We chose to explore the combination in the TP53 mutated OVCAR3 and the TP53 and BRCA1 mutated MDA-MB-436 cell lines. In the OVCAR3 xenograft model, the combination of SRA737 and adavosertib caused tumour regressions and tumour volumes were significantly smaller than controls, p<0001. The combination caused a lesser but significant degree of reduction in the tumour volume in the MDA-MB-436 xenograft model compared to control p=0.003. There was less than a 20% loss of mouse body weight in treatment arms of both xenograft models.