US groups Alkermes and Cephalon have been given the go-ahead to market Vivitrol, an injection against alcoholism, by the Food and Drug Administration, triggering a $110 million milestone payment to Alkermes.

Final clearance of the drug, which follows a conditional approval issued late last year by the agency, means that Vivitrol (naltrexone for extended-release injectable suspension) is now the first and only once-monthly injectable medication for alcohol dependence on the US market, and the groups expect it to be available by the end of June.

Vivitrol’s once-monthly administration offers an important advantage over its tablet predecessor – currently sold by generic drugmaker Barr Pharmaceuticals as ReVia - which must be swallowed every day. Consequently, analysts are expecting Vivitrol to rake in peak sales of over $500 million.

“The approval of Vivitrol, our first internally developed product, marks a significant milestone for Alkermes and demonstrates the potential of our proprietary extended-release technology to offer patients an entirely new way to get the medication they need,” commented Richard Pops, chief executive of Alkermes.

Under the terms of a joint commercialization partnership entered into in June last year, Cephalon holds primary responsibility for the marketing and sales of Vivitrol while Alkermes is responsible for its manufacturing.