Epizyme (EPZM) announced that it has earned a $6 million milestone payment from licensee GlaxoSmithKline (GSK). The milestone payment was triggered after GSK initiated a Phase 1 clinical trial evaluating cancer therapy candidate GSK3326595 (formerly EPZ015938). Under its collaboration and license agreement with Epizyme, GSK has exclusive global rights to methyltransferase inhibitors directed to three targets. GSK3326595 is the first one to enter the clinic.