UPDATE 3-Dendreon loss widens on Provenge launch costs

* Q3 shr loss 47 cents vs Street view loss 44 cents

* Provenge sales $20.2 million

* Shares down slightly after hours (Adds analyst, company comment, updates shares)

NEW YORK, Nov 3 (Reuters) - Dendreon Corp DNDN.O on Wednesday reported a wider third quarter loss on costs associated with the launch of its new Provenge vaccine for advanced prostate cancer, but the company provided an encouraging forecast for future sales.

In its first full quarter on the market, Provenge had sales of $20.2 million, shy of Wall Street estimates of $23.8 million.

The small biotechnology company said sales of Provenge, which hit the U.S. market in May, rose each month of the quarter, reaching $7.8 million in September.

For the first month of the current quarter Provenge had sales of $9.5 million, but Dendreon said it expects sales to dip in November and December due to holidays and some planned plant maintenance.

The company said it expects full-year revenue of $46 million to $47 million. For 2011 Dendreon forecast revenue of $350 million to $400 million, with about half of that expected to be generated in the fourth quarter as its manufacturing capacity increases.

“People should not be focused on what the first full quarter of (Provenge) sales are, but rather on what their guidance is for next year and I think that is very good news,” said Reni Benjamin, an analyst for Rodman & Renshaw.

Based on the forecast for 2011 fourth quarter sales, Benjamin said, “even if you keep that flat without growing that means that 2012 revenue should be at least $800 million, so you are reaching blockbuster status very quickly.”

Analysts expect the company to show its first quarterly profit in the fourth quarter of 2011.

The company posted a net loss of $79.3 million, or 56 cents per share, compared with a loss of $45.6 million, or 40 cents per share, a year ago.

Excluding a litigation charge, Dendreon lost 47 cents a share for the quarter. Analysts on average expected a loss of 44 cents, according to Thomson Reuters I/B/E/S.

The company reported selling, general and administrative expenses rose to $74.1 million in the third quarter from $9.3 million in the year ago period.

Revenue rose to $20.2 million from $25,000 in the year ago period.

Provenge, upon gaining U.S. approval in April, became the first therapeutic vaccine to actually treat cancer.

Unlike traditional vaccines that prevent a disease, Provenge, given via three infusions at a cost of $31,000 each, treats prostate cancer by stimulating the body’s own immune system to attack malignant cells. In clinical trials it has shown an ability to extend survival of advanced prostate cancer patients by more than four months.

But Dendreon shares, which soared to above $57 immediately after the approval, have been under pressure since over concerns about reimbursement and the company’s ability to provide an adequate supply of the drug.

Dendreon said more than 1,000 prescriptions have been written for Provenge since its approval, but that not all of those can be filled due to severe supply constraints.

“A thousand scripts is a nice increase from 500 (disclosed in the previous quarter) and it’s definitely going in the right direction,” said Mark Monane, an analyst with Needham & Co.

The company can currently supply only about $9 million to $10 million worth of Provenge per month. Dendreon said there are long waiting lists for the vaccine in many parts of the country, but noted that due to the nature of the disease some patients are unable to wait for Provenge.

The company said it was on track to make Provenge more broadly available in 2011 with the expansion and licensure of its New Jersey facility in early 2011 and the anticipated approval of plants in Georgia and California in mid-2011.

“The company gave guidance for next year for a robust increase in sales and seems to say that the timing of the manufacturing will meet that,” Monane said.

Dendreon said it plans to increase sales and marketing activities, including adding to its sales force, to keep Provenge demand strong through next year.

Dendreon shares fell to $38.50 in volatile after-hours trading from their Nasdaq close at $38.59. (Reporting by Bill Berkrot; Editing by Bernard Orr and Carol Bishopric)