Abstract
Chronic myeloid leukemia (CML) is classified into three subtypes based on the BCR breakpoint, the rarest of which is micro BCR::ABL1 (also known as e19a2 BCR::ABL1), which encodes a P230 fusion protein. CML patients with the e19a2 transcript are known to have a poor prognosis. Although second-generation tyrosine kinase inhibitors (TKIs) may be effective for this subtype, asciminib, a novel BCR::ABL1 inhibitor that specifically targets the ABL1 myristoyl pocket, has only been shown to be effective in patients with the major BCR::ABL1 transcript, with limited data on the micro BCR::ABL1 subtype. Here, we report a case of a CML patient with the e19a2 transcript who was intolerant to four TKIs but achieved complete cytogenetic response with asciminib. Our case suggests that asciminib, in addition to showing promising outcomes in CML patients with the major BCR::ABL1 transcript, is an effective treatment option for CML patients with the e19a2 micro BCR::ABL1 transcript.