Health care stocks traded mixed Tuesday as the broader market dipped and rose in wide swings. Amgen ( AMGN) rose on the release of study data that showed denosumab, its experimental drug designed to grow bone, reduced the risk of new spine and hip fractures by 68% and 40%, respectively, compared to placebo, in post-menopausal women. Amgen shares gained $3.70, or 6%, to $65.89. Amgen is a component of both the Amex biotechnology index, which climbed 2.3% to 810.10, and the Amex pharmaceutical index, which edged down 0.1% to 297.62. ImClone ( IMCL) shares lost ground on comments from Bristol-Myers Squibb's ( BMY) CFO that the drugmaker could walk away from its $60-a-share bid for the biotech. Jean-Marc Huet, according to a Reuters report, told investors at a Merrill Lynch health care conference in London Tuesday, "You should never fall in love with an asset. We understand the business very well and there are situations in which we are willing to walk away." Last week, ImClone revealed it had received a competing $70-a-share bid from an unnamed suitor. ImClone traded down 5.2% to $60.39, as Bristol shares edged 0.4% lower to $21.46. Shares of Targacept ( TRGT) and AstraZeneca ( AZN) traded lower after the two reported post-close Monday inconclusive results for a phase IIb clinical trial of AZD3480 to treat mild to moderate Alzheimer's disease. AstraZeneca said it will decide on potential further development of AZD3480 in December. Targacept sank $2.58, or 30.5%, to $5.88, while AstraZeneca lost 59 cents, or 1.3%, to $44.35.