pediatric DiseaseSold to AbbVie for $350 million in August 2015. AbbVie has not disclosed how it plans to use the voucher.
Asklepion PharmaRare Pediatric DiseaseTransfered to Retrophin under an existing agreement. Sold to Sanofi for $245 million in May 2015. In February 2016 Sanofi redeemed the voucher to support its NDA for a new type 2 diabetes drug.
Wellstat Therapeutics Rare Pediatric Disease Transferred to AstraZeneca under an existing agreement. Unused by AstraZeneca.
PaxVax BermudaTropical Disease Unused. Likely sold to Gilead for ~$200 million
Alexion PharmaceuticalsRare Pediatric DiseaseUnused.
Alexion Pharmaceuticals Rare Pediatric DiseaseUnused, though the company has publicly disclosed it will keep one of its PRVs.
Sarepta Therapeutics Rare Pediatric DiseaseUnused.

Perhaps the most notable aspect of the vouchers so far is the price they have been able to command. BioMarin's voucher, the first ever to be sold, was purchased for $67 million. Several months later, Gilead Sciences purchased Knight Therapeutics' voucher for $125 million. In May 2015, Sanofi purchased yet another voucher for a record-setting $245 million, and in August 2015, AbbVie shattered that record by paying $350 million for a voucher originally awarded to United Therapeutics.

In July 2016, Gilead disclosed it had purchased a priority review voucher in a US Securities and Exchange Commission (SEC) filing. However, the party the voucher was purchased from and amount it was purchased for remain unknown.

Are There any Risks to Using a Priority Review Voucher?

There are several risks inherent to using a PRV.

The first and most obvious is that FDA is under no obligation to approve a product using a voucher. Both FDASIA and FDAAA stipulate that FDA only needs to come to a decision within six months. As Novartis proved in the first-ever use of a priority review voucher, FDA will not necessarily approve a product just because its sponsor used a voucher.

Priority review will likely accelerate the approval of a good drug to market, but it will not save a bad drug from being rejected. And for companies that are unsuccessful in their use of a priority review voucher, the cost of failure can be especially high due to the cost to procure and use the voucher.

New Drugs Vaccines Rate of PRVs

Another little-known limitation is that FDA claims it isn't actually required to review all drugs submitted using a voucher in six months. As explained in FDA's tropical disease voucher guidance, sponsors are not "guaranteed a six-month review" of their new drug product.

"We believe the intent of this section is that drugs for which priority review vouchers are used should be treated as if they were any other priority review drug. Therefore, these applications would be placed in the priority review group. The Agency has committed to a goal of completing 90 percent of priority reviews within 6 months."

The agency's rare pediatric disease voucher guidance contains similar language:

"Although FDA's goal is to take action on the application within 6 months after the 60 day filing period for an application involving a new molecular entity or within 6 months after the date of receipt of an application not involving a new molecular entity, this timeframe is not guaranteed. Note that "take action" in this context means that FDA aims to complete its review of the filed application and issue an approval or complete response letter within this timeframe; it does not mean that the application will be approved within this timeframe."

Have There Been any Changes to the Priority Review Voucher Program?

In 2014, US legislators made a major change to the tropical disease priority review voucher program with the intent of providing additional incentives to fight the Ebola virus and several other related viruses.

The changes were spurred in part by an op-ed by David Ridley, one of the fathers of the original voucher plan, in which he proposed adding "other infectious diseases" to the list of diseases eligible to receive a voucher. While FDA was already permitted to add additional diseases to its list through the regulatory process, legislators said they feared that process would take too long and would not be completed until the Ebola outbreak had potentially ended.

On 16 December 2014, President Barack Obama signed into law the Adding Ebola to the FDA Priority Review Voucher Program Act. The law made several subtle but important changes to the neglected tropical disease voucher program.

First, the law permitted the tropical vouchers to be used just 90 days after a company notified FDA of its intent to file a new drug. Previously, companies were required to notify FDA 365 days in advance.

Second, the law allows tropical vouchers to be resold an unlimited number of times. FDA had previously interpreted the statute to allow only one sale of the voucher.

Third, the law adds " filovirus"—a category of diseases which include five strains of Ebolavirus, two strains of Marburgvirus and the lone strain of Cuevavirus, known as Lloviu virus.

Genus name Virus name
CuevavirusLloviu virus
EbolavirusBundibugyo virus
Reston virus
Sudan virus
Taï Forest virus
Ebola virus
MarburgvirusMarburg virus
Ravn virus

Fourth, the law permits FDA to add any new viruses to the list of tropical diseases eligible for a voucher "by order" instead of "by regulation." This change will permit FDA to make changes much more quickly, and to avoid the lengthy notice-and-comment provisions of federal regulation.

