Across 94 unique European gene therapy trial records, the dataset contains 755 country-level site allocations and 3,623 country-allocated participants. Site concentration is led by Assistance Publique Hôpitaux de Paris with 15 trial-site participations, while Spain leads country allocation with 789 participants and 158 site allocations. Phase III represents only 28 of 94 trials, but accounts for 2,083 of 3,623 participants and 372 of 755 site allocations, showing that late-stage gene therapy activity is more geographically scaled than early-phase activity.
The top 10 site-country records account for 97 of 724 listed trial-site participations, or 13.4%. Assistance Publique Hôpitaux de Paris ranks first with 15 participations, followed by Hospital Universitari Vall d’Hebron with 11 and three sites tied at 10 participations each.
The leading sites are large academic or hospital-network centers rather than single-specialty clinics. This matters operationally because gene therapy trials often require cross-functional capacity across hematology, neurology, ophthalmology, oncology, imaging, apheresis, intensive care, and long-term follow-up.
Spain, France, Italy, and Germany together account for 2,242 of 3,623 participant allocations, or 61.9%, and 517 of 755 site allocations, or 68.5%. Spain leads participant allocation with 789 participants, while France has the highest country-trial frequency with 43 country-level trial records.
Gene therapy operations are concentrated in the major Western European trial markets. Spain and France combine high participant allocation with broad site networks, making them the strongest first-wave countries for European feasibility and site activation.
Phase III accounts for 28 of 94 trials, or 29.8%, but carries 372 of 755 site allocations, or 49.3%, and 2,083 of 3,623 participant allocations, or 57.5%. Phase I/II is the largest trial-count category at 46 of 94 trials, or 48.9%, but represents only 642 participant allocations, or 17.7%.
| Phase group | Trials | Site share | Participant share |
|---|---|---|---|
| Phase III | 28 / 94 | 49.3% | 57.5% |
| Phase I/II | 46 / 94 | 24.2% | 17.7% |
| Phase II | 12 / 94 | 17.5% | 16.5% |
| Other mixed phase | 8 / 94 | 9.0% | 8.3% |
The pipeline is trial-count heavy in early development, but operational burden is driven by Phase III. For sponsors and CROs, late-stage gene therapy feasibility should prioritize countries with proven site density and participant allocation rather than only early-phase center experience.
Rare disease appears in 42 of 94 trials, or 44.7%, making it the most frequent therapeutic-area tag. However, site allocation is led by ophthalmology with 228 of 898 area-attributed site allocations, or 25.4%, and oncology with 220 of 898, or 24.5%. Oncology also leads participant allocation with 1,366 of 4,226 area-attributed participants, or 32.3%.
Rare disease defines much of the gene therapy pipeline by trial count, but ophthalmology and oncology create the broadest site networks. This suggests that operational infrastructure is more developed where gene therapy programs have moved into larger, later-stage or multi-country development.
The top six disease clusters account for 485 of 755 site allocations, or 64.2%, and 2,348 of 3,623 participant allocations, or 64.8%. Neovascular age-related macular degeneration is the largest site cluster with 199 site allocations across 5 trials and 900 participant allocations.
| Disease cluster | Trials | Sites | Participants |
|---|---|---|---|
| Neovascular age-related macular degeneration | 5 | 199 | 900 |
| Bladder / urothelial cancer | 4 | 108 | 523 |
| Heart failure / cardiomyopathy | 2 | 57 | 249 |
| Melanoma | 3 | 48 | 311 |
| Hemophilia | 5 | 41 | 80 |
| Lymphoma | 2 | 32 | 285 |
The largest gene therapy site networks are not only rare pediatric disorders. Ophthalmology and oncology indications create substantially broader site footprints, while hemophilia shows a smaller but specialized network consistent with the need for concentrated hematology expertise.
Paediatric trials represent 44 of 94 records, or 46.8%, and orphan-designated drug trials represent 45 of 94 records, or 47.9%. Exactly 47 of 94 records, or 50.0%, involve gene therapy in combination with another modality such as cell therapy, small molecule, monoclonal antibody, peptide/protein/enzyme, or diagnostic agent.
European gene therapy development remains highly specialized: nearly half of records involve paediatric or orphan-drug contexts, and half combine gene therapy with another intervention type. Site selection therefore depends on both clinical specialty and operational readiness for complex advanced-therapy workflows.
Site allocation refers to the country-level number of participating sites recorded for a trial. Site participation refers to a unique listed trial-country-site record. Country-allocated participants refers to the participant allocation recorded at country level. CTIS refers to the Clinical Trials Information System. AMD refers to age-related macular degeneration.