High <scp>TPMT</scp> enzyme activity does not explain drug resistance due to preferential 6‐methylmercaptopurine production in patients on thiopurine treatment

Abstract

In this patient population with measured 6-MMP/6-TGN ratios, 19% of patients were preferential 6-MMP producers. The results show that high TPMT enzyme activity is not the major reason for preferential 6-MMP production in most patients with a high metabolite ratio. This suggests that there are one or more important alternative mechanisms for preferentially producing 6-MMP.