Updated from 5:03 p.m. EDT

Amylin Pharmaceuticals ( AMLN), the developer of two diabetes drugs, issued third-quarter results Wednesday that fell below analysts' expectations on both the top and bottom lines.

The financial report, issued after markets had closed, led to a sharp selloff in after-hours trading. Amylin's shares lost $3.99, or 10.5%, to $34. In regular trading, the stock gained 44 cents.

The San Diego-based biotechnology company lost $69.5 million, or 65 cents a share, on revenue of $25.9 million for what was its first full quarter of commercial operations. Analysts polled by Thomson First Call had predicted a loss of 57 cents a share on revenue of $30.7 million.

For the same period last year, Amylin lost $34.1 million, or 36 cents a share, on revenue of $13.4 million.

Amylin makes and sells Symlin, an injectable drug for helping reduce blood sugar and which is used in conjunction with insulin. Symlin was approved by the Food and Drug Administration in March, after more than four years of review during which the agency twice asked Amylin for additional clinical data.

The more important product is Byetta, which helps control blood sugar. The FDA approved the drug in late April. Amylin has enlisted Eli Lilly ( LLY) to help it market Byetta, which must be injected twice a day. Amylin isolated the drug from the saliva of the Gila monster.

Amylin also is working with Lilly and Alkermes ( ALKS) to create a version of Byetta that can be injected once a week.

Although Byetta's clinical results have been favorable, some analysts have said sales might fall below more bullish Wall Street estimates because the injectable Byetta must compete against similar medications that are taken orally.

Ginger L. Graham, the president and CEO, told analysts in a telephone conference call that demand for Byetta isn't completely reflected in reported revenue because Amylin provides free samples to doctors, along with certain discounts for patients. These practices are standard to the pharmaceutical industry as companies promote new drugs to doctors and patients.

Free samples aren't included in prescription trends tracked by medical data firms. Graham said different firms can present conflicting information, and she told analysts to be careful about relying on one service for predicting future trends.

Graham didn't provide details on Amylin's sampling program, except to say that it has been expanding since September. Prescription data shows October demand for Byetta has been growing, but she didn't provide specifics. There has been an "enthusiastic response" by doctors, nurses and patients, Graham said.

Selling, general and administrative expenses more than tripled to $52.1 million vs. the same period last year, reflecting Amylin's increased production of Byetta and the hiring and training of staff to market and support the drug.

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