The goal of this observational study is to learn about infectious complications in patients affected by B-cell acute lymphoblastic leukemia treated with inotuzumab-ozogamicin (INO). The main question it aims to answer is:

• incidence of infectious complications (bacterial, fungal, viral) in patients receiving inotuzumab ozogamicin up to 60 days after the end of treatment

The present study is a multicenter, retrospective, observational clinical-epidemiological study on infectious complications (bacterial, fungal, viral) in patients receiving inotuzumab ozogamicin (INO). The study collects data from about 20 Hematologic Centers of the GIMEMA Group treating B-cell acute lymphoblastic leukemia (ALL) patients with inotuzuumab-ozogamicin (INO) over the last 5 years (2018-2023), according to the authorized indications and not included in interventional clinical trials (randomized or not randomized).

Inclusion Criteria:

• Adult patients (>18 years old)
• Patients with relapsed/refractory CD22 positive B-ALL treated with INO or with relapsed/refractory CD22 positive and Ph-positive B-ALL treated with INO after failing at least one TKI inhibitor
• Signed informed consent if applicable.

Exclusion Criteria:

• Patients treated with INO in interventional clinical trials.

Adult patients with relapsed/refractory CD22 positive acute lymphoblastic leukemia treated with INO or with relapsed/refractory CD22 positive and Ph-positive B-ALL treated with INO after failing at least one TKI inhibitor