Charles River Laboratories International, Inc. has extended its longstanding integrated drug discovery alliance with Genentech, a member of the Roche Group.   Under the alliance, Charles River provides early discovery services, including medicinal chemistry, in vitro and in vivo biology, structural biology, and computer-aided drug design, to help identify promising candidates for preclinical development.   The companies have been engaged in an ongoing program since 2005, with the latest exte...