This multi-centre phase II single arm trial was designed to investigate the activity and safety of 6-mercaptopurine (6MP) 55 mg/m2 per day, and methotrexate 15 mg/m2 per week in patients with advanced breast or ovarian cancer, ECOG PS 0–2, progressing after ≥ one prior regimen and known to bear a BRCA1/2 germ line mutation. This evidence concerns the gene BRCA1 and ovarian cancer.