OBJECTIVES: The lack of long-term effectiveness data for novel therapies and uncertainties around standardised treatment algorithms suggests that new advanced therapies for complex perianal fistulas (CPAF) could be suitable candidates for performance-based risk sharing agreements (PBRSAs). The aim of this work was to identify real-world evidence needs and solutions for addressing payer uncertainty within a heterogeneous standard of care, considering introduction of darvadstrocel - a new advanced therapy medicinal product (ATMP) for CPAF treatment. METHODS: Three case studies of recently reimbursed orphan treatments were used to analyse long-term data requirements and ATMP introduction: daratumumab (registry in multiple myeloma/ non-ATMP); genetically modified allogeneic T-cells (as an add-on to hematopoietic stem cell transplantation, ATMP) in Germany; and autologous CD34+ cells for severe combined immunodeficiency due adenosine deaminase deficiency (ATMP) in Italy were selected and analysed based on HTA outcomes and real-world evidence availability. Additionally, five semi-structured European payer interviews were conducted to complement case study findings. RESULTS: HTA outcomes for the two ATMP introductions required additional information on comparative long-term effectiveness. A longitudinal registry as employed for daratumumab allows for continued evaluation and identifies optimal clinical application strategies, potentially enhancing payer insight. Payer interviews suggested that PBRSAs linked to prospective data collection in the real-world setting could address HTA uncertainty when standard of care is unclear. However, care should be taken to ensure data collection frameworks are not too resource intensive, and enable further contextualisation against previous treatment outcomes. CONCLUSIONS: The implementation of an open-enrolment non-interventional patient registry, as for darvadstrocel, enhances achievability of introduction of this ATMP via PBRSA. Especially if an integrated solution can be provided with minimal additional human or financial resources from providers or payers. Prospective evidence generation through a registry will ease managed entry through PBRSA and may become a preferred market access approach for ATMPs.