SAMHD1 Single Nucleotide Polymorphisms Impact Outcome in Children with Newly Diagnosed Acute Myeloid Leukemia.

Cytarabine arabinoside (Ara-C) has been the cornerstone of AML chemotherapy for decades. Following cellular uptake, it is phosphorylated into its active triphosphate form (Ara-CTP), which primarily exerts its cytotoxic effects by inhibiting DNA synthesis in proliferating cells. Interpatient variation in the enzymes involved in the Ara-C metabolic pathway have been shown to impact intracellular abundance of Ara-CTP and thus its therapeutic benefit. Recently, SAMHD1 (SAM and HD domain containing deoxynucleoside triphosphate triphosphohydrolase 1) has emerged to play a role in Ara-CTP inactivation, development of drug resistance and consequently, clinical response in AML. Despite this the impact of genetic variations in SAMHD1 on outcome in AML has not been investigated in depth. In this study, we evaluated 25 single nucleotide polymorphisms (SNPs) within SAMHD1 gene for association with clinical outcome in 400 newly diagnosed pediatric AML patients from two clinical trials- AML02 and AML08. Three SNPs, rs1291128, rs1291141, and rs7265241 located in the 3' region of SAMHD1 were significantly associated with at least one clinical outcome endpoint: minimal residual disease (MRD) after induction I, event free survival (EFS), or overall survival (OS) in the two cohorts. In an independent cohort of patients from COG-AAML1031 trial (n=854), rs7265241 A>G remained significantly associated with EFS and OS. In multivariable analysis, adjusting for other prognostic factors such as race, age, risk group, and white blood cell count, all the SNPs remained independent predictors of clinical outcome endpoints. These results highlight the relevance of the SAMHD1 pharmacogenomics in context of response to Ara-C in AML and warrants the need for further validation in expanded patient cohorts.