Rare Disease Research Atlas

Of 255 diseases with usable interventional-trial matching in this build (300 total records; incomplete trial fetches and uncapped scans excluded from this percentage)

151

have no interventional trial under their specific condition name — 59.2% conservative; about 49% if broader-category registrations count.

Data as of 26 July 2026. Current-state claim — present tense.

Between roughly 49% and 59.2% of rare diseases have no interventional clinical trial — depending on whether broader-category registrations count. Counting only the specific condition name gives 59.2% (151 of 255); counting parent-category trials as filling a zero gives 49% (125 of 255). We report the conservative figure and show parent-category trials on each disease page. Prior matching choices in this project landed in the mid-50s to mid-70s — that spread is itself a finding about how poorly disease naming maps between literature and trial registries. Against the legacy human-reviewed reference, trial matching recall is 96% and precision 86%. Observational and natural-history studies are shown separately on disease pages because they are meaningful research and may be open to families, but they are not counted as interventional trials. Publication name-collision flags do not remove diseases from this trials denominator.

A fixed historical sample measurement (past tense) is on Methods & findings; the live site may differ.

Broader comparison: 128 of 255 (50.2%) have no matched registered study of any type, including observational studies. The difference between this and the headline is an editorial definition, not a correction to the data. Both figures exclude pan-disease registries.

Of these no-trial diseases, 47 have substantial published literature — a name that demonstrably matches papers, making the trial zero far likelier to be real than a search artifact. A further 43 records returned nothing on either database and are excluded from every percentage as probable broken queries, not measured absence.

Secondary finding: 9 of 181 (5%) have no publication in the last ten years and no interventional trial — intersection of the publications and trials denominators (183 and 255 respectively). Obsolete and “non rare in Europe” Orphanet entries are removed before sampling.

Corpus: sample n=300 seed=42 · excluded 801 obsolete/non-rare