Response to Trametinib of Two Pediatric Myeloid Malignancies Cases Harboring RAS Mutation and Monosomy 7

Myelodysplastic syndrome (MDS) and juvenile myelomonocytic leukemia (JMML) are usually resistant to conven-tional chemotherapies. Allogenic hematopoietic stem cell transplantation (allo-HSCT) is the only curative treatment. Aberrant activation of the RAS-derived mitogen-activated protein kinase (RAS/MAPK) signaling pathway is a major contributing factor in many malignancies. Single-agent trametinib has been reported to produce positive effects against RAS -mutated myeloid malignancies in adult patients. However, the higher response rate among patients with RAS mutations did not translate into a sur-vival benefit for patients with RAS mutations or those who responded to the trametinib treatment [1]. In the present study, we report two patients with pediatric MDS and JMML, separately, who were treated with trametinib (MEK 1/2 inhibitor) before and after HSCT, respectively.