Background: InO is a CD22-directed antibody-drug conjugate indicated for treatment of relapsed/refractory (R/R) ALL. InO has been associated with hepatotoxicity and hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS), particularly post-HSCT. Registry data (Center for International Blood and Marrow Transplant Research [CIBMTR]) was analyzed to assess toxicity in pts with ALL who received InO prior to HSCT. Methods: CIBMTR patient data are being collected for a 5-year period after US approval of InO (Aug 2017 – Aug 2022). Data from US pts age ≥18 y treated with InO who proceeded to allogeneic HSCT were included. Using interim data at 3 y, we evaluated post-HSCT outcomes, including clinical status, overall survival, transplant-related (non-relapse) mortality (NRM), relapse, death after relapse (time from HSCT to death after the first 28 d from any cause with prior relapse/progression post-HSCT), and investigator-defined adverse events, including hepatic VOD/SOS. All statistical analyses are descriptive. Results: Data accrued from 18 Aug 2017 to 17 Aug 2020 for 131 adult pts (median age 40 y) who proceeded to first allogeneic HSCT: 31% in first complete remission (CR1), 46% in CR2, 13% in ≥CR3, 5% in 1st relapse, 2% in ≥3rd relapse, and 3% in primary induction failure. A majority (70%) had transplants from peripheral blood stem cells, and 47% involved an HLA-identical sibling or other related donor. Nearly half received myeloablative conditioning regimens. Before HSCT, 36% of pts received 1 cycle of InO, 46% had 2 cycles, and 17% had ≥3 cycles. Half (48%) received InO as a single agent. Median time from last dose of InO to HSCT was 2.0 mo (range: 0.4–26.2). At time of data-lock (11 Nov 2020), post-transplant data were available for 131 pts. Outcomes for these pts are shown in the Table. Among a subgroup of adults with active R/R ALL (n = 91) at time of HSCT (median of 4 lines prior therapy), VOD/SOS incidence within 100 d of HSCT was 18%. Conclusions: Incidence of VOD/SOS after first HSCT in InO-treated pts with R/R ALL in this study was similar to the 18–19% reported in pooled analyses of 2 clinical trials among InO-treated pts with R/R ALL (Marks et al, Biol Blood Marrow Transplant 2019) and in the INOVATE study (Kantarjian et al, Lancet Haematol 2017). The NRM at 1 y of 21% (23% R/R ALL) is lower than the NRM at 1 y of 38% reported in the pooled analyses of R/R ALL InO recipients.

*Continued CR is defined as a patient who underwent HSCT during CR, and the CR is sustained post-HSCT.