A drug used in the treatment of cancer may help inhibit the growth of cysts in patients with a form of inherited kidney disease, researchers have found. The findings showed that drug — called bosutinib — approved for the treatment of certain cases of chronic myeloid leukemia slowed cyst growth in patients with autosomal dominant polycystic kidney disease (ADPKD). ADPKD is an inherited disorder that affects up to one in 1,000 people and is characterised by cysts in the kidney and other organs.“The reduction in growth of cysts through treatment with bosutinib was confirmed, although gastrointestinal side effects (primarily diarrhoea), which were partly dose-dependent, may represent a substantial drawback for the further development of the drug for patients with ADPKD,” said Vladimir Tesar, from the Charles University and General University Hospital, in the Czech Republic. As patients’ kidney volume increases due to cyst growth, they gradually lose their kidney function and often develop kidney failure. The inherited mutations that cause ADPKD affect a protein involved in various signalling pathways that often involve enzymes called tyrosine kinases. Therefore, researchers tested the potential of an investigational drug called bosutinib that inhibits a particular tyrosine kinase called Src/Bcr-Abl. The study, appearing in the Journal of the American Society of Nephrology (JASN), included patients with ADPKD who were randomized 1:1:1 to bosutinib 200 mg/day, bosutinib 400 mg/day, or placebo. Of 172 patients enrolled, 169 received at least one treatment. The higher dose of bosutinib was not well tolerated. The annual rate of kidney enlargement was reduced by 66 per cent for patients receiving bosutinib 200 mg/day vs. those receiving placebo (1.63 per cent vs. 4.74 per cent, respectively) and by 82 per cent for all patients receiving bosutinib vs. those receiving placebo (0.84 per cent vs. 4.74 per cent, respectively).