UPDATE 1-Alkermes shares slip as J&J terminates 4-wk risperidone

(Adds analyst comments, updates share movement)

Aug 27 (Reuters) - Alkermes Inc (ALKS.O) shares slipped as much as 13 percent a day after it said units of Johnson & Johnson (JNJ.N) have decided not to pursue further development of a four-week long-acting version of antipsychotic drug risperidone.

Alkermes collects revenue for manufacturing a version of the injectable drug, known commercially as Risperdal Consta, which lasts for two weeks.

Jefferies & Co analyst David Windley said J&J's decision was likely influenced by the recent approval of Invega Sustenna and revenue losses to generics.

On July 31, U.S. health regulators approved J&J's once-monthly, long-acting, injectable atypical antipsychotic Invega Sustenna for treatment of schizophrenia in adults.

"Sustenna's approval achieves the once-monthly dosing, at least well enough in light of J&J's budget pressures in the pharma business," Windley said in a research note.

He lowered rating on Alkermes stock to "hold" from "buy" and cut his price target on the stock to $11.50 from $14.00.

J.P. Morgan Securities analyst Cory Kasimov said, "In our view, the fact that this decision was prompted by a portfolio review (rather than data) calls into question J&J's commitment to Consta."

Kasimov cut his price target on Alkermes to $14 from $16.

On Wednesday, Alkermes said the two-week version of Risperdal Consta continues to be marketed in more than 60 countries as the only long-acting atypical antipsychotic therapy available for both the treatment of schizophrenia and bipolar I disorder.

"Consta remains in J&J's long-term plans, but this decision will only fan the flames of the long-standing overhang stemming from the fact that Alkermes' partner is also committed to another similar product in the same space," said Robert W. Baird analyst Thomas Russo.

He maintained a "neutral" rating on Alkermes' stock.

Shares of the company dropped about 10 percent to $9.45 in morning trading, and were one of the top percentage losers on Nasdaq. They fell to a low of $8.98 earlier in the session.

(Reporting by Shailesh Kuber in Bangalore; Editing by Aradhana Aravindan)