Updates with closing share prices in the fifth paragraph.

July 30 Bloomberg -- Charles River Laboratories International Inc. withdrew a $1.6 billion bid for WuXi PharmaTech Cayman Inc., citing investor opposition to what would have been the largest foreign takeover of a China company.

Charles River said today it will pay WuXi a $30 million break fee after the companies agreed to end the $21.25-a-share cash-and-stock offer made in April. Wilmington, Massachusetts- based Charles River, which provides research and testing services to drugmakers, also said its board approved a $500 million share buyback.

Jana Partners LLC, Charles Riverâ??s largest stakeholder, urged investors to vote against the deal, citing â??highly speculativeâ?? benefits and an â??unreasonable price,â?? in a statement issued hours before the announcement. The takeover would have given Charles River facilities in Shanghai, Suzhou and Tianjin in China, where cheaper labor and laboratory costs are luring the worldâ??s biggest drugmakers including Novartis AG.