PREVENTION, rather than cure could become the norm in the West if modern biotechnology has its way. Several big multinational drug firms such as Hoechst, Merck and Glaxo Wellcome are trying their best to manufacture drugs that keep cells from malfunctioning. This is done by blocking the signal that causes these cells to function errantly. The technology, called signal transcluction blocking, could prove invaluable for a host of ailments ranging from allergies, rheumatoid arthritis, osteoporosis to transplanted organ rejection. The biggest challenge is to design drugs that interfere with the process that makes proteins and hormones change shapes and bind, signalling a cell to act without blocking signals for needed activity by other cells.