Biotech stocks overall ticked up slightly Thursday, but one notable exception was Cell Genesys ( CEGE), which sank 75% to 17 cents on word of a serious clinical setback. The decline in Cell Genesys came after the company said it terminated a second study on its prostate cancer vaccine GVAX, and said it would cut 75% of its workforce. Still, Cell Genesys did little to hurt the Nasdaq Biotechnology index, of which it's a component. The index added 3.3%, outperforming the broader market. The Amex Biotechnology index added 2.1%. Components and biotech bellwethers Amgen ( AMGN) and Celgene ( CELG) added 1.6% and 1.5%, respectively. Celgene ( CELG) and Acceleron Pharma said they have initiated a midstage trial on an investigational bone loss therapy in patients with multiple myeloma. It will trigger a $5 million milestone payment from Celgene to Acceleron. Following the close, earnings are expected from Gilead ( GILD). Analysts surveyed by Thomson Reuters are looking for a profit of 49 cents a share on $1.32 billion in revenue. Gilead shares were up 5.9% ahead of quarterly results. Elsewhere, Brean Murray and Merriman Curhan Ford initiated coverage on multiple small- to mid-cap health-care stocks. Brean Murray began coverage on Mentor ( MNT) with a hold rating. Shares were off by 1.5% at $15.82. The firm also picked up coverage on Xtent ( XTNT), NuVasive ( NUVA) and Hansen Medical ( HNSN) with buy ratings. Xtent shares were up 9.8%, and NuVasive gave up 2.2%. Hansen Medical gained 6.6%. Meanwhile, Merriman Curhan Ford started Dendreon ( DNDN) with a sell rating. The stock was down 1.7%, at $80.06. The firm began coverage on Ariad Pharma ( ARIA) with a neutral rating. Shares rose 7.3% to $1.61.