Charles River Laboratories International Inc. has signed a definitive agreement to acquire Vigene Biosciences Inc., a premier, U.S.-based gene therapy contract development and manufacturing organization (CDMO) providing viral vector-based gene delivery solutions.   The purchase price is expected to be $292.5 million in cash, subject to customary closing adjustments. In addition to the initial purchase price, the transaction includes contingent additional payments of up to $57.5 million based on ...