After an eight-year odyssey, the first cytidine triphosphate synthase 1 (CTPS1) inhibitor has entered the clinic, with Step Pharma SAS announcing it has simultaneously begun studies in the U.S. and the U.K. The phase I/II trial is assessing Step’s lead program, STP-938, in relapsed/refractory B- and T-cell lymphomas, with the first U.S. site opening for enrollment this week.