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Context Post-HSCT relapse of B-cell ALL is associated with a dismal outcome. IO allows, in the setting of R/R B-ALL patients, high response rates, but with limited duration. Objective To report the outcome of 8 B-ALL adult patients, relapsed after allogeneic HSCT, treated with IO and DLI. Design Retrospective analysis (first patient treated in April 2015, last patient in October 2019). Setting Multicenter (Italian centers). Patients or other participants Five Ph-negative and 3 Ph-positive B-ALL adult patients, with BM disease (6 morphological relapse and 2 MRD-positivity) were treated; 2 patients had additionally extramedullary (EM) disease. Three patients were in salvage 1, 5 patients in salvage ≥ 2; 50% of the patients had previously received Blinatumomab. Median time from transplant to relapse and from relapse to IO was 11 (range 2-21) and 2.5 (range 0-65) months, respectively. Interventions Patients received a median of 3 (range 2-6) IO courses. Four patients received IO and DLI in an alternate schedule and 4 patients sequentially after IO; a median of 3 (range 2-4) DLI at escalating dose was administered (1st dose ranging from 1 × 104/kg CD3+ to 5 × 106/kg CD3+; following doses from 1 × 105 to 5 × 107/kg CD3+). Main outcome measures CR and MRD rate, EM response, DFS, OS, toxicity. MRD was evaluated with BCR-ABL fusion transcript or V(D)J IgH/TCR disease-specific rearrangement on BM. DFS and OS were calculated from start of IO. Toxicity was graded according to CTCAE version. 4.03. Results All patients achieved CR after 1st IO cycle. Six of 8 patients obtained MRD negativity after 2nd IO cycle (4 of 6 patients after 1st cycle). Both PET+ patients achieved PET-negativity. With a median follow-up of 23.5 (range 3-58) months, 6 of 8 (75%) patients are alive. Four of 8 (50%) patients relapsed, of which 2 with CNS localization. Median DFS is 12 months (range 3-58) and median OS is 23.5 (3-58) months. Four out of 8 patients experienced G4 thrombocytopenia. Two patients experienced grade 1 GvHD and no VOD were reported. Conclusions IO and DLI are a safe combination in the post-HSCT setting that may ameliorate the dismal prognosis of this patient subset.

Background: Adult B-ALL patients still have a dismal prognosis, due to a high incidence of relapse even after allogenic SCT. Safety and efficacy of Blinatumomab, an anti CD3-CD19 Bite antibody, has been demonstrated both in MRD positive patients and in relapsed/refractory (R/R) setting. Aim: To evaluate safety profile and efficacy of Blinatumomab, obtained through a compassionate use, in a cohort of 18 adult patients affected by MRD+ or R/R B-ALL treated at Bologna University. Design: From March 2015 to July 2016, 18 patients received Blinatumomab at the standard dosage (9 mcg/d x 7 days, 28 mcg/d x 21 days) in 28-days courses. All the patients were hospitalized to receive the first course of therapy. The following courses, based on the good safety profile of the compound, were administered in outpatient setting. Patients: 18 patients (M/F = 10/8; median age 43, range 18-73) have been treated. Philadelphia (Ph) chromosome was detected in 8/18 patients. 10 patients were MRD+ (5 Ph pos and 5 Ph neg); E2A-PBX1 and MLL-AF4 rearrangements were found in two patients. 8 patients had a R/R disease (3 Ph pos and 5 Ph neg). Median WBC count before starting therapy with Blinatumomab was 5400/mmc (range 500-76500). All the patients had previously received many lines of therapy (median 4, range 1-7). In 4 cases an alloTMO was already performed, and two patients had received two transplants. 12/18 patients were referred to us by other Italian Institutions. All the patients received at least one course of Blinatumomab. In one case three courses were administered; an elderly patient is actually receiving the fifth course. Globally, 32 courses of therapy have been administered (median 2, range 1-5). Bone marrow evaluations, including cytogenetics, molecular biology and immunophenotyping analysis were performed at the beginning of every course of therapy in order to assess patients' disease status. MRD evaluation was assessed through BCR-ABL fusion transcript quantitative analysis in Ph pos ALL patients and Ig rearrangment in Ph negative patients. Monitoring of adverse events was periodically performed. Results: 16/18 patients are evaluable for response, at least to one cycle (one patient died during the first course, one patient is still receiving the first course). 9/16 (56%) patients obtained a CR (7/9 MRD+ and 2/7 R/R). In 7/9 (78%) responders patients a molecular CR was reached, (in 6 patients after the first course, in one case after the second one). 5 responders proceeded to alloBMT and are actually alive in CR (median follow-up after transplant 240 days). In terms of toxicity, one patient developed a grade IV neurological event (mental confusion, tremor), which completely resolved after a transient drug withdrawal. Conclusions: Our results confirm the high rate of response and to Blinatumomab in a poor patients' population, and the good management profile of the compound. Acknowledgments: Work supported by ALN, AIL, AIRC, PRIN, Progetto Regione-Universita 2010-12 (L. Bolondi), FP7 NGS-PTL project. Disclosures Soverini: Ariad: Consultancy; Bristol-Myers Squibb: Consultancy; Novartis: Consultancy.