UPDATE 2-Shire 2007 earnings top forecast, upbeat on Vyvanse

(Adds analyst, company comments, detail, background, shares)

By Mark Potter

LONDON, Feb 21 (Reuters) - Britain's Shire Plc (SHP.L) beat forecasts with a 38 percent rise in 2007 earnings on Thursday and mounted a vigorous defence of its biggest new drug hope, Vyvanse for attention deficit hyperactivity disorder (ADHD).

Britain's third-biggest drugmaker, whose shares have fallen about a third since September on concerns about Vyvanse's growth since its launch in July, said it expected the drug to achieve $350 million to $400 million of sales this year.

This compares with analysts' current -- albeit reduced -- forecast of $354 million, according to a poll by the company, and also assumes that U.S. regulators approve by the middle of this year that the drug can be marketed to adults.

Chief Executive Matthew Emmens said he had a "high level of confidence" that Vyvanse will be approved to treat adults, the fastest growing part of the ADHD market.

"There has been a lot of noise about this (Vyvanse's launch)," he told reporters on a conference call. "This has been a successful launch and this product will continue to grow."

At 1330 GMT, Shire's shares were up 1.9 percent at 970 pence, valuing the firm at 5.4 billion pounds ($10.6 billion).

BEATING FORECASTS

Shire said it made earnings per American Depositary Share before one off items of $2.95 last year, beating analysts' average forecast of $2.77 in a company poll.

Revenues rose 36 percent to $2.44 billion, boosted by a 19 percent rise in sales of Adderall XR, Shire's current top-selling ADHD treatment, to $1.03 billion.

Key to Shire's future is switching patients onto Vyvanse before Adderall XR faces cheap, generic competition, potentially from April 2009.

Shire has always argued that Vyvanse is a new chemical entity, aimed at taking sales from competitors as well as Adderall XR, and its launch should not be compared with other, more direct drug switches.

"We continue to believe that concerns over Vyvanse are overdone," Morgan Stanley analysts wrote in a research note, keeping an "overweight" rating on Shire's shares.

Vyvanse generated $76.5 million of sales in 2007 and by Feb. 15 had achieved a 6.3 percent share of the U.S. ADHD market based on daily prescriptions.