Challenges and Criteria for Single-Arm Trials Leading to an Added Benefit in German Health Technology Assessments

Background Randomized controlled trials are the standard for health technology assessment, but when they are infeasible or unethical, single-arm trials (SATs) are submitted. Objectives This study examined when SATs were accepted for added benefit by the Institute for Quality and Efficiency in Health Care (IQWiG) and/or the Federal Joint Committee (G-BA) in Germany. Methods We identified health technology assessments via the AMNOG-Monitor database through December 2024, with additional details from G-BA documents. We compared the SATs and other evidence for added benefit decisions (granted/not granted), stratified by orphan drug status, special marketing authorization, approved indication (chronic hepatitis C/others), and population (adults/children). Added benefit claims by manufacturers, IQWiG recommendations, and G-BA appraisals were compared. Results Among 1738 G-BA decisions, 85.8% (1491/1738) of the subpopulations were fully assessed by IQWiG, with 13.5% (202/1491) based on SATs. Among the 247 orphan drugs assessed by the G-BA, 37.7% (93/247) were SAT-based. Overall, SAT-based assessments demonstrated an added benefit in 12.2% (36/295) of cases. This included 13.4% (27/202) of full assessments and 9.7% (9/93) of orphan drug assessments. IQWiG accepted only 18.5% (5/27) of the SATs endorsed by the G-BA. Statistical tests revealed significant differences between manufacturers' claims, IQWiG recommendations, and G-BA appraisals. SATs were most frequently accepted for chronic hepatitis C treatments (mostly with non-standard marketing authorization) and paediatric indications. The G-BA cited reasons such as dramatic effects, rare diseases, a lack of alternatives, or fewer side effects, although justifications were often unclear. Conclusion Acceptance rates for SATs remain low, and criteria for added benefit are not always explicitly defined. To enable benefit assessments when randomised controlled trials are infeasible or unethical, clear and binding criteria developed in collaboration with the G-BA are essential.