This work is based on the discovery of diurnal variations impacting cancer therapy. Especially, use of chronomodulated treatment with 5-fluorouracil (5-FU) has gained significance. Studies indicate high inter-individual variability in diurnal variations in dihydropyrimidine dehydrogenase (DPD) activity – a key enzyme for 5-FU metabolism. However, the influence of individual chronotypes on chronomodulated therapy was unclear but is needed to optimize precision dosing of chronomodulated 5‑FU. Lead by the Thorsten Lehr's PKPD group at the University of Saarland, this collaborative paper is taking a treasure trove of patient 5-FU PK data amalgamated with DPD enzyme activity data from health people to establish a novel PKPD model of 5-FU that captures the extent of diurnal variations in DPD activity and can help investigate individualized chronomodulated 5-FU therapy through testing alternative personalized dosing strategies. Read the paper here.