Harmonised but not more attractive? The EU Clinical Trials Regulation and the site allocation of multinational drug trials

Abstract Europe’s share of industry-sponsored clinical trials has fallen for a decade. The Commission’s 2025 Biotech Act proposal seeks to reverse this by amending the Clinical Trials Regulation (CTR), which in 2022–2023 replaced national authorisation with a single coordinated procedure. I evaluate the CTR’s effect on where trials are run, using 12,955 multinational industry trials started in 2013–2025, linked to national decision dates from the EU Clinical Trials Register and the Clinical Trials Information System, and compare the EU/EEA with other world regions within the same trial. The CTR nearly eliminated cross-country differences in authorisation times, reducing the dispersion of national decision times by about 85 per cent around a common median of roughly four months. Yet after the CTR became mandatory, the probability that a multinational trial included any EU/EEA site fell relative to other regions, by 3.9–11.5 percentage points from a base of 78 per cent depending on how the pre-existing EU trend is modelled. A triple difference with region × year fixed effects, which absorbs EU-wide shocks, shows a further 14.3-point decline for phase 1 relative to phase 3 trials, with flat pre-trends. Trials remaining in Europe used more member states, but selection may account for this increase. Member states whose authorisation had been slowest gained no share. Harmonisation thus did not make Europe more attractive for trials. The results are consistent with a higher fixed cost of entering Europe, a cost that further harmonisation alone does not address.