* FDA clears Fasrena for patients aged 12 years and older
* AstraZeneca prices maintenance dose below rivals
* AstraZeneca product will vie with GSK's Nucala (Adds details on pricing, competition, CEO comment)
LONDON, Nov 15 (Reuters) - AstraZeneca has achieved another milestone in rebuilding its drug portfolio with U.S. approval of a drug for severe asthma as the company battles to put patent losses on older medicines behind it.
The U.S. Food and Drug Administration's (FDA) decision to endorse benralizumab, which will be marketed under the name Fasenra, follows a positive recommendation for the product in Europe on Friday.
Shares in AstraZeneca were 1 percent higher on Wednesday following the overnight news.
Fasenra will compete with GlaxoSmithKline's Nucala and Teva's Cinqair - two other injectable antibody drugs for severe asthma - but AstraZeneca believes its product's potency and convenient dosing could give it an edge.
The Anglo-Swedish company is also being competitive on cost, setting a long-term price below that of rivals at $28,000, or $33,000 in a maintenance year, depending on whether patients receive six or seven doses.
Treatment in the first year will cost $38,000, as more doses are needed, which AstraZeneca said was in line with competing biologic drugs in severe asthma.
While most investor focus is on AstraZeneca's cancer research, the company also has a long history in respiratory therapy that it plans to build on with Fasenra and another earlier-stage medicine called tezepelumab that is developing with Amgen.
Modern biotech asthma drugs are offering new hope for severe asthma sufferers who continue to have breathing problems despite using modern inhalers. In the case of Fasrena, the number of severe asthma attacks was roughly halved in clinical tests.
Fasrena is designed for patients with a particular kind of asthma driven by a type of white blood cells called eosinophils.
AstraZeneca had previously said it hoped to win U.S. approval for the new drug before the end of the year. The FDA approval, announced late on Tuesday, clears Fasenra as an add-on treatment for severe asthma patients aged 12 years and older.
"This is the first approval from our respiratory biologics portfolio and the latest in a series of significant milestones for our company as we deliver on our pipeline-driven transformation," said AstraZeneca Chief Executive Pascal Soriot.
Last week, while presenting quarterly results, Soriot said the drugmaker was moving into a commercial execution mode, following the success of a number of new medicines in clinical development.
In cancer, it has seen good results in 2017 with two new pills already on the market - Lynparza and Tagrisso - while its blood cancer drug Calquence won U.S. approval last month. Imfinzi, its closely watched immunotherapy medicine, failed in initial tests in one lung cancer setting but proved successful in another. (Editing by Louise Heavens)