Researchers from the MRC Laboratory of Medical Sciences, the University of Oxford, and University College London identified a previously underappreciated function for Wee1 that may help explain severe toxicities seen with Wee1 inhibitors in clinical trials. The study combined mathematical modeling with experiments and was published in Nature. The work suggests Wee1 acts earlier in the cell cycle than previously assumed, implying that on-target biology may contribute to toxicity patterns that derail studies. By clarifying the timing of Wee1’s role relative to DNA damage checkpoints—particularly in p53-altered cancers—the authors argue the field can refine patient selection and develop safer, more targeted therapies. For the clinic, the findings provide a mechanistic route for rethinking dosing windows and identifying which tumors are most likely to benefit from Wee1 blockade without unacceptable harm.