Kaplan-Meier probability of survival after HLA 10/10-matched and HLA 9/10-matched unrelated donor HCT according to the number of favorable SNPs. A total of 4205 HLA 10/10 allele-matched⁴⁰  and 2628 HLA 9/10 single locus–mismatched⁴¹  unrelated donor-patient pairs were examined for SNP associations with survival: 10/10-matched and favorable rs887464 (SNP defined in reference 40) (solid red curve; n = 126); 9/10-matched and 0–1 unfavorable SNP (SNPs defined in reference 41) (solid blue curve; n = 73); 10/10-matched and neutral rs887464 (solid black curve; n = 3521); 9/10-matched and more than 1 unfavorable SNP (hatched blue curve; n = 1849); and 10/10-matched and unfavorable rs887464 (hatched red curve; n = 92). Overall survival after 10/10-matched unrelated donor HCT with favorable SNP is similar to that after 9/10-matched unrelated HCT with 0–1 unfavorable SNP. The negative effect of cumulative unfavorable SNPs is additive to HLA mismatch–associated risks.^40,41