Shares of

OSI Pharmaceuticals

(OSIP)

slipped Monday after the biotechnology company announced that its loss for the fiscal year ended Sept. 30 was greater than a year ago.

The results were affected in part by higher expenses incurred by OSI as it built up its sales staff to begin marketing Tarceva, a drug for treating advanced non-small cell lung cancer. The Food and Drug Administration approved Tarceva on Nov. 19, and OSI began selling the drug with its partner

Genentech

(DNA)

on Nov. 22.

OSI lost $260.4 million, or $6.50 a share, on revenue of $42.8 million for the fiscal year ended Sept. 30. The company did not provide separate fourth-quarter data.

For the same period last year, OSI reported a loss of $181.4 million, or $4.87 a share, on revenue of $32.4 million. Both fiscal years' calculations are on a GAAP basis.

Excluding charges and adjustments for the just-completed fiscal year, OSI lost $181.5 million, or $4.53 a share, on revenue of $42.8 million. OSI said it believes non-GAAP figures "are more reflective" of the company's core operating expenses and are "useful in analyzing operating performance and trends."

OSI said it has completed the expansion of its sales force for Tarceva to approximately 50 representatives and managers, who account for about one-fourth of the total Tarceva sales force activities. Tarceva is a tablet that is taken daily, and the drug is prescribed for patients with advanced lung cancer who have failed at least one regimen of chemotherapy.

The company's stock was down 79 cents, or 1.6%, to $49.70, after falling as low as $48.48.