Gilead Sciences

(GILD) - Get Report

on Tuesday issued first-quarter results that handily beat Wall Street's predictions for earnings and sales.

The Foster City, Calif., biotech company reported earnings per share of 59 cents, excluding special items, on sales of $693 million. Analysts polled by Thomson First Call were expecting a profit of 53 cents and revenue of $621 million.

Under generally accepted accounting principles, which include stock-option expenses, Gilead earned $262.7 million, or 55 cents a share. For the same period last year, the company earned $157.1 million, or 34 cents a share, on revenue of $430.4 million.

Gilead was paced by growing sales of its HIV/AIDS drug franchise, which accounts for much of the company's revenue. The drugs Truvada, Viread and Emtriva combined for $450.7 million in sales during the first quarter, up 50% from the $301.5 million for the same period last year. Most of the sales came from Truvada and Viread.

Royalty revenue climbed to $133.5 million from $103.3 million. The antiviral drug Tamiflu, which Gilead licenses to Switzerland's

Roche

, produced first-quarter royalties of $115.3 million vs. $11.9 million in the same quarter of 2005.

Separately, Gilead, which has a market capitalization of $28.6 billion, said it would buy back $500 million worth of stock. To pay for the repurchase, Gilead will issue a total of $1.1 billion in convertible senior notes, in two deals, to institutional buyers. When the convertible deals close, Gilead will repurchase its stock.

Other proceeds will be used in transactions to offset the dilution of Gilead's common stock when the notes are converted. Any additional proceeds will be used for general corporate purposes.

The financial results were issued after the markets had closed. In regular trading, Gilead closed at $61.84, up 65 cents. After hours, the stock added another 61 cents.