Introduction：B cell acute lymphoblastic leukemia(B ALL) is highly prevalent in children and has a good prognosis with a 5-year survival rate of 80-90%. However, the prognosis of elderly ALL is extremely poor, mainly due to its poor prognosis and poor tolerance to treatment. Therefore, for elderly unfit ALL patients, a safe and effective treatment is urgently needed. In recent years, immune therapies have developed rapidly, and these treatment have high efficacy and safety for relapsed and refractory(r/r) B ALL or MRD+ALL. Our aims to observe safety and efficacy of CD22 antibody inotuzumab ozogamicin conjugated with calicheamicin toxin (Ino.) treatment for elderly unfit r/r B ALL
Methods：A total of 9 elderly unfit r/r B ALL pts who received Ino. treatment from August, 2023 to July , 2024 were included. All patients expressed CD22 antige before treatment. 1 pts received three dose Ino.,other pts received Ino.1mg/W 1～2 times.
Results：9pts:5 females and 4 males with a median age of 59 years (56～72 years old),1 pts CML AP，6 pts Ph+ALL，2pts Ph-ALL.All patients were treated with chemotherapy and all Ph+ALL patients were treated with TKI. Among them, 2 patients had relapse after allogeneic hematopoietic stem cell transplantation(allo-HSCT): 1 patient had relapse after HSCT and CD19 CAR-T treatment,1 patient had relapse after HSCT and CD19 antibody blinatumomab(BITE) with COVID-19 infection;7 pts did not undergo HSCT：1 pt experienced recurrent/ineffective treatment after BITE, CD19 CAR-T, CD22 CAR-T,1 pt experienced recurrence after CD19 CAR-T twice and CD22 CAR-T twice、1 pt who was CML-AP experienced recurrence after BITE、CD19 CAR-T with renal dysfunction，1 pt relapsed after BITE accompanied by pulmonary mucormycosis infection，3 pts did not receive any immunotherapybefore：1 pt has been cured of lung cancer.Before INO.,1 pts MRD+,8 pts have hematological recurrence.All patients have safely completed the INO. treatment and after treatment:5 pts(100%) with hematological recurrence achieved CR (3 pts FG-，1 pts FCM-MRD-、FG-MRD+，1pts morphological CR with FCM/FG+），1pts MRD+;In addition, there are 3 pts who cannot evaluate the efficacy of INO: 2 pts achieved the opportunity to collect lymphocytes for CAR-T therapy, and 1 pt died due to subsequent sepsis.
Conclusions：
For elderly unfit r/r B ALL pts even including those after treatment with both CD19 and CD22 CAR-T cells or HSCT, ino. treatment is safe and effective and so ino. can be the first treatment recommendation.
No relevant conflicts of interest to declare.
