Updated from 4:34 p.m. ESTWhile Gilead Sciences ( GILD) saw its fourth-quarter revenue jump, the company reported mixed sales results for some of its major drugs, sending its shares lower in after-hours trading. According to Gilead, fourth-quarter revenue rose 65% from a year ago, and product sales climbed for the ninth straight quarter thanks to its HIV drug Truvada and hepatitis B treatment Hepsera. Sales of Truvada, the company's biggest HIV drug, rose 18% from the third quarter to $191.1 million, but analysts were disappointed. Forecasters expected Truvada sales to reach $197 million. The drug, which launched in the U.S. in the third quarter of 2004 and in certain European countries in 2005, accounted for 50% of Gilead's total HIV product sales for the fourth quarter. As patients switched over to Truvada from Viread, sales of the older HIV drug fell 8% from the 2004 fourth quarter to $182.4 million. Sales of another HIV drug, Emtriva, slid 15% from a year ago to $11.2 million, but the decline wasn't as bad as the expected drop to $9.3 million. Sales of AmBisome, a treatment for severe fungal infections, and Hepsera were stronger than anticipated. AmBisome brought in $55.6 million in sales for the fourth quarter, up 1%, while revenue from Hepsera totaled $51.2 million, a 43% increase. Overall, product sales totaled $493.4 million. The company's HIV product line had sales of $384.8 million in the fourth quarter, a 47% increase from the same period in 2004, but slightly lower than the consensus projection of $389.8 million. All told, the Foster City, Calif., biopharmaceutical company posted revenue of $609.3 million for the quarter, up from $369.6 million in the same period a year ago. Gilead earned $281.6 million, or 59 cents a share, for the last three months of the fiscal year, more than double the $110.2 million and 24 cents a share last year. Excluding a tax benefit realized from the repatriation of foreign earnings, Gilead would have earned $256.5 million, or 54 cents a share, in the most recent quarter, the company said Monday.