Tazemetostat, the histone methyltransferase (HMT) inhibitor of enhancer of zeste homologue 2 (EZH2) [1], is currently in a single agent open-label, phase 1/2 trial in patients with B-cell lymphomas and in combination with prednisolone in diffuse large B-cell lymphoma (DLBCL) (NCT01897571). Here, PRDM9 is linked to diffuse large B-cell lymphoma.