UK-based GlaxoSmithKline said it has given up its fight to protect a key ingredient in its leading anti-diabetes medicine sold in China, the second setback in a month for a Western drug company. Glaxo said it would not counter-sue Chinese drugmakers that had challenged its patent for rosiglitazone, one of three patented ingredients in Avandia. Last month, the Chinese government voided Pfizer's claim on Viagra. Chinese drug companies asked the government to withdraw a patent for the Avandia ingredient in January. Glaxo filed a counter-suit in March asking the companies not to infringe upon its patent, but subsequently decided to drop the suit.