Across 94 European CTIS gene therapy phase 1 - 3 trials, 64 trials used at least one CRO-coded or outsourced clinical service provider, equal to 68.1%. PPD / Pharmaceutical Product Development and Parexel were the most active providers, each appearing in 11 of 94 trials. CRO use was highest in phase 3 trials, mid-sized multinational studies, and trials with 51–100 planned participants.
CRO support was present in 29 of 33 phase 3 trials, equal to 87.9%. Phase 1 and phase 2 trials showed lower but still substantial CRO use: 31 of 51 phase 1 trials (60.8%) and 38 of 63 phase 2 trials (60.3%).
For gene therapy, CRO demand rises sharply when trials move into confirmatory execution. Phase 3 trials combine broader country footprints, stricter operational controls, and heavier EU submission coordination, making outsourced clinical operations and CTIS execution support more common.
PPD / Pharmaceutical Product Development and Parexel led the market, each supporting 11 of 94 trials (11.7%). Fortrea and ICON followed with 10 trials each (10.6%), while Medpace appeared in 8 trials (8.5%).
The provider mix shows two demand layers: full-service CROs for multinational execution and specialist providers for data systems, laboratories, imaging, patient support, and EU/CTIS operational workflows.
The strongest CRO-use signal was not simply the largest trials. CRO support peaked at 51–100 planned participants (11/12 trials; 91.7%), 3–4 countries (17/19; 89.5%), and 5–9 sites (13/15; 86.7%).
Gene therapy sponsors appear most likely to outsource when a trial becomes too complex for a single-country academic or sponsor-led setup, but before it becomes a very large global program with more internal infrastructure.
Among therapeutic areas with at least 7 trials, CRO use was highest in musculoskeletal gene therapy (6/7; 85.7%), ophthalmology (14/17; 82.4%), and rare disease (32/42; 76.2%). Disease-level hotspots included neovascular age-related macular degeneration (4/4; 100%) and Duchenne muscular dystrophy (3/3; 100%).