Avapritinib is effective for treatment of minimal residual disease in acute myeloid leukemia with t (8;21) and kit mutation failing to immunotherapy after allogeneic hematopoietic stem cell transplantation

In patients with t(8;21) acute myeloid leukemia (AML) with recurrent measurable residual disease (MRD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT), pre-emptive interferon-α therapy and donor lymphocyte infusion are noneffective in 30%-50% of patients. Avapritinib is a novel tyrosine kinase inhibitor targeting KIT mutations. We retrospectively report about 20 patients with t(8;21) AML and KIT mutations treated with avapritinib after allo-HSCT with MRD and most failing to respond to immunotherapy. Reduction of RUNX1-RUNX1T1 after 1 month of treatment was ≥1 log in 12 patients (60%), which became negative in 4 patients (20%). In 13 patients who received avapritinib for ≥3 months, the reduction was ≥1 log in all patients, which became negative in 7 patients (53.8%). The median follow-up time was 5.5 (2.0-10.0) months from avapritinib initiation to the last follow-up. Three patients underwent hematologic relapse and survived. Among all 20 patients, RUNX1-RUNX1T1 transcripts turned negative in 9 patients (45%). The efficacy did not differ significantly between D816 and non-D816 KIT mutation groups. The main adverse effect was hematological toxicity, which could generally be tolerated. In summary, avapritinib was effective for MRD treatment in patients with t(8;21) AML with KIT mutations failing to respond to immunotherapy after allo-HSCT.