Glaxosmithkline plc (GSK) pledged $2.1 billion up front and as much as $1.2 billion in development milestone payments to take over privately held Affinivax Inc. and bring aboard the phase II-stage, next-generation, 24-valent pneumococcal vaccine candidate, AFX-3772. London-based GSK is buying all outstanding shares of Affinivax, of Cambridge, Mass., for $2.1 billion upon closing the deal in the third quarter of this year, and two potential milestone payments of $600 million to be paid if certain pediatric development goals are reached.