Shares of biotechnology company Gilead Sciences Inc. (NASDAQ: GILD) have been plunging this morning, despite the firm posting better-than-expected first quarter earnings per share. Hurting the stock this morning is the company's full-year sales guidance, which was unchanged.

Gilead Sciences reported late yesterday that its profit during the first-quarter jumped 22% to $496.1 million, or 51 cents per share, boosted by strong HIV treatments Atripla and Truvada sales. These numbers are up from $407.4 million, or 43 cents per share reported in the same period a year ago. Analysts' forecast was for lower earnings of 47 cents per share in the quarter.

The company's quarterly revenue also surged by a respectable 22% to $1.26 billion. For this period, the company benefited from strong gains from combination HIV treatment Atripla which came with sales of $342.2 million, a 70 percent rise. HIV drugs sales also saw a growth of 37% to $964.7 million. Analysts, on average, expected Gilead Sciences's sales to be $1.22 billion, according to Reuters Estimates.


Despite posting surprising earnings numbers, Gilead Sciences's shares have been plunging in today's trading on traders' disappointment that the company did not lift its full-year sales outlook. Gilead confirmed it still expects 2008 sales of $4.7 billion to $4.8 billion, anticipating lower orders during the second quarter. Analysts, on average, were waiting for a higher revenue of $5.08 billion.

The gloomy outlook from Gilead made Wall Street push the stock down over 4% in morning trading. Along with the company, the biotechnology group is set for a decline and it looks like nothing could encourage investors for the moment at least.

Eliza Popescu is a financial writer for the online investment advisory service Investor's Observer.