Are There any Criticisms of the Priority Review Voucher Program?

There have been several major criticisms levied against the priority review voucher program.

First, there have been some questions about whether the voucher system is actually incentivizing development, or is rather just acting as a giveaway to companies which would have developed the new products anyways. In a January 2015 Public Library of Science article, authors Bernard Pécoul and Manica Balasegaram looked at the tropical disease voucher obtained by Knight Therapeutics, and found that other companies and entities had done much of the development work to get the company's tropical disease drug approved.

The group Medicines san Frontiers has levied similar claims against the voucher program, and argued that companies should be required to show they conducted the research necessary to obtain approval for the drug.

Other experts, including the Drugs for Neglected Disease Initiative's (DNDi) Rachel Cohen, have noted that the voucher systems actually do not require a company to sell a drug. In other cases, companies might seek regulatory approval for a tropical disease drug which is marketed outside the US in the hopes of obtaining a voucher. This should be banned, one of the founders of the voucher program, David Ridley, has said.

The voucher program also doesn't require the drugs provided through the program to be affordable. David Ridley has proposed requiring companies to report on the affordability of drugs that receive a voucher from FDA, and called on companies to voluntarily ensure that the drugs are affordable to those who need them.

Then there's a more fundamental question: Would these drugs have been developed were it not for the possibility of obtaining a voucher? While defenders of the voucher program have said the existence of the vouchers provides a powerful incentive for companies to consider developing new drugs, there's little evidence to show the drugs wouldn't have been developed anyway.

Unfortunately, it's not yet possible to determine whether FDA's priority review voucher programs are having an effect. As we stated at the outset of this article, it often takes a decade to develop a new drug, and any new development catalyzed by the creation of the voucher system may not be evident for several more years. One study recently published in the Public Library of Science estimated that FDA will issue between five and six new vouchers between 2016 and 2018.

Another criticism, levied by Aaron Kesselheim in the New England Journal of Medicine in 2008, is that while the voucher program is intended to be used only for new drug ingredients, it ignores the potential utility of new innovations.

"As a result, an effective novel antimalarial drug that degrades in the heat and must be taken six times a day would earn its sponsor a voucher, but no voucher would be granted for a follow-on formulation that might be more useful in resource-poor settings," he wrote.

Kesselheim also noted a broader concern, raised by other experts as well, that the priority review process is improper to use for drugs lacking an urgent need. "The voucher program will allow drugs for which there is little or no clinical urgency to be subject to accelerated deadlines and may lead to approval of products without adequate consideration by the FDA," he wrote.

Do Any Other Countries Have a Voucher System in Place?

No, although a September 2010 article in The Lancet—again authored by David Ridley—proposed the creation of a European voucher system which would accelerate the review of medicines as well as pricing and reimbursement decisions. The proposal has not yet been adopted.

Are There Other Diseases FDA Might Add to its List of Eligible Neglected Tropical Diseases?

The World Health Organization (WHO) recently called on governments to "increase investment to tackle neglected tropical diseases."

In August 2015, FDA exercised its ability to add to the list for the first time, adding Chagas disease and neurocysticercosis to the list of eligible neglected tropical diseases.

Many of the diseases on its list are already contained on FDA's list of neglected tropical diseases, but several are not:

Which Diseases Aren't on FDA's List of Neglected Tropical Diseases?
RabiesEchinococcosis
Taeniasis Foodborne trematodiases

And with the inclusion of the Ebolavirus, Chagas and other diseases to the list, it is possible Congress and FDA may soon eye other diseases for inclusion on the list as well, including the Middle East respiratory syndrome coronavirus (MERS-CoV), Chikungunya, the avian flu virus and other diseases thought to present a security risk to the US.

Are There any Potential Changes Coming to the Priority Review Voucher System?

The Rare Pediatric Disease PRV program sunsets on 31 December 2016 unless re-authorized by Congress. Both the House and the Senate are working to add an extension of the program through 2022 into another bill. 

Where Can I Learn More About Priority Review Vouchers?

You should read FDA's two related guidance documents:

Guidance for Industry: Tropical Disease Priority Review Vouchers

Guidance for Industry: Rare Pediatric Disease Priority Review Vouchers, Guidance for Industry

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Tags: Priority Review Voucher, PRV, Neglected Tropical Disease, Neglected Tropical Disease Priority Review Voucher, Rare Pediatric Disease Voucher, Rare Pediatric Disease, FDASIA, FDAAA, Voucher, FDA Voucher, Guidance, AbbVie, United Therapeutics, Praluent

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