Updated from 3:41 p.m. EDT

Shares of

Exelixis

(EXEL) - Get Report

were among the most actively traded health-related stocks Friday, after the company signed a collaboration agreement with

Genentech

( DNA) for the discovery and development of drugs that will target cancer, inflammatory diseases, and tissue growth and repair.

As part of the deal, Exelixis will receive an upfront payment from Genentech and receive research and development funding over three years, it said. For cancer therapeutics developed under the agreement, Exelixis will receive milestone and royalty payments. For the other areas, Exelixis has an option to share a portion of the costs and profits associated with the development, manufacturing and commercialization of those products. Shares of Exelixis traded up 4 cents to $7.15.

Universal Health Services

(UHS) - Get Report

rose 1.7% after the company expanded its buyback plan by 3.5 million shares. The company only had 84,000 shares remaining under previous buyback authorizations. The hospital company also said its board authorized it to purchase its convertible debentures due 2020. Shares traded up $1.02 to $60.25.

Shares of

Amylin Pharmaceuticals

( AMLN) traded actively after the company presented data from its phase II obesity study of pramlintide. The study of pramlintide, a synthetic analog of human Amylin -- a hormone known to play a role in the regulation of appetite and food intake -- showed statistically significant, progressive weight loss of 3.6% compared with patients taking a placebo, it said. What's more, there was no evidence of a plateau effect at 16 weeks. The weight loss, it said, was accompanied by a significant and progressive reduction in waist circumference.

Amylin recently started enrolling a 16-week phase II trial that will study about 400 obese, nondiabetic subjects. The placebo-controlled study will evaluate three doses ranging up to 360 micrograms with two- and three-times-a-day dosing regimens. Data from the study is expected to be available during the first half of 2006. Shares traded down 29 cents to $15.67.

Alexion Pharmaceuticals

(ALXN) - Get Report

rose 2.6% after the company posted third-quarter results and narrowed its full-year earnings outlook. The company reported a loss of $32.5 million, or $1.16 a share, on sales of $151,000. A year ago the company posted a loss of $15.2 million, or 69 cents a share, on sales of $168.000. Analysts were looking for a loss of $1.05 a share in the most recent period. Looking ahead, Alexion now expects to report a full-year loss of $106 million to $110 million. The company did not provide a per-share loss estimate. Previously, it forecast a loss of $105 million to $115 million. Analysts are expecting a loss of $3.59 a share. Shares traded up 58 cents to $23.18.

Other health care volume movers included

Elan

(ELN)

, up 18 cents to $7.03;

Pfizer

(PFE) - Get Report

, down 24 cents to $27.96;

WebMD

(HLTH)

, up 49 cents to $10.13;

Biogen Idec

(BIIB) - Get Report

, down $1.67 to $36.40;

Amgen

(AMGN) - Get Report

, down $1.39 to $61.49;

Johnson & Johnson

(JNJ) - Get Report

, down 56 cents to $66.44;

UnitedHealth Group

(UNH) - Get Report

, up 22 cents to $50.60;

Merck

(MRK) - Get Report

, down 14 cents to $32.09;

Boston Scientific

(BSX) - Get Report

, down 5 cents to $27.80;

Able Laboratories

( ABRX), down 31 cents to $4.42; and

Schering-Plough

( SGP), down 15 cents to $19.55.