CHARLES CITY — One of the nation’s leading drug molecule companies with a facility in Charles City is being bought by an international investment firm.

Cambrex Corporation announced Wednesday it’s signed an agreement worth two-point-four billion dollars with a Permira, a private equity firm with offices in London, Tokyo, Hong Kong and New York. Cambrex owns a 45-acre site in Charles City employing 400 people and completed a $24 million expansion in April.

The sale is expected to be completed in the fourth quarter of this year.