Considerations driving the choice in clinical trial design of cell and gene therapy products: weighing convenience versus necessity

Because of small patient populations, lack of effective therapies, and complicated treatment protocols, advanced therapy medicinal products (ATMPs) for rare diseases are often licensed based on evidence generated outside of a “gold standard” double-blinded, randomized controlled trial (RCT). The lack of important bias-reducing features in non-RCTs can present uncertainties for regulators and health technology assessment bodies, making choice of trial design a critical decision for developers. This “Meeting of the Minds,” co-hosted by the Alliance for Regenerative Medicine, the International Society for Cell & Gene Therapy and ATMP Sweden in December 2024, set out to create a structured framework that provides clarity on when deviation from an RCT is necessary and should be acceptable, and on how alternative study designs such as a single-arm trial or unblinded RCT may be justified. Through multi-stakeholder engagement and discussions of case studies, a “trial-design decision tree” was generated that can help guide developers and healthcare decision-makers through a stepwise approach to contemplating deviation from an RCT. Although not exhaustive, three clinical scenarios surfaced where departure from a blinded RCT appears warranted: cases where the experimental treatment is expected to have high efficacy but the enrollable patient population is too small, cases where there is no effective standard of care and patients assigned to placebo would experience significant disease progression during the trial and cases where subjecting the control group to complex, burdensome and potentially risky protocols in the interest of blinding would impose unacceptable burden on patients.