Updated from 2:53 p.m.

Shares of

Dendreon

(DNDN)

were among the worst-performing health and pharmaceutical stocks Friday, falling 9.4% after an analyst slapped a sell rating on the stock.

In lowering his rating to sell from buy, Brean Murray analyst Jonathan Aschoff said "it is not worth waiting for another positive catalyst to provide a better price at which to issue a rating downgrade that we concede is already long overdue." The firm said that it no longer believes Dendreon can manage a partnership deal for the commercialization of Provenge. It also questioned how the Food and Drug Administration would view the company's three-year survival data from trial 9901. Specifically, Aschoff said that if the data "are driven almost entirely by the healthier subgroup, then that would marginalize the relevance of Provenge to the sicker patients and undercut Dendreon's conclusion that the three-year survival data is truly relevant to the entire intent-to-treat population." As a result of the firm's concerns, Brean Murray put a $6 price target on Dendreon's shares. Previously, the firm had a $21 price target. Shares of Dendreon traded down $1.05 to $10.18.

OSI Pharmaceuticals

(OSIP)

and

Genentech

(DNA)

fell Friday after the FDA approved their non-small-cell lung cancer treatment. The companies fell over concerns that Tarceva could not be used with older chemotherapy treatments. Results from two earlier clinical trials showed no clinical benefit with concurrent adminstration of Tarceva with doublet platinum-based chemotherapy. As such, Tarceva is not recommended for use with those therapies. The companies said that Tarceva would be available within five shipping days. Shares of OSI traded down $6.09 to $58.16, while Genentech traded down 99 cents to $48.89.

Shares of

Mylan Labs

(MYL) - Get Report

rose 10% after the company's largest shareholder offered to buy it for $20 a share. In a filing with the

Securities and Exchange Commission

, Carl Icahn, who owns 9.8% of Mylan's stock, said that he and a group of investors feel there are better alternatives for Mylan than its planned acquisition of

King Pharmaceuticals

(KG)

. Shares of Mylan traded up $1.72 to $18.88. Shares of King traded down 5 cents to $11.15.

Other health care volume movers included

Pfizer

(PFE) - Get Report

, down 54 cents to $27.23;

Merck

(MRK) - Get Report

, down 24 cents to $27.12;

Astrazeneca

(AZN) - Get Report

, down 91 cents to $39.43;

Elan

(ELN)

, down $1.67 to $27.83; and

Amgen

(AMGN) - Get Report

, down 20 cents to $59.88.