Drugs for rare diseases have higher than average approval rates for every stage of the FDA approval process. The approval rates were particularly striking when compared to rates for chronic, prevalent health conditions. These are some of the results recently published in a report, Clinical Developmental Success Rates from 2006-2015
. The study is a product of the biotechnology trade association BIO, the publishing company Informa, and the biomarker business company Amplion.
Success rates higher for rare disease drugs
To perform the analysis, the researchers used their Biomedtracker database, which is populated with information from press releases and other sources. They identified all prior FDA Orphan-designated indications, excluding rare cancerous diseases in their calculations. The researchers also analyzed drugs designed to treat prevalent chronic health conditions, with greater than 1 million people affected in the US.
The researchers analyzed the probability of moving ahead at each of the 4 stages of the drug approval process: moving from phase I to phase II, from phase II to phase III, from phase III to new drug application (NDA), from NDA to approval. At each phase, rates of approval were higher for rare disease drugs than they were for all diseases considered as a group. At each phase, they were rates of approval for rare disease drugs were also higher than the rates of approval for chronic, common conditions.
For example, 76% of rare disease drugs moved on from phase I trials, compared to 63% of drugs as a whole and 58% of drugs for rare chronic diseases. Similarly, 50% of rare disease drugs moved from phase II to phase III, compared to 30% of drugs overall and 27% of drugs for common chronic conditions. Overall, 25.3% of rare disease drugs successfully completed the full process of review from phase I to approval, compared to 9.6% of drugs overall and 8.7% of drugs for chronic conditions.
Why have rare disease drugs been approved more frequently?
The reason for these different rates of approval rates is unclear. It is possible that is simply easier to design effective drugs for rare diseases, many of which are genetic diseases with a single identifiable cause and a clear drug target. In comparison, many chronic diseases result from a complicated interaction of multiple genetic and environmental factors. In the end, it may be more difficult to design effective drug treatments for those types of conditions compared to genetic rare diseases.
It is also possible that the approval process itself gives greater allowances for drugs designed to treat rare diseases, even if this is not explicit. Under the FDA’s Safety and Innovation Act
(FDASIA), the FDA is required to incorporate patient input into their review and decision-making process. The FDA may in practice be more likely to approve a drug with borderline conclusive effectiveness for a rare disease population, as these drug trials often face challenges in getting large numbers of study participants.
Potentially, this higher rate of drug approval might serve as a further motivation for companies to invest in rare disease research. If companies believe they are more likely to see a direct return on their investment via FDA approval, they may be more likely to invest in this type of research.
What is clear is that there has been increased funding for companies focused on rare diseases in recent years, and the number of drugs approved is increasing. In 2015, about 47% of the novel drugs approved were for rare diseases
that affect 200,000 or fewer Americans. This cannot come soon enough for the patients with thousands of different rare diseases, most of which currently have no FDA approved treatments.