RE:RE:RE:RE:RE:RE:RE:RE:RE:RE:RE:Clinical Trial Size in Orphan and Rare Diseases From Orphanet :
It has been shown that orphan/ rare disease trials have smaller sample sizes than non-rare disease trials. Indeed some orphan drugs were approved by the European Medicines Agency based on studies with as few as 12 patients.
About 75% of the rarer diseases (<1/1,000,000 and 1–9/1,000,000) trials had size less than 50; actual median size, 15 (interquartile range, IQR, 8–55), anticipated median size, 20 (IQR, 10–30) for prevalence <1/1,000,000 and actual and anticipated median sizes for prevalence 1–9/1,000,000 were 22 (IQR, 15–40) and 38 (IQR, 23.5–77.5), respectively.
Trials of less rare diseases: 1–9/100,000; actual and anticipated median sizes were 36 (IQR, 20–64) and 47 (IQR, 30–70), respectively; and 1–5/10,000; actual and anticipated median sizes were 38 (IQR, 20–67) and 46 (IQR, 30–80).
https://ojrd.biomedcentral.com/articles/10.1186/s13023-017-0597-1