As part of the National Institute for Health and Care Excellence's (NICE's) Single Technology Appraisal (STA) process, Novartis submitted evidence on the clinical effectiveness and cost-effectiveness of tisagenlecleucel for treating paediatric and young adult patients (under the age of 25 years) with relapsed or refractory (r/r) B-cell acute lymphoblastic leukaemia (ALL). This article presents a summary of the Evidence Review Group's (ERG's) independent review of the evidence submission, the committee's deliberations, and the subsequent development of NICE guidance for the use of tisagenlecleucel on the National Health Service (NHS) in England. Tisagenlecleucel is a chimeric antigen receptor-modified T-cell (CAR-T) product, the first of this emerging therapeutic class to be considered by NICE in this indication. The company's evidence submission was based upon three single-arm, phase II studies: ELIANA, ENSIGN, and B2101J. These trials demonstrated a beneficial effect of tisagenlecleucel, with significant extensions in event-free survival (EFS) and overall survival (OS) compared to historical control datasets on blinatumomab and salvage chemotherapy. Adverse events were common; 77% of patients suffered from cytokine release syndrome (CRS), 56% of whom required intensive care unit-level care. The ERG did not consider clofarabine monotherapy an appropriate proxy for salvage chemotherapy. The company presented a hybrid cost-effectiveness model, combining a decision tree and three-state partitioned survival model structure. The majority of quality-adjusted life-years (QALYs) gained were generated through additional life-years in the extrapolated 'long-term survival' phase of the model, where patients were assumed to be 'cured'. The ERG considered the results to be subject to substantial uncertainty, due in part to immature trial data, unresolved long-term treatment effects, and a lack of appropriate comparator data. The ERG implemented a number of changes to the company's model in an alternative base case, producing deterministic incremental cost-effectiveness ratios (ICERs) of £45,397 per QALY gained versus salvage chemotherapy, and £27,732 versus blinatumomab. The probabilistic model produced ICERs of £48,265 per QALY gained versus salvage chemotherapy, and £29,501 versus blinatumomab. The committee considered the ERG's analysis to be most closely aligned with their preferred assumptions, and did not consider tisagenlecleucel to meet both of the end-of-life (EoL) criteria. In recognition of the innovative nature of tisagenlecleucel, and the present immaturity of ongoing clinical trials, the committee considered further data collection would be valuable in resolving uncertainties around OS, the technology's novel mechanism of action, and the management of CRS and B-cell aplasia. The committee therefore recommended tisagenlecleucel for use in the Cancer Drugs Fund (CDF) until the conclusion of the ELIANA study (June 2023). This appraisal highlighted the difficulty of interpreting EoL criteria in the context of curative therapies and the valuation of cure versus extension of life. Further clarification of NICE's position in these situations may be necessary to ensure consistency and equity in their decision-making.