NEW YORK (AP) -- Shares of biotechnology companies opened higher Monday as the sector heads into another week of earnings reports.

The American Stock Exchange's biotechnology index rose 5.42 points to 756.93. The index tracks several bellwether stocks. The Nasdaq Stock Market's biotechnology index, which covers a broader range of small- and midcap stocks, rose 4.35 points, to 809.98.

Here's how several key biotechnology stocks performed Monday:

Gilead Sciences Inc., up 69 cents to $52.09.

Amgen Inc., up 28 cents to $42.53.

Biogen Idec Inc., up 36 cents to $65.50.

Genentech Inc., up 57 cents to $72.54.