German and Swiss drug makers Schering and Novartis are developing a new anti--cancer drug with annual sales potential of up to €2billion ($2.7 billion), Schering chief Hubertus Erlen said in a newspaper interview. "For us and for our cooperation partner Novartis, it could represent sales potential of €1 billion," Erlen told the daily Die Welt. The substance, PTK/ZK, cuts off blood flow to tumours, stopping their growth. It is in the final phase of clinical trials, he said. "If we can show that this technology is successful in intestinal cancer, there is the possibility that it could also be used to treat other types of cancer," Erlen added.