The Nasdaq Biotechnology IndexI:NBI was up 1.3% but slightly lagging the broader market Thursday, with the Nasdaq up 1.7% and the Dow up 1.3%.
Among those gaining in afternoon trading:
Amylin shares were rising 5% to $12.99 on news that billionaire investor Carl Icahn was building his position in the company as he tries to replace some board members.
Dendreon , which announced it would give a company update via Webcast at the upcoming BIO CEO conferences, was lately up 4.8% to $3.68.
Medivation was up 1.7% to $19.56.
Elan was down 0.5% to $8.01.
Genzyme was up 1.2% to $72.01.
Biogen Idec was up 0.6% to $53.04.
Among those losing:
Genentech shares were down 0.7% to $81.90.
Amgen was down 0.1% to $56.71.
Gilead Sciences was down 0.4% to $51.78.