Abstract: Background：Children with Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ALL) have a poor prognosis after relapse, and treatment is challenging. Olverembatinib has shown good efficacy in adult patients with relapsed Ph+ALL, but its efficacy and safety in children are not well defined. Objective：To evaluate the efficacy and safety of olverembatinib in children with Ph+ALL. Design： Case series report. Methods：A retrospective analysis was conducted on children with Ph+ALL admitted to the department of pediatrics of Peking University People's Hospital from January 2022 to July 2024, who were treated with olverembatinib. The effects, side effects, and outcomes of the treatment were analyzed. Main outcome measures：Complete remission (CR), minimal residual disease (MRD) negativity, major molecular response (MMR), and complete molecular response (CMR). Results：A total of eight pediatric patients with relapsed Ph+ALL were included in the analysis, comprising six males and two females, with a median age of 9 years. Among them, three had hematologic relapse, while five had molecular relapse before receiving olverembatinib. All patients achieved CR after one treatment cycle of olverembatinib, either as monotherapy or in combination with chemotherapy. Among the three patients with hematologic relapse, the MRD negativity rate was 100%, and the MMR rate was 66%. Among the five patients with molecular relapse, the MRD negativity rate, MMR rate, and CMR rate were all 100%.The median follow-up duration was 13 months, during which all eight patients maintained CR. The MRD negativity and MMR rates remained 100%, while the CMR rate was 75%. All patients survived throughout the follow up period. Notably, one patient experienced a relapse of central nervous system leukemia (CNSL) but achieved sustained cerebrospinal fluid MRD negativity after receiving olverembatinib monotherapy combined with a single intrathecal chemotherapy injection.The adverse effects observed during treatment were mainly attributed to the combined use of chemotherapy drugs. Olverembatinib monotherapy did not cause significant discomfort in most patients; however, one patient discontinued olverembatinib due to drug-related adverse reactions. Conclusion：For the children with relapse of Ph+ALL, olverembatinib monotherapy or in combination with chemotherapy shows good efficacy and safety.

Key words: Olverembatinib, Relapsed, Philadelphia chromosome positive, Acute lymphoblastic leukemia, Children