Largest Ongoing Rare Disease Drug Trials by Reported Enrollment: Selected Eligible IPF Trials

The largest studies in this selected list are two phase 3 idiopathic pulmonary fibrosis (IPF) trials: NCT06003426, with 1,255 participants reported as actual enrollment, and NCT07284602, with 1,100 reported as estimated enrollment.

This is not a definitive ranking across all rare diseases. It ranks ten eligible trials within a defined IPF search universe on ClinicalTrials.gov. IPF is listed by the NIH Genetic and Rare Diseases Information Center (GARD) as a rare disease. Each enrollment figure is the study’s reported total, not an estimate of U.S. recruitment or a measure of treatment benefit.

Table of contents

• What this selected ranking covers
• Ten selected eligible trials
• Reading enrollment and status correctly
• What this list says about rare disease research
• Frequently asked questions
• Explore clinical-trial data in QOPE
• Sources

What this selected ranking covers

The search universe was ClinicalTrials.gov’s condition search for “Idiopathic Pulmonary Fibrosis,” filtered to Recruiting, Not yet recruiting, Enrolling by invitation, and Active, not recruiting. The returned set contained 154 records, each with a unique NCT identifier. Records were deduplicated by NCT identifier before ranking.

To qualify, a record had to be interventional; be phase 2, phase 2/3, or phase 3; list at least one U.S. location; include a drug or biologic intervention; and report enrollment. Phase 1/2 records were excluded. This deliberately conservative subset accepted only records whose condition labels were “Idiopathic Pulmonary Fibrosis” or “Idiopathic Pulmonary Fibrosis (IPF),” with no other condition labels. The included studies’ summaries and eligibility criteria were also checked to confirm an IPF-only population. Records listing broader or mixed pulmonary-fibrosis populations were excluded rather than assigning their whole-study enrollment to IPF participants.

The condition was checked against GARD’s IPF disease entry, which identifies IPF as a rare disease. An orphan-drug designation was not used as a substitute for checking a trial’s disease population or eligibility.

Within this search universe, 20 records met the criteria. Ten are shown, ranked by enrollment descending, with NCT identifier ascending as the tie-breaker. Three entries report actual enrollment and seven report estimated enrollment. No missing enrollment values occurred among the 154 returned records; missing values, if present, would be excluded from ranking rather than treated as zero.

Ten selected eligible trials

The records below were retrieved on October 28, 2026. Trials are sorted by reported enrollment, largest first; the two records tied at 240 are ordered by NCT identifier. “Actual” and “estimated” reproduce the registry’s enrollment type.

The sponsor shown is the registry’s lead sponsor, not the submitting organization, investigator, or study contact. Intervention descriptions are shortened for readability; consult the linked record for the full protocol details.

Reading enrollment and status correctly

ClinicalTrials.gov enrollment is the reported total for the study. It is not the number enrolled at U.S. sites, the number currently being recruited, or the number assigned to a particular treatment arm. It also does not report whether an intervention works.

One entry needs particular care: NCT07520110 reports estimated total enrollment of 800, while its summary describes approximately 800 IPF participants screened and 400 high-risk participants randomized to metformin or placebo. Eligible participants without the proteomic risk signature receive remote follow-up assessments. The ranking preserves the reported total because the described population has IPF throughout; the 800 figure should not be described as the size of the randomized comparison.

“Ongoing” in this article includes trials that are not recruiting, as well as those that are recruiting or have not yet started recruitment. Registry status may lag behind operational changes. For example, NCT05321420 is listed as Active, not recruiting, with an estimated enrollment and a record update date of October 16, 2025; those are the values reported in the snapshot.

Several larger studies were excluded because their records included broader pulmonary-fibrosis populations without a separate IPF enrollment total. These include NCT07441408, NCT04905693, and NCT06238622. Assigning their entire study enrollment to IPF would overstate the population-specific count.

A larger reported enrollment does not establish study quality, suitability for any individual, effectiveness, or likelihood of success. Investigational therapies should not be interpreted as approved or effective on the basis of this ranking.

What this list says about rare disease research

Reported enrollment helps compare the scale of rare disease clinical trials within a consistently defined population, but whole-study totals can mislead when populations differ. Orphan drug clinical trials are not automatically interchangeable with studies that meet this article’s criteria: eligibility depends on the registry record’s phase, status, locations, intervention, and study population.

Frequently asked questions

Why call these selected trials rather than the definitive top ten?

The search and eligibility review covered the IPF condition query, not every rare disease and every relevant term in the registry. The available evidence supports a selected IPF ranking only.

Does “actual enrollment” mean trial results are available?

No. It identifies the enrollment type reported in the record. Enrollment alone does not provide outcome data or establish whether a treatment is effective.

Why include trials that are not recruiting?

The requested definition of ongoing includes Active, not recruiting and Not yet recruiting records, as well as recruiting and enrolling-by-invitation studies. Status is reproduced as reported and may not reflect the latest operational situation.

Does FDA orphan drug designation show that a trial is eligible or that a therapy is approved?

No. FDA describes orphan designation as a separate process from seeking product approval or licensing. Designation does not, by itself, establish that a particular trial meets the criteria used in this ranking. FDA’s designation overview

Explore clinical-trial data in QOPE

For a clinical-research landscape comparison, start with QOPE’s Clinical Trials dataset catalogue and review the available NCT identifier, study status, type, phase, enrollment, organization, and record-date fields. Use NCT identifiers to cross-check public study records before comparing enrollment or attributing sponsorship. QOPE’s organization field may use the lead-sponsor name with a submitting-organization fallback, so it should not always be treated as a confirmed lead sponsor.

Sources

• ClinicalTrials.gov — registry records linked individually in the ranking; retrieved October 28, 2026.
• Idiopathic Pulmonary Fibrosis — NIH Genetic and Rare Diseases Information Center — disease verification.
• Designating an Orphan Product: Drugs and Biological Products — FDA — distinction between orphan designation and approval.