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FDA’s 2026 draft guidance quietly rewrites the rules for how Bayesian methods can drive—not just decorate—primary efficacy decisions in drug and biologic trials, but sponsors still face major friction around priors, simulation burden, and documentation expectations (Ji, 2026; U.S. Food and Drug Administration, 2026a; Applied Clinical Trials, 2026).

The FDA released final guidance on real-world data in July 2024. The EMA expanded DARWIN EU to 30 partners covering 180 million patients across 16 European Countries (EMA, 2025). Japan's PMDA now accepts Real-World Evidence (RWE) for external control arms in orphan drugs, with multiple recent approvals using registry- or database-based external controls where randomized trials were not feasible (Asano et al., 2025). Taken together, these moves suggest that a regulatory inflection point for RWE has likely already occurred, even if operational practice is still catching up (FDA, 2025; Castor EDC, 2025).