Drugs company CeNeS Pharmaceuticals, which is listed on AIM, advanced by 1p to 8.87p on news that Anglo-American giant GlaxoSmithKline, 12p firmer at 1292p, has bought 13.3m shares, a 5% stake. City speculators have been left wondering if this could signal a commercial tie- up between the two companies, or even the possibility of GSK making a full bid.