June 1 (Reuters) - Alkermes Plc said on Tuesday the U.S. Food and Drug Administration (FDA) had approved its treatment, Lybalvi, for schizophrenia and bipolar I disorder.

The company said it expects to commercially launch the drug in the fourth quarter.

The FDA in November had declined to approve the drug, citing concerns related to a tablet coating process at its manufacturing site.

Lybalvi is a once-daily, oral antipsychotic drug composed of olanzapine, an established antipsychotic agent, and samidorphan, a new chemical entity, the company said.

Schizophrenia is a severe mental disorder and affects 20 million people worldwide, according to the World Health Organization.

The company also has FDA-approved antipsychotic and alcohol-dependence treatments in the market. (Reporting by Dania Nadeem in Bengaluru; Editing by Aditya Soni and Vinay Dwivedi)