Shares in Amgen Inc. surged $3.19 during the first week of the New Year, bolstered by a partnership the Thousand Oaks biotech firm formed with San Francisco-based Cytokinetics to aid the Bay Area company in its development of a new heart drug. The company’s stock gained nearly 5 percent for the week and closed Friday at $71.50 and continued to gain after the market closed.

Guess Inc. was close behind; riding strong December sales numbers that came ahead of the Los Angeles-based company’s fourth quarter earning, which will be announced Feb. 12. The apparel maker and retailer saw its shares gain $2.40 a share, despite a sharp drop of $1.60 on Friday.

Herbalife Ltd. wasn’t so lucky. The Los Angles-based supplement and health products maker saw its shares lose more than $10.42 after slashing its sales projection for 2007, closing Friday at $29.74, losing more than 25 percent for the week.

Arden Group Inc. also saw its shares lose $2.57 to close the first week of 2007 out at $118.53. However, the Compton-based supermarket operator’s stock was up more than 30 percent 2006.