The priority review voucher (PRV) programs, created by Congress with an eye to incentivizing the development of new rare pediatric and neglected tropical disease drugs, have so far rewarded a wide range of small and large biopharma companies and products, though whether PRVs have actually spurred new research remains a question.

Andrew Robertson, head of regulatory science and policy at Sanofi, and Rachel Cohen, regional executive director for the Drugs for Neglected Diseases initiative (DNDi), which recently won a PRV in a collaboration to register a Chagas disease treatment, discussed with Focus what is to come and what has transpired so far in the two nearly decade-old PRV programs.

One of the most recent developments has been the creation of a third PRV program for medical countermeasures (MCMs), adding to the pile of indications eligible for winning the lucrative reward, which can be purchased (so far for between $67 million and $350 million) and used to speed the review of a new drug, usually a potential blockbuster.

As more PRVs come to market, the price that a PRV sells for was expected to and has declined, though with that decline, transparency on which vouchers are available for sale has also leveled off. But will the prices continue to fluctuate from the high of $350 million in 2015 to the more recent ones sold for about $100 million?

Robertson told Focus that the MCMs "would have a limited impact on the voucher" programs on the whole, "at least in the short term. Looking at projects currently in the pipeline, I think it’s reasonable to guess around 4 or so PRV-eligible approvals over the next 10 years," he said, which "shouldn’t drop the price too much."

The rare pediatric disease (RPD) PRV, though, will have a big impact over the next ten years, he said, noting, "If current trends hold, we should see between 35 and 40 RPD PRVs over the next 10 years. This is what would cause the most significant drop in value."

So why are there more PRVs awarded to rare pediatric disease treatments and companies than those for neglected tropical diseases? The discrepancy may not be a sign that the PRVs have necessarily spurred more research in one disease area more than in another.

Robertson noted that for rare pediatric diseases, "Many of the products were in the pipeline before the incentive was even passed into law – while some rare pediatric drugs may have relied on the PRV as an incentive, there is a strong reason to believe that several did not."

DNDi’s Cohen also explained to Focus that of the neglected tropical disease PRVs awarded, she’s seen variability among products in terms of whether original research was conducted by the companies winning the PRV, and if the drugs have been made accessible and affordable.

For instance, in 2009, Novartis won FDA approval for Coartem (artemether, lumefantrine) for the treatment of malaria, and was awarded the first PRV, but Cohen noted Coartem "has been around and registered for years" in other countries before the PRV was awarded, though Novartis has "done quite a bit to make sure it’s available and affordable."

In 2012, J&J’s Janssen won FDA approval for a tuberculosis drug known as Sirturo (bedaquiline), which the company did conduct two Phase 2 trials for, though Cohen noted there have been issues with affordability.

Knight Therapeutics, which won FDA approval in 2014 for Impavido (miltefosine) for patients with an infection spread by sand flies known as Leishmaniasis, has been "the poster child" for not ensuring availability and registering a drug that has been around for decades, Cohen said.

"Very few, if any, PRVs have been awarded as a result of new investments," Cohen said, noting that in discussions with some companies, a PRV is not likely to be enough to push a firm to invest in a specific disease area, though it does factor into the upside of moving forward an R&D project.

And as the prices for PRVs continue to fluctuate or decline, Cohen noted the importance of ensuring only products that meet strict criteria win a PRV.

"We’ve wanted to make sure the criteria are as strict as possible to truly reward novelty and access," she said, noting DNDi and its commercial partner Chemo Group’s pledges.

Cohen also said she’s seen an environment where the race to winning a PRV has hindered the sharing of research. And though she does not know how a legislative fix could help, it's been "an unfortunate consequence" of the voucher program.