The ALLELE trial

The ALLELE trial is investigating tabelecleucel to treat relapsed/refractory EBV-associated PTLD disease (R/R EBV+ PTLD) arising after a solid organ transplant (SOT) or a hematopoietic stem cell transplant (HSCT). In this video, Prof Daan Dierickx, hematologist at the University Hospitals Leuven, discusses the updated results of this trial presented during EBMT 2025.¹

In ALLELE, 75 patients (49 SOT,26 HSCT) were treated with tabelecleucel at 2x 10⁶ cells/kg on days 1, 8 and 15 in 35-day cycles. The median age of patients in the study was 44 years and about a quarter had an ECOG performance status of ≥2. Respectively 50% and 43.8% of patients were classified as having an intermediate or high-risk PTLD-adapted prognostic index. Patients received a median of 1 prior treatment line, with the most frequent prior treatments consisting of rituximab monotherapy (86.7%), chemotherapy- regimens (46.7%) and rituximab + chemotherapy (37.3%).

The overall ORR was reported at 50.7%, with comparable rates in patients undergoing a SOT or a HSCT. A complete response per IORA was seen in 28.0% of patients, with a partial response in additional 22.7%. Responses were durable, with a median duration of response of 23.0 months. The median overall survival (OS) reached 18.4 months, with a 1-year OS rate of 55.7% (57.1% in the SOT cohort and 52.4% among HSCT recipients). Among, responders to tabelecleucel, the 1-year OS rate reached 78.7% as compared to 28.2% in non-responders.

As such, these updated results from the ALLELE study confirm the efficacy and safety of tabelecleucel in R/R EBV+ PTLD patients. The median OS of 18.4 months is impressive knowing that the median OS of patients in the absence of treatment is only 0.7 to 4.1 months.