- Trinucleotide repeat variants in the promoter of the thiopurine S-methyltransferase gene of patients exhibiting ultra-high enzyme activity. Roberts, R.L., Gearry, R.B., Bland, M.V., Sies, C.W., George, P.M., Burt, M., Marinaki, A.M., Arenas, M., Barclay, M.L., Kennedy, M.A. Pharmacogenet. Genomics (2008)