UPDATE 2-Shire says key data on HAE drug bodes well for U.S. approval

* Co plans to submit U.S. marketing app by late 2017/early 2018

* Analysts have forecast potential peak sales of $2 billion

* U.S. shares rise 6 pct premarket (Adds details, updates shares)

May 18 (Reuters) - Shire Plc said successful late-stage data on its long-acting drug for hereditary angioedema would form the basis of a U.S. marketing application for the treatment.

U.S.-listed shares of company, which already sells a number of hereditary angioedema (HAE) treatments, were up about 6 percent at $193.15 before the bell on Thursday.

Shire said it planned to submit a U.S. marketing application for the drug by late 2017 or early 2018. Analysts have forecast peak sales of up to $2 billion for the treatment.

Patients with HAE suffer from recurrent episodes of severe swelling and Shire's drug, lanadelumab, is being developed to prevent these attacks.

Shire said lanadelumab reduced the monthly attack rate by 87 percent versus a placebo in a late-stage study over 26 weeks in patients 12 years and older with the rare genetic disease.

HAE affects about one in 50,000 people, and the areas most commonly affected are the extremities, gastrointestinal tract, and upper airways, according to the National Institutes of Health.

In the United States, existing treatments are either injections for acute attacks or short-acting intravenous infusions administered twice a week, Shire said.

"If approved, lanadelumab may offer patients a long-acting treatment option that significantly reduces HAE attacks when administered subcutaneously as infrequently as every four weeks," the study's lead investigator Aleena Banerji said in statement on Thursday.

Lanadelumab's improved dosing profile would likely prompt wider prophylaxis adoption and its efficacy could lower the need for acute rescue dosing, Cowen & Co analysts said in a note in April.

Shire's existing HAE drugs include Kalbitor, Cinryze and Firazyr. Other FDA-approved treatments include CSL Behring's Berinert and Valeant Pharmaceuticals International Inc's Ruconest.

The approval of lanadelumab would make Shire less vulnerable to Firazyrs loss of exclusivity - expected by 2018 - and to competition for Cinryze, Morningstar analysts have said. (Reporting by Natalie Grover in Bengaluru; Editing by Martina D'Couto and Saumyadeb Chakrabarty)