Best known as Viagra, the erectile dysfunction drug sildenafil started off as a treatment for reduced blood flow but soon saw its value spike after its other effects became clear. The blue pill could have more uses, according to research by scientists at the Weizmann Institute of Science in Tel Aviv. The team found indications that it curbs cancer metastasis via a “newly discovered biological mechanism” drawing upon the drug’s blood dilatation effects. Sildenafil curbs the capacity of cancer...