UPDATE 2-FDA refuses to review Alkermes' depression treatment, seeks more trials

trials@ (Adds details on the company's development pipeline, updates shares)

April 2 (Reuters) - Alkermes Plc has been told to conduct more clinical trials of its experimental depression treatment after the U.S. Food and Drug Administration rejected its initial application for approval, citing a lack of evidence of its effectiveness.

The FDA's decision knocked nearly $2 billion off the company's value and spells extra cost for the Dublin-based drugmaker, which has two major drugs already in the market but for whom the ALKS 5461 depression treatment was seen as a driver of future revenue.

Two of the three late stage trials conducted on the drug two years ago failed to meet efficacy goals before a third set in October 2016 showed significantly reduced symptoms of depression compared to a placebo.

The company strongly disagreed with the FDA's decision and said it would ask for a meeting with the regulator. It was holding a conference call with analysts and investors at 8.30 a.m. ET.

"We strongly believe that the clinical development program, including data from more than 1,500 patients with MDD, provides substantial evidence of ALKS 5461's consistent antidepressant activity and a favorable benefit-risk profile," Alkermes' Chief Executive Officer Richard Pops said.

The drugmaker is working to develop several treatments for other disorders of the central nervous system, but will have to resubmit its marketing application before any future launch of the depression drug after the FDA's "Refusal to File" letter.

Shares of the company fell 22 percent $45.43 in trading before the bell.

The FDA has requested a bioavailability study to show bridging data between the drug and the reference drug, buprenorphine.

ALKS 5461, a once-daily pill combining samidorphan and buprenorphine, is designed to rebalance brain function that becomes dysregulated in the state of depression, and was developed to treat major depressive disorder in patients with an inadequate response to standard antidepressant therapies.

An estimated 16.2 million people in the United States suffered from major depressive disorder in 2016, according to the company, and a majority of the patients do not adequately respond to initial anti-depressant therapy.

The company's other two drugs in the market treat schizophrenia and alcohol dependence. Its development pipeline includes drugs for treatment of multiple sclerosis and schizophrenia. (Reporting by Manas Mishra in Bengaluru; Editing by Shailesh Kuber)