Can the Tropical PRV Have Its Moment (Again?) – Not all Priority Review Vouchers are Created Alike: What the Potential Loss of the Rare Pediatric PRV Could Mean for the Tropical Disease PRV Program

Last December, Congress narrowly avoided a shutdown by significantly paring down the originally proposed 2025 Appropriations bill, slashing away hundreds of programs and laws. The Rare Pediatric Disease (RPD) Priority Review Voucher (PRV) was caught in the crosshair once again. This time, however, the program, which has helped incentivize the development of dozens of pediatric rare disease therapies since 2012, was not renewed.

Our colleagues have recently blogged about the RPD PRV here and here, its four-year sunset date, and the political drama that it frequently gets caught in. With the current lapse in authorization, FDA may only award RPD PRVs for applications that have received an RPD designation before December 20, 2024, and—unless reauthorized before then—may not award any RPD PRVs after September 30, 2026. Below, we discuss some of its downstream impacts on the PRV landscape.

An Increased Interest in the Tropical Disease PRV Program?

As our readers may already know, FDA maintained three PRV programs to incentivize the development of therapies for underfunded diseases: the RPD PRV program, which sunset last month, the Medical Countermeasures (MCM) PRV Program, which sunset in October 2023, and the Tropical Disease PRV Program. The Tropical Disease PRV program was not only the first priority review voucher program created by Congress, it is also the only one drafted without a sunset provision.

In 2006, David Ridley, Henry Grabowski, and Jeff Moe proposed a voucher in an article in Health Affairs as an incentive to develop therapies for “neglected” infectious and parasitic diseases that affect hundreds of millions of people in the developing world. The authors suggested that the developers of such therapies would receive a “priority review voucher” that they can sell to manufacturers of blockbuster drugs. The Tropical Disease PRV program was born the very next year as part of the Food and Drug Administration Amendments Act of 2007 (FDAAA) and expanded in 2014, which experts heralded as a “game-changer” for tropical disease therapies. In the eleven years from 2009 to the end of 2019, FDA awarded 11 tropical disease PRVs for the development of therapies for diseases such as malaria, tuberculosis, dengue, and river blindness.  See Table 1.  But as the other PRV programs were created, the value of each voucher decreased, and the interest and investment in tropical diseases dropped.  Over the last 5 years, only three more drugs or biologics received a tropical disease PRV.  As of the start of 2025, tropical PRVs represent less than 20% of all the PRVs granted.

*The information presented is based on publicly released information, including GAO and RAPS. The authors do not give any guarantees for the accuracy of this data.

The Uncertainty Around the RPD PRV Program May Re-open the Investment for Tropical Disease PRVs

Of all the PRV programs, the RPD PRV program was the most productive. By our analysis, seventy percent of all priority review vouchers that have been awarded since 2009 were awarded to sponsors that developed therapies for rare pediatric diseases.  While lapse of this program may raise concerns about the end of the Tropical Disease PRV, such a result is highly unlikely.

First, the Tropical Disease PRV program is the oldest one on the books and was the only one that was drafted without a sunset clause. To axe the Tropical Disease PRV Program, Congress would have to draft legislation to change the current law and then pass it through both Congressional bodies rather than simply let it expire like it did with RPD and Medical Countermeasures. This seems like a tall order, especially when one considers that the original law was passed in 2007 with only seven votes against it in the House and unanimously in the Senate, and it was expanded unanimously in both chambers in 2014.

Second, the Tropical Disease PRV program is the only program that has seen a small, but regular expansion since its creation. As recently as 2020, FDA added Brucellosis, a zoonotic infection, to the list of tropical diseases for which sponsors are eligible for receiving a PRV. This suggests FDA’s continued interest in the program, making it unlikely to appeal to Congress to repeal it.

Finally, we note that if the RPD PRV program never returns, we would expect to see a large effect on the Tropical Disease PRV program in the form of increased value of each new PRV.  With no more RPD or MCM PRVs, there will be fewer PRVs for purchase (since RPDs made up 70% of the market), which would likely cause the price on the secondary market of each of the remaining PRVs to increase.  As a result, both Tropical Disease PRVs and any un-used other PRVs (as all PRVs earned can continue to be redeemed notwithstanding the end of the program) have the propensity to shoot back up in cost, perhaps to those $300+ million values we saw in 2020.  Only time will tell how much companies will be willing to pay for PRVs once they become even more scarce.

Tropical diseases affect hundreds of millions of people around the world. This might be the time for investors to bring their attention back to therapies for tropical diseases—they might get rewarded with a much more valuable voucher for it.