In May 2025, the World Health Assembly (the supreme decision-making body of the World Health Organization) adopted a landmark resolution declaring rare diseases a global health priority.

And in February this year the FDA’s Priority Review Voucher (PRV) programme was re-authorised and signed into law; it will remain in place until reviewed again in September 2029.

The PRV scheme incentivises development of new treatments for rare paediatric conditions, among other things. When a company is awarded a PRV, it is entitled to a cut in drug review times from ten months to six months; alternatively, it can sell the voucher. Recent sales have been worth between $150m to $200m; in March this year, Cyprium Therapeutics sold its PRV to Fortress Biotech for $205m.

PRVs are considered to be a prime source of non-dilutive capital. When a PRV is sold, the cash generated does not require the seller to issue new equity.

So, perhaps unsurprisingly, investment in rare disease biotechs has increased following renewal of the programme. Big Pharma, venture capital firms and others are actively investing in smaller rare disease biotechs through early-stage funding rounds, asset acquisitions and partnerships.

There are over 300 million people globally living with a rare disease, and somewhere between 7,000 and 10,000 known kinds. Only around 5% have an approved treatment; the vast majority have no effective therapy. Around one in 17 people will be affected by a rare disease during their lifetime. In the UK, this amounts to over 3.5 million people.

Around 80% of rare diseases are monogenic, caused by a mutation in a single gene, which makes them more suitable for highly targeted treatments such as gene silencing.

Historically, it has been the US that has set the pace in rare disease drug design and development, creating incentives that make it very attractive for smaller biotechs that typically focus on addressing a single disease.

The Orphan Drug Act of 1980 set out a range of incentives that includes market exclusivity, tax credits and support with getting into the clinic.

However, there are factors limiting this growth potential, not least a lack of awareness of rare diseases in general and early diagnosis.

According to Fortune Business Insights, the global rare disease therapeutics market was worth $204.8bn in 2025 and is projected to reach $425bn by 2034, a CAGR of 8.41%.

The US market is estimated to be worth around $92.4bn in 2026, about 41.5% of the global total and the US is expected to remain a leader in the global market due to strong orphan drug incentives and faster regulatory pathways.

The UK pales by comparison at around $11.52bn, just over 5% of global market revenues.

The Fortune report says increasing prevalence of rare diseases coupled with a growing focus on precision medicine are primarily driving this market expansion.
As more capital flows into orphan drug pipelines, the market is expected to see more product launches across neurological rare diseases.

The US dominates because the PRV programme creates a highly valuable and, more importantly, tradable asset. VCs and private equity firms are far more willing to invest in rare disease biotechs simply because they provide a financial return on investment.

While the UK is known for high-quality science and innovation, it has seen a sharp contraction in biotech fundraising. Without an equivalent to the FDA’s PRV programme, UK rare disease biotechs rely heavily on public markets, private investment or acquisition by larger global pharma to secure capital.

According to market analysis by Schroder’s, from April this year: ‘With public markets grappling with valuation volatility, the UK’s “golden triangle” of innovation – spanning London, Oxford and Cambridge – continues to produce the next generation of biotech champions.

‘Historically, the UK’s Achilles’ heel has been the “Valley of Death” – the gap between brilliant seed-stage science and the massive capital required for clinical trials. Too often, UK companies were forced to list in New York just to access the depth of capital needed to scale.’

In an article in Cure, Sergey Jakimov, founding partner at specialist biotech VC firm LongeVC, said: “Orphan therapies are already projected to be roughly a fifth of global prescription revenue.

“Pharma needs de-risked, clinically validated assets, and rare disease programmes tend to show up better in diligence – clearer endpoints, smaller trials, engaged patient communities and a higher likelihood of approval from phase 1.”

Jakimov added; “You usually know the gene, you know the protein and you know the patient. When a modality finally catches up to the biology, such as AAV gene therapy, ASOs, siRNA, base and prime editing – you can move from target ID to a clinical hypothesis in a shorter time span.”

The Fortune report cited above goes on to note that restricted awareness of diseases and challenges in early detection pose significant obstacles for growth in the rare disease treatment market, as numerous rare conditions exhibit non-specific symptoms that coincide with those of more prevalent illnesses.

Consequently, patients frequently navigate the long ‘diagnostic odyssey’ through various specialists, undergo repeated testing and follow inappropriate treatment routes before obtaining an accurate diagnosis.

Limited patient populations are a significant obstacle to growth for the global market, as the majority of rare conditions feature very small and geographically dispersed patient clusters. This means clinical trials can take much longer to organise and run.

Small sample sizes also restrict the validity of efficacy and safety data, which can heighten regulatory uncertainty and delay or postpone approvals. So even promising treatments can experience severely delayed market entry.
Taken together, these practical, real-world issues impact market growth.

In the UK, the Medicines & Healthcare Regulatory Agency (MHRA) is consulting on a new regulatory framework for bringing rare disease drugs more quickly to market.
It would be ideal if the UK could introduce a scheme similar to the PRV. With the proposed new framework, everything is in place to better manage the clinical trial and marketing authorisation process for rare disease therapies, but that appears to be where it stops.

Reducing regulatory and approvals timescales and costs can only be good for rare disease patients and their families, but adding this stronger incentive could transform the industry, making the UK a leading player in research and development in this key area.

Meanwhile, in the US, the FDA is calling on Congress to make the PRV scheme permanent, arguing that greater certainty could accelerate therapies for children with life-threatening conditions.

The FDA’s Commissioner, Martin Makary, said: “This proposal would permanently reauthorise the RPD PRV programme, creating more predictability for sponsors and ensuring children living with debilitating or life-threatening conditions have access to safe and effective therapies.”

Today, the scheme requires Congress reauthorisation every four years or so, but there have been gaps.

Reauthorisation of the FDA’s Rare Pediatric Disease Priority Review Voucher scheme has restored financial certainty and sparked intense interest from large pharma and institutional investors.

This higher investment activity is expanding the innovation pipeline and strengthening long-term growth prospects for smaller biotech companies and rare disease therapeutics.

But there are challenges to the growth potential in the rare disease market, ranging from difficulties recruiting patients for clinical trials (thereby delaying those trials, adding uncertainty to the trial results and adding cost) to the well-known ‘diagnostic odyssey’ faced by rare disease patients.

Ultimately, increased investment is good news for those living with a rare disease, and their families – something about which we can all feel a little better.

Dan Williams is CEO of SynaptixBio